The effects of nifedipine and verapamil on antigen-induced bronchoconstriction in dogs

The effects of calcium channel blockers, nifedipine and verapamil (i.v. and aerosol), were investigated in beagle dogs natively allergic to Ascaris suum antigen. Control exposures to an aerosol of Ascaris antigen provoked significant bronchopulmonary changes, i.e., increases in pulmonary resistance (R L) and decreases in dynamic lung compliance (C DYN). Pretreatment with either nifedipine or verapamil (200 μg/kg, i.v.) provided significant inhibition in the R L responses to Ascaris antigen (P < 0.015) while neither agent significantly affected C DYN changes. When administered as an aerosol, verapamil (1.0%; 10 breaths) significantly inhibited both the R L and C DYN responses to Ascaris antigen ( P < 0.05), whereas a similar concentration of nifedipine was without effect. Resting basal levels of R L and C DYN were unaffected by either the i.v. route or by aerosols of either nifedipine or verapamil. These results suggest that calcium channel blockers may have beneficial effects against allergen-provoked bronchoconstriction; however, differences appear to exist in the choice of agent, route of administration and site of action.