Prolonged penile erections induced by hydroxyzine: possible mechanism of action.

We describe a subject who developed prolonged penile erections on hydroxyzine. Molecular modelling showed that the hydroxyzine metabolite, norchlorcyclizine, has structural and conformational similarities to the trazodone metabolite, m-chlorophenylpiperazine. This suggests that a common pharmacological mechanism may underlie the ability of trazodone and hydroxyzine to induce erections.