Drug-induced myocarditis precipitated by amlodipine overdose: a case report

Background: Amlodipine is the most commonly prescribed calcium channel blocker (CCB), used in the treatment of a variety of cardiovascular conditions. Calcium channel blockers remain a well-established cause of cardiovascular drug overdose. We present the case of an intentional overdose with 250 mg of amlodipine resulting in acute left ventricular dysfunction and myocarditis.
Case summary: A 46-year-old man with no significant past medical history presented to the emergency department 8 h after intentionally ingesting 250 mg of amlodipine. Although initially asymptomatic with unremarkable physical examination, the patient developed progressively worsening dyspnoea over the next 2 days. Subsequent findings from chest X-ray, electrocardiogram, echocardiogram, and cardiac magnetic resonance imaging (MRI) were consistent with a diffuse myocarditis process with severe left ventricular systolic dysfunction. The patient was managed with diuretics and discharged once stable.
Discussion: Our case highlights myocarditis as a potential complication of CCB overdose. Amlodipine is the most commonly prescribed CCB and is associated with cardiac toxicity at high doses. The long duration of action and high volume of distribution of amlodipine further increase the risk of morbidity and mortality from overdose. Known cardiac complications of amlodipine overdose include bradycardia, myocardial depression, and pulmonary oedema secondary to heart failure; however, diffuse myocarditis is a complication that has not previously been described in the literature. The mechanism of development of this complication remains unclear.