Effects of selective COX-2 inhibition on prostanoids and platelet physiology in young healthy volunteers

BACKGROUND

Selective inhibitors of cyclooxygenase-2 (COX-2) called coxibs, are effective anti-inflammatory and analgesic drugs. Recently, these drugs were associated with an increased risk for myocardial infarction and atherothrombotic events. The hypothesis of thromboxane-prostacyclin imbalance has been preferred to explain these unwanted effects.

METHODS

We studied the effects of 14 days intake of rofecoxib (25 mg q.d.), celecoxib (200 mg b.i.d.), naproxen (500 mg b.i.d.) and placebo in a randomized, blinded, placebo-controlled study in young healthy volunteers (median age 25-30 years, each group n = 10). We assessed prostanoid metabolite excretion (PGE-M, TXB(2), 6-keto-PGF(1alpha), 11-dehydro-TXB(2), 2,3-dinor-TXB(2), and dinor-6-keto-PGF(1alpha)), the expression of platelet activation markers (CD62P, PAC-1, fibrinogen), platelet-leukocyte formation, the endogenous thrombin potential, platelet cAMP content and plasma thrombomodulin level.

RESULTS

Naproxen suppressed biosynthesis of PGE-M, prostacyclin metabolites and thromboxane metabolites and thrombomodulin levels. In contrast, both coxibs had an inhibitory effect only on PGE-M, 6-keto-PGF(1alpha), and on dinor-6-keto-PGF(1alpha), whereas TXB(2), 2,3-dinor-TXB(2) and 11-dehydro-TXB(2) excretion were unaffected. None of the coxibs exerted significant effects on the expression of platelet activation markers, cAMP generation, platelet-leukocyte formation, or on thrombomodulin plasma levels. Interestingly, platelet TXB(2) release during aggregation was enhanced after coxib treatment following arachidonic acid or collagen stimulation.

CONCLUSION

In young healthy volunteers coxibs inhibit systemic PGE(2) and PGI(2) synthesis. Platelet function and expression of platelet aggregation markers are not affected; however, coxibs can stimulate TXB(2) release from activated platelets. Combined decrease in vasodilatory PGE(2) and PGI(2) together with increased TXA(2) in proaggregatory conditions may contribute to coxib side effects.

Acetylbritannilactone Inhibits Neointimal Hyperplasia after Balloon Injury of Rat Artery by Suppressing Nuclear Factor-{kappa}B Activation

Based on our previous observations that 1-O-acetylbritannilactone (R)-4((3aS,4S,7aR)-4-hydroxy-6-methyl-3-methylene-2-oxo-2,3,3a,4,7,7a-hexahydrobenzofuran-5-yl)pentyl acetate (ABL) suppresses prostaglandin E(2) and nitric oxide synthesis in macrophages, the present study was designed to explore the effect of ABL on neointimal hyperplasia after balloon injury and its mechanism of action. In male Sprague-Dawley rats, 26 mg/kg ABL or polyglycol (control) was administered daily from 3 days before injury to 2 weeks after conventional balloon injury. ABL administration led to a significant reduction in neointimal formation (neointima to media ratio, 1.94 +/- 0.43 versus 0.84 +/- 0.29, P < 0.01) and proliferative activity of vascular smooth muscle cells after balloon injury in rats. Western blot analysis revealed that this is correlated to the inhibition of nuclear factor (NF)-kappaB activation and to the reduced expression of cyclooxygenase-2. Investigation of potential signaling pathways demonstrated that ABL inhibited NF-kappaB activation via the blockade of the inhibitor of NF-kappaB kinase-beta activation and the suppression of the degradation of the inhibitors of NF-kappaB-alpha. These findings suggest that ABL is a potential inhibitor of neointimal formation because it blocks injury-induced NF-kappaB activation and may have beneficial effects in reducing the risk of restenosis after angioplasty.

