A comparison of the bronchodilator effects of the same amounts of terbutaline aerosol given as a single or in divided doses.

Inhalation of 0.5 mg of terbutaline, given as a single dose or as two immediately consecutive doses of 0.25 or four consecutive doses 0.125 mg, produced the same degree of effective bronchodilation in 12 asthmatic patients at all measured intervals from 30 seconds to four hours after administration. Each treatment regimen produced equivalent improvement in FVC, FEV1, MMEF, MVV, PEFR, V Max 50% VC and V Max 25% VC. The most sensitive indicators were MMEF and V Max 50% VC. No significant side effects were encountered with this dosage and route of administration. The clinical significance of this study is that in patients who are trained in the proper use of metered dose dispensers a single 0.5 mg inhalation may be sufficient to deliver the required dose to obtain an effective and safe therapeutic response.