Acute Intentional Antihistamine Poisoning in the Emergency Department: Predictors of Anticholinergic Symptoms Predictors of Anticholinergic Symptoms
International Journal of Medical Toxicology and Forensic Medicine,
Vol. 16 (2026),
29 December 2025
,
Page 1-8
https://doi.org/10.22037/ijmtfm.v16.51253
Abstract
Background: Antihistamines are widely used for allergic and respiratory conditions, but can cause severe toxicity when taken in overdose. Differences in pharmacokinetic properties between first and second-generation agents influence clinical presentation and outcomes. This study aimed to describe the epidemiological and clinical features of intentional antihistamine poisonings in patients consulting our emergency department (ED) in Tunisia and to identify drug-specific and dose-specific associations with anticholinergic symptoms.
Methods: A retrospective study was conducted at the ED of the Mahmoud Yaacoub Center for Urgent Medical Assistance in Tunis from January 2021 to July 2024. Patients presenting with acute intentional antihistamine poisoning were included. Epidemiological and clinical data were analyzed using univariate and multivariate logistic regression to identify independent predictors of anticholinergic symptoms.
Results: Among 134 included cases (median age 24 years; 83.6% female), most involved H1-antihistamines (91.8%), predominantly first-generation agents (58.6%). Cyproheptadine (32.1%) and chlorpheniramine (9.7%) were the most frequently implicated first-generation drugs, while cetirizine (23.9%) was the most common second-generation agent. Symptomatic presentations occurred in 47% of patients, being more common and more severe with first-generation drugs than second-generation (69.8% vs 25.4%, p<0.001). Cyproheptadine poisoning was associated with tachycardia (P=0.034, OR=2.441) and toxic psychosis (P=0.032, OR=6.206), with a cutoff dose of ≥108 mg determinant for toxic psychosis (P=0.025, OR=12.73). Chlorpheniramine was linked to sedation (P=0.022, OR=5.43) and hypotension (P=0.043, OR=16.38). ICU admission occurred in 9.7% of cases, and 2 patients required mechanical ventilation. The majority of patients (73.1%) were discharged home, and 12.7% were referred for psychiatric evaluation.
Conclusion: Most intentional antihistamine poisonings resulted in mild or no symptoms; first-generation agents, particularly cyproheptadine and chlorpheniramine, were linked to more severe toxicity and consequences. Recognition of dose thresholds and drug-specific clinical patterns can guide early management in acute antihistamine poisoning.
- Anticholinergic syndrome, Antihistamine, Emergency Medicine, Intoxication, Predictive factors
How to Cite
References
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