Acetaminophen Overdose and NAC Dosing
Calculates PO/IV NAC dosing for acetaminophen overdose (and nomogram to determine toxic 4 hour level).
When to Use
When to use the Rumack-Matthew nomogram:
- Acute, single ingestions (where entire ingestion occurs within an 8-hour period).
- A known time of ingestion.
- Immediate release formulation.
- Absence of formulations or coingestants that alter absorption and bowel motility (e.g., anticholinergics, opioids).
- An acetaminophen concentration obtained prior to 4 hours post-ingestion cannot be plotted on the Rumack-Matthew nomogram, and only confirms acetaminophen exposure, not toxicity.
- Get an accurate time of ingestion: the Rumack-Matthew nomogram is entirely dependent on knowing time of ingestion.
- Start NAC treatment within 8 hours post-ingestion to decrease the risk of hepatotoxicity (AST or ALT > 1000 IU/L).
- In patients presenting 8-24 hours post-ingestion, start NAC while awaiting the acetaminophen concentration; once this is resulted, NAC can be continued or discontinued depending on the level.
- The Rumack-Matthew nomogram is the most sensitive risk prediction tool in medical toxicology.
- It identifies patients at very low risk of developing hepatotoxicity after acetaminophen overdose and who do not require NAC.
- All patients above the nomogram line should be treated with NAC to decrease the risk of developing hepatotoxicity. (See More Info section)