2951
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Abstract
The lessons that the physician William Withering learned from his studies of digitalis are still relevant today. This paper highlights four of these lessons and updates them using the tools of clinical pharmacology and pharmacoepidemiology. First, Withering learned that failure to prepare digitalis from the foxglove in a standard manner resulted in a product with unpredictable clinical effects. Preparation of medicines from plants since then has not followed similar good practice and medicines have often not been granted marketing authorisation because of variability in their quality. Second, differences in the response to digitalis were noted by Withering, but he had little idea of their basis. Clinical pharmacology has shown that for drugs such as digitalis differences are caused by variability both in receptor sensitivity and in drug disposition. Third, the dose-response characteristics of digitalis were well known to Withering. Modern techniques of measuring response, such as the use of biomarkers, have made such studies easier, although clinical observations remain the gold standard. Fourth, Withering documented many of the adverse effects of digitalis. The use of various modern databases has facilitated the analysis of clinical toxicology and thus of risk-benefit profiles.
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2952
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Abstract
The increasing frequency at which poorly soluble new chemical entities are being discovered raises concerns in the pharmaceutical industry about drugability associated with erratic dissolution and low bioavailability of these hydrophobic compounds. Nanonization provides a plausible pharmaceutical basis for enhancing oral bioavailability and therapeutic effectiveness of these compounds by increasing their surface area. This paper surveys methods available to pharmaceutical manufacturing nanoparticles, including wet chemical processes, media milling, high pressure homogenization, gas-phase synthesis, and form-in-place processes, and elaborates physicochemical rational and gastrointestinal physiological basis upon which nano-drugs can be readily absorbed. Relevant examples are illustrated to show that nano-drugs permeate Caco-2 cell monolayer fast and are well absorbed into animal systemic circulation with high T(max) and AUC, resulting in oral bioavailability higher than their counterpart micro-drugs. The size-dependent permeability and bioavailability should be given particular consideration in the development of potent and selective drug candidates with poor aqueous solubility.
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Affiliation(s)
- Lee Jia
- Developmental Therapeutics Program, National Cancer Institute, National Institutes of Health, Rockville, MD 20852, USA
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2953
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Abstract
In support of a new clinical trial designed to compare the effects of crushed fresh garlic and two types of garlic supplement tablets (enteric-coated dried fresh garlic and dried aged garlic extract) on serum lipids, the three garlic products have been characterized for (a) composition (14 sulfur and 2 non-sulfur compounds), (b) stability of suspected active compounds, and (c) availability of allyl thiosulfinates (mainly allicin) under both simulated gastrointestinal (tablet dissolution) conditions and in vivo. The allyl thiosulfinates of blended fresh garlic were stable for at least 2 years when stored at -80 degrees C. The dissolution release of thiosulfinates from the enteric-coated garlic tablets was found to be >95%. The bioavailability of allyl thiosulfinates from these tablets, measured as breath allyl methyl sulfide, was found to be complete and equivalent to that of crushed fresh garlic. S-Allylcysteine was stable for 12 months at ambient temperature. The stability of the suspected active compounds under the conditions of the study and the bioavailability of allyl thiosulfinates from the dried garlic supplement have validated the use of these preparations for comparison in a clinical trial.
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Affiliation(s)
- Larry D Lawson
- Plant Bioactives Research Institute, Inc., Orem, Utah 84058, USA.
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2954
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Chillrud SN, Grass D, Ross JM, Coulibaly D, Slavkovich V, Epstein D, Sax SN, Pederson D, Johnson D, Spengler JD, Kinney PL, Simpson HJ, Brandt-Rauf P. Steel dust in the New York City subway system as a source of manganese, chromium, and iron exposures for transit workers. J Urban Health 2005; 82:33-42. [PMID: 15738337 PMCID: PMC3142770 DOI: 10.1093/jurban/jti006] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The United States Clean Air Act Amendments of 1990 reflected increasing concern about potential effects of low-level airborne metal exposure on a wide array of illnesses. Here we summarize results demonstrating that the New York City (NYC) subway system provides an important microenvironment for metal exposures for NYC commuters and subway workers and also describe an ongoing pilot study of NYC transit workers' exposure to steel dust. Results from the TEACH (Toxic Exposure Assessment, a Columbia and Harvard) study in 1999 of 41 high-school students strongly suggest that elevated levels of iron, manganese, and chromium in personal air samples were due to exposure to steel dust in the NYC subway. Airborne concentrations of these three metals associated with fine particulate matter were observed to be more than 100 times greater in the subway environment than in home indoor or outdoor settings in NYC. While there are currently no known health effects at the airborne levels observed in the subway system, the primary aim of the ongoing pilot study is to ascertain whether the levels of these metals in the subway air affect concentrations of these metals or related metabolites in the blood or urine of exposed transit workers, who due to their job activities could plausibly have appreciably higher exposures than typical commuters. The study design involves recruitment of 40 transit workers representing a large range in expected exposures to steel dust, the collection of personal air samples of fine particulate matter, and the collection of blood and urine samples from each monitored transit worker.
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Affiliation(s)
- Steven N Chillrud
- Lamont-Doherty Earth Observatory of Columbia University, 61 Rt 9W, Palisades, NY 10964, USA.
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2955
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Abstract
AIMS Rectal administration of methadone may be an alternative to intravenous and oral dosing in cancer pain, but the bioavailability of the rectal route is not known. The aim of this study was to compare the absolute rectal bioavailability of methadone with its oral bioavailability in healthy humans. METHODS Seven healthy subjects (six males, one female, aged 20-39 years) received 10 mg d(5)-methadone-HCl rectally (5 ml in 20% glycofurol) together with either d(0)-methadone intravenously (5 mg) or orally (10 mg) on two separate occasions. Blood samples for the LC-MS analyses of methadone and it's metabolite EDDP were drawn for up to 96 h. Noninvasive infrared pupillometry was performed at the same time as blood sampling. RESULTS The mean absolute rectal bioavailability of methadone was 0.76 (0.7, 0.81), compared to 0.86 (0.75, 0.97) for oral administration (mean (95% CI)). Rectal absorption of methadone was more rapid than after oral dosing with Tmax values of 1.4 (0.9, 1.8) vs. 2.8 (1.6, 4.0) h. The extent of formation of the metabolite EDDP did not differ between routes of administration. Single doses of methadone had a duration of action of at least 10 h and were well tolerated. CONCLUSIONS Rectal administration of methadone results in rapid absorption, a high bioavailability and long duration of action. No evidence of presystemic elimination was seen. Rectal methadone has characteristics that make it a potential alternative to intravenous and oral administration, particularly in cancer pain and palliative care.
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Affiliation(s)
- Ola Dale
- Department of Anaesthesiology, University of Washington, Seattle, USA.
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2956
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Casarin V, Plassard C, Hinsinger P, Arvieu JC. Quantification of ectomycorrhizal fungal effects on the bioavailability and mobilization of soil P in the rhizosphere of Pinus pinaster. New Phytol 2004; 163:177-185. [PMID: 33873794 DOI: 10.1111/j.1469-8137.2004.01093.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
• A differential effect of ectomycorrhizal symbiosis on soil P mobilization and host P nutrition is shown after culture of Pinus pinaster associated with Hebeloma cylindrosporum and Rhizopogon roseolus, poor and good oxalate/proton producers, respectively. • Plants were grown in minirhizoboxes with a thin layer of a Mediterranean soil with a low level of easily available P. This soil was supplemented, or not, with inorganic P and/or CaCO3 . The fungal efficiency on P mobilization and host mineral nutrition was quantified after a 3-month culture period. • R. roseolus had a strong effect on the mobilization of poorly available P, whereas H. cylindrosporum had no effect. However, CaCO3 suppressed the positive effect of R. roseolus. Hydroxyapatite had the greatest effect on growth and P nutrition of nonmycorrhizal plants. With soluble P addition, both ectomycorrhizal species improved shoot P concentrations. • The relationship between soil available P and shoot P concentrations enabled us to separate the fungal effects into two categories, the chemical actions and the soil exploration, explaining the positive effect of ectomycorrhizal symbiosis on P. pinaster P nutrition.
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Affiliation(s)
- Valter Casarin
- Present address: Soil Science Department, São Paulo University, ESALQ, CP 9, 13418-900, Piracicaba (SP), Brazil
| | - Claude Plassard
- Rhizosphère & Symbiose, UMR 1222, AgroM-INRA, 2 Place Viala, Bâtiment 13, 34060 Montpellier Cedex 01, France
| | - Philippe Hinsinger
- Rhizosphère & Symbiose, UMR 1222, AgroM-INRA, 2 Place Viala, Bâtiment 13, 34060 Montpellier Cedex 01, France
| | - Jean-Claude Arvieu
- Rhizosphère & Symbiose, UMR 1222, AgroM-INRA, 2 Place Viala, Bâtiment 13, 34060 Montpellier Cedex 01, France
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2957
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Steinfeld A, Lux A, Maier S, Süverkrüp R, Diestelhorst M. Bioavailability of fluorescein from a new drug delivery system in human eyes. Br J Ophthalmol 2004; 88:48-53. [PMID: 14693772 PMCID: PMC1771947 DOI: 10.1136/bjo.88.1.48] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2003] [Indexed: 11/03/2022]
Abstract
AIM To assess the ocular bioavailability of fluorescein from a novel drug delivery system compared with one single preservative free eye drop. METHODS Part A: In a randomised study 10 volunteers applied the lyophilisate to one eye and a conventional fluorescein eye drop to the fellow eye. Fluorophotometry was performed before and every 2 minutes up to 30 minutes after application in the cornea and anterior chamber. Part B: Another 10 volunteers applied each form of the application. Fluorophotometry was performed before, +2 minutes, and at +8, +10, +12 hours. The dose corresponding to a single fluorescein dose of the lyophilisate was 68 l microg fluorescein SE 0.17%. RESULTS Part A: During the first 30 minutes after administration of the preservative free eye drop of 40 microg the corneal and anterior chamber concentration means were up to 16 times higher in eyes treated with the lyophilisate. Part B: 8-12 hours after application the mean fluorescein concentration in the cornea of the lyophilisate group was two times higher than at baseline. Eyes treated with eye drops had baseline values at +8, +10 and +12 hours. CONCLUSION A significantly better bioavailability was achieved in human eyes by using lyophilisate compared with the same dose from a conventional eye drop. Lyophilisates are a favourable alternative to conventional eye drops since they have no preservatives, higher long term stability, no pH adjustment, and easy handling.
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Affiliation(s)
- A Steinfeld
- Department of Ophthalmology, University of Cologne, Germany.
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2958
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Abstract
Copper is a trace element, important for the function of many cellular enzymes. Copper ions can adopt distinct redox states oxidized Cu(II) or reduced (I), allowing the metal to play a pivotal role in cell physiology as a catalytic cofactor in the redox chemistry of enzymes, mitochondrial respiration, iron absorption, free radical scavenging and elastin cross-linking. If present in excess, free copper ions can cause damage to cellular components and a delicate balance between the uptake and efflux of copper ions determines the amount of cellular copper. In biological systems, copper homeostasis has been characterized at the molecular level. It is coordinated by several proteins such as glutathione, metallothionein, Cu-transporting P-type ATPases, Menkes and Wilson proteins and by cytoplasmic transport proteins called copper chaperones to ensure that it is delivered to specific subcellular compartments and thereby to copper-requiring proteins.
