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?

1 N-acetylcysteine (NAC) ✓ Correct answer
2 Naloxone
3 Vitamin K
4 Activated 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.

In-depth explanation

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.

Master the NCLEX-RN with MyMerci

Thousands of NCLEX-style questions with detailed rationale — in your language. Track your progress and study smarter.

Start for free

App Store Google Play

Read in another language: English 한국어 日本語繁體中文 Tiếng Việt

For study reference only. Always follow current clinical guidelines and your institution’s protocols.

성장을 멈추지 마세요

In-depth explanation

Clinical scenario

Key concepts

Master the NCLEX-RN with MyMerci