Targeting drugs to the airways by different inhalation devices: role of deposition characteristics.

Inhalation therapy has greatly improved the treatment of asthma over the last decades. In recent years, inhalation technology has further optimised the local deposition of inhaled antiasthma drugs. Some studies have suggested improved clinical efficacy, and possibly tolerability, of drugs given with modern dry powder inhalers. In particular, the inhalers Turbuhaler((R)) and Diskus((R)) are now commonly used to treat asthma. This review critically evaluates studies comparing the clinical efficacy of antiasthma drugs delivered by available powder inhalers or by pressurised metered-dose inhalers (pMDI), focusing on comparisons of the same drug given by different inhalers. Results differ among studies, in part because of the inclusion of different patient groups (ideally the patients should have reversible airways obstruction) and use of unequal doses or artificial inhalation patterns that may not be optimal for one of the devices. Furthermore, the use of plastic spacers with pMDIs may affect drug delivery.