Gastric juice, gastric tissue and blood antibiotic concentrations following omeprazole, amoxicillin and clarithromycin triple therapy

Background. Amoxicillm and clarithromycin are key antibiotics in proton pump inhibitor-based Helicobacter pylori eradication therapies. Aims. To study gastric mucus and tissue concentrations and collect basic data about optimal antibacterial doses. Methods. Plasma, gastric mucosa and gastric juice anitibiotic concentrations were measured following either low- or high-dose amoxicillin (750 or 1000 mg bid) and clarithromycin (400 or 500 mg bid) given in combination with omeprazole 20 mg bid to 12 male volunteers in an open crossover design. Gastric juice and mucosal biopsy collection was performed either 2 (n = 6) or 6 hours (n = 6) after dosing. Results. Amoxicillin concentrations 2 hours after high dosage were gastric juice > gastric body > antral mucosa > plasma. At 6 hours, plasma and gastric juice concentrations were still above the MIC for amoxicillin-susceptible bacteria but no antibiotic was detectable in mucosa samples. Clarithromycin concentrations after high dosage were gastric juice > mucosa > serum; all above the MIC for clarithromycin-susceptible bacteria at both 2 and 6 hours. Conclusions. Both dosage regimens provided effective antibiotic concentrations in gastric juice at 2 hours. After dosing, both antibiotics demonstrated high gastric tissue concentrations via local diffusion while clarithromycin also provided sustained delivery (6 hours) via gastric mucosa penetration.