the pharmaceutically active ingredient or drug that is used in the present invention is an opiate which includes natural and synthetic opioids as well as the active metabolites such as morphine - 6 - glucuronide and morphine - 3 - glucuronide . the term also includes pharmaceutically acceptable salts and / or complexes of opioids . some examples of opioids are alfentanil , allylprodine , alphaprodine , anileridine , benzylmorphine , bezitramide , buprenorphine , butorphanol , clonitazene , codeine , cyclazocine , desomorphine , dextromoramide , dezocine , diampromide , dihydrocodeine , dihydromorphine , dimenoxadol , dimepheptanol , dimethylthiambutene , dioxaphetyl butyrate , dipipanone , eptazocine , ethoheptazine , ethylmethylthiambutene , ethylmorphine , etonitazene fentanyl , heroin , hydrocodone , hydromorphone , hydroxypethidine , isomethadone , dextropropoxyphene , ketobemidone , levallorphan , levorphanol , levophenacylmorphan , lofentanil , meperidine , meptazinol , metazocine , methadone , metopon , morphine , myrophine , nalbuphine , narceine , nicormorphine , norlevorphanol , normethadone , nalorphine , normorphine , norpipanone , opium , oxycodone , oxymorphone , papaveretum , pentazocine , phenadoxone , phenomorphan , phenazocine , phenoperidine , piminodine , piritramide , propheptazine , promedol , properidine , propiram , propoxyphene , sufentanil , tilidine , and tramadol . in a preferred embodiment the opiate is morphine , and even more particularly morphine sulphate . the inorganic osmagent that is used in the core of the present invention is an inorganic material that attracts fluid into the core . the preferred inorganic osmagents are inorganic salts preferably , alkali and alkali earth metal salts . representative examples of the inorganic osmagents that are useful in the present invention include but are not limited to magnesium sulfate , potassium chloride , ammonium chloride , calcium sulfate , sodium chloride , lithium chloride , lithium sulfate , potassium sulfate , sodium sulfate , and the like or combinations thereof . other inorganic osmagents are described in u . s . pat . nos . 4 , 612 , 008 and 5 , 082 , 668 ; which are incorporated herein by reference . the preferred osmagent for use in the present invention is sodium chloride . the core or immediate release pellet of the present invention can be prepared by methods commonly known in the art such as wet granulation , dry granulation or extrusion spheronization . in a preferred embodiment of the present invention , the core or immediate release pellet is prepared with an inert starting seed such as a sugar seed with a mesh size of 15 - 40 , preferably 20 - 25 . if an inert starting seed is employed it must be of sufficient density and strength to enable it to undergo coating with the opiate and the controlled release composition . suitable starting seeds are sugar seeds or non - pariels that are well known in the art . additional suitable starting seeds may be chosen from plastic resins , silica , glass , microcrystalline cellulose , starches and other materials commonly known in the art . the opiate and inorganic osmagent can be applied to the inert starting seed by any conventional techniques known in the industry , such as , pan coating , roto - granulation or fluidized bed coating . during such coating operations the opiate is dispersed or dissolved in a solvent , which may also contain other conventional excipients . suitable excipients may be , but are not limited to organic osmagents , binding agents , surfactants , plasticizers , glidants , lubricants , stabilizers , ph modifying agents , solubilizers and combinations of the foregoing . although the aforementioned excipients are commonly known in the industry , a few examples of the binding agents that may be employed in the present invention are polyvinyl pyrrolidone , hydroxyethyl cellulose , hydroxypropyl cellulose , hydroxypropyl methylcellulose , polyacrylate , ethylcellulose , or mixtures of the foregoing . it is preferred that the binding agent be a water soluble or rapidly water dispersible material such as the low molecular weights polyvinyl pyrrolidone , hydroxpropyl methylcellulose and hydroxpropyl cellulose such as those described in european patent application no . 1588708a ( which correspondes to wo 04 / 067001 ) which is incorporated herein by reference . once the cores or immediate release pellets are prepared , a controlled release coating is applied to the cores or immediate release pellets . the controlled release coating preferably comprises a film forming compound such as a polymer and optionally conventional excipients such as a plasticizer and a channeling agent . the film forming polymer is preferably a water permeable , water insoluble polymer . some examples of the film forming polymer useful in the present invention are cellulose esters , cellulose dieters , cellulose triesters , cellulose ethers , cellulose ester - ether , cellulose acylate , cellulose diacylate , cellulose triacylate , cellulose acetate , cellulose diacetate , cellulose triacetate , cellulose acetate propionate , and cellulose acetate butyrate . other suitable polymers are described in u . s . pat . nos . 