The size of the problem of managing asthma.

Asthma is now the commonest chronic disease in industrialised countries and its prevalence is rising throughout the world. However, despite the availability of very effective treatments many patients with asthma have poorly controlled symptoms and frequent exacerbations, some of which require hospital admission. Important factors contributing to poor asthma control are failure to recognise asthma as a diagnosis, non-implementation of asthma management guidelines and patient non-compliance with therapy. The guidelines themselves have many inherent limitations. Chief among these is that the evidence upon which they are based may be misleading. The evidence used to support recommendations in guidelines is derived from double-blind, placebo-controlled studies in very carefully selected patients who are usually compliant with therapy and instructed in the use of inhalers. In the 'real world' things are very different and patients frequently fail to understand how to use their therapy and are often non-compliant. Reasons for non-compliance are complex and include complicated drug and dosing regimens and inability to use inhaler devices correctly; particularly pressurised metered dose inhalers (pMDIs) due to difficulty co-ordinating device activation and inhalation. Dry powder inhalers (DPIs) preclude the need to co-ordinate inspiration with activation, are easy and convenient to use and are environmentally friendly. There is no doubt that the type of inhaler is just as important as the class of drug in the long-term management of asthma. Improvements in inhaled drug delivery will continue to be important in improving asthma management.