Dipyramidole pharmacology (1)

Dipyramidole

1. DIPYRAMIDAMOLE

2. Dipyramidamole Powerful coronary vasodilator Obsolete – not used these days It dilates both conducting vessels & resistance vessels and abolishes auto regulation. However, it is not effective in angina because of Coronary steal phenomenon .

3. CORONARY STEAL PHENOMENON Coronary steal is a phenomenon where an alteration of circulation patterns leads to a reduction in the blood flow directed to the coronary circulation. It is caused when there is narrowing of the coronary arteries and a coronary vasodilator is used – "stealing" blood away from those parts of the heart. This happens as a result of the narrowed coronary arteries being always maximally dilated to compensate for the decreased upstream blood supply. Thus, dilating the resistance vessels in the coronary circulation causes blood to be shunted away from the coronary vessels supplying the ischemic zones, creating more ischemia. .

4. Uses

5. 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.

6. Absorption 70% ( when given orally ) Metabolism Dipyridamole is metabolized in the liver to the glucuronic acid conjugate and excreted with the bile. Half life 40 mins Excretion Through urine Clearance - 2.3-3.5 mL /min/kg Pharmacokinetics

7. Side effects Headache Diarrhoea Vomiting Flushing Rashes, itching Dizziness Uses Dipyramidamole has vasodilator & anti-platelet action. It is used in Post-MI & Post-stroke to prevent coronary & cerebral thrombosis. It is used to prevent blood clots after heart valve replacement .