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Modified Rumack-Matthew Nomogram and Calculator

The purpose of the calculator is to eliminate visual estimation as a means for determination of need for treatment.

Normal dose NAC dosing compared to theoretical higher dosing based upon modified Rumack-Matthew nomogram

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.


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.