title: Programmed diffusional release rate from encapsulated cosolvent system.
abstract: The programmed diffusional release rate of an active agent through a rate-controlling membrane from a cosolvent system is discussed. At initial conditions, the drug is present below saturation in solution in a solvent mixture, enclosed by the rate-controlling membrane; the solvent is composed of the main solvent and a consolvent, which increases the drug solubility in the main solvent. During operation, the active agent and cosolvent diffuse from the capsule at a rate controlled by the membrane. Equations were derived describing the release rate of the active agent as a function of the permeability of the cosolvent and agent, the capsule dimensions, and the system's initial conditions. A great variety of release rate profiles can be programmed from declining to increasing delivery rate patterns as a function of time. Experimental data are presented for the drug progesterone in solution in cyclohexane with methyl, heptyl, or cetyl alcohol as the cosolvent in a polyethylene capsule. The theory qualitatively predicts the theory qualitatively predicts the experimental results.
mesh_terms: D000438:Alcohols; D002214:Capsules; D003510:Cyclohexanes; D004058:Diffusion; D007700:Kinetics; D008567:Membranes, Artificial; D008956:Models, Chemical; D010539:Permeability; D011374:Progesterone; D012995:Solubility
chemical_list: D000438:Alcohols; D002214:Capsules; D003510:Cyclohexanes; D008567:Membranes, Artificial; D011374:Progesterone