Unintentional cetirizine overdose causing anticholinergic syndrome

Area of Science:

• Pharmacology
• Toxicology
• Pediatrics

Background:

• Second-generation antihistamines are designed for reduced central nervous system (CNS) penetration, minimizing anticholinergic side effects.
• Anticholinergic syndrome is rarely associated with these newer antihistamines due to lower affinity for muscarinic receptors.

Observation:

• A six-year-old boy experienced agitation, hallucinations, fixed dilated pupils, tachycardia, and hyperthermia.
• Symptoms appeared several hours after an accidental overdose of cetirizine, a second-generation antihistamine.

Findings:

• The case demonstrates that anticholinergic toxicity can occur with second-generation antihistamines, particularly in overdose scenarios.
• Cetirizine overdose in a child mimicked classic anticholinergic toxidrome.

Implications:

• Early identification of antihistamine-induced anticholinergic syndrome is crucial for effective emergency management.
• Recognizing this rare toxicity can prevent unnecessary diagnostic procedures and associated patient morbidity.