S-Tenatoprazole-Na (STU-Na), a new drug currently under clinical development, belongs to a class of drugs, called proton pump inhibitors (PPls). Some PPIs are already commercially available. STU-Na will be used for treatment of acid related diseases (gastroduodenal ulcers, erosive or ulcerative esophagitis due to gastroesophageal reflux disease). This study evaluates the degree of acid suppression by different doses of STU-Na. The degree of acid suppression is considered to be correlated with clinical efficacy.~In this study four dosages of STU-Na (30 mg, 60 mg, 90 mg, and 120 mg) will be tested in each volunteer. First, one of the dosages will be orally administered for five days. Then, a nine to sixteen day period without study drug administration will follow prior to the administration of the next dosage, for again five days. Each volunteer will have a total of four study drug administration periods.~After the last study drug intake in period 1, 2 and 3 pharmacokinetic blood sampling will be done for four days. After the last study drug intake in period 4 pharmacokinetic blood sampling will be done for five days. Pharmacokinetic blood sampling consists of several blood draws over a pre-determined time period. The pharmacokinetic blood sampling measures the medication concentration in the blood at pre-defined time points.~After the last study drug intake in period 1, 2, 3, and 4, gastric acidity will be measured for 24 hours by means of a thin tube that will be inserted into the stomach through the nostril to evaluate the efficacy of the different dosages of STU-Na.
S-Tenatoprazole-Na (STU-Na), a new drug currently under clinical development, belongs to a class of drugs, called proton pump inhibitors (PPls). Some PPIs are already commercially available. STU-Na will be used for treatment of acid related diseases (gastroduodenal ulcers, erosive or ulcerative esophagitis due to gastroesophageal reflux disease). This study evaluates the degree of acid suppression by different doses of STU-Na. The degree of acid suppression is considered to be correlated with clinical efficacy.~In this study four dosages of STU-Na (30 mg, 60 mg, 90 mg, and 120 mg) will be tested in each volunteer. First, one of the dosages will be orally administered for five days. Then, a nine to sixteen day period without study drug administration will follow prior to the administration of the next dosage, for again five days. Each volunteer will have a total of four study drug administration periods.~After the last study drug intake in period 1, 2 and 3 pharmacokinetic blood sampling will be done for four days. After the last study drug intake in period 4 pharmacokinetic blood sampling will be done for five days. Pharmacokinetic blood sampling consists of several blood draws over a pre-determined time period. The pharmacokinetic blood sampling measures the medication concentration in the blood at pre-defined time points.~After the last study drug intake in period 1, 2, 3, and 4, gastric acidity will be measured for 24 hours by means of a thin tube that will be inserted into the stomach through the nostril to evaluate the efficacy of the different dosages of STU-Na.