Effect of gastric acid suppression on 13C‐urea breath test: comparison of ranitidine with omeprazole

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Abstract
The assessment of the effect of H2 antagonists on the results of the urea breath test has produced controversial results. To assess whether standard doses of both omeprazole and H2 blockers can adversely influence the accuracy of the urea breath test. Sixty dyspeptic patients with ascertained Helicobacter pylori infection were recruited for this prospective, open study. They were randomized to receive either omeprazole 20 mg at 08:00 hours (n = 30) or ranitidine 300 mg at 22:00 hours (n = 30) for 14 days. The urea breath test was performed at baseline, on day 14, while patients were still taking the antisecretory drugs, and on day 21, 1 week after their cessation. Duplicate breath samples were collected after ingestion of 75 mg 13C-urea + citric acid. A δ value > 5‰ was considered positive. On day 14 the median δ values had declined, but not significantly (P = 0.07) compared to baseline (13.79 vs. 22.39) with omeprazole, while they had increased (P = 0.27) with ranitidine (27.21 vs. 19.46). On the same day there were five out of 30 (17%) and five out of 28 (18%) false-negative results in the omeprazole and ranitidine groups, respectively. All these cases became positive again on day 21. However, in eight cases treated with omeprazole and 13 treated with ranitidine, there was an increase of 14-day δ values compared to baseline. Our study shows that both omeprazole and ranitidine at standard doses are able to negatively affect the results of the urea breath test. Their adverse effect resolves within 7 days of drug cessation and therefore the withdrawal of these drugs 7 days before testing seems to be sufficient to avoid false-negative results. The surprising finding that both antisecretory drugs reduce δ values in one group and increase them in another group of patients deserves further study.