AEROSOL THERAPY

Aerosol therapy plays a major role in the diagnosis and treatment of v arious lung diseases. The aim of inhalation therapy is to deposit a re producible and adequate dose of a specific drug to the airways, in ord er to achieve a high, local, clinical effect while avoiding serious sy stemic side effects. To achieve this goal, it is therefore important t o have an efficient inhalation device to deliver different medications . However, the currently available therapeutic inhalation devices (neb uliser, pressurised metered-dose inhaler and dry powder inhaler) are n ot very efficient in aerosol delivery and have several disadvantages. Inhalation devices can be assessed by in vitro studies, filter studies and radiolabelled deposition studies. Several radiolabelled depositio n studies have shown that nebulisers and pressurised metered-dose inha lers are not very efficient in aerosol delivery. In children, before 1 997, only 0.5% to 15% of the total nebulised or actuated dose from a n ebuliser or pressurised metered-dose inhaler actually reached the lung s. These numbers were somewhat improved in adults, 30% of the total ne bulised or actuated dose reaching the airways. Aerosol therapy with dr y powder inhalers was the most efficient before 1997, 30% of the total dose being deposited in the lungs of adults and children. In 1997, ne w developments in pressurised metered-dose inhalers much improved thei r efficiency in aerosol delivery. Lung deposition can be increased by up to 60% with use of a non-electrostatic holding chamber and/or a pre ssurised metered-dose inhaler with a hydrofluoroalkane propellant poss essing superior aerosol characteristics. Several studies comparing the clinical efficiency oi: different inhalation devices have shown that the choice of an optimal inhalation device is crucial. In addition to the aerosol characteristics, ventilation parameters and airway morphol ogy have an important bearing on deposition patterns. These parameters may be greatly influenced by the patient's acceptance of a specific i nhalation device and therefore determine the choice of the device used . It is important for the clinical impact to develop more efficient in halation devices, which need to be assessed for use in different age g roups. These devices should be cheap, easy to use, portable, usable wi th all medications and environmentally safe.