Dipyridamole

Dipyridamole is an Antiplatelet / vasodilator belonging to Nucleoside transport inhibitor / phosphodiesterase-3 (PDE3) inhibitor.

Dipyridamole is indicated for the prevention of postoperative thromboembolic events. It is also used as thallium myocardial perfusion imaging for the evaluation of coronary artery disease.

Dipyridamole is incompletely absorbed from the GI tract. The time to peak plasma concentrations is approximately 75 minutes. Dipyridamole is widely distributed in body tissues. It crosses the placenta in small amounts and enters breast milk. The Volume of distribution of dipyridamole is about 2-3 L/kg. The Plasma protein binding is approximately 91-99%, mainly to α₁-acid glycoprotein. Dipyridamole is metabolized in the liver to glucuronide conjugate; may undergo enterohepatic recirculation. The terminal elimination half-life of Dipyridamole is about 10-12 hours. It is excreted in feces (as glucuronide conjugates and unchanged drugs).

Dipyridamole shows common side effects like Dizziness, stomach pain, headache, rash, diarrhea, vomiting, flushing (feeling of warmth), itching.

Dipyridamole is available in the form of Oral Tablet and Injectable solution.

Dipyridamole is available in India, US, Australia, China, Germany, Russia, France, and Italy.

Dipyridamole belonging to the Nucleoside transport inhibitor / phosphodiesterase-3 (PDE3) inhibitor acts as an antiplatelet / vasodilator.

Dipyridamole likely inhibits both adenosine deaminase and phosphodiesterase, preventing the degradation of cAMP, an inhibitor of platelet function. This elevation in cAMP blocks the release of arachidonic acid from membrane phospholipids and reduces thromboxane A2 activity. Dipyridamole also directly stimulates the release of prostacyclin, which induces adenylate cyclase activity, thereby raising the intraplatelet concentration of cAMP and further inhibiting platelet aggregation.

The time taken for Dipyridamole to show its effect is 24 minutes.

The Duration of action of Dipyridamole is approximately 3 hours.

The Tmax was found within 2-2.5 hours following the administration.

Dipyridamole is available in the form of Oral Tablets and Injectable solutions.

Dipyridamole tablet is taken orally usually 4 times a day and in IV solution; diluted solution Infused over 4 minutes.

Dipyridamole is indicated for the prevention of postoperative thromboembolic events. It is also used as thallium myocardial perfusion imaging for evaluation of coronary artery disease.

Dipyridamole is an Antiplatelet / vasodilator belonging to Nucleoside transport inhibitor / phosphodiesterase-3 (PDE3) inhibitor.

Dipyridamole inhibits the activity of adenosine deaminase and phosphodiesterase, thus inhibiting platelet aggregation, and producing vasodilation. Additionally, it stimulates the release of prostacyclin or PGD₂ and causes coronary vasodilation.

Dipyridamole is approved for use in the following clinical indications

• Thromboembolic Stroke Prophylaxis

Adult:

Dipyridamole tablets are indicated as an adjunct to coumarin anticoagulants in the prevention of postoperative thromboembolic complications of cardiac valve replacement.

Pediatric:

Dipyridamole tablets are indicated as an Adjunct to warfarin prophylaxis of thromboembolism after cardiac valve replacement.

• Dipyridamole is also used for pediatrics as antiplatelet (general dosing and mechanical prosthetic heart valves) and for the treatment of proteinuria.

Although not approved, there have been certain off-label indications. These include

• Thallium Myocardial Perfusion Imaging

Alternative to exercise in thallium myocardial perfusion imaging for evaluation of coronary artery disease (CAD) in patients who cannot exercise adequately.

• Thromboembolic Stroke Prophylaxis

Adult Oral Dose: 75 to 100 mg orally 4 times a day.

Pediatric Oral Dose: 12 years or older: 75 to 100 mg orally 4 times a day.

• Antiplatelet

Infants, Children, and Adolescents

General Oral dose: 2 to 6 mg/kg/day in 3 divided doses; usual adult maximum dose: 100 mg/dose.

