Sustained release formulations of oxymorphone or pharmaceutically acceptable salts thereof; methods for making the sustained release formulations of oxymorphone or pharmaceutically acceptable salts thereof; and methods for using the sustained release formulations of oxymorphone or pharmaceutically acceptable salts thereof to treat patients suffering from pain are provided.

SUMMARY OF THE INVENTION

The invention provides compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, where the sustained release delivery system comprises at least one hydrophilic compound, at least one cross-linking agent (which may be cationic) and at least one pharmaceutical diluent. The sustained release delivery system may further comprise one or more additional hydrophobic polymers or cross-linking compounds. The compositions may optionally comprise an outer coating comprising at least one water insoluble compound, and optionally one or more plasticizers and/or water soluble compounds.

The invention provides compositions comprising an inner core and an outer sustained release coating, where the inner core comprises oxymorphone or a pharmaceutically acceptable salt thereof and the outer sustained release coating comprises at least one water insoluble compound. The outer sustained release coating may optionally further comprise one or more plasticizers and/or water soluble compounds.

The invention provides methods for treating pain in patients by administering an effective amount of any of the compositions of the invention. The pain may be moderate to severe, and may be acute or chronic.

The invention also provides methods for making such compositions.

DETAILED DESCRIPTION OF THE INVENTION

To overcome the difficulties associated with the very low bioavailability of the oral immediate release formulation of oxymorphone and with a 4 hourly dosing frequency of oxymorphone, the invention provides an oral sustained release formulation of oxymorphone comprising an analgesically effective amount of oxymorphone or a pharmaceutically acceptable salt thereof. The bioavailability of the oral sustained release formulations of the invention is sufficiently high that the sustained release formulations can be used to treat patients suffering from pain with only once or twice daily dosing.

The invention provides compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, wherein the sustained release delivery system comprises (i) at least one hydrophilic compound, at least one cross-linking agent, and at least one pharmaceutical diluent; (ii) at least one hydrophilic compound, at least one cross-linking agent, at least one pharmaceutical diluent, and at least one hydrophobic polymer; (iii) at least one hydrophilic compound, at least one cross-linking agent, at least one pharmaceutical diluent, and at least one cationic cross-linking agent different from the first cross-linking agent; (iv) at least one hydrophilic compound, at least one cross-linking agent, at least one pharmaceutical diluent, at least one cationic cross-linking compound different from the first cross-linking agent, and at least one hydrophobic polymer; (v) at least one hydrophilic compound, at least one cationic cross-linking compound, and at least one pharmaceutical diluent; or (vi) at least one hydrophilic compound, at least one cationic cross-linking compound, at least one pharmaceutical diluent, and at least one hydrophobic compound.

The oxymorphone may be homogeneously dispersed in the sustained release delivery system. Preferably, the oxymorphone or pharmaceutically acceptable salt thereof may be present in the composition in an amount of about 1 mg to about 200 mg, more preferably in an amount of about 1 mg to about 100 mg, even more preferably in an amount of about 5 mg to about 80 mg. Preferably, the sustained release delivery system may be present in the composition in an amount from about 80 mg to about 420 mg, more preferably from about 80 mg to about 360 mg, even more preferably from about 80 mg to about 200 mg. "Oxymorphone" includes oxymorphone, metabolites thereof, derivatives thereof, and/or pharmaceutically acceptable salts thereof. Metabolites of oxymorphone include, for example, 6-hydroxy-oxymorphone (e.g., 6-.alpha.-hydroxy-oxymorphone and/or 6-.beta.-hydroxy-oxymorphone).

Oxymorphone may be in the form of any pharmaceutically acceptable salt known in the art. Exemplary pharmaceutically acceptable salts include hydrochloric, sulfuric, nitric, phosphoric, hydrobromic, maleric, malic, ascorbic, citric, tartaric, pamoic, lauric, stearic, palmitic, oleic, myristic, lauryl sulfuric, napthalinesulfonic, linoleic, linolenic acid, and the like. The hydrochloride salt of oxymorphone is preferred.

