The effect of nifedipine (20 mg sublingually) on the bronchial response to cold air was studied in eight asthmatic patients and eight normal subjects. Eucapnic hyperventilation with dry subfreezing air was performed for three minutes by each subject, with a minute volume of 30 X FEV1 for normal subjects and half that for the asthmatics. In the normal subjects there was no difference in the falls in the one-second forced expiratory volume (FEV1) and specific airways conductance (sGaw) produced by cold air inhalation on the days when they were pretreated with placebo and with nifedipine. In asthmatic patients, however, significant protection with nifedipine was demonstrated. The maximum recorded fall in FEV1 was reduced from 13% +/- 2% (SE) to 4% +/- 2% (p less than 0.005) and the maximum fall in sGaw from 35% +/- 5% to 17% +/- 4% (p less than 0.002). The possible causes of this difference are discussed. It is suggested that these results present further evidence for a different mechanism of response to cold air in asthmatic and normal subjects.
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