Folate deficiency states may be produced by drugs such as antiepileptics, oral contraceptives, anti-tuberculosis drugs, alcohol, and folic acid antagonists such as methotrexate, pyrimethamine, triamterene, trimethoprim and sulfonamides. In some instances, such as during methotrexate or antiepileptics therapy, replacement therapy with folic acid may become necessary in order to prevent megaloblastic anemia developing; folate supplementation has reportedly decreased serum-phenytoin concentrations in few cases and there is a possibility that such an effect could also occur with barbiturate-antiepileptics. Cholestyramine and folic acid when administered together, there may be reduction or delay in folic acid absorption. If concomitant therapy is required, folic acid should be administered at least 1 hour before or 4 hours after cholestyramine.