The purpose of the calculator is to eliminate visual estimation as a means for determination of need for treatment.
As per review of the literature, higher dose n-acetyl-cysteine (NAC) may be of benefit for patients with sub-massive and massive APAP overdose. More NAC means more glutathione, which means more capacity to detoxify the toxic metabolite of APAP, n-acetyl-para-benzoquinone imine (NAPQI). This modified nomogram gives theoretical recommendations for levels at which increased NAC doses may be considered.
Furthermore, 4-methylpyrazole (aka, fomepizole) is strong inhibitor of CYP2E1 and may decrease the rate at which NAPQI is formed. Therefore, 4-methylpyrazole may be considered as a safe adjunctive therapy in sub-massive and massive APAP overdoses.
This calculator and nomogram are intended for educational purposes only. This nomogram and calculator have not been clinically validated.
References:
Hazai E, Vereczkey L, Monostory K. Reduction of toxic metabolite formation of acetaminophen. Biochem Biophys Res Commun. 2002;291(4):1089-1094.
Hendrickson RG. What is the most appropriate dose of N-acetylcysteine after massive acetaminophen overdose? Clin Toxicol (Phila). 2019;57(8):686-691.
White SJ, Rumack BH. The acetaminophen toxicity equations: “solutions” for acetaminophen toxicity based on the rumack-matthew nomogram. Annals of Emergency Medicine. 2005;45(5):563-564.