title: Adhesion of powders for inhalation: an evaluation of drug detachment from surfaces following deposition from aerosol streams.
abstract: OBJECTIVE
  To evaluate micronized powder retention and detachment from inhaler surfaces following reproducible deposition by impaction, coupled with centrifugal particle detachment (CPD).
  
  
  METHODS
  Micronized albuterol sulfate (AS) and beclomethasone dipropionate (BDP) were aerosolized as dry powders and deposited by cascade impaction onto different contact surfaces. Drug detachment from the surfaces was characterized using CPD, coupled with HPLC assay and scanning electron microscopy.
  
  
  RESULTS
  Drugs which accumulated as aggregates on model surfaces detached with distinctive profiles for % remaining vs. applied centrifugal force; each profile showed reproducible values for the minimum force required to initiate drug detachment, Fyield. While differences occurred in the observed detachment profiles for different drugs and contact surfaces (polyacetal vs. aluminum), the deposited drug particle size had the most significant effect on these profiles, e.g., Fyield for AS (2.1-3.3 microm) was 383 +/- 12.7 microN compared with 18 +/- 13.8 microN for AS (4.7-5.8 microm).
  
  
  CONCLUSIONS
  A technique was developed which enabled the experimental review, and subsequent data analysis, of the adhesive properties between different DPI construction materials and drug substances deposited from aerosol clouds. The technique appears to be of greater relevance to inhaler design decisions than earlier studies in the literature claiming to show differences in the adhesion of single drug particles to surfaces.
authors.affiliation: Aerosol Research Group, School of Pharmacy, Virginia Commonwealth University, Richmond 23298-0533, USA.
authors.forename: Martyn J
authors.initials: MJ
authors.lastname: Clarke
authors.forename: Joanne
authors.initials: J
authors.lastname: Peart
authors.forename: Stefano
authors.initials: S
authors.lastname: Cagnani
authors.forename: Peter R
authors.initials: PR
authors.lastname: Byron
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D000280:Administration, Inhalation; D000336:Aerosols / Q000737:chemistry; D004353:Drug Evaluation, Preclinical / Q000379:methods* / Q000706:statistics & numerical data; D009330:Nebulizers and Vaporizers / Q000706:statistics & numerical data; D011208:Powders / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000269:Adhesives; D000336:Aerosols; D011208:Powders