A novel zein-based dry coating tablet design for zero-order release.

The purpose of this study was to design zero-order release of dry-coated tablets using pure zein powder, zein granule and zein blend containing two common pharmaceutical excipients such as microcrystalline cellulose (MCC) or starch in different proportions as coating material. The 5-fluorouracil (5-FU) was used as a model drug. The physical characterization and drug release behaviors of dry-coated tablets were investigated. The surface structure of the tablets was examined by a scanning electron microscopy. The correlation coefficient (R) was used as indicator of the best fitting of the zero-order model for drug release. It was found that zein formed a gelatinous layer fast and its network prevented disintegration of the tablet during dissolution process. Zein-based dry coating tablets had good physical properties such as compactibility and friability. All formulations fit the zero-order model well. The mechanism for zero-order release of these dry-coated tablets was solvent penetration into the dosage form and dissolving the drug, the dissolving core formed an apex in the center of the tablets and the drug diffused out. The apex of zein-coated tablets worked as orifice of an osmotic system and released the drug in zero-order profile.