The sustained release delivery system comprises at least one hydrophilic compound. The hydrophilic compound preferably forms a gel matrix that releases the oxymorphone or the pharmaceutically acceptable salt thereof at a sustained rate upon exposure to liquids. The rate of release of the oxymorphone or the pharmaceutically acceptable salt thereof from the gel matrix depends on the drug's partition coefficient between the components of the gel matrix and the aqueous phase within the gastrointestinal tract. In the compositions of the invention, the weight ratio of oxymorphone to hydrophilic compound is generally in the range of about 1:0.5 to about 1:25, preferably in the range of about 1:0.5 to about 1:20. The sustained release delivery system generally comprises the hydrophilic compound in an amount of about 20% to about 80% by weight, preferably in an amount of about 20% to about 60% by weight, more preferably in an amount of about 40% to about 60% by weight, still more preferably in an amount of about 50% by weight.

The hydrophilic compound may be any known in the art. Exemplary hydrophilic compounds include gums, cellulose ethers, acrylic resins, polyvinyl pyrrolidone, protein-derived compounds, and mixtures thereof. Exemplary gums include heteropolysaccharide gums and homopolysaccharide gums, such as xanthan, tragacanth, pectins, acacia, karaya, alginates, agar, guar, hydroxypropyl guar, carrageenan, locust bean gums, and gellan gums. Exemplary cellulose ethers include hydroxyalkyl celluloses and carboxyalkyl celluloses. Preferred cellulose ethers include hydroxyethyl celluloses, hydroxypropyl celluloses, hydroxypropylmethyl-celluloses, carboxy methylcelluloses, and mixtures thereof. Exemplary acrylic resins include polymers and copolymers of acrylic acid, methacrylic acid, methyl acrylate and methyl methacrylate. In some embodiments, the hydrophilic compound is preferably a gum, more preferably a heteropolysaccharide gum, most preferably a xanthan gum or derivative thereof. Derivatives of xanthan gum include, for example, deacylated xanthan gum, the carboxymethyl esters of xanthan gum, and the propylene glycol esters of xanthan gum.

In another embodiment, the sustained release delivery system may further comprise at least one cross-linking agent. The cross-linking agent is preferably a compound that is capable of cross-linking the hydrophilic compound to form a gel matrix in the presence of liquids. As used herein, "liquids" includes, for example, gastrointestinal fluids and aqueous solutions, such as those used for in vitro dissolution testing. The sustained release delivery system generally comprises the cross-linking agent in an amount of about 0.5% to about 80% by weight, preferably in an amount of about 2% to about 54% by weight, more preferably in an amount of about 20% to about 30% by weight more, still more preferably in an amount of about 25% by weight.

Exemplary cross-linking agents include homopolysaccharides. Exemplary homopolysaccharides include galactomannan gums, such as guar gum, hydroxypropyl guar gum, and locust bean gum. In some embodiments, the cross-linking agent is preferably a locust bean gum or a guar gum. In other embodiments, the cross-linking agents may be alginic acid derivatives or hydrocolloids.

When the sustained release delivery system comprises at least one hydrophilic compound and at least one cross-linking agent, the ratio of hydrophilic compound to cross-linking agent may be from about 1:9 to about 9:1, preferably from about 1:3 to about 3:1.

The sustained release delivery system of the invention may comprise one or more cationic cross-linking compounds. Cationic cross-linking compound may be used instead of or in addition to the cross-linking agent. The cationic cross-linking compounds may be used in an amount sufficient to cross-link the hydrophilic compound to form a gel matrix in the presence of liquids. The cationic cross-linking compound is present in the sustained release delivery system in an amount of about 0.5% to about 30% by weight, preferably from about 5% to about 20% by weight.

Exemplary cationic cross-linking compounds include monovalent metal cations, multivalent metal cations, and inorganic salts, including alkali metal and/or alkaline earth metal sulfates, chlorides, borates, bromides, citrates, acetates, lactates, and mixtures thereof. For example, the cationic cross-linking compound may be one or more of calcium sulfate, sodium chloride, potassium sulfate, sodium carbonate, lithium chloride, tripotassium phosphate, sodium borate, potassium bromide, potassium fluoride, sodium bicarbonate, calcium chloride, magnesium chloride, sodium citrate, sodium acetate, calcium lactate, magnesium sulfate, sodium fluoride, or mixtures thereof.

