Dry powder inhalers are bioequivalent to metered-dose inhalers. A study using a new urinary albuterol (salbutamol) assay technique.

Metered-dose inhalers (MDIs) are extensively used to deliver drugs to the lungs but are driven by chlorofluorocarbon (CFC) propellants. The worldwide phasing out of CFCs within the next 5 to 10 years presents difficulties to the pharmaceutical industry. The mean +/- SD relative lung bioavailability of albuterol to the lung following inhalation of 400 micrograms of albuterol from an MDI, the Rotahaler and Diskhaler in 10 well-trained volunteers, was 2.83 (0.78), 1.72 (0.99), and 2.64 (1.23)%, respectively, expressed as a percentage of the nominal dose. The delivery of albuterol to the lungs from the MDI and Diskhaler was similar. In nine asthmatic subjects, the relative lung bioavailability of albuterol following inhalation with the MDI and Diskhaler was 1.19 (0.79) and 2.38 (1.46)%, respectively, expressed as a percentage of the nominal dose. There was no difference in reversibility 30 min after administration of the dose by the two methods. Similar lung deposition from the Diskhaler in volunteers probably is due to efficient MDI technique, which was absent in the asthmatic subjects. The Diskhaler does not rely on coordination during inhalation and therefore is easier to use.