AU2012200480B2 - "Aliphatic amine polymer salts for tableting" - Google Patents

Abstract

C :WRPonblDCC\RXSlA 1476 1_.DOC-25/01/2012 The tablets, compositions and methods of the present invention, comprising a carbonate salt of an aliphatic amine polymer and s monovalent anion can prevent or ameliorate acidosis, in particular acidosis in patients with renal disease. The tablets and compositions of the present invention maintain a disintegration time of no greater than 30 minutes at 37*C and at pH of at least I for a period of at least ten weeks at 60 'C. Furthermore, the tablets are stable for extended periods of time without the need for specialized storage conditions.

Description

Australian Patents Act 1990 - Regulation 3.2A ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title "Aliphatic amine polymer salts for tableting" The following statement is a full description of this invention, including the best method of performing it known to us:- C:WRPonbRlDCC\RXSi 47611 DOC-25 011/2012 ALIPHATIC AMINE POLYMER SALTS FOR TABLETING This is a divisional of Australian Patent Application No. 2005302243, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION Hyperphosphatemia frequently accompanies diseases associated with inadequate renal function, hyperparathyroidism, and certain other medical conditions. Hyperphosphatemia is typically defined for humans as a serum phosphate level of greater than about 4.5 mg/dL. The condition, especially if present over extended periods of time, leads to severe abnormalities in calcium and phosphorus metabolism and can be manifested by aberrant calcification in joints, lungs and eyes. Anion exchange polymers, such as aliphatic amine polymers, have been used in the treatment of hyperphosphatemia. These polymers provide an effective treatment for decreasing the serum level of phosphate, without concomitantly increasing the absorption of any clinically undesirable materials. Metabolic acidosis is another condition which accompanies diseases associated with inadequate renal function. The human body is constantly gaining H+ ions from the metabolism of sugars, fats, protein and lactic acid (produced under anaerobic metabolism). To maintain a constant pH the body must excrete H+ ions. Decreased excretion of H* ions occurs in patients suffering from renal disease or renal failure, which results in metabolic acidosis and, hence, a low blood pH due to excess H* ions.

-2 Current treatments for hyperphosphatemia do not address the issue of metabolic acidosis. The present inventors have prepared carbonate salts of aliphatic amine polymers for this purpose, however, tablets made from carbonate salts of aliphatic amine polymers suffer from short shelf life. Further, the disintegration 5 time of tablets made from carbonate salts increases over time when stored under standard storage conditions. This increase in disintegration time may lead to decreased availability of the active components of the drug to a patient. SUMMARY OF THE INVENTION 10 It has now been found that adding a monovalent anion source to tablets of aliphatic amine carbonates salts significantly increases the shelf life, and prevents the disintegration time from increasing over time when the tablets are stored under standard storage conditions. Further it has been found that increasing the particle size of the aliphatic amine polymer particles in the tablets significantly increases the 15 shelf life, and prevents the disintegration time from increasing over time when the tablets are stored under standard storage conditions. In one embodiment, the present invention is a tablet comprising a carbonate, bicarbonate, acetate or lactate salt of an aliphatic amine polymer, wherein said tablet maintains a disintegration time of no greater than 30 minutes at 37*C and at a pH of 20 at least 1 when stored for a period of at least ten weeks at 60 *C. Preferably the aliphatic amine polymer is sevelamer. In another embodiment the present invention is a tablet comprising a carbonate, bicarbonate, acetate or lactate salt of an aliphatic amine polymer and a monovalent anion source, wherein the monovalent anion comprises at least 0.05% 25 by weight of the combined weights of the carbonate salt and the monovalent anion source. In another embodiment, the present invention is a composition comprising a carbonate, bicarbonate, acetate or lactate salt of an aliphatic amine polymer and a monovalent anion source, wherein the monovalent anion comprises at least 0.05% 30 by weight of the combined weight of the carbonate salt and the monovalent anion source. Preferably the composition is for pharmaceutical use and additionally comprises a pharmaceutically acceptable carrier or diluent.

-3 In another embodiment the present invention is a tablet comprising sevelamer carbonate particles, wherein at least 95% by volume of the particles have a diameter of at least 45 microns. In one embodiment the present invention is a method of removing phosphate 5 from a patient in need of such treatment, comprising administering to the patient a therapeutically effective amount of a tablet, composition or pharmaceutical composition disclosed herein. The tablets, compositions and methods of the present invention, can prevent or ameliorate acidosis, in particular acidosis in patients with renal disease. The 10 disintegration time of the tablets and compositions of the present invention does not increase over time when stored under standard conditions. Furthermore, the tablets are stable for extended periods of time without the need for specialized storage conditions. 15 DETAILED DESCRIPTION OF THE INVENTION Current treatments for hyperphosphatemia do not address the issues of low blood pH which often accompanies renal failure. The use of carbonate salts of aliphatic amine polymers would be useful in addressing this issue, however, tablets of carbonate salts often suffer from short shelf lives and disintegration times which 20 increase over time under standard storage conditions. It has now been discovered that adding a monovalent anion source to the carbonate salt prevents the increase in the disintegration time of the tablets and increases the shelf life. It has also been discovered that increasing the particle size of the aliphatic amine polymer prevents the increase in the disintegration time of the tablets and increases the shelf life. 25 In one embodiment the present invention is a tablet comprising a carbonate, bicarbonate, acetate or lactate salt of an aliphatic amine polymer, wherein said tablet maintains a disintegration time of no greater than 60 minutes, 45 minutes, 30 minutes, preferably 20 minutes, more preferably 15 minutes, most preferably 10 minutes at 37 ± 2*C. The disclosed tablets exhibit these disintegration times over a 30 wide variety of pH ranges including acidic conditions such as a pH of at least 1, more preferably at a pH range of 1-5, preferably 1-4, more preferably 1-3, most preferably 1-2, even more preferably at pH 1.2. The disintegration time can be -4 measured using the procedures described in the United States Pharmacopoeia 27 National Formulary 22 (USP 27 - NF 22) which have been adapted according to Example 1. In a preferred embodiment the disintegration time of the tablets remains constant for a period of at least 1 week, 2 weeks, 1 month, 5 weeks, 2 months, 10 5 weeks, 3 months, 6 months, 1 year, or two years at 60 *C when stored in a sealed, water impervious container. It is to be understood when speaking herein of carbonate salts Applicants' are also referring to bicarbonate, acetate, and lactate salts. Amine polymers are characterized by a repeat unit that includes at least one 10 amino group. Amino groups can be part of the polymer backbone (e.g., a polyalkyleneimine such as polyethyleneimine), pendant from the polymer backbone (e.g., polyallylamine), or both types of amino groups can exist within the same repeat unit and/or polymer. Amine polymers include aliphatic amine polymers and aromatic amine polymers. 15 An aliphatic amine polymer is obtained by polymerizing an aliphatic amine monomer. An aliphatic amine is saturated or unsaturated, straight-chained, branched or cyclic non-aromatic hydrocarbon having an amino substituent and optionally one or more additional substituents. An aliphatic amine monomer is an aliphatic amine comprising a polymerizable group such as an olefin. Examples of aliphatic amine 20 polymers include polymers characterized by one or more repeat units set forth below:

