Author: Catherine Buckley, MD

This is a very quick, very dumbed down info session on acute Tylenol overdose based on a lecture from our 5 minute Toxicology sessions.


The most ideal ( for lack of a better word) Tylenol overdose presentation is a patient that is awake, alert and reports recent Tylenol overdose. However, more likely than not the patient may not be able to endorse the use of Tylenol, the time or the dose. They may be asymptomatic, or they may have nausea or vomiting. Or they may have coingestants clouding their presentation.


FIRST! Give activated charcoal!! Give 50g! This has proven efficacy if given within an hour of ingestion. And according to one of our excellent Toxicologists here at Rush- accurate use of activated charcoal will prevent your need for NAC. Which would be great! 

Now what is NAC you say? NAC IS AN ACTUAL ANTIDOTE!!! Which is very cool and magical and is best started by 8 hours from ingestion. So, you should go ahead and start the NAC if the ingestion time is unknown, the time is known but your lab results won’t come back by the 8 hour mark, or there is hepatotoxicity on labs.

Rumac- Matthew Normogram

If you think you can get your Tylenol level lab result back before hour 8 from the acute ingestion- please wait for the lab result.  If you wait for the lab result then you get to use the fancy-shmancy Rumac – Matthew line to decide to NAC or not to NAC. 

So let’s say you waited for the Tylenol result. The R-M line has a built in buffer. See, the dotted line is the science line. The solid line is the clinical line. So if you are below the solid line, I don’t care how close you are to it, if you are below the line then you do not have to give NAC! Even if you gave activated charcoal, that means it worked! And you can move on with patient’s other treatment needs.

Now, if you are on the line or above it, let’s talk about some options. 

  • You CAN do Oral NAC (if the patient is non-pregnant, has no hepatotoxicity on labs and is able to tolerate PO.) For oral NAC you give 140mg/kg loading dose followed by 17 doses of 70mg/kg Q4…. That’s 68 hours of (smelly) treatment. 
  • You can do IV NAC. If the patient’s INR is <2 then you can follow the 21 hour protocol. ( 150mg/kg over 60 minutes, then 50mg/kg over 4 hours, followed by 100mg/kg over 16 hours.) If the patient’s INR is >2 (sign of hepatic failure) then you should complete the 21 hour protocol and continue with 6.25 mg/kg/hr until the INR is less than 2. 

Now though we have all these protocols, you need to remember that every patient is an individual and may respond differently. So get some help from your neighborly toxicologist or poison control center- AND don’t stop the NAC treatment until the Acetaminophen level is undetectable, the LFTs are improving and the prognostic markers (Creatinine, lactate, pH, etc) are all looking better.


  • American College of Medical Toxicology. ACMT Position Statement: duration of NAC Therapy Following Acetaminophen Overdose. Journal of Medical Toxicology. (2017) 13: 126-127 
  • Yeates, P. Thomas, S. Effectiveness of delayed activated charcoal administration in simulated paracetamol (acetaminophen) overdose. Br. J clin Pharmacology. (2000) 49(1): 11-14

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