Comparing the acid-suppressive effects of three brands of generic lansoprazole with the original: pharmacokinetic bioequivalence tests do not necessarily guarantee pharmacodynamic equivalence.

Generic drugs contain the same active ingredient as an original drug and have their bioequivalence proved by pharmacokinetic tests. However, few studies have been reported on whether these bioequivalence studies infer pharmacodynamic equivalence. In this study, in eight healthy Helicobacter pylori-negative CYP2C19 extensive metabolizers, we compared the acid-suppressive effects of repeated administration of 15 mg of three brands of generic lansoprazole, Taiproton, Tapizol, and Lansoral, with those of the original lansoprazole, Takepron. Median intragastric pH value for 24-h and % pH > 4 for daytime (08:00-20:00 h) and night-time were significantly higher with any lansoprazole formulation, compared with the control (P < 0.05, Wilcoxon signed-rank test). However, during the daytime, % pH > 4 with Tapizol was significantly lower than the original (P < 0.05). Compared with the original, no significantly larger, but no small range of inter-subject variations were observed in these two parameters for each of the three brands of generic lansoprazole (Bartlett test). Pharmacokinetic bioequivalence tests do not necessarily guarantee pharmacodynamic equivalence.