(CH

2 )y -N 4R2 -5

R

1

X

(CH

2 ) -N - R 3

R

2 5 III IV 10

V

-6 X~ R1

R

2 VI R VII

X

R1 N+ R2 5 VIII wherein y is an integer of zero, one or more (e.g., between about 1 and 10, 1 and 6, 1 and 4 or 1 and 3) and each R, R 1 , R 2 , and R 3 , independently, is H or a substituted or 10 unsubstituted alkyl group (e.g., having between 1 and 25, preferably between 1 and 5 carbon atoms, such as aminoalkyl having e.g., between 1 and 5 carbons atoms, inclusive, such as aminoethyl or poly(aminoethyl)) or substituted or unsubstituted aryl (e.g., phenyl) group, and each X- is independently an exchangeable negatively charged counterion. Typically, R, R 1 , R 2 , and R 3 are each independently H or a 15 substituted or unsubstituted alkyl group. In one preferred polymer used in the invention, at least one of the R, R 1 , R 2 , or R 3 groups is a hydrogen atom. In a more preferred embodiment, each of these groups are hydrogen. In one embodiment, R, R 1 , R 2 , and R 3 are H and the polymer comprises repeat units characterized by Structural Formulas I-IV, VII and/or VIII. 20 As an alkyl, or aryl group, R, R 1 , R 2 , or R 3 can carry one or more substituents. Suitable substituents include cationic groups, e.g., quaternary -7 ammonium groups, or amine groups, e.g., primary, secondary or tertiary alkyl or aryl amines. Examples of other suitable substituents include hydroxy, alkoxy, carboxamide, sulfonamide, halogen, alkyl, aryl, hydrazine, guanadine, urea, poly(alkyleneimine), such as poly(ethyleneimine), and carboxylic acid esters. 5 One example of a preferred aliphatic amine polymer is characterized by one or more repeat units of Structural Formula IX: H2_H - C -C4

(CH

2 )x IX 10 or a pharmaceutically acceptable salt thereof, where x is 0 or an integer between 1 and 4, preferably 1. The polymer represented by Structural Formula IX is advantageously crosslinked by means of a multifunctional cross-linking agent. Another preferred polymer for use in the invention is polyallylamine, which is a polymer having repeat units from polymerized allyl amine monomers. The 15 amine group of an allyl monomer can be unsubstituted or substituted with, for example, one or two C1 -C10 straight chain or branched alkyl groups. The alkyl groups are optionally substituted with one or more hydroxyl, amine, halo, phenyl, amide or nitrile groups. Preferably, the polyallylamine polymers of the present invention comprise repeat units represented by Structural Formula X: 20

H

2 N

X

-8 An amine polymer can be a homopolymer or a copolymer of one or more amine-containing monomers or a copolymer of one or more amine-containing monomers in combination with one or more different amine containing monomer or non-amine containing monomers. Copolymers that include one or more repeat units 5 represented by the above Structural Formulas I-X, contain comonomers that are preferably inert and non-toxic. Examples of suitable non-amine-containing monomers include vinyl alcohol, acrylic acid, acrylamide, and vinylformamide. Also polyallylamine can be a copolymer comprising repeat units from two or more different polymerized allyl monomers or with repeat units from one or more 10 polymerized allyl monomers and repeat units from one or more polymerized non allyl monomers. Examples of suitable non-allyl monomers include acrylamide monomers, acrylate monomers, maleic acid, malimide monomers, vinyl acylate monomers and alkyl substituted olefines. Preferably, however, the polyallylamines used in the present invention comprise repeat units solely from polymerized allyl 15 amine monomers. More preferably, the polyallylamine polymers used in the present invention are homopolymers. Even more preferably, the polyallylamine polymers used in the present invention are homopolymers of repeat units represented by Structural Formula X or are crosslinked homopolymers thereof. Preferably, an aliphatic amine polymer is a homopolymer, such as a 20 homopolyallylamine, homopolyvinylamine, homopolydiallylamine or polyethyleneamine. The word "amine," as used herein, includes primary, secondary and tertiary amines, as well as ammonium groups such as trialkylammonium. Aromatic amine polymers comprise an amine-containing aromatic moiety in one or more of the repeat units. An example of an aromatic amine polymer is 25 poly(aminostyrene). Amine polymers used in the invention protonated with H 2 C0 3 or HC0 3 . Preferably, less than 40%, less than 30%, less than 20% or less than 10% of the amine groups are protonated. In another embodiment 10% to 70%, 20% to 60%, 30 to 50% or 35% to 45% of the amines are protonated (e.g., approximately 40%), such 30 as Renagele which is commercially available from Genzyme Corporation. The preferred polymers employed in the invention are water-insoluble, non absorbable, optionally cross-linked polyamines. Preferred polymers are aliphatic.

