Alice I. Nichols

Cytochrome P450 2D6 phenotype predicts antidepressant efficacy of venlafaxine: a secondary analysis of 4 studies in major depressive disorder.

INTRODUCTION Venlafaxine, a serotonin-norepinephrine reuptake inhibitor antidepressant, is metabolized primarily by the cytochrome P450 2D6 enzyme into O-desmethylvenlafaxine (ODV). The ODV/venlafaxine ratio can be used to distinguish between extensive metabolizers (EMs) and poor metabolizers (PMs). OBJECTIVES To determine the relative efficacy and tolerability of venlafaxine in EM vs PM patients with major depressive disorder (MDD). METHOD Data from 4 double-blind, placebo-controlled studies of patients with MDD were pooled. Blood samples were analyzed for plasma concentrations of venlafaxine, ODV, total venlafaxine + ODV, and ODV/venlafaxine ratio. Patients were classified as EMs or PMs on the basis of ODV/venlafaxine ratios. Changes from baseline in depression scale scores were compared between EMs and PMs using t tests. Rates of response, remission, discontinuation, and adverse events (AEs) were compared for EMs and PMs using Fisher exact tests. RESULTS Compared with PMs, EMs had significantly greater mean changes from baseline on 4 of 5 depression rating scales (all 4 comparisons, P ≤ .020). A significantly greater percentage of EMs achieved response or remission by most measures compared with PMs (4 of 5 comparisons, P ≤ .015). Rates of discontinuation and AEs did not differ significantly between EMs and PMs. Since there were no substantial differences between EMs and PMs in terms of venlafaxine dose or tolerability, these factors are not likely to account for the efficacy findings. CONCLUSIONS Venlafaxine treatment in EMs was associated with greater efficacy in MDD on virtually all measures compared with PMs, with no important tolerability differences.

Comparison of the Pharmacokinetics of Venlafaxine Extended Release and Desvenlafaxine in Extensive and Poor Cytochrome P450 2D6 Metabolizers

Background: The goal of this study was to evaluate the impact of cytochrome P450 2D6 extensive metabolizer (EM) or poor metabolizer (PM) status on the pharmacokinetics of single doses of venlafaxine extended release (ER) and desvenlafaxine (administered as desvenlafaxine succinate) in healthy adults. Methods: In an open-label, crossover study, 14 healthy volunteers (aged 18-55 years; 7 EMs and 7 PMs) received, in randomized sequence, single doses of venlafaxine ER 75 mg/d or desvenlafaxine 100 mg/d. Cytochrome P450 2D6 genotyping was performed, and plasma drug levels were measured. The arithmetic means and standard deviation (SD) for area under the plasma concentration-versus-time curve (AUC) and peak plasma concentration (Cmax) were calculated. Comparisons of AUC and Cmax between cytochrome P450 2D6 EMs and PMs were calculated using a Wilcoxon exact test. Results: After administration of venlafaxine ER, mean Cmax and AUC of venlafaxine were significantly greater in PMs compared with EMs, whereas mean Cmax and AUC of its metabolite, desvenlafaxine, were significantly lower for PMs than for EMs (P = 0.001, all comparisons). In contrast, mean Cmax and AUC of desvenlafaxine after administration of desvenlafaxine were comparable between EMs and PMs. Conclusions: Cytochrome P450 2D6 genetic polymorphisms had no discernible impact on exposure to desvenlafaxine after desvenlafaxine administration; in contrast, compared with an EM phenotype, a PM phenotype had a significant effect on venlafaxine and desvenlafaxine plasma concentrations after venlafaxine ER administration. This reduced pharmacokinetic variability of desvenlafaxine may translate into better uniformity of response for patients receiving desvenlafaxine versus venlafaxine, but additional studies are required to test this hypothesis.

An Assessment of Drug-Drug Interactions: The Effect of Desvenlafaxine and Duloxetine on the Pharmacokinetics of the CYP2D6 Probe Desipramine in Healthy Subjects

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 (Cmax) of desipramine and 2-hydroxydesipramine were compared using analysis of variance. Relative to desipramine alone, increases in AUC and Cmax 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 Cmax 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.

