PHARMACEUTICAL COMPOSITIONS

Abstract: The present invention provides for a phased-release oral dosage form comprising a plurality of H2 receptor antagonist pellets in a polymer matrix. Each phase, containing a plurality of pellets which may be optionally coated with a release delaying substance, may have different release rates, thereby providing release of the H2 antagonist over an extended duration of time.

Description: PHARMACEUTICAL COMPOSITIONS FIELD OF THE INVENTION This invention relates to solid oral pharmaceutical compositions containing cimetidine. BACKGROUND OF THE INVENTION Cimetidine is a histamine ^-antagonist which has been described in U.K. Patent Specification 1,397,436. Cimetidine has been shown to be useful in the treatment of duodenal, gastric, recurrent and stomal ulceration, and reflux oesophagitis and in the management of patients who are at high risk from haemorrhage of the upper gastrointestinal tract. Cimetidine has been made available to patients in a variety of dosage forms; for example, tablets, granules, syrups and suspensions. In most, if not all, of these dosage forms, the cimetidine is in an immediate-release form; that is to say the nature of the formulation is such that by the time the cimetidine leaves the stomach, it is either in solution or is in the form of a suspension of fine particles, i.e. a form from which it can be readily absorbed. Coating agents which prevent release of an active ingredient in the stomach but which allow release in the intestines are known as enteric coating agents and many such substances are known in the art for this purpose. Similarly, agents which form a matrix in which the active ingredient is embedded are known to modify the release of the active ingredient. However, it has been found that, when many such release delaying substances are used in conjunction with cimetidine, although release is delayed, the bioavailability of the cimetidine is substantially reduced. SUMMARY OF THE INVENTION The present invention provides for a phased-release oral dosage form comprising an H2 antagonist in a polymer matrix. The dosage form may comprise a plurality of matrix cores containing an H2 antagonist which matrix cores have different release rates or modified-release phases as used herein. The phased-release (or modified- release phase) may contain two, three, four or more phases of modified-release polymer matrix-cores (or matrixes). The dosage form preferably comprises an immediate-release EET phase of cimetidine as well as the modified release phase. The modified release phase alone or in combination with immediate release of cimetidine is able to extend the duration of action of cimetidine and thereby provide improved bioavailability of cimetidine. DETAILED DESCRIPTION OF THE INVENTION In one aspect, the present invention is a modified-release dosage form which comprises an H 2 antagonist in a polymer matrix core. The modified release form, preferably composed of pellets, comprises a plurality of discrete polymer matrix particules suitable for combination into an oral dosage form. The oral dosage form may comprise multiple release phases of matrixes each of which comprises an H 2 antagonist incorporated, independently, into the polymer matrixes. The modified release phase matrix-core may be un-coated (hereinafter referred to as the "uncoated matrix") or coated (hereinafter referred to as a "coated matrix") with a release-delaying substance. Preferably, when the matrix-core is coated with the release delaying substance, the release delaying substance is present in an amount of from 2 to 30% (w/w) relative to the matrix-core. More preferably, the release-delaying substance is present in an amount of from 5 to 25% (w/w). Another aspect of the present invention provides for various combinations of modified-phase release pellets with other pellets, for example, the uncoated matrix pellets may be in combination with 1) an immediate release phase pellet of the same H 2 antagonist, preferably cimetidine; 2) a coated matrix pellets containing the same H2 antagonist; 3) coated matrix pellets with immediate release phase pellets; 4) coated matrix pellets in combination with additional uncoated matrix pellets of a different polymer base; 5) coated matrix pellets in combination with additional uncoated matrix pellets of a different polymer base and immediate release phase pellets. The matrix-core pellets may