-9 Examples of preferred polymers include polyethyleneimine, polyallylamine, polyvinylamine and polydiallylamine polymers. The polymers can be homopolymers or copolymers, as discussed above, and can be substituted or unsubstituted. These and other polymers which can be used in the claimed invention 5 have been disclosed in United States Patents Nos. 5,487,888; 5,496,545; 5,607,669; 5,618,530; 5,624,963; 5,667,775; 5,679,717; 5,703,188; 5,702,696; 5,693,675; 5,900,475; 5,925,379; 6,083,497; 6,177,478; 6,083,495; 6,203,785; 6,423,754; 6,509,013; 6,556,407; 6,605,270; and 6,733,780 the contents of which are hereby incorporated herein by reference in their entireties. Polymers suitable for use in the 10 invention are also disclosed in U.S. Application Nos. 08/823,699 (now abandoned); 08/835,857 (now abandoned); 08/470,940 (now abandoned); 08/927,247 (now abandoned); 08/964,498; 09/691,429; 10/125,684; 10/158,207; 10/322,904; 10/441,157; and 10/766,638, the contents of which are incorporated herein by reference in their entireties. 15 Preferably, the polymer is rendered water-insoluble by cross-linking such as with a multifunctional cross-linking agent. The cross-linking agent is typically characterized by functional groups which react with the amino group of the monomer. Alternatively, the cross-linking agent can be characterized by two or more vinyl groups which undergo free radical polymerization with the amine 20 monomer. The degree of polymerization in cross-linked polymers cannot generally be determined. Examples of suitable multifunctional cross-linking agents include diacrylates and dimethylacrylates (e.g. ethylene glycol diacrylate, propylene glycol diacrylate, butylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol 25 dimethacrylate, butylene glycol dimethacrylate, polyethyleneglycol dimethacrylate and polyethyleneglycol diacrylate), methylene bisacrylamide, methylene bismethacrylamide, ethylene bisacrylamide, ethylene bismethacrylamide, ethylidene bisacrylamide, divinylbenzene, bisphenol A, dimethacrylate and bisphenol A diacrylate. The cross-linking agent can also include acryloyl chloride, 30 epichlorohydrin, butanediol diglycidyl ether, ethanediol diglycidyl ether, succinyl dichloride, the diglycidal ether of bisphenol A, pyromellitic dianhydride, toluene diisocyanate, ethylene diamine and dimethyl succinate.

-10 The level of cross-linking renders the polymers insoluble and substantially resistant to absorption and degradation, thereby limiting the activity of the polymer to the gastrointestinal tract, and reducing potential side-effects in the patient. The compositions thus tend to be non-systemic in activity. Typically, the cross-linking 5 agent is present in an amount from about 0.5-35% or about 0.5-25% (such as from about 2.5-20% or about 1-10%) by weight, based upon total weight of monomer plus cross-linking agent. In some cases the polymers are crosslinked after polymerization. One method of obtaining such crosslinking involves reaction of the polymer with 10 difunctional crosslinkers, such as epichlorohydrin, succinyl dichloride, the diglycidyl ether of bisphenol A, pyromellitic dianhydride, toluence diisocyanate, and ethylenediamine. A typical example is the reaction of poly(ethyleneimine) with epichlorohydrin. In this example the epichlorohydrin (1 to 100 parts) is added to a solution containing polyethyleneimine (100 parts) and heated to promote reaction. 15 Other methods of inducing crosslinking on already polymerized materials include, but are not limited to, exposure to ionizing radiation, ultraviolet radiation, electron beams, radicals, and pyrolysis. Examples of preferred crosslinking agents include epichlorohydrin, 1,4 butanedioldiglycidyl ether, 1,2 ethanedioldiglycidyl ether, 1,3-dichloropropane, 1,2 20 dichloroethane, 1,3-dibromopropane, 1,2-dibromoethane, succinyl dichloride, dimethylsuccinate, toluene diisocyanate, acryloyl chloride, and pyromellitic dianhydride. Epichlorohydrin is a preferred crosslinking agent, because of its high availability and low cost. Epichlorohydrin is also advantageous because of its low molecular weight and hydrophilic nature, increasing the water-swellability and gel 25 properties of the polyamine. Epichlorohydrin forms 2-hydroxypropyl crosslinking groups. In a preferred embodiment, the present invention is a polyallylamine polymer crosslinked with epichlorohydrin. Typically, between about 9% and about 30% of the allylic nitrogen atoms are bonded to a crosslinking group, preferably between 15% and about 21%. 30 In a preferred embodiment, the polyallylamine polymer used in the present invention is polyallylamine crosslinked with about 9.0-9.8% w/w epichlorohydrin, - 11 preferably 9.3-9.5% which is known as sevelamer. The structure is represented below: H2N H a OH H2N NH 5 XI where: the sum of a and b (the number of primary amine groups) is 9; c (the number of crosslinking groups) is 1; n (the fraction of protonated amines) is 0.4; and 10 m is a large number (to indicate extended polymer network). Typically, the amount of epichlorohydrin is measured as a percentage of the combined weight of polymer and crosslinking agent. The polymers can also be further derivatized; examples include alkylated amine polymers, as described, for example, in United States Patent Nos. 5,679,717, 15 5,607,669 and 5,618,530, the teachings of which are incorporated herein by reference in their entireties. Preferred alkylating agents include hydrophobic groups (such as aliphatic hydrophobic groups) and/or quaternary ammonium- or amine substituted alkyl groups. Non-cross-linked and cross-linked polyallylamine and polyvinylamine are 20 generally known in the art and are commercially available. Methods for the - 12 manufacture of polyallylamine and polyvinylamine, and cross-linked derivatives thereof, are described in the above U.S. Patents. Patents by Harada et al. (U.S. Patent Nos. 4,605,701 and 4,528,347), which are incorporated herein by reference in their entireties, also describe methods of manufacturing polyallylamine and cross 5 linked polyallylamine. A patent by Stutts et al. (U.S. Patent No. 6,180,754) describes an additional method of manufacturing cross-linked polyallylamine. In other embodiments, the polymer can be a homopolymer or copolymer of polybutenylamine, polylysine, or polyarginine. Alternatively, the polymer can be an aromatic polymer, such as an amine or ammonium-substituted polystyrene, (e.g., 10 cholestyramine). The molecular weight of polymers of the invention is not believed to be critical, provided that the molecular weight is large enough so that the polymer is non-absorbable by the gastrointestinal tract. Typically the molecular weight is at least 1000. For example the molecular weight can be from: about 1000 to about 5 15 million, about 1000 to about 3 million, about 1000 to about 2 million or about 1000 to about 1 million. As described above, the polymers are protonated and are administered in the form of a salt. By "salt" it is meant that the nitrogen group in the repeat unit is protonated to create a positively charged nitrogen atom associated with a negatively 20 charged counterion. Preferably, the salt is a weak acidic salt such as carbonate, bicarbonate, acetate or lactate. In one embodiment the present invention is a tablet or composition comprising a carbonate salt of an aliphatic amine polymer and a monovalent anion source, wherein the monovalent anion comprises at least 0.01%, preferably 0.05%, 25 more preferably a range of 0.01% to 2%, 0.05% to 1%, 0.08 % to 0.5%, or 0.1% to 0.3% by weight of the combined weights of the carbonate salt and the monovalent anion source. The monovalent anion is selected to minimize adverse effects on the patient. Examples of suitable anions include organic ions, inorganic ions, or a combination 30 thereof, such as halides (Cr, T, Fl and Br), CH 3 0SO3~, HS0 4 , acetate, lactate, butyrate, propionate, sulphate, citrate, tartrate, nitrate, sulfonate, oxalate, succinate - 13 or palmoate. Preferred anions are halides, most preferably chloride. The monovalent anion is other than HC0 3 . In one embodiment, the monovalent anion source is a pharmaceutically acceptable acid, ammonium or metal salt of a monovalent anion. For example, 5 monovalent anion source can be a lithium, sodium, potassium, magnesium, calcium, aluminium, lanthanide, or actinide salt of a monovalent anion. The monovalent anion source can be ammonium, a mono, di, tri or tetra alkylated ammonium. Any of the above described monovalent anions can be combined with any of the metals listed above, of with H*. Preferably the monovalent anion source is sodium chloride 10 or hydrochloric acid. In one embodiment, the tablet or composition comprises a carbonate salt of sevelamer and sodium chloride. In one preferred embodiment, the tablet or composition comprises a carbonate salt of sevelamer and sodium chloride powder. In another preferred embodiment, the tablet or composition comprises a carbonate salt of sevelamer coated with a sodium chloride solution. In yet another 15 embodiment the tablet or composition comprises a carbonate salt of sevelamer and hydrochloric acid. In the above described embodiment, the monovalent anion, for example, the chloride ions comprise 0.01%, preferably 0.05%, more preferably a range of 0.01% to 2%, 0.05% to 1%, 0.08 % to 0.5%, or 0.1% to 0.3% the weight of the carbonate 20 salt of the aliphatic amine polymer plus the weight of the metal salt or acid, for example the weight of sevelamer carbonate plus the weight of sodium chloride. In another embodiment, the monovalent anion source is a monovalent anion salt of an aliphatic amine polymer comprising a repeat unit represented by Structural Formulas I-XI above. The combination of a carbonate salt of an aliphatic amine 25 polymer and a monovalent anion salt of an aliphatic amine polymer is defined herein as a "physically mixed polymer". The monovalent anion salt of the aliphatic amine polymer can be the same or a different aliphatic amine polymer as the aliphatic amine polymer carbonate salt. Preferably the monovalent anion salt of the aliphatic amine polymer is polyallylamine, more preferably the monovalent anion salt of the 30 aliphatic amine polymer is a homopolymer, most preferably the monovalent anion salt of the aliphatic amine polymer is sevelamer. In a preferred embodiment the monovalent anion source is a halide salt of sevelamer, more preferably sevelamer -14 chloride, (sold under the tradename RENAGEL*). In another preferred embodiment the monovalent anion salt of the aliphatic amine polymer is a chloride salt of sevelamer and the aliphatic amine polymer carbonate salt is sevelamer carbonate. In the above described embodiment the carbonate salt of the aliphatic amine 5 polymer and the monovalent anion salt of the aliphatic amine polymer are preferably at a molar ratio of 1:2000, 1:500, 1:100, 1:50, 1:20, 1:9, 1:6, 1:4, 1:3, 1:2, or 1:1 monovalent anion:carbonate salt, more preferably at a molar ratio of 1:4 monovalent anion:carbonate salt. In this embodiment, the monovalent anion, for example, the chloride ions, comprise at least 0.01%, preferably 0.05%, more preferably at a range 10 0.01% to 2%, 0.05% to 1%, 0.08 % to 0.5%, or 0.1% to 0.3% by weight of the weight of the carbonate salt of the aliphatic amine polymer plus the weight of the monovalent anion salt of the aliphatic amine polymer, for example, the weight of sevelamer carbonate plus the weight of sevelamer chloride. In another embodiment the monovalent anion source is the carbonate salt of 15 an aliphatic amine polymer. In this embodiment, the aliphatic amine polymer comprises mainly carbonate ions but also further comprises a monovalent anion other than carbonate. In this embodiment the present invention is a tablet comprising a mixed carbonate and monovalent anion salt of an aliphatic amine polymer. The combination of a carbonate salt and a monovalent anion salt on a 20 single aliphatic amine polymer is defined herein as a "chemically mixed polymer". The aliphatic amine polymer comprises repeat units represented by Structural Formulas I-XI above; preferably the aliphatic amine polymer is sevelamer. Any monovalent anion described above can be used in this embodiment. Preferably the monovalent anion salt is a halide salt, more preferably a chloride salt. Preferably the 25 mixture of carbonate salt to monovalent anion salt is at a molar ratio of monovalent anion:carbonate, of 1:2000, 1:500, 1:100, 1:50, 1:20, 1:4, or 1:1. In this embodiment the monovalent anion, for example, the chloride ions, comprise at least 0.0 1%, preferably 0.05%, more preferably at a range 0.01% to 2%, 0.05% to 1%, 0.08 % to 0.5%, or 0.1% to 0.3% by weight of the weight of the mixed carbonate 30 and monovalent anion salt of the aliphatic amine polymer, for example, the weight of sevelamer with both carbonate and chloride ions.

