Naftopidil inhibits 5-hydroxytryptamine-induced platelet aggregation and 5-hydroxytryptamine uptake in platelets of healthy volunteers

Naftopidil exerts its antihypertensive action via α1-adrenoceptor blockage and Ca2+ antagonism in vascular smooth muscle. Since the chemically similar 1-(1-naphthyl) piperazine is known to be a 5-hydroxytryptamine2 receptor antagonist, the 5-hydroxytryptamine (5-HT) antagonistic properties of naftopidil were tested by examining 5-HT-induced aggregation and 5-HT uptake in platelets from 12 healthy volunteers after oral administration of 60 mg naftopidil or placebo.