Inhaled corticosteroids for adult asthma: impact of formulation and delivery device on relative pharmacokinetics, efficacy and safety.

Metered dose inhalers (MDIs) are the mainstay of inhaled steroid therapy for asthma. With the phasing out of traditional chlorofluorocarbon (CFC) propellants and their replacement with a new generation of CFC-free products, it is becoming clear that formulation and inhaler characteristics can markedly affect the drug delivery. It now seems necessary to compare inhalers not only on the basis of the properties of the steroid molecules but also to take into account the effect of propellants and other inhaler characteristics. The impact of formulation and delivery device on relative pharmacokinetics, therapeutic efficacy and tolerability is illustrated by a new preparation of beclomethasone dipropionate (BDP) in an inhaler containing hydrofluoroalkane (HFA) propellant, called Qvar (3M Health Care, U.K.). This drug preparation delivers the majority of particles (60%) in the fine particle range. This appears to be associated with improved lung deposition, a halving of dose requirements of BDP, but no evidence of clinically relevant adrenal suppression when used in therapeutic doses. Prescribers need to be aware of the impact of formulation on pharmacokinetics of inhaled steroids in order to offer the lowest effective dose and give clear instructions to patients who are changing to a CFC-free product.