Pharmacology · Antiplatelet drugs
Dipyridamole !
An oral antiplatelet and vasodilator that raises adenosine around platelets. It is combined with warfarin after heart valve replacement.
Updated 2026-11-01
Mechanism of action
Dipyridamole blocks the uptake of adenosine into platelets, endothelial cells and red blood cells. The extra adenosine acts on platelet A2 receptors, which raise cAMP through adenylate cyclase and make platelets less responsive to ADP, collagen and platelet-activating factor. It also inhibits phosphodiesterases, especially the one that breaks down cGMP, which adds to the effect of nitric oxide and dilates vessels.
- Dipyridamole blocks adenosine uptake into cells
- Adenosine acts on platelet A2 receptors and raises cAMP
- Phosphodiesterase inhibition adds cGMP: platelets calm, vessels dilate
Pharmacokinetics
- Absorption
- By mouth; peak levels about 75 minutes after a dose.
- Distribution
- Highly bound to plasma proteins.
- Metabolism
- In the liver, conjugated to a glucuronide.
- Elimination
- In the bile.
- Half-life
- Terminal half-life about 10 hours.
Indications
- Together with warfarin, to prevent thromboembolic complications after heart valve replacement.
Adverse effects
Common
- Dizziness
- Abdominal discomfort, diarrhoea, vomiting
- Headache, flushing
- Rash and itching
Contraindications
- Hypersensitivity to dipyridamole
Key interactions
- Adenosine and regadenoson (stress testing)
- Their levels and cardiovascular effects increase; dipyridamole tablets are paused before the test.
- Cholinesterase inhibitors
- Their effect may be opposed, which can worsen myasthenia gravis.
- Warfarin and other anticoagulants or antiplatelets
- Add to bleeding risk.
What is monitored
- Blood pressure, especially at the start
- Chest pain in patients with coronary disease
- Liver enzymes
- INR, as warfarin is given together
Administration and safety
- Oral, as an add-on to warfarin after valve replacement
- Tablets are paused before pharmacological stress testing with adenosine, regadenoson or intravenous dipyridamole
- A fixed combination of aspirin with extended-release dipyridamole also exists; it is a different product
Nursing care
- Check blood pressure and ask about chest pain before and after starting
- Warn that dizziness and headache are common at first and often settle
- Make sure the cardiology or nuclear medicine team knows about it before a stress test
- Watch for bleeding signs together with the INR
Pregnancy and breastfeeding
Animal studies did not show harm, but human data are limited; it is used only if clearly needed.
Test yourself
Think of the answer, then tap the question to see it.
How does dipyridamole inhibit platelets?
It blocks adenosine uptake; the extra adenosine acts on platelet A2 receptors and raises cAMP. It also inhibits phosphodiesterases, especially the cGMP one.
Why is dipyridamole paused before an adenosine or regadenoson stress test?
It increases the levels and cardiovascular effects of adenosine and regadenoson, raising the risk of side effects and reducing test sensitivity.
With which drug is dipyridamole tablet therapy combined after valve replacement?
With warfarin (a coumarin anticoagulant).
Related drugs
← Back to the class: Antiplatelet drugs
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - DIPYRIDAMOLE tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Dipyridamole: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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