Gastric acidity and acid breakthrough with twice-daily omeprazole or lansoprazole

Background: In patients with severe gastro-oesophageal reflux disease (GERD ), proton pump inhibitors are being used increasingly in twice-daily regime ns to improve control of gastric acidity. Few data exist to compare the abi lity of the most-often used proton pump inhibitors, omeprazole and lansopra zole, to control gastric acid at twice-daily dosage regimens. Nocturnal aci d breakthrough, defined as gastric pH < 4.0 continuously for > 60 min, may compromise treatment goals in patients with GERD. Aim: To compare the effects of omeprazole 20 mg b.d. or lansoprazole 30 mg b.d. on gastric acidity and the relative ability of each dosage regimen to prevent acid breakthrough. Methods: In a crossover pharmacodynamic study, 20 healthy volunteers (10 ma le, 10 female, mean age 38 years) were given omeprazole 20 mg b.d. or lanso prazole 30 mg b.d. for 7 days each, in a randomized manner. Each dosage reg imen was separated by a minimum 7-day period where no medication was admini stered. On day 7 of each regimen, 24-h intragastric pH-metry was performed. The percentage of time for which gastric pH was below 4.0 and 3.0, the occ urrence of daytime and nocturnal acid breakthrough, and the duration of act ion of each regimen were compared. Non-parametric statistics for paired dat a were used. Results: The percentage time for which gastric pH was below 4.0 was signifi cantly lower with omeprazole 20 mg b.d. (median 14.8%) than with lansoprazo le 30 mg b.d. (median 24.2; P=0.0372). Fourteen subjects showed more effect ive acid control when taking omeprazole; these were significantly more ofte n H. pylori-negative patients compared with those for whom acid control was better on lansoprazole (P < 0.001). Nocturnal acid breakthrough occurred i n seven patients (35%) on omeprazole and in 10 (50%) on lansoprazole (N.S.) . Conclusion: In healthy volunteers, twice-daily dosing of omeprazole 20 mg b .d. appears to be significantly more effective than lansoprazole 30 mg b.d. in controlling gastric acidity. The clinical importance of such a differen ce remains to be defined in GERD patients.