Folic acid is given to treat megaloblastic anemia due to folic aciddeficiency. This type of anemia usually occurs in patients who have tropical or nontropical sprue, although it can also result from poor nutritional intake during pregnancy, infancy, or childhood.
Folic acid is absorbed rapidly in the first third of the small intes-tine, distributed into all body tissues, and metabolized in the liver. Excess folate is excreted unchanged in urine, and small amounts of folic acid are excreted in stool. Folic acid also appears in breast milk. Synthetic folic acid is readily absorbed, even in malabsorp-tion syndromes
Folic acid is an essential component for normal RBC production and growth. A deficiency in folic acid results in megaloblastic ane-mia and low serum and RBC folate levels.
Folic acid is used to treat folic acid deficiency. Patients who are pregnant or undergoing treatment for liver disease, hemolytic ane-mia, alcohol abuse, or skin or renal disorders typically need folic acid supplementation. Serum folic acid levels below 5 ng/ml indi-cate folic acid deficiency.
Leucovorin is a folic acid derivative used to treat folic acid de-ficiencies resulting from administration of methotrexate.
§ Methotrexate, sulfasalazine, hormonal contraceptives, aspirin, triamterene, pentamidine, and trimethoprim reduce the effective-ness of folic acid.
§ In large doses, folic acid may counteract the effects of anticon-vulsants, such as phenytoin, potentially leading toseizures. (See Adverse reactions to folic acid.)