When the sustained release delivery system comprises at least one hydrophilic compound and at least one cationic cross-linking compound, the ratio of hydrophilic compound to cationic cross-linking compound may be from about 1:9 to about 9:1, preferably from about 1:3 to about 3:1.

Two properties of desirable components of this system (e.g., the at least one hydrophilic compound and the at least one cross-linking agent; or the at least one hydrophilic compound and at least one cationic cross-linking compound) that form a gel matrix upon exposure to liquids are fast hydration of the compounds/agents and the ability to form a gel matrix having a high gel strength. These two properties, which are needed to achieve a slow release gel matrix, are maximized in the invention by the particular combination of compounds (e.g., the at least one hydrophilic compound and the at least one cross-linking agent; or the at least one hydrophilic compound and the at least one cationic cross-linking compound). For example, hydrophilic compounds (e.g., xanthan gum) have excellent water-wicking properties which provide fast hydration. The combination of hydrophilic compounds with materials that are capable of cross-linking the rigid helical ordered structure of the hydrophilic compound (e.g., cross-linking agents and/or cationic cross-linking compounds) thereby act synergistically to provide a higher than expected viscosity (i.e., high gel strength) of the gel matrix.

The sustained release delivery system further comprises one or more pharmaceutical diluents known in the art. Exemplary pharmaceutical diluents include monosaccharides, disaccharides, polyhydric alcohols and mixtures thereof. Preferred pharmaceutical diluents include, for example, starch, lactose, dextrose, sucrose, microcrystalline cellulose, sorbitol, xylitol, fructose, and mixtures thereof. In other embodiments, the pharmaceutical diluent is water-soluble, such as lactose, dextrose, sucrose, or mixtures thereof. The ratio of pharmaceutical diluent to hydrophilic compound is generally from about 1:8 to about 8:1, preferably from about 1:3 to about 3:1. The sustained release delivery system generally comprises one or more pharmaceutical diluents in an amount of about 20% to about 80% by weight, preferably about 35% by weight. In other embodiments, the sustained release delivery system comprises one or more pharmaceutical diluents in an amount of about 40% to about 80% by weight.

The sustained release delivery system of the invention may comprise one or more hydrophobic polymers. The hydrophobic polymers may be used in an amount sufficient to slow the hydration of the hydrophilic compound without disrupting it. For example, the hydrophobic polymer may be present in the sustained release delivery system in an amount of about 0.5% to about 20% by weight, preferably in an amount of about 2% to about 10% by weight, more preferably in an amount of about 3% to about 7% by weight, still more preferably in an amount of about 5% by weight.

Exemplary hydrophobic polymers include alkyl celluloses (e.g., C.sub.1-6 alkyl celluloses, carboxymethylcellulose), other hydrophobic cellulosic materials or compounds (e.g., cellulose acetate phthalate, hydroxypropylmethylcellulose phthalate), polyvinyl acetate polymers (e.g., polyvinyl acetate phthalate), polymers or copolymers derived from acrylic and/or methacrylic acid esters, zein, waxes, shellac, hydrogenated vegetable oils, and mixtures thereof. The hydrophobic polymer is preferably methyl cellulose, ethyl cellulose or propyl cellulose, more preferably ethyl cellulose.

The compositions of the invention may be further admixed with one or more wetting agents (such as polyethoxylated castor oil, polyethoxylated hydrogenated castor oil, polyethoxylated fatty acid from castor oil, polyethoxylated fatty acid from hydrogenated castor oil) one or more lubricants (such as magnesium stearate, sodium stearyl fumarate, and the like), one or more buffering agents, one or more colorants, and/or other conventional ingredients.

