A comparative study of inhaled atropine sulfate and isoproterenol hydrochloride in cystic fibrosis.

To investigate the contribution of vagal tone to the obstructive airway disease 
in cystic fibrosis, we evaluated the pulmonary function response to administration 
of 0.1 mg of atropine sulfate per kg of body weight, 
0.05 mg of isoproterenol hydrochloride per kg of body weight, or 
isotonic saline (control solution) administered by nebulization on 3 different days 
to each of 10 patients with cystic fibrosis in a single 
blind study. The doses of atropine sulfate and isoproterenol hydrochloride were 
based on published dose-response characteristics of the drugs. Each day, thoracic 
gas volume and airway resistance were measured in a volume displacement 
body plethysmograph, and maximal expiratory flow-volume curves were performed before and 
at 15, 30, and 60 min after the inhalation. After inhalation 
of saline, group mean values for all pulmonary functions indicated greater 
airway obstruction at 15, 30, and 60 min when compared to 
pretreatment values. After inhalation of isoproterenol and atropine, significant improvement (P 
< 0.05) was noted in maximal expiratory flows at 60 per 
cent of total lung capacity, specific airway conductance, thoracic gas volume, 
and residual volume. Inhalation of atropine also significantly improved maximal expiratory 
flow at 25 per cent of vital capacity. Isoproterenol increased the 
mean flows by 8 to 46 per cent above baseline, and 
decreased thoracic gas volume and residual volume by 11 to 16 
per cent with the maximal response at 15 or 30 min. 
Atropine increased mean flows by 15 to 77 per cent and 
decreased thoracic gas volume and residual volume by 16 to 25 
per cent with the maximal effect at 30 to 60 min. 
The mean response to atropine, expressed as a percentage of baseline, 
was always greater than or equal to that for isoproterenol. We 
conclude that vagal tone, which may reflect increased irritant receptor activity, 
contributes to the obstructive pulmonary function in cystic fibrosis. Inhalation of 
atropine sulfate will decrease the pulmonary function abnormality, but side effects 
prohibit its clinical usefulness. 