Hydrogel-forming sustained-release preparation

Abstract

The invention provides a hydrogel-type sustained-release preparation comprising (1) at least one drug, (2) an additive which insures a penetration of water into the core of the preparation and (3) a hydrogel-forming polymer, wherein said preparation is capable of undergoing substantially complete gelation during its stay in the upper digestive tract such as stomach and small intestine and is capable of releasing the drug in the lower digestive tract including colon. By the preparation of the invention, the drug is efficiently released and absorbed even in the colon so that a steady and sustained release effect can be achieved.

1 . A hydrogel-type sustained-release preparation comprising (1) at least one drug, (2) an additive which insures a penetration of water into the core of the preparation and (3) a hydrogel-forming polymer, wherein said preparation is capable of undergoing substantially complete gelation during its stay in the upper digestive tract including stomach and small intestine and is capable of releasing the drug in the lower digestive tract including colon.  
     
     
         2 . The hydrogel-type sustained-release preparation according to  claim 1 , wherein said additive which insures a penetration of water into the core of the preparation is at least one additive having a solubility that the volume of water required for dissolving 1 gram of said additive is not more than 5 ml.  
     
     
         3 . The hydrogel-type sustained-release preparation according to  claim 2 , wherein said additive which insures a penetration of water into the core of the preparation is at least one additive having a solubility that the volume of water required for dissolving 1 gram of said additive is not more than 4 ml.  
     
     
         4 . The hydrogel-type sustained-release preparation according to  claim 1 , wherein said hydrogel-forming polymer is either a polymer having an average molecular weight of not less than 2,000,000 or a polymer having a viscosity of not less than 1000 cps as measured at 1% concentration in water at 25° C., or a mixture of two or more of these polymers.  
     
     
         5 . The hydrogel-type sustained-release preparation according to  claim 1  or  4 , wherein said hydrogel-forming polymer includes at least one polyethylene oxide.  
     
     
         6 . The hydrogel-type sustained-release preparation according to any one of  claims 1  to  5 , which comprises (1) at least one drug in an amount of not more than 85% by weight based on the total preparation, (2) an additive which insures a penetration of water into the core of the preparation in an amount of from 5 to 80% by weight based on the total preparation, and (3) a hydrogel-forming polymer in an amount of from 10 to 95% by weight based on the total preparation.  
     
     
         7 . The hydrogel-type sustained-release preparation according to any one of  claims 1  to  6 , which comprises (1) at least one drug in an amount of not more than 80% by weight based on the total preparation, (2) an additive which insures a penetration of water into the core of the preparation in an amount of from 5 to 60% by weight based on the total preparation, and (3) a hydrogel-forming polymer in an amount of from 15 to 90% by weight based on the total preparation.  
     
     
         8 . The hydrogel-type sustained-release preparation according to any one of  claims 1  to  7 , wherein said drug is nicardipine hydrochloride.