In other embodiments, the invention provides oral sustained release solid dosage formulations comprising from about 1 mg to 200 mg oxymorphone hydrochloride, preferably from about 5 mg to about 80 mg oxymorphone hydrochloride; and about 80 mg to about 200 mg of a sustained release delivery system, preferably from about 120 mg to about 200 mg of a sustained release delivery system, more preferably about 160 mg of a sustained release delivery system; where the sustained release delivery system comprises about 8.3 to about 41.7% locust bean gum, preferably about 25% locust bean gum; about 8.3 to about 41.7% xanthan gum, preferably about 25% xanthan gum; about 20 to about 55% dextrose, preferably about 35% dextrose; about 5 to about 20% calcium sulfate dihydrate, preferably about 10% calcium sulfate dihydrate; and about 2 to 10% ethyl cellulose, preferably about 5% ethyl cellulose.

In other embodiments, the invention provides oral sustained release solid dosage formulations comprising from about 1 mg to 200 mg oxymorphone hydrochloride, preferably from about 5 mg to about 80 mg oxymorphone hydrochloride; and about 200 mg to about 420 mg of a sustained release delivery system, preferably from about 300 mg to about 420 mg of a sustained release delivery system, more preferably about 360 mg of a sustained release delivery system; where the sustained release delivery system comprises about 8.3 to about 41.7% locust bean gum, preferably about 25% locust bean gum; about 8.3 to about 41.7% xanthan gum, preferably about 25% xanthan gum; about 20 to about 55% dextrose, preferably about 35% dextrose; about 5 to about 20% calcium sulfate dihydrate, preferably about 10% calcium sulfate dihydrate; and about 2 to 10% ethyl cellulose, preferably about 5% ethyl cellulose.

The sustained release formulations of oxymorphone are preferably orally administrable solid dosage formulations which may be, for example, tablets, capsules comprising a plurality of granules, sublingual tablets, powders, or granules; preferably tablets. The tablets may be an enteric coating or a hydrophilic coating.

The sustained release delivery system in the compositions of the invention may be prepared by dry granulation or wet granulation, before the oxymorphone or pharmaceutically acceptable salt thereof is added, although the components may be held together by an agglomeration technique to produce an acceptable product. In the wet granulation technique, the components (e.g., hydrophilic compounds, cross-linking agents, pharmaceutical diluents, cationic cross-linking compounds, hydrophobic polymers, etc.) are mixed together and then moistened with one or more liquids (e.g., water, propylene glycol, glycerol, alcohol) to produce a moistened mass which is subsequently dried. The dried mass is then milled with conventional equipment into granules of the sustained release delivery system. Thereafter, the sustained release delivery system is mixed in the desired amounts with the oxymorphone or the pharmaceutically acceptable salt thereof and, optionally, one or more wetting agents, one or more lubricants, one or more buffering agents, one or more coloring agents, or other conventional ingredients, to produce a granulated composition. The sustained release delivery system and the oxymorphone may be blended with, for example, a high shear mixer. The oxymorphone is preferably finely and homogeneously dispersed in the sustained release delivery system. The granulated composition, in an amount sufficient to make a uniform batch of tablets, is subjected to tableting in a conventional production scale tableting machine at normal compression pressures, i.e., about 2,000-16,000 psi. The mixture should not be compressed to a point where there is subsequent difficulty with hydration upon exposure to liquids.

The average particle size of the granulated composition is from about 50 .mu.m to about 400 .mu.m, preferably from about 185 .mu.m to about 265 .mu.m. The average density of the granulated composition is from about 0.3 g/ml to about 0.8 g/ml, preferably from about 0.5 g/ml to about 0.7 g/ml. The tablets formed from the granulations are generally from about 6 to about 8 kg hardness. The average flow of the granulations are from about 25 to about 40 g/sec.

In other embodiments, the invention provides sustained release coatings over an inner core comprising oxymorphone or a pharmaceutically acceptable salt thereof. For example, the inner core comprising oxymorphone or a pharmaceutically acceptable salt thereof may be coated with a sustained release film which, upon exposure to liquids, releases the oxymorphone or the pharmaceutically acceptable salt thereof from the core at a sustained rate.

