Hydrophilic matrices: Application of Placket–Burman screening design to model the effect of POLYOX–carbopol blends on drug release

The aim of the present study was to screen the effect of seven factors – POLYOX molecular weight (X1) and amount (X2); carbopol (X3), lactose (X4), sodium chloride (X5), citric acid (X6); compression pressure (X7) – on (1) the release of theophylline from hydrophilic matrices, demonstrated by changes in dissolution rate, and (2) their impact on the release exponent [n] indicative of the drug transport mechanism through the diffusion matrix. This objective was accomplished utilizing the Placket–Burman screening design. Theophylline tablets were prepared according to a 7-factor–12-run statistical model and subjected to a 24-h dissolution study in phosphate buffer at pH 7.2. The primary response variable, Y4, was the cumulative percent of theophylline dissolved in 12 h. The regression equation for the response was Y4 = 66.2167 − 17.5833X1 − 3.3833X2 − 9.366X3 − 1.1166X4 − 0.6166X5 + 2.6X6 − 2.783X7. This polynomial model was validated by the ANOVA and residual analysis. The results showed that only two factors (X2 and X3) had significant effect (p-value < 0.10) on theophylline release from the hydrophilic polymer matrix. Factors (X2 and X7) had significant effect (p-value < 0.10) on [n], the exponent.