Sir,
A recent article by MR Safarinejad published in Neuropsychopharmacology contained results from a randomized, double-blind, placebo-controlled trial of dapoxetine for the treatment of premature ejaculation (PE) (Safarinejad, 2008). In this publication, and in a related article published previously by the same author, (Safarinejad, 2006) several major differences are noted compared to the phase III studies used to investigate the safety and efficacy of dapoxetine (Pryor et al, 2006).
In the Safarinejad trial, dapoxetine 30 mg or placebo was administered twice daily (b.i.d.) for 12 weeks to men with PE. This dosing schedule seems inconsistent with the pharmacokinetic profile of dapoxetine. Dapoxetine is a short-acting selective serotonin reuptake inhibitor (SSRI) that is rapidly absorbed. Maximum serum concentrations (Cmax) are reached ∼1 h after oral administration, and serum levels of dapoxetine are rapidly reduced, with a decline in plasma concentrations to approximately 5% of peak levels by 24 h (Modi et al, 2006). Given the rapid absorption and elimination of dapoxetine, dosing of dapoxetine is most appropriate within 1–3 h of sexual intercourse, which would increase the probability of the subject benefiting from treatment. The Safarinejad article states only that participants were instructed to take dapoxetine every 12 h, and no information is provided as to whether the participants took dapoxetine shortly before anticipated sexual intercourse.
In the Discussion section of the article, Dr Safarinejad points out several times that dapoxetine did not exhibit long-term efficacy 3 months after stopping treatment. There is no pharmacologic agent for the treatment of PE that has been shown to have continued, long-term efficacy after discontinuation. The American Urologic Association Guidelines on the Management of Premature Ejaculation state that ‘Therapy for PE most likely will be needed on a continuing basis. There is no clear consensus as to whether SSRIs will effect an eventual cure of PE, allowing for discontinuation of the medication, or whether SSRIs will be required for life. The Panel members' experience is that PE usually returns upon discontinuing therapy’ (Montague et al, 2004). In summary, the differences in the design of this study, as well as the unrealistic expectations regarding post-treatment efficacy call into question the conclusions of this study.
References
Modi NB, Dresser MJ, Simon M, Lin D, Desai D, Gupta S (2006). Single- and multiple-dose pharmacokinetics of dapoxetine hydrochloride, a novel agent for the treatment of premature ejaculation. J Clin Pharmacol 46: 301–309.
Montague DK, Jarow J, Broderick G, Dmochowski RR, Heaton JP, Lue TF et al (2004). AUA guideline on the pharmacologic management of premature ejaculation. J Urol 172: 290–294.
Pryor JL, Althof SE, Steidle C, Rosen RC, Hellstrom WJG, Shabsigh R et al (2006). Efficacy and tolerability of dapoxetine in the treatment of premature ejaculation: integrated analysis of two randomized, double-blind, placebo-controlled trials. Lancet 368: 929–937.
Safarinejad MR (2006). Comparison of dapoxetine versus paroxetine in patients with premature ejaculation: a double-blind, placebo-controlled, fixed-dose, randomized study. Clin Neuropharmacol 29: 243–252.
Safarinejad MR (2008). Safety and efficacy of dapoxetine in the treatment of premature ejaculation: a double-blind, placebo-controlled, fixed-dose, randomized study. Neuropsychopharmacology 33: 1259–1265.
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Consultant to and/or speaker for Johnson & Johnson, Pfizer, Lilly, GlaxoSmithKline, and Bayer.
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Sharlip, I. Rational use of Dapoxetine for the Treatment of Premature Ejaculation. Neuropsychopharmacol 33, 2785 (2008). https://doi.org/10.1038/npp.2008.11
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DOI: https://doi.org/10.1038/npp.2008.11