An adolescent case of doxylamine-induced widening of QRS complex

Doxylamine is an over-the-counter first-generation antihistamine used in the treatment of allergies and insomnia. Intentional ingestion is common due to its wide availability. Toxicity most frequently presents as an anticholinergic toxidrome with central effects leading to delirium, psychosis, or seizures, and peripheral effects manifested as tachycardia, dry and warm skin, mydriasis, or urinary retention. First-generation antihistamines can have antagonistic properties against the sodium channels on the cardiac myocytes in supratherapeutic doses. This article reports a polysubstance ingestion of 2 antihistaminergic agents with development of QRS complex widening and a right bundle branch block, which has not been well described in the literature.