Lifelong premature ejaculation: definition, serotonergic neurotransmission and drug treatment.

The ejaculation distribution theory (EDT) postulates a biological continuum of the intravaginal ejaculation latency time (IELT) in men. Such an continuum has recently been found in two epidemiological stopwatch studies. In addition, a continuum of ejaculation latency time has also been demonstrated in laboratory rats. It is suggested that the invariable parts of ejaculation, i.e. premature and retarded ejaculation are highly influenced by genetic and neurobiological factors. In contrast, superimposed on biological roots, ejaculation of men, in the middle part of the continuum, is probably more easily influenced by environmental and psychological factors. A meta-analysis of 35 daily SSRI and clomipramine treatment studies demonstrated a similar efficacy for paroxetine, clomipramine, sertraline and fluoxetine, with paroxetine exerting the strongest effect on ejaculation. Based on fundamental insights into serotonergic neurotransmission, it is suggested that on-demand conventional SSRI treatment will not lead to similarly impressive ejaculation delay as that found after daily conventional SSRI treatment. Future studies with SSRIs with short half-lives, short T(max) and high C(max )should elucidate whether these pharmacokinetic properties are able to affect the pharmacodynamics of 5-HT neurons in such a way that immediate clinically relevant ejaculation delay occurs.