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Dry Powder Inhalers: Factors Associated with Device Misuse

Wieshammer S, Dreyhaupt J.

RDD Europe 2009. Volume 1, 2009: 95-104.

Abstract:

Dry powder inhalers (DPIs) were developed to overcome the difficulties of using pressurized metered dose inhalers but are still misused to a substantial degree. Nearly one in three patients (30.9%) used DPIs ineffectively in our study of 224 newly referred outpatients who reported using one or several of four common inhalers. Error rates for the different devices were: Aerolizer 9.1%, Diskus 26.7%, HandiHaler 53.1%, and Turbuhaler 34.9%. The error rate increased with age (20.0% in patients < 60 years versus 41.6% in patients ≥ 60 years, p<0.01), the degree of airway obstruction (25.0% with no obstruction versus 63.6% with severe obstruction, p<0.01), and lack of prior training by a medical professional on how to use the inhaler (23.1% versus 52.6% with training, p<0.01). Approximately one-third of patients were only referred to the package insert for instruction. Based on a risk prediction model, the probability of Turbuhaler misuse is estimated to be only 9.8% for an 18-year-old patient with normal lung function and previous instruction However, the probability of ineffective inhalation is estimated as 83.2% in an 80-year-old with moderate to severe obstruction and no prior instruction. In older patients, the risk of inhaler misuse remains significant despite prior training. Therefore, it is concluded that DPIs are effective devices for the management of younger patients with normal lung function or mild airway disease. The use of currently available DPIs in elderly patients should be re-evaluated. Furthermore, there is a need for user-friendly and ‘active’ DPI designs, which release a reproducible drug dose independently of the patient’s inspiratory force, especially for use by elderly patients.