title: Magnetic resonance microscopy for assessment of morphological changes in hydrating hydroxypropylmethylcellulose matrix tablets in situ-is it possible to detect phenomena related to drug dissolution within the hydrated matrices?
abstract: OBJECTIVE
  So far, the hydrated part of the HPMC matrix has commonly been denoted as a "gel" or "pseudogel" layer. No MRI-based results have been published regarding observation of internal phenomena related to drug dissolution inside swelling polymeric matrices during hydration. The purpose of the study was to detect such phenomena.
  
  
  METHODS
  Multiparametric, spatially and temporally resolved T2 MR relaxometry, in situ, was applied to study formation of the hydration progress in HPMC matrix tablets loaded with L-dopa and ketoprofen using a 11.7 T MRI system. Two spin-echo based pulse sequences were used, one of them specifically designed to study short T2 signals.
  
  
  RESULTS
  Two components in the T2 decay envelope were estimated and spatial distributions of their parameters, i.e. amplitudes and T2 values, were obtained. Based on the data, different region formation patterns (i.e. multilayer structure) were registered depending on drug presence and solubility. Inside the matrix with incorporated sparingly soluble drug a specific layer formation due to drug dissolution was detected, whereas a matrix with very slightly soluble drug does not form distinct external "gel-like" layer.
  
  
  CONCLUSIONS
  We have introduced a new paradigm in the characterization of hydrating matrices using (1)H MRI methods. It reflects molecular mobility and concentration of water inside the hydrated matrix. For the first time, drug dissolution related phenomena, i.e. particular front and region formation, were observed by MRI methods.
authors.affiliation: Department of Magnetic Resonance Imaging, Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342, Kraków, Poland, Piotr.Kulinowski@ifj.edu.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Kulinowski
authors.forename: Anna
authors.initials: A
authors.lastname: Młynarczyk
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Jasiński
authors.forename: Przemysław
authors.initials: P
authors.lastname: Talik
authors.forename: Marco L H
authors.initials: ML
authors.lastname: Gruwel
authors.forename: Bogusław
authors.initials: B
authors.lastname: Tomanek
authors.forename: Władysław P
authors.initials: WP
authors.lastname: Węglarz
authors.forename: Przemysław
authors.initials: P
authors.lastname: Dorożyński
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000737:chemistry; D000978:Antiparkinson Agents / Q000008:administration & dosage / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000032:analysis*; D065347:Hypromellose Derivatives / Q000032:analysis*; D007660:Ketoprofen / Q000008:administration & dosage / Q000737:chemistry; D007980:Levodopa / Q000008:administration & dosage / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008853:Microscopy / Q000379:methods*; D012995:Solubility; D013607:Tablets
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000978:Antiparkinson Agents; D003692:Delayed-Action Preparations; D013607:Tablets; D065347:Hypromellose Derivatives; D007980:Levodopa; D007660:Ketoprofen