A client is admitted to the emergency department after inges… | MyMerci
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Adverse Effects/Contraindications/InteractionsPPT
Question
A client is admitted to the emergency department after ingesting an unknown amount of acetaminophen approximately 4 hours ago. The serum acetaminophen level is plotted above the treatment line on the Rumack-Matthew nomogram. Which medication should the nurse anticipate administering to prevent hepatotoxicity?
1Naloxone
2N-acetylcysteine (NAC)✓ Correct answer
3Vitamin K
4Activated charcoal
Explanation
N-acetylcysteine (NAC) is a glutathione precursor that detoxifies NAPQI, the toxic metabolite of acetaminophen, preventing hepatic necrosis. NAC is most effective within 8 hours of ingestion but remains beneficial up to 24 hours. Naloxone reverses opioid overdose. Vitamin K reverses warfarin-induced coagulopathy. Activated charcoal is effective only within 1 hour of ingestion.
Clinical Judgment The Rumack-Matthew nomogram guides treatment for acetaminophen overdose. A serum level above the treatment line at 4 hours indicates risk of hepatotoxicity and mandates immediate N-acetylcysteine (NAC) therapy. Activated charcoal has limited utility beyond 1 hour post-ingestion.
Memory Tip APAP poisoning → NAC (N-Acetylcysteine neutralizes the toxin)
KR vs US US standard: IV NAC 21-hour protocol (150 mg/kg loading + 50 + 100). Korea also uses IV NAC; some centers historically used oral methionine, now largely replaced by IV NAC.
Clinical scenario
Clinical Practice Guide The American College of Medical Toxicology (ACMT) and AASLD recommend IV NAC for any acetaminophen level above the treatment line on the Rumack-Matthew nomogram. Standard dosing: 150 mg/kg loading over 60 min, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours.
Caution Activated charcoal is only effective if administered within 1 hour of acetaminophen ingestion. After this window, NAC remains the priority intervention. Do not delay NAC waiting for a repeat level if the treatment line is exceeded.
Key concepts
N-acetylcysteine (NAC) — Glutathione precursor that conjugates NAPQI, the toxic acetaminophen metabolite. Standard antidote for acetaminophen overdose. IV protocol: 150 mg/kg loading, then 50 mg/kg over 4h, then 100 mg/kg over 16h.
NAPQI — N-acetyl-p-benzoquinone imine. Toxic intermediate metabolite produced when acetaminophen overwhelms glutathione conjugation. Causes centrilobular hepatic necrosis if not detoxified.
Rumack-Matthew nomogram — Plot of serum acetaminophen concentration against time post-ingestion (4-24h). Treatment line starts at 150 mcg/mL at 4 hours. Levels above this line require NAC therapy.