Folate, absorption anticonvulsants

Folic acid deficiency can be caused by drugs that interfere with folate absorption or metabolism. Phenytoin, some other anticonvulsants, oral contraceptives, and isoniazid can cause folic acid deficiency by interfering with folic acid absorption. Other drugs such as methotrexate and, to a lesser extent, trimethoprim and pyrimethamine, inhibit dihydrofolate reductase and may result in a deficiency of folate cofactors and ultimately in megaloblastic anemia. 

R2. Reizenstein, P., and Lund, L., Effect of anticonvulsant drugs on folate absorption and the cerebro spinal folate pump. Scand. J. Haematol. 11, 158-165 (1973). 

Shafer, R. B., and Nuttall, F. Q., Calcium and folate absorption in patients taking anticonvulsant drugs. J. Clin. Endocrinol. Metab. 41, 1125-1129 (1975). 

DiphenyUiydantoin and other anticonvulsants impair the intestinal absorption of folates. This may be by inhibition of intestinal conjugase however, the evidence from various studies is conflicting. 

Certain drugs such as anticonvulsants and oral contraceptives can impair the absorption of folate. Anticonvulsants also increase the rate of folate metabolism. 

It has been suggested that anticonvulsants inhibit the absorption of folate by the inhibition of intestinal conjugases (S5) but results from various studies have been conflicting. Some workers have reported impaired absorption of folate when given with diphenylhydantoin (B2, El) while others have failed to demonstrate this effect (R2, S6). There is some evidence that anticonvul-... 

FOLATE DEFICIENCY Folate deficiency is a common complication of diseases of the small intestine, which interfere with the absorption of dietary folate and the recirculation of folate through the enterohepatic cycle. In acute or chronic alcohohsm, daily intake of dietary folate may be severely restricted, and the enterohepatic cycle of the vitamin may be impaired by toxic effects of alcohol on hepatic parenchymal cells this is the most common cause of folate-deficient megaloblastic erythropoiesis. However, it also is the most amenable to therapy, inasmuch as the reinstitution of a normal diet is sufficient to overcome the effect of alcohol. Disease states characterized by a high rate of cell turnover, such as hemolytic anemias, also may be complicated by folate deficiency. Additionally, drugs that inhibit dihydrofolate reductase (e.g., methotrexate and trimethoprim) or that interfere with the absorption and storage of folate in tissues (e.g., certain anticonvulsants and oral contraceptives) can lower the concentration of folate in plasma and may cause a megaloblastic anemia. 

An anticonvulsant drug. Among its undesirable side-effects h that of osteomalacia. This is thought to be due to the stimulatior by the drug of hepatic enzymes which inactivate vitamin D resulting in decreased calcium absorption. Phenytoin also in terferes with folate metabolism and this may result in i megaloblastic anaemia. 

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