Journal of Clinical Pharmacology最新文献

This study was designed to investigate the multiple-dose pharmacokinetics, safety, and tolerability of the selective α4β2 nicotinic acetylcholine partial agonist, varenicline, in elderly (65-85 years old) nonsmokers. Fifty male and female subjects with normal renal function for their age were randomized to receive varenicline or placebo once or twice daily for 3 weeks in an investigator- and subject-blinded parallel-group design. Treatment regimens included weekly titration (n = 14; days 1-7, 0.5 mg once daily; days 8-14, 0.5 mg twice daily; days 15-21, 1 mg twice daily); 2-week twice-daily titration (n = 13; days 1-14, 0.5 mg once daily; days 15-21, 0.5 mg twice daily); 2-week once-daily titration (n = 13; days 1-14, 0.5 mg once daily; days 15-21, 1 mg once daily); and placebo (n = 10). Approximate dose-proportional increases in systemic exposure of varenicline at steady state, based on maximum concentration and area under the plasma concentration-time curve over the 24-hour period at steady state, were observed across the dose range of 0.5 to 2 mg/d. Median time to maximum concentration was 3 hours. Mean elimination half-life was estimated to be approximately 24 to 32 hours and independent of dose. Varenicline was considered to be safe and well tolerated in this elderly nonsmoking population.

Drug interactions are a significant clinical concern, particularly in patients with conditions such as heart disease and hypertension, in whom coadministration of multiple drugs is common. Nebivolol is a selective β(1)-blocker with vasodilatory properties approved for the treatment of hypertension. Drug-drug interactions were investigated when nebivolol was coadministered to subjects classified as poor CYP2D6 metabolizers and extensive CYP2D6 metabolizers who were receiving other drugs commonly administered to patients with hypertension or compounds metabolized by cytochrome P450 (CYP) 2D6. There were no drug-drug interactions when nebivolol was coadministered with hydrochlorothiazide, furosemide, ramipril, losartan, digoxin, or warfarin. Coadministration with fluoxetine (also metabolized by CYP2D6) in extensive CYP2D6 metabolizers impeded the apparent clearance of nebivolol. The authors conclude that nebivolol is safe and well tolerated regardless of genotype and type of medication coadministered.

Comparative pharmacokinetics of vitamin K epoxide reductase antagonists tecarfarin and warfarin were assessed before and after coadministration for 21 days of the CYP450 inhibitor fluconazole in a randomized, open-label, single-center drug interaction study. Twenty healthy adult participants were randomized 1:1 to receive approximately equipotent single oral doses of tecarfarin (50 mg) or warfarin (17.5 mg). Following 7 days of baseline serial blood level collections, each participant received oral fluconazole 400 mg daily for 21 days. A second identical single oral dose of tecarfarin or warfarin was given 14 days after starting fluconazole with serial pharmacokinetic sampling. Key pharmacokinetic parameters C(max), t(max), AUC(0-168), apparent clearance, and t(1/2) demonstrated no tecarfarin-fluconazole interaction but a strong warfarin-fluconazole interaction. The ratio of log-transformed mean AUC(0-168) with versus without fluconazole for tecarfarin was 91.2% (90% confidence interval [CI]: 83.3-99.8) and for racemic warfarin was 213% (90% CI: 202-226). The 90% CI was entirely within the standard 80% to 125% bioequivalence interval for tecarfarin but well outside the bioequivalence interval for warfarin, confirming a clinically significant pharmacokinetic interaction between warfarin and fluconazole. In contrast, tecarfarin pharmacokinetics were apparently unchanged by fluconazole.

Varenicline is a novel selective α4β2 nicotinic acetylcholine partial agonist developed for smoking cessation. Single- and multiple dose studies were conducted to investigate pharmacokinetics, safety, and tolerability of varenicline in healthy male Japanese smokers. The single-dose study was conducted as a double-blind, placebo-controlled, 4-way crossover study. Subjects received varenicline (0.25, 0.5, 1.0, 2.0 mg) or placebo at an interval of 2 weeks. The double-blind, placebo-controlled multiple-dose study was conducted as 2 cohorts, each consisting of 8 subjects randomized to varenicline tablets twice daily (0.5 or 1.0 mg) and 4 subjects randomized to placebo administered for 14 days. In both studies, varenicline was well tolerated at doses up to and including 2 mg daily. Dose-proportional increases in varenicline systemic exposure were observed following single and multiple dosing. Peak plasma concentrations generally occurred within 2 to 4 hours after dosing. Mean half-life estimates ranged from approximately 13 to 19 hours after single dosing and 24 to 28 hours after repeat dosing. Consistent with this, both 0.5 and 1.0 mg twice daily resulted, on average, in an approximate 3-fold increase in varenicline systemic exposure. These results showed that the single- and multiple-dose pharmacokinetics of varenicline in Japanese smokers were similar to those previously reported in Western smokers.

