Melatonin-induced symptomatic bradycardia in an otherwise healthy male: a case report

Melatonin, a pineal gland hormone closely associated with the circadian rhythm, has been trending over the past years as an over-the-counter medication to aid with sleep disturbances. Although generally believed to be safe, recent studies show negative inotropic and chronotropic effects on the heart rate and blood pressure in humans. Several studies suggested that melatonin induces cardiac vagal tone and affects heart rate and mean arterial pressure. Limited literature is currently available on the effects of melatonin beyond its sleep function. We present a case of a healthy 22-year-old male who visited the emergency department reporting palpitations and dizziness following the ingestion of 20 mg of melatonin. Subsequent examinations revealed marked bradycardia. Fortunately, the patient experienced spontaneous resolution of the bradycardia without necessitating intervention after a few hours of observation, and he was observed and discharged.