T1069 Effect of Low-Dose Administration of Lansoprazole On the Gastric Mucosal Lesions Induced By Low-Dose Aspirin in Relation to Intragastric pH in Healthy Volunteers with Different CYP2C19 Genotypes

Abstract

Backgrounds and Aims: Given the major role gastric acid plays in the development of aspirininduced gastric mucosal lesions, proton pump inhibitors (PPIs) are now employed as firstline therapy in treating aspirin-related gastrointestinal disorders. Low-dose PPIs are also expected to have a similar preventive effect on aspirin-induced gastric injury. PPIs are metabolized by CYP2C19 in the liver, and their therapeutic effects are influenced by CYP2C19 genotype status. However, the effect of low-dose PPI on aspirin-induced gastric mucosal injury in relation to gastric acidity in humans has not been examined. Here, we investigated the relationship between intragastric pH and aspirin-induced gastric mucosal lesions with regard to CYP2C19 genotype status in healthy subjects receiving aspirin with and without a low-dose administration of lansoprazole. Methods: Fifteen Helicobacter pylori-negative subjects with different CYP2C19 genotype statuses (5 RMs, 5 intermediate metabolizers [IMs], and 5 poor metabolizers [PMs]) were each administered a series of three 7-day regimens of 15 mg of lansoprazole alone, 100 mg of aspirin alone, and both 15 mg of lansoprazole and 100 mg aspirin, with the order randomized among individuals. A washout period of 2 weeks or more was provided between regimens. Gastric mucosal injury was endoscopically evaluated on day 7 of each dosing period based on the modified Lanza score (MLS). 24-hour intragastric pH monitoring was started after endoscopy. Results: Median values (range) of MLS were 0 (0-1) in controls, 0 (0-1) in subjects receiving 15 mg of lansoprazole alone, 3 (0-5) in subjects receiving aspirin alone, and 0 (0-1) in subjects receiving both aspirin and 15 mg of lansoprazole. Lansoprazole increased the intragastric pH and significantly prevented aspirin-induced gastric mucosal injury (p = 0.0009 for aspirin and lansoprazole 15 mg). MLSs were negatively correlated with 24-hour intragastric pH (r = -0.740, P < 0.0001), whereas aspirin had no effect on intragastric pH. With regard to treatment with aspirin and lansoprazole 15 mg, although median values of MLS did not differ among the three genotype groups, median values of intragastric pH during treatment with this regimen were higher in PMs than in RMs and IMs (P = 0.009 for RMs, P = 0.028 for IMs). Conclusion: We observed a significant relationship between 24-hour intragastric pH and grade of aspirin-induced gastric mucosal lesions. Further, the acid inhibition attained on administration of 15 mg of lansoprazole appeared sufficient to prevent aspirin-induced gastric mucosal damage, irrespective of CYP2C19 genotype status.