RESUMO
PURPOSE: Oxcarbazepine (OXC) is chemically related to carbamazepine (CBZ). OZC exerts less liver enzyme induction than CBZ and is completely metabolized by reduction to the active metabolite, 10, 11-dihydro-10-hydroxy-5H-dibenzo (b,f) azepine-5-carboxamide (MHD). It was known that OXC had no significant pharmacokinetic interactions with other antiepileptic drugs. But it is not thoroughly studied yet because of short duration of clinical application. We investigated whether the plasma concentration of OXC metabolite (MHD) is changed by valproic acid compared with OXC monotherapy and studied the correlation of the dose of OXC with the plasma concentration of its active metabolite (MHD). METHODS: The patient with OXC monotherapy (19 cases) and patients with OXC and valproic acid(16 cases) were incluses. We analyzed the level of its metabolites MHD by HPLC RESULTS: The plasma concerntration of MHD in OXC monotherapy is 15.5+/-3.2 microgram/ml and that of the MHD in polytherapy with valproic acid is 16.4+/-3.4 microgram/ml at the same dose of OXC. The plasma concentration of MHD is ranged from 7.4 microgram/ml at 600 mg/day of OXC to 27.0 microgram/ml at 1800 mg/day of OXC and highly correlated with OXC dose per body weight (r=0.72-84). CONCLUSION: There is no significant change or difference of MHD plasma concentraion between OXC monotherapy and polytherapy with valproic acid at the same dose of OXC. THe plasma concentration of MHD is highly correlated with OXC dose per body weight.