Probable drug-induced clitoral priapism due to potentiating effects of pregabalin and duloxetine.

Purpose: The following case report discusses probable clitoral priapism secondary to duloxetine and pregabalin. While this is a rare adverse effect, it is possible given the mechanism of action and potentiating effects of the combined therapy. This adverse drug reaction was reported to MedWatch and shows that additional research into the physiology of clitoral erection is warranted given the scarcity of information on how drugs influence this reaction.

Summary: A 53-year-old African American female with uncontrolled anxiety was started on duloxetine. Pregabalin was added 1 month later due to continued feelings of anxiety. Three weeks later, the patient reported symptoms of clitoral pain, as well as a swollen, tender, and erect clitoris. These adverse effects remained for 4 days, prompting the patient to present to the emergency department where a physical exam was completed with no significant finding except as noted above. Pregabalin was immediately discontinued by the attending physician based on the probability that the swelling was likely drug-induced clitoral priapism. During follow-up, the patient continued to note clitoral erection and pain. The psychiatric pharmacist tapered off duloxetine over 2 weeks with resolution of symptoms. In an examination of the mechanism of action of both drugs, pregabalin can amplify duloxetine's inhibitory effects on voltage-dependent calcium channels. It is likely this mechanism that causes smooth muscle relaxation and led to clitoral priapism.

Conclusion: This case suggests that pharmacological agents affecting vasoconstriction through serotonergic receptors or calcium-dependent channels can also influence clitoral erection.