Aripiprazole augmentation of serotonin reuptake inhibitors in treatment-resistant obsessive-compulsive disorder: a 10-week open-label study

INTRODUCTION

Studies investigating the aripiprazole augmentation treatment of serotonin reuptake inhibitor (SRI)-resistant obsessive-compulsive disorder (OCD) are insufficient. The aim of the present pilot study was to investigate the efficacy and tolerability of flexible doses of aripiprazole as an augmenting agent in SRI-resistant OCD patients.

METHODS

OCD patients who met the criteria of this study were followed up with flexible doses of aripiprazole augmentation over a 10-week period. Effectiveness of treatment was evaluated via the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and Clinical Global Impressions-Severity of Illness (CGI-S) and -Improvement (CGI-I) scales. At the end of the 10-week follow-up period, patients who showed an improvement of ≥30% for the Y-BOCS total score from baseline were considered responders.

RESULTS

Thirty patients met the study inclusion criteria; three patients did not agree to participate, and four patients dropped out of the study. The differences between baseline and scores at 10 weeks for the parameters studied were as follows: Y-BOCS scores: 32.0±6.3-24.0±8.1 (Z=4.2, P<0.05); Y-BOCS compulsion subscore: 15.0±4.2-11.5±4.3 (Z=4.01, P<0.05); Y-BOCS obsession subscore: 17.0±2.6-12.4±4.0 (Z=4.1, P<0.05); and CGI-S scores: 4.8±0.8-3.1±1.2 (Z=3.9, P<0.05). Patients showed a significant improvement over the 10-week study period; however, only seven of 23 patients (30.4%) who completed the study met the criteria determined for treatment response.

CONCLUSION

Despite the limited number of cases and open-label design of this study, results support the notion that adding aripiprazole to SRIs could be a valid strategy for treatment-resistant OCD patients.

Laquinimod, a new oral autoimmune modulator for the treatment of relapsing-remitting multiple sclerosis

Laquinimod, a second-generation quinoline-3-carboxamide, is being developed by Active Biotech AB and Teva Pharmaceutical Industries Ltd for the treatment for relapsing-remitting multiple sclerosis (RRMS). Laquinimod has demonstrated significant activity in suppressing experimental autoimmune encephalomyelitis, an animal model of RRMS. In phase I and II clinical trials, the drug was well tolerated, with some hints of efficacy in small numbers of patients with RRMS. While the mechanism of action of the drug is unknown, it likely involves Th1 to Th2/Th3 immune deviation, promotion of the synthesis and release of neurotrophic factors, and other possible neuroprotective effects. Two phase III clinical trials are ongoing and, if successful, will lead to the approval of the first oral immunomodulatory drug for suppressing multiple sclerosis disease activity.

Multiple-dose safety, tolerability, and pharmacokinetics of oral nemonoxacin (TG-873870) in healthy volunteers

Nemonoxacin (TG-873870) is a novel nonfluorinated quinolone with broad-spectrum activities against Gram-positive and Gram-negative aerobic, anaerobic, and atypical pathogens, as well as against methicillin-resistant Staphylococcus aureus, vancomycin-resistant S. aureus, and multiple-resistant bacterial pathogens. We conducted a randomized, double-blind, placebo-controlled, dose-escalating study to ascertain the safety, tolerability, and pharmacokinetics of nemonoxacin. We enrolled 46 healthy volunteers and used a once-daily oral-dosing range of 75 to 1,000 mg for 10 days. Additionally, the food effect was evaluated in subjects in the 500-mg cohort. Nemonoxacin was generally safe and well tolerated, with no significant changes in the clinical laboratory tests or electrocardiograms. Adverse effects, including headache, contact dermatitis, and rash, were mild and resolved spontaneously. Nemonoxacin was rapidly absorbed within 2 h postdosing, and generally, a steady state was reached after 3 days. The maximum plasma concentration and the area under the plasma concentration-time curve were dose proportional over the dosing range. The elimination half-life was approximately 7.5 h and 19.7 h on days 1 and 10, respectively. Approximately 37 to 58% of the drug was excreted in the urine. Food affected the pharmacokinetics, with decreases in the maximum plasma concentration and area under the plasma concentration-time curve of 46% and 27%, respectively. However, the free AUC/MIC(90) of nemonoxacin was more than 100 under both the fasting and fed conditions, predicting the efficacy of nemonoxacin against most of the tested pathogens. In conclusion, the results support further clinical investigation of once-daily nemonoxacin administration for antibiotic-sensitive and antibiotic-resistant bacterial infections.

Dose escalation study of the safety, tolerability, and pharmacokinetics of nemonoxacin (TG-873870), a novel potent broad-spectrum nonfluorinated quinolone, in healthy volunteers

Nemonoxacin (TG-873870) is a novel nonfluorinated quinolone with potent broad-spectrum activity against Gram-positive and Gram-negative pathogens, including methicillin-resistant Staphylococcus aureus, penicillin- and quinolone-resistant Streptococcus pneumoniae, and vancomycin-intermediate and vancomycin-resistant Staphylococcus aureus. The safety, tolerability, and pharmacokinetics of nemonoxacin were investigated in a double-blind, ascending-single-dose study involving 56 healthy subjects (48 males and 8 females) who were randomly assigned to 1 of 7 dose cohorts. In each successive cohort, two subjects received a placebo and six received single oral doses of 25, 50, 125, 250, 500, 1,000, or 1,500 mg nemonoxacin. Nemonoxacin was well tolerated up to the maximum dose of 1,500 mg. No severe or serious adverse events were observed. The most frequent adverse events were contact dermatitis, pruritus, and erythema. No clinically significant abnormalities were noted in the electrocardiograms, vital signs, or laboratory tests. The plasma concentrations increased over the dose range, and at 500 mg, the free area under the plasma concentration-time curve/MIC(90) ratios and free maximum nemonoxacin concentration/MIC(90) ratios against drug-sensitive/drug-resistant S. pneumoniae and S. aureus were greater than 227 and 24, respectively. The peak time and elimination half-life of nemonoxacin were 1 to 2 h and 9 to 16 h, respectively. The oral clearance was approximately 0.22 liter/h/kg. The plasma protein binding was approximately 16%. The results of this study support further evaluation of the multiple-dose safety, tolerability, and pharmacokinetics of nemonoxacin.

Anticancer activity of CX-3543: a direct inhibitor of rRNA biogenesis

Hallmark deregulated signaling in cancer cells drives excessive ribosome biogenesis within the nucleolus, which elicits unbridled cell growth and proliferation. The rate-limiting step of ribosome biogenesis is synthesis of rRNA (building blocks of ribosomes) by RNA Polymerase I (Pol I). Numerous kinase pathways and products of proto-oncogenes can up-regulate Pol I, whereas tumor suppressor proteins can inhibit rRNA synthesis. In tumorigenesis, activating mutations in certain cancer-associated kinases and loss-of-function mutations in tumor suppressors lead to deregulated signaling that stimulates Pol I transcription with resultant increases in ribosome biogenesis, protein synthesis, cell growth, and proliferation. Certain anticancer therapeutics, such as cisplatin and 5-fluorouracil, reportedly exert, at least partially, their activity through disruption of ribosome biogenesis, yet many prime targets for anticancer drugs within the ribosome synthetic machinery of the nucleolus remain largely unexploited. Herein, we describe CX-3543, a small molecule nucleolus-targeting agent that selectively disrupts nucleolin/rDNA G-quadruplex complexes in the nucleolus, thereby inhibiting Pol I transcription and inducing apoptosis in cancer cells. CX-3543 is the first G-quadruplex interactive agent to enter human clinical trials, and it is currently under evaluation against carcinoid/neuroendocrine tumors in a phase II clinical trial.