Oral dosing for Mechanical prosthetic heart valves: 2 to 5 mg/kg/day in divided doses, most commonly in 3 divided doses.

• Proteinuria, adjunct therapy:

Children ≥7 years and Adolescents Oral Dose

Initial: 3 to 5 mg/kg/day in 3 divided doses; may titrate to reported range: 5 to 6 mg/kg/day in 3 divided doses; maximum daily dose: 400 mg/day; in trials dipyridamole was given as part of a 3 or 4 drug combination therapy (eg. immunosuppressant agents, antihypertensive agents, and an anticoagulant).

• Thallium Myocardial Perfusion Imaging

Adult IV Dose: 0.142 mg/kg/min infused over 4 min (0.567 mg/kg total); not to exceed 60 mg.

Pediatric IV Dose: Children ≥6 years and Adolescents: 0.56 mg/kg administered over 4 minutes; maximum adult dose: 70 mg/dose.

Dipyridamole is available in the form of Oral Tablet and Injectable solution.

Avoid herbs and supplements with anticoagulant/antiplatelet activity (eg. garlic, ginger, bilberry, danshen, piracetam, and ginkgo biloba) and xanthines containing beverages, found in coffee and tea, can reduce the effectiveness of Dipyridamole.

Dipyridamole is contraindicated in patients with

● Hypersensitivity to dipyridamole and any of the other components.

• Coronary Artery Disease

Dipyridamole has a vasodilatory effect and should be used with caution in patients with severe coronary artery disease (e.g., unstable angina or recently sustained myocardial infarction). Chest pain may be aggravated in patients with underlying coronary artery disease who are receiving dipyridamole.

• Hepatic Insufficiency

Elevations of hepatic enzymes and hepatic failure have been reported in association with dipyridamole administration.

• Hypotension

Dipyridamole should be used with caution in patients with hypotension since it can produce peripheral vasodilation.

• Stress Testing with Intravenous Dipyridamole and Other Adenosinergic Agents

Clinical experience suggests that patients being treated with Dipyridamole tablets who also require pharmacological stress testing with intravenous dipyridamole or other adenosinergic agents (e.g. adenosine, regadenoson) should interrupt Dipyridamole tablets for 48 hours prior to stress testing. Intake of Dipyridamole tablets within 48 hours prior to stress testing with intravenous dipyridamole or other adenosinergic agents may increase the risk for cardiovascular side effects of these agents and may impair the sensitivity of the test.

As dipyridamole is excreted in human milk, caution should be exercised when Dipyridamole tablets are administered to a nursing woman.

Adverse events have not been observed in animal reproduction studies. Dipyridamole should be used during pregnancy only if clearly needed; safety has not been established during pregnancy, but this drug has been used without apparent harmful effects.

Avoid herbs and supplements with anticoagulant/antiplatelet activity (eg. garlic, ginger, bilberry, danshen, piracetam, and ginkgo biloba) and xanthines containing beverages, found in coffee and tea, can reduce the effectiveness of Dipyridamole.

• Common Adverse effects

Exacerbation of Angina pectoris, flushing, Dizziness, Headache, Skin rash, pruritus, abdominal distress, diarrhea, vomiting, hepatic insufficiency.

• Rare Adverse effects

Abdominal pain, arthralgia, ataxia, back pain, bronchospasm, cardiac arrhythmia, cardiomyopathy, cough, depersonalization, diaphoresis, dysgeusia, dyspepsia, dysphagia, ECG abnormality, eructation, flatulence, hypersensitivity reaction, hypertonia, hyperventilation, increased appetite, increased thirst, injection site reaction, leg cramps, malaise, mastalgia, muscle rigidity, myalgia, myocardial infarction, orthostatic hypotension, Alopecia, arthritis, cholelithiasis, dyspepsia, fatigue, hepatitis, hypersensitivity reaction, hypotension, laryngeal edema, malaise, myalgia, nausea, palpitations, paresthesia, tachycardia, thrombocytopenia, otalgia, palpitations, perineal pain, pharyngitis, pleuritic chest pain, pruritus, renal pain, rhinitis, skin rash, syncope, tenesmus, tinnitus, tremor, urticaria, vertigo, visual disturbance, vomiting, weakness, xerostomia.

