Delivery systems: the science.

Different delivery devices may be chosen and the prescribing physician requires information on those suitable for patients of different age, together with the reproducibility of the dose inhaled from the chosen device. A large number of different devices are currently available for inhalation therapy. Although the dose of a drug inhaled by a patient from a device may vary by up to 400%, such information is not usually available to the prescribing doctor. Spacer devices, with facemask attachments for younger children, are now the first choice device for delivery of anti-asthma aerosols to those 5 years of age or less. The dose that spacer devices deliver is governed by a variety of factors, including static charge, face mask design, spacer volume, the particular drug used, and the breathing pattern of the child. Nebulizers are generally prescribed for those not tolerating spacer devices. More recent designs, such as the open-vent nebulizer systems deliver the drug more rapidly to adults. The breath-enhanced open-vent systems have the advantage of delivering significantly more drug to older patients. These systems rely on the relatively large tidal volumes of older patients. As a result of their smaller tidal volumes, young children are unlikely to benefit as greatly from these devices. The open-vent system may result in some young children receiving less drug than from a conventional nebulizer.