Controlled release matrix for pharmaceuticals

Abstract: The controlled release of therapeutically active agents is achieved from a controlled release matrix of sodium alginate and a calcium salt. When the composition is to be administered rectally, the matrix is combined with a therapeutically active agent and a suitable suppository base. When the composition is to be administered orally, the matrix further includes a higher aliphatic alcohol.

Description: Sustained release dosage forms are central in the search for improved therapy, both through improved patient compliance and decreased incidences of adverse drug reactions. Ideally, a controlled release dosage form will provide therapeutic concentration of the drug in blood that is maintained throughout the dosing interval with a reduction in the peak/nadir concentration ratio. Central to the development process are the many variables that influence the in-vivo release and subsequent absorption of the active ingredients from the gastrointestinal tract. Controlled release formulations known in the art include specially coated beads or pellets, coated tablets and ion exchange resins, wherein the slow release of the active drug is brought about through selective breakdown of the coating of the preparation or through formulation with a special matrix to affect the release of the drug. Some controlled release formulations provide for sequential release of a single dose of an active medicament at predetermined periods after administration. It is the aim of all controlled release preparations to provide a longer duration of pharmacological response after the administration of the dosage form than is ordinarily experienced after the administration of an immediate release dosage form. Such extended periods of response provides for many inherent therapeutic benefits that are not achieved with short acting, immediate release products. Thus, therapy may be continued without interrupting the sleep of the patient, which is of special importance when treating an epileptic patient to prevent nocturnal seizures, or patients with pain who experience severe pain on awakening, as well as for debilitated patients for whom an uninterrupted sleep is essential. Another critical role for extending the duration of action of medications is in therapy of cardiovascular diseases wherein optimal peak blood levels of a medication must be maintained at steady state level in order to achieve the desired therapeutic effect. Unless conventional immediate release dosage forms are carefully administered at frequent intervals, peaks and valleys in the blood level of the active drug occur because of the rapid absorption and systemic excretion of the compound and through metabolic inactivation, thereby producing special problems in maintenance therapy of the patient. A further general advantage of longer acting drug preparations is improved patient compliance resulting from the avoidance of missed doses through forgetfulness. The prior art teaching of the preparation and use of compositions providing for controlled release of an active compound from a carrier is basically concerned with the release of the active substance into the physiologic fluid of the alimentary tract. However, it is generally recognized that the mere presence of an active substance in the gastrointestinal fluids does not, by itself, insure bioavailability. Bioavailability, in a more meaningful sense, is the degree, or amount, to which a drug substance is absorbed into the systemic circulation in order to be available to a target tissue site. To be absorbed, an active drug substance must be in solution. The time required for a given proportion of an active drug substance contained in a dosage unit to enter into solution in appropriate physiologic fluids is known as the dissolution time. The dissolution time of an active substance from a dosage unit is determined as the proportion of the amount of active drug substance released from the dosage unit over a specified time by a test method conducted under standardized conditions. The physiologic fluids of the gastrointestinal tract are the media for determining dissolution time. The present state of the art recognizes many satisfactory test procedures to measure dissolution time for pharmaceutical compositions, and these test procedures are described in official compendia world wide. Although there are many diverse factors which influence the dissolution of a drug substance from its carrier, the dissolution time determined for a pharmacologically active substance from a specific composition is relatively constant and reproducible. Among the different factors affecting the dissolution time are the surface area of the drug substance presented to the dissolution solvent medium, the pH of the solution, the solubility of the substance in the specific solvent medium, and the driving forces of the saturation concentration of dissolved materials in the solvent medium. Thus, the dissolution