Folinic acid

Folinic acid, also known as leucovorin, is a medication used to decrease the toxic effects of methotrexate and pyrimethamine. It is also used in combination with 5-fluorouracil to treat colorectal cancer and pancreatic cancer, and may be used to treat folate deficiency, anemia, and methanol poisoning. It is taken by mouth, injection into a muscle, or injection into a vein. Better known as 5-formyltetrahydrofolate in biochemistry, it is a natural form of folate, albeit with no clear function. Side effects may include trouble sleeping, allergic reactions, or fever. Use in pregnancy or breastfeeding is generally regarded as safe. When used for anemia it is recommended that pernicious anemia as a cause be ruled out first. Folinic acid is a form of folic acid that does not require activation by dihydrofolate reductase to be useful to the body. Folinic acid was first made in 1945. In 2025, the United States Food and Drug Administration approved leucovorin calcium tablets for cerebral folate deficiency, bypassing standard review and drawing expert criticism. It is on the World Health Organization's List of Essential Medicines.