COMPARATIVE-STUDY OF INHALED ATROPINE SULFATE AND ISOPROTERENOL HYDROCHLORIDE IN CYSTIC-FIBROSIS

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Abstract
To investigate the contribution of vagal tone to the obstructive airway disease in cystic fibrosis, the pulmonary function response to administration of 0.1 mg of atropine sulfate/kg of body wt, 0.05 mg of isoproterenol hydrochloride/kg of body wt, or isotonic saline (control solution) administered by nebulization on 3 different days to each of 10 patients with cystic fibrosis was evaluated 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 flow at 60% of total lung capacity, specific airway conductance, thoracic gas volume, and residual volume. Inhalation of atropine also significantly improved maximal expiratory flow at 25% of vital capacity. Isoproterenol increased the mean flows by 8-46% above baseline, and decreased thoracic gas volume and residual volume 11-16% with the maximal response at 15 or 30 min. Attropine increased mean flows 15-77% and decreased thoracic gas volume and residual volume 16-25% with the maximal effect 30-60 min. The mean respnose to atropine, expressed as % of baseline, was always .gtoreq. that for isoproterenol. Vagal tone, which may reflect increased irritant receptor activity may contribute 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.