Incidence and management of N-acetylcysteine-related anaphylactoid reactions during the management of acute paracetamol overdose

Abstract

Adverse drug reactions (ADRs) to N-acetylcysteine (NAC) treatment for paracetamol overdose are typically anaphylactoid in origin and occur in 2-48% of treated patients. We explored the incidence and management of NAC ADR in our unit. Case notes of patients who presented with paracetamol overdose and had ADR to NAC between February 2005 and June 2011 were reviewed. A total of 1648 patients presented with suspected paracetamol overdose and 660 received NAC treatment. Within this group, 82 patients had documented NAC-related ADR. ADR developed in 12.4% (82/660) of patients receiving intravenous NAC and 59 had full documentation available and were included in this study (34 women, 25 men). ADR occurred in the 15-min (150 mg/kg) bag in 36 cases (61%), 22 in the 4-h (50 mg/kg) bag (37%) and one in the 16-h (100 mg/kg) bag (2%). Symptoms were classified as minimal (n=16, 27%), moderate (n=26, 44%) and severe (n=17, 29%). Asthma and female sex, which are reported risk factors for ADR, did not lead to the development of more severe ADR (P=0.771 and 0.330, respectively). Treatments administered included stopping the NAC infusion (n=32, 54%), administration of antiemetics (n=36, 61%), H1 antihistamines (n=26, 44%), steroids (n=16, 27%), inhaled B2 agonists (n=6, 10%) and adrenaline (n=3, 5%). The incidence of ADR to NAC was comparable with published studies, although there was no association of severity with asthma or female sex. The management of ADRs is variable, with frequent, inappropriate use of steroids. Education about the pathophysiology of these ADRs may improve management.