Relative lung bioavailability of generic sodium cromoglycate inhalers used with and without a spacer device

The relative lung bioavailability of sodium cromoglycate following inhalation has been evaluated using urinary drug excretion in nine healthly volunteers. Each inhaled four 5 mg sodium cromoglycate doses from a generic metered dose inhaler (MDI) and when it was attached to large volume spacer (MDI + VOL). A breath-actuated MDI was also evaluated either used on its own (EB) or attached to a small volume spacer tube (EBO). The mean (SD) urinary excretion of sodium cromoglycate in the first 30 min post-inhalation was 34.1 (20.2), 211.7 (123.5), 29.3 (19.5) and 52.8 (36.0) microg following MDI, MDI+VOL, EB and EBO, respectively. The cumulative mean (SD) urinary excretion of sodium cromoglycate over the 24 h post-inhalation was 364.7 (266.2), 1227.1 (459.0), 280.2 (155.4) and 429.5 (176.7) microg. A metered dose inhaler attached to a large volume spacer delivers more sodium cromoglycate to the lungs than any other inhalation method.