Formulation and in vitro assessment of sustained release matrix tablets of atenolol containing Kollidon SR and carnauba wax

The goal of this study was to evaluate the possibility of using Kollidon SR and carnauba wax in sustained release matrix tablets of atenolol obtained by direct compression. The compatibility between atenolol and excipients (microcrystalline cellulose, colloidal silicon dioxide, magnesium stearate, Kollidon SR, and carnauba wax) was demonstrated by differential scanning calorimetry. 100 mg atenolol tablets were prepared by direct compression, using varying amounts of Kollidon SR (20 or 40%) and carnauba wax (5 or 10%), according to a 22 factorial design, resulting in four formulations. The response studied was the dissolution efficiency in 8 h (DE%8 h). Dissolution tests were performed with the paddle method, 50 rpm, 900 ml phosphate buffer, pH 6.8, 37°C. The mathematical model derived from the experimental design indicated that concentrations of Kollidon SR and carnauba wax negatively affected the DE%8h, while the interaction between thereof had a positive effect. The Korsmeyer-Peppas kinetic model described the dissolution curves and evidenced that drug release occurred by Super Case II transport, mostly controlled by erosion of the matrix, for all formulations. In general, the mechanical strength of the tablets was satisfactory (except for one formulation, which had high friability). Our results indicated that matrices combining Kollidon SR and carnauba wax by direct compression are promising for the sustained release of atenolol.