In vivo binding characteristics of carbamazepine and carbamazepine-10,11-epoxide to serum proteins in paediatric patients with epilepsy.

The in vivo serum protein binding characteristics of carbamazepine (CBZ) and carbamazepine-10,11-epoxide (CBZ-E) were assessed in sera from 23 paediatric patients on CBZ monotherapy. We assumed that CBZ and CBZ-E binding to serum proteins comprised specific binding sites on alpha 1-acid glycoprotein (AAG) and non-specific binding sites on serum albumin. Therefore, the binding characteristics of each compound were analysed according to specific and nonspecific binding equations. Association constants for drug-AAG binding were 0.096 l.mumol-1 for CBZ and 0.023 l.mumol-1 for CBZ-E. Within the concentration ranges investigated the specific binding of each compound contributes to the drug-serum protein interactions. Age did not show a significant correlation with the serum unbound fraction of each compound.