title: The Influence of High Drug Loading in Xanthan Tablets and Media with Different Physiological pH and Ionic Strength on Swelling and Release.
abstract: The formation of a gel coat around xanthan (Xan) tablets, empty or loaded with pentoxifylline (PF), and its release in media differing in pH and ionic strength by NMR, MR imaging, and two release methods were studied. The T1 and T2 NMR relaxation times in gels depend predominantly on Xan concentration; the presence of PF has negligible influence on them. It is interesting that the matrix swelling is primarily regulated by Xan despite high drug loading (25%, 50%). The gastric pH and high ionic strength of the media do not influence the position of the penetration and swelling fronts but do affect the erosion front and gel thickness. The different release profiles obtained in mixing and nonmixing in vitro methods are the consequence of matrix hydration level and erosion at the surface. In water and in diluted acid medium with low ionic strength, the main release mechanism is erosion, whereas in other media (pH 1.2, μ ≥ 0.20 M), anomalous transport dominates as was found out by fitting of measured data with theoretical model. Besides the in vitro investigation that mimics gastric conditions, mathematical modeling makes the product development more successful.
authors: Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
authors: Urša
authors: U
authors: Mikac
authors: Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
authors: Ana
authors: A
authors: Sepe
authors: Faculty of Pharmacy, University of Ljubljana , 1000 Ljubljana, Slovenia.
authors: Saša
authors: S
authors: Baumgartner
authors: Faculty of Pharmacy, University of Ljubljana , 1000 Ljubljana, Slovenia.
authors: Julijana
authors: J
authors: Kristl
mesh_terms: D004337:Drug Carriers; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D009994:Osmolar Concentration; D004364:Pharmaceutical Preparations / Q000008:administration & dosage* / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D012995:Solubility; D013607:Tablets / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D004337:Drug Carriers; D004364:Pharmaceutical Preparations; D011135:Polysaccharides, Bacterial; D013607:Tablets; D014867:Water; C002563:xanthan gum
keywords: drug release mechanisms; gel thickness; magnetic resonance imaging; mathematical modeling; matrix tablets; oral drug formulations; pH-controlled release