ABSTRACT
The rate of drug release from solid dosage forms depends on the dissolution rate. In the case of solutions, it depends on the rate of diffusion. Present technology utilizes either of these possibilities alone or in combination. Slowed diffusion can be obtained by limiting possibilities of drug molecule movement in the molecular dispersed state. In formulation of extended-release dosage forms, this principle is often employed alone or supplementary to the extended solubility principle. Dissolution rate is proportional to the solid solute surface, which should be taken into account in extended-release dosage formulation, since it is related to particle size of drug and dosage-form behavior in an organism. Dissolution rate is proportional to the diffusion coefficient, therefore it is proportional to the viscosity of the solution surrounding the dissolved substance, and its molecular mass.
