Hypothesis: Immediate-release omeprazole suspension may have a more rapid pharmacokinetic profile and greater overall drug absorption in gastroparesis. This will result in shorter time to maximal drug concentration, greater maximal concentration, and greater total area under the curve of the concentration vs. time plot.

Primary Objective: To compare the pharmacokinetics of omeprazole between immediate-release suspension and delayed-release capsules in patients with heartburn associated with gastroparesis.

Study design: randomized, open-labeled, crossover treatment for 7 days with 10-14 days washout. Pharmacokinetic studies will be performed after 7 days on study drug.

Inclusion Criteria:

• Symptoms of heartburn >2 days per week off antireflux therapy, defined by “a burning feeling rising from the stomach or lower chest up towards the neck”

• Symptoms of gastroparesis >1 month in duration, defined by nausea, vomiting, bloating, dyspepsia, early satiety, or effortless regurgitation.

• Prior abnormal 4-hour gastric emptying scan within the past 3 years

Exclusion Criteria:

• History of esophageal or gastric surgery

• Severe gastroparesis with any of the following: vomiting with dehydration requiring IV hydration, hospitalization, weight loss >10 % pre-illness weight, requiring feeding jejunostomy tubes

• Presence of gastric electrical stimulator

• Symptoms of retching with vomiting more than 2 days per week

• Diagnosis of diabetes

• Disorders of small bowel motility (such as pseudo-obstruction or dumping syndrome)

• Disorders of small bowel absorption

• Diagnosis of gastric outlet, small bowel or colon mechanical obstruction

• Diagnosis of acid hypersecretory syndrome

• Disorders affecting proton pump inhibitor metabolism (such as liver failure)

• Known allergy or side effects to proton pump inhibitor

• Non-ambulatory patients: bed-ridden, nursing home resident, etc.

• Pregnancy