The effect of multiple anticonvulsant therapy on the expression of phenytoin-induced gingival overgrowth

The potential effect of co-medication with phenobarbitone, primidone and carbamazepine on plasma and saliva concentrations of 5-(4-hydroxyphenyl)-5-phenylhydantoin (4-HPPH), the major metabolite of phenytoin in man and on the incidence of phenytoin-induced gingival overgrowth was investigated in a group of 36 adult epileptic patients. There were no significant differences in plasma or saliva concentrations of 4-HPPH or phenytoin in patients prescribed phenytoin alone, compared to those who received phenytoin with either phenobarbitone, primidone, or carbamazepine. In addition, the extent and the incidence of gingival overgrowth were similar in the 2 groups. The results suggest that chronic co-medication with other anti-convulsant drugs which induce phenytoin metabolism, does not affect the plasma or saliva 4-HPPB steady-state levels, nor the degree of gingival overgrowth in adult epileptic patients on therapy with phenytoin.