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Buenos Aires, Argentina--The serotonin transport inhibitor dapoxetine appears to be a well-tolerated and effective agent for the treatment of premature ejaculation, according to the results of a phase II study presented at the International Society for Sexual and Impotence Research world congress.
Researchers say the drug, which is still investigational, may offer a safer, more tolerable alternative to the selective serotonin reuptake inhibitors (SSRIs) currently used to treat this common sexual condition.
The randomized, double-blind, placebo-controlled trial enrolled 166 adult, heterosexual men with a baseline intravaginal ejaculatory latency time (IELT, as measured by a stopwatch held by the female partner) <2 minutes (mean time, 1.01 minutes). Subjects were randomized to initial treatment with dapoxetine, 60 mg or 100 mg taken 1 to 2 hours prior to anticipated sexual activity, or placebo. Patients were crossed over to both alternate treatments. Treatment periods lasted 2 weeks and were separated by a 72-hour washout period.
Efficacy was immediate, as well. After the first dose, mean change from baseline IELT was 0.33 minutes for placebo; 1.52 minutes for dapoxetine, 60 mg; and 1.39 minutes for dapoxetine, 100 mg (60 mg vs. placebo, p=.014; 100 mg vs. placebo, p=.025).
Ten patients-one taking placebo and nine receiving dapoxetine, 100 mg-withdrew from the study due to adverse events. However, the 60-mg dose of dapoxetine was well tolerated and associated with a relatively low incidence of minor side effects.
Based on the phase II results, phase III studies were conducted to investigate dapoxetine, both 30 mg and 60 mg, and some preliminary results from those investigations are encouraging, said lead author Wayne J.G. Hellstrom, MD, professor of urology and chief, section of andrology, at Tulane University Health Sciences Center in New Orleans.
"Considering the favorable efficacy and safety profile demonstrated so far for dapoxetine, we look forward to this novel agent as being the first medication approved by the FDA for the treatment of premature ejaculation," he said.
A common problem Dr. Hellstrom noted there is a genuine need for modalities to treat premature ejaculation, as it is one of the most common types of male sexual dysfunction, affecting up to 30% of men at some time in their lives, and can be a psychologically disturbing condition for men and their partners.
Compared with SSRIs Current management of premature ejaculation usually involves off-label use of an antidepressant SSRI, such as paroxetine (Paxil), sertraline (Zoloft), or fluoxetine (Prozac).
"Like the SSRIs, dapoxetine prolongs the time to ejaculation through a central effect on the serotonin system," Dr. Hellstrom said. "However, dapoxetine is very short acting-less than 4% of the parent compound or its metabolites are still present in the body after 24 hours. And it has a much more favorable safety profile."
To be eligible for participation in the phase II study, men had to be 18 to 65 years of age; in a stable, monogamous, sexual relationship for at least 6 months; have no concomitant erectile dysfunction or use of SSRIs; and have no history of major psychiatric disorders.
In addition, both the patient and partner had to be willing to attempt sexual intercourse at least twice weekly. About 75% of enrolled men were 30 to 49 years of age, and 80% were Caucasian.