**Core Concept**
Amitriptyline is a tricyclic antidepressant (TCA) with a narrow therapeutic index. In cases of overdose, it can cause severe anticholinergic toxicity, cardiac arrhythmias, and seizures. Managing TCA poisoning requires a multi-faceted approach, including supportive care and specific antidotes.

**Why the Correct Answer is Right**
Atropine is not an antidote for amitriptyline poisoning. In fact, administering atropine in this scenario can worsen the anticholinergic effects of the drug, such as tachycardia, dry mouth, and mydriasis. The primary goal of treatment is to manage the life-threatening complications of TCA overdose, including cardiac arrhythmias and seizures.

**Why Each Wrong Option is Incorrect**
* **Option A:** Sodium bicarbonate infusion is a recommended treatment for TCA poisoning to help alkalinize the urine and promote the excretion of the drug. It can also help manage cardiac arrhythmias.
* **Option B:** Gastric lavage may be considered in cases of recent ingestion, but its effectiveness is limited, and it should not delay other treatments. Activated charcoal can be given to reduce absorption.
* **Option C:** Diazepam is an appropriate treatment for seizures associated with TCA poisoning. Benzodiazepines are effective in managing seizure activity and can help reduce the risk of status epilepticus.

**Clinical Pearl / High-Yield Fact**
In cases of TCA poisoning, it's essential to monitor cardiac rhythm and manage arrhythmias promptly. Sodium bicarbonate, magnesium, and phenytoin may be used to manage cardiac complications, while benzodiazepines are used to control seizures.

**✓ Correct Answer: D. Atropine as antidote**