# 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?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=362720&lang=en  
> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## 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?

## Option

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

**Correct answer: 2**

## 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.

## Related questions

- [A nurse is reviewing the morning lab results for an adult client receiving warfarin for at…](https://mymerci.kr/pages/nclex_q.php?qn_id=360515&lang=en)
- [A client with chronic heart failure is prescribed metoprolol 25 mg orally twice daily. Bef…](https://mymerci.kr/pages/nclex_q.php?qn_id=362756&lang=en)
- [A 28-year-old client with type 1 diabetes receives regular insulin 6 units and NPH insulin…](https://mymerci.kr/pages/nclex_q.php?qn_id=362792&lang=en)
- [A client receives IV vancomycin 1 g every 12 hours for MRSA bacteremia. Before the next do…](https://mymerci.kr/pages/nclex_q.php?qn_id=362833&lang=en)
- [A client with bipolar disorder has been taking lithium carbonate 600 mg orally three times…](https://mymerci.kr/pages/nclex_q.php?qn_id=362894&lang=en)
- [An 80-year-old male with heart failure is prescribed digoxin 0.125 mg daily. During mornin…](https://mymerci.kr/pages/nclex_q.php?qn_id=372686&lang=en)
- [A 38-year-old female with rheumatoid arthritis is being discharged with a new prescription…](https://mymerci.kr/pages/nclex_q.php?qn_id=372687&lang=en)
- [A 62-year-old patient is being discharged after a deep vein thrombosis and will continue e…](https://mymerci.kr/pages/nclex_q.php?qn_id=372707&lang=en)

## Read in another language

- [en](https://mymerci.kr/pages/nclex_q.php?qn_id=362720&lang=en)
- [ko](https://mymerci.kr/pages/nclex_q.php?qn_id=362720&lang=ko)
- [ja](https://mymerci.kr/pages/nclex_q.php?qn_id=362720&lang=ja)
- [zh-TW](https://mymerci.kr/pages/nclex_q.php?qn_id=362720&lang=zh-tw)
- [vi](https://mymerci.kr/pages/nclex_q.php?qn_id=362720&lang=vi)

---

More free questions: [NCLEX-RN Practice](https://mymerci.kr/pages/nclex_bank.php?lang=en)

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