title: Effect of hydrophobic inclusions on polymer swelling kinetics studied by magnetic resonance imaging.
abstract: The rate of drug release from polymer matrix-based sustained release formulations is often controlled by the thickness of a gel layer that forms upon contact with dissolution medium. The effect of formulation parameters on the kinetics of elementary rate processes that contribute to gel layer formation, such as water ingress, polymer swelling and erosion, is therefore of interest. In the present work, gel layer formation has been investigated by magnetic resonance imaging (MRI), which is a non-destructive method allowing direct visualization of effective water concentration inside the tablet and its surrounding. Using formulations with Levetiracetam as the active ingredient, HPMC as a hydrophilic matrix former and carnauba wax (CW) as a hydrophobic component in the matrix system, the effect of different ratios of these two ingredients on the kinetics of gel formation (MRI) and drug release (USP 4 like dissolution test) has been investigated and interpreted using a mathematical model.
authors.affiliation: Department of Chemical Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
authors.forename: Michaela
authors.initials: M
authors.lastname: Gajdošová
authors.affiliation: Zentiva, k.s., U Kabelovny 130, Prague 10, Czech Republic.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pěček
authors.affiliation: Department of Chemical Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
authors.forename: Nina
authors.initials: N
authors.lastname: Sarvašová
authors.affiliation: Department of Chemical Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Grof
authors.affiliation: Department of Chemical Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic. Electronic address: Frantisek.Stepanek@vscht.cz.
authors.forename: František
authors.initials: F
authors.lastname: Štěpánek
mesh_terms: D003692:Delayed-Action Preparations / Q000737:chemistry; D065546:Drug Liberation; D057927:Hydrophobic and Hydrophilic Interactions; D065347:Hypromellose Derivatives / Q000737:chemistry*; D007700:Kinetics; D000077287:Levetiracetam; D008279:Magnetic Resonance Imaging; D008962:Models, Theoretical; D010889:Piracetam / Q000031:analogs & derivatives / Q000737:chemistry; D012995:Solubility; D013607:Tablets; D014885:Waxes / Q000737:chemistry*
chemical_list: D003692:Delayed-Action Preparations; D013607:Tablets; D014885:Waxes; D065347:Hypromellose Derivatives; D000077287:Levetiracetam; C026344:carnauba wax; D010889:Piracetam
keywords: Carnauba wax; Drug dissolution; Gel layer; HPMC; MRI