# A client with chronic back pain comes to the emergency department reporting that about 6 hours ago the client took an unknown number of acetaminophen 500 mg tablets after an argument. The client reports nausea and right upper quadrant discomfort and denies tinnitus or taking other medications. Vital signs: BP 118/72 mm Hg, HR 96/min, RR 18/min, temperature 36.8°C (98.2°F). The abdomen is soft without guarding. Laboratory results: acetaminophen level 145 mcg/mL (the nomogram treatment line is about 100 mcg/mL at 6 hours after ingestion), salicylate undetectable, AST 42 U/L (10-40), ALT 38 U/L (7-56), INR 1.2 (0.9-1.1), total bilirubin 1.1 mg/dL (0.1-1.2), lipase normal. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=617431&lang=en  
> language: en  
> subject: Medication Administration  
> category: PPT

## Question

A client with chronic back pain comes to the emergency department reporting that about 6 hours ago the client took an unknown number of acetaminophen 500 mg tablets after an argument. The client reports nausea and right upper quadrant discomfort and denies tinnitus or taking other medications. Vital signs: BP 118/72 mm Hg, HR 96/min, RR 18/min, temperature 36.8°C (98.2°F). The abdomen is soft without guarding. Laboratory results: acetaminophen level 145 mcg/mL (the nomogram treatment line is about 100 mcg/mL at 6 hours after ingestion), salicylate undetectable, AST 42 U/L (10-40), ALT 38 U/L (7-56), INR 1.2 (0.9-1.1), total bilirubin 1.1 mg/dL (0.1-1.2), lipase normal. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

Condition

Select 1
Acetaminophen poisoning above the treatment line
Subtoxic acetaminophen ingestion not needing an antidote
Acute cholecystitis
Salicylate toxicity

Actions to take

Select 2
Give activated charcoal by mouth now
Start the prescribed IV acetylcysteine infusion
Repeat the acetaminophen level in 4 hours before treating
Administer vitamin K for the INR of 1.2
Clarify the ingestion time and any co-ingestants

Parameters to monitor

Select 2
Serum lipase
Serial AST and ALT
Serum salicylate concentration trend
Serum potassium
INR and prothrombin time

## Explanation

A level of 145 mcg/mL at 6 hours lies above the nomogram treatment line (about 100 mcg/mL at 6 hours), so this is acetaminophen poisoning needing acetylcysteine now; the 150 mcg/mL figure applies only at 4 hours. The nurse starts IV acetylcysteine and clarifies the ingestion time and co-ingestants, because an earlier ingestion would make the level even more dangerous. AST/ALT and INR track liver injury.

## In-depth explanation

Quick answer
Acetaminophen poisoning above the treatment line; start IV acetylcysteine and clarify ingestion time and co-ingestants; monitor serial AST/ALT and INR.

Why this is correct
The nomogram compares the level with the hours since ingestion. At 6 hours the treatment line is roughly 100 mcg/mL, so 145 mcg/mL is well above it even though it is below the 4-hour value of 150. Early liver-enzyme and INR changes with nausea and RUQ pain are consistent with evolving hepatotoxicity. Acetylcysteine is most protective when started within 8 to 10 hours, so treatment should not wait, while an accurate time and co-ingestant history refines the risk assessment.

Easy analogy or mental picture
The nomogram line slopes downward like a descending staircase: a number that looks 'just under' the 4-hour step is actually far above the step you are standing on at 6 hours.

Memory hook
"Read the line at the right hour" — 150 at 4 h, about 100 at 6 h.

NCLEX decision rule
For acetaminophen overdose, plot the level against the actual time since ingestion; if it is above the line, or the time is uncertain with a detectable level, start acetylcysteine without delay and trend liver function.

Why the other choices are wrong
Activated charcoal is most useful within the first hours after ingestion and does not replace the antidote at 6 hours. Waiting 4 more hours pushes treatment past the most protective window. Vitamin K does not correct an INR rise caused by hepatocellular injury. Subtoxic ingestion is ruled out by reading the level against the correct time, cholecystitis by a soft abdomen, normal temperature, and normal lipase, and salicylate toxicity by an undetectable salicylate level and normal respirations. Lipase, salicylate, and potassium do not track acetaminophen liver injury.

References
1StatPearls — Acetaminophen Toxicity (NCBI Bookshelf)Levels plotted on the Rumack-Matthew nomogram guide acetylcysteine; charcoal is most useful early; AST/ALT and INR track hepatotoxicity.
2DailyMed — Acetylcysteine InjectionIV acetylcysteine is indicated to prevent or lessen hepatic injury after a potentially hepatotoxic acetaminophen ingestion.

## Clinical scenario

Scenario
About 6 hours after an intentional ingestion, the client's acetaminophen level is 145 mcg/mL with nausea, RUQ discomfort, and a slight rise in AST and INR.

## Key concepts

- **Rumack-Matthew nomogram** — A graph of serum acetaminophen level versus hours after a single acute ingestion used to decide whether acetylcysteine is needed.
- **N-acetylcysteine** — The antidote that replenishes glutathione to detoxify the harmful acetaminophen metabolite.
- **Hepatotoxicity** — Drug-induced liver injury, shown by rising AST/ALT, INR, and bilirubin.

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