Proton pump inhibitors (PPI) are used to decrease stomach acid secretion. A generic form of omeprazole, one of the PPIs, is on the market. With cheaper than brand name PPIs, it is unclear whether generic omeprazole is as effective clinically. This study compares generic omeprazole with half-dose esomeprazole, the strongest brand name PPI. The half-dose esomeprazole is in fact cheaper than generic omeprazole. Healthy volunteers will take each medication in turn for 7 days and their stomach acid will be measured while taking each medication. We hypothesize that half-dose esomeprazole is better at suppressing stomach acid than generic omeprazole.