Acetaminophen poisoning nomogram

This nomogram should only be used after a single acute acetaminophen ingestion. The line indicates the level at which toxicity is possible after acetaminophen overdose. A serum acetaminophen level should be obtained four or more hours after an ingestion to ensure that a peak level has occurred. Patients who ingest extended-release preparations should have a second level drawn four hours after the first level to assess for an additional rise in serum concentration. The level should be plotted in relationship to the time of ingestion to determine the likelihood of toxicity and the need for treatment. Caution should be used in assessing the reliability of the time of ingestion. This nomogram cannot be used for ingestions that occurred greater than 24 hours prior to presentation, repeated supratherapeutic oral ingestions, or iatrogenic intravenous overdose.