Prescription bias and factors associated with improper use of inhalers

Many different inhalers are available for delivering aerosol therapy in respiratory medicine. As a consequence, the prescribing physicians may have some difficulty tailoring the most suitable inhaler to each patient. This multicenter, observational study using a self-administered questionnaire analyzed the characteristics of a large sample of patients (n = 1,305; 55% females; mean age 57.4, with a range of 15-88 years; most suffering from asthma or chronic obstructive pulmonary disease [COPD]) familiar with several different types of inhalers in relation to their most commonly used delivery device. Data on the inhalation technique for 2,057 observations of 1,126 patients using device-specific checklists and factors associated to misuse were also evaluated. Prevalent usage of newer dry powder inhalers (DPIs) was significantly associated with male sex, higher education, better respiratory function, and prescription from a respiratory physician. Patients using DPIs had received less instruction by health caregivers and were more likely to have read the instruction leaflet than users of metered dose inhalers (MDIs). Under these conditions, inhaler misuse was common and similar for both pressurized metered dose inhalers (pMDIs) and DPIs. For both types of inhalers, misuse was significantly and equally associated to increased age, less education, and less instruction by health care personnel. We conclude that many doctors are not familiar with the relevant characteristics of currently available inhalers. The prescription of newer DPIs may be subjected to gender, socio-economic, and instruction bias. The simple change of device from the pMDI to the newer DPIs is not associated with improved inhalation technique.