What is the mechanism by which dipyridamole works?

Dipyridamole acts primarily by blocking the uptake of adenosine into cells. By inhibiting the adenosine transporters, dipyridamole increases the levels of adenosine in the vascular environment. Adenosine is a potent vasodilator and has antiplatelet properties, as it can inhibit platelet activation and aggregation. This mechanism is particularly beneficial in preventing thrombus formation and is one of the reasons dipyridamole is used in certain cardiovascular conditions, especially in combination with other antiplatelet medications.

In contrast, the other options do not accurately reflect the primary action of dipyridamole. It does not increase platelet aggregation, does not enhance vitamin K activity—which is more associated with anticoagulants like warfarin—and does not have a direct effect on reducing blood viscosity. The first choice accurately captures the unique pharmacological action of dipyridamole and its role in managing cardiovascular health.