Dipyridamole is a drug that inhibits platelet aggregation.

• It inhibits the enzyme adenosine deaminase which normally breaks down adenosine. This inhibition leads to increased levels of adenosine. Adenosine activates the enzyme adenylate cyclase which leads to increased cyclic AMP (cAMP) synthesis.
• Dipyridamole also inhibits the enzyme phosphodiesterase which normally breaks down cAMP.

Both of these mechanisms lead to increased levels of cAMP within platelets. cAMP impairs platelet aggregation.

Modified release dipyridamole is used in conjunction with aspirin in the secondary prevention of stroke and transient ischemic attack.