Pharmacokinetic/Pharmacodynamic Study of Metformin with Gastric Bypass Surgery



Bariatric surgery has been the only durable option for weight loss in the extremely obese individuals. The number of bariatric surgery performed has increased 10-fold from 1998-2008. Roux-en-Y gastric bypass surgery (GBS) is the most frequently performed bariatric surgery procedure in the US. It involves restrictive and malabsorptive mechanisms. Theoretically, GBS will significantly alter the absorption/disposition of orally administered medications. Currently, littel information is available about the effect of GBS the absorption/disposition of metformin. The lack of this knowledge may result in inappropriate dosing and compromized clinical outcomes. Thus, the goal of this study is to compare the pharmacokinetic/pharmacodynamic (PK/PD) properties of metformin before and after GBS. To accomplish this goal, the hypothesis that PK/PD profiles of metformin are decreased after GBS will be tested. Adults who undergo GBS and take scheduled metformin prior to GBS will be included in the study. Blood samples will be drawn immediately prior to surgery and at each follow-up visit at 1,3,6,12 months after the surgery. Serum drug concentrations will be determined using LC-MS/MS and pharmacokinetic parameters will be calculated. The pharmacodynamic profiles, i.e. glucose concentrations and HGA1c levels will also be determined.