title: Suitability of caspofungin for aerosol delivery: physicochemical profiling and nebulizer choice.
abstract: BACKGROUND
  Aerosolized antifungal therapy is a promising route of drug delivery for pulmonary aspergillosis due to attainment of high localized concentrations. Caspofungin, a new antifungal agent with proven efficacy against invasive aspergillosis, has ideal potential for aerosolization.
  
  
  OBJECTIVE
  To examine in vitro the suitability of caspofungin for aerosol administration by characterizing factors that influence efficacy and airway tolerance of aerosol delivery: physicochemical properties, aerodynamics of drug particles, and efficiency of nebulizing systems.
  
  
  METHODS
  Physicochemical characteristics of caspofungin solutions (10 mg/mL and 30 mg/mL) were analyzed: osmolality, pH, viscosity, and surface tension. A time-of-flight aerosol spectrometer API Aerosizer was used to determine aerosol particle size and distribution. Drug output was quantified by high-performance liquid chromatography assay. Nebulizer efficiency was measured by drug output and respirable fraction (percentage of aerosolized particles with a 1 to 5 mum aerodynamic diameter) and compared among three jet nebulizer/compressor systems: device 1, Micromist (Hudson RCI; Temecula, CA)/Pulmo-Aide (model 5650D; DeVilbiss; Somerset, PA); device 2, Sidestream MS 2400/Envoy model IRC 1192 (Invacare; Elyria, OH); and device 3, Pari LC Star/Proneb Ultra (Pari Respiratory Equipment; Midlothian, VA).
  
  
  RESULTS
  Caspofungin requires 0.9% NaCl rather than sterile water as the diluent and addition of 0.3N NaOH buffer to adjust acidity of solutions (pH 6.17 to 6.26) in order to achieve optimal physicochemical properties for airway tolerability (osmolality, 150 to 550 milliosmol per kilogram; chloride ion, 31 to 300 mmol/L; and pH 7.4). The drug output rate increased with higher concentrations of drug solution: device 1, 4.0 mg/min vs 12.5 mg/min; device 2, 5.4 mg/min vs 14.7 mg/min; and device 3, 2.3 mg/min vs 12 mg/min, respectively. The percentage of particles within the respirable range varies depending on device and concentration of drug solutions (10 mg/mL vs 30 mg/mL): device 1, 85% vs 38%; device 2, 44% vs 57%; and device 3, 83% vs 93%, respectively.
  
  
  CONCLUSIONS
  Caspofungin solution with adjustments appears to have physicochemical and aerodynamic characteristics suitable for aerosolization when used with either the Pari LC Star/Proneb Ultra or Micromist/Pulmo-Aide devices. Further in vivo testing is warranted.
authors.affiliation: School of Pharmacy, University of Southern California, Los Angeles, 90089, USA. anniew@usc.edu
authors.forename: Annie
authors.initials: A
authors.lastname: Wong-Beringer
authors.forename: Maria Polikandritou
authors.initials: MP
authors.lastname: Lambros
authors.forename: Paul M
authors.initials: PM
authors.lastname: Beringer
authors.forename: David L
authors.initials: DL
authors.lastname: Johnson
mesh_terms: D000935:Antifungal Agents / Q000008:administration & dosage*; D000077336:Caspofungin; D002851:Chromatography, High Pressure Liquid; D054714:Echinocandins; D004867:Equipment Design; D006801:Humans; D055666:Lipopeptides; D009330:Nebulizers and Vaporizers; D009994:Osmolar Concentration; D010316:Particle Size; D010456:Peptides, Cyclic / Q000008:administration & dosage*; D013499:Surface Properties; D013500:Surface Tension; D014783:Viscosity
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D010456:Peptides, Cyclic; D000077336:Caspofungin