**Core Concept**
Acetaminophen is a widely used analgesic and antipyretic drug, but its overdose can lead to severe liver damage due to the formation of a toxic metabolite.

**Why the Correct Answer is Right**
Hepatic necrosis is the most prominent toxic effect associated with acetaminophen use, occurring when the normal metabolic pathway for acetaminophen is overwhelmed, leading to the formation of N-acetyl-p-benzoquinone imine (NAPQI). NAPQI covalently binds to cellular proteins, causing mitochondrial damage and ultimately leading to hepatocyte death. The liver's glutathione stores are depleted, and once these stores are exhausted, NAPQI can cause irreversible damage to liver cells. This process is facilitated by the cytochrome P450 enzyme system, particularly CYP2E1.

**Why Each Wrong Option is Incorrect**
**Option A:** Respiratory alkalosis is a condition characterized by an elevated pH in arterial blood, typically caused by hyperventilation or other respiratory conditions. It is not directly related to acetaminophen toxicity.
**Option B:** Haemorrhage refers to bleeding from blood vessels, which is not a primary effect of acetaminophen overdose.
**Option D:** Gastric ulceration can be caused by nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin, but it is not a characteristic effect of acetaminophen toxicity.

**Clinical Pearl / High-Yield Fact**
In patients with acetaminophen overdose, early administration of N-acetylcysteine (NAC) can prevent liver damage by replenishing glutathione stores and scavenging NAPQI.

✓ Correct Answer: C. Hepatic necrosis