CYP2C19 Genotype Predictor of Gastric Acid Suppression

Proton pump inhibitors are metabolized through the CYP2C19 hepatic enzyme system. Several
variant genotypes of this enzyme exist which may lead to decreased, normal or increased
metabolism of the proton pump inhibitor. With alteration of metabolism, the degree of gastric
acid suppression achieved and efficacy in treating reflux could be affected. For example,
Asian populations who have low activity of CYP2C19, commonly need lower doses of proton pump
inhibitors to manage gastroesophageal reflux because of more sustained blood levels and
availability of the drug. Theoretically, those patients who are rapid metabolizers would
receive less effective treatment with proton pump inhibitors

Inclusion criteria:

- Age 18 or older

- Have either mild-to-moderate Los Angeles (LA) Classification System grade B,
moderately severe LA grade C, or severe LA grade D erosive reflux esophagitis

- Or patients having a clinically indicated pH/impedance monitoring on proton pump
inhibitor therapy for indications of gastroesophageal reflux disease.

Exclusion criteria:

- Neoplasm of the esophagus or stomach

- Use of drugs that interfere with CYP2C19 metabolism Diazepam, phenytoin,
amitriptyline, clomipramine, clopidogrel Cyclophosphamide, progesterone, fluoxetine,
fluvoxamine, ketoconazole Lansoprazole, omeprazole, ticlopidine

- Evidence of active H. pylori infection

- Inability to read due to: Blindness, cognitive dysfunction, or English language
illiteracy

- Disorders which predispose to unreliable responses such as Schizophrenia, Alzheimer's
disease or significant memory loss