Drugs commonly used in Vascular Surgery

Heparin

• Mucopolysaccharide which is negatively charged, complexes with positively charged plasma proteins.
• Extracted from mast cells of animal tissue.
• 1/2 life is 1 1/2 hours.
• Slows the conversion of prothrombin to thrombin.
• Potentiates the effects of antithrombin III.
• Decreases platelet adhesiveness.
• Monitored by measuring PTT.
• Neutralized with IV protamine sulfate at a dose of 1mg protamine sulfate/100 units of active heparin.

Coumadin (Sodium warfarin)

• Oral dosing
• Inhibits the production of the vitamin K dependent factors II, VII, IX, X.
• May take up to three days to take effect.
• Metabolized by the liver.
• 1/2 life is 36 hours.
• Reversal with IM vitamin K and fresh frozen plasma.
• Monitored by Prothrombin time (PT).

see figure 1

Aspirin

• Inhibits the entire prostaglandin pathway by irreversibly acetylation cyclooxygenase.
• This inhibits prostacyclin and thromboxane production.
• Small doses of aspirin (100 mg/day) selectively inhibit platelet cyclooxygenase more than endothelial cyclooxygenase, with a net effect of decreasing platelet aggregation in response to injury.

see figure 2

Persantine

• Phosphodiesterase inhibitor which acts by inhibiting the breakdown of cAMP within platelets.
• Net result is that there is an increase in platelet cAMP which decrease platelet aggregation.
• When used with aspirin there is an enhanced effect.

Pentoxifylline (Trental)

• Used to treat patients with intermittent claudication.
• Works by altering the rheology of the red blood cell membrane.
• Can increase walking distance 25-40%.

Source:  Vascular Surgery for the House Officer, 2nd edition; Jon R. Cohen