title: Finite element analysis of the release of slowly dissolving drugs from cylindrical matrix systems.
abstract: Drug release from matrix systems of cylindrical shape is analyzed in detail by using the finite element method. The model used combines the Noyes-Whitney and diffusion equations, and thus takes the effects of a finite dissolution rate into account. The model is valid for all drug solubilities and dissolution rates, and allows accurate predictions of the drug release to be made. Anisotropic drug transport that may result from the manufacturing process is properly accounted for. Model calculations show that a finite dissolution rate may affect the release profile significantly, producing an initial delay. The equivalence between anisotropic release and isotropic release from a matrix with different dimensions is demonstrated. Comparisons are made with the predictions of a recently proposed pseudo-steady state (PSS) analysis of drug release from cylindrical matrices [Y. Zhou, J. S. Chu, T. Zhou, X. Y. Wu, Modeling of dispersed-drug release from two-dimensional matrix tablets, Biomaterials 26 (2005) 945-952]. This comparison reveals that important discrepancies exist between the numerical and analytical results, which are attributed to the simplifying assumption made in the PSS analysis that the region containing solid drug remains cylindrical in shape throughout the release process. The proposed model is shown to describe experimental release data well.
authors.affiliation: Department of Pharmacy, Uppsala University, Uppsala Biomedical Center, P. O. Box 580, SE-751 23 Uppsala, Sweden. Goran.Frenning@farmaci.uu.se
authors.forename: Göran
authors.initials: G
authors.lastname: Frenning
authors.forename: Ulrika
authors.initials: U
authors.lastname: Brohede
authors.forename: Maria
authors.initials: M
authors.lastname: Strømme
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D001241:Aspirin / Q000008:administration & dosage / Q000737:chemistry; D002482:Cellulose / Q000031:analogs & derivatives; D002626:Chemistry, Pharmaceutical / Q000706:statistics & numerical data*; D004058:Diffusion; D004337:Drug Carriers; D020342:Finite Element Analysis; D015233:Models, Statistical; D012995:Solubility; D013607:Tablets
chemical_list: D004337:Drug Carriers; D013607:Tablets; C013517:ethyl cellulose; D002482:Cellulose; D001241:Aspirin