Acetaminophen overdose resident survival guide

# Overview
Acetaminophen overdose is the intentional or accidental ingestion of a high dose of acetaminophen.  Acute acetaminophen overdose occurs 8 hours before presentation, while chronic acetaminophen overdose occurs following the repeated supratherapeutic ingestion of acetaminophen.
Acetaminophen is available in the U.S. market under the following brand names:
- Tylenol
- Anacin-3
- Liquiprin
- Percocet
- Tempra
- Cold and flu medicines
- Aceta
- Actimin
- Apacet
- Aspirin Free Anacin
- Atasol
- Banesin
- Dapa
- Datril Extra-Strength
- Feverall
- Fibi
- Genapap
- Genebs
- Panadol

# Acetaminophen Dosage
Shown below is a table summarizing the commonly used dosages of paracetamol.
Shown below is a table summarizing the recommended maximum doses of paracetamol.

# Management

## General Approach
Shown below is an algorithm depicting the approach to acetaminophen overdose.

## Acetylcysteine Therapy
Shown below is an algorithm depicting the oral and IV regimen of N-acetylcysteine.

# Rumack-Matthew Nomogram

# Criteria for Liver Transplantation
- Arterial pH < 7.3
- Hepatic encephalopathy grade III/IV
- Serum creatinine concentration > 300 mol/L
- Prothrombin time > 100 seconds
- Arterial lactate concentration > 3.5 mmol/L on admission or > 3.0 mmol/L 24 hours after paracetamol ingestion

# Do's
- Measure serum acetaminophen concentrations between 4 and 16 hours post-ingestion. Values taken before 4 hours are not useful as it takes about 4 hours for maximal drug absorption. Likewise values taken after 16 hours are less useful as liver failure may have already occurred.
- Look for ketones on urinalysis and low blood urea concentration as a sign for malnourishment or starvation.
- In case of acetaminophen ingestion prior to 2 hours of the presentation, administer activated charcoal as it was found to be superior to gastric lavage and substance induced emesis, although both of them are potentially useful.
- N-acetylcysteine can be administered 8 hours following the ingestion of acetaminophen; however, it is most beneficial within the first 8 hours of ingestion.
- Provide a supportive treatment when needed: fluid replacement, symptomatic treatment for nausea and vomiting, intensive supportive treatment  in case of acute liver failure.
- If a patient vomits following oral N-acetylcysteine, administer a trial of anti emetic; however, in such cases IV N-acetylcysteine is preferred.
- Stop the infusion if IV N-acetylcysteine precipitates an anaphylactoid reaction, treat with H1-antihistaminics and resume IV N-acetylcysteine at a slower infusion rate.
- If acetaminophen level can not be obtained, assume that that patient has overdose of acetaminophen and treat with N-acetylcysteine.
- Consider liver transplantation if the patient has liver failure and meets the criteria for transplantation.

# Dont's
- Do not overlook acetaminophen in those who have signs suggestive of overdose with other agents.
- Do not use activated charcoal after 4 hours of acetaminophen ingestion.
- Do not delay treatment with antidote more than 8 hours following the ingestion of acetaminophen.
- Do not use the Rumack-Matthew nomogram to stratify patients who ingested acetaminophen more than 8 hours ago or whose history of ingestion is unclear.