The rapidity of bronchodilatation. A comparison of isoprenaline, terbutaline and rimiterol.

The onset of action of three sympathomimetic drugs (rimiterol 0.2 mg, terbutaline 0.25 mg and isoprenaline 0.08 mg) administered by metered dose inhaler was compared in 12 asthmatics. In order to evaluate side effects of the drugs, a second dose of the aerosols, 8-10 times higher than the first one, was given after 30 min. The effects were measured in terms of VC, FEV1.0, PEF and heart rate. All the substances caused a significant increase in spirometric values within 1.5 min, the results with isoprenaline being slightly better than those with terbutaline. An increased heart rate was observed after the first dose of isoprenaline whereas no further increase was found after the higher dose. Two patients complained of palpitations, one after isoprenaline and one after rimiterol. No other side effects were recorded. It is concluded that there is a small, clinically insignificant, difference in the onset of action of isoprenaline compared with that of the selective beta2-stimulating aerosol, terbutaline.