Antispasmogenic and spasmolytic effects of verapamil and salbutamol, alone and in combination, on histamine-induced guinea pig tracheal contraction in vitro.

The antispasmogenic and spasmolytic effects of the calcium entry blocker verapamil were examined on histamine-induced guinea pig tracheal contraction in vitro in comparison with the beta 2-adrenergic agonist salbutamol. The effects of verapamil were found to be about 1000 times weaker than those of salbutamol. The antispasmogenic IC50 for verapamil was 1.99 x 10(-4) M compared to 7.94 x 10(-8) M for salbutamol. The spasmolytic EC50 for verapamil was 3.37 x 10(-5) M and for salbutamol was 1.95 x 10(-8) M. The combined application of verapamil and salbutamol resulted in additive antispasmogenic and spasmolytic effects.