Effects of diltiazem and verapamil on ADP-induced rabbit platelet shape change and aggregation.

Abstract 1. 1. The effects of diltiazem and verapamil (two structurally different calcium channel blockers) were examined on the rabbit platelets shape change and aggregation induced by adenosine-5′-diphosphate (ADP). 2. 2. ADP was a much more potent stimulator on inducing platelet shape change (ED 50 = 1 × 10 −7 ) than platelet aggregation (ED 50 = 1.78 × 10 −6 ). 3. 3. Both drugs similarly inhibited ADP-induced platelet shape change and aggregation at concentrations more than 300 μM. 4. 4. There were no significant differences in inhibitory effects of either diltiazem or verapamil on ADP-induced platelet shape change and aggregation. 5. 5. The inhibitory effects of diltiazem and verapamil on ADP-induced platelet shape change and aggregation at high concentrations may be due to their non specific properties.