What is the specific antidote for Tricyclic Antidepressant (TCA) poisoning?

The specific antidote for Tricyclic Antidepressant (TCA) poisoning is sodium bicarbonate. This is primarily due to the fact that TCAs can cause cardiotoxic effects, particularly by leading to cardiac arrhythmias and metabolic acidosis. Sodium bicarbonate acts by alkalinizing the plasma and stabilizing myocardial membranes, which helps prevent these potentially life-threatening cardiac effects.

In cases of TCA overdose, the administration of sodium bicarbonate can also improve the function of the sodium channels affected by the drug's toxicity. This is particularly significant because TCAs inhibit sodium channels, leading to a wider QRS complex on an electrocardiogram (ECG). By using sodium bicarbonate, there can be a significant reduction in the length of the QRS interval, making it a critical intervention in severe cases.

The other options do not serve as specific antidotes for TCA poisoning. For example, Digoxin immune Fab is used for digoxin toxicity, N-acetylcysteine is a specific antidote for acetaminophen toxicity, and Flumazenil is a benzodiazepine antagonist that might precipitate seizures in TCA overdose. Thus, sodium bicarbonate's unique action makes it the recognized treatment for TCA poisoning