be coated independently with different release-delaying substances all of which may be combined with the uncoated or immediate release phase pellets of cimetidine. Therefore, additional combinations such as changing the polymer bases for the coated and uncoated matrixes as well as changing the release delaying substance in each of the above noted combinations is also contemplated within the scope of the invention. Yet another aspect of the present invention provides for an additional modified-release phase to be present in combination with the coated or un-coated matrix, with or without immediate release, which additional modified-release phase comprises at least one core of cimetidine coated with a release-delaying substance (hereinafter referred to as "immediate coated"). The release-delaying substance present in the immediate coated pellets is present in an amount from about 2 to about 30% (w/w) relative to the granule. Preferably the substance is present in an amount of 5 to 25% (w/w). More preferably this invention provides for combinations of the immediate coated pellets with coated matrix and immediate release pellets; as well as various combinations of immediate coated pellets with uncoated matrix and immediate release pellets; as well as immediate coated pellets with coated matrix and un-coated matrix pellets. The combination of all four types of pellets (immediate-release, immediate coated, un-coated matrix and coated matrix) is also contemplated as a further aspect of the present invention and is described below in its preferred embodiment : A modified-release oral dosage form comprising: a) an immediate-release phase of cimetidine; b) a "first" modified release phase which comprises a matrix-core which comprises cimetidine incorporated into a polymer matrix; c) a "second" modified release phase matrix-core which comprises cimetidine incorporated into a polymer matrix coated with a first modified release-delaying substance in an amount of from 2 to 30% (w/w) relative to the matrix-core (hereinafter referred to as a "coated matrix"); and d) a "third" modified-release phase which comprises at least one core of cimetidine coated with a second modified release-delaying substance in an amount of from 2 to 30% (w/w) relative to the core (hereinafter refeιτed to as "immediate coated"). As the release-delaying substances, which can for instance be enteric coatings, slow release, or delayed release, may vary independently with the matrix core(s) o the immediate release pellets of cimetidine, therefore all combinations of such coatings are contemplated to be within the scope of this invention. Further, as the polymer used to granulate the matrix can vary with the release phase desired, the various combinations of matrixes having different polymer cores is also contemplated within the scope of this invention. Examples of H 2 antagonists useful in the present invention include, but are not limited to, cimetidine, rantidine, famotidine, nizatidine and roxatidine. Immediate release phase, as used herein, is intended to mean a short pulse, i.e., a dissolution time and absorption from the gastric juices from immediate release to about 45 minutes. The immediate-release phase of the present invention contributes to a first pulse of cimetidine in the stomach. Such immediate-release formulations for instance of cimetidine are old and well known to those skilled in the art, for example, U.S. Patent No.4,024,271 issued May 17, 1977. The immediate release phase pellets of the present invention, as described in the Example Section, herein meet such criteria. The immediate release phase of the present invention preferably comprises cimetidine as a pellet or granule (one core) not comprising a delayed released substance. Modified release phase, as used herein, is intended to mean a controlled release of cimetidine such that cimetidine is not immediately and completely released into the stomach, within the time frame noted above, and remains available to the mammal for release over a prolonged period of time. The release may occur in the stomach or the intestinal tract The immediate coated release pellets of the present invention, are made from coated "immediate release" pellets of cimetidine. However, it is within the scope of this invention that any immediate release form of cimetidine is contemplated and is not limited to a bead or pellet formulation as described herein. Bulk