What is the rescue medication used for pulmonary fibrosis when administering Methotrexate (Rheumatrex)?

Leucovorin is the correct answer because it is used as a rescue medication to help mitigate the side effects of Methotrexate, particularly when Methotrexate is used at higher doses or when there is a concern about toxicity. Methotrexate can interfere with folate metabolism, leading to bone marrow suppression and mucositis. Leucovorin, a form of folate, helps to replenish the folate levels in the body, thereby reducing the risk of these side effects.

This context becomes particularly significant in patients receiving Methotrexate for pulmonary fibrosis, as it is important to monitor and manage potential complications that might arise from the treatment. Leucovorin acts as a safeguard during Methotrexate therapy, allowing patients to continue receiving the medication while minimizing harmful effects.

The other options listed do not serve the same function in this context. Digoxin is used primarily in heart conditions, amiodarone is an antiarrhythmic medication, and non-dihydropyridine calcium channel blockers (CCBs) are generally used for hypertension and certain types of cardiac arrhythmias but are not indicated as rescue medications for Methotrexate toxicity.