Pfizer announced the publication of a clinical study in the Journal of Clinical Psychiatry showing comparable sexual function in adult patients diagnosed with major depressive disorder (MDD) treated daily with Pristiq extended release tablets 50mg and 100mg doses versus placebo. Sexual dysfunction is often an issue for patients treated with antidepressants, and Pfizer conducted the study pursuant to a post marketing requirement by the US Food and Drug Administration (US FDA).

“Sexual dysfunction is a common concern for patients treated with antidepressants. This study showed that sexual function was comparable between desvenlafaxine and placebo,” said Dr. Anita Clayton, interim chair, Department of Psychiatry and Neurobehavioural Sciences at the University of Virginia Health System, and lead investigator of the study. “The low potential for sexual dysfunction with desvenlafaxine is encouraging, and physicians and patients would benefit from further study.”

The primary end point of the study showed a statistically significant improvement among patients treated with Pristiq compared to placebo in symptoms of major depressive disorder as measured by the 17-item Hamilton Rating Scale for Depression (HAM-D17) total score over an 8-week period. The HAM-D17 is a validated assessment tool used to rate the severity of a patient’s depressive symptoms. Sexual dysfunction was a secondary end point, and measured using the Arizona Sexual Experiences Scale (ASEX), a validated and reliable patient rated sexual function scale in the United States.

An estimated 33 million to 35 million US adults are likely to experience major depression at some point during their lifetime. The criteria for MDD include having five or more of the symptoms of depression listed below during the same two-week period and representing a change from previous functioning. Depressed mood or diminished interest or pleasure must be among the depression symptoms reported from the following list: depressed mood; diminished interest or pleasure; significant weight loss or change in appetite; insomnia/hypersomnia; psychomotor agitation; fatigue or loss of energy; feelings of worthlessness or excessive/inappropriate guilt; difficulty concentrating; and recurrent thoughts of death.

In this phase 4, multi-centre, randomised, double blind placebo-controlled study, a total of 924 patients, 18-years or older, with a baseline HAM-D17 score of =20, were randomly assigned to Pristiq 50mg/day, Pristiq 100 mg/day or placebo in a 1:1:1 ratio over an 8-week period. The primary efficacy end point for the study was the change from baseline in HAM-D17 total score at week 8. In the primary efficacy analysis, a statistically greater change from baseline was observed in patients receiving Pristiq 50 mg and Pristiq 100mg compared with placebo. The most common treatment emergent adverse events observed were consistent with the known safety and tolerability profile of Pristiq.

Sexual function was assessed using the ASEX Scale. The ASEX was selected over other validated scales because it is a brief but sensitive tool, less burdensome to patients than a more in-depth scale, and has been utilised in previous trials for desvenlafaxine and other antidepressant drugs. It measures five core elements of sexual function (sexual drive, arousal, penile erection/vaginal lubrication, ability to reach orgasm, and satisfaction from orgasm) rated on a six-point Likert scale. A Likert scale is a psychometric scale commonly utilised in research that employs questionnaires. A total score is calculated as the sum of all 5 individual item scores; negative numbers for change from baseline indicate improvement in sexual function.

Incidence of sexual dysfunction was assessed using the ASEX data. In adult outpatients with MDD with baseline sexual activity and at least one post-baseline assessment, effects on ASEX total and item scores were comparable for the Pristiq 50 mg and Pristiq 100 mg groups and placebo. Rates of sexual dysfunction were comparable between each Pristiq dose and placebo at baseline (placebo, 52 per cent; Pristiq 50 mg/d, 56 per cent; Pristiq 100 mg/d, 54 per cent) and at week 8 (placebo, 45 per cent; Pristiq 50 mg/d, 49 per cent; Pristiq 100 mg/d, 47 per cent).

“The treatment and management of MDD in adults can be both complex and challenging for physicians and patients,” noted Dr. Salomon Azoulay, global clinical and medical affairs head, Pfizer Global Established Pharma. “As a science-based company, we continue to study Pristiq in order to provide clinicians with information that can help guide their treatment decisions and positive health outcomes for patients with MDD.”

Pristiq, a selective serotonin and norepinephrine reuptake inhibitor (SNRI), is a prescription medication that was approved by the US Food and Drug Administration (US FDA) in 2008 for the treatment of MDD in adults. The recommended dose for Pristiq is 50 mg once daily, with or without food. In clinical studies, doses of 50-400 mg/day were shown to be effective, although no additional benefit was demonstrated at doses greater than 50 mg/day and adverse events and discontinuations were more frequent at higher doses.