Pharmacokinetic interactions of carbamazepine with some antiepileptic drugs during epilepsy treatment in children and adolescents
Steinborn B

Purpose: The aim of the study was to obtain pharmacokinetic data for carbamazepine (CBZ) and its fractions not bound with proteins in bitherapy with lamotrigine (LTG), topiramate (TPM), vigabatrin (VGB) or valproic acid (VPA) in children and adolescents treated for epilepsy.
Material and methods: The participants of the presented investigations were fifty-five patients with epilepsy who were under control of The Department of Developmental Neurology, University of Medical Sciences in Pozna. All of patients were treated with CBZ in bitherapy with LTG, TPM, VGB or VPA. The blood samples were taken under steady-state conditions, before the morning dose and subsequently every 3 or 2 for 24 h. The plasma levels of CBZ were determined using TDX analyzer (Abbott Diagnostic Division, USA). Free CBZ fraction was isolated with the use of ultrafiltration system (Amicon, USA). For pharmacokinetic calculations of total and free CBZ, one-compartment model was used according to standardized procedure.
Results: No significant differences in pharmacokinetic parameters of unbound CBZ in four groups of patients on bitherapy with CBZ and LTG, TPM, VGB or VPA were found. The changes in pharmacokinetics of total CBZ were related with difference in CBZ concentrations, area under curve (AUC), L/D/kg ratios and clearance (Cl)/kg. CBZ+VGB bitherapy led to higher total CBZ concentrations. In the group on bitherapy with CBZ+VPA, no increase in unbound CBZ was detected. 
Conclusions: Pharmacokinetic interactions of CBZ with LTG, TPM, VGB or VPA in children are associated only with the changes in total CBZ parameters.