Towards evidence-based drug treatment research on premature ejaculation: a critical evaluation of methodology

In the last decade, an increasing number of drug studies on premature ejaculation have been published. The methodology used in these studies differed widely. In this review, it is therefore questioned as to how far the differences in methodology could have influenced clinical outcomes. The aim of the present review was to compare the different methodologies that were used in drug studies on premature ejaculation. The majority of these studies were conducted between 1973 and 2003 and were strikingly different in study design and in the quantification of clinical outcomes. It appeared that in some of these studies, placebo and active drug effects were neglected due to an erroneous methodology. The few studies that were using stopwatch assessment at each intercourse at baseline and during treatment and in which the intravaginal ejaculation latency time (IELT) was included appeared to be comparable in their results. The use of a well-defined definition of premature ejaculation, for example, an IELT of less than 1 min revealed reproducible results. Finally, the retrospective use of a questionnaire or a subjective report on ejaculation time induced higher effects with regard to placebo effects and an underestimation of active drug effects. In conclusion, for drug treatment research of premature ejaculation it is recommended to use a randomized double-blind prospective design, the use of the IELT, the use of a stopwatch at each coitus both during a baseline period and during drug treatment and a definition of premature ejaculation as an ejaculation that occurs within 1 min after vaginal penetration.