Is eradication of Helicobacter pylori with colloidal bismuth subcitrate quadruple therapy safe?

Background. When standard triple therapy fails to eradicate Helicobacter pylori, quadruple 'rescue' therapy is often used which, in Europe, generally comprises colloidal bismuth subcitrate (CBS) based triple therapy and a proton pump inhibitor Since hypochlorhydria could greatly increase absorption of the toxic bismuth ion from CBS, we investigated the bismuth status of patients receiving anti-H, pylori quadruple therapy. Materials and Methods. In a prospective open label study 34 patients with nonulcer dyspepsia or peptic ulcer disease, who had failed to eradicate H. pylori with standard triple therapy, were subsequently treated with CBS, omeprazole, amoxycillin and metronidazole (BOAM). A further 35 patients received triple therapy for the eradication of H. pylori: CBS, amoxycillin and metronidazole (BAM) (n = 18); placebo bismuth, amoxycillin and metronidazole (AM) (n = 9); or omeprazole, amoxycillin and metronidazole (OAM) (n = 8). Whole blood bismuth levels were determined before and within 24 hours of completing treatment. Analysis of bismuth was by inductively coupled plasma mass spectrometry, and concentrations were compared between groups and with the Hillemand 'alarm level' for blood bismuth (50-100 mug/l). Results. BOAM gave higher blood bismuth levels than BAM (difference in means 13.1, CI 6.0-20.2, p<.001); three (8.8%) patients taking BOAM had concentrations within the Hillemand alarm level at 54.2, 64.7 and 91.8 <mu>g/l. OAM and AM did not alter baseline blood bismuth levels. Conclusions. Caution should be observed in prescribing CBS with gastric acid suppression, and alternative bismuth preparations should be considered.