Effect of aceclofenac on pharmacokinetic of phenytoin

Aceclofenac is presently most commonly prescribed analgesic for chronic pain and inflammatory conditions. In clinical practice, phenytoin and aceclofenac are used in a chronic condition of generalized seizure with concomitant chronic pain. Hence there are chances of drug-drug interaction because modulations of isoenzymes involved in metabolism of phenytoin and aceclofenac are CYP2C9/10 and CYP2C19. It is important to maintain the therapeutic level of phenytoin in plasma for effective control of seizure. So, the aim of the study was to determine the effect of aceclofenac on the pharmacokinetics of phenytoin in rabbits. In a parallel design study, phenytoin 30 mg/kg/day per oral was given daily for seven days. On day 7, blood samples were taken at various time intervals between 0-24 hours. In aceclofenac group, phenytoin was administered for seven days as above. On day 8, aceclofenac 14 mg/kg along with phenytoin 30 mg/kg/day was administered and blood samples drawn as above. Plasma phenytoin levels were assayed by HPLC and pharmacokinetic parameters were calculated. In aceclofenac group, there was decrease in t½el than phenytoin group significant changes were observed in the pharmacokinetic parameters in aceclofenac treated group. These results suggest that aceclofenac alter the pharmacokinetics of phenytoin. Confirmation of these results in human studies will warrant changes in phenytoin dose or frequency when aceclofenac is co-administered with it.