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 sleep and nocturnal penile tumescence (NPT) was assessed by intravenous infusion of the drug, in two doses (high and low), and of placebo through the night in 12 young normal volunteers and 24 men with erectile dysfunction. The drug reduced total sleep time in the younger normal volunteers 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 sleep time in Stage 1 with the high dose. The dysfunctional men were divided into two age groups (< 47 years and > 47 years). There was an age-related increase in the proportion of total sleep in rapid eye movement (REM), which was only apparent in the older age group. In the volunteers, there was a curvilinear dose-response effect on NPT. The lower dose modestly increased erectile response, particularly during non-REM sleep, whereas the higher dose reduced erectile response, most noticeably during REM. The only positive effect of the higher dose was an increase 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 with the higher dose, an effect that was also significant in the interval between sleep onset (Stage 2) and first REM.