THE EFFECT OF HIGH-DOSES OF INHALED SALBUTAMOL AND IPRATROPIUM BROMIDE IN PATIENTS WITH STABLE CYSTIC-FIBROSIS

The effect of large doses of salbutamol (S) and ipratropium bromide (I B) were tested in a double-blind, randomized, crossover study. Nine pa tients with cystic fibrosis (CF), aged 12.8 +/- 2 years (mean +/- SE), were studied for 8 h on 2 separate days. Pulmonary function tests (PF Ts) included spirometry (FEV1), lung volumes (FRC), and airway resista nce (Raw) measured by body plethysmography. Heart rate (HR) and oxygen saturation (SaO2) were measured before each test. On 1 day patients r eceived S 200 mug, S 400 mug, and IB 80 mug, by inhalation at 45-min i nterval (sequence A). On the other day, the sequence was EB 80 mug, S 200 mug, and S 400 mug (sequence B). The PFTs were obtained at baselin e, 45 min after each inhalation, and 4 and 8 h after baseline measurem ents. Baseline PFTs (mean +/- SE) were not significantly different on the 2 study days (FEV1, 1.48 +/- 0.1 vs 1.42 +/- 0.1 L; FRC, 2.77 +/- 0.6 vs 2.87 +/- 0.6 L; Raw, 4.04 +/- 02 vs 4.00 +/- 0.3 cm H2O/L/s). T he FEV1 and Raw improved from baseline after each inhalation, and at 4 and 8 h during both days (p<0.05). Forty-five minutes after S 200 mug , plus S 400 mug, FEV1, FRC, and Raw were not significantly different compared with the values 45 min after IB 80 mug, plus S 200 mug (1.67 +/- 0.1 vs 1.63 +/- 0.1 L; 2.81 +/- 0.6 vs 2.65 +/- 0.5 L; and 2.98 +/ - 0.2 vs 2.66 +/- 0.1 cm H2O/L/s, respectively). The PFTs were not sig nificantly different after maximal doses of IB (80 mug) compared with S (600 mug). The HR and SaO2 were not significantly different from bas eline throughout the study period. These results indicate that both si ngle and sequential therapy have a similar acute bronchodilator effect provided that large doses are used. We speculate that adrenergic and muscarinic pathways are equally important in airflow obstruction in pa tients with CF.