Roflumilast is an oral phosphodiesterase 4 (PDE4) inhibitor for the treatment of chronic obstructive pulmonary disease (COPD). It is metabolized by CYP1A2 and CYP3A4 to its primary metabolite, roflumilast N-oxide, through which >90% total PDE4 inhibitory activity (tPDE4i) is mediated. Fluoroquinolones, of which enoxacin is the most potent CYP1A2 inhibitor, are used to treat COPD exacerbations. This phase I, open, nonrandomized, fixed-sequence, 2-period study evaluated the effects of steady-state enoxacin on the single-dose pharmacokinetics of roflumilast and roflumilast N-oxide. Twenty healthy participants received roflumilast, 500 µg once daily, on days 1 and 12, and enoxacin, 400 mg twice daily, on days 7 to 18. Pharmacokinetic profiles were obtained for days 1 to 6 and 12 to 19. The safety and tolerability of all treatments were also assessed. In 19 evaluable participants, coadministration led to 56% higher mean systemic exposure, 20% higher mean peak concentrations, and 36% lower mean apparent oral clearance compared with roflumilast alone. For roflumilast N-oxide, 23% higher mean systemic exposure and 14% lower mean peak concentrations were seen after coadministration. Roflumilast was well tolerated both alone and in combination with enoxacin. A weak interaction was shown between roflumilast and enoxacin, as mean tPDE4i increased by 25%, but is unlikely to have clinical relevance.

Vestibular loss induces a combination of postural, oculomotor, and perceptive symptoms that are compensated over time. The aim of this study was to analyze the influence of betahistine dihydrochloride on vestibular compensation. A randomized, double-blind, placebo-controlled study was performed in Menière's disease patients who underwent a curative unilateral vestibular neurotomy (UVN). The effects of betahistine treatment were investigated on a broad spectrum of vestibular-induced changes resulting from vestibular loss: body sway, head orientation, ocular cyclotorsion, spontaneous nystagmus, verticality perception, and self-evaluation of the postural stability. The time course of the recovery was compared in 16 patients who received either a placebo or betahistine (24 mg b.i.d.) from 3 days up to 3 months after UVN. Patients were examined before (day -1) and after UVN (days 7, 30, and 90). Results indicate that betahistine reduces the time to recovery by 1 month or more depending on the tested functions. Betahistine was effective as soon as 4 days after treatment administration, and the effect remained during the whole compensation period (up to 3 months). The observed clinical effects may be attributed to an action of betahistine in rebalancing the neuronal activity between contralateral vestibular nuclei.

Oral delivery of proteins has been hampered by an array of difficulties. However, promising novel oral delivery systems have been developed. 5-CNAC, formulated with the peptide salmon calcitonin, is in phase III clinical trials for the treatment of osteoporosis or osteoarthritis and could become the first marketed oral peptide. This article reviews key findings and implications from studies undertaken to date with this oral formulation. Findings include these: (1) the optimal calcitonin tablet dose is 0.8 mg; (2) 0.8 mg of oral calcitonin is rapidly absorbed, reaching maximum concentration in 15 to 30 minutes, and is eliminated from plasma with a short half-life-9 to 15 minutes; (3) the 0.8-mg tablet is more highly absorbed than the marketed nasal formulation, with biomarker levels indicating significantly greater efficacy in suppression of bone resorption; (4) drug absorption is increased with dosing at least 10 minutes before a meal rather than postprandially and also with 50 mL of water; (5) the optimal timing of dosing for osteoporosis therapy is in the evening to mitigate the circadian peak in bone resorption; and (6) the oral formulations of synthetic and recombinant calcitonin have similar pharmacokinetic and pharmacodynamic properties. These key findings may aid researchers in the development of other oral formulations.

Polymorphisms in the drug transporter gene (ABCB1) may play a significant role in individualizing cyclosporine (CsA) and tacrolimus (Tac) dosage and subsequently the allograft outcome in renal transplant recipients. In total, 225 recipients on CsA and 75 on Tac-based immunosuppression regimen were recruited, and 6 common polymorphic sites in the ABCB1 gene were analyzed for association with dose-adjusted levels of CsA/Tac. Furthermore, association of ABCB1 single-nucleotide polymorphisms (SNPs) with allograft outcome was examined. GG and CC genotype patients at ABCB1 2677G>T and ABCB1 3435C>T were associated with lower dose-adjusted levels of CsA and Tac at 1 month (P = .057, P = .034), 3 months (P = .001, P = .015), and 6 months (P = .043) posttransplantation. Wild-type patients at 1236C>T (log P = .025) and 2677G>T (log P = .002) in CsA and 2677G>T (log P = .008) and 3435C>T (log P = .015) in Tac therapy patients demonstrated lower mean time to allograft rejection. No influence of ABCB1 haplotypes on CsA/Tac dose-adjusted levels was observed. Wild-type patients at ABCB1 2677G>T and 3435C>T were associated with lower dose-adjusted levels and thereby were at increased risk of allograft rejection because of under-immunosuppression in the early part of posttransplantation. Thus, genetic evaluation may be helpful to identify patients at risk for allograft rejection and also to individualize immunosuppressant dosing.