concentration of an active drug substance is dynamically modified in this steady state as components are removed from the dissolution medium through absorption across the tissue site. Under physiological conditions, the saturation level of the dissolved materials is replenished from the dosage form reserve to maintain a relatively uniform and constant dissolution concentration in the solvent medium, providing for a steady state absorption. The transport across a tissue absorption site in the gastrointestinal tract is influenced by the Donnan osmotic equilibrium forces on both sides of the membrane, since the direction of the driving force is the difference between the concentrations of active substance on either side of the membrane, i.e. the amount dissolved in the gastrointestinal fluids and the amount present in the blood. Since the blood levels are constantly being modified by dilution, circulatory changes, tissue storage, metabolic conversion and systemic excretion, the flow of active materials is directed from the gastrointestinal tract into the blood stream. Notwithstanding the diverse factors influencing both dissolution and absorption of a drug substance. A strong correlation has been established between the in-vitro dissolution time determined for a dosage form and the in-vivo bioavailability. this correlation is so firmly established in the art that dissolution time has become generally descriptive of bioavailability potential for the active component of the particular dosage unit composition. In view of this relationship, it is clear that the dissolution time determined for a composition is one of the important fundamental characteristics for consideration when evaluating controlled release compositions. Certain controlled release pharmaceutical compositions for oral administration consisting of a release matrix of sodium alginate and calcium salts have been discussed in the art. For example, in vitro evaluations of floating alginate gel-systems consisting of sodium alginate, calcium phosphate, sodium bicarbonate, drug and diluent filled in a gelatin capsule have been reported by Protan. Protan also reports that a method for treatment of diabetes by encapsulating islets of Langerhans in calcium alginate beads coated with a semi-permeable membrane have been developed. US-Patent No. 4,717,713 discloloses a controlled release pharmaceutical composition comprising a normally liquid formulation containing a solution or suspension vehicle selected from the group consisting essentially of xanthan gum, sodium alginate, gelatin, carrageenan, methylcellulose and mixtures thereof in a amount from about 0.3 to about 5.0 percent by weight and an pharmaceutically active agent, said vehicle forming a semi-solid gel-like matrix in the environment of the stomach thereby controlling the release of said pharmaceutically active agent. SUMMARY OF THE INVENTION An object of the present invention is to provide a new controlled release matrix which extends the time of release of active medicaments incorporated therein. It is another object of the present invention to provide controlled release matrix compositions which are useful for all types of pharmaceutically active ingredients and which can extend the time of release of all such ingredients. In accordance with the above objects and other, the present invention is directed to controlled release compositions for the controlled release of therapeutically active ingredients over a pre-determined period of time, e.g. from five hours to as much as 24 hours after administration in human or animals. More particularly the present invention is related to a controlled release pharmaceutical composition for oral administration, comprising a controlled release matrix comprising a pharmaceutically acceptable sodium alginate, a pharmaceutically acceptable calcium salt which cross-links with the sodium alginate when the composition is exposed to aqueous solutions, an effective amount of a higher aliphatic alcohol, and an effective amount of an active agent distributed or suspended in said controlled release matrix. The amount of higher aliphatic alcohol included is sufficient to obtain a desired rate of release of the active agent. The higher aliphatic alcohol preferably contains from about 8 to about 18 carbon atoms. The present invention is further related to a controlled release matrix for the release of an orally administered therapeutically active agent, comprising from about 10 to about 50 percent by weight of a pharmaceutically acceptable sodium alginate, a sufficient amount of a pharmaceutically acceptable calcium salt to cross-link with the sodium alginate when the matrix is exposed to aqueous solutions or gastric fluid, and an effective amount of a higher aliphatic alcohol to obtain a desired rate of release of an active agent to be incorporated into the matrix. DETAILED DESCRIPTION An important aspect of the present invention is related in part to the realization