Metered-dose inhaler adherence in a clinical trial

Am Rev Respir Dis. 1992 Dec;146(6):1559-64. doi: 10.1164/ajrccm/146.6.1559.


We studied patterns of inhaler usage in a sample of participants from two centers in the Lung Health Study clinical trial. The inhaler, containing either ipratropium bromide or a placebo, was prescribed to be taken as two inhalations three times daily. For 4 months we recorded adherence by both self-report (n = 95) and canister weight change (n = 70). We compared these results with data obtained from a microprocessor monitoring device, the Nebulizer Chronolog (NC), which records the date and time of each inhaler actuation. Seventy-three percent of the participants reported using the inhaler an average of three times daily; however, NC data showed that only 15% of the participants actually used the inhaler an average of 2.5 or more times per day. Canister weight overestimated adherence because only 62% of the NC sets contained the prescribed two actuations. Fourteen percent showed a pattern of actuation of their inhalers more than 100 times in a 3-h interval. We interpret this usage pattern to reflect deliberate emptying of inhalers to appear to be in good compliance with the prescribed program. We conclude that self-report and weighing of inhaler canisters overestimate adherence to the prescribed regimens. Furthermore, a substantial number of monitored inhaler users appear to deliberately dump their medication prior to follow-up visits.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Inhalation
  • Adult
  • Asthma / drug therapy*
  • Female
  • Humans
  • Ipratropium / administration & dosage*
  • Male
  • Middle Aged
  • Nebulizers and Vaporizers
  • Patient Compliance*


  • Ipratropium