Inhibition of exercise-induced asthma by nifedipine: a dose-response study

1. The effect of three single doses of nifedipine on exercise-induced asthma has been examined in 11 asthmatic subjects. 2. On four separate days patients undertook 6 min of exercise on a treadmill 30 min after taking placebo or nifedipine 10, 20 or 30 mg administered double-blind and in random order. 3. Nifedipine had no significant effect on resting FEV1 measurements. 4. Nifedipine, in doses of 10, 20 and 30 mg, inhibited exercise induced bronchoconstriction, reducing the maximum fall in FEV1 from 30.8 +/- 3.5% after placebo to 21.9 +/- 3.4% (NS), 13 +/- 3.4% (P less than 0.01) and 15 +/- 3.9% (P less than 0.01) respectively. 5. This study has shown that the protective effect of nifedipine against exercise-induced asthma is dose related with the maximum inhibitory effect being observed with a single dose of 20 mg.