Maximum achievable bronchodilatation in asthma.

We have examined the effects of combinations of three bronchodilator drugs in 37 patients with poorly reversible asthma. In each case FEV1 was less than 90% predicted before administration of the third drug. Nineteen patients took increasing doses of salbutamol by inhalation followed by 160 micrograms ipratropium bromide and intravenous aminophylline, 5.6 mg kg-1. FEV1 increased by at least 200 ml in 18 patients after salbutamol. Subsequently, ipratropium bromide increased FEV1 by 200 ml in three patients while aminophylline did not produce a further 200 ml rise in any patient in this group. Nine patients were given aminophylline followed by ipratropium bromide and salbutamol and nine took ipratropium bromide then aminophylline and salbutamol. Eleven of the 18 patients in these latter two groups had a 200 ml increase in FEV1 using salbutamol as the third drug. Significant increases in pulse rate were only seen after aminophylline or salbutamol administered as the third drug. These results suggest that maximal bronchodilatation in poorly reversible asthma can usually be achieved by increasing doses of beta agonist up to a therapeutic plateau. A further response, if required, may be achieved in some patients with ipratropium bromide.