Purpose: Diphenhydramine (DPH), an over-the-counter first-generation H1 receptor antagonist, is not a common drug of abuse; however, it is encountered in cases of overdose both in the clinical setting and in death investigations. The toxicology laboratories in the Tarrant County Medical Examiner's Office and the District of Columbia Office of The Chief Medical Examiner analyze antemortem and postmortem specimens. Presented are the findings of this evaluation and detailed histories of cases involving DPH.
Methods: Toxicology reports, autopsy reports, and death investigator narratives were obtained in cases involving DPH at toxic and lethal levels in which this compound was the primary cause or a contributing factor in the death.
Results: Blood concentrations were quantified at a range of 2870 to 21,263 ng/mL. A rare occurrence of DPH abuse via documented intravenous administration leading to death is presented. The cases presented here generally involved much higher concentrations of DPH and an older population than those in previous published data regarding DPH's role in death investigation and abuse.
Conclusions: As people seek legal alternative drugs to abuse and with the ease of obtaining information via online forums, there is a potential to see an increase in the number of cases involving excessive use of DPH.