Analysis of the Influence of Gastric By-Pass on the Pharmacokinetics of Common Drugs

The aim of this study is to investigate the pharmacokinetics of some of the most frequently prescribed oral drugs in hospital and outpatient medicine, in patients undergoing GBP surgery for obesity associated with metabolic syndrome. Paradoxically, despite their frequency of use, very few data, contradictory data or no data at all characterize the molecules we wish to study.

The number of patients undergoing GBP surgery is growing rapidly, as their life expectancy reaches that of the general population once their weight has normalized. However, while weight loss induced by surgery can improve, and more rarely cure, the comorbidities associated with metabolic syndrome, the majority of patients will need to continue or modify their treatments.

It is therefore essential to know the pharmacokinetics of the antihypertensive, lipid-lowering and hypoglycemic drugs they will be taking throughout their lives, in order to adapt their dosage if necessary, or even to change therapeutic class if their absorption is insufficient after GBP.

Moreover, as some studies have shown, the pharmacokinetics of many molecules are likely to vary over time in these patients (19), probably as a result of weight loss itself, but also possibly due to adaptive phenomena in the digestive tract. Studying the pharmacokinetics of the molecules used in the usual treatment of metabolic syndrome in most obese patients should make it possible to: target the preferred sites of absorption in the digestive tract of the molecules studied, study the variations in absorption linked to GBP but also the pharmacokinetic changes linked to weight loss as a function of time. In fact, metabolic capacity may be both decreased and increased in obese patients compared to healthy subjects (20,21), so that drug clearance may both increase and decrease after weight normalization. It is therefore difficult to predict the pharmacokinetics of drugs immediately or long after GYP. The results obtained should make it possible to adapt treatment in these patients, both in terms of changing the dosage administered and in the choice of molecules.

Inclusion criteria

• Age ≥ 18 years
• Patients having undergone a complete bariatric course, eligible for bariatric surgery after validation of the operative indication by a multidisciplinary RCP dedicated to obesity, in accordance with HAS criteria: morbid obesity with BMI > 40 kg/m2 or severe obesity with BMI >35Kg/m2
• Patients with a comorbidity linked to one of the elements of metabolic syndrome that can be improved by surgery: type 2 diabetes, hypertension, dyslipidemia.
• Patients treated pre-operatively for at least 2 weeks with one or more of the molecules designed to control metabolic syndrome and selected for our study:

• Antihypertensive: amlodipine; candesartan,
• Hypolipidemic: rosuvastatin
• Hypoglycemic agent: metformin
• Patients scheduled for Y-shaped gastric bypass surgery
• Membership of a social security scheme

Exclusion criteria

• History of restrictive bariatric surgery (sleeve)
• History of renal or hepatocellular insufficiency
• Patient undergoing treatment or having stopped treatment within the last month with a drug that may alter the clearance of the molecules studied: enzyme inducer or inhibitor (boosted antiproteases, macrolides, azole antifungals, grapefruit juice, rifampicin, rifabutin, phenobarbital, phenytoin, St John's wort), probenecid, non-steroidal anti-inflammatory drugs, etc.
• Patients treated with a drug that may alter the bioavailability of associated drugs: antacids containing aluminium or magnesium hydroxide, gastric dressings, etc.
• Patients for whom it is impossible to give informed consent (language barrier)
• Patients taking part in another interventional clinical study
• Patients under legal protection (guardianship, curatorship)
• Pregnant or breast-feeding women