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- Action:
    - powerful vasodilator and inhibits platelet aggregation thru activation of adenylate cyclase, which leads to an increase in intracellular cyclic adenosine monophosphate;
    - prostacyclin and thromboxane A(sub 2) are formed from arachidonic acid, w/ endoperoxides & prostaglandins G2 and H2 as 
         intermediates;
    - variety of drugs with diverse mechanisms of action are reputed to increase prostacyclin production;
         - include calcium antagonists, captopril, dipyridamole, diuretic agents, nitrates, and streptokinase;
         - fall in BP induced by several antihypertensive drugs, including propranolol, is reduced by Aspirin, suggesting that prostacyclin may 
              have a more general role in their activity;
    - it causes relaxation of the underlying smooth muscle, and in the lumen it prevents platelets and perhaps other blood cells from clumping
         onto the endothelium;
- Steroids:
    - inhibit prostacyclin synthesis in endothelial & other cells by stimulating formation of lipocortin, endogenous inhibitor of
         phospholipase A(sub 2) activity;
    - inhibits phospholipase A(sub 2), & Aspirin-like drugs, by inhibiting cyclooxygenase, reduce synthesis of prostacyclin & Thromboxane