In one embodiment, the sustained release coating comprises at least one water insoluble compound. The water insoluble compound is preferably a hydrophobic polymer. The hydrophobic polymer may be the same as or different from the hydrophobic polymer used in the sustained release delivery system. Exemplary hydrophobic polymers include alkyl celluloses (e.g., C.sub.1-6 alkyl celluloses, carboxymethylcellulose), other hydrophobic cellulosic materials or compounds (e.g., cellulose acetate phthalate, hydroxypropylmethylcellulose phthalate), polyvinyl acetate polymers (e.g., polyvinyl acetate phthalate), polymers or copolymers derived from acrylic and/or methacrylic acid esters, zein, waxes (alone or in admixture with fatty alcohols), shellac, hydrogenated vegetable oils, and mixtures thereof. The hydrophobic polymer is preferably, methyl cellulose, ethyl cellulose or propyl cellulose, more preferably ethyl cellulose. The sustained release formulations of the invention may be coated with a water insoluble compound to a weight gain from about 1 to about 20% by weight.

The sustained release coating may further comprise at least one plasticizer such as triethyl citrate, dibutyl phthalate, propylene glycol, polyethylene glycol, or mixtures thereof.

The sustained release coating may also contain at least one water soluble compound, such as polyvinylpyrrolidones, hydroxypropylmethylcelluloses, or mixtures thereof. The sustained release coating may comprise at least one water soluble compound in an amount from about 1% to about 6% by weight, preferably in an amount of about 3% by weight.

The sustained release coating may be applied to the oxymorphone core by spraying an aqueous dispersion of the water insoluble compound onto the oxymorphone core. The oxymorphone core may be a granulated composition made, for example, by dry or wet granulation of mixed powders of oxymorphone and at least one binding agent; by coating an inert bead with oxymorphone and at least one binding agent; or by spheronizing mixed powders of oxymorphone and at least one spheronizing agent. Exemplary binding agents include hydroxypropylmethylcelluloses. Exemplary spheronizing agents include microcrystalline celluloses. The inner core may be a tablet made by compressing the granules or by compressing a powder comprising oxymorphone or the pharmaceutically acceptable salt thereof.

In other embodiments, the compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, as described herein, are coated with a sustained release coating, as described herein. In still other embodiments, the compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, as described herein, are coated with a hydrophobic polymer, as described herein. In still other embodiments, the compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, as described herein, are coated with an enteric coating, such as cellulose acetate phthalate, hydroxypropylmethylcellulose phthalate, polyvinylacetate phthalate, methacrylic acid copolymer, shellac, hydroxypropylmethylcellulose succinate, cellulose acetate trimelliate, or mixtures thereof. In still other embodiments, the compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, as described herein, are coated with a hydrophobic polymer, as described herein, and further coated with an enteric coating, as described herein. In any of the embodiments described herein, the compositions comprising oxymorphone or a pharmaceutically acceptable salt thereof and a sustained release delivery system, as described herein, may optionally be coated with a hydrophilic coating which may be applied above or beneath the sustained release film, above or beneath the hydrophobic coating, and/or above or beneath the enteric coating. Preferred hydrophilic coatings comprise hydroxypropylmethylcellulose.

The invention provides methods for treating pain by administering an effective amount of the sustained release formulations of oxymorphone to a patient in need thereof. An effective amount is an amount sufficient to eliminate all pain or to alleviate the pain (i.e., reduce the pain compared to the pain present prior to administration of the oxymorphone sustained release formulation). "Sustained release" means that the oxymorphone or pharmaceutically acceptable salt thereof is released from the formulation at a controlled rate so that therapeutically beneficial blood levels (but below toxic levels) of the oxymorphone or pharmaceutically acceptable salt thereof are maintained over an extended period of time. The sustained release formulations of oxymorphone are administered in an amount sufficient to alleviate pain for an extended period of time, preferably about 8 hours to about 24 hours, more preferably for a period of about 12 hours to about 24 hours. The oxymorphone sustained release oral solid dosage formulations of the invention may be administered one to four times a day, preferably once or twice daily, more preferably once daily. The pain may be minor to moderate to severe, and is preferably moderate to severe. The pain may be acute or chronic. The pain may be associated with, for example, cancer, autoimmune diseases, infections, surgical traumas, accidental traumas or osteoarthritis. The patient may be an animal, preferably a mammal, more preferably a human.

