BACKGROUND: Vonoprazan is a new acid-suppressing drug that received FDA approval in 2022. It reversibly inhibits gastric acid secretion by competing with the potassium ions on the luminal surface of the parietal cells (potassium-competitive acid blockers or P-CABs). Vonoprazan has been on the market for a short time and there are many clinical trials to support its clinical application. However, medical experience and comprehensive clinical data is still limited, especially on how and if, gastric histology is altered due to therapy.

METHODS: A 12-week experiment trial with 30 Wistar rats was to assess the presence of gastrointestinal morphologic abnormalities upon administration of omeprazole and vonoprazan. At six weeks of age, rats were randomly assigned to one of 5 groups: (1) saline as negative control group, (2) oral omeprazole (40 mg/kg), as positive control group, (3) oral omeprazole (40 mg/kg) for 4 weeks, proceeded by 8 weeks off omeprazole, (4) oral vonoprazan (4 mg/kg), as positive control group, and (5) oral vonoprazan (4 mg/kg) for 4 weeks, proceeded by 8 weeks off vonoprazan.

RESULTS: We identified non-inflammatory alterations characterized by parietal (oxyntic) cell loss and chief (zymogen) cell hyperplasia and replacement by pancreatic acinar cell metaplasia (PACM). No significant abnormalities were identified in any other tissues in the hepatobiliary and gastrointestinal tracts.

CONCLUSION: PACM has been reported in gastric mucosa, at the esophagogastric junction, at the distal esophagus, and in Barrett esophagus. However, the pathogenesis of this entity is still unclear. Whereas some authors have suggested that PACM is an acquired process others have raised the possibility of PACM being congenital in nature. Our results suggest that the duration of vonoprazan administration at a dose of 4 mg/kg plays an important role in the development of PACM.