The relevance of site of airway inflammation in asthma and targeted aerosol delivery

Asthma is an inflammatory disorder characterised by mast cell, T-cell, epit helial cell and eosinophil activation within the airways as well as noticea ble recruitment of eosinophils into the airway mucosa. These changes are ev ident in both small and large airways, although most of the in vivo evidenc e has been obtained from the large airways. It has now been established tha t nocturnal asthma exacerbations are associated with alveolar eosinophilic inflammation and structural airway changes seen in both the small and large airways. Consequently this has led to a change in emphasis for the targeti ng of therapeutic intervention to both the large and the peripheral airways . This shift has been emphasised by reports of exaggerated loss of lung fun ction with time in asthma and airway hyperinflation in this disease, both o f which can be attributed to persistent small airway abnormalities. Setter understanding of particle dynamics during aerosol actuation and inhalation identifies deficiencies of the current chlorofluorocarbon inhaler devices i n dispersing drug of the appropriate particle size to reach peripheral airw ays. The advent of hydrofluoroalkane (HFA) inhaler devices, particularly HF A-beclomethasone dipropionate (which is in solution rather than suspension) , has increased the fraction of particles in the 1-3 mu m range, thus enabl ing peripheral airway deposition. Within the short term, the increased lowe r airway delivery with aerosols allows symptom control and improved lung fu nction to occur at a lower inhalation dose. The long-term impact on asthma management is awaited.