title: Investigation into the effect of varying l-leucine concentration on the product characteristics of spray-dried liposome powders.
abstract: OBJECTIVE
  Spray-dried formulations offer an attractive delivery system for administration of drug encapsulated into liposomes to the lung, but can suffer from low encapsulation efficiency and poor aerodynamic properties. In this paper the effect of the concentration of the anti-adherent l-leucine was investigated in tandem with the protectants sucrose and trehalose.
  
  
  METHODS
  Two manufacturing methods were compared in terms of their ability to offer small liposomal size, low polydispersity and high encapsulation of the drug indometacin.
  
  
  RESULTS
  Unexpectedly sucrose offered the best protection to the liposomes during the spray drying process, although formulations containing trehalose formed products with the best powder characteristics for pulmonary delivery; high glass transition values, fine powder fraction and yield. It was also found that l-leucine contributed positively to the characteristics of the powders, but that it should be used with care as above the optimum concentration of 0.5% (w/w) the size and polydispersity index increased significantly for both disaccharide formulations.
  
  
  CONCLUSIONS
  The method of liposome preparation had no effect on the stability or encapsulation efficiency of spray-dried powders containing optimal protectant and anti-adherent. Using l-leucine at concentrations higher than the optimum level caused instability in the reconstituted liposomes.
authors.affiliation: School of Pharmacy, Queen's University of Belfast, Belfast The School of Pharmacy, University of London, London, UK.
authors.forename: Kun-Hung
authors.initials: KH
authors.lastname: Chen
authors.forename: Wunlapa
authors.initials: W
authors.lastname: Mueannoom
authors.forename: Simon
authors.initials: S
authors.lastname: Gaisford
authors.forename: Vicky L
authors.initials: VL
authors.lastname: Kett
mesh_terms: D004339:Drug Compounding; D016503:Drug Delivery Systems; D004355:Drug Stability; D005079:Excipients / Q000737:chemistry*; D007213:Indomethacin / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D007930:Leucine / Q000737:chemistry*; D008081:Liposomes; D008168:Lung / Q000378:metabolism; D010316:Particle Size; D011208:Powders; D013395:Sucrose / Q000737:chemistry; D014199:Trehalose / Q000737:chemistry
chemical_list: D005079:Excipients; D008081:Liposomes; D011208:Powders; D013395:Sucrose; D014199:Trehalose; D007930:Leucine; D007213:Indomethacin