P-glycoprotein has differential effects on the disposition of statin acid and lactone forms in mdr1a/b knockout and wild-type mice

In the present study we examined the disposition of atorvastatin, lovastatin, and simvastatin in acid and lactone forms and pravastatin in acid form in multidrug-resistant gene (mdr1a/b) knockout (KO), and wild-type (WT) mice. Each statin was administered s.c. to mdr1a/b KO and WT mice at 3.0 mg/kg (n > or = 3 mice/time point). Blood, brain, and liver samples were harvested at 0, 0.5, 1.5, and 3 h postdose. Plasma and tissue concentrations of the acid and lactone (only the acid form was determined for pravastatin) were determined using a liquid chromatography-mass spectrometry method. Both lactone and acid were observed in plasma when lactones were administered, but only acids were detected when the acid forms were administered. The plasma and liver concentrations of acid or lactone were similar between the KO and WT mice. Two- to 23-fold higher concentrations were observed in liver than in plasma, suggesting potential uptake transporters involved. A significantly higher (p < 0.05) brain penetration in the KO compared with the WT mice was observed for lovastatin acid (but the brain/plasma ratio was low for both KO and WT mice) and lactone and simvastatin lactone but not for atorvastatin or pravastatin. The present results suggest that mouse P-glycoprotein does not affect the lactone-acid interconversion or liver-plasma distribution. Furthermore, P-glycoprotein plays a limited role in restricting the brain penetration of the acid forms of atorvastatin, pravastatin, simvastatin, lovastatin, and atorvastatin lactone but may limit the brain availability of the lactone forms of simvastatin and lovastatin.

Influence of OATP1B1 genotype on the pharmacokinetics of rosuvastatin in Koreans

This study was carried out to determine whether polymorphisms of organic anion-transporting polypeptide 1B1 (OATP1B1) have an effect on rosuvastatin pharmacokinetics in Koreans. Among 200 subjects genotyped for OATP1B1 c.388A>G, and c.521T>C, 30 subjects were selected for the rosuvastatin pharmacokinetic study. The area under the concentration-time curve for 0 to infinity (AUC(0-infinity)) of rosuvastatin for group 1 (*1a/*1a, *1a/*1b, *1b/*1b), group 2 (*1a/*15, *1b/*15), and group 3 (*15/*15) were 111+/-49.3, 126+/-45.2, and 191+/-31.0 ng h/ml, respectively, with significant differences among the three groups (P=0.0429) and between *15/*15 and the other groups (P=0.0181). The maximum plasma concentration (Cmax) also showed a significant difference between *15/*15 and the other groups (P=0.0181). There were no significant differences in rosuvastatin-lactone pharmacokinetics among the three groups. The pharmacokinetic exposure of rosuvastatin was higher in the OATP1B1*15/*15 subjects than the others, suggesting a potential association between the OATP1B1 genetic polymorphisms and altered rosuvastatin pharmacokinetics in Korean populations.

Ginkgo biloba and ovarian cancer prevention: Epidemiological and biological evidence

There is considerable interest in herbal therapies for cancer prevention but often with little scientific evidence to support their use. In this study, we examined epidemiological data regarding effects of commonly used herbal supplements on risk for ovarian cancer and sought supporting biological evidence. 4.2% of 721 controls compared to 1.6% of 668 cases regularly used Ginkgo biloba for an estimated relative risk (and 95% confidence interval) of 0.41 (0.20,0.84) (p=0.01); and the effect was most apparent in women with non-mucinous types of ovarian cancer, RR=0.33 (0.15,0.74) (p=0.007). In vitro experiments with normal and ovarian cancer cells showed that Ginkgo extract and its components, quercetin and ginkgolide A and B, have significant anti-proliferative effects ( approximately 40%) in serous ovarian cancer cells, but little effect in mucinous (RMUG-L) cells. For the ginkgolides, the inhibitory effect appeared to be cell cycle blockage at G0/G1 to S phase. This combined epidemiological and biological data provide supportive evidence for further studies of the chemopreventive or therapeutic effects of Ginkgo and ginkgolides on ovarian cancer.

Pharmacokinetics of the ginkgo B following intravenous administration of ginkgo B emulsion in rats

Ginkgo B (GB) is an extract from the leaves of Ginkgo biloba, used in the treatment of dementia, cerebral insufficiency or related cognitive decline. In this paper, the main features of the pharmacokinetics of GB emulsion in rats were reviewed and the binding rate of GB to rat plasma and human plasma protein were investigated meanwhile. The concentrations of GB in plasma, tissue, and excretion of rats after i.v. administration of GB were measured using HPLC-ESI-MS. The metabolite was qualitated by LC-MS/MS. Intravenously administered GB was eliminated in a biphasic manner with a prominent initial phase (half-life of 0.3 h) followed by a slower terminal phase (half-life of 1.5 h). After i.v. 4, 12 and 36 mg/kg GB emulsion, the pharmacokinetic parameters from a two compartment model analysis of plasma samples were AUC(0-tau) (microg x min/ml): 53.7, 165.5 and 649.7; CL (l/min/kg): 0.07, 0.07 and 0.05; V(C) (l/kg): 2.27, 3.27 and 2.76, respectively. Peak concentrations generally occurred at 10 min except brain and fat. Tissue concentration then declined by several-fold during 6 h although still present in most tissues at 6 h. Single intravenous dose was mainly excreted in the urine (40-50%), feces contained less than 30%. The binding rate to rat plasma was little higher than to human plasma, but the difference was negligible. Some metabolites were found in urine and bile through qualitative analysis on the urine and bile by LC-MS/MS.

