Hypersensitivity-like reactions to N-acetylcysteine.

This report describes nine episodes of presumed allergic reactions occurring in seven patients who were treated for acetaminophen overdose with intravenous N-acetylcysteine. All of these reactions were confined to the skin and consisted of urticaria and/or angioedema. All patients were pruritic. There was no evidence of bronchospasm or hypotension. In four of these episodes the intravenous protocol was completed after the parenteral administration of an antihistamine. In all four of these instances there was no progression of the hypersensitivity-like symptoms or signs. Previous case reports of acute allergic reactions to intravenous N-acetylcysteine will be reviewed. The advantages and disadvantages of oral vs. intravenous N-acetylcysteine therapy for acetaminophen overdose will be discussed in light of the hypersensitivity-like reactions to intravenous N-acetylcysteine.