Lung deposition patterns of directly labelled salbutamol in normal subjects and in patients with reversible airflow obstruction.
BACKGROUND--Earlier studies of aerosol deposition in the lungs have relied on indirect labelling of Teflon spheres of a similar size distribution to the drug in question and have assumed similar aerodynamic properties. Using a modification of a new technique for directly labelling salbutamol, the deposition of salbutamol within the lungs of normal subjects and patients with asthma has been studied with the use of a metered dose inhaler (MDI) alone, an MDI with a spacer device, and a dry powder inhaler (DPI). METHOD--Salbutamol was directly labelled with technetium-99m and placed in an MDI or DPI. Ten normal subjects and 19 patients with asthma inhaled 200 micrograms of salbutamol by means of the MDI alone, the MDI with a spacer device attached, and by DPI on separate days. Deposition was assessed by a dual headed gamma camera after inhalation of the drug. RESULTS--The total mean (SD) percentage deposition of the drug in the normal subjects was 21.6% (8.9%) with the MDI alone, 20.9% (7.8%) with the MDI with spacer, and 12.4% (3.5%) with the DPI. For the patients, the mean percentage deposition was 18.2% (7.8%) with the MDI alone, 19.0% (8.9%) with the MDI and spacer, and 11.4% (5.0%) with the DPI. Bronchodilatation achieved by the patients was similar with all three techniques. Mean peripheral lung deposition was significantly greater with a spacer device than when the MDI was used alone in both normal subjects (49.4% (6.1%) v 44.1% (9.9%)) and patients (38.6% (11.1%) v 30.4% (9.4%)). CONCLUSIONS--The deposition of directly labelled salbutamol from an MDI is greater than previously estimated by indirect labelling techniques. The deposition of labelled salbutamol from a DPI, however, is little different from that measured by indirect techniques.
Melchor
R
R
Department of Thoracic Medicine, University College Hospital, London.
Biddiscombe
M F
MF
Mak
V H
VH
Short
M D
MD
Spiro
S G
SG
D000328:Adult; D000368:Aged; D000420:Albuterol / Q000008:administration & dosage*; D001249:Asthma / Q000188:drug therapy*; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D008168:Lung / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D013667:Technetium
D013667:Technetium; D000420:Albuterol