RA06.06: PATHOGENESIS OF POTASSIUM-COMPETITIVE ACID BLOCKER (P-CAB)-RESISTANT NON-EROSIVE REFLUX DISEASE, AND GASTRIC ACID SECRETION-INHIBITORY EFFECTS OF P-CAB

Abstract

Abstract Background In PPI-resistant NERD patients with symptoms related to acid reflux due to insufficient acid suppression, the symptoms may be improved by the administration of potassium-competitive acid blocker (P-CAB), which is a potent acid inhibitor. However, there are patients with P-CAB-resistant NERD, in whom symptoms persist despite the administration of P-CAB. The objective of this study was to clarify the pathogenesis of P-CAB-resistant NERD. Methods Forty-three patients with NERD (20 males, mean age 57.7 ± 2.5 years old), who had persistent reflux symptoms despite the administration of P-CAB (vonoprazan, 20 mg/day for 2 to 4 weeks), were included in this study. After excluding eosinophilic esophagitis (EoE) and primary esophageal motility disorders, esophageal impedance-pH monitoring was performed on P-CAB therapy. The relationship between reflux and symptoms was evaluated according to the symptoms index (SI). Reflux episodes were characterized by pH measurement as acid, weakly acidic or weakly alkaline according to a published consensus report. In symptom index (SI)-positive patients, the mechanism of SI positivity and percent time with intragastric pH > 4 and with esophageal pH < 4 were investigated according to the presence or absence of Helicobacter pylori infection. Results One (2.3%) of 43 patients had a primary esophageal motility disorder (Jackhammer esophagus). Eighteen (41.9%) and 3 (7%) patients were SI-positive for liquid- and gas-only reflux, respectively, and the remaining 21 patients who were SI-negative (48.8%) had functional heartburn. All patients SI-positive for liquid reflux were SI-positive for weakly acidic reflux. The percent time with intragastric pH > 4 and esophageal pH < 4 were 98.1 ± 0.8% and 0.18 ± 0.1% (mean ± SE), respectively, in H. pylori-positive patients and 79.9 ± 4.3% and 0.28 ± 0.1%, respectively, in H. pylori-negative patients, demonstrating that gastric acid was sufficiently suppressed by P-CAB regardless of the presence or absence of H. pylori infection. Conclusion The pathogenesis of P-CAB-resistant NERD was elucidated in 51% of patients. Symptoms in all patients SI-positive for liquid reflux were related to weakly acidic reflux, and symptoms related to acid reflux may be ruled out by the administration of P-CAB. Disclosure All authors have declared no conflicts of interest.