Transfer of clarithromycin to gastric juice is enhanced by omeprazole in Helicobacter pylori-infected individuals

Background: The effects of proton-pump inhibitors and Helicobacter pylori i nfection on the distribution of drugs employed for the eradication of H. py lori are poorly understood. The aim of this study was to investigate the ef fects of a 7-day oral administration of 20 mg omeprazole on the distributio n of clarithromycin in the gastric juice of individuals with H. pylori infe ction. Methods: Eighteen H. pylori-infected dyspeptic male volunteers witho ut endoscopic lesions were enrolled in a study with an open, randomized, tw o-period crossover design and a 21-day washout period between phases. Plasm a and gastric juice concentrations of clarithromycin in subjects with and w ithout omeprazole pretreatment were measured by means of liquid chromatogra phy coupled to tandem mass spectrometry. Results: The maximum concentration of clarithromycin (C-max) and the area under the time-concentration curve from 0 to 2 h (AUC(0-2h)) were significantly higher in gastric juice than i n plasma. Omeprazole treatment further augmented clarithromycin C-max and A UC(0-2h) in gastric juice approximately 2-fold (P < 0.05). Conclusions: Sho rt-term treatment with omeprazole in H. pylori-positive volunteers increase s the amount of clarithromycin transferred to the gastric juice, confirming a synergism between these drugs. Our results suggest the presence of an ac tive transport mechanism for clarithromycin from plasma to the gastric lume n, which is influenced by omeprazole.