Risperidone mucoadhesive buccal tablets: formulation design, optimization and evaluation

The aim of this study was to design and optimize risperidone (RIS) mucoadhesive buccal tablets for systemic delivery as an alternative route. Direct compression method was used for the preparation of buccal tablets, and screening studies were conducted with different polymers to determine their effects on tablet characteristics. Carbopol® (CP) and sodium alginate (SA) were selected as two polymer types for further optimization studies by applying response surface methodology. Tablet hardness (TH), ex vivo residence time (RT), and peak detachment force (DF) from buccal mucosa were selected as three important responses. Physicochemical compatibility of formulation excipients and RIS was evaluated by using Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) analysis. In vitro drug release profiles and release kinetics were investigated; swelling index and matrix erosion studies were conducted. Optimum formulation consisted of 16.4% CP and 20.3% SA, which provided 7.67±0.29 hour ex vivo RT, 45.52±4.85 N TH, and 2.12±0.17 N DF. FT-IR spectroscopy and DSC analysis revealed that there was no chemical interaction present between tablet ingredients. Cumulative RIS release of >90% was achieved after 8 hours of in vitro dissolution studies, which was supported by swelling and matrix erosion analysis. Mechanism of RIS release was fitted best to zero-order model, while release exponent (n) value of 0.77 demonstrated an anomalous (non-Fickian) release, indicating combined erosion and swelling mechanism. The results suggested that optimized buccal tablets of RIS would be a promising and alternative delivery system for the treatment of schizophrenia.