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Affiliation(s)
- H Tapiero
- Université de Paris - Faculté de Pharmacie CNRS UMR 8612, 5, rue Jean-Baptiste-Clément, 94200, Chatenay-Malabry, France.
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2959
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Rengelshausen J, Göggelmann C, Burhenne J, Riedel KD, Ludwig J, Weiss J, Mikus G, Walter-Sack I, Haefeli WE. Contribution of increased oral bioavailability and reduced nonglomerular renal clearance of digoxin to the digoxin-clarithromycin interaction. Br J Clin Pharmacol 2003; 56:32-8. [PMID: 12848773 PMCID: PMC1884337 DOI: 10.1046/j.1365-2125.2003.01824.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
AIMS A clinically important interaction between the cardiac glycoside digoxin and the antibiotic clarithromycin has been suggested in earlier reports. The aim of this study was to investigate the extent of the interaction and the relative contribution of different mechanisms. METHODS In a randomized, placebo-controlled, double-blind cross-over design single oral doses of 0.75 mg digoxin with oral coadministration of placebo or 250 mg clarithromycin twice daily for 3 days were administered to 12 healthy men. Additionally, three of the subjects received single intravenous doses of 0.01 mg x kg(-1) digoxin with oral placebo or clarithromycin. Digoxin plasma and urine concentrations were determined by a highly sensitive radioimmunoassay. RESULTS Oral coadministration of clarithromycin resulted in a 1.7-fold increase of the area under the digoxin plasma concentration-time curve [mean AUC(0,24) +/- SD 23 +/- 5.2 vs. 14 +/- 2.9 microg x L(-1) x h; 95% confidence interval (CI) on the difference 7.0, 12; P = 0.002] and in a reduction of the nonglomerular renal clearance of digoxin [mean ClRng(0, 24) +/- SD 34 +/- 39 vs. 57 +/- 41 mL min-1; 95% CI on the difference 7.2, 45; P = 0.03]. The ratios of mean digoxin plasma concentrations with and without clarithromycin were highest during the absorption period of clarithromycin. After intravenous administration digoxin AUC(0,24) increased only 1.2-fold during coadministration of clarithromycin. CONCLUSIONS Increased oral bioavailability and reduced nonglomerular renal clearance of digoxin both contribute to the interaction between digoxin and clarithromycin, probably due to inhibition of intestinal and renal P-glycoprotein.
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Affiliation(s)
- Jens Rengelshausen
- Department of Internal Medicine VI, Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Heidelberg, Germany
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2960
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Smith FA. Healthy soils, healthy people. New Phytol 2003; 158:424-426. [PMID: 36056505 DOI: 10.1046/j.1469-8137.2003.00779.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Affiliation(s)
- F Andrew Smith
- Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, SA 5005, Australia (tel +61 883036517; fax +61 883036511;email )
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2961
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Abstract
The use of simple spreadsheets is described to create simulations of complex pharmacokinetic phenomena. The basics of spreadsheets are first described and are developed to demonstrate classical pharmacokinetics without the use of differential or integral calculus. Using standard spreadsheet commands, the technique is shown to be applicable to the full range of advanced pharmacokinetic simulations. Demonstrations of the effect of a variety of physiological eventualities are included to show the versatility of the technique. The technique is very simple to use and is always in the complete control of the modeller.
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2962
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Lux A, Maier S, Dinslage S, Süverkrüp R, Diestelhorst M. A comparative bioavailability study of three conventional eye drops versus a single lyophilisate. Br J Ophthalmol 2003; 87:436-40. [PMID: 12642306 PMCID: PMC1771614 DOI: 10.1136/bjo.87.4.436] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2002] [Indexed: 11/04/2022]
Abstract
AIM To study the ocular bioavailability of a triple dose, single application of sodium fluorescein to the human anterior segment from a novel drug delivery device. METHODS In a randomised, open label study 22 healthy volunteers applied a single lyophilisate to one eye (+1 minute) and three conventional eye drops (+1, 16, 31 minutes) of fluorescein ophthalmic solution to the fellow eye. The fluorescein dose of the lyophilisate was 204 mg corresponding to three conventional, preservative-free eye drops of 40 ml fluorescein SE Thilo 0.17% (68 micro g each) (Alcon). Fluorophotometry was performed (Fluorotron Master II Ocumetrics, USA) before and +15, 30, 45, 60, 120, 180, 240, 300, 360, 420 minutes after application. The fluorescein concentrations of the corneal stroma and mid-anterior chamber were analysed by paired t test. RESULTS Cornea and anterior chamber mean values (ng/ml) were significantly higher (p<0.018, paired t test) in the lyophilisate group up to 7 hours after application with the exception of +45 minutes. The mean fluorescein bioavailability from the lyophilisate was up to 11 times higher in the cornea and up to 8.7 times higher in the anterior chamber compared with the three preservative-free eye drops. CONCLUSION A triple dose was delivered to the human eye with a single lyophilisate application for the first time. A significantly better bioavailability was achieved in the cornea and anterior chamber for up to 7 hours by means of drug application with lyophilisates. The application of medications by means of the lyophilisate will improve the treatment of, for example, glaucoma, bacterial, viral and fungal infections, as well as dry eye syndrome.
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Affiliation(s)
- A Lux
- Department of Ophthalmology, University of Cologne, Germany
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2963
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Tannergren C, Knutson T, Knutson L, Lennernäs H. The effect of ketoconazole on the in vivo intestinal permeability of fexofenadine using a regional perfusion technique. Br J Clin Pharmacol 2003; 55:182-90. [PMID: 12580990 PMCID: PMC1894734 DOI: 10.1046/j.1365-2125.2003.01722.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
AIMS To investigate whether the drug-drug interaction between fexofenadine and ketoconazole is localized to efflux transport proteins of the small intestine, and to determine and classify the effective jejunal permeability (Peff) of fexofenadine according to the Biopharmaceutics Classification System (BCS). METHODS Two separate jejunal perfusion experiments were performed using the Loc-I-Gut technique in eight healthy volunteers. During treatment 1 (T1), we investigated the acute effect of ketoconazole on the Peff and plasma pharmacokinetics of fexofenadine. In treatment 2 (T2) we examined the effect of oral pretreatment with ketoconazole (200 mg daily for 5 days) on the same absorption parameters. Each experiment was divided into two periods of 100 min and the jejunal segment was perfused with 93 micro m fexofenadine during both periods. In period 2 of each treatment, fexofenadine was coadministered with 94 micro m ketoconazole. The concentrations of fexofenadine in intestinal perfusate and plasma were measured by liquid chromatography with mass detection. RESULTS During T1, the mean (+/- s.d.) Peff of fexofenadine was low according to the BCS (0.11 +/- 0.11 and 0.04 +/- 0.13 x 10(-4) cm s(-1) in periods 1 and 2, respectively), and the coadministration of ketoconazole in period 2 had no significant acute effect on Peff (95% confidence interval (CI) on the difference -0.37, 0.51). After pretreatment with ketoconazole (T2), the jejunal Peff of fexofenadine increased to 0.29 +/- 0.47 and 0.22 +/- 0.31 x 10-4 cm s(-1) in both periods 1 and 2, respectively, but the change was not statistically significant when compared with T1 (95% CI on the difference -0.62, 0.27 for T1 0-100 min vs T2 0-100 min; -0.54, 0.34 for T1 0-100 min vs T2 100-200 min). Fexofenadine plasma AUC from 0-100 mg showed no significant difference after pretreatment with ketoconazole (55 +/- 101 and 51 +/- 33 micro g ml(-1) min(-1) respectively; 95% CI on the difference -108, 115). Total plasma AUC (0-720 min) was 318 +/- 426 and 426 +/- 232 ng ml(-1) min in T1 and T2, respectively (95% CI on the difference -622, 405). CONCLUSIONS No significant effect of acute coadministration or pretreatment with ketoconazole on the in vivo intestinal absorption of fexofenadine was detected in this study.
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2964
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Cunningham CC, Van Horn CG. Energy availability and alcohol-related liver pathology. Alcohol Res Health 2003; 27:291-9. [PMID: 15540800 PMCID: PMC6668872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Alcohol consumption alters the metabolism of the most common type of cell found in the liver, the hepatocyte. The presence of alcohol in the body causes the liver to use more oxygen-for example, when breaking down the alcohol. Increased oxygen use, in turn, causes oxygen deficits in several key cells, particularly in hepatocytes located near the small hepatic veins. These veins return blood to the heart for re-oxygenation after it has passed through the liver. Hepatocytes surrounding these veins are the first to show signs of liver disease. The damage induced by oxygen deficits may be exacerbated by alcohol-induced deficits in other components that are essential for cell survival. For example, adenosine triphosphate (ATP), the cell's main source of energy, is generated primarily during the course of two sets of metabolic reactions: glycolysis and the mitochondrial oxidative phosphorylation process. Alcohol consumption may interfere with both of these pathways of ATP production through several mechanisms. An inadequate supply of ATP impairs the cell's ability to perform critical functions, including the repair of alcohol-induced cell damage, and may therefore contribute to cell death and alcoholic liver disease.
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Affiliation(s)
- Carol C Cunningham
- Department ofBiochemistry at Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
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2965
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Arlander E, Sjövall J, Sörstad J, Norsten-Höög C, Gustafsson LL. Rectal ropivacaine is absorbed proportionally to the dose, with low intraindividual variability. Br J Clin Pharmacol 2003; 55:14-22. [PMID: 12534636 PMCID: PMC1884191 DOI: 10.1046/j.1365-2125.2003.01732.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
AIMS This study investigated the absorption characteristics and the tolerability of rectally administered ropivacaine, a local anaesthetic, intended as a new local therapy for ulcerative colitis. METHODS Thirty-two healthy volunteers participated in a randomized, placebo-controlled study. In study phase 1 (n = 16, double-blind, crossover) single rectal doses of ropivacaine corresponding to 50, 100 and 200 mg base were given as 20-ml gel enemas. Eight of these subjects also received an i.v. infusion corresponding to 20 mg (2H3)ropivacaine base given with the last rectal dose. In study phase 2 (n = 16, single-blind, crossover) the same rectal doses were given but formulated in 20, 40 and 80 ml gel, respectively. Peripheral venous plasma samples and urine were collected over 12 h after dosing and analysed for ropivacaine base by gas chromatography and (2H3)ropivacaine by gas chromatography-mass spectrometry. Ropivacaine and metabolites were analysed in urine by reversed phase liquid chromatography. RESULTS AUC was proportional to the dose with a point estimate [95% confidence interval (CI)] for the increase, after doubling the dose, of 1.91 (1.66-2.20) and 1.95 (1.78-2.13) in study phases 1 and 2, respectively. The increase in Cmax was also proportional to the dose with corresponding results of 1.76 (1.52-2.04) and 1.84 (1.70-1.99). The volume of the rectal formulation had no influence on either the extent or the time course of absorption. The mean (s.d.) absolute bioavailability (%F) was 56 (18)%. AUC and Cmax showed a two- to three-fold lower intra- than interindividual variability. Zero-order kinetics dominated the first 4 h of the absorption phase. Thereafter first-order kinetics were observed. The terminal half-lives were similar between the rectal doses and were longer than that after the i.v. administration, indicating an absorption-dependent half-life. The main urinary metabolite was 3-hydroxyropivacaine corresponding to about 23% of the dose. The subjects had no difficulties in retaining the doses and rectal administration of ropivacaine was well tolerated, both locally and systemically. CONCLUSIONS Plasma drug concentrations were proportional to the dose after rectally administered doses corresponding to 50-200 mg ropivacaine base in a gel formulation. The drug was well-tolerated. Mean bioavailability was about 60% and not influenced by variations in the enema volume. Initial absorption seemed to follow zero-order kinetics and then first-order kinetics after about 4 h. Cmax and AUC showed considerably less intra- compared with inter-individual variability, resulting in more consistent plasma concentrations within subjects.
