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..
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.
7. 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
