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Question answered:26/09/06 Warning! this question is over two years old.
In 2005 the National Horizon Scanning Centre, University of Birmingham, prepared a briefing report on dapoxetine hydrochloride for premature ejaculation in which discusses the drug’s mechanism of action:
“Dapoxetine hydrochloride (AP 38) - Janssen-Cilag, is a SSRI in development for the management of premature ejaculation. Its mechanism of action is to increase the level of serotonin in the central nervous system. An observed, and usually adverse, effect of SSRIs is a delay in ejaculatory latency time although the precise mechanism of action is unknown. Dapoxetine has a rapid onset of action of approximately 1.5 hours and a short half-life and the company anticipate a dose of 30 or 60mg 1-3 hours before intercourse not to be taken more frequently than once every 24 hours. A US application for licence was submitted in December 2004. The earliest UK launch is anticipated to be in 2007.” [1]
On the 9th of September 2006, the “Lancet” published the results of two double-blind trials of dapoxetine which found the SSRI improved intravaginal ejaculatory latency time compared to placebo. Concerning how the drug might work, the author’s Pryor et al suggest:
“The underlying pathophysiology of premature ejaculation is not completely understood, although both physiological and psychological components could contribute to the condition. Psychopharmacological studies suggest that premature ejaculation might be related to diminished serotonergic neurotransmission through pathways that control ejaculation. Dapoxetine is a short acting SSRI developed specifically for the treatment of premature ejaculation. The drug's mechanism of action is thought to be related to inhibition of neuronal reuptake of serotonin and subsequent potentiation of serotonin activity. By contrast with SSRIs approved for depression, which take 2 weeks or longer to reach steady-state concentration, dapoxetine has a unique pharmacokinetic profile, with a short time to maximum serum concentration (about 1 h) and rapid elimination (initial half-life of 1-2 h). By 24 h, plasma concentrations are less than 5% of peak values. These attributes make dapoxetine suitable for on-demand therapy.” [2]
References
1. National Horizon Scanning Centre. Dapoxetine hydrochloride for premature ejaculation. January 2005. (http://www.pcpoh.bham.ac.uk/publichealth/horizon/PDF_files/2005reports/Dapoxetine.pdf).
2. Pryor JL, Althof SE, Steidle C et al for the Dapoxetine Study Group. Efficacy and tolerability of dapoxetine in treatment of premature ejaculation: an integrated analysis of two double-blind, randomised controlled trials. The Lancet - Vol. 368, Issue 9539, 09 September 2006, Pages 929-937. Full text access to this article requires an ATHENS password.
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