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If you are a woman of childbearing age, you may already be taking that all-important daily dose of folic acid to protect against birth defects if you become pregnant. But if you take birth control pills or certain other medications, they could leave you less protected.
"Folic acid is crucial to the prevention of several serious birth defects, and certain prescription drugs interfere with the body's ability to use folic acid," says Donald R. Mattison, M.D., medical director of the March of Dimes.
The March of Dimes urges women and their health care providers to be alert to interactions between common prescription drugs and the B vitamin folic acid. Mattison says the drug interactions are one reason why a woman is encouraged to have a prepregnancy checkup.
"The physician may want to change the medication she is taking or raise the amount of folic acid, as well as to monitor her blood levels carefully," he says.
The March of Dimes' message came in response to a study of folic acid antagonists during pregnancy and the risk of birth defects published in The New England Journal of Medicine.
The article listed several medications that can lead to folic acid deficiency, including medications used to treat some very common conditions, such as high blood pressure, urinary tract infections, heartburn and reflux. Oral contraceptives and the antibiotic tetracycline also are reported to interfere with folic acid, according to Mattison.
Drugs to watch
The drugs listed in the article as culprits in the interference of folic acid are:
- Phenobarbital, phenytoin (Dilantin®), carbamazapine (Tegretol®) and primidone (Mysoline®) are used primarily to prevent seizures.
- Antibiotic combination of trimethoprim and a sulfonamide (Bactrim®, Septra®) are commonly used for urinary tract infections.
- Triamterene (Dyrenium®) is a diuretic used for high blood pressure.
- Sulfasalazine (Azulfidine®) is used for ulcerative colitis and other inflammatory conditions.
- Anticonvulsant valproic acid (Depakene®).
- Cimetidine (Tagamet®) is used to treat heartburn and reflux.
- Beta-blockers and calcium-channel blockers are used for high blood pressure and certain heart disorders.
- Cholestyramine (Locholest®, Questran®) is used to lower cholesterol levels.
A word of caution: Women taking medications for a chronic medical condition such as high blood pressure or epilepsy should not discontinue these medications on their own either prior to pregnancy or upon learning of being pregnant. Let your doctors (your medical specialist and gynecologist) know your plans and always follow their advice.
The March of Dimes recommends that all women of childbearing age consume 400 micrograms of folic acid daily as part of a healthy diet beginning before pregnancy to prevent birth defects of the brain and spine known as neural tube defects (NTDs). If you have previously had a pregnancy affected by a birth defect of the brain or spinal cord, ask your doctor how much folic acid to take. NTDs, which include spina bifida and anencephaly, are among the most serious and common birth defects in the United States. Each year, an estimated 2,500 babies are born with NTDs and many additional affected pregnancies result in miscarriage or stillbirth.
Folic acid should be taken before a woman gets pregnant, as it only can help prevent birth defects during the first weeks of her pregnancy. By the time a woman knows she's pregnant, her baby's brain and spine are already formed.
Getting the full benefit of folic acid
The surest way to get the required 400 micrograms of folic acid daily is to take a multivitamin. Multivitamins, breakfast cereals and grain products fortified with folic acid are more easily absorbed by the body than the natural form. "The folate in foods is different than what you have in a vitamin pill," Mattison says. "Only about half of that (folate) is absorbed."
As an added assurance, try eating foods that are naturally rich in folates (the natural forms of folic acid found in foods) such as orange juice, other citrus fruits and juices, leafy green vegetables, beans, peanuts, broccoli, asparagus, peas, lentils and whole-grain products.
To get full folic acid protection, Mattison advises taking your multivitamin with water because 100 percent of the folic acid is absorbed as opposed to taking it with food where some absorption is lost. He also has a word about those fortified cereals, which boast of providing the daily recommended dose of folic acid.
"Sometimes cereal manufacturers spray folic acid on the cereal as opposed to mixing it in, so if you don't drink the milk or whatever you put on the cereal, some of the folic acid stays in the liquid," Mattison explains. The reason is simple: Folic acid is water-soluble.
This article was reviewed and updated June 2007.
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