Effect of different polymers on the release characteristics of carbamazepine from stable controlled-release tablets prepared by the air suspension and wet granulation techniques

The purpose of this work was to develop the controlled-release (CR) carbamazepine tablets using ethylcellulose and acrylic resins (Eudragits® RSPO and S100) as retardant polymers. Two different procedures were utilized. In method I, the prepared carbamazepine granules were coated with different polymers by the air suspension (Wurster) technique and then compressed into 24 h CR tablets. However, in method II, a wet granulation procedure was used to prepare the 12 h controlled-release matrix tablets. Both the wet granulation and air suspension (Wurster) techniques were found to be reliable methods for the preparation of carbamazepine controlled-release tablets. Triethylcitrate (TEC) was used as plasticizer in all prepared formulations. The release properties of the resulting tablets were evaluated in hydrochloric acid buffer (pH 2.5), acetate buffer (pH 4.5), and phosphate buffers (pH 6.8 and 7.5). The concentration of the polymer was the drug release rate determining factor. One commercially available brand of carbamazepine CR tablets was included into the study for comparison. The release patterns were analyzed from the standpoint of the diffusion-controlled process as well as zero-order and first-order kinetics. The influence of storage conditions (temperature and relative humidity) on the release of carbamazepine from 12 h CR tablets containing Eudragits® RSPO+S100 was evaluated. These tablets were found stable when stored under stress conditions.