Investigation of In vitro Release Kinetics of Carbamazepine from Eudragit® RS PO and RL PO Matrix Tablets

Purpose: The objective of this research work was to prepare and evaluate the effect of Eudragit RS PO and Eudragit RL PO polymers on the physical property and release characteristics of carbamazepine matrix tablets. Methods: Matrix tablets containing carbamazepine were prepared with Eudragit® RS PO alone as the rate-retarding polymer (coded batch series ‘A’) and also with a combination of Eudragit® RS PO and RL PO (coded batch series ‘B’). The tablets were characterized for hardness as well as for carbamazepine release. The release data were subjected to different models in order to evaluate their release kinetics and mechanisms. Results: The hardness of batch series ‘A’ matrix tablet was >160 kg/cm2 while for batch series ‘B’, it was >170 kg/cm2. Carbamazepine tablets containing only Eudragit RS PO showed very slow release (less than 6% in 8 h) but when Eudragit RL PO was blended with Eudragit RS PO, the release rate improved significantly to 44% in 24 h (p < 0.05). Drug release mechanism was a complex mixture of diffusion and erosion. Conclusion: Carbamazepine matrix tablets of satisfactory hardness were produced. Furthermore, by blending Eudragit RS PO with Eudragit RL PO in the matrix, tablets of varying release characteristics can be prepared.