Priapism as a rare adverse effect of levomepromazine: A case report

Abstract

BACKGROUND

Priapism is a rare but potentially serious adverse effect of antipsychotic therapy, largely attributed to peripheral α1-adrenergic receptor blockade. Reports specifically involving levomepromazine remain scarce.

CASE SUMMARY

We report the case of a 45-year-old man with schizophrenia who presented with a persistent, painless penile erection lasting eight hours, 48 hours after initiation of levomepromazine at 100 mg/day. He had no previous history of priapism, known hematological disorder, trauma, recreational drug use, or exposure to other potentially causative medications. Corporal blood gas analysis revealed profound hypoxia and acidosis [pH 6.831, partial pressure of oxygen (PO₂) 8 mmHg, partial pressure of carbon dioxide (PCO₂) 84 mmHg], confirming severe ischemic priapism despite the absence of penile pain. Corporal aspiration and intracavernosal phenylephrine failed to achieve satisfactory detumescence. Persistent ischemia ultimately required surgical intervention with a proximal cavernospongiosal Quackels shunt, resulting in immediate and complete detumescence. Levomepromazine was discontinued, and the patient was discharged after an uneventful two-day hospitalization. A review of previously reported cases revealed only limited evidence of levomepromazine-associated priapism, with substantial heterogeneity in treatment exposure, predisposing factors, clinical presentation, and management.

CONCLUSION

Levomepromazine-associated ischemic priapism is a rare but potentially severe adverse drug reaction. This case demonstrates that profound cavernosal ischemia may develop rapidly after treatment initiation and may occur despite the absence of penile pain. Clinicians prescribing antipsychotics with substantial α1-adrenergic antagonistic activity should remain aware of this complication. Prompt recognition and guideline-directed management are essential to minimize irreversible cavernosal injury and subsequent erectile dysfunction.

Keywords: Priapism; Levomepromazine; Antipsychotics; Ischemia; Phenothiazines; Case report

Core Tip: Levomepromazine-associated priapism is rarely reported despite the drug’s substantial α1-adrenergic antagonistic activity. This case is notable for the development of severe ischemic priapism only 48 hours after initiation of levomepromazine monotherapy at a therapeutic dose, with complete absence of penile pain despite profound cavernosal hypoxia and acidosis. Failure of intracavernosal phenylephrine ultimately required surgical shunting. This observation emphasizes that absence of pain does not exclude severe ischemia and that persistent erections during antipsychotic therapy require prompt evaluation and treatment to prevent irreversible cavernosal injury.