Pharmacokinetics of Venlafaxine Extended Release 75 mg and Desvenlafaxine 50 mg in Healthy CYP2D6 Extensive and Poor Metabolizers

BackgroundGenetically driven variations in the level of cytochrome P450 (CYP) 2D6 metabolic activity have been shown to significantly affect the pharmacokinetic behaviour of medications that are substrates of this enzyme.ObjectiveTo evaluate the impact of CYP2D6 extensive metabolizer (EM) and poor metabolizer (PM) phenotypes on the pharmacokinetics of single doses of venlafaxine extended release (ER) and desvenlafaxine (administered as desvenlafaxine succinate).MethodsThis study used a randomized, open-label, two-period, parallel-group, crossover design. The enrolled healthy subjects participated in the study for approximately 8 weeks, which included ≤6 weeks of screening procedures and two separate 1-week partial inpatient confinement periods (separated by a 4-day washout period), during which venlafaxine ER or desvenlafaxine was administered and blood samples were collected. Subjects were admitted to partial inpatient confinement in a laboratory setting for the two separate study periods where each study drug was individually administered. Blood samples for pharmacokinetic analyses were collected during the 120 hours following administration of each study drug. Plasma concentrations of the study drugs were measured by a third-party analyst using liquid chromatography-tandem mass spectrometry. Healthy subjects were recruited through newspaper advertisements and genotyped to determine their CYP2D6 metabolic phenotype (i.e. EM or PM) using internally developed and commercially available assays. Subjects were reimbursed for their participation in this study. Single, sequentially administered oral doses of the dual-acting, serotonin and norepinephrine reuptake inhibiting antidepressants venlafaxine ER (75 mg) and desvenlafaxine (50 mg) were administered. The main outcome measures were differences in the geometric means for area under the plasma concentration-time curve from time zero to infinity (AUC∞) and peak plasma concentration (Cmax) between EMs and PMs. Comparisons were made using a 2-tailed Wilcoxon exact test.ResultsNo carryover effect was observed between treatment sequence groups. There was no statistically significant difference in either Cmax or AUC∞ of O-desmethylvenlafaxine between PMs (n = 7) and EMs (n=7) following administration of desvenlafaxine 50 mg. However, when subjects received venlafaxine ER 75 mg, the AUC∞ and Cmax of O-desmethylvenlafaxine (the primary active metabolite) were 445% and 434% higher, respectively, in EMs compared with PMs (p ≤ 0.001), and the AUC∞ and Cmax of venlafaxine were 445% and 180% higher, respectively, in PMs compared with EMs (p<0.01). In addition, the ratios of O-desmethylvenlafaxine: venlafaxine AUC∞ and Cmax for subjects receiving venlafaxine ER 75 mg were higher for EMs (6.2 and 3.3) than PMs (0.21 and 0.22; p ≤ 0.001 for both comparisons).ConclusionIn contrast to venlafaxine ER 75 mg, the pharmacokinetics of desvenlafaxine 50 mg is not significantly impacted by CYP2D6 genetic polymorphisms. PMs receiving venlafaxine ER 75 mg had significantly lower O-desmethylvenlafaxine and higher venlafaxine plasma concentrations.

The Effects of Desvenlafaxine and Paroxetine on the Pharmacokinetics of the Cytochrome P450 2D6 Substrate Desipramine in Healthy Adults

The potential for cytochrome P450 (CYP) 2D6 substrates to interact with desvenlafaxine (administered as desvenlafaxine succinate) and paroxetine was evaluated. In an open‐label, crossover study, 20 healthy volunteers (aged 21–50) were randomized to 2 series of 9 days each of desvenlafaxine (100 mg/d) or paroxetine (20 mg/d), separated by a 5‐day washout. The CYP2D6 substrate desipramine (50 mg) was administered alone on day 1 and coadministered on day 6 of dosing with either desvenlafaxine or paroxetine. CYP2D6 genotype was determined at baseline. Based on least squares geometric mean ratios between reference (desipramine alone) and test treatments, desvenlafaxine produced minor increases in desipramine area under the plasma concentration versus time curve (AUC; 36%) and peak plasma concentration (Cmax; 30%) (vs paroxetine: 419%, 90%, respectively; both P < .001). Desvenlafaxine produced little change in 2‐hydroxydesipramine AUC (16% increase) and Cmax (0%) versus paroxetine (18% and 82% decreases, respectively; P = .008, P < .001, respectively), indicating that desvenlafaxine, especially at the recommended therapeutic dose of 50 mg/d for major depressive disorder in the United States, has little potential to interact with CYP2D6 substrates.

