💊 Dipyridamole

Dipyridamole is an antiplatelet agent and a vasodilator. It is often used in combination with aspirin.

Dipyridamole inhibits adenosine deaminase and phosphodiesterase, leading to increased intracellular cyclic AMP (cAMP) levels in platelets. This inhibits platelet aggregation and adhesion. It also potentiates the antiplatelet effect of prostacyclin and has vasodilatory properties, particularly in the coronary arteries, by increasing local adenosine concentrations.

Dipyridamole, usually in modified-release formulation combined with aspirin, is indicated for the secondary prevention of ischaemic stroke or transient ischaemic attack (TIA). It is also used as an adjunct to oral anticoagulation for prophylaxis of thromboembolism in patients with prosthetic heart valves.

Contraindications include unstable angina, recent myocardial infarction, and severe aortic stenosis due to its vasodilatory effects. It should be used with caution in patients with severe coronary artery disease, hypotension, or uncontrolled hypertension. Hypersensitivity to dipyridamole is also a contraindication.

Common adverse effects are related to its vasodilatory properties, including headache, dizziness, flushing, and nausea. Gastrointestinal upset, such as diarrhoea, can also occur. Rarely, it can exacerbate angina or cause hypotension. Bleeding risk is increased, especially when combined with other antiplatelet agents.

No routine blood monitoring is typically required for dipyridamole. Patients should be monitored for signs of bleeding, particularly when co-administered with aspirin or other antiplatelet/anticoagulant agents. Blood pressure should be monitored, especially in patients prone to hypotension.

When prescribing, always check for a history of unstable angina, recent MI, or severe aortic stenosis. Enquire about other antiplatelet or anticoagulant medications due to increased bleeding risk. Counsel patients on common side effects such as headache and dizziness, advising them to take it with food to minimise GI upset.

Dipyridamole's mechanism involving adenosine and cAMP is important. Its primary role in UK practice is in secondary stroke prevention as part of a combination product with aspirin. Remember its vasodilatory effects and associated side effects. It is also used for prosthetic heart valve thrombosis prophylaxis.

SBA questions often focus on dipyridamole's dual mechanism (antiplatelet and vasodilator) and its specific role in secondary stroke prevention, usually in combination with aspirin. Its use in prosthetic heart valves is another common theme. Questions might also explore its vasodilatory side effects like headache and dizziness, and contraindications related to coronary artery disease.