[Antibacterial activity of quinolones against various clinically isolated strains and evaluation of efficacy based on the pharmacokinetics/pharmacodynamics theory]

We compared the antimicrobial activities of oral quinolones, ciprofloxacin (CPFX), gatifloxacin (GFLX), garenoxacin (GRNX), levofloxacin (LVFX), moxifloxacin (MFLX), norfloxacin (NFLX), prulifloxacin (PUFX), and tosufloxacin (TFLX) using Streptococcus pneumoniae, Haemophilus influenzae, Streptococcus agalactiae, Streptococcus pyogenes, extended spectrum beta-lactamase(ESBL) producing Klebsiella pneumoniae, and methicillin-susceptible Staphylococcus aureus (MSSA) isolated from clinical materials. Based on the pharmacokinetics-pharmacodynamics theory, the target attainment rate at the area under the curve (AUC)/MIC of 120 or more for Gram-negative and 30 or more for Gram-positive bacteria was calculated using Monte Carlo simulation (MCS), and was assessed as the efficacy. GRNX showed the lowest MIC50 and MIC90 values (0.03 and 0.06 microg/ml, respectively) against S. pneumoniae, suggesting its potent antimicrobial activity. GRNX also exhibited the most potent antimicrobial activity against Gram-positive bacteria (S. agalactiae, S. pyogenes, MSSA) other than S. pneumoniae. The antimicrobial activity of CPFX against H. influenzae was most potent. The MIC50 and MIC90 values were 0.016 microg/ml each. However, the MIC50 and MIC90 values of the other agents were also favorable. PUFX showed the most potent antimicrobial activity against ESBL-producing K. pneumoniae. Both of MIC50 and MIC90 values were 0.06 and 1 microg/ml, respectively. On efficacy assessment using MCS, GRNX, GFLX, and MFLX showed a probability of 90% or more against S. pneumoniae and S. pyogenes. Against S. agalactiae, GRNX, MFLX, and GFLX showed a probability of approximately 60%. All agents showed a low probability against ESBL-producing K. pneumoniae; PUFX showed a maximum (43.63%). GRNX, MFLX, GFLX, and LVFX showed a probability of 90% or more against MSSA. Furthermore, we investigated the probability that the target value of resistance inhibition, an AUC/MIC of more than 200 against S. pneumoniae, is achieved. GRNX showed the highest probability (95.05%). It also exhibited a similar probability even when the target value was established as 250. Recently, the widespread use of quinolones has increased the number of quinolone-resistant bacteria. In the future, antimicrobial agents should be selected with respect to more potent therapeutic effects and resistance inhibition, and an appropriate dose and administration method must be employed.

24-hour bronchodilator efficacy of single doses of indacaterol in subjects with COPD: comparison with placebo and formoterol

OBJECTIVE

To assess the bronchodilator efficacy, safety and tolerability of indacaterol, a novel, once-daily inhaled beta(2)-agonist bronchodilator, in patients with chronic obstructive pulmonary disease (COPD).

METHODS

This crossover, double-blind, double-dummy study was conducted to evaluate the 24-h bronchodilator effect of a range of single doses of indacaterol (150 microg, 300 microg and 600 microg), given in the morning via single-dose dry powder inhaler (SDDPI) in subjects with COPD, compared with placebo and with the daily therapeutic dose of formoterol (two 12 microg doses 12 h apart, via an SDDPI). Tolerability and safety were also assessed.

RESULTS

Fifty-one subjects with moderate-to-severe COPD received each of the five treatments on separate study days in randomised sequence. The 24-h trough FEV(1) (primary endpoint; mean [95% CI]) was 1.46 (1.43, 1.49) L with indacaterol 600 microg (p < 0.001 vs. placebo, p < 0.01 vs. formoterol, p < 0.05 vs. indacaterol 150 microg), 1.45 (1.42, 1.48) L with indacaterol 300 microg (p < 0.001 vs. placebo, p < 0.05 vs. formoterol), 1.42 (1.39, 1.45) L with indacaterol 150 microg (p < 0.001 vs. placebo), 1.41 (1.38, 1.43) L with formoterol (p < 0.001 vs. placebo) and 1.28 (1.25, 1.31) L with placebo. All treatments were well tolerated and there was little effect on serum potassium, blood glucose or QTc interval.

CONCLUSION

All doses of indacaterol were effective in providing 24-h bronchodilation and were well-tolerated in subjects with COPD. The bronchodilator efficacy of indacaterol (150, 300 and 600 microg) at 24 h post-dose was at least as efficacious as formoterol 12 microg twice daily.

Elvitegravir, an oral HIV integrase inhibitor, for the potential treatment of HIV infection

The treatment of HIV is often complicated by the emergence of antiretroviral (ARV) resistance, which has prompted the development of ARV drugs with novel mechanisms of action and resistance profiles. One of the newest classes of ARVs is the integrase inhibitors. These agents inhibit viral replication by preventing integration of viral DNA into the host cell. Japan Tobacco Inc and Gilead Sciences Inc are developing elvitegravir, a novel integrase inhibitor undergoing phase III clinical trials. Elvitegravir is predominantly metabolized via cytochrome P450 (CYP)3A4, along with minor pathways including glucuronidation via UGT1A1/3 and oxidative metabolism. Consequently, the coadministration of elvitegravir with the protease inhibitor ritonavir (a substantial CYP3A4 inhibitor) results in significantly enhanced bioavailability and a longer half-life than with elvitegravir alone, allowing for the once-daily dosing of elvitegravir. In vitro and clinical data suggest that elvitegravir has an overlapping resistance profile with raltegravir and with other integrase inhibitors that are in development. Data from phase I/II clinical trials have demonstrated excellent virological responses with elvitegravir, as well as minimal toxicities. At the time of publication, phase III trials to examine the efficacy and toxicity of elvitegravir were enrolling patients infected with HIV-1.

Transport of aripiprazole across Caco-2 monolayer model

This study aimed to investigate the transport characteristics of aripiprazole. A human intestinal epithelial cell model Caco-2 cell in vitro cultured had been applied to study the transport of aripiprazole. The effects of time, concentration of donor solutions, pH, temperature and P-glycoprotein inhibitor on the transport of aripiprazole were investigated. The determination of aripiprazole was performed by HPLC. It is concluded that aripiprazole is transported through the intestinal mucosa via a passive diffusion mechanism primarily, coexisting with a carrier-mediated transport. The transport of aripiprazole is positively correlated to transport time, pH, and temperature. Papp increased with donor concentrations up to 10 microg x mL(-1), and then decreased for higher concentrations. The P-glycoprotein inhibitor cyclosporine A significantly enhanced the transport amount of aripiprazole.

Novel oral absorption system containing polyamines and bile salts enhances drug transport via both transcellular and paracellular pathways across Caco-2 cell monolayers

The combinatorial use of spermine (SPM), a typical polyamine, and sodium taurocholate (STC), a typical bile salt, was found to be a promising safe preparation for improving the oral absorption of poorly water-soluble and/or poorly absorbable drug in our previous studies utilizing rats and dogs. To clarify the mechanisms behind the synergistic enhancement effect of the polyamine and bile salt, the transport of rebamipide, which is classified into Biopharmaceutics Classification System Class IV, was investigated in Caco-2 cell monolayers. The synergistic enhancement of rebamipide transport by SPM and STC was certainly observed in Caco-2 cells as well, while the separate use of either SPM or STC did not significantly improve the transport of rebamipide. The combinatorial use of SPM and STC significantly decreased the transepithelial electrical resistance (TEER) in Caco-2 cell monolayers, suggesting that the opening of paracellular pathway. On the other hand, it was also confirmed that the decrease in TEER was transient and reversible after removal of SPM and STC and that cell viability was maintained. Voltage-clamp study clearly showed that their combinatorial use improved rebamipide transport via both paracellular and transcellular pathways, and that the contribution of transcellular route could be larger than paracellular route.