cimetidine, granulated cimetidine and coated cimetidine particles thereof are but one aspect of the present invention. The overcoating as contemplated herein for the immediate release dosage forms, are the enteric coatings. The enteric coating art is well known to those skilled in the art and is suitably described in Example 1 herein. The immediate coated release pellets of the present invention will allow for release of the cimetidine over a period of time in the intestinal tract (dependent upon the type and amount of coating chosen). The "release delaying substance" of the present invention, as used herein, is a coating agent or blend of agents thereof, which protects the active ingredient, the H 2 antagonist, from immediate degradation in the stomach. The overcoating, depending upon the release rate desired may allow for continual release (or slow release) or may be a delayed release. The modified release phase of an uncoated matrix pellet, as used herein, will result in a pulse of cimetidine which, depending upon the polymer used in the matrix itself, continue to release cimetidine for a period of time exceeding that of the immediate release. Preferably the release will continue for up to 4 hours. More preferably the release will continue for up to 8 hours. A preferred embodiment of the invention is an immediate release of the H2 antagonist, followed by a 10% release of the H2 antagonist by 4 hours, followed thereby with a 10 to 15% release rate each hour up to 8 hours. The modified release phase of a coated matrix pellet as used herein, results in the absence of available cimetidine in the stomach and allows for its release in the intestinal tract , i.e. as a "third" pulse in combination with immediate and uncoated matrix pellets. Dependent upon the coating and polymer used in the matrix a prolonged release of cimetidine in the intestinal tract will occur over an extended period of time. In this manner the duration of action of cimetidine can be extended providing good bioavailability. Extending the duration of action of cimetidine increases the rate of healing in gastric or duodenal ulceration and is advantageous in disease states such as gastro- esophageal reflux disease, dyspepsia or stress ulceration where prolonged control of acid secretion is desirable. The cimetidine may be present as the free base or as a pharmaceutically acceptable salt, for example the hydrochloride salt. The immediate-release phase of cimetidine can exist in any of the commonly used types of solid dosage form, for example, as tablets, pellets or granules which can optionally be coated with a coating agent which dissolves in the gastric juices or which can optionally be contained within a gelatin capsule. The modified release phase matrix can similarly exist as a tablet, pellet or granule and is optionally coated with the release-delaying substance. The additional modified-release phases, such as the immediate coated may also exist as a tablet, pellet or granule coated with the same, or different release-delaying substance, and which can optionally be contained within a gelatin capsule.. The immediate and modified-release phases can be presented separately or more conveniently combined in a single dosage form. Thus, for example, a combination can take the form of immediate-release phase pellets, "first modified-release phase" un-coated matrix pellets, "second modified-release phase" coated matrix pellets, and "third modified-release phase" immediate coated pellets, all optionally contained within a gelatin capsule. It is possible to have various combinations of the dosage forms, such as immediate release with coated matrix; immediate release with uncoated matrix; immediate release with immediate coated and coated matrix; or immediate release with immediate coated and un-coated matrix. The immediate release phase and the modified release phase (an uncoated matrix, coated matrix or immediate coated pellet) are preferably contained in a single dosage form. The immediate release phase and modified release phase are preferably composed of pellets or beads (used interchangeably herein). The pellets are preferably contained in a capsule, which is preferably made of gelatin. For paniculate dosage forms such as pellets or granules and in a two phase system, of the total amount, preferably the immediate release phase is present in an amount of about 5 to 40% (w/w). The first and second