What is the antidote used for amitriptyline toxicity?

Sodium bicarbonate is the antidote for amitriptyline toxicity due to its ability to mitigate the cardiotoxic effects associated with tricyclic antidepressant overdose, including arrhythmias, by alkalinizing the serum and shifting the equilibrium of the drug in the cardiac tissues. Amitriptyline can cause significant cardiac conduction disturbances, and the administration of sodium bicarbonate helps to stabilize the cardiac membrane and can improve the pH levels in the blood, thereby reducing the toxicity.

In cases of overdose, the alkalizing effect of sodium bicarbonate can enhance the excretion of the drug through urine and can counteract metabolic acidosis, a common complication of prolonged toxicity. This makes sodium bicarbonate the recommended treatment in managing serious cases of amitriptyline overdose.

The other options listed do not serve as effective antidotes for amitriptyline toxicity. Flumazenil is a benzodiazepine antagonist, not relevant in tricyclic overdose management. Pyridoxine is primarily used for treating certain types of seizures and ethylene glycol poisoning, while Vitamin K is involved in coagulation and does not address the toxicity related to amitriptyline.