THE EFFECTS OF A NEW ALPHA-2-ADRENOCEPTOR ANTAGONIST ON SLEEP AND NOCTURNAL PENILE TUMESCENCE IN NORMAL-MALE VOLUNTEERS AND MEN WITH ERECTILE DYSFUNCTION

The effects of a new alpha-2 adrenoceptor antagonist, RS 15385, on sle ep and nocturnal penile tumescence (NPT) was assessed by intravenous i nfusion of the drug, in two doses (high-and low), and of placebo throu gh the night in 12 young normal volunteers and 24 men with erectile dy sfunction. The drug reduced total sleep time in the younger normal vol unteers only with the high dose and in the dysfunctional men with both doses. There was no selective effect on different sleep stages in the normal volunteers, except for an increase in the per cent of total sl eep time in Stage 1 with the high dose. The dysfunctional men were div ided into two age groups (<47 years and >47 years). There was an age-r elated increase in the proportion of total sleep in rapid eye movement (REM), which was only apparent in the older age group. In the volunte ers, there was a curvilinear dose-response effect on NPT. The lower do se modestly increased erectile response, particularly during non-REM s leep, whereas the higher dose reduced erectile response, most noticeab ly during REM. The only positive effect of the higher dose was an incr ease in spontaneous erections after lights out before sleep onset. The older dysfunctional group showed no drug effects on NPT. The younger dysfunctional men showed increased erectile response during non-REM wi th the higher dose, an effect that was also significant in the interva l between sleep onset (Stage 2) and first REM.