modified release substance (the coated or un-coated matrix respectively) is thereby present in an amount of 60 to 95% (w/w) relative to the immediate release dosage form. Preferably, either matrix is present in an amount of 70 to 90% (w/w) relative to the immediate release form of 10 to 30% (w/w). For a three phase system, which can include either or both of the coated and un-coated matrixes, of the total amount, the immediate release dosage form is present in an amount of about 5 to 40%, the coated matrix dosage form is present in an amount of about 10 to 85% (w/w) relative to the immediate release dosage and an immediate coated dosage form is present in an amount of about 10 to 85% (w/w) also relative to the immediate release dosage form. Preferably the immediate release dosage form is present in an amount of about 5 to 30%, the coated matrix dosage form is present in an amount of about 20 to 75% (w/w), and the immediate coated dosage form is present in an amount of about 20 to 75% (w/w). The modified release substances should preferably be present in about 66 to 75% total (w/w) of the cimetidine dosage form. More preferably the immediate release dosage form in present in an amount of about 15 to 25%, the immediate enteric coated dosage form is present in an amount of about 20 to 30%, and the coated matrix dosage form is present in an amount of 45 to 60%. For the four phase system, the immediate release dosage form is present in an amount of about 5 to 40%, the (un)-coated matrix dosage form is present in an amount of about 10 to 75% (w/w) relative to the immediate release dosage and the immediate coated dosage form is present in an amount of about 5 to 75% (w/w) also relative to the immediate release dosage form. Preferably the immediate release is present in an amount of about 5 to 30%, the coated matrix in an amount about 20 to 70% (w/w), the un-coated matrix in an amount about 20 to 70% (w/w), and the immediate coated substance in present in an amount about 10 to 30% (w/w). As in the case of the three phase system, the modified release substances should preferably be present in about 66 to 75% total (w/w) of the total dosage form. Suitably the coating agents used for the immediate-release phase of cimetidine will dissolve in the gastric juices. Such coating agents are well known to those skilled in the art and include, but are not limited to hydroxypropyl methylcellulose, or methyl cellulose. Suitably the coating agents used for the modified-release phase matrixes are agents or blends of agents such as, but not limited to, enteric coating agents selected from copolymers based on methacyriic acid and ethyl acrylate; copolymers based on methacyrlic acid and methacrylates (also referred to as methacrylic acid copolymers, Type A-C United States Pharmacopia, 22nd Edition); copolymers based on hydroxypropyl methylcellulose phthalate, cellulose acetate phthalate, polyvinyl acetate phthalate, or mixtures thereof. The coating agents of the additional, or second and third modified-release phase substances need not be the same, however, conveniently they are essentially the same. Preferably the coating agent is Eudragit ™L30D which is an aqueous dispersion containing 30% (w/w) of an acrylic resin formed from a copolymer based on polymethacrylic acid and acrylic acid esters. The acrylic resin is soluble in intestinal juice from pH 5.5 upwards. The process of producing the coated modified-release phase tablets, pellets and particules is also well known to those skilled in the art and may be readily achieved by suspending the material to be coated in fluidized bed equipment, spraying the coating solution onto the material and subsequently drying. Alternatively, the coating can be carried out in pans designed for such purpose and employing similar spraying techniques to coat materials and subsequently drying thereafter. The matrix material comprising the modified release phase contains a suitable polymer which forms a matrix from which the cimetidine can be gradually released. Suitable materials are the water swellable polymers, or polymers which are non-water swellable but water permeable. Examples of suitable polymers useful in this invention include, but are not limited to a non-ionic neutral copolymers based on ethyl acrylate and methyl acrylate (also referred to as polyacrylates), such as Eudragit™ NE30D, acrylic and methacrylic acid esters, such as Eudragit™ RS30D, ethyl cellulose, hydroxypropyl methylcellulose, gelatin or various waxes (such as, but not limited to, white, carnauba, stearyl alcohol, stearic acid, polyethylene glycol, castor wax, polyethylene glycol monostearate and triglycerides) or mixtures thereof. A preferred polymer is Eudragit™ NE 30D which is an aqueous dispersion containing 30% (w/w) of a neutral copolymer based on ethyl acrylate and methyl acrylate, and is considered a water swellable and water permeable polymer. Another preferred polymer are the co-polymers of acrylic and methacrylic acid esters (Eudragit™ RS 30D), which is not water swellable and has a low permeability to water. Another preferred polymer similar to Eudragit ™RS 30D is one based upon the same structure but which has additional ammonium groups, such as Eudragit™ RL 30D. This copolymer is not water swellable but is very permeable to water. Both Eudragit™ RS 30 D and RL 30 D are independent of pH. A short chemical description of the preferred polymers, such as Eudragit™ RS 30D, RL 30D and NE 30D, produced by Rohm Pharma GMBH, Weiterstadt is shown below. Poly(ethylacrylate, 1: 2: 0.2 150,000 RL 30D (30% dispersio methylmethacrylate) trimethyl- RL 100 ( granules ) ammonioethylmethacrylate chloride R = CH2-CH2-N+(CH 3 )3C1- Poly(ethylacrylate, 1: 2: 0.1 150,000 RS 30D (30% dispersio methylmethacrylate) trimethyl- RS 100 ( granules ) ammonioethylmethacrylate chloride R = CH2-CH 2 -N+(CH3)3Cr- A preferred usage of these copolymers in the instant invention is to mix Eudragit™ RS 30D and Eudragit™ RL 30D in ratios from 0 to 100% w/w to produce the desired release profile. A preferred ratio of RS 30D to RL 30D (for matrix use) is from 95:5 to 60:40. Another preferred combination is to mix Eudragit™ RS 30D and Eudragit™ NE 30D in ratios of 0 to 100% w/w as well. The preferred ratios of Eudragit™ RS 30D to NE30D (for matrix use) are from 95:5 to 50:50, more preferably 85:15. The polymers can be used alone, or in combination to produce a delayed (or controlled) release of the H2 antagonist either by incorporation into the matrix granulation and optionally with overcoating the matrix cores by the copolymers. For instance, if Eudragit™ NE 30D is the copolymer used for the matrix granulation core then Eudragit™ RS 30D may be used as the copolymer for over-coating. Alternatively, Eudragit™ RS 30D could be used for the matrix granulation core material and the overcoating copolymer may be Eudragit™ NE 30D. Preferably the matrix granulation polymer is present in an amount of 10 to 20% (w/w) of polymer relative to the H2 antagonist or cimetidine (based upon dry weight of polymer). The matrix granulation core w/w % is dependent upon the concentration of the polymer suspension. For instance, the preferred polymer Eudragit™ NE 30D is available as aqueous dispersion containing 30% (w/w) of the neutral copolymer as well as a 40% and a 50% concentration. As cimetidine is fairly soluble in water, the amount of suspension which can be used is restricted as the granulation becomes overwet. If a more concentrated suspension is used a higher level of polymer may be obtained in the matrix bead. If more polymer is used there will be a decrease in the amount of cimetidine available. Yet another factor for ultimately determining the correct percentage of polymer used in the matrix granulation is the amount of retardant or release-delaying substance applied. An increase of release-delaying substance would decrease the amount of polymer used in the matrix granulation. A preferred embodiment of the present invention is a matrix granulation core containing 12% w/w of polymer. If the matrix core is coated with a release-delaying substance of the type which causes a slow release (as opposed to a delayed release), the preferred percentage of polymer used will be from about 2 to about 30%, preferably from about 2 to about 20%. A slow release overcoating w/w % would preferably be from about 2 to about 20% as well. More preferably about 10%. A further preferred embodiment of the present invention is a matrix granulation core which is overcoated with a retardant ( or delayed release) polymer. Similar preferred ratios of polymers are those noted above. The formulations of the present invention may further comprise additional excipients and agents well known in the coating art such as: 1) plasticisers, e.g. acetylated monoglycerides, diethyl phthalate, triacetin. citric