**Core Concept**
Amitriptyline is a tricyclic antidepressant (TCA) that can cause severe poisoning due to its anticholinergic and cardiotoxic effects. The management of amitriptyline poisoning involves supportive care, decontamination, and specific antidotes to counteract its toxic effects.

**Why the Correct Answer is Right**
In the case of amitriptyline poisoning, gastric lavage or activated charcoal administration is recommended to prevent further absorption of the drug. **Option C: Administer activated charcoal** is a correct management strategy. Another effective approach is to use a specific antidote, such as sodium bicarbonate, to help alkalinize the urine and enhance the elimination of the drug. **Option A: Administer sodium bicarbonate** is also a recommended treatment. In addition, close monitoring of the patient's cardiac rhythm and vital signs is essential, and **Option B: Perform a 12-lead ECG** is an important step in the management of amitriptyline poisoning.

**Why Each Wrong Option is Incorrect**
**Option D:** Administer physostigmine is incorrect because physostigmine is a cholinesterase inhibitor that can worsen the anticholinergic effects of amitriptyline, leading to increased toxicity.

**Clinical Pearl / High-Yield Fact**
In cases of TCA poisoning, it is essential to monitor the patient's cardiac rhythm closely, as QRS prolongation is a common sign of toxicity. A QRS interval greater than 100 ms is a red flag for severe TCA poisoning.

**Correct Answer: D. Administer physostigmine. Physostigmine is not recommended in the management of amitriptyline poisoning.**