Lack of pharmacokinetic interaction between mexiletine and omeprazole.

Objective: To investigate the effect of omeprazole on the pharmacokinetics of mexiletine.

Methods: Nine healthy male Japanese volunteers participated in a crossover study. On day 1, the subjects received mexiletine 200 mg. On days 2-7, they received omeprazole 40 mg, and on day 8 they received mexiletine 200 mg and omeprazole 40 mg concomitantly. Serum concentrations of mexiletine were determined just before drug administration and at 1, 2, 3, 4, 6, 8, 12, and 24 hours on day 1 and day 8.

Results: No differences in mexiletine concentrations were observed between the two phases of the study. The mean AUCs after administration of mexiletine alone and in combination with omeprazole 40 mg/d were 6.26 and 6.20 ng.h/L, respectively.

Conclusions: These findings suggest that omeprazole does not affect mexiletine metabolism.