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Method for producing a controlled release preparationRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Preparations Characterized By Special Physical Form, Tablets, Lozenges, Or Pills, Sustained Or Differential Release Type, Discrete Particles In Supporting MatrixMethod for producing a controlled release preparation description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060159755, Method for producing a controlled release preparation. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present application is a continuation of U.S. patent application Ser. No. 09/819,813, filed on Mar. 29, 2001, which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention concerns a method for producing a pharmaceutical preparation. Specifically the invention concerns a method for producing a controlled-release pharmaceutical preparation with a particle-containing coating. The invention also concerns new pharmaceutical preparations. BACKGROUND OF THE INVENTION [0003] Many polymers are used as coatings in controlled release oral pharmaceutical preparations. These polymers are essentially water-insoluble and have consequently low permeability towards water and drugs. If the drug is very soluble and surface of the preparation is large, as in e.g. pellets, low permeability is desired. If the drug is moderately soluble or the surface of the preparation is small, as in e.g. tablets, the permeability of the coating has to be increased. [0004] One method of increasing the permeability of the polymer is disclosed in the U.S. Pat. No. 4,629,619. According to this patent the permeability is increased by including water soluble particles in the coating. When the preparation is subsequently swallowed by a patient and contacted with the GI juices, the water soluble particles dissolve and form pores or channels in the coating through which pores or channels the drug is released from the preparation. The coating including these water soluble pore-forming particles is obtained by a method according to which the water-soluble particles are suspended in an organic solvent. Medical preparations developed according to this patent are currently used and well accepted by the patients. A disadvantage is however the necessity to use organic solvents. [0005] Another method of increasing the permeability is disclosed in the U.S. Pat. No. 5,472,712 and 5,639,476. According to these two patents the permeability of the polymer is increased by including a water-soluble material in the polymer. The coating including the water soluble material is obtained by dissolving the water soluble material in the aqueous dispersion of a film-forming polymer. When such a preparation is subsequently swallowed and contacted with the GI juices the water soluble material dissolves and make the polymer coating micro-porous and increase the release rate of the drug through the coating. The sizes of the micro-pores correspond to those of the dissolved molecules. An advantage with medical preparations prepared according to these two patents is that they may be prepared without organic solvent. A disadvantage is that the mechanical strength of the coating is poor, when the permeability is increased to an acceptable level for moderately soluble drugs, especially for tablets. Another disadvantage is that the size of the pores is not controlled which means e.g. that it is difficult to obtain reproducible products. [0006] The permeability increasing or pore-forming agents used according to the two above methods may be identical chemically but the physical state of these agents in the coating solution is different. OBJECT OF THE INVENTION [0007] An object of the present invention is therefore to accomplish a method for producing a controlled-release pharmaceutical preparation having the same effective release rate and mechanical strength as the one described in U.S. Pat No. 4,557,925 while avoiding the use of organic solvents and the problems arising by using the method according to U.S. Pat. No. 5,472,712 and 5,639,476. SUMMARY OF THE INVENTION [0008] This object as well as other objects that will be apparent from the description below, have now been obtained according to the present invention by providing a method for producing an essentially zero order, controlled release pharmaceutical preparation with a particle containing coating according to claim 1. [0009] This method comprises the steps of: [0010] preparing a drug-containing solid core; [0011] suspending a pore-forming agent having a balanced solubility in an aqueous dispersion of a film-forming, water insoluble polymer in order to form a coating suspension having a predetermined amount of solid particles of the pore-forming agent suspended therein; [0012] coating the solid core with the obtained suspension; and drying the coated tablet. [0013] By a careful selection of the type, amount and particle size of the pore-forming agent, the coating of the final tablet will contain comparatively large particles of the pore-formers. When the tablet is then contacted with the GI juices of a patient, these particles dissolve and create a network of canals or pores of a predetermined size in the polymer coating and the drug is released through these pores or canals. Due to this network the coating will get good mechanical stability and the polymer film will be left intact after the release of the drug. [0014] A predetermined release rate may be obtained by selecting the above parameters of the pore-forming agent in combination with type and amount of film forming polymer. The coatings thus prepared have a good mechanical stability and are left intact after the release of the drug and the pore-forming agent. [0015] The problem to be solved by the present invention is thus to find a pore-creating agent or pore-former combining the two seemingly non compatible properties of being, on one hand sufficiently insoluble in the aqueous coating dispersion, and on the other hand sufficiently soluble in the aqueous GI juices. In this context this feature is referred to as "balanced solubility". DETAILED DESCRIPTION OF THE INVENTION [0016] The critical pore-forming agent must be a pharmaceutically acceptable substance that can be added to the aqueous dispersion of the film-forming polymer without being completely dissolved. Important factors for the pore-forming agent are its solubility and mean particle size. The solubility of the pore-forming agent is below 200 mg/ml in the coating solution at 25.degree. C. Preferably the solubility is below 100 mg/ml, more preferably below 50 and most preferably below 30 mg/ml. [0017] The mean particle size of the pore-forming agent when added to the coating solution is 0.1-500 .mu.m, preferably 0.5-100 .mu.m and most preferably 1.0-25 .mu.m. [0018] If larger particles are used it will be difficult to get reproducible preparations and if smaller particles are used manufacturing problems are expected. [0019] The predetermined amount of solid particles of the pore-forming agent in the coating solution is selected by the man skilled in the art in view of the specific drug and polymer used and the desired release rate. [0020] In a preferred embodiment of the invention the pore-forming agent is selected from the group consisting of potassium hydrogen tartrate (potassium bitartrate), creatine, aspartic acid, glutamic acid and inosine. [0021] Other preferred pore-forming agents are chitosan and poly(butyl methacrylate, (2-dimethyl aminoethyl) methacrylate, methyl methacrylate) 1:2:1. [0022] Other pore-forming agents which may be used selected from a group consisting of potassium salts, calcium salts, magnesium salts, amino acids, week acids, carbohydrates, polymers with amino and/or acid functions. Examples are aspargine, glutamine, leucin, neroleucine, isoleucine, magnesium citrate, magnesium phosphate, magnesium carbonate, magnesium hydroxide, magnesium oxide or a composition wherein at least one component is selected from one of these substances. Continue reading about Method for producing a controlled release preparation... Full patent description for Method for producing a controlled release preparation Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method for producing a controlled release preparation patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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