Apomorphine-induced penile tumescence in impotent patients--preliminary findings

Apomorphine (Apo), a short acting dopamine (DA) receptor agonist induces penile erections in normal subjects. The erectile response to one or more doses of Apo HCl (0.25, 0.5, 0.75, 1.0 mg sc) or placebo was investigated in eight impotent subjects and penile tumescence monitored using a mercury strain gauge and strip chart recording. Four patients showed a full erection with Apo and one a partial response. Distressing side effects (nausea, sweating) were associated with non-response or partial response. Three responders to Apo were treated with low doses of the long acting DA receptor agonist, bromocriptine (2.5-3.75 mg/d po); all three showed complete recovery of erectile function within two weeks. A subgroup of impotent patients may have impaired central DA function. Testing with Apo may provide a diagnostic and predictive test to identify such patients who may respond to treatment with low doses of bromocriptine or other DA receptor agonist.