Effects of vilazodone on sexual functioning in healthy adults: results from a randomized, double-blind, placebo-controlled, and active-controlled study

Abstract

The aim of this study is to evaluate the effects of vilazodone on sexual functioning in healthy, sexually active adults and assess the impact of medication nonadherence in this type of trial. Participants were randomized to vilazodone (20 or 40 mg/day), paroxetine (20 mg/day), or placebo for 5 weeks of double-blind treatment. The primary endpoint was change from baseline to day 35 in Change in Sexual Functioning Questionnaire (CSFQ) total score in the intent-to-treat (ITT) population. Post-hoc analyses were carried out in modified intent-to-treat (mITT) populations that excluded participants in the active-treatment groups with undetectable plasma drug concentrations at all visits (mITT-I) or at least one visit (mITT-II). In the ITT population (N=199), there were no statistically significant differences between any treatment groups for CSFQ total score change: placebo, -1.0; vilazodone 20 mg/day, -1.4; vilazodone 40 mg/day, -1.9; and paroxetine, -3.5. In mITT-I (N=197) and mITT-II (N=159), CSFQ total score change was not significantly different between vilazodone (either dose) versus placebo; the CSFQ total score decreased significantly (P<0.05) with paroxetine versus both placebo and vilazodone 20 mg/day, but not versus vilazodone 40 mg/day. Vilazodone exerted no significant effect on sexual functioning in healthy adults. Medication nonadherence can alter study results and may be an important consideration in trials with volunteer participants.

Fig. 1

Change from baseline to day 35 in the CSFQ total score (MMRM). Sample size (n-value) represents the number of participants in each treatment group who had an available CSFQ total score assessment at day 35. For the mITT-I and mITT-II analyses, participants in the vilazodone and paroxetine groups with undetectable plasma drug concentrations at day 35 were excluded. *P<0.05, active drug versus placebo; ^§P<0.05, vilazodone versus paroxetine. CSFQ, Changes in Sexual Functioning Questionnaire; ITT, intent-to-treat; LS, least squares; mITT, modified intent-to-treat; MMRM, mixed-effects model for repeated measures.

Fig. 2

CSFQ sexual dysfunction by study visit (mITT-I population). Sexual dysfunction defined as CSFQ total score ≤47 (men) or ≤41 (women). Sample size (n-value) represents the number of participants in each treatment group who had an available CSFQ total score assessment at the study visit analyzed (day 8, 15, 22, or 35) and, in the active-treatment groups, had detectable plasma drug concentrations at the respective visit. CSFQ, Changes in Sexual Functioning Questionnaire; mITT, modified intent-to-treat.

Fig. 3

Change from baseline to day 35 in CSFQ subscale scores (mITT-I population, MMRM). Sample size (n-value) represents the number of participants in each treatment group who had available CSFQ subscale score assessments at day 35, and, in the active-treatment groups, had detectable plasma drug concentrations at day 35. *P<0.05, active drug versus placebo; ^§P<0.05, vilazodone versus paroxetine. CSFQ, Changes in Sexual Functioning Questionnaire; LS, least squares; mITT, modified intent-to-treat; MMRM, mixed-effects model for repeated measures.