A GASTROINTESTINAL SIMULATION SYSTEM (GISS) FOR DISSOLUTION OF DRUGS BEFORE AND AFTER ROUX-EN-Y GASTRIC BYPASS:FIRST RESULTS

Introduction Roux-en-Y gastric bypass (RYGB) surgery is the most commonly performed procedure in bariatric surgery, greatly reducing stomach size and bypassing much of the small intestine. Hence it may reduce the absorption and bioavai-lability of oral medications, especially modified release products. However, the pharmacokinetics of drugs after RYGB are poorly studied. An in vitro dissolution method simulating the conditions before and after RYGB might be a valuable tool to predict the behaviour of drugs with possible bioavailability problems in vivo. The objective of this study was to develop a gastrointestinal simulation system (GISS) mimicking conditions before and after RYGB for investigating dissolution characteristics of oral medications. Methods The GISS is a dissolution method which is based on a design by Schellekens et al. [1]. The GISS enables variation in parameters which are relevant to drug release in vivo: pH, volume, transit time, osmolality and agitation. During the test an oral drug formulation is exposed to solutions simulating stomach, (duodenum) jejunum, ileum and colon in fasting and non-fasting conditions before and after RYGB. Metoprolol immediate (IR) and controlled release (CR) tablets were tested in triplo. Release profiles were determined by measuring the concentrations of metoprolol spectrophotometrically. Results The GISS is able to expose an oral dosage form to subsequent environments simulating fasting and non-fasting conditions before and after RYGB. So far, release profiles of the tested products have been studied in conditions before RYGB. In non-fasting conditions after 30 min the release of metoprolol from the IR tablet is complete. From the CR tablet after 300 min almost 30 % of metoprolol is released. Conclusion A GISS has been developed to study release behaviour of medication during its passage through the gastrointestinal tract in fasting and non-fasting conditions before and after RYGB. Studies in which the situation after RYGB is simulated are in progress