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2966
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Pecking M, Montestruc F, Marquet P, Wodey E, Homery MC, Dostert P. Absolute bioavailability of midazolam after subcutaneous administration to healthy volunteers. Br J Clin Pharmacol 2002; 54:357-62. [PMID: 12392582 PMCID: PMC1874433 DOI: 10.1046/j.1365-2125.2002.01665.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS Midazolam is given intravenously for induction of anaesthesia and conscious sedation and by subcutaneous infusion in patients in palliative care units. The objective of the present study was to determine the absolute bioavailability of subcutaneous midazolam and its pharmacokinetics in young, healthy, male volunteers. METHODS Eighteen volunteers were given single doses of 0.1 mg kg-1 midazolam i.v. and s.c. after a wash-out period of 7-15 days in an open-label, randomized, cross-over study. Blood samples were collected up to 12 h post-infusion. Plasma concentrations of midazolam and of its two metabolites, 1'-OHM and 4-OHM, were assessed using an h.p.l.c.-MS method (LOQ 0.5 ng ml-1 for each analyte). Vital signs, cardiac parameters and oximetry were monitored. Local tolerance was determined and adverse events were also monitored. RESULTS After s.c. infusion t(max) and C(max) were 0.51 +/- 0.18 h and 127.8 +/- 29.3 ng ml-1 (mean +/- s.d.), respectively. No statistically significant difference was detected in AUC(0, infinity ) after i.v. and s.c. administration. The mean (+/- s.d.) absolute bioavailability of subcutaneous midazolam was 0.96 (+/- 0.14) (CI 0.84, 1.03). Mean (+/- s.d.) t1/2 was similar after s.c. (3.2 (+/- 1.0) h) and i.v. infusion (2.9 (+/- 0.7) h), although a statistically significant difference was reached (P < 0.05). Mean CL and V of i.v. midazolam were 4.4 +/- 1.0 ml min-1 kg-1 and 1.1 +/- 0.2 l kg-1 (mean +/- s.d.), respectively. Plasma concentrations of 1'-OHM were higher than those of 4-OHM. Few mild and transient adverse events were noted and there were no clinically significant effects on EEG, blood pressure and laboratory parameters. CONCLUSIONS This study has shown that subcutaneous midazolam has excellent bioavailability and that administration of midazolam by this route could be preferable when the intravenous route is inappropriate.
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Affiliation(s)
- M Pecking
- Clinical Research Department, Roche, 92521 Neuilly-sur-Seine, France
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2967
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Martin-Facklam M, Burhenne J, Ding R, Fricker R, Mikus G, Walter-Sack I, Haefeli WE. Dose-dependent increase of saquinavir bioavailability by the pharmaceutic aid cremophor EL. Br J Clin Pharmacol 2002; 53:576-81. [PMID: 12047481 PMCID: PMC1874336 DOI: 10.1046/j.1365-2125.2002.01595.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2001] [Accepted: 02/14/2001] [Indexed: 11/20/2022] Open
Abstract
AIMS Bioavailability of orally administered drugs depends on several factors including active excretion, e.g. by P-glycoprotein (PGP), and presystemic metabolism, e.g. by cytochrome P450 3A (CYP3A), in both gastrointestinal tract and liver. Many drugs including saquinavir are substrates of both PGP and CYP3A. It was the aim of this study to test whether the extremely low bioavailability of saquinavir can be increased dose-dependently in vivo by cremophor EL, an 'inactive' pharmaceutic aid known to inhibit PGP in vitro. METHODS In a randomized, placebo-controlled, double-blind, four phase cross-over design single doses of oral saquinavir (Invirase, 600 mg, without food) were administered with increasing single doses of oral cremophor EL (up to 5000 mg) to eight healthy, male individuals. Saquinavir plasma concentrations were determined by LC/MS/MS up to 48 h after intake. Main outcome measures were area under the plasma concentration time curve (AUC), peak concentration (Cmax), time to reach Cmax (tmax) and terminal elimination half-life (t(1/2)). RESULTS Cremophor EL dose-dependently increased Cmax, AUC(0,4 h), and AUC(0,infinity) of saquinavir. As compared with placebo, the increment observed after 5000 mg cremophor EL was 13-fold for both Cmax and AUC(0,4 h) and 5-fold for AUC(0,infinity). The terminal half-life and the time to reach Cmax (tmax) were unchanged. CONCLUSIONS Cremophor EL increased the systemic availability of saquinavir without affecting its elimination suggesting that cremophor EL is not devoid of pharmacological action and acts as a modulator of the absorption process, probably by inhibiting intestinal PGP.
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Affiliation(s)
- Meret Martin-Facklam
- Department of Internal Medicine VI, Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Bergheimer Strasse 58, D-69115 Heidelberg, Germany
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2968
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Schug BS, Brendel E, Chantraine E, Wolf D, Martin W, Schall R, Blume HH. The effect of food on the pharmacokinetics of nifedipine in two slow release formulations: pronounced lag-time after a high fat breakfast. Br J Clin Pharmacol 2002; 53:582-8. [PMID: 12047482 PMCID: PMC1874338 DOI: 10.1046/j.1365-2125.2002.01599.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2001] [Accepted: 01/17/2002] [Indexed: 11/20/2022] Open
Abstract
AIMS The aim of this study was to investigate the effect of concomitant food intake on the bioavailability of two nifedipine containing modified release dosage forms for once daily administration. The clinical study was performed to investigate the in vivo relevance of pH-dependent differences in the in vitro release properties of the two dosage forms. METHODS This was a randomized, open, 4-way crossover study in 24 healthy, male subjects. Following an overnight fast of 12 h single doses of Adalat OROS or Slofedipine XL were administered either in the fasted state or immediately after a high fat American breakfast. Nifedipine plasma concentrations in samples obtained until 48 h after drug administration were determined using a validated LC-MS/MS method. Calculation of pharmacokinetic parameters was conducted model-independently. The two dosage forms as well as the two administration conditions were compared by calculating point estimates and 90% confidence intervals for the relevant pharmacokinetic parameters. In vitro dissolution tests were performed using a paddle apparatus 3 acc. USP, a pharmacopoeial dissolution system consisting of reciprocating cylinders in flat-bottomed glass vessels, with various buffer systems covering the entire physiological pH-range of the gastrointestinal tract. RESULTS After fasted administration the extent of bioavailability of nifedipine as characterized by AUC(0,infinity) was slightly lower for Slofedipine XL compared with Adalat OROS with a point estimate of 82.3% primarily resulting from pronounced differences in nifedipine concentrations during the first 15 h after administration. Accordingly, maximum plasma concentrations were lower after administration of Slofedipine XL compared with Adalat OROS (point estimate: 84.3%). Under fed conditions the differences in bioavailability between the two products as characterized by the pharmacokinetic parameters AUC(0,tn) and Cmax were greater than after fasting conditions with point estimates of 69.6% and 81.0%, respectively. However, most striking was a pronounced delay in nifedipine absorption observed under fed conditions after administration of Slofedipine XL which resulted in lag-times of more than 15 h in 15 out of 24 subjects. Owing to this lag-time under fed conditions the relative bioavailability of nifedipine from Slofedipine XL compared with Adalat OROS was only 28% over the intended dosing interval of 24 h. CONCLUSIONS In this study a dosage form-dependent food interaction was observed which, under fed conditions, resulted in pronounced differences in the relative bioavailability of nifedipine between Slofedipine XL and Adalat OROS over the intended dosing interval of 24 h. The delay in nifedipine absorption when Slofedipine XL is administered after a high-fat breakfast may be explained by the formulation properties. Slofedipine XL is an erosive tablet with an acid resistant coating whereas Adalat OROS is designed with an osmotic push-pull system. Under fed conditions drug from the single unit enteric coated dosage form exhibits a delayed absorption probably due to an extensively prolonged gastric residence time which does not allow drug release, on the other hand the osmotically driven push-pull system is not sensitive to concomitant food intake. The observed phenomenon might be of therapeutic relevance. For example a change from taking Slofedipine XL in the fed to the fasted state might result in increased systemic concentrations of nifedipine.
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2969
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Cook SV, Chu A, Goodman R. Toxicity of flare and crude hydrocarbon mixtures. ScientificWorldJournal 2002; 2:1418-25. [PMID: 12805927 PMCID: PMC6009641 DOI: 10.1100/tsw.2002.220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The toxicity of whole, saturate, and aromatic hydrocarbon mixtures from flare pit and crude oil sources were evaluated using Lumbricus terrestris. Body burden analysis was used to analyze the intrinsic toxicity of the six hydrocarbon mixtures. The major fractions of the whole mixtures, the saturate, and aromatic fractions had different intrinsic toxicities; the aromatics were more toxic than the saturates. The toxicity of the saturate and aromatic fractions also differed between the mixtures. The flare saturate mixture was more toxic than the crude saturate mixture, while the crude aromatic mixture was more toxic than the flare aromatic mixture. The most dramatic difference in toxicity of the two sources was between the flare whole and crude whole mixtures. The crude whole mixture was very toxic; the toxicity of this mixture reflected the toxicity of the crude aromatic fraction. However, the flare whole mixture was not toxic, due to a lack of partitioning from the whole mixture into the lipid membrane of the exposed worms. This lack of partitioning appears to be related to the relatively high concentrations of asphaltenes and polar compounds in the flare pit whole mixture.
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Affiliation(s)
- Sonja V Cook
- Department of Civil Engineering, University of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada T2N 1N4.
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2970
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Tojal C, Hendrickx F, Tack FM, Maelfait JP, Bogaert N, Willems K, Vernaillen P, Mertens J, Verloo MG. Heavy metal concentrations in the spiders Pirata piraticus (Clerck, 1757) and Clubiona phragmitis (C.L. Koch, 1843) along the Scheldt Estuary (Belgium). ScientificWorldJournal 2002; 2:978-82. [PMID: 12805952 PMCID: PMC6009379 DOI: 10.1100/tsw.2002.170] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wetland ecosystems may be affected by deposition and accumulation of heavy metals. Metal concentrations in the spiders Pirata piraticus and Clubiona phragmitis living in marshes along the river Scheldt (Flanders, Belgium) were analyzed. The organisms were sampled on seven sites along a gradient from freshwater to brackish marshes. Except for lead, P. piraticus contained higher metal concentrations than C. phragmitis. This is related to physiological and ecological differences between species. No correlation was found between metal concentration in the organisms and soil total concentration.
