The purpose of this study is to determine if magnesium pantoprazole 20 mg twice a day (b.i.d.), maintains gastric pH above 4 during a longer percentage of time than magnesium pantoprazole 40 mg once a day (qd). This is a comparison between split dose concept and standard dose of proton pump inhibitors.

Eligible healthy volunteers will be randomly assigned for 2 different treatment sequences: A) magnesium pantoprazole 20 mg b.i.d. followed by magnesium pantoprazole 40 mg q.d. or B) magnesium pantoprazole 40 mg q.d. followed by magnesium pantoprazole 20 mg b.i.d.

Treatment sequences will be administrated as follows: 6 days with the first medication, followed by a washout period of 8 days (no medication) and a further period of 6 days with the second medication.

Treatment efficacy will be established by the percentage of time with intragastric pH >4, measured by 24-hour pH-Metry on day 6 of each medication (on-treatment measurement). Basal pH will be measured as reference.

The blinding distribution of treatments will be maintained for the patients, the doctor and the statistician who will analyze the data.

Main inclusion criteria:

• Carlsson-Dent Questionnaire with score ≤ 4 (negative for GERD).
• Endoscopy: negative for GERD
• BMI between 18.5 and 30

Main exclusion criteria:

• Volunteers with any the following symptoms: dysphagia, digestive track bleeding, anorexia, anemia, involuntary weight loss.
• Women under breastfeeding period, pregnant or under pregnancy suspicion.
• Subjects with abnormal manometry (any motor esophageal disorder).
• Peptic ulcer history and/or ulcer complication.
• Volunteers under PPI treatment, H. pylori eradication treatment, H2 receptor antagonists, prokinetics or similar medication (current, during the last 30 days or during the trial).
• History of systemic glucocorticoids or non-steroidal anti-inflammatory drugs (NSAID) use, during the last 30 days.
• Abnormal laboratory parameters or vital signs, considered clinically relevant by the researcher.