INTRODUCTION:In the treatment of upper GI endoscopy-negative patients with heartburn and epigastric pain or burning, antacids, antireflux agents, and mucosal protective agents are widely used, alone or as add-on treatment, to increase response to proton-pump inhibitors, which are not indicated in infancy and pregnancy and account for significant cost expenditure.METHODS:In this randomized, controlled, double-blind, double-dummy, multicenter trial assessing the efficacy and safety of mucosal protective agent Poliprotect (neoBianacid, Sansepolcro, Italy) vs omeprazole in the relief of heartburn and epigastric pain/burning, 275 endoscopy-negative outpatients were given a 4-week treatment with omeprazole (20 mg q.d.) or Poliprotect (5 times a day for the initial 2 weeks and on demand thereafter), followed by an open-label 4-week treatment period with Poliprotect on-demand. Gut microbiota change was assessed.RESULTS:A 2-week treatment with Poliprotect proved noninferior to omeprazole for symptom relief (between-group difference in the change in visual analog scale symptom score: [mean, 95% confidence interval] −5.4, −9.9 to −0.1; −6.2, −10.8 to −1.6; intention-to-treat and per-protocol populations, respectively). Poliprotect's benefit remained unaltered after shifting to on-demand intake, with no gut microbiota variation. The initial benefit of omeprazole was maintained against significantly higher use of rescue medicine sachets (mean, 95% confidence interval: Poliprotect 3.9, 2.8–5.0; omeprazole 8.2, 4.8–11.6) and associated with an increased abundance of oral cavity genera in the intestinal microbiota. No relevant adverse events were reported in either treatment arm.DISCUSSION:Poliprotect proved noninferior to standard-dose omeprazole in symptomatic patients with heartburn/epigastric burning without erosive esophagitis and gastroduodenal lesions. Gut microbiota was not affected by Poliprotect treatment. The study is registered in Clinicaltrial.gov (NCT03238534) and the EudraCT database (2015-005216-15).