Implantable Medical Device with Drug Filled Holes

Abstract

The present invention relates to implantable medical devices for delivery of therapeutic agents, such as drugs, to a patient. More particularly, the invention relates to a device having therapeutic agents protected by a protective layer that prevents or retards processes that deactivate or degrade the active agents.

1 . An implantable medical device comprising: 
 an implantable device body having a plurality of through holes therein;    a barrier formed in the plurality of through holes, the barrier formed of a biodegradable copolymer having a first copolymer ratio;    a drug filled portion formed in the plurality of through holes adjacent the barrier; and    a cap formed in the plurality of through holes adjacent the drug filled portion, the cap formed of the biodegradable copolymer having a second copolymer ratio wherein the second copolymer ratio is different from the first copolymer ratio.    
     
     
         2 . The device of  claim 1 , wherein the implantable medical device is a stent.  
     
     
         3 . The device of  claim 2 , wherein the drug filled portion comprises a drug for prevention of restenosis.  
     
     
         4 . The device of  claim 1 , wherein the barrier, the drug filled portion, and the cap are formed by loading compositions dropwise into the through holes.  
     
     
         5 . The device of  claim 1 , wherein the biodegradable copolymer is poly(lactide-co-glycolide).  
     
     
         6 . The device of  claim 5 , wherein the first copolymer ratio is 85:15.  
     
     
         7 . The device of  claim 5 , wherein the second copolymer ratio is 50:50.  
     
     
         8 . The device of  claim 1 , wherein the first and second copolymer ratios are selected such that following implantation the cap degrades faster than the barrier.  
     
     
         9 . The device of  claim 2 , wherein the barrier is formed adjacent a luminal surface of the stent and the cap degrades faster than the barrier.  
     
     
         10 . The device of  claim 1 , wherein the drug filled portion includes a limus drug.  
     
     
         11 . The device of  claim 1 , wherein the drug filled portion includes a water sensitive drug.  
     
     
         12 . A method of forming an implantable medical device comprising: 
 forming an implantable device body having a plurality of through holes therein;    loading a mixture of a biodegradable copolymer having a first copolymer ratio and a first solvent into the holes and evaporating the first solvent to form a barrier;    loading a mixture of a drug, a polymer, and a second solvent into the holes and evaporating the second solvent to form a drug portion; and    loading a mixture of the biodegradable copolymer having a second copolymer ratio and a third solvent into the holes and evaporating the third solvent to form a cap wherein the second copolymer ratio is different from the first copolymer ratio.    
     
     
         13 . The method of  claim 12 , wherein the first, second, and third solvents are the same.  
     
     
         14 . The method of  claim 12 , wherein the implantable medical device is a stent.  
     
     
         15 . The method of  claim 12 , wherein the drug comprises a drug for prevention of restenosis.  
     
     
         16 . The method of  claim 12 , wherein the loading steps include loading the mixtures dropwise into the through holes.  
     
     
         17 . The method of  claim 12 , wherein the biodegradable copolymer is poly(lactide-co-glycolide).  
     
     
         18 . The method of  claim 17 , wherein the first copolymer ratio is 85:15.  
     
     
         19 . The method of  claim 17 , wherein the second copolymer ratio is 50:50.  
     
     
         20 . The method of  claim 12 , wherein the first and second copolymer ratios are selected such that following implantation the cap degrades faster than the barrier.  
     
     
         21 . The method of  claim 14 , wherein the barrier is formed adjacent a luminal surface of the stent and the cap degrades faster than the barrier.  
     
     
         22 . The method of  claim 12 , wherein the drug comprises a limus drug.  
     
     
         23 . The method of  claim 12 , wherein the drug comprises a water sensitive drug.