Background and objectives: Intravenous
N-acetylcysteine (IV-NAC) is widely recognized as the antidote of choice for
acetaminophen overdose [1]. However, its use is not without adverse drug
reactions (ADR) which might affect therapeutic outcome or lead to treatment
delay [2, 3]. The aims of this study were to investigate the type and incidence
of ADR induced by IV-NAC in patients treated for acetaminophen overdose and to
assess the causality of individual ADR to IV-NACusing Naranjo's algorithm [4].
Methods:
This is a retrospective study of patients admitted to the hospital for acute
acetaminophen overdose over a period of 5 years (January 1, 2004 to December
31, 2008). The primary outcome of interest in this study was the occurrence of
ADR during NAC administration. The probability of an ADR was assessed using the
Naranjo algorithm, which consists of 10 questions), and has been used to
determine the likelihood that an ADR was related to a specific medication [4].
Results:
During the study period, 305 patients with a diagnosis of overdose of
paracetamol-containing compounds were admitted to the hospital for monitoring
and treatment. Different types of ADR occurred in 137 patients (137/305;
44.9%). Of those patients who had an ADR, 98 (98/137; 71.5%) had been treated
with IV-NAC and 39 (39/137; 28.5%) had not(p < 0.001). Comparison of
different ADR in all patients showed that the following ADR were significantly
associated with IV-NAC administration: nausea (p = 0.004), vomiting (p <
0.001), flushing (p < 0.001), rash (P < 0.001), pruritus (p < 0.001),
chest pain (p = 0.001), bronchospasm (p = 0.015), coughing (p = 0.017),
headache (p < 0.001), dizziness (p < 0.001), convulsion (p = 0.035) and
hypotension (p = 0.001). Based on Naranjo’s algorithm, 226 events were judged
to be NAC-related – 31.1% probably and 67.9% possibly drug-related. None of the
events were definitely drug-related. Conclusion: Adverse drug reactions
to IV-NAC were common among patients with acetaminophen overdose but mostly
minor, and that all reported adverse reactions were easily managed.