-15 These chemically mixed polymers can be prepared by adding, for example, aqueous solution of sodium carbonate and/or sodium bicarbonate to an aqueous solution of sevelamer chloride. The ratios of salts to sevelamer chloride may be varied in order to get the desired salt ratio in the chemically mixed polymer. 5 Preferred molar ratios include 1:2000, 1:500, 1:100, 1:50, 1:20, 1:4, or 1:1 sevelamer hydrochloride:carbonate. In another embodiment, the chemically mixed aliphatic amine polymer may be mixed with a carbonate salt of an aliphatic amine polymer. The aliphatic amine polymers comprise repeat units represented by Structural Formulas I-XI above and 10 may be the same or different. Preferably the chemically mixed polymer and the carbonate salt polymer are sevelamer. The preferred anions on the chemically mixed polymer are as described above. Preferably the chemically mixed polymer and carbonate polymer are at a molar ratio of chemically mixed salt:carbonate, of 1:2000, 1:500, 1:100, 1:50, 1:20, 1:4, or 1:1. 15 Increasing the particle size of the aliphatic amine polymer particles results in an increase in shelf life of the tablets of the present invention and prevents the disintegration time of the tablets from increasing over time. The particles comprise of an aliphatic amine polymer, preferably polyallyamine polymer, more preferably a homopolymer, most preferably sevelamer, and optionally one or more additional 20 pharmaceutically acceptable ingredients. In a preferred embodiment the particles comprise at least 80%, preferably at least 90% more preferably at least 95%, most preferably at least 100%, by weight of aliphatic amine polymer. In one embodiment, the present invention is a tablet comprising particles of a carbonate salt of aliphatic amine polymer, preferably polyallyamine polymer, more 25 preferably sevelamer, most preferably sevelamer carbonate, wherein at least 95% by volume of the particles have a diameter of at least 45 microns, at least 60 microns, at least 80 microns or at least 100 microns. These aliphatic amine polymer particles may be combined with for example, an excipient, carrier or diluent, to form the tablets or compositions of the present 30 invention. The tablets of the present invention can comprise one or more excipients, such as binders, glidants and lubricants, which are well known in the art. Suitable -16 excipients include colloidal silicon dioxide, stearic acid, magnesium silicate, calcium silicate, sucrose, cellulose, calcium stearate, glyceryl behenate, magnesium stearate, talc, zinc stearate and sodium stearylfumarate, a cellulose derivative such as carboxymethyl cellulose, microcrystalline cellulose, hydroxypropyl cellulose, 5 acacia, tragacanth, pectin, gelatin, polyethylene glycol. Preferably the cellulose derivative is microcrystalline cellulose, more preferably Ceolus@ (Asahi Kasei Chemicals Corporation). The tablets of the invention are prepared by a method comprising the steps of: (1) hydrating or drying the aliphatic amine polymer to the desired 10 moisture level; (2) blending the aliphatic amine polymer with any excipients to be included; and (3) compressing the blend using conventional tableting technology. The tablet is optionally coated, i.e., the aliphatic amine polymer and 15 excipients form a core surrounded by a coating. In one embodiment, the coating composition comprises a cellulose derivative and a plasticizing agent. The cellulose derivative is, preferably, hydroxypropylmethylcellulose (HPMC). The cellulose derivative can be present as an aqueous solution. Suitable hydroxypropylnethylcellulose solutions include those containing HPMC low 20 viscosity and/or HPMC high viscosity. Additional suitable cellulose derivatives include cellulose ethers useful in film coating formulations. The plasticizing agent can be, for example, an acetylated monoglyceride such as diacetylated monoglyceride, The coating composition can further include a pigment selected to provide a tablet coating of the desired color. For example, to produce a white 25 coating, a white pigment can be selected, such as titanium dioxide. In one embodiment, the coated tablet of the invention can be prepared by a method comprising the step of contacting a tablet core of the invention, as described above, with a coating solution comprising a solvent, at least one coating agent dissolved or suspended in the solvent and, optionally, one or more plasticizing 30 agents. Preferably, the solvent is an aqueous solvent, such as water or an aqueous buffer, or a mixed aqueous/organic solvent. Preferred coating agents include cellulose derivatives, such as hydroxypropylmethylcellulose. Typically, the tablet -17 core is contacted with the coating solution until the weight of the tablet core has increased by an amount ranging from about 3% to about 6%, indicating the deposition of a suitable coating on the tablet core to form a coated tablet. In one preferred embodiment, the solids composition of the coating solution 5 is: Material %W/W HPMC low viscosity Type 2910, cUSP 38.5% HPMC high viscosity Type 2910, cUSP 38.5% 10 diacetylated monoglyceride 23.0% Tablets may be coated in a rotary pan coater as is known in the art or any other conventional coating apparatus such as a column coater or a continuous coater. The present invention also encompasses pharmaceutical compositions other 15 than tablets. These pharmaceutical compositions comprise a pharmaceutically acceptable carrier or diluent and a carbonate salt of an aliphatic amine polymer and a monovalent anion source as described above. Preferably the monovalent anion source comprises at least 0.0 1%, preferably 0.05%, more preferably at a range 0.01% to 2%, 0.05% to 1%, 0.08 % to 0.5%, or 0.1% to 0.3% by weight of the 20 combined weight of the carbonate salt and the monovalent anion source. The aliphatic amine polymers, tablets and compositions of the present invention are preferably administered orally. They can be administered to the subject alone or in a pharmaceutical composition, and optionally, one or more additional drugs. The pharmaceutical compositions of the invention preferably 25 contain a pharmaceutically acceptable carrier or diluent suitable for rendering the compound or mixture administrable orally. The active ingredients may be admixed or compounded with a conventional, pharmaceutically acceptable carrier or diluent. It will be understood by those skilled in the art that any mode of administration, vehicle or carrier conventionally employed and which is inert with respect to the 30 active agent may be utilized for preparing and administering the pharmaceutical compositions of the present invention. Illustrative of such methods, vehicles and - 18 carriers are those described, for example, in Remington's Pharmaceutical Sciences, 18th ed. (1990), the disclosure of which is incorporated herein by reference. The formulations of the present invention for use in a subject comprise the agent, together with one or more acceptable carriers or diluents therefore and 5 optionally other therapeutic ingredients. The carriers or diluents must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof. The formulations can conveniently be presented in unit dosage form and can be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing into association the agent with 10 the carrier or diluent which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the agent with the carriers and then, if necessary, dividing the product into unit dosages thereof. Those skilled in the art will be aware that the-amounts of the various 15 components of the compositions of the invention to be administered in accordance with the method of the invention to a subject will depend upon those factors noted above. The compositions of the invention can be formulated as a tablet, sachet, slurry, food formulation, troche, capsule, elixir, suspension, syrup, wafer, chewing gum or 20 lozenge. A syrup formulation will generally consist of a suspension or solution of the compound or salt in a liquid carrier, for example, ethanol, glycerine or water, with a flavoring or coloring agent. Where the composition is in the form of a tablet, one or more pharmaceutical carriers routinely used for preparing solid formulations can be employed. Examples of such carriers include magnesium stearate, starch, lactose and 25 sucrose. Where the composition is in the form of a capsule, the use of routine encapsulation is generally suitable, for example, using the aforementioned carriers in a hard gelatin capsule shell. Where the composition is in the form of a soft gelatin shell capsule, pharmaceutical carriers routinely used for preparing dispersions or suspensions can be considered, for example, aqueous gums, celluloses, silicates or 30 oils, and are incorporated in a soft gelatin capsule shell. The aliphatic amine polymers, tablets and compositions can be administered as multiple dosage units or as a single dosage unit. As used herein a dosage unit -19 may be a tablet, sachet, slurry, food formulation, troche, capsule, elixir, suspension, syrup, wafer, chewing gum or the like prepared by art recognized procedures. Preferably a dosage unit is a tablet, capsule, sachet, slurry, suspension or food formulation, more preferably the dosage unit is a tablet, slurry, suspension or food 5 formulation, most preferably the dosage unit is a tablet or sachet. Typically, the desired dose of an aliphatic amine polymer is administered as multiple tablets or capsules, or a single dose of a sachet, slurry, food formulation, suspension or syrup. In one example, the dosage unit is an oval, film coated, compressed tablet containing either 800 mg or 400 mg of sevelamer on an anhydrous basis. The 10 inactive ingredients are sodium chloride, zinc stearate, Ceolus*, hypromellose, and diacetylated monoglyceride. In yet another embodiment, the dosage unit is a hard gelatin capsule containing 403 mg of sevelamer on an anhydrous basis. The inactive ingredients are sodium chloride, zinc stearate, Ceolus*, hypromellose, and diacetylated monoglyceride. 15 The aliphatic amine polymers, tablets and compositions of the present invention are preferably administered with meals. The methods of the invention involve treatment of patients with hyperphosphatemia. Elevated serum phosphate is commonly present in patients with renal insufficiency, hypoparathyroidism, pseudohypoparathyroidism, acute untreated 20 acromegaly, overmedication with phosphate salts, and acute tissue destruction as occurs during rhabdomyolysis and treatment of malignancies. As used herein a subject is a mammal, preferably a human, but can also be an animal in need of veterinary treatment, such as a companion animal (e.g., dogs, cats, and the like), a farm animal (e.g., cows, sheep, pigs, horses, and the like) or a 25 laboratory animal (e.g., rats, mice, guinea pigs, and the like). A therapeutically effective amount of compound is that amount which produces a result or exerts an influence on the particular condition being treated. As used herein, a therapeutically effective amount of a phosphate binder means an amount which is effective in decreasing the serum phosphate levels of the patient to 30 which it is administered. Typical dosages of phosphate binders range from about 5 milligrams/day to about 10 grams/day, preferably from about 50 milligrams/day to about 9 grams/day, - 20 more preferably from about 1 gram/day to about 8 grams/day, even more preferably about 2 grams to about 7 grams, most preferably about 4 grams/day to about 6 grams/day. The phosphate binders of the present invention can be administered at least four times per day with meals, at least three times per day with meals, at least 5 twice per day with meals, at least once pre day with meals, (see US Provisional Application No. 60/623,985 the entire contents of which are incorporated herein by reference). EXEMPLIFICATION 10 EXAMPLE 1 Better compactibility and disintegration time of mixed aliphatic amine carbonate salt and monovalent anion formulation as compared to the formulation containing sevelamer carbonate alone. 15 The term "physically mixed salt" refers to dry blending of sevelamer HCI and sevelamer carbonate API (2 compounds). The total chloride was targeted to be in the range of 4 to 6%. Based on the ratios of sevelamer hydrochloride to sevelamer carbonate used, the % LOD for the final mixture of sevelamer hydrochloride and sevelamer 20 carbonate was calculated. For the wetting of the mixture to target % loss on drying (LOD), the sevelamer hydrochloride API, sevelamer carbonate API and Ceolus* were added directly to the Diosna (a high shear wetting equipment/granulator). The blend was mixed for 3 minutes using the impeller rotating at 435 rpm. Purified water was then added to the blend using a spray bottle to achieve the target LOD in a 25 Diosna Granulator over a 20 minute mixing period. The blend was mixed for an additional 3 minutes at an impeller speed of 435 rpm. The blend was transferred from the Diosna bowl to a double lined plastic bag that was then securely closed and stored in a plastic container. The wetted blend was allowed to equilibrate for 24 hours. 30 After 24 hours, the required quantities of wetted material and lubricant were weighed. The wetted material was screened using a co-mill fitted with a 600-micron screen with the impeller rotating at 2500 rpm. A portion of wetted blend was bag- -21 blended with appropriate lubricant, passed through a 600-micron screen and a second portion of wetted sevelamer was passed through the 600-micron screen. The wetted blend and lubricant were then blended in a V-blender for 115 revolutions. The powder blend was compressed into tablets using a rotary tablet press 5 (Jenn-Chiang Machinery Co. Ltd., (JCMCO)) adjusted to meet the target weight and hardness. The press was set up with I station of B press tooling which has the same surface area as the commercial tooling (0.405' x 0.748"). The tablets were compressed using different compression parameters. An average compactibility (ratio of tablet hardness over the main compression force used on the tablet press) 10 was determined from these conditions. The tablets were dedusted. This process was generally done at 0.5 to 1.5 kg scale. The disintegration testing of the tablets was performed in simulated gastric fluid USP without enzymes having a pH of 1.2 (0. 1N HCl). The details of the disintegration apparatus and procedure followed are described below. 15 Disintegration testing Apparatus (USP27/NF22): The apparatus consisted of a basket-rack assembly, a 1000-ml beaker, a thermostatic arrangement for heating the fluid between 35*C and 3 9*C, and a device for raising and lowering the basket in the immersion fluid at a constant frequency 20 rate between 29 and 32 cycles per minute. The basket-rack assembly consisted of six open-ended transparent tubes. The tubes were held in a vertical position by two plastic plates with six holes equidistant from the center of the plate and equally spaced from one another. Attached to the 25 under surface of the lower plate was a woven stainless steel wire cloth which had plain square weave with 1.8 to 2.2 mm mesh apertures and with a wire diameter of 0.63 ± 0.03 mm. A 10-mesh screen was also put on the top of the basket to avoid the tablet from coming out during the disintegration testing. A suitable means was provided to suspend the basket-rack assembly from the raising and lowering device 30 using a point on its axis. Testing procedure: -22 The simulated gastric fluid USP without enzymes having a pH of 1.2 (0.IN HCl) (900ml) was placed in the 1000 ml beaker and heated to 37 "C using the water bath of the disintegration apparatus. Two tablets were tested by putting each one in separate tubes of the basket-rack assembly and a 10 mesh screen was placed on the 5 top to prevent the tablets from coming out. The lowering and raising device was turned on and the tablets were observed for the rupture time (i.e. the time when the coating on the tablet first ruptures and polymer starts coming out) and disintegration time (i.e. the time when the tablet disintegrates completely and comes out from the tube of the basket-rack assembly). 10 The physically mixed salt formulations containing sevelamer hydrochloride and sevelamer carbonate Active Pharmaceutical Ingredient (API) were evaluated. The data suggested that physically mixed salt formulation had better compactibility and disintegration time as compared to the formulation containing sevelamer carbonate API only (see Table 1). The disintegration time for the tablets 15 manufactured using the physically mixed salt approach was significantly faster as compared to the formulation containing sevelamer carbonate API only. Table 1: Comparison of sevelamer carbonate vs physical mixture approaches Dsnegmtonbm(mnueS)of Core 5eeMu SmUBw S H Tablets stomd at60C.Perornd in pH1.2 Ap-hDC.CDLzhdt % Haimsls&__ vMt disk ur* sowm A~~mac*use LuLCO %ChE GS m~~lwicod 4Zbonae 5ev. 003 useal [t# & atoo " Aveage Averge1 Aveage Aeage 0 week weefs wees sndamer CwbW 10.5 14 0.25 1.2 NA 2416344 NA 431 32 .4 34.8 38.8 8 0 0.375 Sear cadd 0.4 2448260 2416344 1 t3 38 2.5 27 24 24 ftxd 2327_ tD ND ND ND 8 0 0.375 sb~tcadd Q4 244826 2416344 1toB 8 8 1.7 ND 0.7 1.4 8 0 0.375 sICedd 0.4 2448 2416344 Ito9 90 2.3 ND ND 22 20 The above results show that the physically mixed salt formulation can provide desirable compactibility and the disintegration times remain more stable over time compared to formulation containing sevelamer carbonate only. 25 EXAMPLE 2 Effect of various ratios of sevelamer HCI to sevelamer carbonate on compactibility, ejection forces and disintegration times.