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Affiliation(s)
- Catarina Tojal
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium
| | - Frederik Hendrickx
- Laboratory of Ecology, Biogeography and Nature Conservation, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent,
Belgium
| | - Filip M.G. Tack
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium
- *Filip M.G. Tack:
| | | | - Nicolas Bogaert
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium
| | - Katrien Willems
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium
| | - Pieter Vernaillen
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium
| | - Johan Mertens
- Laboratory of Ecology, Biogeography and Nature Conservation, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent,
Belgium
| | - Marc G. Verloo
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium
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2971
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Penson RT, Joel SP, Roberts M, Gloyne A, Beckwith S, Slevin ML. The bioavailability and pharmacokinetics of subcutaneous, nebulized and oral morphine-6-glucuronide. Br J Clin Pharmacol 2002; 53:347-54. [PMID: 11966664 PMCID: PMC1874271 DOI: 10.1046/j.1365-2125.2002.01554.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS Morphine-6-glucuronide (M6G), one of the active metabolites of morphine, has attracted considerable interest as a potent opioid analgesic with an apparently superior therapeutic index. To date studies have used the intravenous route, which is generally unacceptable in the treatment of cancer related pain. The aim of this study was to define the pharmacokinetics, toxicity and cardio-respiratory effects of three alternative routes of administration of M6G. METHODS Ten healthy volunteers participated in an open randomized study. Subjects received M6G 2 mg as an intravenous bolus, 20 mg orally, 2 mg subcutaneously and 4 mg by the nebulized route. Pulse, blood pressure, respiratory rate and peak flow rate were monitored and subjective toxicity recorded on rating and visual analogue scales. RESULTS After i.v. M6G the mean (+/- s.d.) AUC(0,infinity) standardized to a dose of 1 mg was 223 +/- 57 nmol l(-1) h, mean elimination half-life was 1.7 +/- 0.7 h and the mean clearance was 157 +/- 46 ml min(-1). These parameters were virtually identical after subcutaneous administration which had a bioavailability (F(0,infinity)) of 102 +/- 35% (90% CI 82, 117%) and t(max) of 0.5 +/- 0.2 h. The mean bioavailability of nebulized M6G was 6 +/- 2% (90% CI 4, 7%) with a t(max) of 1.2 +/- 0.8 h. Following oral M6G two plasma M6G peaks were seen in 7 of the 10 subjects, the first with a t(max) of 3.1 (+/- 0.9) h. The second peak had a t(max) of 13.4 (+/-5.0) h, started approximately 4 h after dosing, and was associated with the detection of plasma M3G and morphine, suggesting that M6G was significantly hydrolysed in the gut to morphine, which was then glucuronidated following absorption. Although the overall mean bioavailability was 11 +/- 3% (90% CI 9, 12%), confining the analysis to data from the first peak suggested a bioavailability of directly absorbed M6G of only 4 +/- 4%. Apart from a characteristic dysphoria following intravenous and subcutaneous M6G, there was no significant toxicity. CONCLUSIONS With the minimal toxicity reported in this and previous studies, subcutaneous infusion of M6G may potentially provide clinically useful analgesia for advanced cancer pain. Nebulized M6G is not significantly absorbed via the lungs, and if opiates are shown to have a local effect in the lung, reducing the sensation of breathlessness, then nebulized administration is likely to minimize systemic effects. Oral M6G has poor bioavailability, but is significantly hydrolysed in the gut to morphine, which is subsequently glucuronidated following absorption. This circuitous route accounts for the majority of systemically available M6G after oral administration.
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Affiliation(s)
- Richard T Penson
- Department of Medical Oncology, St Bartholomew's Hospital, West Smithfield, London, EC1A 7BE
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2972
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Abstract
The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh- and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U4+ or UO2(2+)) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO2(2+) and UO2OH+ are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO2(2+) and UO2OH+. The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.
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Affiliation(s)
- Scott J Markich
- Environment Division, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Australia.
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2973
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Abstract
AIM To determine the bioavailability of mupirocin in human nasal secretions and to assess whether the contents of nasal secretions interact appreciably with this antibiotic. METHODS The comparative bioavailability of mupirocin and chlorhexidine in nasal secretions was determined by bioassay after one, four, and eight hours of incubation with pooled secretions from three subjects. The interaction of mupirocin with nasal secretions was characterised by matrix assisted laser desorption time of flight mass spectrometry (MALDI-TOF). RESULTS MALDI-TOF analysis showed that mupirocin was not absorbed by the main fraction of pooled nasal secretions and should remain active. In bioassay, mupirocin retained 100% of its antistaphylococcal activity in nasal secretions, whereas chlorhexidine was significantly reduced from 100 mg/litre to 1.5 mg/litre and from 1000 mg/litre to 38.5 mg/litre, irrespective of incubation time. CONCLUSIONS The high bioavailability of mupirocin in nasal secretions results from the lack of appreciable molecular interactions.
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Affiliation(s)
- R L R Hill
- South London Public Health Laboratory and Department of Infection, Guy's, King's, and St Thomas's School of Medicine, King's Denmark Hill Campus, Bessemer Road, London SE5 9PJ, UK.
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2974
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Nichols DJ, Muirhead GJ, Harness JA. Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: absolute bioavailability, food effects and dose proportionality. Br J Clin Pharmacol 2002; 53 Suppl 1:5S-12S. [PMID: 11879254 PMCID: PMC1874258 DOI: 10.1046/j.0306-5251.2001.00027.x] [Citation(s) in RCA: 246] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS To determine the absolute bioavailability, dose proportionality and the effects of food on the pharmacokinetics of single oral doses of sildenafil citrate. METHODS Three open-label, randomized crossover studies were conducted in healthy male subjects. Absolute bioavailability was determined by comparing pharmacokinetic data after administration of single oral and intravenous 50-mg doses of sildenafil (n=12 subjects). Food effects were examined by comparing pharmacokinetic data for sildenafil and its primary circulating metabolite, UK-103,320, after administration of a single oral 100-mg dose in the fasted and fed states (n=34 subjects). Dose proportionality was assessed from pharmacokinetic data obtained after administration of four single oral doses of sildenafil (25, 50, 100 and 200 mg) to 32 subjects. The safety and tolerability of sildenafil were also assessed in all of these studies. RESULTS The calculated absolute oral bioavailability of sildenafil was 41% (90% CI: 36--47). Food slowed the rate of absorption, delaying mean tmax by approximately 1 h and reducing Cmax by 29% (90% CI: 19--38). Systemic exposure, as assessed by the mean area under the plasma concentration--time curve (AUC), was reduced by 11% (90% CI: 6--16). These food effects were not considered to be of clinical significance. There was statistical evidence of nonproportionality in Cmax and AUC over the dose range 25--200 mg. However the degree of nonproportionality was small, with predicted increases in Cmax and AUC of 2.2- and 2.1-fold, respectively, for a doubling in dose, and was thought to be clinically nonsignificant. Sildenafil was well tolerated in the three studies; the majority of adverse events were mild and transient. CONCLUSIONS Sildenafil had a mean absolute bioavailability of 41%. Food caused small reductions in the rate and extent of systemic exposure; these reductions are unlikely to be of clinical significance. Across the dose range of 25--200 mg, systemic exposure increased in a slightly greater than dose-proportional manner.
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2975
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Allen AV. Selected Peer-Reviewed Papers from the Arsenic Session of the 6th International Conference on the Biogeochemistry of Trace Elements, July 29-August 2, 2001, Guelph, Ontario, Canada. ScientificWorldJournal 2002; 2:134-135. [PMID: 29973840 PMCID: PMC6009400 DOI: 10.1100/tsw.2002.118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2002] [Accepted: 01/10/2002] [Indexed: 11/17/2022] Open
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2976
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Zain-Hamid R, Ismail Z, Mahendra Raj S, Shuaib I, Mohsin SSJ. The Pharmacokinetics of Single Dose vs Steady-State Doses of Propranolol in Cirrhotic Malay Patients. Malays J Med Sci 2002; 9:16-20. [PMID: 22969313 PMCID: PMC3436100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2000] [Revised: 07/12/2001] [Accepted: 08/15/2001] [Indexed: 06/01/2023] Open
Abstract
Pharmacokinetics of propranolol (PRN) given orally were studied in twelve cirrhotic Malay patients [10 males, 2 females], aged 33-62 years [49.83±9.17], body weight 39-72 kg [58.0±8.46] and height 142-168 cm [158.8±7.89] following single 20 mg and steady-state 20 mg tds for 7 days dosing of PRN. Blood samples were withdrawn hourly up to 48 hours. PRN concentrations in the plasma were assayed by HPLC with oxprenolol as the internal standard. Pharmacokinetic parameters were analysed using a non-linear regression program MultiForte. Area under the curve (AUC) as performed using the linear trapezoidal rule. Student's t-test was used to test for statistical significance and AUC in Malay cirrhotic patients was found to be much bigger than that observed in Caucasians. Steady-state AUC was significantly increased following multiple dosing (961.31±7.47 vs 2954.19±1153.34 ng.hr/ml), however, the volume of distribution (V(d)) declined (543.89±292.91 vs 224.14±1003.12 L) significantly compared to that of a single dose. The apparent systemic clearance (CL) was significantly reduced at steady-state (436.04±209.4 vs 129.51±48.42 ml/min) in comparison to single dose therapy. The peak plasma concentration (Cp(max)) was greatly increased at steady-state (54.32±22.37 vs 136.10±38.63 ng/ml). Based on the AUC, PRN bioavailability was greater in cirrhotic Malay patients compared to Caucasians who took only 20 mg instead of 80 mg doses. The decline in drug clearance following steady-state was due to saturation of the metabolizing capacity of hepatic enzymes and a decreased portal blood flow. Reduced V(d) was believed to be caused by increased drug-receptor interactions and decreased tissue/protein binding of PRN in these patients.
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Affiliation(s)
| | | | | | - I.L. Shuaib
- Department of Pharmacology
- Department of Medicine and
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2977
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Abstract
AIMS To establish the bioavailability of tropisetron (5 mg) administered orally as capsule compared with 2 mg given intravenously. METHODS Using a randomized crossover design, 18 healthy volunteers received a single oral dose of tropisetron (5 mg) and an intravenous bolus of tropisetron (2 mg) separated by a wash-out period of 1 week. Plasma concentrations of tropisetron were determined by h.p.l.c. and the pharmacokinetic parameters were estimated. RESULTS The mean pharmacokinetic parameters for 5 mg tropisetron given orally were Cmax 3.46 ng ml(-1), t(max) 2.6 h, t(1/2) 5.7 h and AUC(0,infinity) 32.9 ng ml(-1) h. After intravenous administration initial plasma concentration was 15.1 ng ml(-1), t(1/2) 5.6 h, AUC(0,infinity) 20.7 ng ml(-1) h, V 678 l and CL 1800 ml min(-1). An inverse correlation was demonstrated between CYP2D6 activity, measured by the sparteine metabolic ratio, and the bioavailability (mean 0.60, range 0.27-0.99) of oral tropisetron. CONCLUSIONS Tropisetron exhibits a wide range of oral bioavailability at therapeutic doses, which is mainly determined by CYP2D6 activity.
