Severe Hypotension After Amlodipine Use for Hypertension in a Newborn on Beta Blocker Therapy for Thyrotoxicosis

A 35-year-old woman with a 9-year history of Grave's disease delivered a male infant weighing 2,210 g at 32 weeks of gestation by caesarean section. The neonate developed thyrotoxicosis and, at the age of 24 h, was treated with oral carbimazole (500 µg every 8 h) and propranolol (2 mg/kg/day in two divided doses). He subsequently developed hypertension on day 4, which required therapy with amlodipine (0.1 mg once daily). Severe hypotension developed within 24 h and required discontinuation of amlodipine, with initiation of intravenous inotropic support with dopamine and dobutamine (at a rate of 20 µg/kg/min). The blood pressure rapidly normalized, and both dopamine and dobutamine infusions were stopped within 36 h. A Naranjo assessment score of 6 was calculated, indicating that the severe hypotension was a probable adverse drug reaction caused by the combination of amlodipine and propranolol therapy.