The Effects of Switching to Vonoprazan, a Novel Potassium-Competitive Acid Blocker, on Gastric Acidity and Reflux Patterns in Patients with Erosive Esophagitis Refractory to Proton Pump Inhibitors

<b><i>Background/Aim:</i></b> The effects of vonoprazan and proton pump inhibitors (PPIs) in patients with reflux esophagitis (RE) have not yet been compared using multichannel intraluminal impedance-pH (MII-pH). <b><i>Methods:</i></b> A total of 8 patients with persistent gastric mucosal injury, despite completing an 8-week standard PPI therapy, were enrolled in the study. While they were on standard PPI therapy, the baseline values of reflux parameters, holding time ratio (HTR) of gastric pH >4, and esophageal pH <4 were obtained by using 24 h MII-pH monitoring. They were re-evaluated after discontinuation of the therapy and 4 weeks of subsequent treatment with vonoprazan 20 mg/day. <b><i>Results:</i></b> The patients were found to be CYP2C19 extensive metabolizers and negative for <i>Helicobacter pylori</i> infection. In 7 patients (87.5%), the mucosal lesions had healed completely after vonoprazan therapy. A significant increase in gastric pH >4 HTR was observed, from 26.5 to 78.0% (<i>p</i> = 0.029). A reduction in esophageal pH <4 HTR was also observed but it was not statistically significant. Furthermore, acid clearance time and the total number of reflux events, including acid and proximal reflux events, were significantly reduced. <b><i>Conclusion:</i></b> Vonoprazan may be a better therapy for the treatment of patients with PPI-refractory RE.