A dose-ranging study of indacaterol in obstructive airways disease, with a tiotropium comparison

This dose-ranging study assessed the bronchodilator efficacy and tolerability of indacaterol, a novel once-daily inhaled beta2-agonist, in subjects clinically diagnosed with COPD. Comparative data with tiotropium were collected. In the double-blind, core period of the study, 635 subjects with COPD (prebronchodilator FEV(1)40% of predicted and > or =1.0L; FEV1/FVC <70%) were randomized to receive indacaterol 50, 100, 200 or 400microg or placebo via multi-dose dry powder inhaler, or indacaterol 400microg via single-dose dry powder inhaler, once daily for 7 days. After completing double-blind treatment and washout, a subset of subjects from each treatment group entered an open-label extension and received tiotropium 18microg once daily for 8 days. The primary efficacy variable was the trough bronchodilator effect: standardized area under the FEV1 curve between 22 and 24h post-dose (FEV1 AUC(22-24h)) on Day 1. Clinically relevant improvements versus placebo in FEV1 AUC(22-24h) were seen for 400 and 200microg doses on Day 1 and all doses on Day 7. All indacaterol doses significantly (P<0.05) increased FEV1 from 5min to 24h post-dose; the 400 and 200microg doses were most effective. All doses were well tolerated. Indacaterol trough FEV1 levels compared favorably with the improvement seen by Day 8 in subjects treated with tiotropium in the open-label extension. The results confirm that indacaterol has a 24-h duration of bronchodilator effect and a fast onset of action in COPD and suggest that indacaterol could be an effective once-daily inhaled beta2-agonist bronchodilator. Indacaterol demonstrated a good overall safety and tolerability profile.

[Permeabilities of rebamipide via different intestinal mucosa in the diffusion chamber in vitro]

The objective of this study is to investigate the permeabilities of rebamipide across the jejunal, ileal and colonic membranes in rat. The permeability (Papp) of rebamipide via rat intestinal membranes at concentration of 80 micromol L(-1) was evaluated by an in vitro diffusion chamber system after the membranes were isolated from the rat intestine. And the concentration of rebamipide in the receptor was determined by HPLC. As a result, the permeability of rebamipide across the jejunal or ileal membrane was higher than that across the colonic membrane, and the permeability of rebamipide in the ileal tissue from the serosal to mucosal direction was greater than that from the mucosal to serosal direction. Therefore, there was a regional difference in the permeability of rabamipide across the jejunum, ileum and the colon in rat. Also, the transporters in the intestinal mucosa as p-glycoprotein may not be involved in the transport of rebamipide.

Pharmacokinetics of elvitegravir and etravirine following coadministration of ritonavir-boosted elvitegravir and etravirine

BACKGROUND

This crossover, open-label clinical study evaluated the potential for clinically relevant drug interactions between ritonavir-boosted elvitegravir (elvitegravir/r), an HIV integrase inhibitor, and etravirine, a non-nucleoside reverse transcriptase inhibitor.

METHODS

Healthy volunteers were randomized into one of two groups, each with two arms. Group 1 (n = 20) followed a sequence of 10-day dosing of elvitegravir/r (150/100 mg once daily) and elvitegravir/r plus etravirine (200 mg twice daily) or the reverse (n = 10 per sequence). Group 2 (n = 14) followed a sequence of 10-day dosing of etravirine and etravirine plus elvitegravir/r or the reverse (n = 7 per sequence), all under fed conditions. Elvitegravir, ritonavir and etravirine pharmacokinetics were determined on days 10 and 20 using non-compartmental analyses. Lack of pharmacokinetic alteration bounds for 90% confidence intervals (CI) about the geometric mean ratio (GMR; coadministration versus alone) were 70-143% for elvitegravir and ritonavir pharmacokinetics (maximum concentration [C(max)], concentration at the end of the dosing interval [C(tau)] and area under the plasma concentration-time curve [AUC(tau); 0-24 h] and 80-125% for etravirine pharmacokinetics (AUC(tau) 0-12 h).

RESULTS

Of the 34 enrolled participants, 31 completed the study. There were three discontinuations, but none were caused by adverse events (AEs). The most common treatment-emergent AE was headache. Elvitegravir pharmacokinetic GMR was 6-7% higher following elvitegravir/r plus etravirine dosing versus elvitegravir/r. The GMR for etravirine and ritonavir AUC(tau) were 2.4% and 12.3% lower, respectively. Importantly, the 90% CI for elvitegravir and etravirine pharmacokinetics and AUC(tau) and C(max) for ritonavir were within the lack of alteration bounds.

CONCLUSIONS

Elvitegravir/r and etravirine do not undergo clinically relevant drug interactions and can be coadministered without dose adjustment.

Validation of a simple HPLC method for assay of haplamine and its metabolites in plasma suitable for pharmacokinetic application in rats

A simple HPLC method with ultraviolet detection has been developed and validated for the simultaneous determination of haplamine and its metabolites (trans/cis-3,4-dihydroxyhaplamine) in rat. A liquid-liquid extraction was used to extract the compounds from rat plasma. The analysis was performed on a C(18) Nucleosil Nautilus column. The mobile phase consisted of water (A) and a mixture of methanol and acetonitrile (85:15; v/v) (B) used in gradient mode (38-40% B for 10 min, 40-58% B for 49 min, 58-38% B for 1 min, and 38% for 5 min) pumped at 1 mL/min. The calibration curves showed good linearity with correlation coefficients greater than 0.999 for the analytes in the investigated concentration range. The lower limit of detection was 0.007, 0.008 and 0.009 microg/mL and the lower limit of quantification was 0.014, 0.017 and 0.018 microg/mL for haplamine, and trans/cis-3,4-dihydroxyhaplamine, respectively. The method was applied to a preliminary pharmacokinetic study in rats. This method proved to meet fully the standards required of experimental pharmacokinetic studies and should be used in further preclinical investigation.

Pharmacokinetics of coadministered ritonavir-boosted elvitegravir and zidovudine, didanosine, stavudine, or abacavir

OBJECTIVE

To evaluate the potential for clinically relevant drug interactions between ritonavir-boosted elvitegravir (EVG/r) and the nucleoside reverse transcriptase inhibitors (NRTIs) zidovudine (ZDV), didanosine (ddI), stavudine (d4T), or abacavir (ABC) upon coadministration.

METHODS

In 3 studies, healthy subjects were administered a single dose of ddI, d4T, or ABC, or multiple doses of ZDV, followed by multiple doses of EVG/r alone and together with an NRTI; pharmacokinetics (PK) of EVG and NRTIs were evaluated after individual administration and coadministration. Lack of PK alteration bounds (90% confidence intervals [CI]) for the NRTIs were based on the lack of PK-based dose adjustments per prescribing information.

RESULTS

Twenty-four of 28, 32/32, and 24/26 subjects completed the ZDV-EVG/r, ddI/d4T-EVG/r, and ABC-EVG/r studies, respectively. All study drugs were well tolerated and no serious adverse events were noted. The PK of ZDV, its glucuronide (G-ZDV), d4T, ABC, and EVG were within the lack of PK alteration 90% CI bounds upon coadministration. Exposures of ddI were modestly (approximately 15%) lower, but these changes are unlikely to be clinically meaningful.

CONCLUSIONS

There are no clinically relevant drug interactions between EVG/r and the NRTIs zidovudine, didanosine, stavudine, or abacavir. These agents can be coadministered without dose adjustment.