- 23 The sevelamer hydrochloride to sevelamer carbonate ratios of 1:1, 1:3, 1:6 and 1:9 were evaluated using the excipients used in the Renagel* formulation (800mg active API, 8% target LOD, 0.375% colloidal silicon dioxide and 0.4% stearic acid) (see Table 2). All experiments were carried out as described above for 5 Example 1 Table 2: Effect of various ratios of sevelamer HC1 to sevelamer carbonate on disintegration times. 10 Formulation: 8% LOD, No Ceolus, 0.375% Colloidal silicon dioxide (CSD), 0.4% stearic acid Sev. HCI: CF Compactibility Disintegration Time (minutes) of Core Sev. C03 PC (kN) -(kN) (N/kN) Tablets stored at 60C. Performed in pH wt. Ratio 1.2 with disk and screen Average t Average Average Average =0 1 week 2 weeks 3 weeks I to 1 is 19 15.9 0.8 1.9 1.3 1.3 I to3 15 44 8.7 2.5 2.7 2.4 2.4 1 to 6 15 45 2.2 1.7 ND 0.7 1.4 1 to 9 15 45 2.0 2.3 ND ND 2.2 ND: Not determined, PC: Precompression force; CF: Compression Force; Disintegration testing, n=2 15 Based on the above studies, it can be seen that the disintegration time is maintained in a pharmaceutically acceptable range with all the ratios of chloride to carbonate salts evaluated. EXAMPLE 3 20 Comparison of physically mixed salts with chemically mixed salts All experiments were carried out as described above for Example 1. As can be seen from Table 3 the chemically mixed salt also resulted in pharmaceutically acceptable disintegration times.

