Can lung deposition data act as a surrogate for the clinical response to inhaled asthma drugs?

Studies involving the direct measurement of clinical response to inhaled as thma drugs, especially inhaled corticosteroids, may be very difficult to co nduct. However, the deposition of drug in the lungs may be considered as a measure of local bioavailability, and may be quantified by radionuclide ima ging techniques, or for some drugs by pharmacokinetic methods. This paper r eviews evidence for considering lung deposition data as a surrogate for the clinical response to inhaled asthma drugs, based mainly upon a series of c ase histories. The appropriate use of lung deposition data in regulatory pa ckages, especially to document the equivalence or comparability of two prod ucts, offers the possibility of significant time saving in the drug develop ment process, and hence a faster drug development programme for inhaled ast hma products.