ABSENCE OF AN INHIBITORY EFFECT OF OMEPRAZOLE AND NIZATIDINE ON PHENYTOIN DISPOSITION, A MARKER OF CYP2C ACTIVITY

The effects of omeprazole (40 mg orally per day) and nizatidine (300 m g orally per day) on the disposition of phenytoin (4.5 mg kg-1 p.o. si ngle dose) were studied in 18 healthy, young adult males. Total and un bound plasma concentrations of phenytoin were measured for 48 h after each dose of phenytoin. Neither treatment altered the disposition kine tics of phenytoin, the hydroxylation of which is mediated specifically by cytochromes P450 of the 2C subfamily.