- 24 The chemically mixed salt were prepared by adding sevelamer hydrochloride to an aqueous solution of sodium carbonate and sodium bicarbonate. Table 3: Comparison of physically mixed and chemically mixed salt 5 Disintegration Tine mitese) of Coro A oaaLaMo sow Tablets stored at 60C. Perform d in pH 1.2 Approach %LOD %Cehus Lubricant %o M nate %Chod Hanis Wtdikandscreen delot# lot Averaget Averagel Arge Aerage2 =0 week weeks weeks 10.5 5 PRUN 0.5 2448260 2416344 4 488 1.1 2.4 2.8 3 ialy 10.5 5 PRUV 0.5 NA NA 5 305 12.1 11.3 11.2 11.5 10.5 5 0.5 244820 2418344 4 48 1.0 4.4 4.9 5.2 ixed____ nicy 10.6 0.5 NA NA 5 116 7.1 .7 6 6.2 mixe slsarate EXAMPLE 4 Comparison of sevelamer carbonate with sodium chloride and without sodium 10 chloride All experiments were carried out as described above for Example 1. As can be seen from Table 4 the disintegration time increased much more in the case for sevelamer carbonate without sodium chloride. 15 Table 4: Comparison of sevelamer carbonate with sodium chloride and without sodium chloride Disintegration Time (minutes) of core Tablets stored at 80C. Performed In pH 1.2 Approach % LOD % ceolus Lubricant Serboate Hardness with disk and screen lot # Average t Average I Average 2 Average 3 0 week weeks weeks No sodum 10.5 14 Sodium stearyl 2416570 194 2.7 24.2 ND 29.5 chloride unrtI 0.25% Sodium 10.5 15 Sodium stearyl 2416344 352 3.9 8.8 9.4 13.4 chloride 10.5 fumerete 20 From the above studies, it was determined that addition of sodium chloride to sevelamer carbonate significantly decreases the increase in the disintegration time.