esters such as triethyl citrate, acetyl triethyl citrate, tributyl-citrate or acetyl tributyl citrate, propylene glycol, tributyrine, butylphthalylbutyl glycolate, glycerine, polyethylene glycols, glyceryl triacetate, dibutyl sebacate, dibutyl phthalate, castor oil or acetyl monoglyceride, polysorbates and sodium lauryl sulfate; 2) lubricants, e.g. calcium stearate, colloidal silicon dioxide, mineral oil, magnesium stearate, polyethylene glycol or talc; or 3) film disintegrating agents, e.g. lactose, saccharose, starch, cellulose, kaolin, polyvinyl alcohol or hydroxypropyl methyl cellulose. The immediate-release and modified-release phases forms of this invention suitably comprise other standard pharmaceutically acceptable carriers or excipients, for example starch, celluloses, sodium croscarmellose, sodium starch glycoate, crospovidone, polyvinyl alcohol, polyvinylpyrrolidione, gelatin, low viscosity hydroxypropyl methylcellulose, lactose, sucrose, talc, kaolin, colloidal silicon dioxide, magnesium stearate, or stearic acid. The process of producing immediate release substance is well known to those skilled in the art For instance the H2 antagonist can be granulated in accordance with standard pharmaceutical techniques; thus is can be mixed with a solution of a binding agent in a conventional mixing device or it can be subjected to fluidized bed granulation methods as known in the art. The process of producing the modified release phase is also well known to those skilled in the art and is further illustrated by means of the following examples. EXAMPLE 1 Uncoated immediate-release cimetidine pellets, un-coated matrix pellets, and immediate coated pellets are contained within a hard gelatin capsule. Manufacture of Immediate-Release Pellets Ingredients % w/w Cimetidine 85 Mi c rocrystalline Cellulose 12 Gelatin 3 Water (qs) The cimetidine and part of the microcrystalline cellulose are dry blended in a high shear mixer. Mixing is continued while a solution of the gelatin in water is added. When homogeneously massed the material is passed through an extruder and recirculated through it once. The extrudate is transferred to a Marumerizer bowl and spheronized. The rest of the microcrystalline cellulose is used as dusting powder to facilitate this stage of the process. The pellets are discharged and spread out on trays to be dried in a hot air oven. The dried pellets are screened via a 1.4mm sieve to remove oversize and via a 0.6mm sieve to remove undersized fractions. Pellets fractions between 600 microns and 1400 microns in diameter are retained. These dried uncoated immediate-release pellets therefore contain 85% of cimetidine. Coating of Immediate-Release Pellets to yield Immediate Coated Pellets Composition of coating suspension % w/w Eudragit ™L30D 51.2 Triethyl citrate 2.3 Colloidal silicon dioxide 1.2 Water 45.3 Pellets obtained as described above are coated by bottom spraying with the coating suspension in Fluidized Bed equipment until a 20% gain in weight is achieved. These coated pellets therefore contain 85/120 = 70.8% of cimetidine. The coated pellets are dried in situ before discharge, and then allowed to cure overnight at room temperature, while spread out on trays. The approximate weight of a coated pellet is about 0.8 mg. * Calculated as dry weight of polymer The cimetidine polymer matrix-pellets are prepared in similar manner to the immediate-release pellets except that the Eudragit ™NE 30 D suspension is added prior to the addition of the gelatin solution. Dried uncoated cimetidine polymeric matrix-pellets therefore contain 75% of cimetidine. Encapsulation The coated and uncoated pellets are prepared as in Example 1 are filled (encapsulated) into capsules, such that one capsule contains: 58.8 mg of uncoated immediate release pellets comprising 50 mg cimetidine; 70.6 mg of immediate coated pellets comprising 50mg cimetidine; and 266.7 mg of coated matrix pellets comprising 200 mg cimetidine. Thus two capsules provides a 600mg dose of cimetidine. EXAMPLE 2 Immediate-release cimetidine pellets, and uncoated matrix are contained within a hard gelatin capsule. Manufacture: The un-coated matrix pellets and immediate release cimetidine pellets are prepared as in Example 1. Encapsulation: These pellets are filled (encapsulated) into capsules, such that one capsule contains: 88.2mg of uncoated immediate release pellets comprising 75mg cimetidine, and 3 OOmg of uncoated matrix pellets comprising 225mg cimetidine. When prepared in accordance with these procedures, one capsule would provide a 300mg dose of cimetidine. Alternatively, the pellets may also be encapsulated such that one capsule contains : >_. 