Acute bronchial and cardiovascular effects of oral pirbuterol and metaproterenol.

The acute pulmonary and cardiovascular effects of pirbuterol dihydrochloride 10 mg and 15 mg, a new orally active beta 2-selective sympathomimetic agent, were compared with those of placebo and metaproterenol 20 mg over a period of seven hours in 24 stable asthmatics. Pirbuterol 15 mg and metaproterenol 20 mg had a comparable onset of action (30 min) and magnitude of peak bronchodilator effect (29 +/- 5 mean % increase in FEV1) but the bronchodilatation following pirbuterol was longer lasting (seven hours) than that following metaproterenol (three hours). Pirbuterol 15 mg also caused a greater magnitude and duration of bronchodilatation than pirbuterol 10 mg. No effect on heart rate or PEP/LVET ratio was noted with either drug. Side effects reported following each of the active agents were comparable in frequency and were almost always mild. These findings indicate that pirbuterol is an effective bronchodilator with a relatively long duration of action, definite beta 2-adrenergic specificity and insignificant toxicity when administered in a single dose.