A double-blind within-patient investigation was performed to determine whether the interposition of an extension tube (10 cm length x 3 -2 cm diameter) between a metered dose inhaler and the mouth alters the bronchodilator efficacy of terbutaline sulphate. On two consecutive study days 14 adult patients with stable reversible airways obstruction inhaled a cumulative dose of 500 jig of terbutaline which was delivered from a metered dose inhaler with or without the extension tube attached and received placebo in a similar manner. The drug was inhaled in doses of 125, 125, and

The dose-response relationships of the anticholinergic bronchodilator drug ipratropium bromide were studied. Cumulative doses totalling 288