Acetominophen Overdose

This article described emergency care for a 17-year-old woman who overdosed on Excedrin PM. She had anorexia nervosa and took the medication occasionally to fall asleep. Her mother found her unconscious and estimated that she had taken 50 tablets.

Unresponsiveness appeared due to the CNS-depressant effects of the diphenhydramine. The critical concern was hepatotoxicity. Emergency care included IV naloxone (Narcan) for the decreased respiratory and cognitive status, vital signs monitoring, gastric lavage , activated charcoal and N-acetylcysteine (NAC).

Each Excedrin PM tablet contains acetaminophen 500 mg and diphenhydramine citrate (Benadryl) 38 mg. For adults, the average lethal dose for acetaminophen is 7.5 grams; a lethal dose of diphenhydramine is about 2.8 grams. Half a bottle means 25 grams of acetaminophen and 1.9 grams of diphenhydramine

Acetaminophen figures in a high proportion of intentional and accidental drug overdoses. It is converted in the liver to a metabolite that can cause hepatic necrosis by binding to liver cells.

Ethanol consumption, malnutrition, and short-term fasting deplete glutathione which increases susceptibility to hepatotoxicity.

Early (within 30 minutes of ingestion) acetaminophen toxicity is marked by anorexia, nausea, and vomiting due to local GI effects, but can be asymptomatic. In 24 hours, abdominal pain, liver tenderness, elevated hepatic enzymes, and oliguria are likely. Complications include hypotension, renal failure, acidosis, hemorrhage, and hypoglycemia. For those who survive, liver damage resolves in four days to two weeks.

This patient survived and received counseling.

(McDonough, J. Acetaminophen overdose. Am J Nurs 1998;98(3):52)

COMMENT: Teens self-medicate without knowledge of drug action or side effects. Often labels are difficult to read and understand. Television ads may be misleading and offer little education about drugs. School nurses are well-positioned to question students about the medicines they take and to explain proper use. This patient had special problems that lead to misuse.
Contributor — Kathleen Bryan RN, CFNP.