Lung deposition of budesonide from a pressurized metered-dose inhaler attached to a spacer

The absolute systemic availability and pulmonary deposition of budesonide inhaled from a pressurized metered-dose inhaler (pMDI) attached to a Nebuhaler spacer was determined in 15 healthy subjects. The study was of an open cross-over design. Each subject randomly received three single doses of budesonide on separate days: 0.5 mg given intravenously and 1.0 mg (0.2 mg x 5) by inhalation from a pMDI with a Nebuhaler, with or without concomitant oral charcoal intake to prevent gastrointestinal absorption. Charcoal intake did not significantly affect the systemic availability or deposition of budesonide. The systemic availability was 36+/-14% (metered dose, mean+/-SD) with charcoal and 35+/-10% without. The pulmonary deposition was 36+/-14% with charcoal and 34+/-11% without. Erroneous administration, in which the canister was shaken only before the first of the five actuations, halved the systemic availability. In conclusion, the pulmonary deposition of budesonide from a pressurized metered-dose inhaler with Nebuhaler is high under optimum conditions. The small discrepancy between the systemic availability and pulmonary deposition indicates that the contribution from deposition in the oropharynx and subsequent absorption from the gastrointestinal tract is negligible. The marked reduction in the systemic availability of budesonide with the unshaken canisters confirms that the performance of a pressurized metered-dose inhaler is very much dependent on proper handling.