Abstract:
The present investigation describes the influence of the high substituted hydroxypropyl cellulose (HPC-H) and guar gum on release behavior and kinetics of theophylline sustained release tablets using 3² full factorial design. The amounts of Guar Gum (X1) and HPC-H (X2) were selected as an independent variables and drug release at 1hr (Q₁) and at 8hr (Q₈) and time required for 50% drug release (T_50%) were selected as a dependent variable. Theophylline tablets were prepared by direct compression method using HPC-H with Guar Gum as release retardant in different proportions and MCC as directly compressible filler-binder. The parameter optimized using 3² factorial designs. The tablets of all batches were evaluated for various evaluation parameters. Different dissolution models were applied to drug release data in order to evaluate release mechanisms and kinetics. Regression analysis and response surface analysis were performed for dependent variables. The FTIR study was carried out for drug excipient compatibility Studies. The initial release was sufficiently higher in all formulations thus ruling out the need to incorporate a specific loading dose. Thus, the use of suitable polymer combinations that could provide initial higher release and release extension up to 12 hr. It was observed that type and ratio of polymer had significant influence on Q₈, without significant influence on Q₁ and T_50%. Mathematical treatment of the in vitro drug release data suggests that, the drug release of all the formulations followed Korsmeyer-peppas model, the release exponent n<0.5 indicate that drug diffuses through the polymeric matrix by a Fickian (case I) diffusion mechanism. 

Keywords: 3² Full Factorial Design, Release Kinetics, Sustained Release, Response Surface Plot.