Abstract

Megaesophagus is a condition characterized by generalized dilation and reduced or absent motility of the esophagus, leading to ineffective transport of food and liquids from the mouth to the stomach. A dog diagnosed with megaesophagus and concurrent gastroesophageal reflux disease showed inadequate response to conventional proton pump inhibitor therapy. An off-label treatment regimen combining vonoprazan, a potassium-competitive acid blocker, and mosapride, a prokinetic agent, was initiated to achieve enhanced acid suppression and improve esophageal motility. Vonoprazan was administered orally at 1 mg/kg once daily, and mosapride at 1 mg/kg every 12 h. The combination therapy was well tolerated, with no adverse effects observed. Notably, the dog demonstrated a marked reduction in regurgitation frequency and improvement in clinical condition. This case suggests that vonoprazan, with its potent and sustained acid suppression, when paired with a prokinetic like mosapride, may offer a promising alternative for managing megaesophagus-associated gastroesophageal reflux disease in dogs unresponsive to standard therapy. Further studies are warranted to evaluate the safety, efficacy, and long-term benefits of this approach in veterinary patients.