Acetaminophen is the most important overdose in toxicology

Step 1: Check a Serum Acetaminophen Level

* Common situations where testing is ordered* Suicidal ideation* Severe depression* Overdose

Step 2: Consult the Rumack-Matthew nomogram

* Only works for acute/single ingestions of acetaminophen* Loses reliability if patient is on drugs that affect bowel motility* If the time of ingestion is KNOWN* Measure acetaminophen level 4 hours post-ingestion* Plot on nomogram and treat if above line* If time of ingestion is UNKNOWN* Determine earliest possible time of ingestion* Plot on nomogram and treat if above line

Step 3: Order hepatic labs (LFTs)

* AST* ALT* Alk Phos* PTT/PT/INR

Step 4: Identify Phase of Toxicity

* Phase 1/Day 1* High acetaminophen levels* Normal LFTs* Minimal symptoms* Phase 2/Day 2* Acetaminophen level starts decreasing* LFTs level starts increasing* Mild GI symptoms develop* Abdominal pain* Nausea/vomiting* Phase 3/Day 3* Acetaminophen levels are normalized* LFTs are peaking* Phase 4* Recovery

Step 5: Give N-Acetylcysteine (NAC)

* If patient meets criteria on Rumack-Matthew nomogram* If patient is in phase 1, 2, or 3

Additional Reading

* Acetaminophen Overdose and NAC Dosing (MDCalc)