Dipyridamole
Dipyridamole
Description
· A phosphodiesterase inhibitor that blocks uptake and metabolism of adenosine by erythrocytes and vascular endothelial cells. Dipyridamole also potentiates the anti-aggregating action of prostacyclin.
Mechanism of Action
· 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.
Pharmacokinetics
· Following an oral dose of Dipyridamole tablets, the average time to peak concentration is about 75 minutes. The decline in plasma concentration fits a two-compartment model with an α half-life (initial decline following peak concentration) of 40 minutes and a β half-life of 10 hours. This is consistent with the twice-daily regimen used in recent clinical studies.
· Absorption of dipyridamole from conventional formulations is quite variable and can result in low systemic bioavailability. A modified-release formulation of dipyridamole with improved bioavailability has been developed. Dipyridamole is highly bound to plasma proteins, and is metabolized in the liver where it is conjugated to a glucuronide and excreted in the bile. It is subject to enterohepatic recirculation.
Uses
· This medication is used in combination with "blood thinners" such as warfarin to keep clots from forming after heart valve replacements. Clots are a serious complication that can cause strokes, heart attacks, or blocked blood vessels in the lungs (pulmonary embolisms).
· Dipyridamole is an antiplatelet drug. It helps to keep blood flowing by stopping platelets from clumping together and by keeping heart blood vessels open.
Side Effects
· Dizziness, stomach upset, diarrhea, vomiting, headache, and flushing may occur as your body adjusts to the medication. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
· To reduce the risk of dizziness and light headedness, get up slowly when rising from a sitting or lying position.
References
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