that a controlled release matrix for the oral administration of a wide variety of therapeutically active agents is obtained from the combination of a pharmaceutically acceptable sodium alginate, a pharmaceutically acceptable calcium salt, and a higher aliphatic alcohol. Among the different factors affecting the dissolution time are the surface area of the drug substance presented to the dissolution solvent medium, the pH of the solution, the solubility of the substance in the specific solvent medium, and the driving forces of the saturation concentration of dissolved materials in the solvent medium. In the case of an orally administered drug, the physiologic fluids of the gastrointestinal tract are the media for determining dissolution time. Any pharmaceutically acceptable sodium alginate may be used in conjunction with the present invention the most preferred having a viscosity range between 10 - 500 cps as a one percent solution in water. More preferably, the alginate is a sodium alginate having a viscosity of from about 40 to about 150 cps as a one percent solution. In certain preferred embodiments the alginate has a viscosity from about 40 to about 70 cps as a one percent solution, for example when the matrix of the present invention is to be used in conjunction a less soluble drug or when a faster dissolution profile is desired. In other embodiments, the alginate has a viscosity from about 70 to about 150 cps, for example when the drug to be incorporated is relatively water soluble or when a slow dissolution rate is desired. In yet other preferred embodiments, the sodium alginate has a viscosity from about 300 to about 500 cps as a one percent solution. In terms of particle size, the sodium alginate preferably has a particle size from about 45 to about 125 microns, more preferably has a particle size of 70 microns or less. Any alginates which are pharmaceutically acceptable can be used for the purposes of the present invention. Examples of commercially available alginates suitable for use in conjunction with the present invention are those that are marketed under the trade name "Protanal * " and "Keltone * ", and are available from Protan A/S, Norway and Merck & Co. Inc., New Jersey, U.S.A. respectively. The amount of alginate contained in the controlled release matrices and compositions of the present invention is dependent upon many factors, including the desired duration of action and the nature of the active drug substance to be incorporated into the composition. In general, the amount of alginate in the total composition is from about 10 to about 50 percent by weight and in certain embodiments more preferably from about 15 to about 30 percent by weight. The amount of alginate may be higher or lower depending upon the dosage regimen desired (once-a-day, twice-a-day, three times a day, etc.). Suitable calcium salts for use in the matrices and compositions of the present invention include calcium phosphate, dicalcium phosphate, calcium chloride, calcium carbonate, calcium acetate, and calcium gluconate. The amount of calcium salt in the compositions of the present invention must be sufficient to cross-link with the alginate when exposed to solutions (e.g. gastric fluid in the case of oral preparations such that a gel matrix is formed from which the drug is slowly released. Generally, in terms of the amount of sodium alginate in the composition, the amount of calcium salt is from about 2 to about 12 percent, and more preferably from about 8 to about 12 percent, by weight of the amount of sodium alginate present in the composition. In terms of the composition, the amount of calcium is generally from about 1 to about 4 percent, by weight. Generally, the controlled release compositions of the present invention provide sustained release of the drug(s) over a predetermined or a specified period of time, e.g. over a period of time from about 4-5 hours to as much as 24 hours after administration in humans or animals. The controlled release compositions of the present invention for oral administration comprise a sodium alginate, a calcium salt and a higher aliphatic alcohol containing from 8 to 18 carbon atoms, which is optionally substituted by a further aliphatic group containing from about 8 to about 18 carbon atoms. The controlled release compositions of the present invention may be administered orally in the form of tablets, capsules, etc. It is also contemplated that the compositions of the present invention may be adapted for buccal administration. Examples of suitable higher aliphatic alcohols include fatty alcohols such as lauryl alcohol, myristyl alcohol, stearyl alcohol, cetyl alcohol and cetostearyl alcohol, and mixtures thereof. The level of higher aliphatic alcohol in the oral compositions of the present invention is determined by the rate of drug release required. Generally, the compositions will contain from about 5% to about 45% (w/w), and preferably from about 102% to about 30% (w/w), of the