Final answer:
The antidote for quinidine or TCA toxicity is d) sodium bicarbonate, which helps correct metabolic acidosis and reduce the cardiotoxic effects by increasing drug binding.
Step-by-step explanation:
The antidote for quinidine or tricyclic antidepressants (TCA) toxicity is sodium bicarbonate. Quinidine and TCAs can lead to cardiotoxicity and sodium bicarbonate is used to combat this by correcting the associated metabolic acidosis, and by increasing the pH, it enhances the protein binding of the drugs thereby reducing their bioavailability and effects on cardiac cells. Protamine sulfate is an antidote for heparin, Vitamin K is for warfarin overdose, and physostigmine is used to treat anticholinergic toxicity, such as atropine poisoning. It's worth noting that muscarinic agonists like physostigmine are indeed the antidote to atropine poisoning, thereby providing a clue from the list and emphasizing the proper antidote to quinidine and TCA toxicity within the choices given.