The long-term objective of this research is to implement pharmacogenomic (PGX) testing of approved gene-drug pairs to maximize the efficacy and minimize adverse events for drugs that are used to treat childhood disease. Personalized medicine, that is, the use of the patient's own genetic information to predict the right dose of the right drug, has been a goal of medicine's since the publication of the human genome and HAPMAP projects. However, the adoption of PGX testing has been slow owing to several barriers and challenges. Recently President Obama announced the precision medicine initiative, which includes PGX testing, and has earmarked $ 1 b to implement it. The precision medicine initiative is expected to move personalized medicine forward so that most patients including pediatric patients will benefit. The Nemours Children's Health System is uniquely positioned to lead the effort to personalize medicine among pediatric patients. The goal of the proposed 1-year pilot project is to implement PGX testing in the Nemours children's health system. The experience, knowledge and skills gained in this pilot project will position Nemours to help lead precision medicine initiatives including PGX testing among pediatric populations. To implement PGX testing in Nemours we propose to begin testing the cyp2c19 - proton pump inhibitor gene-drug pair in the division of gastroenterology, Nemours children's hospital. A total of 120 children 2-17 yo who have been diagnosed with gastroesophageal reflux disease (GERD) or other stomach acid mediated conditions for which a PPI is prescribed will be recruited into the study by pediatric gastroenterologists (aim 1a). Drs. Franciosi and Lima will educate staff in the division of PGX testing and of the study. GI pediatricians are not required to participate in PGX testing. After obtaining consent, the study coordinator will obtain and bar code samples of saliva from the patient. Samples will be genotyped by Spartan Rx, a point-of-care genotyping platform, which are housed (2 of them) in the division of pathology. Loss-of-function alleles (\*2, \*3) and the gain-of-function allele (\*17) are identified in \< 60 minutes. The result of genotyping will be checked by dr. Badizadegan and entered into the patient's EMR. Clinical Decision Support (CDS) tools will advise Drs. Badizadegan and Franciosi of the patient's metabolic phenotype based on cyp2c19 genotype. Dr. Franciosi (or other GI pediatricians) will decide the dose of PPI to use based CDS tools carrying algorithms for conventional dosing and for genotype-guided dosing of PPIs. The electronic prescription for the PPI with genotype-guided dosing will be called in. PPI efficacy and safety for each study participant will be monitored weekly (aim 1B) by collecting and recording scores on validated GERD and adverse reaction questionnaires. Efficacy and safety scores will be communicated by each participant (or caregiver) using mobile devices (iPhone; computer) and recorded using redcap. Dr. Blake will supervise this phase of the study. Outcome metrics for aim 1A include: % of patients agreeing to volunteer for the study; % of patients reporting efficacy and toxicity data; % of providers agreeing to participate in study; and % of participants agreeing to future use of DNA. Outcome metrics for aim B will be judgments by Dr. Franciosi and his staff regarding success based on scores from GERD and adverse event questionnaires.