Paradoxic bronchospasm induced by adrenergic aerosols, especially isoproterenol, is a well-known clinical entity. It normally occurs in patients who abuse the use of isoproterenol, but has also been reported in a small group of other patients. This study attempted to identify patients who exhibit paradoxic bronchospasm after administration of aerosolized isoproterenol. Forty-one stable, ambulant asthmatics, whose FEV1.0 was < 70 percent of predicted normal were studied. None of the asthmatics had taken isoproterenol for one year prior to evaluation. Baseline pulmonary function tests (FVC, FEV 1.0, MMEFR), blood pressure and ECG rhythm strips were recorded, and repeated at 15, 30, 60 and 120 min after administration of isoproterenol. Twenty-nine of the asthmatic patients had the expected normal response (ΔFEV1.0, 15 min: + 579; 30 min: + 464; 60 min: + 372; 120 min: + 307 ml; + 44, + 36, + 23 and + 24 percent) (ΔMMEFR, 15 min: + 37; 60 min: + 29; 120 min: + 18L/Min; + 75, + 69, + 47 and + 37 percent). Twelve asthmatic patients (29 percent) had paradoxic bronchospasm (ΔFEV1.0, 15 min: — 38; 30 min: — 60; 60 min: — 175; 120 min: — 27 ml; — 1, —4, — 10 and — 4 percent) (ΔMMEFR — 15 min: — .5; 30 min: — 3; 60 min: — 9; 120 min: — 2L/min; + 4, — 3, — 6 and — 5 percent, P < 0.001).