In certain embodiments, upon oral ingestion of the oxymorphone sustained release formulation and contact of the formulation with gastrointestinal fluids, the sustained release formulation swells and gels to form a hydrophilic gel matrix from which the oxymorphone is released. The swelling of the gel matrix causes a reduction in the bulk density of the formulation and provides the buoyancy necessary to allow the gel matrix to float on the stomach contents to provide a slow delivery of the oxymorphone. The hydrophilic matrix, the size of which is dependent upon the size of the original formulation, can swell considerably and become obstructed near the opening of the pylorus. Since the oxymorphone is dispersed throughout the formulation (and consequently throughout the gel matrix), a constant amount of oxymorphone can be released per unit time in vivo by dispersion or erosion of the outer portions of the hydrophilic gel matrix. The process continues, with the gel matrix remaining bouyant in the stomach, until substantially all of the oxymorphone is released.

In certain embodiments, the chemistry of certain of the components of the formulation, such as the hydrophilic compound (e.g., xanthan gum), is such that the components are considered to be self-buffering agents which are substantially insensitive to the solubility of the oxymorphone and the pH changes along the length of the gastrointestinal tract. Moreover, the chemistry of the components is believed to be similar to certain known muco-adhesive substances, such as polycarbophil. Muco-adhesive properties are desirable for buccal delivery systems. Thus, the sustained release formulation can loosely interact with the mucin in the gastrointestinal tract and thereby provide another mode by which a constant rate of delivery of the oxymorphone is achieved.

The two phenomenon discussed above (buoyancy and muco-adhesive properties) are mechanisms by which the sustained release formulations of the invention can interact with the mucin and fluids of the gastrointestinal tract and provide a constant rate of delivery of the oxymorphone.

When measured by USP Procedure Drug Release USP 23 (incorporated by reference herein in its entirety), the sustained release formulations of the invention exhibit an in vitro dissolution rate of about 15% to about 50% by weight oxymorphone after 1 hour, about 45% to about 80% by weight oxymorphone after 4 hours, and at least about 80% by weight oxymorphone after 10 hours. The in vitro and in vivo release characteristics of the sustained release formulations of the invention may be modified using mixtures of one or more different water insoluble and/or water soluble compounds, using different plasticizers, varying the thickness of the sustained release film, including providing release-modifying compounds in the coating, and/or by providing passageways through the coating.

When administered orally to patients the sustained release formulations of the invention exhibit the following in vivo characteristics: (a) a peak plasma level of oxymorphone occurs within about 2 to about 6 hours after administration; (b) the duration of the oxymorphone analgesic effect is about 8 to about 24 hours; and (c) the relative oxymorphone bioavailability is about 0.5 to about 1.5 compared to an orally administered aqueous solution of oxymorphone.

While the compositions of the invention may be administered as the sole active pharmaceutical compound in the methods described herein, they can also be used in combination with one or more compounds which are known to be therapeutically effective against pain.

The invention also provides pharmaceutical kits comprising one or more containers filled with one or more of the compositions of the invention. The kits may further comprise other pharmaceutical compounds known in the art to be therapeutically effective against pain, and instructions for use.
 

Claim 1 of 16 Claims

1. An oral sustained release formulation comprising from about 5 mg to about 80 mg oxymorphone hydrochloride and from about 80 mg to about 360 mg of a granulated sustained release delivery system, wherein the granulated sustained release delivery system comprises from about 8.3% to about 41.7% by weight locust bean gum, from about 8.3% to about 41.7% by weight xanthan gum, from about 20% to about 55% by weight dextrose, from about 5% to about 20% by weight calcium sulfate dihydrate, and from about 2% to about 10% ethyl cellulose.

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.