Dipyridamole

Dipyridamole is an antiplatelet and vasodilator agent of the pyrimidopyrimidine class. It inhibits phosphodiesterase 3, the enzyme responsible for breaking down cAMP in platelets, thereby increasing cAMP concentration. Elevated cAMP inhibits the release of calcium ions within platelets, reducing platelet activation and aggregation. Dipyridamole also blocks the reuptake of adenosine by platelets and endothelial cells, increasing extracellular adenosine concentration. This can activate A2 receptors and stimulate platelet adenylate cyclase to produce cAMP, further inhibiting platelet aggregation and promoting vasodilation.