Phase 1 (day 1 to day 4): baseline (control) activities of CYP2B6, CYP2C8 and OATP1B1 will be measured using selective probe substrates. Eligible subjects will receive simultaneously a single 100 mg dose of bupropion (CYP2B6), a single 10 mg dose montelukast (CYP2C8) and a single 5 mg dose of rosuvastatin (OATP1B1) by mouth on empty stomach together at least 10 days before phase 2. Frequent plasma samples will be collected for 72 hours and urine for 48 hours after dosing. Safety assessment will be made for the first 24 hours. Phase 1 is completed after the last blood draw on day 4 (72 hours).