title: Theoretical analysis of the release of slowly dissolving drugs from spherical matrix systems.
abstract: Drug release from spherical matrix systems has been investigated theoretically, with numerical as well as analytical methods. The model used combines the Noyes-Whitney and diffusion equations, and thus takes the effects of a finite dissolution rate into account. The release profile has been determined numerically, by using well-established FORTRAN routines. An approximate analytical formula for the amount of released drug has been derived, which is valid during the early stages of the release process. This analytical short-time approximation was compared to the numerical result, and to drug release models existing in the literature. From this comparison it was concluded that the analytical approximation provided a good description of the major part of the release profile, irrespective of the dissolution rate. Existing literature models, based on instantaneous dissolution, provided a good description of the release only when drug dissolution proceeded very rapidly in comparison with the diffusion process. Consequently, the new analytical short-time approximation complements the formulas existing in the literature, since it provides a superior description of the release of slowly dissolving drugs.
authors.affiliation: Department of Pharmacy, Uppsala University, P.O. Box 580, SE-751 23 Uppsala, Sweden. Goran.Frenning@farmaci.uu.se
authors.forename: Göran
authors.initials: G
authors.lastname: Frenning
mesh_terms: D000465:Algorithms; D003692:Delayed-Action Preparations; D004058:Diffusion; D007700:Kinetics; D008863:Microspheres; D015233:Models, Statistical; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D012995:Solubility
chemical_list: D003692:Delayed-Action Preparations; D004364:Pharmaceutical Preparations