SUSTAINED-RELEASE MECHANISMS OF WAX MATRIX SYSTEM FOR CONTROLLED-RELEASE

In order to elucidate the influence of the particle size of water-soluble ingredients in a wax matrix and the solubility of drugs on the drug dissolution rate from a dosage form, reservoir devices were prepared from a wax matrix layer consisting of hydrogenated easter oil (HCO) and lactose, a drug reservoir and a water non-permeable layer of HCO, and dissolution tests were then carried out. Drug permeability and water penetrability of the wax matrix layer were affected by the particle size of lactose incorporated into the wax matrix layer. Drug permeability and water penetrability could be decreased by using smaller lactose particles. Tortuosity in the wax matrix layer after the dissolution of lactose could be increased inversely proportional to the particle size. Permeability of the wax matrix layer differed depending on the kinds of drugs forming the drug reservoir, which was attributed to differences in the solubility and viscosity of the drug saturated solution formed in the drug reservoir.