Acid-suppressive effects of generic omeprazole: Comparison of three brands of generic omeprazole with original omeprazole

Generic omeprazole contains the same active ingredient as original omeprazole and require verification of the bioequivalence with original omeprazole. However, very few clinical studies have been reported. A prospective, randomised, open-label, crossover study to compare acid-suppressive effect of generic omeprazole with that of original omeprazole. Seven healthy Helicobacter pylori-negative subjects of CYP2C19 extensive metaboliser. Intragastric pH was measured for 24 h without medications (placebo) and on day 7 of repeated administration of 10 mg once daily after breakfast of original omeprazole, Omeprazon, or three brands of generic omeprazole, Omeprazole-Towa, Ovulanze or Omerap. Median values of intragastric pH and percentages of time with pH > 4 for 24 h were significantly higher with administration of any omeprazole formulation compared with placebo ( P < 0.05, Wilcoxon signed-rank test). Whereas, during the night-time period (20:00–08:00 h), percentages of time with pH > 4 with Omeprazole-Towa and Omerap were not significantly higher than placebo. Compared with Omeprazon, these two parameters for 24 h showed significantly greater inter-subject variations with Omeprazole-Towa ( P < 0.05 and P < 0.01, F-test) and Ovulanze ( P < 0.05). Acid-suppressive effects of some brands of generic omeprazole are not the same as original omeprazole. These differences might be reflected in clinical outcomes.