Subsensitivity of beta-adrenoceptor responses in asthmatic patients taking regular low dose inhaled salbutamol

Summary Tremor (Tr), chronotropic (HR) and metabolic (K, Glu) responses to cumulative doses of inhaled salbutamol (100 g to 4000 g) were compared in an age and sex matched group of 7 normal (N) and asthmatic (A) subjects.Comparison of regression lines between groups showed differences in HR and K. This was also reflected in attenuation of maximum responses in group A, for HR and K.These results show subsensitivity of chronotropic and hypokalaemic responses in patients with asthma, which may reflect tachyphylaxis from the effects of long term inhaled salbutamol therapy.