Pharmacokinetic considerations in Roux-en-Y gastric bypass patients

Abstract

Purpose: Pharmacokinetic considerations in patients who have undergone Roux-en-Y gastric bypass (RYGB) are explored.

Summary: The prevalence of obesity, especially morbid obesity, has dramatically increased in recent years. In response, the number of bariatric surgeries performed has risen sharply, as this surgery is the technique demonstrated as being the most effective for sustained treatment of morbid obesity. RYGB, the most popular technique in the United States, combines the principle of restriction (dramatically decreasing stomach size) with malabsorption (bypassing the entire duodenum). It stands to reason that a decrease in gastric and intestinal absorptive surface area may considerably affect oral bioavailability of some drugs. Drugs that require a more acidic environment for absorption, uncoating, or activation and drugs that rely on intestinal transporters located in the duodenum for proper absorption would be most affected. Practitioners looking for guidance in tailoring pharmacotherapy to the RYGB patient will find little help in the primary literature at this time. Until more pharmacokinetic studies are available, practitioners may apply and log P of individual the principles of pK(a) drugs in the attempt to predict the potential impact of the RYGB on a drug's absorption. Likewise, if a drug relies on certain transporters located with highest frequency in the duodenum, alternative therapies can be selected that do not rely on such transport mechanisms for absorption.

Conclusion: The pK(a), log P, and intestinal transport mechanisms should be considered when determining which drugs may have altered pharmacokinetics in patients who have undergone RYGB.