Venlafaxine metabolism as a marker of cytochrome P450 enzyme 2D6 metabolizer status.

Introduction: One of the major enzymes of the cytochrome P450 drug-metabolizing system, CYP2D6, shows a high degree of genetic polymorphism and variability in activity. Based on the degree of CYP2D6 activity, individuals can be broadly classified as poor metabolizers (PMs) or extensive metabolizers (EMs); the metabolism of CYP2D6 substrates differs among PMs and EMs. The metabolism of various drugs that are substrates of CYP2D6 has been used as a marker for metabolic phenotype, calculating the plasma or urinary metabolic ratio of the parent compound to its metabolite. The current analysis evaluates the use of the O-desmethylvenlafaxine-venlafaxine ratio (ODV/VEN) after administration of VEN, a CYP2D6 substrate, for determining CYP2D6 metabolic phenotype in healthy adults receiving VEN. Methods: The analysis included data from 2 studies in which healthy adults were classified as either EMs or PMs using established methods (1 genotypic and 1 phenotypic) and were then administered VEN at daily dosages ranging from 75 to 150 mg. Blood plasma samples were taken at various time points, and the ODV/VEN ratio was calculated. Results: Blood samples from 28 participants in the 2 studies were available for analysis. The ODV/VEN ratio distinguished the EM and PM phenotypes; ratios were 1 or greater for EMs and less than 1 for PMs at 4 hours after dose administration. Conclusions: The ratio of ODV/VEN is an effective means of phenotyping individuals according to their CYP2D6 metabolizer status.

Effect of desvenlafaxine on the cytochrome P450 2D6 enzyme system.

Background The cytochrome P450 2D6 (CYP2D6) enzyme is responsible for metabolizing approximately 25% of pharmaceutical agents. Individuals with impaired CYP2D6 metabolism and those concomitantly receiving agents that inhibit CYP2D6 can have variations in concentrations of such medications and their metabolites. Methods Five studies assessing the interaction between desvenlafaxine and CYP2D6 are reviewed. Study 1 compared desvenlafaxine area under the plasma concentration-versus-time curve (AUC) in CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs) after administration of 100 mg of desvenlafaxine or 75 mg of venlafaxine extended release (ER). Studies 2 to 5 assessed the effect of concomitant administration of desvenlafaxine 100 mg (studies 2, 4, and 5) or 400 mg (study 3), paroxetine (20 mg, study 4), and duloxetine (30 mg twice daily; study 5) on the CYP2D6 probe desipramine. Results In study 1, there was no significant difference in mean desvenlafaxine AUC between the CYP2D6 EMs and PMs (−11%; P=0.641) who were administered desvenlafaxine. However, PMs receiving venlafaxine ER had significantly higher venlafaxine and lower desvenlafaxine AUCs compared with EMs (+350% and −74%, respectively; P<0.001 for each). In studies 2, 4, and 5, the mean increases in desipramine AUC with concomitant administration of desvenlafaxine 100 mg ranged from 17% to 36%; the increase with concomitant administration of desvenlafaxine 400 mg (study 3) was 90%. Paroxetine and duloxetine produced increases in mean desipramine AUC of 419% and 122%, respectively, which were significantly greater than the increases seen with desvenlafaxine 100 mg (P<0.001 for each comparison). Conclusions Based on the findings presented here, desvenlafaxine is expected to have a low risk for variability in efficacy and safety/tolerability resulting from CYP2D6 polymorphisms or drug-drug interactions when coadministered with CYP2D6 substrates or inhibitors.

The pharmacokinetics and safety of desvenlafaxine in subjects with chronic renal impairment.

BACKGROUND Desvenlafaxine (administered as desvenlafaxine succinate), the major active metabolite of venlafaxine, is a new serotonin-norepinephrine reuptake inhibitor (SNRI) approved for the treatment of major depressive disorder (MDD). OBJECTIVE To assess the pharmacokinetics, safety, and tolerability of desvenlafaxine in healthy volunteers vs. those with renal impairment. MATERIALS AND METHODS A single, oral, 100 mg dose of desvenlafaxine was administered to healthy subjects (n = 8) and subjects with mild (n = 9), moderate (n = 9), or severe (n = 7) renal impairment (24-h creatinine clearance, ml/min: 50 - 80, 30 - 50, or < 30 ml/min, respectively) or end-stage renal disease (ESRD; on dialysis.

