Local anticoagulation without systemic effect using a polymer heparin delivery system.

Polymeric drug delivery systems that allow the application of substances to a localized region for specified periods of time have been developed. A model for intravascular thrombosis in the rat common carotid artery was established using a combination of balloon catheter endothelial injury with 1-hour occlusion of the vessel. After endothelial injury in 11 Sprague-Dawley rats, the adventitial surface of the carotid artery was exposed to the polymer polyvinyl alcohol (PVA) containing heparin and was compared with exposure to PVA alone in the contralateral (control) vessel. Subsequent determinations of the coagulation parameters systemic prothrombin and partial thromboplastin times showed no systemic effect of heparin. All 11 control vessels demonstrated complete or partial thrombosis, whereas only one of 11 heparin/PVA-treated vessels showed a small thrombus. Morphometric analysis of the cross-sectional thrombus: lumen ratio in 10 rats showed a significant reduction (p less than 0.005) in thrombus size for treated vessels (4.1 +/- 9.6%) compared with control vessels (60.2 +/- 25.8%). Scanning electron microscopy verified the absence of thrombus in the treated vessels despite complete endothelial desquamation. In a second group of eight rats, endothelial injury without occlusion did not cause thrombosis in treated or control arteries. The coagulation parameters for this group of eight unoccluded rats were similarly unaffected by heparin/PVA treatment. Our observations suggest that a localized antithrombotic effect of heparin can be achieved without systemic anticoagulation using a polymeric drug delivery system. This technique may be applied to a variety of surgical and nonsurgical clinical conditions.