Cinnabaramides A-G: analogues of lactacystin and salinosporamide from a terrestrial streptomycete

The cinnabaramides A-G (1-7) were isolated from a terrestrial strain of Streptomyces as potent and selective inhibitors of the human 20S proteasome. Their chemical and biological properties resemble those of salinosporamide A, a recently identified lead compound from an obligate marine actinomycete, which is currently under development as an anticancer agent. Cinnabaramides F and G (6, 7) combine essential structural features of salinosporamide A and lactacystin and show about equal potency in vitro, with IC50 values in the 1 nM range. The properties and phylogenetic position of the producer organism, the production and isolation of compounds 1-7, their structure elucidation by MS and NMR, and their biological activities are reported. Additionally, an X-ray crystal structure was obtained from cinnabaramide A (1).

Determination of atractylenolide II in rat plasma by reversed-phase high-performance liquid chromatography

A method for quantitative determination of atractylenolide II in rat plasma using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with UV spectrometry was established. From a variety of compounds and solvents tested, atractylenolide III was selected as the internal standard (IS) and ethyl acetate was found to be the best solvent for extracting atractylenolide II from plasma samples. RP-HPLC analysis of the extracts was performed on an analytical column (DIKMA ODS, 150 x 4.6 mm; i.d., 5 microm) equipped with a security guard pre-column system. There was good linearity over the range 0.05-5.0 microg/mL (r > 0.99). The recoveries were more than 90.0% in plasma, and the intra- and inter-day coefficients of variation were less than 10.0% in all cases. The limit of detection (LOD) was 0.025 microg/mL and the lower limit of quantification (LLOQ) was 0.05 microg/mL. The RP-HPLC method was applied to quantitate atractylenolide II in rat plasma within 24 h in a pharmacokinetics study where experimental rats received a single dose of atractylenolide II (60 mg/kg).

Quantitative LC/MS/MS method and pharmacokinetic studies of columbin, an anti-inflammation furanoditerpen isolated fromRadix Tinosporae

Columbin is an important component isolated from Radix Tinosporae. It has been demonstrated to possess many pharmacological activities, including anti-inflammation, antitumor and inhibition of enzyme activity in vivo. The purpose of the present study was to examine in vivo pharmacokinetics and bioavailability of columbin in rats using a high-performance liquid chromatography coupled with tandem mass spectrometry quantitative detection method. The columbin was extracted from rat plasma samples by methyl tert-butyl ether, evaporated and reconstituted in 100 microL methanol prior to analysis. The separation was performed using a Luna reversed-phase analytical column (5 microm, 100 x 2.0 mm) and an SB-C18 guard column (5 microm, 20 x 4.0 mm). The mobile phase was a mixture of methanol and water containing 25 mmoL/L NH(4)Ac (80:20, v/v). The method was validated within the concentration range of 5-5000 ng/mL, and the calibration curves were linear with correlation coefficients (r) >0.999. It was further applied to assess pharmacokinetics and oral bioavailability of columbin after i.v. and oral administration to rats. The oral bioavailability of columbin was only 3.18%, which indicated that columbin had poor absorption or underwent extensive first-pass metabolism.

