Omeprazole is a highly effective drug for the treatment of gastroesophageal reflux disease (GERD) in infants. Infants, aged 0-12 months, require a non-standard dose of omeprazole. Due to this fact extemporaeus formulations of omeprazole are administered to these infants. The oral bioavailability of omeprazole in nonproprietary formulations may be unpredictable and produce variable degrees of drug exposure. The dose range for GERD management in pediatric studies using omeprazole is 0.3 - 3.5 mg/kg/day.

Dosing information, aged-specific pharmacodymanic and pharmacokinetic data are not avaible in infants, aged 0-12 months. Two adult studies at healthy volunteers suggest that a omeprazole suppository is an effective dosage form.This study is designed to evaluate and to compare the efficacy, the pharmacodynamics and the pharmacokinetics of oral and rectal omperazole treatment of omeprazole in infants with gastroesophageal reflux disease.

Inclusion Criteria:

• age 3-6 months
• weight: 3 kg or > 3 kg
• gastroesophageal reflux as a result of esophageal atresia or congenital diaphragmatic hernia.
• Informed consent of both parents

Exclusion Criteria:

• Allergy to omeprazole
• Infants with gastroesophageal reflux as a result of congenital errors of CNS
• Changes in the co-medication during the study
• Participation in a study that is interfering with this study.
• The use of the following co-medication: alprazolam, midazolam, triazolam, carbamazepine, clorazepate, ciclosporin, disulfiram, phenytoin, iron, itraconazole, ketoconazole, voriconazole, methotrexate, ticlopidine, warfarin.
• Infants of the non-Caucasian race