The fate of inhaled drugs: the pharmacokinetics and pharmacodynamics of drugs administered by aerosol.

Prior to a drug achieving its effects (ie, pharmacodynamics), there are numerous events within the body that determine its ultimate fate. The effects of the "body on the drug" has been referred to as pharmacokinetics-how the favorable lung-to-systemic effects predicted from this exercise translate into practice. Inhaled drugs have enjoyed the major feature of having "local" effects on the target organ of the lung. Broadly, lower doses can be used and adverse effects are often less than with oral or parenteral administration. Nevertheless, key features of respiratory drugs and their administration can impact their fate and ultimate utility. This review has provided some relevant examples of basic pharmacokinetics principles as related to inhaled products, with emphasis on those factors that help to partition lung-to-systemic effects.