It is planned to compare the efficacy and safety of rabeprazole 50 mg DDR (dual delayed release) capsules versus rabeprazole 20 mg enteric coated tablets administered once daily in patients with Gastroesophageal Reflux Disease (GERD).

Inclusion Criteria:

• Diagnosis of GERD with symptoms (i.e. regurgitation, pyrosis) at least 1 or more episodes a week.
• Age ≥ 18 years and <65 years
• Helicobacter pylori (an infection) negative
• Have a body mass index (BMI) between 18 and 33 kg/m²
• pH>4 gastric exposure <25% on a 24-hour dual pH channel monitoring study performed prior to screening (normal intragastric pH +2SD)
• Pathologic intraesophageal acidity exposure (DeMeester score >14.75 and/or >4% of pH<4 (at least 21 hours measured)

Exclusion Criteria:

• Patiets with Barrett's stricture, gastric outlet obstruction, malignancy, gastrointestinal system bleeding or any other upper gastrointestinal system pathology.
• Patients whose Hiatus hernia is > 3 cm.
• Patients with uncontrolled or insulin dependent diabetes mellitus, symptomatic gallbladder stone, active or unhealed stomach or duodenum ulcer, Zollinger-Ellison syndrome, primary esophagus motility disorder, pancreatitis, inflammatory bowel disease, severe lung disease, chronic liver disease, uncontrolled kidney impairment, cancer (except skin cancer except melanoma), cerebrovascular disease, epilepsy.
• Patients with history of heart failure, ventricular tachycardia, ventricular fibrillation, cardiac arrest, Torsades de pointes, bradycardia, sinus node dysfunction, heart attack, long QTc (>450 ms for male, >470 ms for female patients).
• Patients taken PPIs or H2-blockers within 7 days and prokinetic drugs within 3 days before entering the study.
• Patients with major psychiatric disease.
• Alcoholism and drug use.
• Patients with pathologic laboratory tests; hemogram, sedimentation, CRP, thyroid functions tests, liver enzymes.
• Malabsorbtion.
• Immunosuppressive patients.
• Patients taken cortisone.
• Patients taken other drugs that prolong QT interval.
• Patients taken drugs that need gastric acid for optimal absorption; ketoconazole, iron salts, digoxin, ampicillin esters, anticoagulants, antineoplastic agents, prostaglandin analogues, sukralfat.
• Pregnancy or breast-feeding.
• Patients taken drugs that may affect gastrointestinal system motility or acid release.
• History of abdominal surgery (hysterectomy, abdominal hernia repair, caesarean cases may be included; cholecystectomy have to be excluded).
• Patients taken NSAII drugs (paracetemol may be used up to 2 gr/day).
• Patients taken antidepressants.
• Hypersensitivty to study drugs.
• Known allergy to peanut and soy.