Impairment of the in vitro release of carbamazepine from tablets

Carbamazepine belongs to the class II biopharmaceutical classification system (BCS) which is characterized by a high per-oral dose, a low aqueous solubility and a high membrane permeability. The bioavailability of such a drug is limited by the dissolution rate. The present study deals with the formulations of immediate release tablets of poorly soluble carbamazepine. As model tablets for this investigation, two formulations (named "A" and "B" formulations) of carbamazepine tablets labeled to contain 200 mg were evaluated. The aim of this study was to establish possible differences in dissolution profile of these two formulations purchased from the local market. The increased crystallinity together with enlarged particle size, enhanced aggregation and decreased wettability of the drug, resulted in insufficient dissolution rate for formulation "B". From the dissolution point of view, this formulation was inferior to the formulation "A", due to the solubilization effect.