Pantoprazole, a proton-pump inhibitor widely used for stress ulcer prophylaxis and gastroesophageal reflux disease,12 is metabolized mainly by CYP2C19 and to a lesser extent by CYP3A4. Genetic variants in the CYP2C19 enzymes substantially influence the PK of pantoprazole.13 Here, CYP2C19 is linked to gastroesophageal reflux disease.