The relationship between prescribed and delivered doses of inhaled corticosteroids in adult asthmatics.

A model was developed to estimate the impact of adherence and inhalation technique over time on delivered doses of inhaled corticosteroids (ICS) for asthmatics using metered-dose inhalers (MDIs) and dry powder inhalers (DPIs). Factors affecting inhalation technique include ongoing training, inhalation device, spacer use (with MDIs), and natural ability. Model parameters were derived from a literature review or were estimated from clinical experience. Analyses demonstrated that most patients receive a fraction of prescribed ICS doses over time. The model may be used to better understand the impact of increasing ICS dosages and to estimate the likelihood of patients being underdosed.