The Rumack-Matthew nomogram is a well studied and validated tool to help assess the potential for liver toxicity following acute acetaminophen poisoning. Here is a brief review of when it is best utilized.
Prior to 4 hours post-ingestion: Not helpful to determine likelihood for toxicity. Only use is to confirm an ingestion took place.
Between 4 and 24 hours post-ingestion: Plot the patient's level vs. time after ingestion. If above the toxicity line, treat with acetylcysteine.
More than 24 hours post-ingestion: Any elevated acetaminophen level is toxic and should be treated with acetylcysteine.
Outside-the-box situations:
Chronic exposures: Nomogram not indicated.
Overdoses with co-ingestants that slow GI motility (e.g., opioids, diphenhydramine) OR extended release products (e.g., Tylenol Arthritis): If the level at 4 hours post-ingestion is not toxic, repeat it at 8 hours post-ingestion. If either level is toxic, treat with acetylcysteine.
