A 66-year-old woman with a history of chronic alcohol abuse has had headaches and nausea for the past 4 days. She has become increasingly obtunded. On physical examination, she has right upper quadrant tenderness, tachycardia, tachypnea, and hypotension. Laboratory studies show serum AST of 475 U/L, ALT of 509 U/L, alkaline phosphatase of 23 U/L, total bilirubin of 0.9 mg/dL, albumin of 3.8 g/dL, and total protein of 6.1 g/dL. She is treated with N-acetylcysteine. Which of the following drugs has she most likely ingested in excess?

## **Core Concept**
The patient presents with symptoms and laboratory findings suggestive of acute liver failure, which is characterized by coagulopathy, encephalopathy, and significant elevation of liver enzymes. The key to this question lies in identifying the substance that can cause liver damage and is treated with N-acetylcysteine (NAC).

## **Why the Correct Answer is Right**
The patient is treated with N-acetylcysteine, which is a specific antidote for acetaminophen (paracetamol) overdose. Acetaminophen toxicity is a common cause of acute liver failure, especially in the setting of chronic alcohol abuse, which can induce cytochrome P450 enzymes and increase the formation of the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). The patient's presentation with elevated AST and ALT, but relatively preserved albumin levels, and the absence of significant cholestasis (normal alkaline phosphatase and bilirubin), points towards a hepatocellular injury pattern consistent with acetaminophen overdose.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain drugs can cause liver injury, the specific treatment with NAC points directly to acetaminophen overdose, making other hepatotoxic drugs less likely.
- **Option B:** Similarly, other substances can cause liver damage but are not specifically treated with NAC.
- **Option C:** This option is a distractor and does not relate directly to the treatment provided or the common causes of acute liver failure in this context.
- **Option D:** This option is incorrect because the clinical scenario and treatment provided specifically suggest acetaminophen overdose.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that N-acetylcysteine is administered in acetaminophen overdose and works by replenishing glutathione stores, which help detoxify NAPQI. Early administration of NAC is crucial in preventing liver damage. It's also important to note that chronic alcohol use can increase the risk of acetaminophen-induced liver injury.

## **Correct Answer: .**

✓ Correct Answer: A. Acetaminophen