The contributions of erosion, swelling, and porosity to theophylline release kinetics from Cissus populnea polymer matrices

The variable factors of erosion rate, swelling rate, and porosity were used in studying the release patterns of theophylline from our Cissus populnea polymer (CPP) matrices under the different factor combinations given by a simple 2ⁿ factorial experimental design. The zero-order slopes and correlation coefficients representing release rate and linearity, respectively, as obtained from both the nonsteady state and steady state were statistically treated. It appears that the nonsteady-state analysis is more suitable for studying the effects of individual factors, while the steady-state analysis appears more suitable for studying interaction effects of the factors. The study also showed that erosion is the main mechanism by which theophylline is released from the matrices, while swelling is responsible for maintaining linearity in the zero-order release curves. A careful examination of the statistical results shows some functional relationships between the factors, which should be considered in designing more detailed factorial experiments to enable the establishment of equation models for predicting the release profile of theophylline from our CPP matrices under any given dissolution condition.