Rosuvastatin and Losartan Pharmacokinetics After Bariatric Surgery

Inclusion Criteria: * Adults aged 18 to 65 years; * Formal clinical indication for RYGB or sleeve gastrectomy after multidisciplinary assessment; * Bariatric surgery scheduled and no previous bariatric procedure; * Able to understand the study and provide written informed consent. Exclusion Criteria: * Moderate or severe hepatic impairment, liver enzymes greater than 3 times the upper limit of normal, or Child-Pugh class B or C. * Estimated glomerular filtration rate below 30 mL/min/1.73 m². * Concomitant use of drugs that substantially affect rosuvastatin pharmacokinetics and cannot be temporarily discontinued, including cyclosporine, gemfibrozil, or potent OATP1B1/BCRP or CYP2C9 inhibitors. * Systemic antibiotic use within 3 months or probiotic, prebiotic, or synbiotic use within 4 weeks before sampling. * Continuous current rosuvastatin or other statin therapy unless medically discontinued with an adequate washout period under physician supervision. * Clinically relevant baseline hypotension, significant hyperkalemia, renal impairment, or another condition that makes a losartan test dose unsafe. * Severe postoperative complication preventing oral dosing, including active gastrointestinal leak, intractable vomiting, or severe anastomotic stenosis. * Pregnancy. Participants of childbearing potential undergo routine preoperative beta-hCG testing.