title: Konjac glucomannan and konjac glucomannan/xanthan gum mixtures as excipients for controlled drug delivery systems. Diffusion of small drugs.
abstract: Konjac glucomannan (KGM), alone or in combination with xanthan gum (XG), was evaluated as main component of systems capable of controlling the diffusion of small molecules with a view of their use in drug delivery. To provide the study with enough general character, KGM batches were obtained from the three main areas of excipient harmonization (Europe, USA and Japan). The rheological evaluation at physiological temperature of KGM (0.5%, w/v) aqueous dispersions, with or without XG at different ratios, showed significant variability among the three KGMs owing to differences in the acetylation degree. The Japanese and European varieties of KGM synergically interact with XG giving rise to gel formation; the synergism being maximum at a 1:1 ratio. By contrast, the American KGM does not show such effect forming only viscous solutions. Drug diffusion coefficients of theophylline and diltiazem HCl, with different molecular size and net charge, were evaluated in systems containing KGM/XG ratio 1:1. KGM/XG systems were more efficient than the XG alone dispersion for controlling drug diffusion of small molecules because of the gel formation. These results point out the potential of mixtures of some KGM types with XG to develop delivery systems capable of maintaining physical integrity and drug release control for up to 8-h period.
authors.affiliation: Departamento Farmacia y Tecnología Farmacéutica, Facultad de Farmacia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: Felipe
authors.initials: F
authors.lastname: Alvarez-Manceñido
authors.forename: Mariana
authors.initials: M
authors.lastname: Landin
authors.forename: Igor
authors.initials: I
authors.lastname: Lacik
authors.forename: Ramón
authors.initials: R
authors.lastname: Martínez-Pacheco
mesh_terms: D031056:Amorphophallus / Q000737:chemistry*; D002121:Calcium Channel Blockers / Q000008:administration & dosage / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D002850:Chromatography, Gel; D003692:Delayed-Action Preparations; D004058:Diffusion; D004110:Diltiazem / Q000008:administration & dosage / Q000737:chemistry; D016503:Drug Delivery Systems; D005079:Excipients / Q000737:chemistry*; D008351:Mannans / Q000737:chemistry*; D008970:Molecular Weight; D004364:Pharmaceutical Preparations / Q000737:chemistry; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D012212:Rheology; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013806:Theophylline / Q000008:administration & dosage / Q000737:chemistry; D014783:Viscosity