title: Magnetic resonance imaging for the in vivo evaluation of gastric-retentive tablets.
abstract: OBJECTIVE
  To develop a magnetic resonance imaging (MRI) technique for assessing in vivo properties of orally ingested gastric-retentive tablets under physiologic conditions.
  
  
  METHODS
  Tablets with different floating characteristics (tablet A-C) were marked with superparamagnetic Fe3O4 particles to analyze intragastric tablet position and residence time in human volunteers. Optimal Fe3O4 concentration was determined in vitro. Intragastric release characteristic of one slow-release tablet (tablet D) was analyzed by embedding gadolinium chelates (Gd-DOTA) as a drug model into the tablet. All volunteers underwent MRI in the sitting position. Tablet performance was analyzed in terms of relative position of tablet to intragastric meal level (with 100% at meal surface), intragastric residence time (min) and Gd-DOTA distribution volume (% of meal volume).
  
  
  RESULTS
  Intragastric tablet floating performance and residence time of tablets (tablet A-D) as well as the intragastric Gd-DOTA distribution of tablet D could be monitored using MRI. Tablet floating performance was different between the tablets (A, 93%(95 - 9%); B, 80%(80 - 68%): C, 38%(63 - 32%); p < 0.05). The intragastric distribution volume of Gd-DOTA was 19.9% proximally and 35.5% distally.
  
  
  CONCLUSIONS
  The use of MRI allows the assessment of galenic properties of orally ingested tablets in humans in seated position.
authors.affiliation: Biophysics Group, Institute of Biomedical Engineering, University and ETH Zurich Gloriastrasse, 35 CH-8092 Zurich, Switzerland. steingoetter@biomed.ee.ethz.ch
authors.forename: Andreas
authors.initials: A
authors.lastname: Steingoetter
authors.forename: Dominik
authors.initials: D
authors.lastname: Weishaupt
authors.forename: Patrick
authors.initials: P
authors.lastname: Kunz
authors.forename: Karsten
authors.initials: K
authors.lastname: Mäder
authors.forename: Hans
authors.initials: H
authors.lastname: Lengsfeld
authors.forename: Miriam
authors.initials: M
authors.lastname: Thumshirn
authors.forename: Peter
authors.initials: P
authors.lastname: Boesiger
authors.forename: Michael
authors.initials: M
authors.lastname: Fried
authors.forename: Werner
authors.initials: W
authors.lastname: Schwizer
mesh_terms: D003692:Delayed-Action Preparations; D016503:Drug Delivery Systems; D005290:Ferric Compounds / Q000737:chemistry; D006571:Heterocyclic Compounds; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009942:Organometallic Compounds; D013270:Stomach / Q000033:anatomy & histology*; D013607:Tablets
chemical_list: D003692:Delayed-Action Preparations; D005290:Ferric Compounds; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D013607:Tablets; C000499:ferric oxide; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate