An acetaminophen toxicity nomogram plotting serum concentration of acetaminophen against the time since ingestion in an attempt to prognosticate possible liver toxicity as well as allowing a clinician to decide whether to proceed with N-Acetylcysteine (NAC) treatment or not.
The logarithmic graph starts from 4 hours post ingestion after absorption is considered likely to be complete.
Allows for timely management of acetaminophen overdose.
A serum plasma concentration (APAP) of 140-150 microgram/mL (or milligrams/L) at 4 hours post ingestion, indicates the need for NAC treatment.
This nomogram is not used alone if the patient has altered mental status or if the history is not reliable, but a second level should be drawn and plotted to see if the slope of the line remains at or above the nomogram.
A formal half life may also be determined, and half-life calculated:If half-life is more than 4 hours, then treatment is necessary to prevent hepatotoxicity and liver failure.
The treatment line was created starting at 150 at 4 hours and is the usual line used in the United States to determine treatment of acetaminophen overdose.