Substituted 6-(1-Pyrrolidine)quinolin-2(1H)-ones as Novel Selective Androgen Receptor Modulators

The androgen receptor is a ligand inducible transcription factor that is involved in a broad range of physiological functions. Here we describe the discovery of a new class of orally available selective androgen receptor modulators. The lead compound, 6-[(2R,5R)-2-methyl-5-((R)-2,2,2-trifluoro-1-hydroxyethyl)pyrrolidin-1-yl]-4-trifluoromethylquinolin-2(1H)-one (6a), showed excellent anabolic activity in muscle with reduced effect on the prostate in a rat model of hypogonadism. The compound also improved bone strength in a rat model of post-menopausal osteoporosis.

Allometric scaling of marbofloxacin, moxifloxacin, danofloxacin and difloxacin pharmacokinetics: a retrospective analysis

The purpose of this study was to examine the allometric analyses of marbofloxacin, moxifloxacin, danofloxacin and difloxacin using pharmacokinetic data from the literature. The parameters of interest (half-life, clearance and volume of distribution) were correlated across species as a function of body weight using an allometric approach (Y = aWb). Results of the allometric analysis indicated similarity between clearance and volume of distribution as they relate to body weight for all drugs. The elimination half-life was independent of body mass for all fluoroquinolones except moxifloxacin. Results of the analysis suggest that allometric scaling can be used as a tool for predicting pharmacokinetic parameters for fluoroquinolones.

Pharmacokinetics of emtricitabine, tenofovir, and GS-9137 following coadministration of emtricitabine/tenofovir disoproxil fumarate and ritonavir-boosted GS-9137

OBJECTIVES

To evaluate the potential for clinically relevant drug-drug interaction between emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) and the ritonavir-boosted HIV integrase inhibitor GS-9137 (GS-9137/r).

METHODS

Healthy adults were administered FTC/TDF (200/300 mg once daily) for 7 days, followed by randomization to the order of receiving GS-9137/r (50/100 mg once daily) and GS-9137/r plus FTC/TDF in a crossover fashion under fed conditions for 10 days. Pharmacokinetic (PK) blood draws were performed on days 7, 17, and 27. Lack of PK alteration for FTC, tenofovir (TFV), and GS-9137 was defined as a 90% confidence interval (CI) for the estimated ratio of geometric least squares means (coadministration/alone) between 70% and 143% for the primary PK parameters: maximum observed plasma concentration (Cmax), area under the plasma concentration-time curve over dosing interval (AUCtau), and trough concentration (Ctau).

RESULTS

Twenty-four of the 26 enrolled subjects completed the study with no serious adverse events or discontinuations attributable to adverse events. FTC, TFV, and GS-9137 PKs were unaffected during coadministration, with Cmax, AUCtau, and Ctau, meeting the protocol definition of equivalence and also the stricter bioequivalence criteria (90% CI: 80% to 125%). FTC and TFV PK parameters were comparable to historical values.

CONCLUSION

There is no clinically relevant drug-drug interaction between FTC/TDF and GS-9137/r on their coadministration.

Pharmacology and antitumor activity of a quinolinedione Cdc25 phosphatase inhibitor DA3003-1 (NSC 663284)

Cdc25 protein phosphatases are regulators of cyclin-dependent kinases and are often highly expressed in human malignancies. Few small molecule inhibitors of the Cdc25 phosphatase family have been identified and little is known about their disposition, metabolism or efficacy in xenograft models. In this study, the efficacy, pharmacokinetics, and metabolism of a potent quinolinedione Cdc25 phosphatase inhibitor, DA3003-1, in mice was examined. DA3003-1 inhibited the growth of subcutaneous human colon HT29 xenografts in SCID mice. After a single i.v. dose of 5 mg/kg, DA3003-1 was not detectable in plasma or tissues beyond 5 min. In vitro studies showed that DA3003-1 was rapidly dechlorinated and conjugated to glutathione. Following DA3003-1 treatment of tumor-bearing SCID mice, reduced glutathione concentrations in HT29 tumor were decreased to a greater extent and remained decreased for longer than the reduced glutathione concentrations in liver and kidneys. These studies suggest that the minimal antitumor activity of DA3003-1 in mice may be due to its rapid metabolism.

Influence of inoculum size on the selection of resistant mutants of Escherichia coli in relation to mutant prevention concentrations of marbofloxacin

We demonstrate using an in vitro pharmacodynamic model that the likelihood of selection of Escherichia coli mutants resistant to a fluoroquinolone was increased when the initial size of the bacterial population, exposed to fluoroquinolone concentrations within the mutant selection window, was increased.

Pharmacokinetics of a single intravenous dose of marbofloxacin in adult donkeys

Six donkeys each received 2 mg/kg marbofloxacin as a 10 per cent aqueous solution administered intravenously. Principal pharmacokinetic parameters were determined and two efficacy indices were computed by using pharmacokinetic parameters and selected mic90 values of marbofloxacin against pathogenic equine strains to predict the efficacy of the drug at this dose. The pharmacokinetics of marbofloxacin in donkeys was characterised by a large mean volume of distribution at a steady state (1.15 [0.09] l/kg) and a long mean (sd) elimination half-life of 9.24 (1.96) hours. It was also characterised by a relatively slow total body clearance of 0.10 (0.02) l/kg/hour, slower than in horses. Using mic90 values of marbofloxacin against pathogenic equine strains with a daily dose of 2 mg/kg, appropriate values of efficacy indicators were obtained only for Enterobacteriaceae. Daily intravenous doses of 0.33, 2.62 and 20 mg/kg were calculated for evaluation in clinical trials of infections due to Enterobacteriaceae, Staphylococcus aureus and Streptococci, respectively.

Safety and tolerability of indacaterol in asthma: a randomized, placebo-controlled 28-day study

The safety and tolerability of indacaterol, a novel once-daily beta(2)-agonist bronchodilator with a fast onset of action, were assessed in 156 asthma patients in a multicentre, randomized, double-blind, placebo-controlled study. Patients received indacaterol 200, 400 or 600 microg or placebo once daily for 28 days. Adverse events (AEs), laboratory assessments, vital signs, electrocardiograms, spirometry and physical examinations were monitored. Indacaterol pharmacokinetics were assessed. There was no evidence of dose-related increases in AE incidence or clinically significant hypokalaemia or hyperglycaemia in indacaterol-treated patients. Mean pulse rate changes were minor in any group, with maximum 1-h post-dose changes from baseline of -3.7, -3.3 and -2.2 bpm for indacaterol 200, 400 and 600 microg, respectively, and -2.9 bpm for placebo. Mean QTc interval was similar between groups; change from baseline >60 ms occurred in only two patients. Mean FEV(1) increased after the first indacaterol dose; baseline-adjusted pre-dose (trough) values remained >or=166 mL higher than placebo at all subsequent visits, supporting a 24-h bronchodilator effect. Pre-dose (but not post-dose) serum indacaterol concentrations indicated a slight trend for accumulation. Once-daily indacaterol 200-600 microg has a favourable therapeutic index. It is well tolerated, and is not associated with any adverse cardiac or metabolic effects, while providing effective 24-h bronchodilation.

