Freeze-dried pregelatinized Dioscorea starches as tablet matrix for sustained release

Abstract

Freeze dried pregelatinized Dioscorea starches have been evaluated as a directly compressible excipient for sustained release using diclofenac sodium and caffeine as the model drugs. The tableting and tablet properties of the binary and ternary mixtures of the drug/starch/excpients were assessed using the 3-D modeling parameters and the crushing force of the tablets while the drug release properties were also evaluated. The effect of dicalcium phosphate dihydrate on the compaction and drug release properties of the matrices was also investigated. The results obtained indicate the tablet formation properties of the starches depend on the Dioscorea starch used and on the concentration of drug present in the matrix tablets. There appears to be a decrease in the CF of the tablets as the concentration of drug in the matrix is increased. Inclusion of dicalcium phosphate dihydrate in the tablet matrix increased the bonding in the matrix tablets leading to an increase in CF of the tablets. The amount for drug release from the matrices, and the release rates and mechanism were also dependent on the Dioscorea starch used and the drug concentration. Modified Bitter matrices provided a controlled release of diclofenac for up to 5 hours while modified Chinese starches provided controlled release for over 24 hours. The release mechanism from modified Chinese matrices was found to be Super Case-II transport or time-independent release kinetics. Furthermore, the release rates were dependent on the concentration of the drug present in the matrix. Thus, the modified starch matrices could be used to achieve different drug release profiles depending on the intended use of the tablets. The addition of dicalcium phosphate dihydrate not only improved the mechanical properties of the tablets but also altered the release rates and kinetics. Thus, modified Chinese and Bitter could find application as excipient for controlled drug delivery.