Unintentional cetirizine overdose causing anticholinergic syndrome.

The incidence of anticholinergic syndrome due to second generation antihistamines is infrequently reported. Largely due to their decreased affinity for central nervous system (CNS) receptors, second generation antihistamines are rarely associated with anticholinergic symptoms, though toxicity is still possible particularly when taken in excess. We report a case of a six year old boy who presented with agitation, hallucinations, fixed and dilated pupils, tachycardia, and hyperthermia consistent with anticholinergic toxicity several hours after accidental overdose of a second generation antihistamine, cetirizine. Early identification of this rare phenomenon is important not only for appropriate emergency management but also for avoidance of potentially invasive and unnecessary tests which may further increase patient morbidity.