Megaloblastic anemia w/ MXT or antiepileptics. Decreased serum conc of phenytoin & barbiturates. May lower blood conc of vit B
12.
May be inhibited by gastric acidity & presence of ascorbate in GI
tract. Reduced intestinal absorption w/ metformin. Folate depletion w/
phenytoin. Dihydrofolate reductase inhibitors. May produce deficiency states w/ antiepileptics, OCs, anti-TB drugs, alcohol & folic acid antagonists (eg, MXT, pyrimethamine, triamterene, trimethoprim & sulfonamides).