The purpose of this study is

1. To describe patient characteristics and drug usage among children that are prescribed esomeprazole for the first time and to compare them with patients who are prescribed other proton pump inhibitors (PPIs) or H2-receptor antagonists for the first time.
2. To ascertain all incident hospitalized cases of angioneurotic oedema, pneumonia, gastroenteritis, failure to thrive, convulsions/seizures, acute interstitial nephritis and thrombocytopenia among new users in the three cohorts of esomeprazole, other PPIs and H2-receptor antagonists.

Time Perspective: Other = Retrospective analysis of prospectively collected data Number of Anticipated Subjects: All subjects dispensed esomeprazole, other PPIs or H2-receptor antagonists for the first time during the study period

Inclusion Criteria:

• Age 0-18 years
• Newly dispensed esomeprazole, other proton pump inhibitors or H2-receptor antagonists

Exclusion Criteria:

• Children with less than one year of history in PHARMO RLS before study cohort entry (if a child is <1 year at cohort entry, history from birth is required)
• Children using more than 1 acid suppressing drug concomitantly at cohort entry

The study population will include all children aged 0 to 18 years receiving a first dispension of acid suppressing drugs recorded in the PHARMO RLS database between September 2008 and October 2011. Subjects will be followed-up for at least 18 month. First review of study outcomes including chart reviews is estimated to start in August 2011.