NEW YORK, Aug 01 (Reuters) -- Some prenatal multivitamins containing folic acid, a dietary supplement that can significantly decrease neural tube birth defects, may not deliver the expected amount because of the tablet's failure to dissolve quickly enough.
The United States Pharmacopoeia Convention's (USP) dissolution standard requires that a tablet release 75% of the labeled folic acid amount within one hour. In a new study from the University of Maryland School of Pharmacy, professors Stephen Hoag, Ralph Shangraw, and graduate student Hanu Ramachandruni examined a variety of prescription multivitamins. Only three out of the nine multivitamin products they tested met the USP standards. Most of the products missed this minimum standard by a wide margin, two releasing less than 25% of the labeled amount.
"Typically vitamins, including folic acid, are more readily absorbed in the upper gastrointestinal tract, just beyond the stomach," says Hoag. "Not meeting the standard of dissolving within an hour highlights a potential problem with these products. The amount of folic acid available for optimal absorption in the body could be inadequate."
Folic acid is most efficiently absorbed at a particular part of the intestine called the jejunum. If a drug is not dissolved quickly during digestion, it may pass the jejunum and not be sufficiently absorbed by the body.
Previous research has shown that folic acid supplementation can decrease the incidence of neural tube (spinal cord birth) defects such as spina bifida and anencephaly by 50% to 72%. In addition, folic acid seems to reduce homocysteine levels in the body, lowering the risk for arteriosclerotic disease. This has led the U.S. Public Health Service to recommend that everyone, especially women of child-bearing age, increase folic acid supplementation by 0.4 milligrams per day.
The researchers are not willing to name the products studied because "these (USP) standards were not official when some of the products were manufactured" and have since been improved by some companies. This also does not mean that people should stop taking their vitamins, warns Shangraw. "Vitamins should preferably be taken with food and plenty of fluids. Any amount absorbed is beneficial, and no one is sure what amount of folic acid is needed to reduce neural tube defects."
SOURCE: Journal of the American Pharmaceutical Association (1997;4:397-400)