An open-label, single-dose, parallel-group study of the effects of chronic hepatic impairment on the safety and pharmacokinetics of desvenlafaxine.

BACKGROUND Many antidepressants are extensively metabolized in the liver, requiring dose adjustments in individuals with hepatic impairment. Clinical studies indicate that the serotonin-norepinephrine reuptake inhibitor desvenlafaxine is metabolized primarily via glucuronidation, and ∼45% is eliminated unchanged in urine. OBJECTIVE The objectives of this study were to assess the pharmacokinetic profile, safety, and tolerability of desvenlafaxine in adults with chronic Child-Pugh class A, B, and C hepatic impairment. METHODS Subjects (aged 18-65 years) with mild (Child-Pugh class A, n = 8), moderate (Child-Pugh class B, n = 8), and severe (Child-Pugh class C, n = 8) hepatic impairment and 12 healthy matched subjects received a single 100-mg oral dose of desvenlafaxine. Disposition of (R)-, (S)-, and (R+S)-enantiomers of desvenlafaxine were examined in plasma and urine. Geometric least squares (GLS) mean ratios and 90% CIs for AUC, AUC0-τ, Cmax, and Cl/F were calculated; comparisons were made by using a 1-factor ANOVA. Safety was evaluated according to adverse events, physical examination, vital signs, and laboratory assessments. RESULTS Healthy participants had a mean age of 51 years (range, 36-62 years) and weight of 79.1 kg (range, 52.5-105.0 kg); hepatically impaired participants had a mean age of 52 years (range, 31-65 years) and weight of 80.9 kg (range, 50.2-119.5 kg). In both groups, 67% of participants were male. No statistically significant differences (≥50%) in the disposition of desvenlafaxine were detected between hepatically impaired patients and healthy subjects based on GLS mean ratios for Cmax, AUC0-τ, AUC, or Cl/F (P > 0.05 for each comparison). Median Tmax was similar for all groups (range, 6-9 hours). A nonsignificant increase was observed for desvenlafaxine exposure in patients with moderate or severe hepatic impairment (GLS mean ratios [90% CIs] for AUC, 31% [93.2-184], 35% [96.5-190], respectively). The most common adverse events were nausea (n = 2, healthy subjects; n = 3, hepatically impaired subjects) and vomiting (n = 1, healthy subjects; n = 2, hepatically impaired subjects). CONCLUSIONS A single 100-mg dose of desvenlafaxine was well tolerated in healthy subjects and hepatically impaired patients. A mild increase in exposure was observed for moderate and severe hepatically impaired subjects (Child-Pugh class B and C).

Desvenlafaxine for major depressive disorder: incremental clinical benefits from a second-generation serotonin-norepinephrine reuptake inhibitor.

Importance of the field: Genetic and pharmacologically-driven variations in common mechanisms involved in the disposition of antidepressant medications may contribute to variable interpatient response. This review describes the pharmacological properties underlying the safety and efficacy of desvenlafaxine, a second-generation serotonin–norepinephrine reuptake inhibitor (SNRI). Areas covered in this review: Literature published between January 2006 and September 2010 evaluating desvenlafaxine was reviewed. What will the reader gain: Desvenlafaxine therapy is initiated at the therapeutic dose (50 mg/day) without a need for dose titration. Desvenlafaxine metabolism and distribution are not appreciably affected by altered function of cytochrome P450 (CYP) enzymes or permeability glycoprotein (P-gp). Desvenlafaxine has clinically insignificant effects on the activity of CYP and P-gp. The efficacy of desvenlafaxine in treating major depressive disorder has been established. Adverse events are characteristic of the SNRI class. Notably, the rate of discontinuation due to adverse events with the 50 mg/day recommended therapeutic dose is comparable to that seen with placebo. Take home message: Incremental benefits with desvenlafaxine, derived from straight-forward dosing, a simple metabolic profile and lack of interaction with active transporter P-gp and CYP enzymes may contribute to more consistent response, good tolerability and lower incidence of drug–drug interactions with concomitant medications.