Effect of Gastric Bypass on the Absorption of Metformin

Study Overview
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Brief Summary
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Background: Gastric bypass is the most commonly performed type of bariatric (obesity) surgery, has dramatically increased in popularity and is now considered to be preferred treatments in severely obese patients that fail non-surgical therapy - particularly in patients with type 2 diabetes. Drug malabsorption is a potential concern post-gastric bypass because intestinal length is reduced. Purpose: The purpose of this controlled, pharmacokinetic study is to determine whether the absorption of a single dose of metformin, the first line drug treatment in patients with type 2 diabetes, is significantly reduced after gastric bypass. Methods: A single dose of standard release metformin 1000 mg will be administered to patients who have undergone gastric bypass and to patients who have not received surgery but are on the wait list (wait-listed controls). Blood sampling and urine sampling will occur in standardized fashion over the ensuing 24 hours to measure and compare the absorption of metformin between study arms. 34 patients total will be recruited. Significance: Following completion of this study, we will better understand how gastric bypass affects metformin absorption. Ultimately, this information will help to ensure that this patient population is receiving optimal doses of this important drug treatment.

Official Title
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Effect of Gastric Bypass on the Absorption of Metformin

Conditions
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Obesity, Gastric Bypass

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients living within and around Edmonton that have been referred to the Alberta Health Services Weight Wise Program Exclusion Criteria: Undergone or undergoing revision of a previous bariatric procedure Any major post-operative gastrointestinal complications, such as an anastomotic leak, outlet obstruction or persistent vomiting Currently on metformin therapy Any contraindications to metformin therapy such as: allergy to the drug chronic metabolic acidosis history of lactic acidosis liver failure or baseline liver enzymes higher than 3-fold above the upper limit of normal congestive heart failure renal failure (glomerular filtration rate < 60 ml/min) alcoholism acute illness fatty liver disease Pregnant or nursing Not taking furosemide or nifedipine (both drugs may increase metformin absorption by 15-20%)the day of visit 2. Any other medical, social or geographic condition, which, in the opinion of the investigator would not allow safe completion of the study protocol

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Post Gastric Bypass<br> | |
| Obese Controls<br>age, BMI, gender matched | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Area-under-the-curve of metformin absorption (0-infinity) |  | cross-sectional | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| AUC (0-24h) |  | cross-sectional | 
| tmax |  | cross-sectional | 
| cmax |  | cross-sectional | 
| AUC glucose (0-8h) |  | cross-sectional | 
| bioavailability of metformin (urine metformin concentration from 0-infinity) |  | cross-sectional | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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obesity, gastric bypass, metformin, pharmacokinetics, absorption