ABSTRACT:A number of antidepressants inhibit the activity of the cytochrome P450 2D6 enzyme system, which can lead to drug-drug interactions. Based on its metabolic profile, desvenlafaxine, administered as desvenlafaxine succinate, a new serotonin-norepinephrine reuptake inhibitor, is not expected to have an impact on activity of CYP2D6. This single-center, randomized, open-label, four-period, crossover study was undertaken to evaluate the effect of multiple doses of desvenlafaxine (100 mg/day, twice the recommended therapeutic dose for major depressive disorder in the United States) and duloxetine (30 mg b.i.d.) on the pharmacokinetics (PK) of a single dose of desipramine (50 mg). A single dose of desipramine was given first to assess its PK. Desvenlafaxine or duloxetine was then administered, in a crossover design, so that steady-state levels were achieved; a single dose of desipramine was then coadministered. The geometric least-square mean ratios (coadministration versus desipramine alone) for area under the plasma concentration versus time curve (AUC) and peak plasma concentrations (C max ) of desipramine and 2-hydroxydesipramine were compared using analysis of variance. Relative to desipramine alone, increases in AUC and C max of desipramine associated with duloxetine administration (122 and 63%, respectively) were significantly greater than those associated with desvenlafaxine (22 and 19%, respectively; P < 0.001). Duloxetine coadministered with desipramine was also associated with a decrease in 2-hydroxydesipramine C max that was significant compared with the small increase seen with desvenlafaxine and desipramine (؊24 versus 9%; P < 0.001); the difference between changes in 2-hydroxydesipramine AUC did not reach statistical significance (P ‫؍‬ 0.054). Overall, desvenlafaxine had a minimal impact on the PK of desipramine compared with duloxetine, suggesting a lower risk for CYP2D6-mediated drug interactions.Concomitant use of a drug that affects the activity of the same cytochrome P450 (P450) enzyme system responsible for biotransformation of another drug can lead to significant elevations in plasma concentration and potentially important drug-drug interactions (Preskorn and Flockhart, 2004). Such interactions may be associated with poor tolerability or increased risk for toxicity. In addition, for drugs requiring biotransformation via P450 enzymes from an inactive/less active parent compound to a pharmacologically active metabolite, drug interactions may manifest as a reduction in efficacy (Stearns et al., 2003;Preskorn and Flockhart, 2004;Preskorn and Werder, 2006). Drug interactions have an impact on clinical care and may create the need for dose adjustments, consideration of different therapeutic options, or other management strategies.Several antidepressants are known to inhibit CYP2D6 activity (Zanger et al., 2004). The selective serotonin reuptake inhibitors are associated with varying degrees of CYP2D6 inhibition. For example, paroxetine and fluoxetine strongly inhibit CYP2D6 (K i of 2.0 and 3.0 ...

Anacetrapib is currently being developed for the oral treatment of dyslipidemia. A clinical study was conducted in healthy subjects to assess the potential for an interaction with orally administered digoxin. Anacetrapib was generally well tolerated when co-administered with digoxin in the healthy subjects in this study. The geometric mean ratios (GMR) for (digoxin + anacetrapib/digoxin alone) and 90% confidence intervals (CIs) for digoxin AUC(0-last) and AUC(0-∞) were 1.05 (0.96, 1.15) and 1.07 (0.98, 1.17), respectively, both being contained in the accepted interval of bioequivalence (0.80, 1.25), the primary hypothesis of the study. The GMR (digoxin + anacetrapib /digoxin alone) and 90% CIs for digoxin C(max) were 1.23 (1.14, 1.32). Median T(max) and mean apparent terminal t(½) of digoxin were comparable between the two treatments. The single-dose pharmacokinetics of orally administered digoxin were not meaningfully affected by multiple-dose administration of anacetrapib, indicating that anacetrapib does not meaningfully inhibit P-glycoprotein. Thus, no dosage adjustment for digoxin is necessary when co-administered with anacetrapib.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Inhibition of cholesteryl ester transfer protein (CETP) is a potential new mechanism for the treatment of dyslipidaemia. Anacetrapib is a novel CETP inhibitor in development. Warfarin is a commonly prescribed anticoagulant that has a narrow therapeutic index. A drug interaction study for warfarin with a novel CETP inhibitor is expected to be helpful in defining dosing regimens. WHAT THIS STUDY ADDS• This is the first study to show that there is no clinically meaningful pharmacokinetic interaction between anacetrapib and warfarin. The single dose pharmacokinetics and pharmacodynamics of orally administered warfarin were not meaningfully affected by multiple dose administration of anacetrapib, indicating that anacetrapib does not affect CYP 2C9 clinically. Thus, no dosage adjustment for warfarin is necessary when co-administered with anacetrapib. AIMAnacetrapib is currently being developed for the treatment of dyslipidaemia. Since warfarin, an anticoagulant with a narrow therapeutic index, is expected to be commonly prescribed in this population, a drug interaction study was conducted. METHODSIn a randomized, open-label, two-period fixed-sequence design, 12 healthy male subjects received two different treatments (treatment A followed by treatment B). In treatment A, a single oral dose of 30 mg warfarin (3 ¥ 10 mg Coumadin TM ) was administered on day 1. After a washout interval, subjects began treatment B, where they were given daily 100 mg doses of anacetrapib (1 ¥ 100 mg) beginning on day -14 and continuing through day 7, with concomitant administration of 30 mg warfarin (3 ¥ 10 mg) on day 1. All anacetrapib and warfarin doses were administered with a standard low fat breakfast. After warfarin concentrations and prothrombin time were measured, standard pharmacokinetic, pharmacodynamic and statistical (linear mixed effects model) analyses were applied. RESULTSAnacetrapib was generally well tolerated when co-administered with warfarin in the healthy males in this study. The geometric mean ratios (GMRs) for warfarin + anacetrapib : warfarin alone and 90% confidence interval (CIs) for warfarin AUC(0-•) were 0.94 (0.90, 0.97) for the R(+) warfarin enantiomer and 0.93 (0.87, 0.98) for the S(-) warfarin enantiomer, both being contained in the interval (0.80, 1.25), supporting the primary hypothesis of the study. The GMRs warfarin + anacetrapib : warfarin alone and 90% CIs for the statistical comparison of warfarin Cmax were 1.01 (0.97, 1.05) for both the R(+) warfarin and the S(-) warfarin enantiomers, and were also contained in the interval (0.80, 1.25). The GMR (warfarin + anacetrapib : warfarin alone) and 90% CI for the statistical comparison of INR AUC(0-168 h) was 0.93 (0.89, 0.96). CONCLUSIONThe single dose pharmacokinetics and pharmacodynamics of orally administered warfarin were not meaningfully affected by multiple dose administration of anacetrapib, indicating that anacetrapib does not affect CYP 2C9 clinically. Thus, no dosage adjustment for warfarin is necessary whe...

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Test and reference formulations met the regulatory criteria for bioequivalence in the fasting healthy volunteers enrolled.