1. Introduction
Dipyridamole is an antiplatelet agent used to prevent blood clots and reduce the risk of stroke. It inhibits the enzyme phosphodiesterase, increasing cyclic AMP levels and reducing platelet aggregation. Additionally, it has vasodilatory properties, making it useful in specific cardiovascular conditions.
2. Indications
- Approved Indications:
- Secondary prevention of ischaemic stroke and transient ischaemic attack (TIA) (often combined with aspirin).
- Adjunct to anticoagulation for the prevention of thromboembolic complications in prosthetic heart valve patients.
- Off-Label Uses:
- Diagnostic agent in myocardial perfusion imaging (due to its vasodilatory properties).
3. Dosage
- Adults:
- Ischaemic Stroke/TIA Prevention: 200 mg of extended-release dipyridamole combined with 25 mg aspirin twice daily.
- Adjunct in Prosthetic Valves: 300–400 mg daily in divided doses.
- Children:
- Not typically used in paediatric populations.
- Elderly:
- No specific dose adjustment, but monitor for tolerability due to potential side effects such as hypotension or dizziness.
4. Administration
- Take orally, with or without food.
- Swallow extended-release capsules whole; do not crush or chew.
- For myocardial perfusion imaging, administer intravenously under medical supervision.
5. Forms Available
- Extended-release capsules: 200 mg (combined with aspirin 25 mg).
- Immediate-release tablets: 25 mg, 50 mg, 75 mg.
- Injectable solution: 5 mg/mL (used for diagnostic imaging).
6. Side Effects
6.1. Common Side Effects
- Headache.
- Dizziness.
- Nausea.
- Abdominal discomfort.
6.2. Less Common Side Effects
- Hypotension (due to vasodilation).
- Flushing.
6.3. Rare but Serious Side Effects
- Increased bleeding risk (when combined with aspirin or anticoagulants).
- Severe allergic reactions (e.g., rash, difficulty breathing).
7. Warnings
- Bleeding Risk: Use cautiously in patients at high risk of bleeding, especially when combined with other antiplatelet or anticoagulant medications.
- Hypotension: Due to vasodilatory effects, it may cause dizziness or fainting, particularly in patients with low blood pressure.
8. Precautions
- Use cautiously in patients with severe coronary artery disease due to the risk of “coronary steal syndrome” (redistribution of blood flow away from stenosed arteries).
- Monitor for headache or other signs of intolerance, particularly during initial therapy.
9. Interactions
- Drug-Drug Interactions:
- Aspirin or anticoagulants: Increased risk of bleeding.
- Antihypertensives: May enhance hypotensive effects.
- Adenosine: Dipyridamole increases adenosine levels, prolonging its effects.
- Drug-Food Interactions:
- No specific food interactions.
10. Monitoring Parameters
- Clinical efficacy (e.g., reduction in ischaemic events such as stroke or TIA).
- Monitor for signs of bleeding, particularly in patients on combination therapy with aspirin or anticoagulants.
- Blood pressure (especially in patients prone to hypotension).
11. Use in Children
- Limited data on use in paediatric populations; generally avoided unless specifically indicated.
12. Use in Pregnancy
- Category B: Generally considered safe in pregnancy, but should only be used if benefits outweigh potential risks.
13. Use in Elderly
- Safe for use in elderly patients, but monitor closely for side effects like hypotension or headache.
14. Use in Kidney Disease
- No specific dose adjustment is required, but caution is advised in severe renal impairment due to limited data.
15. Use in Liver Disease
- Use with caution in patients with hepatic impairment due to possible altered metabolism.
16. Patient Counselling Points
- Take dipyridamole exactly as prescribed, and do not miss doses to ensure continuous prevention of clots.
- Report unusual bleeding, bruising, or persistent headaches to your doctor immediately.
- For extended-release capsules, swallow whole with water. Do not crush or chew.
- Stand up slowly to prevent dizziness due to low blood pressure.
- Inform your healthcare provider if you’re undergoing surgery or dental procedures, as the medication may need to be stopped temporarily.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Aggrenox (ER Aspirin + Dipyridamole) | Boehringer Ingelheim | $50–100 (30 capsules) |
Persantine | Boehringer Ingelheim | $20–40 (30 tablets, 75 mg) |
Generic Dipyridamole | Various | $10–25 (30 tablets, 75 mg) |
18. FAQs (15 Questions)
- What is dipyridamole used for?
It is used to prevent blood clots, reduce the risk of stroke, and support anticoagulation in prosthetic heart valve patients. - How does dipyridamole work?
It inhibits platelet aggregation and has vasodilatory properties by increasing cyclic AMP levels. - Can dipyridamole be used alone for stroke prevention?
It is often combined with aspirin for greater efficacy in preventing strokes and TIAs. - What are the common side effects of dipyridamole?
Headache, dizziness, nausea, and abdominal discomfort are common side effects. - How should dipyridamole be taken?
Take it as prescribed, with or without food. Swallow extended-release capsules whole. - Can dipyridamole cause low blood pressure?
Yes, it may cause hypotension due to its vasodilatory effects. - Is dipyridamole safe during pregnancy?
It is generally considered safe (Category B), but consult your doctor before use. - What should I do if I miss a dose of dipyridamole?
Take it as soon as you remember, but skip it if it’s close to your next dose. Do not double up. - Can dipyridamole interact with other medications?
Yes, it can interact with aspirin, anticoagulants, adenosine, and antihypertensives. - Can dipyridamole be used in children?
It is not commonly used in children due to limited safety data. - How long does it take for dipyridamole to work?
Its effects begin within a few hours, but long-term use is required for stroke prevention. - Does dipyridamole increase bleeding risk?
Yes, particularly when combined with aspirin or anticoagulants. - Can I drink alcohol while taking dipyridamole?
Alcohol may increase the risk of dizziness or hypotension, so it should be limited or avoided. - How should dipyridamole be stored?
Store at room temperature, away from light and moisture. - Can dipyridamole be stopped abruptly?
Do not stop taking dipyridamole without consulting your doctor, as it may increase the risk of blood clots.