DOSE-RELATED PROTECTION AGAINST HISTAMINE-INDUCED BRONCHOCONSTRICTIONBY INHALED SALMETEROL

A double-blind crossover study was carried out in 8 subjects to compar e the effect of inhaled salmeterol 12.5, 50 and 100 mug with inhaled s albutamol 200 mug on resting lung function and on bronchoconstriction in response to inhaled histamine up to 12 hours following each treatme nt. Changes in resting lung function were measured using forced expira tory volume in one second (FEV1) and flow at 70% of vital capacity tak en from partial expiratory flow volume curves (pEFR70). The concentrat ions of histamine which produced a 15% fall in FEV1 (PC15) and a 40% f all in pEFR70 (PC40) were also measured. The peak bronchodilator effec t after salmeterol 50 and 100 mug was similar in magnitude to salbutam ol 200 mug. Salmeterol produced dose-related changes in lung function and protection against histamine-induced bronchoconstriction. The dura tion of the effect of salmeterol (50 and 100 mug) was longer than that for salbutamol (200)mug). Although pEFR70 is a more sensitive measure of lung function there was no greater separation between different do ses of salmeterol than with FEV1. Both salmeterol and salbutamol were well tolerated.