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Affiliation(s)
- F Kees
- Department of Pharmacology, University of Regensburg, Germany.
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2978
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Suputtamongkol Y, Newton PN, Angus B, Teja-Isavadharm P, Keeratithakul D, Rasameesoraj M, Pukrittayakamee S, White NJ. A comparison of oral artesunate and artemether antimalarial bioactivities in acute falciparum malaria. Br J Clin Pharmacol 2001; 52:655-61. [PMID: 11736876 PMCID: PMC2014567 DOI: 10.1046/j.1365-2125.2001.01458.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2000] [Accepted: 06/14/2001] [Indexed: 11/20/2022] Open
Abstract
AIMS Artesunate and artemether are the two most widely used artemisinin derivatives in the treatment of uncomplicated Plasmodium falciparum malaria, but there is little information on their comparative pharmacokinetics. The aim of this study was to examine the relative oral antimalarial bioavailability and pharmacokinetics of the two derivatives. METHODS The pharmacokinetic properties of oral artesunate and artemether (4 mg kg(-1)) were compared in a randomized cross-over study of 14 adult patients in western Thailand with acute uncomplicated Plasmodium falciparum malaria. Antimalarial activity was compared using a previously validated, sensitive bioassay. RESULTS Despite a 29% lower molar dose, oral artesunate administration resulted in significantly larger mean area under the plasma antimalarial activity time curve and median maximum plasma antimalarial activity than after oral artemether (P CONCLUSIONS The oral antimalarial bioavailability following artemether was significantly lower than that after artesunate. Artemether oral antimalarial bioavailability is reduced in acute malaria.
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2979
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Binh TQ, Ilett KF, Batty KT, Davis TM, Hung NC, Powell SM, Thu LT, Thien HV, Phuöng HL, Phuong VD. Oral bioavailability of dihydroartemisinin in Vietnamese volunteers and in patients with falciparum malaria. Br J Clin Pharmacol 2001; 51:541-6. [PMID: 11422013 PMCID: PMC2014487 DOI: 10.1046/j.1365-2125.2001.01395.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS To obtain comprehensive bioavailability data for artesunate (ARTS) and its active metabolite dihydroartemisinin (DHA) following their separate oral administration to Vietnamese volunteers and to patients with acute, uncomplicated falciparum malaria. METHODS Volunteers were randomized to receive either i.v. ARTS (120 mg) followed by oral ARTS (150 mg) 8 h later (Group 1, n = 10), or i.v. ARTS (120 mg) followed by oral DHA (120 mg) 8 h later. Patients, also received oral ARTS (150 mg; Group 3, n = 8) or DHA (120 mg; Group 2, n = 7), in a randomized cross-over study design. Multiple blood samples were collected after each administration and plasma ARTS and/or DHA concentrations were determined by h.p.l.c. Pharmacokinetic descriptors were obtained from noncompartmental analysis and bioavailability was calculated from AUC data. In the patients, the time to 50% parasite clearance (PCT50) and fever clearance time (FCT) also were measured. RESULTS In Group 1 (volunteers), the mean (95% CI) absolute bioavailability of oral ARTS was 80% (62,98%), while in Group 2 (volunteers), the bioavailability of oral DHA was 45% (34,56%). In the patients (Group 3), the bioavailability of oral DHA relative to oral ARTS was 88% (49,127%). The median PCT50 and FCT were 2.3 and 28 h, respectively. CONCLUSIONS The study shows that the absolute bioavailability of DHA was significantly lower than that for ARTS in healthy volunteers. The bioavailability of ARTS in volunteers was consistent with previous studies in patients with uncomplicated falciparum malaria. The dose-normalized Cmax and AUC(0,infinity) for DHA were significantly greater in patients with falciparum malaria than in healthy volunteers. The high relative bioavailability of DHA in the patients may have been due to lower first-pass clearance. We conclude that, for the treatment of malaria, DHA is likely to be a suitable oral substitute for ARTS. Based on our mean AUC measurements, it appears that equal doses of DHA and ARTS (mg basis) should give equivalent systemic exposure to bioactive DHA in uncomplicated falciparum malaria.
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Affiliation(s)
- T Q Binh
- Tropical Diseases Research Center, Cho Ray Hospital, Ho Chi Minh City, Vietnam
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2980
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Abstract
AIMS To describe the oral disposition of the dietary flavonoid chrysin in healthy volunteers. METHODS Oral 400 mg doses of chrysin were administered to seven subjects. Chrysin and metabolites were assayed in plasma, urine and faeces by h.p.l.c. RESULTS Peak plasma chrysin concentrations were only 3-16 ng ml(-1) with AUCs of 5-193 ng ml(-1) h. Plasma chrysin sulphate concentrations were 30-fold higher (AUC 450-4220 ng ml(-1) h). In urine, chrysin and chrysin glucuronide accounted for 0.2-3.1 mg and 2-26 mg, respectively. Most of the dose appeared in faeces as chrysin. Parallel experiments in rats showed high bile concentrations of chrysin conjugates. CONCLUSIONS These findings, together with previous data using Caco-2 cells, suggest that chrysin has low oral bioavailability, mainly due to extensive metabolism and efflux of metabolites back into the intestine for hydrolysis and faecal elimination.
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Affiliation(s)
- T Walle
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Division of Clinical Pharmacology, Medical University of South Carolina, Charleston, SC 29425, USA.
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2981
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Malingré MM, Beijnen JH, Rosing H, Koopman FJ, Jewell RC, Paul EM, Ten Bokkel Huinink WW, Schellens JH. Co-administration of GF120918 significantly increases the systemic exposure to oral paclitaxel in cancer patients. Br J Cancer 2001; 84:42-7. [PMID: 11139311 PMCID: PMC2363627 DOI: 10.1054/bjoc.2000.1543] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oral bioavailability of paclitaxel is very low, which is due to efficient transport of the drug by the intestinal drug efflux pump P-glycoprotein (P-gp). We have recently demonstrated that the oral bioavailability of paclitaxel can be increased at least 7-fold by co-administration of the P-gp blocker cyclosporin A (CsA). Now we tested the potent alternative orally applicable non-immunosuppressive P-gp blocker GF120918. Six patients received one course of oral paclitaxel of 120 mg/m(2)in combination with 1000 mg oral GF120918 (GG918, GW0918). Patients received intravenous (i.v.) paclitaxel 175 mg/m(2)as a 3-hour infusion during subsequent courses. The mean area under the plasma concentration-time curve (AUC) of paclitaxel after oral drug administration in combination with GF120918 was 3.27 +/- 1.67 microM x h. In our previously performed study of 120 mg/m(2)oral paclitaxel in combination with CsA the mean AUC of paclitaxel was 2.55 +/- 2.29 microM x h. After i.v. administration of paclitaxel the mean AUC was 15.92( )+/- 2.46 microM x h. The oral combination of paclitaxel with GF120918 was well tolerated. The increase in systemic exposure to paclitaxel in combination with GF120918 is of the same magnitude as in combination with CsA. GF120918 is a good and safe alternative for CsA and may enable chronic oral therapy with paclitaxel.
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Affiliation(s)
- M M Malingré
- Department of Medical Oncology, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, Amsterdam, CX, 1066, The Netherlands
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2982
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Abstract
AIMS To measure and compare the systemic bioavailability of fluticasone propionate aqueous nasal spray and a new nasal drop formulation, using a sensitive analytical method and high dose regimen. METHODS Volunteers received four 800 microg doses of fluticasone propionate as a nasal spray or drops over 2 days, separated by an 8 h dose interval. On day 2, blood samples were collected for assay of fluticasone propionate plasma concentrations. RESULTS The mean systemic exposure, for both formulations was 8.5 pg x ml(-1) x h (drops) and 67.5 pg x ml(-1) x h (spray). Mean absolute bioavailabilities were estimated to be 0.06% (drops) and 0.51% (spray), by reference to historical intravenous data. CONCLUSIONS Both formulations exhibited low systemic bioavailability, even at 12 times the normal daily dose. The bioavailability from the nasal drops was approximately eight times lower than from the nasal spray.
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Affiliation(s)
- P T Daley-Yates
- Glaxo Wellcome Research & Development, Greenford Road, Middlesex and Stockley Park West, Middlesex, UK.
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2983
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Daley-Yates PT, Baker RC. Systemic bioavailability of fluticasone propionate administered as nasal drops and aqueous nasal spray formulations. Br J Clin Pharmacol 2001. [PMID: 11167672 PMCID: PMC2014420 DOI: 10.1046/j.0306-5251.2001.01325.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
AIMS To measure and compare the systemic bioavailability of fluticasone propionate aqueous nasal spray and a new nasal drop formulation, using a sensitive analytical method and high dose regimen. METHODS Volunteers received four 800 microg doses of fluticasone propionate as a nasal spray or drops over 2 days, separated by an 8 h dose interval. On day 2, blood samples were collected for assay of fluticasone propionate plasma concentrations. RESULTS The mean systemic exposure, for both formulations was 8.5 pg x ml(-1) x h (drops) and 67.5 pg x ml(-1) x h (spray). Mean absolute bioavailabilities were estimated to be 0.06% (drops) and 0.51% (spray), by reference to historical intravenous data. CONCLUSIONS Both formulations exhibited low systemic bioavailability, even at 12 times the normal daily dose. The bioavailability from the nasal drops was approximately eight times lower than from the nasal spray.
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Affiliation(s)
| | - Richard C Baker
- Glaxo Wellcome Research & DevelopmentStockley Park West, Middlesex, UK
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2984
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Abstract
The toxicokinetics of manganese (Mn) was investigated in male and female rats either following a single intravenous (iv) or oral dose of MnCl2 (6.0 mg Mn/kg), or following a single oral dose of methylcyclopentadienyl manganese tricarbonyl (MMT) (20 mg MMT/kg or 5.6 mg Mn/kg). The plasma concentrations of manganese were quantified by atomic absorption spectrophotometry (AAS). Upon iv administration of MnCl2, manganese rapidly disappeared from blood with a terminal elimination t1/2 of 1.83 h and CL8 of 0.43 L/h/kg. The plasma concentration-time profiles of manganese could be described by C = 41.9e(-424t) + 2.1e(-0.44t). Following oral administration of MnCl2, manganese rapidly entered the systemic circulation (Tmax = 0.25 h). The absolute oral bioavailability was about 13%. Oral dose of MMT resulted in a delayed Tmax(7.6 h), elevated Cmax (0.93 microg/ml), and prolonged terminal t1/2 (55.1 h). The rats receiving MMT had an apparent clearance (CL/F = 0.09 L/h x kg) about 37-fold less than did those who were dosed with MnCl2. Accordingly, the area under the plasma concentration-time curves (AUC) of manganese in MMT-treated rats was about 37-fold greater than that in MnCl2-treated rats. A gender-dependent difference in toxicokinetic profiles of plasma manganese was also observed. Female rats displayed a greater AUC than that of male rats. Although the apparent volume of distribution of manganese was similar in both sexes, the apparent clearance in males was about twice that observed in females. The results indicated that after oral administration, the MMT-derived manganese displayed higher and more prolonged plasma concentration-time profiles than MnCl2-derived manganese. Thus, MMT-derived manganese appeared likely to accumulate in the body following repeated exposure.
