19/12/08 Up to one in five people on antibiotics stop taking their full course of antibiotic therapy due to diarrhea. Physicians could help patients avoid this problem by prescribing probiotics, according to a study by researchers at Albert Einstein College of Medicine of Yeshiva University published in American Family Physician.

Antibiotics target "bad" bacteria but may also kill the "good" bacteria in the large intestine, leading to diarrhea. Diarrhea can also result from bacterial and viral infections. Probiotics -- cultures of "good" microorganisms similar to those normally found in the gut have been promoted as restoring the microbial balance disrupted by antibiotics and infections. Probiotic bacterial strains are added to certain yogurts and brands of miso and other fermented foods, and are also available as powders and pills sold in health food stores.

The Einstein scientists reviewed the medical literature and found seven, high-quality studies in which probiotics were administered to people. The researchers concluded that the studies support the use of probiotics for avoiding diarrhea resulting from antibiotic use or from gastrointestinal viral or bacterial infections. In addition, the probiotics used in these studies were found to rarely cause adverse effects, even in children.

"With the level of evidence that probiotics work and the large safety margins for them, we see no good reason not to prescribe probiotics when prescribing antibiotics," says Dr. Benjamin Kligler, a co-author of the study and associate professor of clinical family and social medicine at Einstein. "The only drawback is that probiotics are not covered by health insurance." On average, a one-month supply of probiotics costs between $8 and $22.

Dr. Kligler notes that the effects of probiotics doses are short-lived, so they should be taken throughout a course of antibiotic therapy. Probiotics will not diminish the effectiveness of antibiotics, he adds.

Because probiotics are considered dietary supplements, they are not regulated as stringently as conventional foods and drugs. Products vary widely in bacterial dose and in quality. The Einstein paper specifies several commercial probiotic preparations of sufficient strength to offer health benefits. In general, probiotic doses of more than 5 billion colony-forming units per day for children and more than 10 billion colony-forming units per day for adults were associated with the best outcomes.