Mechanism for Covalent Binding of Rofecoxib to Elastin of Rat Aorta

We have previously reported that oral administration of [(14)C]rofecoxib to rats resulted in the long retention of radioactivity by the aorta as a consequence of covalent binding to elastin. Treatment of rats with alpha-phenyl-alpha-propylbenzeneacetic acid 2-[diethylamino]-ethyl ester hydrochloride (SKF-525A), a cytochrome P450 inhibitor, significantly decreased the systemic exposure of 5-hydroxyrofecoxib, one of the main metabolites of rofecoxib, whereas there was no statistically significant change in the retention of radioactivity from [(14)C]rofecoxib in the aorta. On the other hand, the aortic retention of radioactivity closely correlated to the systemic exposure of unchanged rofecoxib in the dose range between 2 and 10 mg/kg. A covalent binding study of [(14)C]rofecoxib in vitro using rat aorta homogenate in the presence of d-penicillamine, hydralazine, beta-aminopropionitrile, and sodium borohydride suggested that the aldehyde group of allysine in elastin was relevant to the covalent binding. In a model reaction using benzaldehyde, rofecoxib but not 5-hydroxyrofecoxib reacted with the aldehyde group of benzaldehyde in a manner of condensation reaction under a physiological pH condition. A histopathological examination using an electron microscope demonstrated that multiple oral administration of rofecoxib to rats caused marked degradation of the elastic fiber system of the aorta. These results suggested that rofecoxib as such is reactive in vivo, undergoing a condensation reaction with allysine, thereby preventing the formation of cross-linkages in elastin, i.e., desmosine and isodesmosine, and causing the degradation of the elastic fibers.

Extent of renal effect of cyclo-oxygenase-2-selective inhibitors is pharmacokinetic dependent

Non-steroidal anti-inflammatory drugs (NSAIDs) cause renal side-effects. In the present study, we tested the hypothesis that the extent of the renal effects of cyclo-oxygenase (COX)-2-selective NSAIDs is linked to their pharmacokinetics. A single oral dose of rofecoxib (10 mg/kg), celecoxib (40 mg/kg), meloxicam (3 mg/kg) or placebo was administered to rats. Urinary excretion of electrolytes, a marker of renal effects, and plasma and kidney concentrations of NSAIDs were measured. Rofecoxib and celecoxib, but not meloxicam, significantly decreased urinary sodium and potassium excretion. There was a significant correlation between the area under the 24 h plasma concentration-time curve (AUC0-24) of rofecoxib and the change in sodium (r = -0.65; P < 0.02) and potassium (r = -0.82; P < 0.0006) excretion. The AUC0-24 of celecoxib was correlated with sodium (r = -0.80; P < 0.05) but not potassium excretion. The ratios of kidney to plasma drug concentrations were 1.72, 3.16 and 0.17 for rofecoxib, celecoxib and meloxicam, respectively. The renal effect of the COX-2-selective NSAIDs examined, marked by their ability to reduce the excretion of electrolytes, is influenced by systemic exposure to the drugs. The relatively higher distribution into the kidneys of rofecoxib and celecoxib compared with meloxicam suggests involvement of direct drug exposure in the kidneys in the adverse renal effect.

[Determination of acetylbritannilactone in inulicin and rat plasma by micellar electrokinetic capillary chromatography with on-line sweeping concentration technique]

A method was established for the determination of acetylbritannilactone (ABL) in inulicins and rat plasma by micellar electrokinetic capillary chromatography (MECC), in which on-line sweeping technique was applied to elevate the sensitivity of the detection. The column used was an uncoated fused silica capillary with a size of 57 cm (effective length of 50 cm) x 75 microm i.d. Electrode buffer was a 50 mmol/L borate buffer containing 50 mmol/L sodium lauryl sulfate (SDS) (pH 9.5). Sample buffer was a 10 mmol/L borate buffer (pH 9.5). Other conditions were as follows: separation voltage, 23 kV; detection wavelength, 195 nm; sample injection, 3.45 kPa (0.5 psi) x 5 s; column temperature, 25 degrees C. The on-line sweeping-MECC had excellent linearity with correlation coefficient of 0. 997 5, and reproducibility with the relative standard deviation of ABL migration time less than 5%. The recovery was more than 92%, and the sensitivity was 0.005 g/L. ABL in inulicin and their dynamic change in vivo were determined by sweeping-MECC. The results indicate that on-line sweeping-MECC is a simple and rapid method for the determination of trace biological sample. The method needs only micro-amount of samples, and is characterized by higher degree of automation and sensitivity.

Exposure of atorvastatin is unchanged but lactone and acid metabolites are increased several-fold in patients with atorvastatin-induced myopathy

BACKGROUND

The most serious side effect from statin treatment is myopathy, which may proceed to rhabdomyolysis. This is the first study to investigate whether the pharmacokinetics of either atorvastatin or its metabolites, or both, is altered in patients with atorvastatin-related myopathy compared with healthy controls.

METHODS

A 24-hour pharmacokinetic investigation was performed in 14 patients with atorvastatin-related myopathy. Relevant polymorphisms in SLCO1B1 (encoding organic anion transporting polypeptide 1B1), MDR1/ABCB1 (encoding P-glycoprotein), and CYP3A5 (encoding cytochrome P450 3A5) were determined. Data from 15 healthy volunteers were used as controls.

