Efficacy of isoproterenol for treating amlodipine overdose resulting in bradycardia.

Case: Amlodipine predominantly affects vascular smooth muscle cells. Amlodipine overdose usually presents with vasodilatory shock, accompanied by reflex tachycardia rather than bradycardia.An 81-year-old woman presented with impaired consciousness 8 h after ingesting 50 5-mg amlodipine tablets with suicidal intent. On admission, her blood pressure was 50/40 mmHg and her heart rate was 45 b.p.m. Serum amlodipine level was extremely high (474.4 ng/mL), causing refractory bradycardia. She remained hypotensive despite fluid resuscitation, and therefore was administered dopamine and norepinephrine. She was also administered glucagon and calcium gluconate, and underwent high-dose insulin euglycemic therapy.

Outcome: Although her blood pressure improved, bradycardia progressively worsened and isoproterenol infusion was initiated, which resulted in an improvement in her heart rate. The patient discharged on day 14 without any complications.

Conclusion: Isoproterenol is effective for treating bradycardia after amlodipine overdose.