Pharmacokinetic/pharmacodynamic evaluation of inhalation drugs: application to targeted pulmonary delivery systems

Inhaled therapy with either glucocorticoids and/or beta(2)-adrenergic drugs remains the mainstay of asthma treatment. In the last few years, a number of new products have been introduced into the market with the goal of improving efficacy and safety. This review article summarises the pharmacokinetic and pharmacodynamic properties of inhaled drugs for topical delivery necessary to achieve this goal. Pharmacokinetic properties include a high pulmonary deposition, low oral bioavailability, optimised pulmonary residence time and a very high systemic clearance. Optimisation of pharmacodynamic properties, such as receptor selectivity, may also yield drugs with improved pulmonary selectivity. As existing drugs also provide high efficacy and safety profiles, future developments will represent only slight improvements and quantum leap improvements are unlikely to occur.