Adding Once-Daily Omeprazole 20 mg to Metronidazole/Amoxicillin Treatment for Helicobacter pylori Gastritis: A Randomized, Double-Blind Trial Showing the Importance of Metronidazole Resistance

OBJECTIVE: We compared the Helicobacter pylori eradication rate after a 14-day treatment with amoxicillin 500 mg t.i.d. and metronidazole 500 mg t.i.d. with or without omeprazole 20 mg once daily. METHODS: This was a randomized, controlled trial in which omeprazole was given in double-blind fashion. Patients with H. pylori-associated gastritis were enrolled in four centers in Canada from July 1991 to January 1994. Eradication of H. pylori was assessed by histological evaluation and culture of endoscopic biopsies obtained from the antrum and corpus of the stomach. RESULTS: The H. pylori eradication rate was 73% (33 of 45) in the omeprazole-amoxicillin-metronidazole group, compared with 66% (31 of 47) in the amoxicillin-metronidazole group. This 7% difference was not statistically significant (p = 0.43, 95% confidence interval for difference -11% to 26%). Metronidazole primary resistance in the prestudy cultures was found more frequently in the omeprazole-amoxicillin-metronidazole group than in the amoxicillin-metronidazole group. Resistance to metronidazole was an important predictor of treatment failure. The H. pylori eradication rate was 61% (19 of 31) for patients infected with metronidazole-resistant H. pylori strains, compared with 91% (30 of 33) eradication for those infected with metronidazole-sensitive strains (p < 0.01). Vaginal candidiasis was reported in four patients. CONCLUSIONS: The H. pylori eradication rate was higher (73%) for omeprazole-amoxicillin-metronidazole than for the dual antibiotic therapy given without omeprazole (66%); however, this difference was not statistically significant. Metronidazole resistance significantly reduces H. pylori eradication rates.