title: Impact of HPMC on the physical properties of spray-congealed PEG microparticles and its swelling effect on rifampicin dissolution.
abstract: BACKGROUND
  Many active substances are poorly water-soluble and pose a great challenge when orally administered because drug bioavailability is largely dependent on its solubility.
  
  
  OBJECTIVE
  The objective of this investigation was to evaluate the effect of hydroxypropyl methylcellulose (HPMC) as an additive on the physical properties of spray-congealed polyethylene glycol (PEG) microparticles.
  
  
  METHODS
  The effects of four viscosity grades of HPMC (K100 LV, K4M, K15M and K100M) on the spray-congealing process yield and physical properties of spray-congealed microparticles, such as morphology and particle size, were studied. The swelling effect of HPMC on drug release was also explored using surface plots.
  
  
  CONCLUSIONS
  Molten mixtures containing PEG and HPMC of various grades and concentrations were successfully spray-congealed with useful yield ranging from 42.6% to 58.4%. Smooth and spherical microparticles were produced and their size was found to increase with increasing feed viscosity. The swelling extent of microparticles was found to be influenced by the grade, particle size and amount of HPMC present while the rate of erosion depended on the formation of the barrier and grade of HPMC used. Formulations with appropriate rates of erosion were selected to prepare microparticles with rifampicin (RIF), a poorly water-soluble drug. At 10% (w/w), K100 LV was found to enhance the dissolution of RIF while K15M retarded the release.
  
  
  CONCLUSIONS
  The novel application of HPMC as an additive in spray-congealed PEG microparticles not only affected the physical properties of the microparticles but also modified the drug release by its swelling effect.
authors.affiliation: a GEA-NUS Pharmaceutical Processing Research Laboratory, Department of Pharmacy, Faculty of Science, National University of Singapore , Singapore , Singapore.
authors.forename: Ching Mien
authors.initials: CM
authors.lastname: Oh
authors.affiliation: a GEA-NUS Pharmaceutical Processing Research Laboratory, Department of Pharmacy, Faculty of Science, National University of Singapore , Singapore , Singapore.
authors.forename: Carin
authors.initials: C
authors.lastname: Ru Shan Siow
authors.affiliation: a GEA-NUS Pharmaceutical Processing Research Laboratory, Department of Pharmacy, Faculty of Science, National University of Singapore , Singapore , Singapore.
authors.forename: Paul Wan Sia
authors.initials: PW
authors.lastname: Heng
authors.affiliation: a GEA-NUS Pharmaceutical Processing Research Laboratory, Department of Pharmacy, Faculty of Science, National University of Singapore , Singapore , Singapore.
authors.forename: Lai Wah
authors.initials: LW
authors.lastname: Chan
mesh_terms: D002626:Chemistry, Pharmaceutical / Q000379:methods*; D065546:Drug Liberation; D065347:Hypromellose Derivatives / Q000737:chemistry* / Q000493:pharmacokinetics; D008863:Microspheres; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000493:pharmacokinetics; D012293:Rifampin / Q000737:chemistry* / Q000493:pharmacokinetics; D012995:Solubility; D014783:Viscosity
chemical_list: D065347:Hypromellose Derivatives; D011092:Polyethylene Glycols; D012293:Rifampin
keywords: Drug release; erosion; hydroxypropyl methylcellulose; microparticle; rifampicin; spray congealing; swelling