role of calcium in propranolol-verapamil toxic interaction

Simulaneous administration of propranolol and verapamil is toxic to the experimental animals. The total and differential serum calcium level and serum protein level were estimated in 4 groups of rabbits. One group received propranolol, the second received verapamil, the third received both drugs and the fourth received both drugs plus calcium. Significant increase in the level of serum ionized calcium was observed in the 4 groups. The result indicates that these drugs induce their toxic interacation through the blockade of calcium channels