Self-treatment of acetaminophen overdose with dietary-supplement acetylcysteine

Acetylcysteine is well known as an antidote for acetaminophen poisoning, but it is also marketed as a dietary supplement and touted as an antioxidant, metal chelator, and antiviral. Dietary-supplement acetylcysteine is available in capsules or tablets, each containing 500–1000 mg of the drug. Bottles containing 60–1200 capsules or tablets are priced at $10–100 by health food stores and online vendors. The recommended dose of dietary-supplement acetylcysteine is generally one or two capsules or tablets once or twice daily. Use of acetylcysteine as an antidote for acetaminophen overdose is described by many online sources such as Wikipedia, Medscape, and chat rooms.1,2 Self-treatment of acetaminophen overdose is not advised by these sources, but the following case illustrates how easily this may occur. A 33-year-old 130-kg man with a history of alcohol abuse came to the emergency department (ED) five days after allegedly ingesting 15 acetaminophen 500-mg tablets (total, 7.5 g) in one day for back pain. He became concerned about acetaminophen toxicity, and after researching acetylcysteine on the Inter-net, he took 60 600-mg tablets of dietary-supplement acetylcysteine (36 g total, 277 mg/kg) over the three or four days before coming to the ED. In comparison, FDA-approved labeling for acetylcysteine given orally for acetaminophen overdose indicates a dosage of 1330 mg/kg over 72 hours.3 On arrival at the ED, the patient’s acetaminophen and salicylate concentrations were undetectable, and results of liver function tests were normal (serum aspartate transaminase, 22 units/L; serum alanine transaminase, 34 units/L; serum total bilirubin, 0.9 mg/dL; International Normalized Ratio, 1.1), but he was acidotic (serum carbon dioxide, 16 mg/dL; anion gap, 17 meq/L) and had renal impairment (blood urea nitrogen, 46 mg/dL; serum creatinine, 6.5 mg/dL). The patient was admitted for supportive care and received no additional acetylcysteine. His renal function improved during hospitalization, with the serum creatinine concentration dropping to 1.8 mg/dL 10 days after acetaminophen ingestion. It is unclear whether self-administration of acetylcysteine affected his outcome.