RESULTS

No statistically significant difference in systemic exposure of atorvastatin was observed between the 2 groups. However, patients with atorvastatin-related myopathy had 2.4-fold and 3.1-fold higher systemic exposures of the metabolites atorvastatin lactone (P<.01) and p-hydroxyatorvastatin (P<.01), respectively, compared with controls. There were no differences in frequencies of SLCO1B1, MDR1, and CYP3A5 polymorphisms between the 2 groups.

CONCLUSIONS

This study disclosed a distinct difference in the pharmacokinetics of atorvastatin metabolites between patients with atorvastatin-related myopathy and healthy control subjects. These results are of importance in the further search for the mechanism of statin-induced myopathy.

Racemic and chiral sulfoxides as potential prodrugs of the COX-2 inhibitors Vioxx® and Arcoxia®

The preparation of the sulfoxide analogues 2 and 4, and their enantiomeric pure forms is discussed as well as their potential to act as prodrugs to the potent and selective sulfone-containing COX-2 inhibitors rofecoxib and etoricoxib. Sulfoxides 2 and 4 were shown to be effectively transformed in vivo into rofecoxib and etoricoxib, respectively, after oral administration in rats. In the case of sulfoxide 2, both a slightly improved pharmacokinetic profile and a better pharmacological activity in an arthritis model were seen when compared with rofecoxib.

Pharmacological separation between peripheral and central functions of cyclooxygenase-2 with CIAA, a novel cyclooxygenase-2 inhibitor

There are many reports concerning the physiological and pathological involvement of cyclooxygenase (COX)-2 in the central nervous system and peripheral tissue cells. Selective COX-2 inhibitors that mainly distribute peripherally have not been reported thus far. Therefore central and peripheral roles of COX-2 remain classified pharmacologically. In this study, in vivo pharmacological profiles of CIAA ([6-chloro-2-(4-chlorobenzoyl)-1H-indol-3-yl]acetic acid), a novel selective COX-2 inhibitor which distributes at higher concentrations in plasma than in brain, were compared with those of well-known selective COX-2 inhibitors, celecoxib and rofecoxib. Additionally, the possibility of pharmacological separation between peripheral and central actions of COX-2 with the inhibitors was investigated. CIAA selectively inhibited COX-2 activity compared with COX-1 in in vitro assays with rat whole blood. The compound exhibited lower brain penetration and higher plasma concentration (the brain/plasma concentration ratio was approximately 0.02) than celecoxib and rofecoxib after oral administration. Therefore, CIAA is mainly expected to act peripherally. Edema and prostaglandin E2 (PGE2) production in Carrageenan-injected rat paws, and pyrexia and PGE2 production in the brain in lipopolysaccharide (LPS)-injected rats were measured in in vivo experiments. CIAA exhibited lower ratios of anti-pyretic/anti-edematous activities and of inhibitory activities of PGE2 production in brain/paw than those of celecoxib and rofecoxib, and these ratios well-reflected brain/plasma concentration ratios. In conclusion, we discovered a novel selective COX-2 inhibitor, CIAA, which distributes at higher concentrations in plasma than in brain, which would make possible the pharmacological separation of the peripheral and central functions of COX-2.

COVALENT BINDING OF RADIOACTIVITY FROM [14C]ROFECOXIB, BUT NOT [14C]CELECOXIB OR [14C]CS-706, TO THE ARTERIAL ELASTIN OF RATS

Rofecoxib is a cyclooxygenase-2 (COX-2) inhibitor that has been withdrawn from the market because of an increased risk of cardiovascular (CV) events. With a special focus on the arteries, the distribution profiles of radioactivity in rats orally administered [14C]rofecoxib were investigated in comparison with two other COX-2 inhibitors, [14C]celecoxib and [14C]CS-706 (2-(4-ethoxyphenyl)-4-methyl 1-(4-sulfamoylphenyl)-1H-pyrrole), a novel selective COX-2 inhibitor. Whole-body autoradioluminography and quantitative determination of the tissue concentrations showed that considerable radioactivity is retained by and accumulated in the thoracic aorta of rats after oral administration of [14C]rofecoxib, but not [14C]celecoxib or [14C]CS-706. Acid, organic solvent, and proteolytic enzyme treatments of aorta retaining high levels of radioactivity from [14C]rofecoxib demonstrated that most of the radioactivity is covalently bound to elastin. In agreement with this result, the radioactivity was found to be highly localized on the elastic fibers in the aorta by microautoradiography. The retention of radioactivity on the elastic fibers was also observed in the aortic arch and the coronary artery. These findings indicate that [14C]rofecoxib and/or its metabolite(s) are covalently bound to elastin in the arteries. These data are consistent with the suggestion of modified arterial elasticity leading to an increased risk of CV events after long-term treatment with rofecoxib.

