Changes to gastric pH, gastric emptying time, gastrointestinal transit-time or the pre-systemic metabolizing effect of enzymes secreted in the mucosa may all alter the pharmacokinetics of medicines. These factors are potentially influenced by bariatric surgery. Little is so far known about how gastric bypass and sleeve gastrectomy impacts the biological availability of medication. In this study the pharmacokinetic effects of bariatric surgery on enalapril are investigated.