3 , 845 , 770 ; 3 , 916 , 899 ; 4 , 008 , 719 4 , 036 , 228 and 5 , 260 , 068 ; which are incorporated herein by reference . the most preferred film forming polymer is cellulose acetate comprising an acetyl content of 37 % to 42 %, which is commercially available from eastman fine chemicals . the controlled release coating may also comprise a plasticizer , which makes the extended release coating more flexible and aids in the release of the opiate from the core or immediate release pellet . some commonly known plasticizers include adipate , azelate , enzoate , citrate , stearate , isoebucate , sebacate , triethyl citrate , tri - n - butyl citrate , acetyl tri - n - butyl citrate , citric acid esters , and those described in the encyclopedia of polymer science and technology , vol . 10 ( 1969 ), published by john wiley & amp ; sons . other possible plasticizers include triacetin , acetylated monoglyceride , grape seed oil , olive oil , sesame oil , acetyltributylcitrate , acetyltriethylcitrate , glycerin sorbitol , diethyloxalate , diethylmalate , diethylfumarate , dibutylsuccinate , diethylmalonate , dioctylphthalate , dibutylsebacate , triethylcitrate , tributylcitrate , glyceroltributyrate , and the like . the preferred plasticizer are water soluble , such as acetyltributyl citrate . it may also be desirable for the controlled release coating to employ a channeling agent . a channeling agent is a material that increases the volume of fluid imbibed into the core to enable the extended release pellet to dispense substantially all of the opiate through the controlled release coating . the channeling agent may dissolve or leach from the controlled release coating to form paths in the coating for the fluid to enter the core and dissolve the opiate . the dissolved opiate is then released from the extended release pellets by movement through the channels formed in the controlled release coating by the dissolved or leached channeling agent . the channeling agent can be a water soluble material or an enteric material . some examples of the preferred materials that are useful as channeling agents are sodium chloride , potassium chloride , sucrose , sorbitol , mannitol , polyethylene glycol ( peg ), propylene glycol , poloxamer , hydroxypropyl cellulose , hydroxypropyl methycellulose , hydroxypropyl methycellulose phthalate , cellulose acetate phthalate , polyvinyl alcohols , methacrylic acid copolymers and mixtures thereof . the preferred channeling agent is peg 400 . the channeling agent may also be a drug that is water soluble . if the channeling agent is a drug , the dosage form has the added advantage of providing an immediate release of the drug that is selected as the channeling agent . the controlled release coating may also further comprise a lubricant such as talc , stearic acid , magnesium stearate , silicon dioxide , glyceryl monostearate , kaolin and sodium stearate . a particularly preferred lubricant is talc . in capsule formulation the pellets may be dusted with a lubricant before encapsulation , whereas during tabletting the lubricant is added before compression and / or during granulation of the material to be tabletted . the weight percentages of ingredients shown in table i below are based on a preferred embodiment of the present invention and the total weight of the core or immediate release pellet composition . table i ingredients ( core ) preferred most preferred inert seed 20 - 70 % 30 - 60 % opiate 10 - 60 % 15 - 45 % inorganic osmagent 1 - 30 % 2 - 20 % binder 0 - 30 % 1 - 20 % the weight percentages of the ingredients shown in table ii are based on a preferred embodiment of the present invention and are based upon the total dry weight of the extended release coating composition . table ii ingredients ( coating ) preferred most preferred film forming polymer 50 - 99 % 70 - 90 % plasticizer 0 - 40 % 1 - 35 % channeling agent 0 - 20 % 1 - 10 % lubricant 0 - 10 % 0 . 5 - 5 % a final dosage form prepared in accordance with the present invention may contain a homogeneous population of extended release pellets or a heterogeneous population of extended release pellets . as used herein a homogeneous population of extended release pellets refers to extended release pellets that employ a similar controlled release coating composition and thickness . as used herein a heterogeneous population of extended release pellets refers to two or more different types of extended release pellets wherein each type of extended release pellet employs a different amount of the controlled release coating ( i . e . thickness ) and / or a different controlled release coating composition such as a different film forming material or different amount of channeling agent . a method for preparing a heterogeneous population of extended release pellets is disclosed in u . s . pat . no . 