Identification and comparison of marbofloxacin metabolites from the plasma of ball pythons (Python regius) and blue and gold macaws (Ara ararauna)

Marbofloxacin is a veterinary only, synthetic, broad spectrum fluoroquinolone antimicrobial agent. In mammals, approximately 40% of the oral dose of marbofloxacin is excreted unchanged in the urine; the remaining is excreted via the bile as unchanged drug in the feces. The Vd ranges from 1.1 (cattle) to 1.3 (dog, goat, swine) L/kg. Because of extra-label use of marbofloxacin in birds and reptiles, this study was designed to determine the profile of metabolites in plasma and compare the circulating metabolite profile between a reptile and an avian species. Six adult ball pythons (Python regius) and 10 blue and gold macaws (Ara ararauna) were used in this study. The macaws were dosed both i.v. and p.o. with a single 2.5 mg/kg administration where as the pythons received a single 10 mg/kg dose both i.v. and p.o. The metabolite profiles of marbofloxacin in the plasma of these species were determined using a high performance liquid chromatography system with a mass spectrometer for detection (LC/MS/MS). Mass spectra data generated from the snake and bird plasma samples were compared with previously reported LC/MS/MS mass spectral data. Evidence does not suggest differences due to route of administration (i.v. vs. p.o.) in either species. Four chromatographic peaks with resulting daughter spectrum were identified and represent 12 possible metabolite structures. All of the proposed metabolites, except for the N-oxide, appear to be unique to macaws. The potential metabolites identified in macaws appear to be very different than those reported for chickens.

Pharmacokinetics of aripiprazole and concomitant carbamazepine

The objective of this study was to assess the pharmacokinetics of aripiprazole when coadministered with carbamazepine using an open-label sequential treatment design in patients with schizophrenia or schizoaffective disorder. Nine male patients were enrolled and received aripiprazole monotherapy (30 mg once daily) for 14 days, after which aripiprazole steady-state pharmacokinetics were assessed. Subjects were then administered carbamazepine together with aripiprazole for 4 to 6 weeks. The dose of carbamazepine was titrated to produce a trough serum concentration within the range of 8 to 12 mg/L. Aripiprazole pharmacokinetics were then assessed in the presence of carbamazepine. Six patients completed the study as designed. Coadministration with carbamazepine decreased the values of mean peak plasma concentration and area under the plasma concentration-time curve of aripiprazole by 66% and 71%, respectively (P = 0.001 and 0.002, respectively). Similarly, coadministration with carbamazepine decreased the values of mean peak plasma concentration and area under the plasma concentration-time curve over the 24-hour dosing interval of the major active metabolite of aripiprazole, dehydroaripiprazole, by 68% and 69%, respectively (P < 0.001). Both aripiprazole and dehydroaripiprazole are substrates for the cytochrome P-450 3A4 enzyme which is known to be induced by carbamazepine dosed to steady state. Thus, therapeutic doses of carbamazepine had significant effects on the pharmacokinetics of aripiprazole in patients with schizophrenia or schizoaffective disorder. When carbamazepine is added to aripiprazole therapy, aripiprazole dose should be doubled (to 20-30 mg/d). Additional dose increases should be based on clinical evaluation. When carbamazepine is withdrawn from combination therapy, aripiprazole dose should then be reduced.

Single-dose pharmacokinetics of marbofloxacin in Egyptian buffalo (Bubalus bubalis L.) steers

The objective of this study was to investigate the pharmacokinetics of marbofloxacin (MAR) following intravenous (iv) and intramuscular (im) administration of a 2.0 mg/kg body weight dosage to five healthy Egyptian buffalo steers. A cross-over design was used with a washout period of 2 weeks. Blood samples were obtained at 0, 5,10,15, and 20 min and at 0.5,0.75,1,2,4,6,8,10,12,24,30 and 48 hours after marbofloxacin administration. The serum marbofloxacin concentrations were quantitated using a modified agar diffusion bioassay method. Marbofloxacin exhibited a relatively high volume of distribution at steady-state (Vdss = 1.77 Lkg), which suggests good tissue penetration, and a total body clearance (Cltot) of 0.18 L/kgxh,which is associated with a long elimination half-life (tl/2beta = 7.52 h). Marbofloxacin was rapidly absorbed at a dosage of 2.0 mg/kg after im administration with an observed maximum serum concentration (Cmax) value of 2.004 microg/mL obtained at a time to peak concentration (tmax) of 0.5 h, and an absolute bioavailability (F %) of 86.79 +/- 5.53 %. The protein-binding ranged from 22 to 24.6 % with an average of 23.4 %. In conclusion, single iv and im administered doses of marbofloxacin were well tolerated by Egyptian buffalo steers. A dosage of 2 mg/kg body weight might not be enough to treat infections caused by bacteria with minimum inhibitory concentration (MIC) at or above 0.2 microg/mL, based on the calculated area under the inhibitory concentration (AUIC).

Effects of Comedication on the Serum Levels of Aripiprazole: Evidence from a Routine Therapeutic Drug Monitoring Service

INTRODUCTION

The objective of the study was to compare the serum concentrations of the atypical antipsychotic aripiprazole in monotherapy with the concentrations found during concomitant therapy with other drugs.

METHODS

Samples analyzed for aripiprazole by a liquid chromatography-mass spectrometry method in a routine therapeutic drug monitoring setting were collected consecutively.

RESULTS

Samples from 81 patients were included in the study. Comedication with the CYP3A4 inducer carbamazepine lowered the dose-adjusted aripiprazole concentration by 88%. Comedication with CYP2D6 inhibitors gave a mean concentration 44% higher than in the monotherapy group. Subjects comedicated with valproate had lower aripiprazole concentrations, while subjects comedicated with lamotrigine, citalopram/escitalopram and lithium had higher concentrations than the subjects in the monotherapy group.

CONCLUSION

Although the study is small and the results should be interpreted very cautiously, it indicates that comedication with drugs inhibiting or inducing CYP2D6 or CYP3A4 affects the serum concentrations of aripiprazole. The other findings should be considered as preliminary and have to be replicated in a larger setting before firm conclusions can be drawn.

A phase I clinical and pharmacokinetic study of tipifarnib in combination with docetaxel in patients with advanced solid malignancies

PURPOSE

This phase I study assessed the maximum tolerated doses (MTDs), safety, pharmacokinetics, and efficacy of combined tipifarnib and docetaxel treatment in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

The study protocol was sensitive to myelosuppression, as both drugs have been associated with this adverse event. Due to myelosuppression incidence, and in order to determine the MTD of docetaxel, multiple treatment regimens were employed. Tipifarnib was administered orally at 200 or 300 mg, twice daily (BID) for 21 days, 14 days, or 7 days for multiple 21-day cycles; intravenous (i.v.) docetaxel was administered on day 1 of each cycle at 60, 75, or 85 mg/m2.

RESULTS

A total of 36 patients entered into the study. For each drug, MTDs were identified (tipifarnib: 300 mg BID for 14 days with 60 mg/m2 docetaxel; tipifarnib: 200 mg BID for 14 days with 75 mg/m2 docetaxel). The major dose-limiting toxicity was myelosuppression, particularly febrile neutropenia (44%). Mutual pharmacokinetic interactions (the effect of docetaxel on tipifarnib pharmacokinetics and the effect of tipifarnib on docetaxel pharmacokinetics) were not evident, as maximum plasma concentration (Cmax) and the area under the serum concentration-time curve (AUC) values of both tipifarnib and docetaxel were similar (p > or = 0.43) whether the two drugs were concomitantly administered or not. Seven of 31 evaluable patients (23%) had an objective response, 11 (35%) had stable disease (six > or = 24 weeks), and the overall clinical benefit rate (objective response and/or stable disease > or = 24 weeks) was 42%.

CONCLUSIONS

Although the high incidence of febrile neutropenia necessitated a multiple scheduling adaptation of tipifarnib compared to the original protocol, the apparent lack of mutual pharmacokinetic interactions, the ability to coadminister tipifarnib and docetaxel near single-agent MTDs, and suggestive evidence of efficacy make this drug combination attractive for further examination.

