Which antidote - drug pair is incorrect?

• A. Leucovorin - Methotrexate
• B. Phytomenadione - Warfarin
• C. Physostigmine - Benzodiazepines
• D. Prussian blue - Thallium

Answer: (C)

Antidote choices must counteract the exact mechanism of a toxin. Leucovorin serves as a rescue after methotrexate by replenishing reduced folates, allowing normal DNA synthesis to continue. Phytomenadione (vitamin K1) reverses warfarin’s effect by restoring vitamin K–dependent clotting factors II, VII, IX, and X. Prussian blue binds thallium in the gut, reducing absorption and speeding elimination. The pairing with benzodiazepines is incorrect because benzodiazepine overdose is treated with flumazenil, a benzodiazepine receptor antagonist, not physostigmine. Physostigmine is used for anticholinergic toxicity, not benzodiazepines.