Drugs that interfere with folic acid increase birth defects

December 5, 2000 in Pregnancy and Breastfeeding, Vitamins, Minerals, Supplements

Drugs that interfere with folic acid increase birth defects

A new study finds that drugs that interfere with the body's use of the B vitamin folic acid (folate) can increase the risk of birth defects if taken during pregnancy. Researchers agree that lack of folic acid during pregnancy raises the risk of spina bifida and other neural tube defects. However, the suspected link with some other birth defects is less clear.

Researchers from Boston University reviewed 6,932 infants born with oral clefts or defects of the heart or urinary tract. They were compared with 8,387 babies with other defects not thought to be caused by lack of folic acid.

Most drugs that can disrupt folic acid are known as dihydrofolate reductase inhibitors. They include the cancer drugs aminopterin and methotrexate; sulfasalazine, an anti-inflammatory drug; pyrimethamine, used to treat protozoal infections; triamterene, a diuretic; and trimethoprim, an ingredient of the antibiotic Bactrim. Some drugs used to treat epilepsy, including phenytoin, phenobarbital, primidone and carbamazepine, can also can affect folic acid.

The researchers found that the risk of heart defects and oral clefts roughly tripled if mothers used dihydrofolate reductase inhibitors during the first three months of pregnancy. It doubled if they used the epilepsy medicines.

Women of childbearing age are urged to take multivitamins to make sure they get enough folic acid. The study found that the vitamins reduced much of the extra risk of birth defects among women using the dihydrofolate reductase inhibitors but not among those taking the epilepsy medicines.

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