Melanotan II overdose associated with priapism

To the Editor:

We read the brief communication by Nelson et al. regarding the sympathomimetic effects of Melanotan II in the December issue of Clinical Toxicology and have several questions.¹ We recently cared for a similar patient self-experimenting with Melanotan II. We were consulted on a 60-year-old man who had subcutaneously injected 10 mg of Melanotan II into his abdomen. Within 30 minutes of injection, he developed a painful erection. Like Dr Nelson's case, our patient presented with a sympathomimetic toxidrome. His heart rate was 113 beats/min; his blood pressure was 142/81. He was agitated and intensely diaphoretic despite a normal temperature. He complained of a compulsive “need to stretch” and exhibited an odd back-arching behavior. Laboratory evaluation was significant only for a mild leukocytosis (WBC 12.4) with a bandemia (10%), anion gap (13), and elevated creatinine (1.35 mg/dL; baseline, 1.04 mg/dL). He had no clinical or laboratory evidence of rhabdomyolysis. Treatment of his priapism with subcutaneous terbutaline was unsuccessful. Similarly, corporal aspiration, corporal irrigation, and corporal instillation of 50 μg of phenylephrine failed to achieve detumescence. Ultimately, the patient required surgical intervention – a Winter's shunt was placed, resolving the priapism. He required several doses of diazepam and lorazepam for agitation. His vital signs normalized after 6 h of benzodiazepine therapy. At the end of a 24-h observation period, he was asymptomatic and discharged to home. At 4-month follow-up, he was asymptomatic except for a residual hyperpigmented patch at the injection site.

Although “unrelenting erection” has been reported, we are not aware of melanotropic peptides causing priapism.² Did Dr. Nelson's patient exhibit any penile erectile abnormalities after the 6 mg dose? Additionally, did his patient‘s agitation include any back-arching behavior? We ask these questions because the preclinical literature on melanocortins documents lordotic posturing in rodents administered these compounds.^3,4 This behavior has been interpreted as evidence of increased sexual arousal.⁴ We are wondering whether another neurochemical effect is occurring and whether Dr. Nelson's patient exhibited evidence of this abnormal neuromuscular activity as the precipitator of his rhabdomyolysis.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.