title: Metered dose inhalers: a need for dose counters.
abstract: OBJECTIVE
  This study investigated the ability of patients to assess when a metered dose inhaler (MDI) is empty.
  
  
  METHODS
  A total of 17 patients assessed, by shaking, the number of doses remaining in a salbutamol MDI that had been partially emptied. Another 100 patients were asked to collect all salbutamol MDIs they considered to be empty and would have thrown away. These MDI canisters were weighed and the number of doses that had been used was estimated.
  
  
  RESULTS
  Using the 'shaking method', patients overestimated the amount remaining by around 40 doses. The mean number of doses delivered from an MDI labelled to contain 200 doses before it was discarded was 224 (range, 155-289).
  
  
  CONCLUSIONS
  These findings confirm that patients are unable to determine when an MDI should be discarded, resulting in insufficient drug delivery at the end of the life of an MDI for the majority of patients, and wastage of the drug for others.
authors.affiliation: P3 Research, Wellington, New Zealand.
authors.forename: Shaun
authors.initials: S
authors.lastname: Holt
authors.forename: Avrille
authors.initials: A
authors.lastname: Holt
authors.forename: Mark
authors.initials: M
authors.lastname: Weatherall
authors.forename: Matthew
authors.initials: M
authors.lastname: Masoli
authors.forename: Richard
authors.initials: R
authors.lastname: Beasley
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage*; D001249:Asthma / Q000188:drug therapy; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D004349:Drug Packaging; D004867:Equipment Design; D006801:Humans; D036501:Metered Dose Inhalers / Q000145:classification
chemical_list: D001993:Bronchodilator Agents; D000420:Albuterol