Dose response of inhaled gallopamil (D600), a calcium channel blocker, in attenuating airway reactivity to methacholine and exercise. To determine if there is a dose-response relationship for calcium channel blockers in preventing experimentally induced bronchoconstriction, we evaluated the effects of inhaled gallopamil (D600), a potent methoxy derivative of verapamil, on airway reactivity to methacholine and exercise in volunteers with mild asthma. Methacholine challenges were completed by 11 subjects 2 hours before and 20 minutes after placebo, and 1, 2, 5, 10, and 20 mg of inhaled gallopamil administered in a single-blind, randomized manner on different days. Gallopamil did not significantly alter FVC, FEV1, or forced expiratory flow rate between 25% and 75% of FVC, but increased the dose