Prevention of fog-induced bronchospasm by Duovent and its components (fenoterol, ipratropium bromide) in asthmatics.

16 hyperreactive asthmatics were challenged with an ultrasonic mist of H2O at the same time of day on 4 usually consecutive days 2 h after premedication with placebo, fenoterol (200 micrograms), ipratropium bromide (80 micrograms) and Duovent (fenoterol 200 micrograms + ipratropium bromide 80 micrograms), given in random order and double-blind conditions. The challenge test consisted of 3 exposures of 30, 60 and 120 s with 4-min intervals. Specific airway resistance (sRaw) was measured under basal conditions and 1, 2 and 3 min after each exposure. FEV1 was measured under basal conditions and immediately after the last sRaw measurement. Fenoterol afforded a good protection; ipratropium bromide alone was ineffective but enhanced the protective effect of fenoterol when the two drugs were given in combination (Duovent). A similar effect was also observed after a second challenge performed 1 h (9 patients) or 3 h (6 patients) after the first one, which was performed 2 h after premedication.