- 25 EXAMPLE 5 Effect of particle size cut on the disintegration behavior and compactibility Different particle sizes were compared for the effect on compactibility and 5 disintegration time using a formulation of: 6.5% LOD ("as is" API moisture), 25% Ceolus* KG 802, 1.2% Glyceryl dibehenate, No Colloidal silicon dioxide (CSD), (API: 20% carbonate). All experiments were carried out as in Example 1. The compression conditions were: precompression force: 15kN, compression force: 45kN, and speed: 20rpm. The results can be seen in Table 5. 10 Table 5: Effect of particle size cut on the disintegration behavior and compactibility. Disintegration time (minutes) of Lab notebook Particle size Ejection Compact core tablets stored at 60C. number cuts (micron) (N) . (N/kN) Performed in pH 1.2 with disc and screen . 15 0495-200 "As Is" 316 8.2 2.6 12.6 15.0 15.0 ______ _____ API__ _ _ ___ _ _ __ _ _ _ 0484-170 >53 326 8.2 1.9 ND 6.3 7.2 0484-171 >75 316 6.9 1.8 ND 5.5 6.2 0484-172 >90 320 6.3 1.5 ND 4.9 5.5 0484-138 >106 330 5.8 1.0 4.4 5.2 4.5 20 The above results show that the formulations with increased particle sizes maintain a more stable disintegration time over time compared to formulations with smaller particles sizes. While this invention has been particularly shown and described with 25 references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

C:NRPotb\DCC\RXSW I14761tDOC -23M lIZ - 26 The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (49)

1. A composition, comprising: i) a carbonate salt and a bicarbonate salt of sevelamer; and ii) a monovalent anion source; wherein the monovalent anion comprises at least 0.05% by weight of the combined weights of the sevelamer carbonate, sevelamer bicarbonate, and the monovalent anion source.

