Case Study 1: Dapoxetine Wins The Race
Delayed ejaculation is an adverse effect of selective serotonin re-uptake inhibitors (SSRIs) in men. Dapoxetine (marketed as Priligy, a short-acting SSRI, is the first drug to be marketed for premature ejaculation.
After oral administration, peak plasma concentrations of Dapoxetine are reached after an hour. Elimination is relatively rapid and the terminal half-life is approximately 19 hours.
There have been several randomized controlled trials of dapoxetine for premature ejaculation. The primary outcome for most of the trials was ‘intravaginal ejaculatory latency time’ measured by the partner using a stopwatch.
An analysis of a trial, in which 2614 men (aged 18–77 years) were randomized to dapoxetine (30 mg or 60 mg) or placebo (all taken 1–3 hours before intercourse), found that dapoxetine increased intravaginal ejaculatory latency time significantly more than placebo. At baseline, men were required to have an intravaginal ejaculatory latency time of 2 minutes or less at least 75% of the time. After 12 weeks, 29% of men taking the 30 mg dose and 34% taking the 60 mg dose had a latency time of 3 minutes or more. This was compared to only 14% of men taking placebo. Men taking dapoxetine perceived that they had better control of ejaculation and were more satisfied with their sexual performance than those taking placebo.
During the trial, nausea (11%), headache (5.6%), diarrhoea (3.5%), somnolence (3.1%) and dizziness (5.8%) were more commonly reported with dapoxetine 30 mg than with placebo. These events were dose-related – all of them were more frequent with the 60 mg dapoxetine dose. Nausea and dizziness were the most common reasons for discontinuation with dapoxetine 30 mg. Because of the increased risk of adverse events, patients should be warned to take no more than one tablet in a 24-hour period.
Dapoxetine is contraindicated in patients with heart problems such as heart failure, conduction abnormalities or significant ischaemic or valvular disease. It is also contraindicated in moderate and severe hepatic impairment. Dapoxetine is not recommended in patients with severe renal impairment or with psychiatric disorders.Although dapoxetine prolongs intravaginal latency time before ejaculation, improvements seem modest and a placebo effect was apparent in most of the studies.