Comparison between immobilized artificial membrane (IAM) HPLC data and lipophilicity in n-octanol for quinolone antibacterial agents

The membrane phospholipid affinity of ten quinolone antibacterial agents, including both acidic and zwitterionic compounds, was measured by HPLC on two different immobilized artificial membrane (IAM) stationary phases, namely IAM.PC.MG and IAM.PC.DD2; it is expressed as the logarithm of the retention factor measured with (or extrapolated to) 100% aqueous eluent at pH 7.0, logk(w)(IAM). Quinolones are a class of highly potent, orally active, broad-spectrum antibacterial agents. For these compounds, lipophilicity values in n-octanol found in the literature, either calculated or measured, are not consistent with each other and are too low to be compatible with their pharmacokinetic properties. The logk(w)(IAM) values obtained in this study showed no relation with any of the lipophilicity values in the literature (clogP(a), clogP(b), MLP, logD(7.4)). In contrast, they were collinear with a new lipophilicity scale we had previously obtained by an original ion-pair reversed-phase HPLC method set up to estimate the lipophilicity of the neutral forms, logP(N). Moreover, when comparing the retention of quinolones on IAM to the retention of structurally unrelated neutral compounds, we observed that they interact with phospholipids with the same affinity as neutral isolipophilic compounds. The use of an eluent at pH 5.5, instead of pH 7.0, increased the retention on IAM not only for acidic, but also for zwitterionic congeners, indicating that phospholipid affinity is enhanced in the experimental conditions that depress the ionization of the acidic function, even when the ionization of the amino function increases simultaneously. To gain an insight into the mechanism of quinolones/serum-protein interactions, we investigated about possible relationships between quinolones affinity data for serum proteins and IAM data. Quinolone affinity for both HSA and AGP was already demonstrated poorly related to n-octanol lipophilicity values, probably due to the occurrence of electrostatic interactions. Only poor relationships were found between IAM and HSA affinity data, whereas quite good relationships were found with AGP affinity data. However, IAM.PC.DD2 data correlated better than those on IAM.PC.MG with quinolone affinity for both serum-proteins, mainly due to the fact that IAM.PC.MG phase is scarcely discriminative for the compounds with the highest retention values. The results suggest that IAM retention can produce a lipophilicity scale that, unlike solvent/water partition coefficients, is consistent with the pharmacokinetic behaviour of zwitterionic quinolones.

Population pharmacokinetics of tipifarnib in healthy subjects and adult cancer patients

AIMS

To characterize the population pharmacokinetics of tipifarnib.

METHODS

A total of 1083 subjects treated orally with a solution, capsule or tablet formulations of tipifarnib, given as a single dose or as multiple twice-daily doses (range 25-1300 mg) were combined with data from 1, 2 and 24 h intravenous infusions. A total of 3445 concentrations in the index data set were fitted by an open three-compartment linear disposition model with sequential zero-order input into the depot compartment, followed by a first-order absorption process, and lag time, using NONMEM V. The effect of patient covariates on tipifarnib pharmacokinetics was explored. The model was evaluated using goodness of fit plots and relative error measurements for 3894 concentrations in the test data set. Computer simulations were undertaken to evaluate the effect of covariates on tipifarnib pharmacokinetics.

RESULTS

Tipifarnib oral bioavailability (26.7%) did not differ between the formulations. The absorption rate from the solution was faster than from the solid forms. Whereas the absorption rate and systemic clearance were more rapid in healthy subjects, the extent of absorption and the steady-state volume of distribution were comparable in cancer patients and healthy subjects. Systemic clearance in cancer patients (21.9 l h-1) exhibited a statistically significant relationship with total bilirubin. The typical volume of the central compartment in cancer patients (54.6 l 70 kg-1) was directly proportional to body weight. The clinical relevance of these covariates in cancer patients is questionable as there was a substantial overlap in simulated concentration-time profiles across a wide range of covariate values.

CONCLUSIONS

A population PK approach has been used to integrate data gathered during clinical development and to characterize the pharmacokinetics of tipifarnib. Individualization of dose based on body weight or total bilirubin concentration in adult cancer patients is not warranted.

Preliminary single-dose pharmacokinetics of marbofloxacin in ball pythons (Python regius)

Pharmacokinetics of marbofloxacin in two male and four female adult ball pythons (Python regius) was determined after i.v. and p.o. administration of a single dose. Using a crossover design, each snake was given a single 10 mg/kg dose of marbofloxacin i.v. and p.o. Blood samples were collected prior to and 0.5, 1, 1.5, 3, 6, 12, and 24 hr after marbofloxacin administration. Marbofloxacin was quantitated by use of liquid chromatography-mass spectrometry. Following p.o. administration, marbofloxacin had a peak plasma concentration (Cmax) of 9.40 microg/ml and a time to Cmax (Tmax) of 9.0 hr. Based on the plasma pharmacokinetics generated in this study and pending any further studies to evaluate potential toxicity and multi-dose pharmacokinetics, we suggest a dosage for marbofloxacin in ball pythons of 10 mg/kg p.o. at least every 48 hr, depending on the sensitivity of the pathogen and as a basis for further research.

Lack of effect of DX-619, a novel des-fluoro(6)-quinolone, on glomerular filtration rate measured by serum clearance of cold iohexol

DX-619 is a novel des-fluoro(6)-quinolone with activity against a broad range of bacterial strains, including methicillin-resistant Staphylococcus aureus. The effects of DX-619 on the glomerular filtration rate (GFR) were evaluated because drug-related increases in serum creatinine levels were observed in studies with healthy volunteers. Forty-one healthy subjects were randomized to receive intravenous DX-619 at 800 mg or placebo once daily for 4 days, and the GFR was directly measured by determination of the clearance of a bolus iohexol injection in 33 subjects who completed the study per protocol. DX-619 was noninferior to placebo for the GFR on the basis of a criterion for a clinically significant difference of -12 ml/min/1.73 m(2). The mean GFRs on day 4 were 101.1 +/- 14.2 ml/min/1.73 m(2) and 100.2 +/- 15.6 ml/min/1.73 m(2) for the volunteers receiving placebo and DX-619, respectively. On day 4 the mean serum creatinine concentration for volunteers receiving DX-619 increased by 30 to 40%, with a corresponding decrease in mean creatinine clearance. Both parameters normalized within 7 days after the cessation of DX-619 treatment. Nonclinical studies suggest that DX-619 increases the serum creatinine concentration by inhibiting excretory tubular transporters. In conclusion, DX-619 administered intravenously at 800 mg once a day for 4 days did not affect the GFR in healthy volunteers. Glomerular toxicity is not expected to present a risk to patients receiving DX-619 in clinical trials, but monitoring of the renal function, with an emphasis on the serum creatinine concentration, is still warranted.

Pharmacokinetics of tipifarnib after oral and intravenous administration in subjects with advanced cancer

The primary objective of this study was to identify intravenous regimens of tipifarnib that would mimic the systemic exposure obtained after the current twice-daily oral administration of tipifarnib. After determination of an intravenous dose that 6 subjects with advanced cancer could tolerate, another 26 subjects were randomly assigned to receive 3 consecutive 4-day regimens of tipifarnib with different treatment sequences: a 100-mg 2-hour intravenous infusion, 200-mg oral administration twice daily, and a 200-mg/d continuous intravenous infusion. The systemic exposure to tipifarnib was comparable among these 3 regimens. The plasma concentration-time profile of 2-hour intravenous infusion more closely resembled the oral administration than did the continuous infusion. Glucuronidation is a metabolic pathway for tipifarnib with concentrations of the glucuronide conjugate greatly exceeding the parent compound after oral and intravenous administration. Analysis of plasma metabolites indicated that tipifarnib also undergoes dealkylation and loss of the imidazole group.

