Effect of polymorphism on in vitro in vivo properties of carbamazepine conventional tablets

The objective of the present study was to investigate the effect of polymorphism on in vitro-in vivo properties of carbamazepine (CBZ). For this purpose, three different polymorphs and a dihydrate of CBZ were obtained and the conventional tablets of these crystalline forms at the dose of 200 mg were prepared. The polymorphs were examined by the IR and DSC analysis. The tablets were investigated by the in vitro dissolution test. Tegretol was selected as a reference. The tablets of beta CBZ demonstrated the lowest dissolution rate, while the alpha form tablets exhibited the highest. Dissolution rates were significantly changed by the polymorphic forms of CBZ. Tegretol, bulk powder and beta CBZ tablets were selected for the bioavailability study. Six healthy volunteers participated in an open-randomized cross-over designed clinical trial. After a total blood sampling period of 96 h, plasma levels of CBZ were determined by HPLC analysis by using a CN column and an acetonitril-water (30:70) mobile phase. There were no significant differences between the plasma concentration-time curves of Tegretol, bulk powder and beta CBZ tablets. The only marked difference was the time required to reach plasma peak concentrations.