Effect of Roux-en-Y gastric bypass on the bioavailability of metoprolol from immediate and controlled release tablets: a single oral dose study before and after surgery.

Objective: Roux-en-Y gastric bypass (RYGB) surgery induces major changes in the gastrointestinal tract that may alter the pharmacokinetics of orally administered drugs. Results from pharmacokinetic studies are sparse. This study aimed to investigate the effect of RYGB on the bioavailability of metoprolol from immediate release (IR) and controlled release (CR) tablets in female patient volunteers before and after surgery. Methods: An explorative, two-phase, single oral dose pharmacokinetic study of metoprolol in female patients undergoing RYGB was carried out. The dose was administered twice in each patient, 1 month before and 6 months after surgery. After intake of either 100 mg of metoprolol IR or CR tablet serum concentration-time profiles of metoprolol were determined. The endpoint was the ratio of AUCafter/AUCbefore of metoprolol. Results: Twelve patients were included in the study (metoprolol IR: 7; metoprolol CR: 5). After intake of a metoprolol IR tablet major intraindividual and interindividual differences for area under the serum concentration versus time curve (AUC) of metoprolol before and after surgery were observed (range ratio AUC0-10 hours after/AUC0-10 hours before: 0.74-1.98). For metoprolol CR tablets a significant reduction in bioavailability of metoprolol was observed after surgery (range ratio AUC0-24 hours after/AUC0-24 hours before: 0.43-0.77). Conclusion: RYGB may influence the bioavailability of metoprolol from an IR tablet. The magnitude of changes in bioavailability after RYGB requires close monitoring of patients using metoprolol IR tablets and dose adjustment if deemed necessary. RYGB clearly reduces the bioavailability of metoprolol from a CR tablet. After RYGB clinicians may consider to increase the dose according to clinical response.

Influence of bariatric surgery on the use of medication.

PURPOSE: Bariatric surgery can influence the prevalence and incidence of comorbidities, as well as the pharmacokinetics of drugs. This might lead to changes in the use of drugs. This study aimed to assess the influence of bariatric surgery on the use of medication in patients before and after surgery, focusing on type, number of medications, and daily dosage. METHODS: In a retrospective and prospective observational study, drug dispensing data from pharmacies of patients undergoing their first bariatric surgery between January 2008 and September 2011 was collected. Dispensing data from 1 month before until 12 months after surgery was analyzed. Drugs were classified according to the WHO-ATC classification system. Dosages of drugs were compared using defined daily dose (DDD). RESULTS: Among 450 patients, 12 months after surgery, the mean number of drugs per patient for antidiabetics, drugs acting on the cardiovascular system, anti-inflammatory and antirheumatic drugs, and drugs for obstructed airway diseases decreased by, respectively, 71.3 % (95 % CI 57.2 to 85.4), 34.5 % (95 % CI 28.2 to 43.0), 45.5 % (95 % CI 13.3 to 72.6), and 33.1 % (95 % CI 15.3 to 53.2). Patients used lower median DDD of oral antidiabetics, beta-blocking agents, and lipid-modifying drugs. CONCLUSIONS: For some major drug classes 12 months after bariatric surgery, the use of drugs decreases in terms of mean number per patient. A reduction in dose intensity was observed for oral antidiabetics, beta-blocking agents, and lipid-modifying drugs. Dispensing data from pharmacies may provide detailed information on the use of medications by patients after bariatric surgery.