Drug-Induced Priapism Its Aetiology, Incidence and Treatment

Abstract

Priapism is characterised by a persistent erection that cannot be relieved by sexual intercourse or masturbation. Although priapism subsides spontaneously in a few days, impotence frequently follows. Both vascular and neural mechanisms are implicated in the pathophysiology of priapism, but it is not clear which initiates the process. Idiopathic cases of priapism are the most frequent (near 50%); other medical conditions that can result in priapism are haematological diseases (mainly sickle cell anaemia and leukaemia), traumatism, and neoplastic processes. Drug-induced priapism comprises about 30% of cases. The drugs most frequently implicated are psychotropic drugs (phenothiazines and trazodone), antihypertensives (mainly prazosin) and heparin. Recently, the intracavernosal injection of vasoactive drugs (papaverine and phentolamine) has been described in patients treated for impotence. With the exception of heparin, an alpha-adrenergic blocking mechanism has been suggested in the priapism-inducing action of these drugs. A significant number of anecdotal case reports link priapism and drugs, and it is possible that certain cases of idiopathic priapism could be reclassified if accurate pharmacological anamnesis were to be performed. Priapism must be considered a urological emergency. Surgical procedures are the most preferred treatment for this condition but, in selected cases, drug treatment seems to be an alternative approach.

Medical Therapy for Benign Prostatic Hyperplasia: A Review of the Literature

“…In most of these studies prazosin increased urinary flow above that achieved by placebo, and was associated with a lower incidence of the undesirable effects of α–blocker therapy in comparison to earlier less selective agents (phenoxybenzamine). However, it was still associated with drowsiness, weakness, headache, postural hypotension and syncope (especially following the initial dose) [24], and has been linked to priapism in numerous case reports [29]. Prazosin is taken twice daily.…”

Selective Enhancement of Contractions to α1-adrenergic Receptor Activation in the Aorta of Mice With Sickle Cell Disease

“…20 First, local administration of phenylephrine and other α-adrenergic agents often prove efficacious in aborting priapism that fails to respond to conservative measures 20 ; we suggest that such efficacy reflects the enhanced α1-adrenergic vasoconstriction that exists in the vasculature in SCD, thereby leading to decreased penile blood flow. Second, the use of antihypertensive agents in SCD, especially prazosin, increases the risk for priapism in SCD 21 ; in our studies, prazosin completely blocked the contractile response to phenylephrine and norepinephrine.…”

Priapism

“…Neuroleptics with notable α‐blocking activity include the butyrophenones (haloperidol) and phenothiazines (chlorpromizine, fluphenazine), antidepressants (trazodone particularly) and many other drugs 14,15 . Local injection of vasoactive drugs such as phentolamine (an‐blocker), papaverine (direct vasodilator) and PGE 1 (raises adenyl cyclase and relaxes vascular smooth muscle) are now widely and effectively used to treat impotence.…”

“…The majority of cases of priapism have been classed as idiopathic 8,10,14,15 . In retrospect many of these “idiopathic” cases may have been druginduced.…”