Which antidote is used for methotrexate overdose?

• A. Flumazenil
• B. N-acetylcysteine
• C. Leucovorin
• D. Deferoxamine

Answer: (C)

Leucovorin is the correct antidote used for methotrexate overdose due to its role as a folate antagonist that mitigates the effects of high levels of methotrexate in the body. Methotrexate is an antimetabolite that inhibits folate metabolism, which is crucial for DNA synthesis. In cases of overdose or high doses of methotrexate, leucovorin acts as a rescue agent by providing the necessary folate that can counteract the toxic effects, allowing for the normalization of cellular function and promoting recovery of healthy cells that are affected by methotrexate's antitumor activity.

The use of leucovorin is particularly important because it bypasses the metabolic block caused by methotrexate, thus facilitating the production of nucleic acids essential for cell replication and repair. This is a critical intervention in clinical settings when patients experience toxicity from methotrexate, especially in cases of severe overdose or prolonged exposure due to impaired renal function.

In contrast, flumazenil is an antidote for benzodiazepine overdose, N-acetylcysteine is used primarily for acetaminophen toxicity, and deferoxamine is used for iron overdose. Each of these agents targets specific toxins that