Dose response of patients with asthma to inhaled isoproterenol.

In 12 patients with asthma, inhalation of approximately 0.02 mg of isoproternol produced as much increase in peak expiratory flow rate (PEFR) as had a previous inhalation of approximately 0.16 mg of isoproternol at a time when the pre-treatment PEFRwas similar. A group or patients recorded measurements of their PEFR before and after inhalation of varying doses of isoproterenol, ranging from 0 to 0.08 mg. In each patient, only data obtained when control PEFRs were similar were utilized. A maximal effect was noted after inhalation of 0.02 mg of isoproterenol, and no further increase of PEFR was noted after inhalation of larger doses. Inhalation of 0.02 mg or less of isoproterenol produces a maximal effect on PEFR of patients with asthma.