Bismuth + metronidazole + tetracycline. Why risk adding bismuth?

The standard treatment for peptic ulcer associated with Helicobacter pylori is a combination of omeprazole, amoxicillin and clarithromycin, which renders the bacterium undetectable in about 70% of cases. A fixed-dose combination of bismuth subcitrate potassium + metronidazole + tetracycline has been authorised in some European countries for use in this setting, combined with high-dose omeprazole. In a European trial with 440 patients, the 4-drug combination of omeprazole + bismuth subcitrate + metronidazole + tetracycline was significantly more active than the standard 3-drug regimen in terms of H. pylori eradication, as measured with the urea breath test (79.8% with bismuth, 55.4% without bismuth). In a North American trial with 275 patients the success rate was similar with the two treatments, again based on the urea breath test. There are no comparative trials of the 4-drug regimen in patients in whom standard treatment has failed. The main adverse effects of the 4-drug regimen observed in clinical trials were black stools, nausea, headache and dizziness. However, the trials were too small to detect infrequent but serious adverse effects such as bismuth encephalopathy. Safety during pregnancy is not known. Some patients included in clinical trials had detectable plasma bismuth concentrations. Omeprazole increases the absorption of bismuth subcitrate potassium. In practice, the 4-drug regimen combining omeprazole + bismuth subcitrate potassium + metronidazole + tetracycline is probably more effective than standard 3-drug therapy against H. pylori, at least in Europe, but this combination should be avoided due to uncertainties on the possible neurotoxicity of bismuth. Other antibiotic combinations are preferable, and there are too many questions surrounding the adverse effects of this combination for it to replace the standard 3-drug regimen in France.