Pharmacokinetics of flunisolide administered via metered dose inhaler with and without a spacer device and following oral administration.

BACKGROUND: After inhalation of a glucocorticoid from a meter dose inhaler (MDI), a certain portion of the delivered dose is deposited in the lungs, and the remainder is deposited in the oropharynx. OBJECTIVE: To examine the absolute bioavailability of flunisolide given orally via metered dose inhaler, and metered dose inhaler with a commercially available spacer device as well as to determine the fraction of drug deposited in the lungs following inhalation. METHODS: Twenty-four healthy volunteers were enrolled in the study; twenty-two completed the study. The IRB approved the study protocol, and informed consent was obtained. Volunteers received four treatments: treatment A (MDI), 1.0 mg inhaled flunisolide; treatment B (MDI-S), 1.0 mg inhaled flunisolide with a spacer device; treatment C, 1.0 mg of orally administered flunisolide with 240 mL of water; and treatment D, 1.0 mg intravenous flunisolide by IV push in the antecubital vein over 60 seconds. Plasma and urine flunisolide were quantified by HPLC/mass spectrometry/mass spectrometry. RESULTS: Flunisolide is a corticosteroid with low oral bioavailability (6.7%), which was found to be lower than previously reported. Similar AUCs were observed between the MDI and MDI-S groups, but by using mass balance equations, it appears that more flunisolide was delivered to the lungs in the MDI-S group (410 microg versus 280 microg). Oropharyngeal deposition was an important difference between the two inhaler groups. Approximately an 11-fold reduction in the oropharyngeal deposition of flunisolide through use of the spacer device was observed. CONCLUSIONS: Use of a spacer device improved pulmonary delivery of flunisolide by almost 50% and significantly decreased the oropharyngeal exposure to drug.