Clinical question: Does a shorter regimen of IV acetylcysteine reduce adverse effects compared to the standard regimen?
Background: Acetaminophen poisoning is common, and recommended treatment is IV acetylcysteine; however, the standard regimen has many adverse effects, including vomiting and anaphylactoid reactions. Although studies have outlined these side effects, no published trials have compared their frequency to that of a shorter protocol.
Study design: Double-blinded, randomized controlled trial.
Setting: Three acute care hospitals in the United Kingdom.
Synopsis: Of 3,311 patients who presented with acetaminophen overdose, 222 underwent randomization to the standard (duration 20-25 hours) or modified (12 hours) acetylcysteine regimen, with or without pre-treatment with IV ondansetron 4 mg. The primary outcome of vomiting, retching, or need for rescue antiemetic treatment within two hours of acetylcysteine initiation was significantly less frequent in patients who received the shorter regimen, compared to those allocated to the standard regimen.
Specifically, the adjusted odds ratio was 0.26 with the modified regimen (97.5% CI, 0.13-0.52; P<0.0001). The primary outcome was significantly less in patients pre-treated with ondansetron compared to placebo (OR 0.41, 97.5% CI 0.2-0.8; P=0.003). Anaphylactic reactions were significantly reduced with the shorter protocol; no significant difference in hepatotoxicity was noted.
It is reasonable to infer that the shorter acetylcysteine regimen substantially reduces the frequency of vomiting and serious anaphylactoid reactions when compared with the standard schedule; however, hospitalists should note that this study was not powered to assess for non-inferiority of the shorter regimen with regard to prevention of acetaminophen’s hepatotoxic effects. Further studies are needed to confirm the efficacy and safety of the modified regimen before widespread adoption into clinical practice.
Bottom line: A shorter acetylcysteine regimen is associated with decreased occurrence of vomiting and anaphylactoid reactions compared to the standard protocol for treating acetaminophen toxicity. Additional research is needed to assess non-inferiority of this modified regimen for prevention of hepatotoxic effects.
Citation: Bateman DN, Dear JW, Thanacoody HK, et al. Reduction of adverse effects from intravenous acetylcysteine treatment for paracetamol poisoning: a randomized controlled trial. Lancet. 2014;383(9918):697-704.