58.8 mg of uncoated immediate release pellets comprising 50mg cimetidine, and 333.3 mg of uncoated matrix pellets comprising 250mg cimetidine. EXAMPLE 3 Uncoated immediate-release cimetidine pellets, coated matrix pellets, and immediate coated pellets are contained within a hard gelatin capsule. The immediate coated cimetidine pellets and immediate release pellets are prepared as in Example 1, above. Coating of the Uncoated Polymer Matrix Pellets (Coated Matrix Pellets) The uncoated matrix cimetidine pellet is first prepared using the procedures described above in Example 1 for preparation of the un-coated Cimetidine Polymer Matrix pellets. The uncoated pellet is then coated in an analogous manner and with the same coating suspension as described in Example 1 for the immediate coated pellets. When prepared in accordance with these procedures the coated pellets contain 75/120 = 62.5% of cimetidine. Encapsulation The coated and uncoated pellets as prepared above are filled (encapsulated) into capsules, such that one capsule contains: 58.8 mg of uncoated immediate release pellets comprising 50 mg cimetidine; 141.2 mg of immediate coated pellets comprising lOOmg cimetidine; and 240.0 mg of coated matrix pellets comprising 150 mg cimetidine. Thus two capsules provides a 600mg dose of cimetidine wherein the ratio of immediate release, immediate coated and coated matrix is 1 :2:3 [50+100+150 = 300mg]. EXAMPLE 4 Uncoated immediate-release cimetidine pellets, and coated matrix pellets are contained within a hard gelatin capsule. The immediate release pellets are prepared as described above, in Example 1. The coated matrix pellets are prepared as described in Example 3. These pellets are filled (encapsulated) into capsules, such that one capsule contains: 117.6mg of uncoated immediate release pellets comprising lOOmg cimetidine, and 320mg of coated matrix pellets comprising 200mg cimetidine. Alternatively, the pellets may be encapsulated such that one capsule contains: 88.2 mg of uncoated pellets comprising 75mg cimetidine, and 360.0 mg of coated matrix pellets comprising 225mg cimetidine. EXAMPLE 5 Uncoated immediate-release cimetidine pellets, uncoated matrix pellets, coated matrix pellets, and immediate coated pellets are contained within a hard gelatin capsule. Manufacture: The uncoated matrix is prepared as described above in Example 1. The coated matrix is prepared, as described above, in Example 3. The immediate release and immediate coated release pellets are also prepared, as described above, in Example 1. Encapsulation Uncoated and coated pellets are filled into capsules such that one capsule contains : 29.4 mg of uncoated pellets comprising 25 mg cimetidine (8.3%) 35.3 mg of coated pellets (immediate-coated) comprising 25 mg cimetidine (8.3%) 133.3 mg of uncoated polymer matrix-pellets comprising 100 mg cimetidine (33.3%) 240.0 mg of coated polymer matrix-pellets comprising 150 mg cimetidine (50%). EXAMPLE 6 For systems consisting of coated matrix beads the following combinations are exemplified. The amount of coating present is expressed as a % weight gain over the granule alone. none Eudragit™ L 30D 10% Wt. gain NE 30D 10% Wt. gain RS 30D 10% Wt. gain none 10 % Wt. gain Eudragit™ L 30D 10 % Wt. gain NE 30D 10 % Wt. gain RS 30D 10 % Wt. gain none 10 % Wt. gain Eudragit™ L 30D 10 % Wt. gain NE 30D 10 % Wt. gain RS 30D 10 % Wt. gain The above description fully discloses the invention including preferred embodiments thereof. Modifications and improvements of the embodiments specifically disclosed herein are within the scope of the following claims. Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. Therefore the Examples herein are to be construed as merely illustrative and not a limitation of the scope of the present invention in any way. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

