J Korean Soc Emerg Med.  2010 Jun;21(3):405-411.

A Case of Electrocardiographic and Mental Change in a Patient with a Diphenhydramine Overdose

• Park CS
• Kang IG
• Ryu HS
• Park SS
• Lee MJ
• Jeong WJ

Abstract

The antihistaminic drug diphenhydramine is mainly used as a sedative, hypnotic and antiemetic. In many countries it is available over-the-counter, very common, and generally regarded as a harmless drug. However, diphenhydramine overdose can result in cardiotoxicity due to its ability to block fast sodium channels in a manner analogous to classic Vaughan-Williams type IA antidysrhythmic agents. As such, cardiotoxicity from diphenhydramine resembles that of the tricyclic antidepressant agents. Here we report a case of a 52 year old man who ingested 2,000 mg of diphenhydramine and presented with an altered mental state and an electrocardiographic change. His electrocardiogram showed sinus tachycardia with a rate 145 beat/min, a QRS interval of 88 ms, and a QTc of 556 ms. He had a wide anion gap metabolic acidosis. He was treated with intravenous sodium bicarbonate and supportive therapy. His clinical manifestations waned and he was transferred to another hospital nearby his hometown.

Keyword

Diphenhydramine; Electrocardiography; Sodium bicarbonate; Acidosis; Overdose

MeSH Terms

Acid-Base Equilibrium
Acidosis
Diphenhydramine
Electrocardiography
Humans
Sodium Bicarbonate
Sodium Channels
Tachycardia, Sinus
Diphenhydramine
Sodium Bicarbonate
Sodium Channels