Dose-dependent toxicity of diphenhydramine overdose

Background: Diphenhydramine (DPHM) overdose is a frequent cause of acute poisoning. Although its clinical features are well known, information about the dose dependent toxicity of DPHM is still scarce. The objective of this study was to investigate the dose-dependent toxicity of DPHM in patients with acute DPHM poisoning.Methods: We have analyzed retrospectively all well-documented cases with DPHM monointoxications reported by physicians to the Swiss Toxicological Information Centre (STIC) between January 1984 and April 1996. In addition, a prospective study focusing on ingested DPHM doses and severity of symptoms was performed between May 1996 and December 1998.Results: The retrospective and prospective studies included 232 and 50 patients with DPHM monointoxications, respectively. In both studies, mild symptoms (somnolence, anticholinergic signs, tachycardia, nausea/vomiting) occurred in 55-64%, moderate symptoms (isolated and spontaneously resolving agitation, confusion, hallucinations and ECG disturba...