Drug-eluting stents generally consist of three parts - the stent platform, a polymer coating that binds the drug to the stent and releases drug (although stents have been tested that do without a coating), and the drug.

The stent platform itself is an expandable framework, generally with an elaborate mesh-like design to allow expansion, flexibility, and in some cases the ability to make/enlarge side openings for side vessels.
 The first DES were stainless steel alloys composed of iron, nickel, and chromium and were based on existing bare metal stents.
 These stents were hard to visualize with medical imaging, posed a risk of causing allergic responses, and were difficult to deliver, and subsequent new alloys were brought to bear, namely cobalt-chrome and platinum chrome, with improved performance.
 Subsequently, bioresorbable stents have been developed in which the stent itself dissolves over time.
  As of 2009, materials that had been explored included magnesium, polylactic acid, polycarbonate polymers, and salicylic acid polymers.
 Resorbable stents have held the promise of providing an acute treatment that would eventually allow the vessel to function normally, without leaving a permanent device behind.

One to three or more layers of polymer can be used in the coating, e.g., a base layer for adhesion, a main layer that holds and elutes (releases) the drug into the arterial wall by contact transfer, and sometimes a top coat to slow down the release of the drug and extend its effect.
The first few drug-eluting stents to be licensed used durable coatings.
 The first generation coatings appear to have caused immunological reactions at times and some possibly led to thrombosis, which has driven experimentation and development of new coating approaches.

The drug is mainly to inhibit neointimal growth (due to the proliferation of smooth muscle cells) that would cause restenosis.
   Much of the neointimal hyperplasia seems to be caused by inflammation.
Hence, immunosuppressive and antiproliferative drugs are used.
Sirolimus, paclitaxel, and everolimus were previously used for other medical applications and have been included in licensed DES.
Drug-eluting stents generally consist of three parts - the stent platform, a polymer coating that binds the drug to the stent and releases drug (although stents have been tested that do without a coating), and the drug.
The stent platform itself is an expandable framework, generally with an elaborate mesh-like design to allow expansion, flexibility, and in some cases the ability to make/enlarge side openings for side vessels.  The first DES were stainless steel alloys composed of iron, nickel, and chromium and were based on existing bare metal stents.  These stents were hard to visualize with medical imaging, posed a risk of causing allergic responses, and were difficult to deliver, and subsequent new alloys were brought to bear, namely cobalt-chrome and platinum chrome, with improved performance.  Subsequently, bioresorbable stents have been developed in which the stent itself dissolves over time.   As of 2009, materials that had been explored included magnesium, polylactic acid, polycarbonate polymers, and salicylic acid polymers.  Resorbable stents have held the promise of providing an acute treatment that would eventually allow the vessel to function normally, without leaving a permanent device behind.
One to three or more layers of polymer can be used in the coating, e.g., a base layer for adhesion, a main layer that holds and elutes (releases) the drug into the arterial wall by contact transfer, and sometimes a top coat to slow down the release of the drug and extend its effect. The first few drug-eluting stents to be licensed used durable coatings.  The first generation coatings appear to have caused immunological reactions at times and some possibly led to thrombosis, which has driven experimentation and development of new coating approaches.
The drug is mainly to inhibit neointimal growth (due to the proliferation of smooth muscle cells) that would cause restenosis.    Much of the neointimal hyperplasia seems to be caused by inflammation. Hence, immunosuppressive and antiproliferative drugs are used. Sirolimus, paclitaxel, and everolimus were previously used for other medical applications and have been included in licensed DES.
Drug-eluting stent