title: Investigation of electrostatic behavior of a lactose carrier for dry powder inhalers.
abstract: OBJECTIVE
  This study aims to elucidate the electrostatic behavior of a model lactose carrier used in dry powder inhaler formulations by examining the effects of ambient relative humidity (RH), aerosolization air flow rate, repeated inhaler use, gelatin capsule and tapping on the specific charge (nC/g) of bulk and aerosolized lactose.
  
  
  METHODS
  Static and dynamic electrostatic charge measurements were performed using a Faraday cage connected to an electrometer. Experiments were conducted inside a walk-in environmental chamber at 25 degrees C and RHs of 20% to 80%. Aerosolization was achieved using air flow rates of 30, 45, 60 and 75 L/min.
  
  
  RESULTS
  The initial charges of the bulk and capsulated lactose were a magnitude lower than the charges of tapped or aerosolized lactose. Dynamic charge increased linearly with aerosolization air flow rate and RH. Greater frictional forces at higher air flow rate induced higher electrostatic charges. Increased RH enhanced charge generation. Repeated inhaler use significantly influenced electrostatic charge due to repeated usage.
  
  
  CONCLUSIONS
  This study demonstrated the significance of interacting influences by variables commonly encountered in the use DPI such as variation in patient's inspiratory flow rate, ambient RH and repeated inhaler use on the electrostatic behavior of a lactose DPI carrier.
authors.affiliation: Institute of Chemical and Engineering Sciences, Jurong Island, Singapore, Singapore. keatchow@uts.cc.utexas.edu
authors.forename: Keat Theng
authors.initials: KT
authors.lastname: Chow
authors.forename: Kewu
authors.initials: K
authors.lastname: Zhu
authors.forename: Reginald B H
authors.initials: RB
authors.lastname: Tan
authors.forename: Paul W S
authors.initials: PW
authors.lastname: Heng
mesh_terms: D004337:Drug Carriers; D006813:Humidity; D007785:Lactose / Q000737:chemistry*; D009330:Nebulizers and Vaporizers; D055672:Static Electricity
chemical_list: D004337:Drug Carriers; D007785:Lactose