The purpose of this study is to understand how quickly lansoprazole, once daily (QD), improves feeding in premature babies or babies less than 28 days of age.

A Phase 1, multicenter, pharmacokinetic/Pharmacodynamic and safety study in which infants will be randomized in an open-label fashion to receive 5 days of open-label treatment with lansoprazole pediatric suspension 1 mg/kg/day oral, or lansoprazole pediatric suspension 2 mg/kg/day oral. On Dosing Days 1 and 5, blood samples will be obtained for drug assay. All subjects will be evaluated for inclusion in the pH monitoring portion of the study and will undergo pH monitoring, provided it is clinically indicated, at the discretion of the investigator. Intragastric pH monitoring (up to 24 hours) will be performed at Baseline, on Dosing Day 1 (or Day 2) and on Dosing Day 5 (or Day 6). Intraesophageal pH may be done in addition to intragastric pH at the discretion of the investigator. Subjects will be evaluated for safety, including a follow-up visit on Post-Dosing Day 14.

Inclusion Criteria:

• Hospitalized or outpatient male or female, term or post-term infants beyond the neonatal period (>28 days) but less than 12 months of age, OR a preterm infant with a corrected age of at least 44 weeks but less than 12 months on Dosing Day 1.
• Clinically-evident Gastroesophageal Reflux Disease (feeding intolerance, regurgitation, wheezing or stridor with feedings)
• At least 7 days post-surgery without anticipated need for surgery during study
• No significant laboratory abnormalities

Exclusion Criteria:

• Unstable, clinically significant disease or abnormality
• Congenital anomaly of the upper gastrointestinal tract
• Clinical evidence of acute sepsis
• Cystic fibrosis
• Medical condition requiring subject to not be fed by mouth/gastric tube