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Affiliation(s)
- W Zheng
- School of Public Health, and Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
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2985
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Corey AE, Agnew JR, Valentine SN, Nesbitt JD, Wagner DL, Powell JH, Thompson GA. Comparative oral bioavailability of azimilide dihydrochloride in the fed and fasted states. Br J Clin Pharmacol 2000; 49:279-82. [PMID: 10718785 PMCID: PMC2014920 DOI: 10.1046/j.1365-2125.2000.00139.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS This study investigated the relative oral bioavailability of azimilide dihydrochloride following administration in the fed (high-fat meal) and fasted states. METHODS This was a single-dose, randomized, two-way crossover study in 30 healthy, Caucasian, male subjects. Following oral administration, blood samples were collected over 27 days and analysed for azimilide using h.p.l.c. with u.v. detection. Pharmacokinetic parameters were determined using 'noncompartmental' analysis and compared using an ANOVA and 90% or 95% confidence intervals. RESULTS The extent of absorption was equivalent in the fed and fasted states (ratio = 96.2%; 90% CI=90.5% -102.4%). However, Cmax was decreased 19% following a high-fat meal (ratio=81.4%; 90% CI= 76.2% -87.0%). No difference in tmax or t(1/2),z was observed. CONCLUSIONS Azimilide dihydrochloride may be orally administered to patients without regard to the prandial state.
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Affiliation(s)
- A E Corey
- Procter & Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Road, Mason, OH 45040-9462, USA
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2986
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Abstract
AIMS To examine the influence of cisapride on the pharmacokinetics of ethanol and the impact of gastric emptying monitored by the paracetamol absorption test. METHODS Ten healthy male volunteers took part in a cross-over design experiment. They drank a moderate dose of ethanol 0.30 g kg-1 body weight exactly 1 h after eating breakfast either without any prior drug treatment or after taking cisapride (10 mg three times daily) for 4 consecutive days. In a separate study, the same dose of ethanol was ingested on an empty stomach (overnight fast). Paracetamol (1.5 g) was administered before consumption of ethanol to monitor gastric emptying. Venous blood was obtained at 5-10 min intervals for determination of ethanol by headspace gas chromatography and paracetamol was analysed in serum by high performance liquid chromatography (h.p.l.c.). Results The maximum blood-ethanol concentration (Cmax ) increased from 3.8+/-1.7 to 5.6+/-2.3 mmol l-1 (+/-s.d.) after treatment with cisapride (95% confidence interval CI on mean difference 0.28-3.28 mmol l-1 ). The area under the blood-ethanol curve (AUC) increased from 6.3+/-3.5 to 7.9+/-2.6 mmol l-1 h after cisapride (95% CI -0. 74-3.9 mmol l-1 h). The mean blood ethanol curves in the cisapride and no-drug sessions converged at approximately 2 h after the start of drinking. Both Cmax and AUC were highest when the ethanol was ingested on an empty stomach (Cmax 9.5+/-1.7 mmol l-1 and AUC 14. 6+/-1.9 mmol l-1 h), compared with drinking 1 h after a meal and regardless of pretreatment with cisapride. CONCLUSIONS A small but statistically significant increase in Cmax occurred after treatment with cisapride owing to faster gastric emptying rate as shown by the paracetamol absorption test. However, the rate of absorption of ethanol, as reflected in Cmax and AUC, was greatest after drinking the alcohol on an empty stomach. The cisapride-ethanol interaction probably lacks any clinical or forensic significance.
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Affiliation(s)
- S Kechagias
- Division of Gastroenterology and Hepatology, University Hospital, Linköping; Department of Emergency Medicine, University Hospital, Linköping, Sweden
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2987
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Abstract
AIMS To examine the effect of timing of a risedronate dose relative to food intake on the rate and extent of risedronate absorption following single-dose, oral administration to healthy male and female volunteers. METHODS A single-dose, randomized, parallel study design was conducted with volunteers assigned to four treatment groups (31 or 32 subjects per group, 127 subjects total). Each subject was orally administered 30 mg risedronate. Group 1 was fasted for 10 h prior to and 4 h after dosing (fasted group); Groups 2 and 3 were fasted for 10 h and were dosed 1 and 0.5 h, respectively, before a high-fat breakfast; and Group 4 was dosed 2 h after a standard dinner. Blood and urine samples were collected for 168 h after dosing. Pharmacokinetic parameters were estimated by simultaneous analysis of risedronate serum concentration and urinary excretion rate-time data. RESULTS Extent of risedronate absorption (AUC and Ae ) was comparable (P=0.4) in subjects dosed 2 h after dinner and 0.5 h before breakfast; however, a significantly greater extent of absorption occurred when risedronate was given 1 or 4 h prior to a meal (1.4- to 2.3-fold greater). Administration 0.5, 1, or 4 h prior to a meal resulted in a significantly greater rate of absorption (Cmax 2.8-, 3.5-, and 4.1-fold greater, respectively) when compared with 2 h after dinner. CONCLUSIONS The comparable extent of risedronate absorption when administered either 0.5-1 h before breakfast or 2 h after an evening meal support previous clinical studies where risedronate was found to have similar effectiveness using these dosing regimens. This flexibility in the timing of risedronate administration may provide patients an alternative means to achieve the desired efficacy while maintaining their normal daily routine.
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Affiliation(s)
- D Y Mitchell
- Procter & Gamble Pharmaceuticals, Mason, Ohio, USA
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2988
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Herben VM, Rosing H, ten Bokkel Huinink WW, van Zomeren DM, Batchelor D, Doyle E, Beusenberg FD, Beijnen JH, Schellens JH. Oral topotecan: bioavailablity and effect of food co-administration. Br J Cancer 1999; 80:1380-6. [PMID: 10424739 PMCID: PMC2363072 DOI: 10.1038/sj.bjc.6690532] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The aims of the study were twofold: (1) to evaluate the effect of food on the relative oral bioavailability of topotecan gelatin capsules in patients with solid tumours, and (2) to determine the absolute bioavailability of oral topotecan with reference to the intravenous (i.v.) formulation. The study had a randomized two-period cross-over design. On day 1 of the first treatment course patients were administered 2.3 mg m(-2) day(-1) of oral topotecan with or without a high-fat breakfast. They crossed over to receive the alternate regimen on day 2. In the second course (3 weeks later) fasted patients received topotecan orally (2.3 mg m(-2) day(-1)) or i.v. (1.5 mg m(-3) day). They crossed over to receive the alternate regimen on day 2. On days 3-5 of both treatment courses patients received oral topotecan. Plasma pharmacokinetics were performed on days 1 and 2 of the first and second course using a high-performance liquid chromatographic assay. Eighteen patients were enrolled in the study. The ratio of the area under the curve to infinity during fasted and high-fat treatment was 0.93+/-0.23 (90% confidence interval (CI) 0.83-1.03). Maximal plasma concentrations of topotecan were similar after ingestion of the capsules with (10.6+/-4.4 ng ml(-1)) or without food (9.2+/-4.1 ng ml(-1)) (P = 0.130). The time needed to reach maximal plasma levels was significantly prolonged after food intake (median 3.1 h, range 2.8-6.1) compared to fasted conditions (2.0 h, range 1.1-8.1) (P = 0.013). The absolute bioavailability of topotecan averaged 42+/-13% (90% CI 37-47%). The apparent terminal half-life was significantly longer after administration of oral topotecan (3.9+/-1.0 h) than after i.v. administration (2.7+/-0.4 h) (P < 0.001). Topotecan demonstrates suitable bioavailability for oral treatment. Co-administration of the topotecan gelatin capsules with a high-fat breakfast leads to a small decrease in absorption rate but does not affect the extent of absorption.
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Affiliation(s)
- V M Herben
- Slotervaart Hospital/The Netherlands Cancer Institute, Department of Pharmacy and Pharmacology, Amsterdam
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2989
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Van Der Heyden SA, Highley MS, De Bruijn EA, Tjaden UR, Reeuwijk HJ, Van Slooten H, Van Oosterom AT, Maes RA. Pharmacokinetics and bioavailability of oral 5'-deoxy-5-fluorouridine in cancer patients. Br J Clin Pharmacol 1999; 47:351-6. [PMID: 10233196 PMCID: PMC2014244 DOI: 10.1046/j.1365-2125.1999.00899.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
AIMS Oral administration of 5-fluorouracil (FUra), an important cytotoxic agent, is limited by a wide variation in bioavailability. 5'-deoxy-5-fluorouridine (dFUrd), a masked form of FUra, has shown promise clinically when given intravenously or orally as a solution or tablet. This study investigates the efficacy of an oral capsule formulation of dFUrd in generating continuous systemic levels of this compound in cancer patients. METHODS Six patients with advanced intestinal or ovarian malignancies were given three cycles of dFUrd, days 1-5, at intervals of 4 weeks. The doses of dFUrd were 600 mg m-2 three times daily, 800 mg m-2 three times daily, and 1000 mg m-2 three times daily, on cycles one, two and three, respectively (total dose 36 g m-2 ). The initial dose in each cycle was given as a slow intravenous injection over 10 min, and the remainder orally. Plasma and urine levels of dFUrd and two of its metabolites, FUra and 5,6-dihydro-5-fluorouracil (FUraH2 ), were monitored in six patients at each dose level. RESULTS All six patients completed the study, receiving three different doses over a 3 month period, following which one had achieved a partial response, one had stable disease, and four had developed progressive disease. Side-effects were negligible, and only two instances of transient diarrhoea WHO grade 1 were seen. Total body clearance (CLtot) of intravenous dFUrd decreased with increasing dose; 2.7, 2.0 and 1.3 l min-1 m-2, following doses of 600, 800 and 1000 mg m-2, respectively. The mean elimination half-life of intravenous dFUrd increased with the dose from 15 to 22 min. Oral dFUrd was rapidly absorbed with a lag time of less than 20 min. The mean elimination half-life (t1/2, z ) of oral dFUrd was 32-45 min in the dose range 600-1000 mg m-2. The AUC of FUra and FUraH2 increased overproportionally with increasing intravenous doses of dFUrd. The mean systemic bioavailability of oral dFUrd was 34-47%. CONCLUSIONS dFUrd, which selectively releases the antimetabolite FUra in tumour cells, can be given orally at doses of 600-1000 mg m-2 three times daily for 5 days. The systemic levels achieved are equivalent to those seen following continuous infusions of dFUrd or FUra. Toxicity is tolerable, and further clinical investigation of oral dFUrd is warranted.
