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Implantation of Drug Eluting Stents (DES) is the most accepted technique currently available to treat cardiovascular blockages. First generation DES uses polymers for drug delivery which are nondegradable in nature and remains attached to stent surface lifetime. Biodegradable polymers have gained immense attention for controlled drug delivery of therapeutic drugs from cardiovascular stents in recent times as nondegradable polymers are associated with long-term adverse events. Studies showed that permanent contact with this polymer creates local inflammatory reactions and long-term stent thrombosis which raises concerns over the widespread use of DES. Biodegradable polymers are widely accepted biomaterials in human health care area and have proved its biocompatibility as drug delivery vehicle in various medicinal applications. This research work is carried out to study mechanisms affecting drug release kinetics from coated cardiovascular stents composed of biodegradable poly lactide-cocaprolactone and polyvinyl pyrrolidone. A conventional air brush technique was effectively modified so that CoÀCr L605 metallic stents were coated within multiple layers having drug Sirolimus blended together with biodegradable polymeric matrix. Kinetic studies for drug dissolution from a stent are carried out in simulated biological fluid using high performance liquid chromatography (HPLC) with simultaneous monitoring of surface morphology by scanning electron microscopy (SEM). Drug elution data analyzed by mathematical models suggested a combination of surface drug dissolution and diffusion as major drug release mechanisms. Investigation of different top coats revealed that drug release is influenced by the hydrophobicity of the drug free protective layer.

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-Utilization of biodegradable polymers for controlled drug delivery has gained immense attention in the pharmaceutical and medical device industry to administer various drugs, proteins and other biomolecules both systematically and locally to cure several diseases. The efficacy and toxicity of this local therapeutics depends upon drug release kinetics, which will further decide drug deposition, distribution, and retention at the target site. Drug Eluting Stent (DES) presently possesses clinical importance as an alternative to Coronary Artery Bypass Grafting due to the ease of the procedure and comparable safety and efficacy. Many models have been developed to describe the drug delivery from polymeric carriers based on the different mechanisms which control the release phenomenon from DES. Advanced characterization techniques facilitate an understanding of the complexities behind design and related drug release behavior of drug eluting stents, which aids in the development of improved future drug eluting systems. This review discusses different drug release mechanisms, engineering principles, mathematical models and current trends that are proposed for drug-polymer coated medical devices such as cardiovascular stents and different analytical methods currently utilized to probe diverse characteristics of drug eluting devices.