Abstract
A controlled-release matrix filler was prepared by spray-drying a heated aqueous hydroxypropymethylcellulose (HPMC) solution suspending microcrystalline cellulose (MCC, PH101). Acetaminophen tablets (used as model drug, content=50%) were prepared by directly compressing the mixture of drug and spray-dried matrix filler. When HPMC was formulated with more than 10% of the matrix filler, drug release from the tablets was satisfactorily sustained. To obtain a similar sustained-release pattern with unmodified original HPMC, more than 50% of the matrix filler was required in the formulation. Whereas, when the tablet formulation was less that 5% modified HPMC, the drug was rapidly released from the tablets. Uniformly distributed HPMC in the spray-dried filler should lead to such drug-releasing behaviors. The micromeritic properties of HPMC in the matrix filler, viz. particle size, size distribution and the loading amount of HPMC, were main factors in determining the drug-release properties of the tablets. The drug-release rate of the tablets was determined by the erosion rate of the gelled HPMC formed on the surface of the tablets. The drug-release kinetics were described as a function of the cube root of the tablet weight. The drug was tabletted directly with the modified matrix filler by a rotary tabletting machine.
