Chitosan Based Unidirectional Release Buccal Patches of Carbamazepine: Formulation Development and In Vitro, Ex Vivo Characterization

The unidirectional release buccal patches of carbamazepine (CBZ) were designed in total of 36 formulations using a 32 full factorial design. Different hydrophilic polymers were used in the formulation along with chitosan-HPMC matrix. The thickness of the prepared patches varied between 0.3 ± 0.10 and 0.5 ± 0.15 mm. The mass of the patches varied from 142.4 ± 0.22 and 160.2 ± 0.13 mg. The pH of the prepared patches was in the range of 4.9±0.01 to 6.2±0.06. The drug loading efficiency of the patches varied between 18.1±0.5 and 19.8±0.1 and showed folding endurance of ˃188. Out of these 36 formulations, five formulations (FA42, FA46, FB38, FB49 and FB52) showed high folding endurance of ˃255. These patches were selected for further evaluation such as swelling studies, ex vivo mucoadhesion time, ex vivo mucoadhesive strength, in vitro drug release, ex vivo permeation, accelerated stability studies, DSC, FTIR and X-ray diffraction spectral studies. The percentage of swelling was higher up to 53 ± 1.1 for FB49 after 160 min. The percentage swelling was increased in the following order, FA42 < FB38 < FA46 < FB52 < FB49. The ex vivo mucoadhesion time of selected buccal patches was in the range of 112 ± 3.9 to 167 ± 3.1 min. The highest mucoadhesive force was observed with formulation FA42. In vitro release revealed that formulation FB49 showed maximum release of 99.9% after 90 min and followed by FB52 (105 min), FA46 (135 min), FB38 and FA42 (150 min). CBZ permeation through the porcine buccal mucosa was investigated by using Franz diffusion cell. There was a good correlation between in vitro drug release and ex vivo permeation studies. The accelerated stability study of tested patches showed no significant change in drug content, mucoadhesion time and surface pH, observed in the beginning of the study.