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Affiliation(s)
- S A Van Der Heyden
- Laboratory for Experimental Oncology, University of Leuven, B-3000 Leuven, Belgium
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2990
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Abstract
meta-iodobenzylguanidine (MIBG) radiolabelled with iodine-131 is used for diagnosis and treatment of neuroadrenergic neoplasms such as phaeochromocytoma and neuroblastoma. In addition, non-radiolabelled MIBG, administered i.v., is used in several clinical studies. These include palliation of the carcinoid syndrome, in which MIBG proved to be effective in 60% of the patients. Oral MIBG administration might be convenient to maintain palliation and possibly improve the percentage of responders. We have, therefore, investigated the feasibility of oral administration of MIBG in an animal model. Orally administered MIBG demonstrated a bioavailability of 59%, with a maximal tolerated dose of 60 mg kg(-1). The first and only toxicity encountered was a decrease in renal function, measured by a reduced clearance of [51Cr]EDTA and accompanied by histological tubular damage. Repeated MIBG administration of 40 mg kg(-1) for 5 sequential days or of 20 mg kg(-1) for two courses of 5 sequential days with a 2-day interval did not affect renal clearance and was not accompanied by histological abnormalities in kidney, stomach, intestines, liver, heart, lungs, thymus, salivary glands and testes. Because of a sufficient bioavailability in absence of gastrointestinal toxicity, MIBG is considered suitable for further clinical investigation of repeated oral administration in patients.
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Affiliation(s)
- A Kuin
- Department of Experimental Therapy, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Amsterdam
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2991
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Kohno T, Murasugi N, Sakurai H, Watabe K, Nakamuta H, Koida M, Sugie Y, Nomura M, Yanagawa A. Development of a highly sensitive and specific two-site enzyme immunoassay for parathyroid hormone (1-34): application to pharmacokinetic study on intranasal parathyroid hormone (1-34) in human. J Clin Lab Anal 1998; 12:268-75. [PMID: 9773956 PMCID: PMC6808088 DOI: 10.1002/(sici)1098-2825(1998)12:5<268::aid-jcla3>3.0.co;2-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A highly sensitive and specific two-site enzyme immunoassay for parathyroid hormone (1-34) (PTH(1-34)) and its usability for the pharmacokinetic study are described. Plasma samples were incubated simultaneously with 2,4-dinitrophenylated anti-PTH(1-34) IgG and anti-PTH(1-34) Fab'-beta-D-galactosidase conjugate. The immune complex formed of the three components was trapped onto (anti-2,4-dinitrophenyl group) IgG-coated polystyrene balls. beta-D-Galactosidase activity bound to the polystyrene balls was assayed by fluorometry. The practical detection limit of PTH(1-34) was 50 fg (12 amol)/0.05 ml of sample and 1 pg/ml as the concentration and practically no interference occurred by PTH(1-84) and PTH-related protein (1-34) up to 300 pg/ml and 10 ng/ml, respectively. The application of this method has enabled us to directly estimate the bioavailability of PTH(1-34) dosed intranasally at the prescribed level (0.090 mg). The pharmacokinetic parameters of the intranasal PTH(1-34) (n = 4) thus estimated were as follows: the area under the plasma concentration-time curve (AUC) = 20,500+/-15,900(SD) pg.min/ml; the mean residence time (MRT) = 194+/-16.3(SD) min; and the maximal concentration (Cmax) = 98+/-51 (SD) pg/ml with the maximal time (Tmax) = 35.0+/-12.2(SD) min.
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Affiliation(s)
- T Kohno
- Department of Environmental Health Sciences, Setsunan University, Hirakata, Osaka, Japan
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2992
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Abstract
The experimental and clinical effectiveness of nasal salmon calcitonin (SCT) for treatment of osteoporosis in humans has been well established, but none is known yet about the pharmacokinetic property in relation to therapeutic efficacy, especially when used in a therapeutic dose range. This preclinical study was designed to evaluate such a property, first of all in rats, using a novel heterogeneous two-site enzyme immunoassay that has allowed us to evaluate the pharmacokinetic property of parenteral SCT in rats due to the high sensitivity (the detection limit = 2 pg of SCT/ml of plasma). It was found that as early as 10 min after the nasal dosing of 1.25, 5, or 20 U/rat, the SCT immunoactivity became detectable in plasma and thereafter it waned rapidly with time. Hypocalcemia developed in a dose-dependent manner, but with a delay of approximately 20 min from the peak of the immunoactivity and lasted hours. The pharmacokinetic parameters measured for the doses (1.25, 5, and 20 U/rat) were as follows; the AUCs (pg.hr/ml) = 20.8, 89.0, and 189, and the MRTs (min) = 52, 54, and 45, respectively. The results appear to suggest: (1) the unexpected quick transfer of nasal SCT into and from the circulation, (2) a delayed onset of hypocalcemia and possibly its anti-osteopenic action, both of which may last longer, (3) that keeping the plasma SCT above the in vitro anti-osteoclastic level (approximately 1 pM) only for a few hours per 2 days would be enough for inducing the distinct anti-osteopenic effect in rats, and (4) the feasibility of designing the clinical study as to the pharmacokinetics and pharmacodynamics of nasal SCT on humans.
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Affiliation(s)
- H Nakamuta
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Osaka, Japan
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2993
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Ezzet F, Mull R, Karbwang J. Population pharmacokinetics and therapeutic response of CGP 56697 (artemether + benflumetol) in malaria patients. Br J Clin Pharmacol 1998; 46:553-61. [PMID: 9862244 PMCID: PMC1873796 DOI: 10.1046/j.1365-2125.1998.00830.x] [Citation(s) in RCA: 174] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/1997] [Accepted: 07/02/1998] [Indexed: 11/20/2022] Open
Abstract
AIMS To investigate the pharmacokinetic and pharmacodynamic properties of artemether and benflumetol in a fixed combination tablet (CGP 56697) and to offer an explanation for the lower than expected cure rate in a Thai clinical trial. METHODS Two hundred and sixty patients were enrolled into a randomized, double-blind, parallel group, dose-finding trial. CGP 56697 was given orally, either as: A, 4 x 4 tablets over 48 h; B, 4 x 2 tablets over 48 h or C, 3 x 4 tablets over 24 h. Each tablet contained artemether 20 mg amd benflumetol 120 mg. The pharmacokinetics were determined using a population-based approach combining full profiles (42 patients) and sparse data (218 patients). Parasite clearance time and 28 day cure rate were correlated with the derived pharmacokinetic parameters. RESULTS The median absorption half-life of benflumetol was 5.3 h, with a tmax of 10 h and terminal elimination half-life of 4.5 days. For artemether (and its metabolite, dihydroartemisinin), the corresponding values were 1.9 (1.9) h, 1.8 (1.2) h, and 0.84 (0.43) h. The variability in bioavailability of artemether and dihydroartemisinin was large both between doses and between patients, but was less pronounced for benflumetol. Compared with the first dose, benflumetol bioavailability was estimated to increase three-fold by the third and fourth doses. Higher artemether or dihydroartemisinin AUC was found to decrease parasite clearance time. Higher benflumetol AUC was found to significantly increase the chance of cure. CONCLUSIONS Using a population-based approach it was confirmed that the pharmacokinetic and pharmacodynamic properties of benflumetol and artemether differ markedly. Benflumetol AUC is associated with cure and the effect of benflumetol when coadministered with artemether is to prevent recrudescence. The mode of action of benflumetol is consistent with its longer elimination half-life. A short course of low-dose artemether, which is rapidly absorbed and has a short elimination half-life, produced effective parasite clearance. The complementary pharmacokinetic and pharmacodynamic properties of benflumetol and artemether was the main rationale for developing a fixed-dose combination. While the 4 x 4 dose regimen is very effective in most endemic areas, the poorer absorption (2.5 fold lower than in China) and the more resistant parasites in Thailand require higher doses of this drug.
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Affiliation(s)
- F Ezzet
- Novartis Pharma Ag., Basel, Switzerland
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2994
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Seaber EJ, Peck RW, Smith DA, Allanson J, Hefting NR, van Lier JJ, Sollie FA, Wemer J, Jonkman JH. The absolute bioavailability and effect of food on the pharmacokinetics of zolmitriptan in healthy volunteers. Br J Clin Pharmacol 1998; 46:433-9. [PMID: 9833595 PMCID: PMC1873688 DOI: 10.1046/j.1365-2125.1998.00809.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS Zolmitriptan (Zomig (formerly 311C90)) is a novel 5-HT1B/1D receptor agonist developed for the acute oral treatment of migraine. A highly sensitive LCMS-MS assay has been developed which allows quantification of plasma concentrations of zolmitriptan and its active metabolite, 183C91, after therapeutic doses. Two studies using this assay method were conducted to investigate the pharmacokinetics, including absolute bioavailability, of 2.5 and 5 mg oral doses of zolmitriptan in men and women, the dose-proportionality of 2.5, 5 and 10 mg doses and the effect of food on the pharmacokinetics of a 5 mg oral dose. METHODS Two randomized, balanced, open-label, 4-period crossover studies were conducted in a total of 32 healthy volunteers. The first study determined the absolute bioavailability of 2.5 and 5 mg doses of zolmitriptan and compared the pharmacokinetics in men and women. The second study examined the dose-proportionality in pharmacokinetics after fasting doses of 2.5, 5 and 10 mg, and the effect of food on a 5 mg dose. Blood pressure, heart rate, ECG, clinical chemistry, haematology and adverse events were also monitored. RESULTS The mean (s.d.) absolute oral bioavailability was 0.41 (0.14 and 0.40) 0.09 after 2.5 mg and 0.48+/-0.14 and 0.36+/-0.07 after 5 mg in women and men, respectively. Without adjustment for bodyweight, plasma concentrations of zolmitriptan, but not 183C91, were higher in women than men. Mean (+/-s.d.) AUC was 32.7+/-10.1 and 60.2+/-26.8 ng ml(-1) h after 5 mg in men and women, respectively (95% CI for ratio 0.43-0.77). After 2.5 mg mean (+/-s.d.) AUC was 18.4+/-5.4 and 23.1+/-9.9 ng ml(-1) h in men and women, respectively (95% CI for ratio 0.61-1.09). However, these differences were of no clinical significance. Cmax and AUC of oral zolmitriptan were dose-proportional and there was a 13 and 16% fall in mean zolmitriptan Cmax and AUC, respectively, when administered after food. Adverse effects were minor, predominantly mild and transient, and there were no clinically significant effects on ECG, blood pressure, or laboratory parameters. CONCLUSIONS At therapeutic doses zolmitriptan has good oral bioavailability in healthy volunteers and has dose-proportional pharmacokinetics that are not affected by food to any clinically relevant extent.
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Affiliation(s)
- E J Seaber
- Glaxo Wellcome Research and Development, Greenford, Middlesex, UK
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2995
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Batty KT, Ilett KF, Edwards G, Powell SM, Maggs JL, Park BK, Davis TM. Assessment of the effect of malaria infection on hepatic clearance of dihydroartemisinin using rat liver perfusions and microsomes. Br J Pharmacol 1998; 125:159-67. [PMID: 9776356 PMCID: PMC1565587 DOI: 10.1038/sj.bjp.0702023] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The clearance of dihydroartemisinin (DHA) in control and malaria-infected (MI) rats was investigated using the isolated perfused rat liver (IPRL) model and hepatic microsomal studies. 2. In the recirculating IPRL, clearance of DHA was reduced from a mean (s.d.) of 8.2+/-1.8 ml min(-1) in controls (n=8) to 6.0+/-1.0 ml min(-1) in MI (n=8; P<0.01). Clearance in control livers was similar to the perfusion flow rate, suggesting a high hepatic extraction ratio for DHA. 3. Single-pass IPRL studies in controls (n=8) showed that DHA bioavailability at 1.3, 8 and 38 microm was 0.026+/-0.020, 0.043+/-0.025 and 0.14+/-0.06, respectively (P<0.001 for 8 microM vs 38 microM). In MI livers (n=5), DHA bioavailability at 8 and 38 microM was 0.18+/-0.07 and 0.40+/-0.08, respectively (P=0.002). Bioavailability was higher in the MI group than in controls (P=0.01 at 8 microM and P<0.001 at 38 microM). DHA-glucuronide was the sole biliary metabolite. 4. Hepatic microsomal studies of DHA-glucuronide formation showed a significantly lower Vmax but no significant change in Km, in MI compared to control livers (n=6). Intrinsic metabolic clearance (Vmax/Km) was higher in control than in MI livers (5.2+/-1.3 and 2.5+/-1.4 microl min(-1) mg(-1), respectively; P=0.006). 5. These studies demonstrate that DHA has a high, concentration-dependent hepatic extraction ratio that is reduced by 20-30% in the P. berghei rodent malaria model. The impaired hepatic clearance of DHA in MI is attributable to a reduction in intrinsic metabolic clearance.
