This study looks at the effect on basal and pentagastrin-stimulated acid output of 40 mg Esomeprazole (Nexium) administered orally and intravenously as a 15-minute infusion to people with symptoms of Gastroesophageal Reflux Disease (GERD)

Inclusion Criteria:

1. Heartburn on at least 2 days of the past 7 days prior to screening, with or without a history of EE or a documented diagnosis of GERD within 6 months prior to screening, with or without a history of EE.
2. Body mass index (BMI) of ≥18.5 and ≤35 kg/m2. [BMI will be calculated using the following formula: weight (kg)/height (m)2.]
3. Able to communicate with the investigator and to understand and comply with the requirements of the study.

Exclusion Criteria:

1. History of esophageal, gastric, or duodenal surgery, except for simple closure of an ulcer.
2. History of severe liver disease, including (but not limited to) cirrhosis and acute or chronic hepatitis.
3. Any significant "alarm symptoms", within the past 6 months, such as, unintentional weight loss, gastrointestinal bleeding, jaundice or any other sign indicating serious or malignant disease.
4. Abnormal lab test results, as indicated in the protocol.
5. Other diseases, as indicated in the protocol.