Asymptomatic chronic gastritis decreases metformin tolerance in patients with type 2 diabetes

Digestive disorders represent the most common metformin side effects for type 2 diabetes. The mechanism of these metformin side effects is unclear. The aim of this study was to assess whether asymptomatic chronic gastritis could influence metformin tolerance in patients with type 2 diabetes.Demographic, anthropometric, ultrasound and laboratory data were obtained from 144 metformin naïve patients with diabetes. The diagnosis of chronic gastritis was based on endoscopic and histopathological examination, and H. pylori infection was assessed based on (13) C urea breath test (UBT). All subjects started metformin at 500 mg/day and increasing progressively to 1500 mg/day over 4 weeks. A score of gastrointestinal side effects (abdominal pain, diarrhoea, nausea, vomiting, bloating and anorexia) was assessed each week, and metformin dose was adjusted as appropriate.Based on endoscopy, 64 patients were categorized as non-gastritis subjects and 80 as chronic gastritis subjects. At baseline, there is no statistical difference in gastrointestinal symptoms between two groups. With metformin, the mean scores for gastrointestinal symptoms in the non-gastritis and gastritis subjects were 1·02 ± 1·71 vs. 2·18 ± 2·05 (P = 0·001), 0·20 ± 0·65 vs. 0·50 ± 0·89 (P = 0·022), 0 vs. 0·06 ± 0·24 (P = 0·024) and 1·08 ± 1·03 vs. 1·71 ± 1·66 (P = 0·028). The mean final metformin dose used by gastritis subjects was 706·24 ± 568·90 mg, significantly less than the mean dose used by non-gastritis subjects (1101·56 ± 578·58 mg, P = 0·001). After adjustment for age and sex, the odds ratio (OR) for a final metformin dose of less than 1500 mg/day was found to be 2·76 (95% CI 1·38-5·53, P = 0·004) for chronic gastritis subjects. The OR for a final metformin dose of less than 1000 mg/day was found to be 3·98 (95% CI 1·91-8·27, P = 0·001) for chronic gastritis subjects.Our data suggest that pre-existing non-symptomatic gastritis was associated with metformin-related gastrointestinal side effects.