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Affiliation(s)
- K T Batty
- Department of Pharmacology, University of Western Australia, Nedlands, Australia
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2996
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Mather LE, Woodhouse A, Ward ME, Farr SJ, Rubsamen RA, Eltherington LG. Pulmonary administration of aerosolised fentanyl: pharmacokinetic analysis of systemic delivery. Br J Clin Pharmacol 1998; 46:37-43. [PMID: 9690947 PMCID: PMC1873979 DOI: 10.1046/j.1365-2125.1998.00035.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS Pulmonary drug delivery is a promising noninvasive method of systemic administration. Our aim was to determine whether a novel breath-actuated, microprocessor-controlled metered dose oral inhaler (SmartMist, Aradigm Corporation) could deliver fentanyl in a way suitable for control of severe pain. METHODS Aersolised pulmonary fentanyl base 100-300 microg was administered to healthy volunteers using SmartMist and the resultant plasma concentration-time data were compared with those from the same doses administered by intravenous (i.v.) injection in the same subjects. RESULTS Plasma concentrations from SmartMist were similar to those from i.v. injection. Time-averaged bioavailability based upon nominal doses averaged approximately 100%, and was > 50% within 5 min of delivery. Fentanyl systemic pharmacokinetics were similar to those previously reported with no trends to dose-dependence from either route. Side-effects (e.g. sedation, lightheadedness) were the same from both routes. CONCLUSIONS Fentanyl delivery using SmartMist can provide analgetically relevant plasma drug concentrations. This, combined with its ease of noninvasive use and transportability, suggests a strong potential for field and domicilliary use, and for patient controlled analgesia without the need for i.v. cannulae.
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Affiliation(s)
- L E Mather
- Department of Anaesthesia and Pain Management, University of Sydney at Royal North Shore Hospital, St Leonards, NSW, Australia
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2997
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Lecaillon JB, Godbillon J, Campestrini J, Naquira C, Miranda L, Pacheco R, Mull R, Poltera AA. Effect of food on the bioavailability of triclabendazole in patients with fascioliasis. Br J Clin Pharmacol 1998; 45:601-4. [PMID: 9663817 PMCID: PMC1873654 DOI: 10.1046/j.1365-2125.1998.00725.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
AIMS Preliminary results indicate higher absorption of triclabendazole (TCBZ) administered postprandially. Therefore, the influence of food on the pharmacokinetics of TCBZ and its active sulphoxide (TCBZ-SO) and sulphone (TCBZ-SO2) metabolites was investigated. METHODS Two single doses (10 mg kg(-1)) of TCBZ were administered to 20 patients with fascioliasis. Ten patients were first given the drug after a high energy breakfast and then, 48 h later, after an overnight fast. The other 10 patients first received the drug in fasting state and then, 48 h later, after breakfast. A low energy breakfast was served 2 h after drug administration for fasting state. RESULTS Compared with the fasting state, an increased AUC and Cmax after food intake (significant, P < 0.0001) was shown from the values of TCBZ, TCBZ-SO and TCBZ-SO2. The mean AUC for TCBZ (fasting: 1.55, fed: 5.72 micromol l(-1) h), TCBZ-SO (fasting: 177, fed: 386 micromol l(-1) h) and TCBZ-SO2 (fasting: 13.9, fed: 30.5 micromol l(-1) h) indicated a large availability increase with food and the strong systemic predominance of the active sulphoxide metabolite over the unchanged drug. (All patients were cured at the end of the trial except one who required a second course of two postprandial doses of triclabendazole (10 mg kg(-1) each). Tolerability to the treatment among the patients was good. CONCLUSIONS The administration of triclabendazole with food is recommended for improved systemic availability in patients with fascioliasis or paragonimiasis.
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Affiliation(s)
- J B Lecaillon
- Novartis Pharma S.A., Drug Metabolism & Pharmacokinetics, Rueil-Malmaison, France
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2998
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Abstract
AIMS To study the pharmacokinetics and bioavailability of the prodrug bambuterol and its bronchodilator moiety terbutaline in healthy subjects. METHODS Eight healthy subjects (four women) received intravenous doses of bambuterol and terbutaline. On a third occasion, they, plus another four subjects, ingested oral bambuterol as a single dose followed by repeated doses once daily for 7 days. Plasma concentrations and urinary excretion of bambuterol and terbutaline were measured. RESULTS After intravenous administration, renal clearances of bambuterol and terbutaline were similar (about 140 ml min(-1)), but there was a five-fold difference in total clearance (bambuterol 1.25 l min(-1), terbutaline 0.23 l min(-1)). Volume of distribution (Vss) was 1.6 l kg(-1) b.w. for both substances. A similar renal clearance of bambuterol was found during oral administration but that of terbutaline decreased (to about 120 ml min(-1)). Mean terminal half-life of bambuterol was 2.6 h after intravenous and 12 h after oral administration, implying that uptake was rate-limiting. Mean residence time of terbutaline generated from oral bambuterol was 34 h compared with 8.0 h when terbutaline as such was infused. Generated terbutaline had a bioavailability of 36% (28-46) after intravenous and 10.2% (6.1-13.2) after oral administration of the prodrug. Bambuterol was well tolerated. The mean activity of plasma cholinesterase, an enzyme catalyzing bambuterol metabolism, was inhibited between 30-60% during repeated oral dosing. It virtually regained original activity within 48 h after the last dose. CONCLUSIONS The plasma concentration ofterbutaline fluctuated little during repeated oral administration (mean peak: trough ratio 1.9), as a result of prolonged absorption of bambuterol and slow formation of terbutaline. Thus, the pharmacokinetic properties of bambuterol make it suitable for oral once-daily dosage.
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Affiliation(s)
- L Nyberg
- Human Pharmacology, Astra Draco AB, Lund, Sweden
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2999
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Abstract
AIMS Saquinavir is a potent HIV protease inhibitor whose effectiveness is limited in vivo by its low bioavailability. Since saquinavir is metabolized by CYP3A4, the effect of grapefruit juice, an inhibitor of CYP3A4, was investigated on its bioavailability. METHODS After an overnight fast, eight healthy volunteers were treated with either 400 ml grapefruit juice or water before intravenous (12 mg) or oral saquinavir (600 mg) was administered. Serial blood samples were obtained over the following 24 h and standardized meals were served 5 and 10 h after the administration of saquinavir. The plasma concentrations of saquinavir were determined by high-performance liquid chromatography and pharmacokinetic parameters were calculated by routine methods. RESULTS The AUC was not affected by grapefruit juice after intravenous administration, but it increased significantly from 76+/-96 (water, mean (s.d.) to 114+/-70 (microg l[-1] h) (grapefruit juice) after oral saquinavir. Similarly, the oral bioavailability of saquinavir increased by a factor of 2 with grapefruit juice (from 0.7% to 1.4%). In contrast, clearance, volume of distribution and elimination half-life of saquinavir were not affected by grapefruit juice. After oral, but not after intravenous administration, the plasma concentration-time curve showed a second peak after lunch irrespective of pretreatment, suggesting enhancement of absorption by food. CONCLUSIONS The studies demonstrate that grapefruit juice increases the bioavailability of saquinavir without affecting its clearance, suggesting that inhibition of intestinal CYP3A4 may contribute. Since the antiretroviral effect of saquinavir is dose-dependent, inhibition of CYP3A4 may represent a way to enhance its effectiveness without increasing the dose.
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Affiliation(s)
- H H Kupferschmidt
- Division of Clinical Pharmacology & Toxicology, University Hospital, Zürich, Switzerland
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3000
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Batty KT, Thu LT, Davis TM, Ilett KF, Mai TX, Hung NC, Tien NP, Powell SM, Thien HV, Binh TQ, Kim NV. A pharmacokinetic and pharmacodynamic study of intravenous vs oral artesunate in uncomplicated falciparum malaria. Br J Clin Pharmacol 1998; 45:123-9. [PMID: 9491824 PMCID: PMC1873351 DOI: 10.1046/j.1365-2125.1998.00655.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/1997] [Accepted: 09/19/1997] [Indexed: 02/06/2023] Open
Abstract
AIMS To obtain comprehensive pharmacokinetic and pharmacodynamic data for artesunate (ARTS) and its active metabolite dihydroartemisinin (DHA) following i.v. and oral administration of ARTS to patients with acute, uncomplicated falciparum malaria. METHODS Twenty-six Vietnamese patients with falciparum malaria were randomized to receive either i.v. ARTS (120 mg; group 1) or oral ARTS (100 mg; group 2), with the alternative preparation given 8 h later in an open crossover design. Mefloquine (750 mg) was administered at 24 h. Plasma concentrations of ARTS and DHA were determined by h.p.l.c. assay. Pharmacokinetic parameters were calculated by non-compartmental methods. The time to 50% parasite clearance (PCT50) was calculated by linear interpolation of parasite density determinations. Linear least squares and multiple linear regression analyses were used to evaluate pharmacokinetic-pharmacodynamic relationships. RESULTS Following i.v. bolus, ARTS had a peak concentration of 29.5 microM (11 mg l[-1]), elimination t1/2 = 2.7 min, CL = 2.33 l h(-1) kg(-1) and V = 0.14 l kg(-1). The Cmax for DHA was 9.3 microM (2.64 mg l[-1]), t1/2 = 40 min, CL =0.75 l h(-1) kg(-1) and V = 0.76 l kg(-1). Following oral ARTS, relative bioavailability of DHA was 82%, Cmax was 2.6 microM (0.74 mg l[-1]), t1/2 = 39 min, and MAT = 67 min. Overall, the PCT50 and fever clearance time (FCT) were 6.5 h and 24 h, respectively. There was no correlation between PCT50 or FCT and AUC, Cmax or MRT for DHA. CONCLUSIONS Despite rapid clearance of ARTS and DHA in patients with uncomplicated falciparum malaria, prompt parasite and fever clearance were achieved. High relative bioavailability of DHA following oral ARTS administration, and clinical outcomes comparable with those after i.v. ARTS, support the use of the oral formulation in the primary care setting.
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Affiliation(s)
- K T Batty
- Department of Medicine, University of Western Australia, Fremantle Hospital
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