DIPYRIDAMOLE
Clinical safety rating: safe
Animal studies have demonstrated safety
Inhibits platelet phosphodiesterase and blocks adenosine reuptake, increasing intracellular cAMP and adenosine levels, thereby inhibiting platelet aggregation; also causes coronary vasodilation.
| Metabolism | Hepatic metabolism via conjugation with glucuronic acid; minor CYP-mediated metabolism. |
| Excretion | Primarily hepatic metabolism (glucuronidation) with enterohepatic recirculation; biliary/fecal excretion accounts for >90% of eliminated drug; renal excretion of unchanged drug is negligible (<5%). |
| Half-life | Terminal elimination half-life is 10–12 hours in healthy adults; prolonged to 20–30 hours in hepatic impairment; clinical effect duration correlates with dosing interval. |
| Protein binding | Approximately 99% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd is 2–3 L/kg, indicating extensive extravascular distribution; high tissue binding (e.g., heart, liver). |
| Bioavailability | Oral bioavailability is 37–66% due to first-pass metabolism; IV bioavailability is 100%. |
| Onset of Action | Oral: 30–60 minutes for inhibition of platelet aggregation; IV: immediate for coronary vasodilation (within 2–5 minutes). |
| Duration of Action | Oral: 6–10 hours (platelet inhibition); IV: 15–30 minutes for vasodilation effect; clinical notes: sustained-release formulations extend duration. |
Dipyridamole immediate-release tablets: 50-100 mg orally 3-4 times daily. Extended-release with aspirin: 200 mg orally twice daily.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (GFR <30 mL/min), use with caution, no specific dose recommendation. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A-B). Contraindicated in severe hepatic impairment (Child-Pugh C) due to risk of hypoglycaemia and hypotension. |
| Pediatric use | Not recommended for use in children due to lack of safety and efficacy data. For rare off-label use: 3-6 mg/kg/day orally in 3 divided doses; maximum 400 mg/day. |
| Geriatric use | No specific dose adjustment; use lowest effective dose due to increased risk of hypotension and falls. Monitor renal function, which may decline with age. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Theophylline may antagonize the antiplatelet effect Can cause angina pectoris and hypotension in patients with coronary artery disease.
| Breastfeeding | Excreted in human milk at low levels; M/P ratio approximately 0.2-0.3. Considered compatible with breastfeeding by AAP; use cautiously in preterm infants or those with thrombocytopenia. |
| Teratogenic Risk | Pregnancy category B. No evidence of teratogenicity in animal studies; limited human data. Risk of fetal hemorrhage due to antiplatelet effect; use only if clearly needed. Second and third trimester: theoretical risk of premature ductus arteriosus closure (no reports to date). |
■ FDA Black Box Warning
No FDA boxed warning.
| Common Effects | Headache |
| Serious Effects |
Hypersensitivity to dipyridamole; use with adenosine or adenosine analogues is contraindicated in stress testing.
| Precautions | May cause hypotension; use with caution in patients with coronary artery disease due to potential coronary steal; can exacerbate angina in unstable patients; discontinue before stress testing if patient is unstable. |
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| Fetal Monitoring |
| Monitor maternal blood pressure, heart rate, and signs of bleeding. In fetus, monitor for growth and well-being if used long-term. No specific monitoring required for short-term use. |
| Fertility Effects | No known adverse effects on fertility in animal studies. No human data available. |