Obesity surgery may alter drug absorption pattern

NEW YORK (Reuters Health) - Obese individuals who undergo stomach surgery may not properly absorb certain medications and nutrients from vitamins, minerals and dietary supplements afterwards, a review of published studies suggests.

"Patients should always inform all of their healthcare professionals, including pharmacists and other physicians, that they have undergone bariatric (stomach) surgery and ask them if their medications, vitamins, minerals, or dietary supplements will be properly absorbed," advises Dr. Kelly M. Smith of the University of Kentucky College of Pharmacy in Lexington.

"Physicians, pharmacists, and other healthcare professionals should always carefully evaluate the ability of any drug, vitamin, mineral or dietary supplement (taken by mouth) to be absorbed in bariatric surgery patients," she added.

Smith and a colleague, Dr. April D. Miller, who is also at the University of Kentucky, reviewed the available literature on potential absorption problems that stomach surgery patients may face. They focused their review on the type of stomach surgery performed most often in the U.S. called Roux-en-Y gastric bypass, a combination procedure that restricts the amount of food the stomach can hold by making it smaller. The surgery also includes creating a bypass of a portion of the small intestine that can cause malabsorption of nutrients.

This could cause drug absorption trouble, Smith explained, given that some medications like delayed or timed-release formulations are designed specifically to be absorbed in certain sections of the gastrointestinal (GI) tract. These drugs "may not be properly absorbed if a patient's GI tract has been altered by a surgical procedure," she said.

"If absorption is likely to be a problem, alternative medications or dosage forms, including liquid medications or those made in a patch form, may need to be utilized," Smith told Reuters Health.

Miller added in a statement, "After bariatric surgery, all patients should take a daily multivitamin and calcium supplementation -- preferably in a powder or liquid form to enhance absorption. "Monthly B12 injections and early bone density testing should also be considered."
SOURCE: American Journal Health-System Pharmacy, October 1, 2006.