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document
Differential inhibition of bronchoconstriction by the calcium channel blockers , verapamil and nifedipine . Recent studies have demonstrated that the calcium channel blocking agents can inhibit experimentally induced bronchoconstriction in asthmatics , but their protective action has been variable . To clarify the influence of stimulus intensity and choice of calcium blocker on these reported differences in outcome , we performed noncumulative thermal stimulus-response curves using isocapnic hyperventilation of cold air in 8 asthmatics . Subjects received pretreatment with orally administered nifedipine ( 20 mg ) , intravenously administered verapamil ( 10 mg bolus followed by a continuous infusion ) , or appropriate placebos in a randomized , double-blind fashion . Verapamil afforded no consistent protection against the thermal challenges , whereas nifedipine significantly blunted the bronchoconstrictor response to stimuli of low ( p less than 0.02 ) and middle ( p less than 0.03 ) intensity . At the highest thermal burden , the effect of nifedipine was inconsistent and not significantly different from that of placebo . These results indicate that the protection from bronchoconstriction afforded by the calcium channel blockers depends on the choice of agent and the intensity of the bronchoconstricting stimulus , and they raise the possibility that the contribution of transmembrane calcium ion influx to the pathogenesis of bronchoconstriction may vary according to stimulus intensity .
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Intervention_Pharmacological
calcium channel blockers
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Intervention_Pharmacological
verapamil
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Intervention_Pharmacological
nifedipine
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Intervention_Physical
calcium channel blocking agents
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Intervention_Pharmacological
nifedipine
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Intervention_Pharmacological
verapamil
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Intervention_Control
placebos
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Intervention_Pharmacological
nifedipine
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Intervention_Control
placebo
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Intervention_Physical
calcium channel blockers
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Outcome_Physical
Differential inhibition of bronchoconstriction
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Outcome_Physical
experimentally induced bronchoconstriction
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Outcome_Physical
bronchoconstrictor response to stimuli of low
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Outcome_Physical
effect of nifedipine
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Outcome_Physical
protection from bronchoconstriction
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Participant_Condition
asthmatics
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Participant_Sample-size
8
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Participant_Condition
asthmatics