2. A composition according to claim 1, wherein the monovalent anion comprises 0.05% to 2% by weight of the combined weights of the sevelamer carbonate, sevelamer bicarbonate, and the monovalent anion source.

3. A composition according to claim 1 or claim 2, wherein the monovalent anion comprises 0.05% to 1% by weight of the combined weights of the sevelamer carbonate, sevelamer bicarbonate, and the monovalent anion source.

4. A composition according to any one of claims 1-3, wherein the monovalent anion source is a monovalent anion salt of sevelamer.

5. A composition according to any one of claims 1-4, wherein the monovalent anion is a halide.

6. A composition according to any one of claims 1-5, wherein the halide is a chloride.

7. A composition according to any one of claims 1-6, wherein the monovalent anion source is a metal salt of a monovalent anion or an acid of a monovalent anion.

8. A composition according to any one of claims 1-7, wherein the monovalent anion source is sodium chloride, hydrochloric acid, or sodium bicarbonate. C:\NRPonbl\DCC\RXS\411476I_1.DOC-23A1/212 - 28

9. A composition according to any one of claims 1-8, wherein the monovalent anion source is sodium chloride.

10. A composition according to any one of claims 1-9, wherein comprises one or more excipients comprising zinc stearate or a cellulose derivative.

11. A composition according to claim 10, wherein the composition comprises zinc stearate.

12. A composition according to any one of claims 10-11, wherein the composition comprises a cellulose derivative.

13. A composition according to claim 12, wherein the cellulose derivative comprises carboxymethyl cellulose.

14. A composition according to any one of claims 12-13, wherein the cellulose derivative comprises microcrystalline cellulose.

15. A composition according to any one of claims 12-14, wherein the cellulose derivative comprises hydroxypropyl cellulose.

16. A composition according to any one of claims 12-14, wherein the cellulose derivative comprises hydroxypropylmethylcellulose (HPMC).

17. A composition according to any one of claims 12-14, wherein the cellulose derivative comprises low viscosity hydroxypropylmethylcellulose.

18. A composition according to any one of claims 12-14, wherein the cellulose derivative comprises high viscosity hydroxypropylmethylcellulose.

19. A composition according to any one of claims 12-14, wherein the cellulose CNRVolnbN)CC\RXS\4114761_ .DOC-25A)1/2012 -29 derivative comprises low viscosity hydroxypropylmethylcellulose and high viscosity hydroxypropylmethylcellulose.

20. A composition according to any one of claims 12-14, wherein the cellulose derivative comprises hypromellose.

21. A composition according to any one of claims 1-20, wherein the composition comprises a plasticizing agent.

22. A composition according to any one of claims 1-21, wherein the composition comprises diacetylated monoglyceride.

23. A composition according to any one of claims 1-22, wherein the composition comprises a bicarbonate salt of sevelamer and sodium chloride powder.

24. A composition according to any one of claims 1-22, wherein the composition comprises a bicarbonate salt of sevelamer coated with a sodium chloride solution.

25. A composition according to any one of claims 1-22, wherein the composition comprises a bicarbonate salt of sevelamer and hydrochloric acid.

26. A pharmaceutical composition comprising a composition according to any one of claims 1-25.

27. A pharmaceutical composition comprising a pharmaceutically acceptable carrier or diluent and a carbonate salt of sevelamer, a bicarbonate salt of sevelamer, and a monovalent anion source, wherein the monovalent anion comprises at least 0.05% by weight of the combined weight of the sevelamer carbonate, the sevelamer bicarbonate, and the monovalent anion source.

28. A pharmaceutical composition according to claim 27, wherein the monovalent C:\NRPonbrlDCC\LXS\4i14761_ .DOC.2501/2012 -30 anion source is a chloride source and wherein chloride comprises 0.05% to 2% by weight of the combined weights of the sevelamer carbonate, the sevelamer bicarbonate, and the chloride source.

29. A pharmaceutical composition according to claim 27, wherein the monovalent anion source is a chloride source and wherein chloride comprises 0.05% to 1% by weight of the combined weights of the sevelamer carbonate, the sevelamer bicarbonate, and the chloride source.

30. A tablet comprising a pharmaceutical composition according to any one of claims 26-29.

31. A tablet comprising the composition according to any one of claims 1-25.

32. A tablet comprising the composition according to any one of claims 1-25, wherein the tablet is coated with a coating composition.

33. A tablet according to claim 32, wherein the coating composition comprises a plasticizing agent.

34. A tablet according to claim 32, wherein the coating composition comprises diacetylated monoglyceride.

35. A tablet according to any one of claims 32-34, wherein the coating composition comprises a cellulose derivative.

36. A tablet according to claim 35, wherein the cellulose derivative comprises hypromellose.

37. A tablet according to claim 35, wherein the cellulose derivative comprises hydroxypropylmethylcellulose (HPMC). C:\NRPotblDCC\RXSUI 14761.1DOC-25/01/212 -31

38. A tablet according to claim 35, wherein the cellulose derivative comprises low viscosity hydroxypropylmethylcellulose.

39. A tablet according to claim 35, wherein the cellulose derivative comprises high viscosity hydroxypropylmethylcellulose.

40. A tablet according to claim 35, wherein the cellulose derivative comprises low viscosity hydroxypropylmethylcellulose and high viscosity hydroxypropylmethylcellulose.

41. A tablet according to any one of claims 30-40, wherein the tablet comprises 800 mg of a mixture of sevelamer carbonate and sevelamer bicarbonate on an anhydrous basis.

42. A tablet according to any one of claims 30-40, wherein the tablet comprises 400 mg of a mixture of sevelamer carbonate and sevelamer bicarbonate on an anhydrous basis.

43. A tablet according to any one of claims 30-42, wherein the tablet core is contacted with the coating solution until the weight of the tablet core has increased by an amount ranging from 3% to 6%.

44. A tablet according to any one of claims 30-43, wherein the tablet is an oval, film coated, compressed tablet.

45. A method of removing phosphate from a patient including the step of administering to the patient a composition according to any one of claims 1-25.

46. Use of the composition according to any one of claims 1-25 in the manufacture of a medicament for removing phosphate from a patient.

47. A method of removing phosphate including the step of administering to the patient a pharmaceutical composition according to any one of claims 26-29. C:NlRPonbrlCCiRXSlI 14761,1.DOC-251i121112 - 32

48. Use of the pharmaceutical composition according to any one of claims 26-29 in the manufacture of a medicament for removing phosphate from a patient.

49. A method of removing phosphate from a patient including the step of administering to the patient a tablet according to any one of claims 30-44.