Evaluation of the comparative efficacy and tolerability of rofecoxib and naproxen in children and adolescents with juvenile rheumatoid arthritis: a 12-week randomized controlled clinical trial with a 52-week open-label extension

OBJECTIVE

To compare the safety and efficacy of rofecoxib* to naproxen for the treatment of juvenile rheumatoid arthritis (JRA).

METHODS

This was a 12-week, multicenter, randomized, double-blind, double-dummy, active comparator-controlled, non-inferiority study with a prespecified 52-week open-label active comparator-controlled extension. Children (ages 2-11 yrs) and adolescents (ages 12-17 yrs) received lower-dose (LD)-rofecoxib [0.3 mg/kg/day up to 12.5 mg/day (base study only)]; or higher-dose (HD)-rofecoxib (0.6 mg/kg/day up to 25 mg/day) or naproxen 15 mg/kg/day as oral suspensions. Adolescents received daily rofecoxib (LD) 12.5 (base study only) or (HD) 25 mg, or naproxen 15 mg/kg/day (maximum 1,000 mg/day) as tablets. The primary endpoint was the time-weighted average proportion of patients meeting the American College of Rheumatology Pediatric-30 (ACR Pedi 30) response criteria. A prespecified bound for the 95% confidence interval for the ratio of the percentage of ACR Pedi 30 responders was used to assess non-inferiority of treatment response between groups. Safety was assessed throughout the study.

RESULTS

A total of 310 patients ages 2-17 years (181 (3/4) age 11) were randomized to receive LD-rofecoxib (N=109), HD-rofecoxib (N=100), or naproxen (N=101). The ACR Pedi 30 response rates following 12 weeks of treatment were 46.2%, 54.5%, and 55.1%, respectively. The relative rates of response compared to naproxen were 0.81 (95% CI 0.61, 1.07) and 0.98 (95% CI 0.76, 1.26) for LD- and HD-rofecoxib, respectively. Both rofecoxib doses were not inferior to naproxen. Patients (N=227) entering the extension received HD-rofecoxib or naproxen with efficacy maintained during the extension. All treatments were generally well tolerated throughout the study.

CONCLUSION

Daily treatment of JRA patients with rofecoxib up to 12.5 or 25 mg was well tolerated, providing sustained clinical effectiveness comparable to naproxen 15 mg/kg. *On September 30, 2004, Merck & Co., Inc. announced the voluntary worldwide withdrawal of rofecoxib from the market.

Rofecoxib Increases Susceptibility of Human LDL and Membrane Lipids to Oxidative Damage: A Mechanism of Cardiotoxicity

Clinical investigations have demonstrated a relationship between the extended use of rofecoxib and the increased risk for atherothrombotic events. This has led to the removal of rofecoxib from the market and concern over the cardiovascular safety of other cyclooxygenase (COX)-2 selective agents. Experimental findings from independent laboratories now indicate that the cardiotoxicity of rofecoxib may not be a class effect but because of its intrinsic chemical properties. Specifically, rofecoxib has been shown to increase the susceptibility of human low-density lipoprotein and cellular membrane lipids to oxidative modification, a contributing factor to plaque instability and thrombus formation. Independently of COX-2 inhibition, rofecoxib also promoted the nonenzymatic formation of isoprostanes and reactive aldehydes from biologic lipids. The basis for these observations is that rofecoxib alters lipid structure and readily forms a reactive maleic anhydride in the presence of oxygen. By contrast, other selective (celecoxib, valdecoxib) and nonselective (naproxen, diclofenac) inhibitors did not influence rates of low-density lipoprotein and membrane lipid oxidation. We have now further confirmed these findings by demonstrating that the prooxidant activity of rofecoxib can be blocked by the potent antioxidant astaxanthin in homochiral form (all-trans 3S, 3'S). These findings provide a mechanistic rationale for differences in cardiovascular risk among COX-selective inhibitors because of their intrinsic physicochemical properties.

