Cardiovascular effects of intramuscular or inhaled terbutaline in asthmatics

8 stable asthmatics were at random given placebo, 0.125 mg, 0.25 mg, 0.5 mg and 1 mg terbutaline intramuscularly or 2.5 mg as inhalation. Systolic time intervals, echocardiographic parameters and peak expiratory flow (PEF) were measured. Maximal circulatory and respiratory response was obtained after 0.5 mg and 0.25 mg, respectively. The circulatory effect of 2.5 mg inhaled terbutaline equalled 0.125 mg given intramuscularly, while this dosage elicited maximal bronchodilator effect. Thus, nebulized terbutaline has only a minimal circulatory effect, and even the intramuscular dosages were without dramatic circulatory side effects.