ABSTRACT
AIMS: Previous bronchoprovocation studies indicate that nifedipine attenuates airway responsiveness to several stimuli whereas diltiazem has no effect. The aim of this study was to determine whether such studies predict the efficacy of calcium channel blockers as maintenance therapy for persistent asthma. METHODS: Twenty-one otherwise healthy adults with persistent asthma, mean age 25 years, completed treatment with maximum tolerated doses of placebo (P), nifedipine (N), and diltiazem (D) in a double-blind, randomized, three-treatment, three-period, crossover manner, each for 4 weeks. Frequency and severity of asthmatic symptoms were recorded twice daily, as well as peak expiratory flow and frequency of 'prn' use of inhaled terbutaline. Blood pressure, heart rate, P-R interval of the ECG and spirometry were measured biweekly. At the end of each treatment, airway responsiveness to exercise was measured. RESULTS: The mean (s.e. mean)% of days with wheeze was 69plus minus7% during P, 75plus minus6% during N and 72plus minus6% during D (P=0.7). FEV1 was 79plus minus2% of predicted during P, 81plus minus2% during N and 79plus minus2% during D (P=0.6). The decrease in FEV1 after exercise was 32plus minus4% during P, 32plus minus5% during N and 27plus minus4% during D (P=0.5). Heart rate was elevated during N (P=0.0002) whereas P-R interval was prolonged during D (P=0.0001). CONCLUSIONS: Maintenance therapy with calcium channel blockers, at doses that produce cardiovascular effects, do not suppress the signs and symptoms of persistent asthma. Previous bronchoprovocation studies did not predict these results.