Quantitative determination of atractylenolide III in rat plasma by liquid chromatography electrospray ionization mass spectrometry

Atractylenolide III is a major active component in Atractylodes macrocephala. This paper describes a simple, rapid, specific and sensitive method for the quantification of atractylenolide III in rat plasma using a liquid-liquid extraction procedure followed by liquid chromatography mass spectrometric (LC-MS) analysis. A Kromasil 3.5 microm C(18) column (150 mm x 2.00 mm) was used as the analytical column. Linear detection responses were obtained for atractylenolide III concentration ranging from 5 to 500 ng L(-1). The precision and accuracy data, based on intra-day and inter-day variations over 5 days were within 10.29%. The lower limit of quantitation for atractylenolide III was 5 ng mL(-1), using 0.1 mL plasma for extraction and its recoveries were greater than 85% at the low, medium and high concentrations. The method has been successfully applied to a pharmacokinetic study in rats after an oral administration of atractylenolide III with a dose of 20.0 mg kg(-1). With the lower limits of quantification at 5 ng mL(-1) for atractylenolide III, this method was proved to be sensitive enough for the pharmacokinetics study of atractylenolide III.

Influence of plasma protein on the potencies of inhibitors of cyclooxygenase-1 and -2

It is widely believed that the potencies of nonsteroid anti-inflammatory drugs (NSAIDs) as inhibitors of cyclooxygenase (COX) are influenced by protein binding in the extracellular fluid, since NSAIDs are bound to circulating albumin by well over 95%. This is an important point because the protein concentrations in synovial fluid and the central nervous system, which are sites of NSAID action, are markedly different from those in plasma. Here we have used a modified whole-blood assay to compare the potencies of aspirin, celecoxib, diclofenac, indomethacin, lumiracoxib, meloxicam, naproxen, rofecoxib, sodium salicylate, and SC560 as inhibitors of COX-1 and COX-2 in the presence of differing concentrations of protein. The potencies of diclofenac, naproxen, rofecoxib, and salicylate, but not aspirin, celecoxib, indomethacin, lumiracoxib, meloxicam, or SC560, against COX-1 (human platelets) increased as protein concentrations were reduced. Varying protein concentrations did not affect the potencies of any of the drugs against COX-2, with the exception of sodium salicylate (A549 cells). Clearly, our findings show that the selectivity of inhibitors for COX-1 and COX-2, which are taken to be linked to their efficacy and side effects, may change in different extracellular fluid conditions. In particular, selectivity in one body compartment does not demonstrate selectivity in another. Thus, whole-body safety or toxicity cannot be linked to one definitive measure of COX selectivity.

Sensitive and selective liquid chromatography–electrospray ionization mass spectrometry analysis of ginkgolide B in dog plasma

As an important active constituent of Ginkgo biloba extract, ginkoglide B is a highly selective and competitive PAF receptor antagonist which has been widely used in clinical applications. A novel high-performance liquid chromatography-electrospray ionization mass spectromentry (LC-ESI-MS) method was developed for the determination of ginkgolide B in dog plasma. After liquid/liquid extraction with ether and high-performance liquid chromatography (HPLC) gradient separation with 0.01% of ammonia water (v/v)-methanol as the mobile phase, the deprotonized anions [M-H](-1) at m/z 423 of ginkoglide B, and [M-H](-1) at m/z 492 of internal standard (IS) glibenclamide were analyzed by LC-ESI-MS in selected ion monitoring (SIM) mode. Chromatographic separation was achieved in less than 9 min and calibration curve was linear over a concentration range of 0.1-20 ng/ml. The described assay method was successfully applied to the pre-clinical pharmacokinetic study of ginkoglide B. After intragastric administration of ginkgolide B to beagle dogs, C(max) and T(max) of ginkgolide B were 43.8 +/- 6.24 ng/ml and 0.5 h, respectively, and the elimination half-life (t(1/2)) was 2.85 +/- 0.54 h.

