Gastroesophageal reflux disease and reflux-esophagitis are a major chronic problem in most children with cerebral palsy and mental retardation. Oral administration of enteric-coated formulations of the acid-labile proton pump inhibitor omeprazole is often problematic in these patients who may be suffering from swallowing disorders. A suspension of omeprazole in a sodium bicarbonate solution is often used for administration via the gastrostomy tube. This trial aims to compare the pharmacokinetics of omeprazole administered through the gastrostomy tube as a suspension in pediatric patients with cerebral palsy and mental retardation versus the pharmacokinetics of omeprazole administered as a multi-unit-pellet system (MUPS®). The crossover study will consist of 2 consecutive treatment periods of 14 days.

Inclusion Criteria:

• Children > 15 kg
• Cerebral palsy and mental retardation with swallowing disorders
• Presence of gastrostomy tube
• GERD and/or reflux-esophagitis treated with omeprazole at the same dose since at least 2 weeks
• Informed consent

Exclusion Criteria:

• Treatment with ciclosporine, tacrolimus, mycofenolate
• Treatment with anticoagulants
• Infection
• Recent start of treatment with known inhibitors of the omeprazole-metabolism
• Moderate to severe hepatic impairment (SGPT and/or AST > 3 times upper limit)