OBJECTIVE: Proton pump inhibitors and antimicrobial agents are widely used to eradicate Helicobacter pylori (H. pylori) infection. In the general population the prevalence of infection and of polypharmacy increases the possibility of drug-drug interactions during H. pylori eradication therapy. The purpose of the present study was to assess the prevalence, degree, and clinical relevance of metabolic interference with the cytochrome P450 enzymatic system occurring during 1 wk of administration of omeprazole, lansoprazole, or pantoprazole followed by the association of clarithromycin and metronidazole for another week. The 13C aminopyrine breath test (ABT) was chosen to screen for possible interactions. METHODS: We studied 30 patients referred to our Unit for H. pylori eradication therapy. They were randomized to receive either omeprazole (20 mg b.i.d.), lansoprazole (30 mg b.i.d.), or pantoprazole (40 mg b.i.d.) for 2 wk. During the second week clarithromycin (250 mg b.i.d.) and metronidazole (500 mg b.i.d.) were added. ABT was performed before, and at the end of the first and second week of therapy. Percentage of the administered dose of 13C recovered per hour at the peak (percent 13C dose/h at the peak) and cumulative percentage of administered dose of 13C recovered over time at 120 min (percent 13C dose cum120) were the ABT evaluated parameters. RESULTS: At baseline all patients showed a normal liver function. In individual patients during treatment we observed various liver metabolic interactions both as inhibition and induction, as well as after the first and the second week of therapy. However, mean modifications of the ABT parameters during the 2 weeks of therapy were not statistically significant compared to baseline values. None of the patients who had ABT variations complained of side effects. CONCLUSIONS: H. pylori eradication therapy interferes with cytochrome P450-dependent liver metabolic activity. However, the clinical relevance of these metabolic interactions is not yet apparent, and further investigation is needed. H. pylori eradication therapy appears safe, but these interactions should be considered in the choice of proton pump inhibitor and antimicrobial agents. (C) 2000 by Am. Coll. of Gastroenterology.
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