folinic acid (foh-lin-ik) n. a derivative of folic acid involved in purine synthesis. Administered by mouth or by injection (in the form of its calcium or disodium salts), it is used to reverse the biological effects of methotrexate, and so prevent excessive toxicity (f. a. rescue), and to potentiate the action of fluorouracil. Trade names: Isovorin, Lederfolin, Refolinon, Sodiofolin.

folinic acid The 5‐formyl derivative of the vitamin folic acid; more stable to oxidation than folic acid itself, and commonly used in pharmaceutical preparations. The synthetic (racemic) compound is known as leucovorin.