A phase 2 study of the oral farnesyltransferase inhibitor tipifarnib in patients with refractory or relapsed acute myeloid leukemia

This phase 2 study evaluated the efficacy and safety of the oral farnesyltransferase inhibitor tipifarnib in adults with refractory or relapsed acute myeloid leukemia (AML). Patients (n=252) received tipifarnib 600 mg twice a day for 21 days in 28-day cycles. Median age was 62 years; 99 (39%) patients were 65 years or older. Eleven (4%) of 252 patients achieved complete remission (CR) or complete remission with incomplete platelet recovery (CRp; 9 CR and 2 CRp). Nineteen patients (8%), including those who achieved CR/CRp, achieved a reduction in bone marrow blasts to less than 5% blasts. Bone marrow blasts were reduced more than 50% in an additional 8 patients (total = 27; 11%). Median survival was 369 days for patients who achieved CR/CRp. Myelosuppression was the most common adverse event. The most common nonhematologic toxicities were fever, nausea, and hypokalemia. Single-agent treatment with tipifarnib induced durable CR/CRp, which was associated with prolonged survival, in some patients with refractory or relapsed AML. The response rate observed in this heavily pretreated group of patients suggests the requirement to enhance the response rate either by combining tipifarnib with other active agents or determining factors that are predictive of response.

Clinical activity of tipifarnib in hematologic malignancies

Farnesyltransferase inhibitors are a novel class of anticancer agents that competitively inhibit farnesyltransferase. Initially developed to inhibit the farnesylation that is necessary for Ras activation, their mechanism of action seems to be more complex, involving other proteins unrelated to Ras. Of the four classes of farnesyltransferase inhibitors, at least three agents have been investigated in hematologic malignancies. Tipifarnib (R-115777), an orally administered non-peptidomimetic farnesyltransferase inhibitor, has shown promising clinical activity. Preliminary results from clinical trials demonstrate enzyme target inhibition, an acceptable toxicity profile and promising evidence of clinical activity. Ongoing studies will better determine the mechanism of action of tipifarnib and the role of combination with other agents, defining its place in the therapeutic arsenal of hematologic disorders.

Naïve averaged, naïve pooled, and population pharmacokinetics of orally administered marbofloxacin in juvenile harbor seals

OBJECTIVE

To determine the pharmacokinetics of marbofloxacin after oral administration in juvenile harbor seals (Phoca vitulina) at a dose of 5 mg/kg (2.3 mg/lb) and to compare pharmacokinetic variables after pharmacokinetic analysis by naïve averaged, naïve pooled, and nonlinear mixed-effects modeling.

DESIGN

Original study. Animals-33 male and 22 female juvenile seals being treated for various conditions.

PROCEDURES

Blood collection was limited to < or = 3 samples/seal. Plasma marbofloxacin concentrations were measured via high-pressure liquid chromatography with UV detection.

RESULTS

Mean +/- SE dose of marbofloxacin administered was 5.3 +/- 0.1 mg/kg (2.4 +/- 0.05 mg/lb). The terminal half-life, volume of distribution (per bioavailability), and clearance (per bioavailability) were approximately 5 hours, approximately 1.4 L/kg, and approximately 3 mL/min/kg, respectively (values varied slightly with the method of calculation). Maximum plasma concentration and area under the plasma-time concentration curve were approximately 3 microg/mL and 30 h x microg/mL, respectively. Naïve averaged and naïve pooled analysis appeared to yield a better fit to the population, but nonlinear mixed-effects modeling yielded a better fit for individual seals.

CONCLUSIONS AND CLINICAL RELEVANCE

Values of pharmacokinetic variables were similar regardless of the analytic method used. Pharmacokinetic variability can be assessed with nonlinear mixed-effects modeling, but not with naïve averaged or naïve pooled analysis. Visual observation by experienced trainers revealed no adverse effects in treated seals. Plasma concentrations attained with a dosage of 5 mg/kg every 24 hours would be expected to be efficacious for treatment of infections caused by susceptible bacteria (excluding Pseudomonas aeruginosa).

Disposition of 1,4,6,8-tetramethyl-furoquinolinone in normal and ascitic tumor bearing mice

1,4,6,8-Tetramethyl-2H-furo[2,3h]quinolin-2-one (FQ) belongs to a series of furocoumarin isosters, designed to obtain new drugs for photochemotherapy. The objective of this study was to characterize the disposition of orally administered 3H-FQ in normal and ascitic tumor bearing mice and to evaluate the influence of UVA irradiation in control mice. This compound was rapidly absorbed and its decay in serum was biphasic. Binding to serum proteins, which was maximum at 30 min (74 %), time-dependently declined. FQ was distributed to all the studied tissues, primarily to the liver and kidneys. The administered radioactivity was excreted mostly in the urine (43 %) and was associated with polar metabolites. The unchanged compound was not present to any detectable extent in the urine. Elimination in the faeces, that may include FQ not absorbed, was low (14 % of administered radioactivity), emphasizing the quantitatively efficient gastrointestinal absorption of the drug. UVA irradiation of FQ-treated mice for 2 h caused a significant increase in radioactivity measured in serum as well as in the liver. In mice bearing Ehrlich ascitic tumor, serum and tissue concentrations were lower than in control animals, possibly due to the larger volume of body fluids (10+/-4 ml of ascitic fluid) available for drug distribution.

Measurement of glycine binding site ofN-methyl-d-asparate receptors in living human brain using 4-acetoxy derivative of L-703,717, 4-acetoxy-7-chloro-3-[3-(4-[11c] methoxybenzyl) phenyl]-2(1H)-quinolone (AcL703) with positron emission tomography

N-methyl-D-aspartate (NMDA) receptors are of major interest in brain functions and neuropsychiatric disorders. However, at present there are few suitable radioligands for in vivo imaging of NMDA receptors. 7-choloro-4-hydroxy-3-[3-(4-methoxybenzyl) phenyl]-2(1H)-quinolone (L-703,717) is one of the potent ligands for the glycine-binding site of NMDA receptors. 4-Acetoxy derivative of L-703,717 (AcL703) is a candidate, as a positron emission tomography (PET) ligand for NMDA receptors, because of its better permeability at the blood-brain barrier compared with L-703,717. After intravenous injection of 624-851 MBq of [11C]AcL703, dynamic PET scan was performed on six healthy males for 90 min. Regions-of-interest were located on the cerebral cortices, cerebellar cortex, and cerebral white matter. The binding potential (BP) was calculated from the ratio of the area under the curve (AUC) of radioactivities from 40 to 90 min in the target region to that in white matter. Regional radioactivities reached close to equilibrium in all regions after about 40 min postinjection. Regional brain uptake of [11C]AcL703 at 40 min after injection was 0.00028-0.00065% of the injected dose/milliliter. Radioactivity concentration of [11C]AcL703 was highest in the cerebellar cortex and lowest in white matter. AUC in the cerebellar cortex was higher than those of cerebral cortices, thalamus, striatum, and white matter. BP in the cerebellar cortex was twofold higher than in the cerebral cortices (cerebellar cortex: BP=2.20+/-0.72; cerebral cortices: BP=1.05+/-0.45). Despite the low brain uptake of [11C]AcL703, regional distributions were in good agreement with our previous studies of rodents. This indicates the possibility of in vivo evaluation of NMDA receptors using PET with [11C]AcL703 in living human brain.

Determination of a series of quinolones in pig plasma using solid-phase extraction and liquid chromatography coupled with mass spectrometric detection

A simple and sensitive liquid chromatography (LC) method was developed for the simultaneous determination of eight quinolones in pig plasma samples. The following two methods of detection were used: ultraviolet (UV) and mass spectrometry with electrospray ionization (ESI/MS). Sample preparation consisted of solid-phase extraction (SPE) on Strata X cartridges prior to the analysis by LC/UV or LC/ESI/MS. The recovery, linearity, limit of detection (LOD) and limit of quantification (LOQ), precision and accuracy of the method were evaluated using spiked pig plasma samples. The suitability of the method for pharmacokinetic studies was evaluated by determining the concentrations of enrofloxacin (ENR) and ciprofloxacin (CIP) also in pig plasma, after administration of 200mg of enrofloxacin per kilogram of fodder during 5 consecutive days.

