Formulation, Release Characteristics and Bioavailability Study of Oral Monolithic Matrix Tablets Containing Carbamazepine

This study examined the release of carbamazepine (CBZ) from hydrophobic (Compritol (R) 888 ATO) and hydrophilic-hydrophobic matrix combination (Compritol (R) 888 ATO-hydroxpropyl methylcellulose, HPMC). Hydrophobic matrix tablets were prepared by hot fusion technique, while hydrophilic-hydrophobic matrix tablets were prepared by wet granulation technique. The properties of the compressed matrix tablets were determined according to the US Pharmacopoeia. Both matrix formulations displayed a controlled-release profile when compared to the reference formulation (Tegretol (R) CR 200). The bioavailability of CBZ formulations and Tegretol (R) CR 200 were evaluated in beagle dogs. Carbamazepine presented a significant higher bioavailability from matrix tablets containing hydrophilic polymer (HPMC) than that obtained from Tegretol (R) CR200. The average inter-subject plasma concentration variability CV% was the least with tablet containing hydrophilic polymer (HPMC) and was the highest with Tegretol (R) CR 200 (33.8 and 54.1, respectively). Analysis of variance applied to log AUC(0-alpha) and log C (max) showed statistical significant differences among the three formulations (P < 0.05). Plotting the fraction of CBZ released in vitro and fraction absorbed showed a statistically significant relationship (R-2=0.935-0.975) for the three matrix tablets examined.