A comprehensive analysis and optimization of continuous twin-screw granulation processes via sequential experimentation strategy.

Nowadays twin-screw granulation has been emerging as an attractive continuous wet granulation technique. This study was geared towards better process design and understanding with emphasis on bridging the knowledge gap between input and output variables by employing sequential experimentation strategy. A low-dose formulation for granulation experiments contained anhydrous caffeine as the model drug. In the first phase of parameter screening, D-optimal design and stepwise regression were leveraged to develop interaction models following the examination of various quantitative and qualitative factors of potential importance. To maximize the design space dictated by predefined quality target values, several variables were fixed at optimum levels: 700 rpm screw speed, 60° kneading element staggering angle, 5 kneading elements and distributive feed screw in the screw configuration. In the second phase of characterization, response surface design was utilized to investigate the dependence of critical quality attributes of granules and tablets on selected critical process parameters (L/S ratio, throughput and barrel temperature). The results indicated that the influence of throughput and barrel temperature was relatively inferior to L/S ratio. Higher degree of liquid saturation led to granules with narrower size distribution, smaller porosity and enhanced flowability and tablets with declining tensile strength yet slackened drug release.