LC-MS characterization of terpene lactones in plasma of experimental animals treated with Ginkgo biloba extracts Correlation with pharmacological activity

Liquid chromatography/atmospheric pressure chemical ionization ion trap mass spectrometry (LC/APCI-ITMS) was applied to determine the concentration of terpene lactone in plasma of guinea pigs after chronic administration of Ginkgo biloba extract enriched in ginkgoterpenes in free form (IDN 5380) or complexed with soy phosphlipids (IDN 5381). Oral treatment of the animals with ginkgoterpenes resulted to inhibit the bronchoconstriction (ITP) and the concomitant increase of the levels of thromboxane B2 (TXB2) in the circulation caused by histamine (HIST) and platelet activating factor (PAF) in normal guinea pigs or by ovalbumin (OA) in actively sensitized guinea pigs. To compare the protective activities of G. biloba forms (IDN 5380 and IDN 5381), ED50 and dose ratio (DR) values for both parameters (ITP and TXB2) were evaluated. The phytosomic form (IDN 5381) significantly reduced (two- to four-fold as compared to free form, P < 0.001) the HIST, PAF or OA-induced airway changes and TXB2 release. In addition it has been observed that the absence of ginkgolide C (GC) in plasma samples (in human and animals) was due to its rapid methylation.

[In vitro and in vivo stability of 9-nitrocamptothecin lactone form in rats]

AIM

To investigate the in vitro and in vivo stability of 9-nitrocamptothecin lactone form in rat plasma.

METHODS

The specific and accurate HPLC method was developed for quantifying 9-nitrocamptothecin lactone form and the total lactone and carboxylate forms simultaneously. By using of this method, the ratios of lactone form to the total in rat plasma at different time were determined in vitro and in vivo. The results were compared to determine which was the main factor influencing the stability of 9-nitrocamptothecin lactone form in rat plasma in vivo.

RESULTS

The stability of lactone form in rat plasma was much higher in vivo than that in vitro.

CONCLUSION

Blood cells help to increase the stability of 9-nitrocamptothecin lactone form. Clearance from blood in vivo is the primary factor which influences the plasma stability of 9-nitrocamptothecin lactone form. The kinetic process of 9-nitrocamptothecin lactone form and total drug in rats were both best fitted to a two-compartment model. However, the process of 9-nitrocamptothecin carboxylate form in vivo was best fitted to a one-compartment model.

Simultaneous Determination of Rofecoxib and Celecoxib in Human Plasma by High-Performance Liquid Chromatography

An innovative reversed-phase high-performance liquid chromatographic method is validated for the simultaneous determination of rofecoxib and celecoxib in human plasma. The internal standard is 4-n-pentyl-phenyl-acetic acid. Good chromatographic separation is achieved using a Zorbax SB-CN (5 microm) analytical column operated at room temperature and mobile phase consisting of acetonitrile and water containing 0.1M potassium dihydrogen orthophosphate buffer adjusted to pH 2.4 with 85% orthophosphoric acid (42:58, v/v). UV detection is performed at 254 nm, and the flow rate is maintained at 1.0 mL/min. Plasma samples are extracted into an organic solvent (1-chlorobutane) and evaporated under an air flow. The calibration curve for rofecoxib is linear over the range of 10 to 500 microg/L, and the celecoxib calibration curve is linear over the range of 20 to 2000 microg/L. The lower limit of quantitation for rofecoxib and celecoxib is 10 and 20 microg/L, respectively, using 1.0 mL of human plasma. The validation data show that the assay is sensitive, accurate, specific, and reproducible for the determination of rofecoxib and celecoxib. This method is therefore appropriate for pharmacokinetic studies to quantitate these therapeutic agents in patients with arthritis conditions.

Combining restricted access material (RAM) and turbulent flow for the rapid on-line extraction of the cyclooxygenase-2 inhibitor rofecoxib in plasma samples

Restricted access material (RAM) has been used in the packing of a solid-phase extraction (SPE) column for on-line extractions under turbulent flow conditions. The bio-compatible RAM material works by the principle of size exclusion in addition to conventional reversed-phase chromatography, thereby allowing the extraction and preconcentration of small analyte molecules from biological samples such as plasma. Using small column dimensions (0.76 mm x 50 mm) and a consequently high linear velocity, turbulent flow was achieved during online sample extractions. The improved mass-transfer rate characteristic of turbulent flow allows fast sample cleanup without decreased extraction efficiency. The novel use of the RAM column, connected upstream to a C18 monolithic column, allowed the direct injection, extraction, separation, and MS/MS detection of plasma samples spiked with rofecoxib in a span of 5 min. Calibration curves obtained using this RAM turbulent flow coupled column method showed good linearity (R2 > 0.99) and reproducibility (%RSD < or = 7%). The lower limit of quantitation of rofecoxib in plasma samples was found to be 40 ng/ml. The extraction method showed good recovery of rofecoxib from a plasma matrix with minimal signal loss and robustness after more than 200 plasma injections.