The clinical effects of a bronchodilator, terbutaline sulphate, were compared after administration in the beginning of the inhalation by means of a standard inhaler and administration by actuating 2 seconds before starting the inhalation by means of an inhaler furnished with a 32 X 100 mm tube. No differences could be seen in the parameters measured-forced vital capacity (FVC), 1-second forced expiratory volume (FEV1), forced mid-expiratory flow (FMF), and oscillatory resistance (Ros). The results indicate that when attaching a tube to the standard inhaler co-ordination of inhalation and actuation of the aerosol is not of vital importance.

Pressurized aerosols of sympathomimetic drugs are widely used in the treatment of bronchial asthma. The efficacy of this form of treatment is diminished in a number of patients by difficulties in coordination between the aerosol actuation and the inhalation. In order to improve the intrapulmonary deposition of terbutaline, an extension tube has been adapted to the regular pressurized aerosol device. In a cross-over randomized study we compared the bronchodilatory effect of increasing doses of terbutaline (250, 500 and 750 μg at 25-min intervals) either delivered by the regular pressurized aerosol device or by the device with the extension tube. The study was performed on 11 adult patients with reversible airways obstruction. Spirometry, body plethysmography and flow volume curves were performed. The onset of the bronchodilatory effect of a single dose of 250 μg terbutaline was more rapid after delivery via the extension tube. The addition of the extension tube caused a significantly higher bronchodilator efficacy of aerosolized terbutaline on the small airways. Our results show that the addition of an extension tube improves the bronchodilator efficacy of terbutaline delivered from a pressurized aerosol.

The bronchodilator effects of cumulative doses of terbutaline 0.125 mg, 0.125 mg and 0.250 mg administered as a pressurized aerosol via a pear shaped spacer were compared with those of terbutaline 1.25 mg, 1.25 mg and 2.50 mg administered as a nebulized solution via a PARI-inhaler Boy. FEV1.0 and flow-volume curves in 13 patients were measured. Initial placebo treatment of both groups resulted in a significant increase in FEV1.0, especially when it was given in nebulized form. The increase after active drug was significant after 15 min, with only minor changes during the rest of the trial. The log-dose/increase in FEV1.0 showed that equipotent doses of pressurized and nebulized terbutaline were in the ratio 1 to 4. Administration by nebulization offered no clear advantage over use of a pressurized aerosol with a pearshaped spacer.

The effect on large and small airways of a pressurized terbutaline aerosol delivered via a 750 ml spacer, or via an ordinary actuator, was investigated in a double-blind study of 15 patients with reversible obstructive airflow disease. There was significant bronchodilatation with both devices as measured by Raw, FEV1.0, PEFR, MEF75, MEF50, and MEF25. Raw showed, a significant difference in favour of the 750 ml spacer. Measurement of Closing Volume (CV) revealed a significant decrease with the spacer, but with the ordinary actuator there was a slight increase in CV; the difference between the devices was significant. The quotient Closing Volume/Vital Capacity (CV/VC%) was significantly decreased with the 750 ml spacer but not with the ordinary actuator. The decrease in volume of isoflow (VisoV) was more pronounced with the spacer but not significantly so. The results suggest that use of a 750 ml spacer may promote more extensive peripheral deposition of the drug in the bronchial tract.