Claims: What is claimed is : 1. A phased-release oral dosage form comprising an H2 antagonist in a polymer matrix. 2. The dosage form according to Claim 1 wherein the H2 antagonist is cimetidine. 3. The dosage form according to Claim 2 which comprises a plurality of polymer matrix cores. 4. The dosage form according to Claim 3 wherein the polymer matrix is selected from the group consisting of a non-ionic neutral copolymer of ethyl acrylate and .methyl acrylate, acrylic and methacrylic acid esters, ethyl cellulose, hydroxypropyl methylcellulose, gelatin, waxes or mixtures thereof. 5. The dosage form according to Claim 4 wherein the polymer matrix is a copolymer of ethyl acrylate and methyl acrylate. 6. The dosage form according to Claim 4 wherein the polymer matrix is a co-polymer of acrylic and methacrylic acid esters. 7. The dosage form according to Claim 4 wherein the polymer matrix is a co-polymer of Eudragit™RL 30D. 8. The dosage form according to Claim 4 wherein the polymer matrix material is present in an amount of 10 to 20% (w/w) of polymer relative to cimetidine. 9. The dosage form according to Claim 4 wherein the dosage form is composed of pellets. 10. The dosage form according to Claim 9 wherein the pellets are contained in a gelatin capsule. 11. The dosage form according to Claim 4 wherein at least one of the matrixes is independently coated with a release-delaying substance. 12. The dosage form according to Claim 11 wherein the release-delaying substance is a coating agent selected from the group consisting of co-polymers based on polymethacrylic acid and methacrylates, ethyl acrylate and methyl acrylate, co-polymers of acrylic and methacrylic acid esters, co-polymers of Eudragit™RL 30D, hydroxypropyl methylcellulose phthlate, cellulose acetate phthalate, polyvinyl acetate pthtalate or mixtures thereof. 13. The dosage form according to Claim 12 wherein the coating agent is a copolymer of polymethacrylic acid and methacrylates, methacrylic acid and ethylacrylate, or co-polymers of Eudragit™RL 30D. 14. The dosage form according to Claim 13 wherein the release-delaying substance is present in an amount of from 2 to 30% (w/w) relative to the matrix-core. 15. The dosage form according to Claim 1 or 3 which further comprises an immediate release phase. 16. The dosage form according to Claim 14 wherein the phased-release phase is present in an amount of 66 to 75% (w/w) relative to the immediate release phase. 17. The dosage form according to Claim 16 wherein the matrix core is optionally coated with a release-delaying substance. 18. The dosage form according to Claim 17 wherein the immediate release phase is optionally coated. 19. A modified-release oral dosage form comprising: a) an immediate-release phase of cimetidine; b) a modified-release phase which comprises cimetidine incorporated into a polymer matrix; c) a second modified-release phase which comprises cimetidine incorporated into a polymer matrix coated with a release-delaying substance in an amount of from 2 to 30% (w/w) relative to the matrix-core; d) a third modified-release phase which comprises cimetidine coated with a release-delaying substance in an amount of from 2 to 30% (w/w) relative to the core. 20. The dosage form according to Claim 19 wherein the modified release phase is present in an amount of 66 to 75% (w/w) relative to the immediate release phase. 21. The dosage form according to Claim 20 wherein the polymer matrix material is present in an amount of 10 to 20% (w/w) of polymer relative to cimetidine. 22. A phased-release oral dosage form comprising: a) an immediate-release phase of cimetidine; b) an immediate coated release phase of cimetidine; c) a modified-release phase which comprises cimetidine incorporated into a polymer matrix optionally coated with a release-delaying substance in an amount of from 2 to 30% (w/w) relative to the matrix-core. 23. A process for producing a phased release oral dosage form which process comprises granulating an H 2 receptor antagonist in a polymer matrix. 24. The process according to Claim 24 wherein the H2 antagonist is cimetidine. 25 ' . The process according to Claim 24 which comprises a plurality of polymer matrix cores. 26. The process according to Claim 25 wherein the polymer matrix is selected from the group consisting of a non-ionic neutral copolymer of ethyl acrylate and methyl acrylate, acrylic and methacrylic acid esters, ethyl cellulose, hydroxypropyl methylcellulose, gelatin, waxes or mixtures thereof.

Inventors: MARSHALL KEITH, THIELE WILLIAM JAY, MARSHALL, KEITH, THIELE, WILLIAM, JAY
Applicants: SMITHKLINE BEECHAM CORP, SMITHKLINE BEECHAM CORPORATION
Application year: 1991
Main classification: A61K9
IPC codes: A61K9, A61K31, A61K47, A61P43