Metered dose inhalers: current and future uses.

Respiratory disease poses an enormous burden on individuals and society. Asthma and chronic obstructive pulmonary disease (COPD), the diseases discussed here, contribute towards a substantial proportion of ill health and cost to the NHS and the economy. Most health professionals consider the inhaled route to be the best method of delivering drugs to the respiratory system. Four types of inhaled delivery system are in use: pressurised metered dose inhalers (pMDIs); dry powder devices; pMDIs and large volume spacers in combination; and nebulisers. In the UK pMDIs are the cheapest type of device on the market and are usually the method of choice for those patients able to use them. International agreement to phase out CFCs has led to the development of alternative propellants for pMDIs. The role of pMDIs is predicted to increase in the future. Demand for pMDIs to treat asthma is likely to increase as the introduction of clinical guidelines extends best practice, and their use to treat patients with COPD is increasing. Novel drugs for the respiratory system, including gene therapy and drugs for non-respiratory disorders, may well employ pMDIs as a delivery system in the future.