title: Atypical effects of incorporated surfactants on stability and dissolution properties of amorphous polymeric dispersions.
abstract: OBJECTIVE
  To understand the impact of ionic and non-ionic surfactants on the dissolution and stability properties of amorphous polymeric dispersions using griseofulvin (GF) as a model for poorly soluble drugs.
  
  
  METHODS
  Solid dispersions of the poorly water-soluble drug, griseofulvin (GF) and the polymers, poly(vinylpyrrolidone) (PVP) and poly(2-hydroxypropyl methacrylate) (PHPMA), have been prepared by spray drying and bead milling and the effect of the ionic and non-ionic surfactants, namely sodium dodecyl sulphate (SDS) and Tween-80, on the physico-chemical properties of the solid dispersions studied.
  
  
  RESULTS
  The X-ray powder diffraction data and hot-stage microscopy showed a fast re-crystallisation of GF. While dynamic vapour sorption (DVS) measurements indicated an increased water uptake, slow dissolution rates were observed for the solid dispersions incorporating surfactants. The order by which surfactants free dispersions were prepared seemed critical as indicated by DVS and thermal analysis. Dispersions prepared by milling with SDS showed significantly better stability than spray-dried dispersions (drug remained amorphous for more than 6 months) as well as improved dissolution profile.
  
  
  CONCLUSIONS
  We suggest that surfactants can hinder the dissolution by promoting aggregation of polymeric chains, however that effect depends mainly on how the particles were prepared.
authors.affiliation: The School of Pharmacy, University of Reading, Reading, UK. h.al-obaidi@reading.ac.uk.
authors.forename: Hisham
authors.initials: H
authors.lastname: Al-Obaidi
authors.affiliation: Institute of Pharmaceutical Science, King's College London, London, UK.
authors.forename: M Jayne
authors.initials: MJ
authors.lastname: Lawrence
authors.affiliation: The School of Pharmacy, University College London, London, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Buckton
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D004339:Drug Compounding; D004355:Drug Stability; D006118:Griseofulvin / Q000737:chemistry*; D007700:Kinetics; D008853:Microscopy; D008956:Models, Chemical; D011109:Polymethacrylic Acids / Q000737:chemistry*; D011136:Polysorbates / Q000737:chemistry*; D011205:Povidone / Q000737:chemistry*; D033362:Powder Diffraction; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D012995:Solubility; D013501:Surface-Active Agents / Q000737:chemistry*; D013678:Technology, Pharmaceutical / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D011109:Polymethacrylic Acids; D011136:Polysorbates; D013501:Surface-Active Agents; D014867:Water; D006118:Griseofulvin; D012967:Sodium Dodecyl Sulfate; D011205:Povidone
keywords: dissolution rate; glass transition temperature; globules; solid dispersions; spray drying; surfactants