6 , 524 , 620 ; which is incorporated herein by reference . an embodiment of the present invention will be a capsule of tablet that contains about 1 - 40 % ( preferably 2 - 20 %) of an immediate release form of the opiate , preferably in the form of immediate release pellets ; and about 60 - 98 % of extended release pellets . another embodiment of the present invention will be a capsule of tablet that contains about 1 - 30 % of an immediate release form of the opiate , preferably in the form of immediate release pellets ; about 30 - 90 % of a first population of extended release pellets that cause a plasma peak between 4 and 10 hours after administration and 30 - 90 % of a second population of extended release pellets that cause a plasma peak about 10 - 16 hours after administration . still another embodiment of the present invention will be a capsule of tablet that contains about 2 - 20 % of an immediate release form of the opiate , preferably in the form of immediate release pellets ; about 20 - 60 % of a first population of extended release pellets that exhibits a zero order rate of opiate release over a 24 hour time period and 20 - 60 % of a second population of extended release pellets that exhibits a lag time where little or no opiate is released , independent of ph of the environment of use , followed by a zero order rate of opiate release over a time period of about 2 to about 6 hours following the lag time . the lag time for the second population can be for a period of about 4 to about 14 hours , preferably about 6 to about 12 hours . the present invention will be further illustrated by the following examples . an extended release morphine sulphate capsule in accordance with the present invention is prepared as follows . step i drug solution morphine sulphate , sodium chloride and opadry ® clear are dissolved into a water solution . the solution is mixed for approximately 60 minutes . the suspension formed in step i above is spray coated onto 20 / 25 mesh sugar spheres using a fluidized bed coater under standard coating parameters to form immediate release pellets . a release controlling solution is formed by dissolving cellulose acetate , acetytributyl citrate and polyethylene glycol in acetone . a portion of the release controlling solution formed in step iii above is sprayed dried onto some of the immediate release pellets formed in step ii to form an extended release pellet that exhibits a zero order rate of opiate release over a 24 hours time period and which results in a plasma peak in about 4 to 10 hours after administration . a second portion of the release controlling solution prepared in step iii above is sprayed onto an additional sample of the immediate release pellets formed in step ii above to form an extended release pellet that exhibits a lag time of about 6 to about 12 hours after administration wherein no or substantially no opiate is released . the extended release lag time pellets will begin releasing the opiate after the lag time in a substantially zero order rate for a period of about 2 to about 6 hours resulting in a plasma peak of about 10 - 16 hours after administration . the immediate release and extended release pellets prepared above are dusted with talc and encapsulated utilizing equipment and guidelines commonly known in the art . final capsules are prepared comprising from about 2 - 20 % of the immediate release pellets formed from step ii ; from about 20 - 60 % of the extended release pellets from step iv and from about 10 - 50 % of the extended release pellets from step v . the composition of the final dosage form is report in table iii . table iii amount ingredients per unit morphine sulfate usp 120 . 0 sugar spheres , nf pg 20 / 25 160 . 0 opadry clear ( ys - 1 - 7006 ) 42 . 0 sodium chloride , usp 30 . 0 cellulose acetate , nf 398 - 10 34 . 5 acetyltributyl citrate , nf 5 . 8 polyethylene glycol 400 1 . 2 talc 20 . 7 purified water , usp * acetone , nf * total 414 . 1 * evaporated during processing . while certain preferred and alternative embodiments of the invention have been set forth for purposes of disclosing the invention , modifications to the disclosed embodiments may occur to those who are skilled in the art . accordingly , this specification is intended to cover all embodiments of the invention and modifications thereof which do not depart from the spirit and scope of the invention .
the present invention relates to an extended release opiate pellets that contain an opiate and an inorganic osmagent in the core . the extended release pellets can be used alone or combined with an immediate release opiate form to prepare extended release oral pharmaceutical tablets or capsules .