Acetaminophen level

Background

• Serum acetaminophen (APAP) concentration; essential in any intentional ingestion or unknown overdose

Normal Values

• Therapeutic: 10-20 mcg/mL
• Toxicity assessment: plot on Rumack-Matthew nomogram at 4 hours post-ingestion

Interpretation

• Draw level at 4 hours post-ingestion (or immediately if >4 hours); use Rumack-Matthew nomogram to determine need for N-acetylcysteine (NAC)
• Treatment line: 150 mcg/mL at 4 hours (some use lower 100 mcg/mL line for added safety)
• Check APAP level on all intentional ingestions regardless of reported substance (co-ingestion is common)
• Undetectable level at >4 hours after acute ingestion essentially rules out toxic ingestion
• Chronic/repeated supratherapeutic ingestion: nomogram does not apply; treat based on level, AST/ALT, and clinical picture

See Also

• Acetaminophen toxicity
• N-acetylcysteine