CATHETER-BASED DRUG-DELIVERY FOR RESTENOSIS

Despite high initial success rates, balloon angioplasty and all other percutaneous revascularization procedures continue to be limited by ab rupt vessel closure in up to 8% of cases and restenosis at the site of arterial injury in 30-50% of cases. With the possible exception of st ents, the failure of mechanical devices and systemic pharmacologic the rapies to prevent or even significantly modify the restenotic process has provoked intense interest in alternative approaches. Interest has therefore shifted from systemically administered agents for the preven tion of restenosis to the direct delivery of potentially useful compou nds to the site of arterial injury following coronary angioplasty. Rap id advances in intravascular imaging and molecular cardiology have exp anded our understanding of the physical and biological components of t he response to arterial injury increases, and targeted therapy taking individual patient and lesion characteristics into account promises to become a reality. An ideal local drug delivery system should achieve efficient site-specific drug transfer producing a high concentration o f drug at the treatment site, while minimizing the systemic effects wh ich would be expected from systemic doses sufficient to obtain similar local concentrations. Local delivery devices may be broadly classifie d as balloon catheter delivery systems, polymeric or coated stents, or devices for 'facilitated diffusion'. Drug delivery may be directly vi a these devices, or may be enhanced by the use of local delivery vehic les such as controlled release matrices, gene vectors, cell targeting, or drug-loaded platelets. This review will concentrate on balloon cat heter-based delivery devices. Recent approval of two balloon catheter local delivery systems for clinical use heralds the onset of an exciti ng new era of sophisticated, specific and effective vascular therapy.