Cumulative dose response relationship of terbutaline delivered by three different inhalers.

In a controlled, open cross-over study 15 asthmatic children received increasing doses of terbutaline (0.125 mg + 0.125 mg + 0.25 mg + 0.5 mg + 0.1 mg) delivered by a pressurized aerosol alone or with a tube spacer or a nebuhaler attached. At no time was there any significant difference in measured FEV1 or percent increase in FEV1 between the three inhalers. However, when eight patients with bronchodilation greater than 50% on all tests days were studied separately, a significantly greater improvement in FEV1 was seen after the first three inhalations of terbutaline when a nebuhaler or a tube spacer was used compared with the response after the pressurized aerosol (P less than 0.05) Bronchodilation measurements did not differ after use of the two spacers. There was no statistically significant difference in side effects between the three inhalers, but there was a trend towards a higher occurrence of side effects when the pressurized aerosol was used alone.