title: Modelling of diclofenac sodium diffusion from swellable and water-soluble polyethylene oxide matrices.
abstract: OBJECTIVE
  The main objective of this study was to develop a mathematical model for the characterization of diclofenac sodium diffusion from polyethylene oxide (PEO) matrices. A model was developed on the basis of the diffusion theory accounting for the characteristics of the polymer: swelling with subsequent dissolution in water. The concentration-dependent diffusion of drug and water was taken into account. Experimental data were analysed using a computer software program as an aid for solving partial differential equations.
  
  
  METHODS
  Six formulations of matrix tablets with different drug-excipient ratios were prepared using low-molecular-weight PEO as a matrix-forming material. For obtaining drug release data, dissolution studies were performed and water uptake by pure PEO matrices was studied as well.
  
  
  RESULTS
  A good agreement of the developed model with experimental results was demonstrated. Some anomalies in drug diffusion were observed and their origin was questioned. Changes in the parameters characterizing the process of diffusion are attributed to glassy-rubbery polymer transitions. Additional interpretation of this phenomenon on the basis of percolation theory is also provided.
  
  
  CONCLUSIONS
  The obtained model has the ability to predict the required characteristics of matrices for desired drug release. The composition of batches with undesirable release properties can be predetermined and avoided in manufacturing.
authors.affiliation: Institute of Pharmaceutical Technology, Faculty of Pharmacy, Belgrade, Serbia. jpetrovic@pharmacy.bg.ac.rs
authors.forename: Jelena
authors.initials: J
authors.lastname: Petrović
authors.forename: Jelena
authors.initials: J
authors.lastname: Jocković
authors.forename: Svetlana
authors.initials: S
authors.lastname: Ibrić
authors.forename: Zorica
authors.initials: Z
authors.lastname: Durić
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D004008:Diclofenac / Q000737:chemistry*; D004058:Diffusion; D016503:Drug Delivery Systems / Q000592:standards*; D005079:Excipients / Q000737:chemistry* / Q000592:standards; D008962:Models, Theoretical; D008970:Molecular Weight; D011092:Polyethylene Glycols; D012995:Solubility; D013607:Tablets / Q000737:chemistry* / Q000592:standards; D014867:Water
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D005079:Excipients; D013607:Tablets; D014867:Water; D004008:Diclofenac; D011092:Polyethylene Glycols