Persistent Penile Erection (Priapism) Associated With Quetiapine and Lithium

To the Editor: Priapism is an emergency condition in which a painful erection lasts more than 4 (or 6) hours despite that physical or psychological stimulation is not present. Treatment-induced priapism is thought to be related to vasoconstriction in the corpus cavernosum induced by blockade of α1- and α2-adrenergic receptors. The condition is infrequent (incidence ranges from 0.34 to 1.5 cases per 100,000 men).¹ Treatment with antipsychotics is one of the priapism risk factors, particularly for antipsychotics with high α1 affinity (e.g., chlorpromazine and clozapine).² Other mechanisms include neurological (e.g., spinal cord lesions) and vascular (e.g., sickle cell anemia, leukemia, and thalassemia) factors. Priapism can also result from illicit drugs. We present a case of treatment-induced priapism in a patient with bipolar disorder treated with quetiapine and lithium.

Case Report

“Mr. B” is a 28-year-old man with bipolar disorder treated with quetiapine (1000 mg/day) and lithium (300 mg/day). He reported to a urologist because of a painful, long-lasting (approximately 5 hours) penile erection. Doppler ultrasound examination revealed no blood flow abnormalities in the penis vessels. He received 600 mg of acetylsalicylic acid, 0.8 mL nadroparin (low-molecular-weight heparin; 9500 anti-Xa IU/mL), and a sedative agent. After excluding other causes, it was decided that priapism was induced by quetiapine, and the medication was discontinued. Regular blood, urine, and biochemical tests and a neurological examination were normal. We decided to increase the dose of lithium to 1125 mg/day (blood level of 0.67 mmol/L) and not to introduce other medications. No recurrence of priapism was observed during further treatment, when, because of recurring mild psychotic symptoms, first olanzapine (up to 7.5 mg/day, withdrawn due to excessive sedation) and then aripiprazole (currently 15 mg/day) were administered.

Discussion

Almost all antipsychotics have been reported to rarely cause priapism due to their α-adrenergic antagonism,³ even after a single dose.⁴ There are no reports of priapism induced by lithium alone. Using the Naranjo Adverse Drug Reaction Probability Scale,⁵ a score of 7 for quetiapine was found (a probable adverse drug reaction to the drug). Clinicians should be cautious about it due to severe consequences of delayed treatment of this adverse reaction.