• Adenosinergic Agents

Dipyridamole has been reported to increase the plasma levels and cardiovascular effects of adenosine. Adjustment of adenosine dosage may be necessary. Dipyridamole also increases the cardiovascular effects of regadenoson, an adenosine A2A receptor agonist. The potential risk of cardiovascular side effects with intravenous adenosinergic agents may be increased during the testing period when dipyridamole is not held 48 hours prior to stress testing.

• Cholinesterase Inhibitors

Dipyridamole may counteract the anticholinesterase effect of cholinesterase inhibitors, thereby potentially aggravating myasthenia gravis.

• Other Anticoagulants

Anticoagulants agents with Antiplatelet Properties may enhance the anticoagulant effect of Anticoagulants.

The common side effects of Dipyridamole include the following

• Common

Dizziness, stomach pain, headache, rash, diarrhea, vomiting, flushing (feeling of warmth), itching.

• Rare

Chest pain, unusual bleeding, or bruising, yellowing of the skin or eyes

• Pregnancy

Pregnancy Category B

Teratogenic Effects Reproduction studies have been performed in mice, rabbits and rats at oral dipyridamole doses of up to 125 mg/kg, 40 mg/kg and 1000 mg/kg, respectively (about 1 ½, 2 and 25 times the maximum recommended daily human oral dose, respectively, on a mg/m2 basis) and have revealed no evidence of harm to the fetus due to dipyridamole. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, Dipyridamole tablets should be used during pregnancy only if clearly needed.

• Nursing Mothers

As dipyridamole is excreted in human milk, caution should be exercised when Dipyridamole tablets are administered to a nursing woman.

• In case of real or suspected overdose, seek medical attention or contact a Poison Control Center immediately. Careful medical management is essential. Based upon the known hemodynamic effects of dipyridamole, symptoms such as warm feeling, flushes, sweating, restlessness, feeling of weakness and dizziness may occur. A drop in blood pressure and tachycardia might also be observed.
• Symptomatic treatment is recommended, possibly including a vasopressor drug. Gastric lavage should be considered. Administration of xanthine derivatives (e.g., aminophylline) may reverse the hemodynamic effects of dipyridamole overdose. Since dipyridamole is highly protein bound, dialysis is not likely to be of benefit.

Pharmacodynamic

Dipyridamole, a non-nitrate coronary vasodilator that also inhibits platelet aggregation, is combined with other anticoagulant drugs, such as warfarin, to prevent thrombosis in patients with valvular or vascular disorders. Dipyridamole is also used in myocardial perfusion imaging, as an antiplatelet agent, and in combination with aspirin for stroke prophylaxis.

Pharmacokinetics

• Absorption

Dipyridamole is incompletely absorbed from the GI tract. Time to peak plasma concentrations is approximately 75 minutes.

• Distribution

Dipyridamole is widely distributed into body tissues. It crosses the placenta in small amounts and enters breast milk. The Volume of distribution of dipyridamole is about 2-3 L/kg. The Plasma protein binding is approximately 91-99%, mainly to α₁-acid glycoprotein.

• Metabolism and Excretion
  

Dipyridamole is metabolized in the liver to glucuronide conjugate; may undergo enterohepatic recirculation. The terminal elimination half-life of Dipyridamole is about 10-12 hours. It is excreted in feces (as glucuronide conjugates and unchanged drug).

• https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/012836s061lbl.pdf
• https://www.rxlist.com/Dipyridamole-drug.htm#indications
• https://reference.medscape.com/drug/Dipyridamole-dipyridamole-342147
• https://go.drugbank.com/drugs/DB00975
• https://www.drugs.com/dosage/dipyridamole.html
• https://www.uptodate.com/contents/dipyridamole-drug-information#F161399
• https://www.mims.com/singapore/drug/info/dipyridamole?mtype=generic
• https://medlineplus.gov/druginfo/meds/a682830.html#precautions
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