ABSTRACT
Heparin is a highly sulphated linear polysaccharide that was discovered in 1916 as an anticoagulant. Heparin binds to antithrombin III, thereby inducing a conformational change. This results in inhibition of thrombin and other serine proteases involved in the blood clotting cascade immediately after administration. The actions of heparin on neointimal proliferation are complex. This was demonstrated by Edelman et al.1 They found an increase of intimal hyperplasia after arterial injury in the rat model when heparin was administered once daily. Twice daily administration had different effects depending on the time-interval of dosing but very significant reduction in intimal hyperplasia was seen with continuous administration. Clowes et al. showed that heparin should be administered for 4-7 days in order to have an antiproliferative effect after injury.2
