Regional Lung Deposition and Clearance of ^99mTc-Labeled Beclomethasone-DLPC Liposomes in Mild and Severe Asthma

¹ From the Department of Clinical Physiology and Nuclear Medicine, University of Tampere Medical School, Tampere, Finland
² From the Department of Pharmaceutics, University of Kuopio, Kuopio, Finland
³ From the Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston
⁴ From the Tampere University Hospital, and the Department of Medicine, University of Tampere Medical School, Tampere, Finland

Objective: To compare the distribution and clearance of inhaled beclomethasone dipropionate (Bec)-dilauroylphosphatidylcholine (DLPC) liposomes in patients with mild and severe asthma.

Design: A ^99mTc-labeled Bec-DLPC suspension was delivered via a nebulizer (Aerotech II). Immediately after inhalation, anterior and posterior views of the lungs and an anterior view of the oropharynx were measured by a large field gamma camera with the patient in a supine position. To evaluate the mucociliary clearance of the inhaled liposomes, anterior and posterior lung scans were repeated 1, 2, 4, and 24 h after the aerosol delivery.

Patients: Ten patients with mild asthma (FEV₁ >80% of the predicted) and 10 patients with severe asthma (FEV₁ <60% of the predicted) were included in an open, parallel group study.

Results: Clearance is more rapid among patients with severe asthma (p<0.0001). At the 4-h measurement, a mean of 82% (SD, 5.9) of the total pulmonary dose was detected in the lungs of patients with mild asthma while in those with severe asthma the figure was 69% (SD, 10.9). The ratio between central and peripheral deposition was significantly higher for patients with severe asthma than for those having a mild form of the disease; 1.07 (SD, 0.29) and 0.76 (SD, 0.07), respectively (p=0.008).

Conclusions: Inhaled Bec-DLPC liposomes were deposited more centrally in the lower airways of patients with severe asthma than those having a milder form of the disease. The clearance of Bec-DLPC liposomes is strikingly slow in both groups of asthmatic patients. However, due to the more peripheral penetration of inhaled liposomes in patients with mild asthma, the clearance rate in this group was slower than in those with severe asthma.

Key Words: aerosol • asthma • beclomethasone dipropionate (Bec) • corticosteroids • dilauroylphosphatidylcholine (DLPC) • liposome • nebulizer • ^99mtechnetium

Submitted on May 23, 1997
Accepted on November 25, 1997

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