Dipiridamol

Uses

Dipiridamol is used for Prophylaxis of thromboembolism following cardiac valve replacement, Secondary prophylaxis of stroke or transient ischaemic attack

Dipiridamol is also used to associated treatment for these conditions: Coronary Artery Disease (CAD), Postoperative Thromboembolism, Stroke, Transient Ischemic Attack, Thrombotic events, Anti-platelet Therapy

How Dipiridamol works

Dipiridamol 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. Dipiridamol also directly stimulates the release of prostacyclin, which induces adenylate cyclase activity, thereby raising the intraplatelet concentration of cAMP and further inhibiting platelet aggregation.

Dosage

Dipiridamol dosage

Prophylaxis of thromboembolism following cardiac valve replacement:

• Adult: 300-600 mg/day in divided doses with an oral anticoagulant.
• Child: 5 mg/kg/day in divided doses.

Secondary prophylaxis of stroke or transient ischaemic attack:

• Adult: As modified-release preparation: 200 mg bid, with or without aspirin.

Should be taken on an empty stomach. Take 1 hr before meals. May be taken with meals to reduce GI discomfort.

Side Effects

GI disturbances, headache, dizziness, faintness, facial flushing, skin rash, liver dysfunction, angina. Large doses may lower BP.

Toxicity

Hypotension, if it occurs, is likely to be of short duration, but a vasopressor drug may be used if necessary. The oral LD₅₀ in rats is greater than 6,000 mg/kg while in the dogs, the oral LD₅₀ is approximately 400 mg/kg. LD₅₀=8.4g/kg (orally in rat)

Precaution

In patients with rapidly worsening angina, subvalvular aortic stenosis, haemodynamic instability associated with recent MI or coagulation disorders esp when given IV during myocardial imaging. Hypotension, unstable angina, aortic stenosis. Pregnancy and lactation. Safety and efficacy are not established in childn < 12 yrs.

Interaction

Aminophylline may reverse vasodilatation effect. Useful combination with aspirin in prevention of thromboembolism. Efficacy reduced by concurrent admin of antacids. Concurrent use may increase the cardiotoxic effects of adenosine.

Food Interaction

• Avoid herbs and supplements with anticoagulant/antiplatelet activity. Examples include garlic, ginger, bilberry, danshen, piracetam, and ginkgo biloba.
• Avoid xanthines. Xanthines, found in coffee and tea, can reduce the effectiveness of this medication.
• Take with or without food. Taking dipyridamole extrended release capusels with a high-fat meal minimally reduces it's AUC and Cmax.

[Moderate] ADJUST DOSING INTERVAL: Caffeine and other xanthine derivatives (e.g., theophylline) are nonspecific, competitive antagonists of adenosine receptors.

As such, they may interfere with the vasodilating effect of dipyridamole, an adenosine receptor agonist.

In studies of healthy volunteers, caffeine has been shown to reduce the hemodynamic response (i.e., heart rate increases, vasodilation, blood pressure changes) to dipyridamole infusions, and both caffeine and theophylline have been reported to cause false-negative results in myocardial scintigraphy tests using dipyridamole.

MANAGEMENT: Patients should avoid consumption of caffeine-containing products for at least 24 hours prior to administration of dipyridamole for myocardial perfusion imaging.

Dipiridamol Drug Interaction

Moderate: omega-3 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acidsUnknown: aspirin, aspirin, aspirin, aspirin, atorvastatin, atorvastatin, pregabalin, pregabalin, acetaminophen, acetaminophen, clopidogrel, clopidogrel, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol

Dipiridamol Disease Interaction

Major: bronchospasmModerate: conduction abnormalities, hypotension, myasthenia gravis

Volume of Distribution

• 1 to 2.5 L/kg

Elimination Route

70%

Half Life

40 minutes

Clearance

• 2.3-3.5 mL/min/kg

Elimination Route

Dipiridamol is metabolized in the liver to the glucuronic acid conjugate and excreted with the bile.

Pregnancy & Breastfeeding use

Pregnancy Category B. Either animal-reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the 1st trimester (and there is no evidence of a risk in later trimesters).

Contraindication

Hypersensitivity. Peptic ulcer.

Acute Overdose

Symptoms: warm feeling, flushes, sweating, restlessness, weakness, dizziness, hypotension and tachycardia.

Management: treatment is symptomatic. Empty stomach by gastric lavage. Haemodialysis unlikely to be useful.

Storage Condition

Store below 25° C.

Innovators Monograph

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