title: Using quantitative magnetic resonance methods to understand better the gel-layer formation on polymer-matrix tablets.
abstract: BACKGROUND
  Magnetic resonance imaging is a powerful, non-invasive technique that can help improve our understanding of the hydrogel layer formed on swellable, polymer-matrix tablets, as well as the layer's properties and its influence on drug release.
  
  
  METHODS
  In this paper, the authors review the NMR and MRI investigations of hydrophilic, swellable polymers published since 1994. The review covers NMR studies on the properties of water and drugs within hydrated polymers. In addition, MRI studies using techniques for determining the different moving-front positions within the swollen tablets, the polymer concentration profiles across them, the influence of the incorporated drug, and so on, are presented. Some complementary methods are also briefly presented and discussed.
  
  
  CONCLUSIONS
  Using MRI, the formation of a hydrogel along with simultaneous determination of the drug's position within it can be observed non-invasively. However, the MRI parameters can influence the signal's intensity and therefore they need to be considered carefully in order to prevent any misinterpretation of the results. MRI makes possible an in situ investigation of swollen-matrix tablets and provides valuable information that can lead, when combined with other techniques, to a better understanding of polymeric systems and a more effective development of optimal dosage forms.
authors.affiliation: Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
authors.forename: Urša
authors.initials: U
authors.lastname: Mikac
authors.forename: Julijana
authors.initials: J
authors.lastname: Kristl
authors.forename: Saša
authors.initials: S
authors.lastname: Baumgartner
mesh_terms: D004337:Drug Carriers / Q000737:chemistry*; D005079:Excipients; D005782:Gels / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011108:Polymers / Q000737:chemistry*; D013607:Tablets / Q000737:chemistry*
chemical_list: D004337:Drug Carriers; D005079:Excipients; D005782:Gels; D011108:Polymers; D013607:Tablets