Pharmacokinetic Variability of Aripiprazole and the Active Metabolite Dehydroaripiprazole in Psychiatric Patients

Aripiprazole is a new atypical antipsychotic drug with a partial agonist activity at dopamine 2 and serotonin 1A receptors. The metabolism of aripiprazole involves both cytochrome P450 2D6 (CYP2D6) and CYP3A4. This study investigated the pharmacokinetic variability of aripiprazole and the active metabolite dehydroaripiprazole on the basis of 155 drug monitoring samples from psychiatric patients treated with therapeutic doses of aripiprazole (10-30 mg/day). Serum concentrations of drug and metabolite were determined by liquid chromatographic and tandem mass spectrometric detection. Pharmacokinetic variability was expressed as the range in concentration/dose (C/D) ratios, and the effect of sex and occasionally coprescribed CYP2D6 or CYP3A4 inhibitors/inducers was studied. In addition, the dose-concentration relationship and combined interquartile range of concentrations obtained at low dose (10-15 mg/day) and high dose (20-30 mg/day) were described. Individual C/D ratios ranged 37-fold for aripiprazole, 78-fold for dehydroaripiprazole, and 27-fold for the active sum of aripiprazole + dehydroaripiprazole. Median C/D ratios in male and female patients differed by less than 15%, and none of the differences were significant (P > 0.14). Cases of concurrent CYP3A4 inducers/inhibitors were not found, but three patients were coprescribed the potent CYP2D6 inhibitors paroxetine or fluoxetine. No consistent difference in C/D ratio was observed in these three patients compared with the rest of the patients. There was a proportional dose-concentration relationship in the population, and the combined interquartile ranges were 230 to 960 nmol/L for aripiprazole and 330 to 1210 nmol/L for aripiprazole + dehydroaripiprazole. In conclusion, pharmacokinetic variability of aripiprazole is extensive in psychiatric patients but apparently not dependent on dose or sex. The variability of the pharmacologic active sum of aripiprazole + dehydroaripiprazole is 25% to 30% less than aripiprazole, suggesting that variability of aripiprazole is partly determined by metabolism to dehydroaripiprazole.

Comparative pharmacokinetics of marbofloxacin in healthy and Mannheimia haemolytica infected calves

The pharmacokinetics of marbofloxacin were investigated in healthy (n=8) and Mannheimia haemolytica naturally infected (n=8) Simmental ruminant calves following intravenous (i.v.) and intramuscular (i.m.) administration of 2 mg kg(-1) body weight. The concentration of marbofloxacin in plasma was measured using high performance liquid chromatography with ultraviolet detection. Following i.v. administration of the drug, the elimination half-life (t(1/2 beta)) and mean residence time (MRT) were significantly longer in diseased calves (8.2h; 11.13 h) than in healthy ones (4.6 h; 6.1 h), respectively. The value of total body clearance (CL(B)) was larger in healthy calves (3 ml min(-1) kg(-1)) than in diseased ones (1.3 ml min(-1) kg(-1)). After single intramuscular (i.m.) administration of the drug, the elimination half-life, mean residence time (MRT) and maximum plasma concentration (C(max)) were higher in diseased calves (8.0, 12 h, 2.32 microg ml(-1)) than in healthy ones (4.7, 7.4 h, 1.4 microg ml(-1)), respectively. The plasma concentrations and AUC following administration of the drug by both routes were significantly higher in diseased calves than in healthy ones. Protein binding of Marbofloxacin was not significantly different in healthy and diseased calves. The mean value for MIC of marbofloxacin for M. haemolytica was 0.1+/-0.06 microg ml(-1). The C(max)/MIC and AUC(24)/MIC ratios were significantly higher in diseased calves (13.0-64.4 and 125-618 h) than in healthy calves (8-38.33 and 66.34-328 h). The obtained results for surrogate markers of antimicrobial activity (C(max)/MIC, AUC/MIC and T > or = MIC) indicate the excellent pharmacodynamic characteristics of the drug in diseased calves with M. haemolytica, which can be expected to optimize the clinical efficacy and minimize the development of resistance.

Impact of transporter-mediated drug absorption, distribution, elimination and drug interactions in antimicrobial chemotherapy

A comprehensive list of drug transporters has recently become available as a result of extensive genome analysis. Membrane transporters play important roles in determining the pharmacokinetic aspects of intestinal absorption, tissue distribution, and the urinary and biliary excretions of a wide variety of therapeutic drugs. The identification and characterization of transporters responsible for the transfer of nutrients and xenobiotics, including drugs, is expected to provide a scientific basis for understanding drug disposition, as well as the molecular mechanisms of drug-drug/drug-food/drug-protein interactions and inter-individual/inter-species differences. This review focuses on the influence of transporters on the pharmacokinetics of beta-lactam antibiotics, new quinolones, and other antimicrobial agents, as well as focusing on the drug-drug interactions associated with transporter-mediated uptake from the small intestine and transporter-mediated elimination from the kidney and liver.

Inter-species variability of haplamine metabolism and identification of its phase I metabolites from liver microsomes

Haplamine, a pyranoquinoline alkaloid, was isolated from the genus Haplophyllum. The inter-species variability of haplamine metabolism was determined by reversed phase high performance liquid chromatography (HPLC) with UV detection. Microsomes from the liver of rats, mice, rabbits, guinea-pigs and humans were incubated with haplamine. After incubation, samples were extracted with a mixture of ethyl acetate and isopropyl alcohol (90 : 10; v/v). Haplamine and its metabolites were separated by HPLC using Nucleosil C18 Nautilus (5 microm) connected with a precolumn of the same type. The HPLC mobile phase consisted of water (A) and a mixture of methanol and acetonitrile (85 : 15; v/v) (B) used in a gradient mode (17 to 27 % B for 10 min, 27 to 90 % B for 37 min, 90 to 17 % B for 3 min, and finally 17 % B for 3 min) at 1 mL/min. Quantitative and qualitative results showed significant inter-species differences in haplamine metabolism. Qualitative similarities were found between guinea-pigs, rabbits, and humans. The metabolites were isolated by HPLC and identified by GC/MS after silylation. The phase I metabolites identified in human liver microsomes were TRANS/CIS-3,4-dihydroxy-9-O-desmethylhaplamine, TRANS/CIS-3,4-dihydroxyhaplamine and 9-O-desmethylhaplamine.

Mucosal permeability of water-soluble drugs in the equine jejunum: a preliminary investigation

Ussing chambers have been used to study the mucosal permeability of drugs in humans, rats and other species. This data can then be used to develop in vitro/in vivo correlations (IVIVC) for drugs based on the Biopharmaceutics Classification System (BCS). Due to the poor oral bioavailability of many drugs in the horse, this method may be useful for screening drugs before development to determine if they warrant further study. Cephalexin (CPX), marbofloxacin (MAR), metronidazole (MTZ) and fluconazole (FCZ) were chosen for this study based on the wide range of physicochemical properties and bioavailability in the horse. Permeability was ranked as follows: MTZ > FCZ > MAR > CPX. This correlated with the bioavailability (R(2) = 0.633447), the Log P (R(2) = 0.648517), as well as the molecular weight (R(2) = 0.851208) of the drugs. Metronidazole induced a decrease in the tissue transepithelial resistance, suggestive of the possibility of tissue toxicity, which may have falsely increased its permeability. The low permeability of cephalexin across the tissue may indicate a lack of active transporters that are found in other species. From this study, we can conclude that the Ussing chamber is a promising method for determining mucosal permeability in the horse.