A STUDY OF THE INTERACTION BETWEEN OMEPRAZOLE AND PHENYTOIN IN EPILEPTIC PATIENTS

This study was performed to determine the effect of omeprazole, given in therapeutically recommended doses, on the steady-state plasma levels of phenytoin in epileptic patients. Five menand three women of median age 34 years participated in the study.Steady-state plasma levels of phenytoin were measured once a weekfor 2 weeks before and after, respectively, and during 3 weeks ofconcomitant omeprazole treatment with 20 mg daily. Urinary excretion of phenytoin and its metabolite [5-(p-hydroxyphenyl)-5-phenyl-hydantoin were determined before and at the end of the omeprazole treatment period. The steady-state plasma phenytoin levels as well as urinary excretion of phenytoin and its main metabolite were unchanged during omeprazole treatment. The resultsfrom this study suggest that concomitant omeprazole treatment in therapeutically recommended doses (20 mg daily) will not significantly affect the steady-state plasma levels of phenytoin in epileptic patients. © 1990 Raven Press, Ltd., New York.