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Updated: Feb 3, 2026

Author Spotlight: A Unique Mouse Model of Asphyxia-Induced Cardiac Arrest
Published on: April 14, 2023
Cardiac arrest caused by diphenhydramine overdose
Tomoya Nishino1, Shinjirou Wakai1, Hiromichi Aoki1
1Department of Emergency and Critical Care Medicine Tokai University School of Medicine Isehara Kanagawa Japan.
Case:
A 45-year-old man presented to our emergency department with disturbance of consciousness; he had mentioned to his family earlier about a drug overdose. When first responders arrived, he suffered cardiac arrest. Cardiac arrest due to drug overdose was diagnosed.The patient was supported with venoarterial extracorporeal membrane oxygenation. Arterial blood gas showed mixed acidosis, and electrocardiogram showed junctional rhythm and complete right bundle branch block.
Outcome:
The patient's blood pressure gradually decreased, and he died on the third day of hospitalization. After death, his serum diphenhydramine concentration at the time of arrival was found to be 18.7 μg/mL.
Conclusion:
Although diphenhydramine is regarded as a safe medication, it shows dose-dependent toxicity. High intake is associated with death; therefore, caution should be exercised in cases of drug overdose. Developing a procedure for rapid measurement in the emergency department should be a priority.
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