higher aliphatic alcohol, as a proportion to the weight of the composition. The greater the amount of higher aliphatic alcohol included in the matrix, the slower the rate of release of the drug. Upon oral ingestion and contact with fluids, the compositions of the present invention swell and gel to form a matrix from which the drug is released. Since the drug is suspended or distributed throughout the composition (and consequently throughout the matrix), a constant amount of drug can be released per unit time in vivo by dispersion or erosion of the outer portions of the matrix. Any pharmaceutically accepted soluble or insoluble inert pharmaceutical filler (diluent) material can be used in the compositions of the present invention, such as monosaccharides, disaccharides, polyhydric alcohols, or mixtures thereof. Examples of inert diluents include sucrose, dextrose, lactose, microcrystalline cellulose, xylitol, fructose, sorbitol, mixtures thereof and the like. However, it is preferred that a soluble pharmaceutical filler such as lactose, dextrose, sucrose, or mixtures thereof be used. In the case of tablets, an effective amount of any generally accepted pharmaceutical lubricant, including the calcium or magnesium soaps may be added to the above-mentioned ingredients of the excipient be added at the time the medicament is added, or in any event prior to compression into a solid dosage form. Most preferred is magnesium stearate in an amount of about 0.5-3% by weight of the solid dosage form. In preparing the matrices of the present invention for oral administration, the sodium alginate, calcium salt, drug(s) and higher aliphatic alcohol can be combined together using a wet granulation technique of at least one step, to form a uniform granulate together with any of the other excipients that are required for the tableting or the capsule filling. Alternatively, the drug(s) can be combined during the process of preparing the granulate, or mixed with the granulate after it is prepared. The moist granulated mass with or without the drug(s) is then dried and then the granulate is sized using a suitable screening device, which then provides a flowable powder which can then be filled into capsules or compressed into matrix tablets or caplets. The therapeutically active agents which may be used in the compositions of the present invention include a wide variety of drugs, including both water-soluble and water-insoluble drugs. Examples of different classes of therapeutically active pharmaceutical agents that can be incorporated into the matrices of the present invention include antihistamines (e.g., dimenhydrinate, diphenhydramine (50-100 mg), chlorpheniramine and dexchlorpheniramine maleate), analgesics (e.g., aspirin, codeine, morphine (15-300 mg), dihydromorphone, oxycodone, etc.), anti-inflammatory agents (e.g., naproxyn, diclofenac, indomethacin, ibuprofen, acetaminophen, aspirin, sulindac), gastro-intestinals and anti-emetics (e.g., metoclopramide (25-100 mg)), anti-epileptics (e.g., phenytoin, meprobamate and nitrezepam), vasodilators (e.g., nifedipine, papaverine, diltiazem and nicardirine), anti-tussive agents and expectorants (e.g., codeine phosphate), anti-asthmatics (e.g. theophylline), anti-spasmodics (e.g. atropine, scopolamine), hormones (e.g., insulin, leparin), diuretics (e.g., eltacrymic acid, bendrofluazide), anti-hypotensives (e.g., propranolol, clonidine), bronchodilators (e.g., albuterol), anti-inflammatory steroids (e.g., hydrocortisone, triamcinolone, prednisone), antibiotics (e.g., tetracycline), antihemorrhoidals, hypnotics, psychotropics, antidiarrheals, mucolytics, sedatives, decongestants, laxatives, antacids, vitamins, stimulants (including apetite suppressants such as phenylpropanolamine). The above list is not meant to be exclusive. DESCRIPTION OF PREFERRED EMBODIMENTS The following examples are given to further illustrate the present invention. The scope of the invention is not, however, meant to be limited to the specific details of the examples. EXAMPLES 1-3 ORAL CONTROLLED RELEASE SYSTEM An oral controlled release composition according to the present invention was prepared with the formulation set forth in Table 1. Ingredient Weight (mg) Dimenhydrinate 75 Protanol SF/200 75 (Sodium Alginate) Calcium Phosphate 7 Lactose (spray dried) 25 Cetostearyl Alcohol 30 Magnesium Stearate 3 Talc 3 Total 218 mg The dimenhydrinate, protanol, calcium phosphate and lactose were dry blended until thoroughly mixed. Cetostearyl alcohol was added to the warmed mixed powder, and the whole was mixed thoroughly. The mixture was allowed to cool in the air, regranulated and sieved through a 16 mesh screen. The coated granules were filled in a hard gelatin capsule using talc and magnesium stearate as lubricants (capsules) or were compressed using appropriate punches (tablets). Dissolution results of Example 1, using USP paddle method, 50 rpm were then obtained in deionized water. The results are set forth in Table 2. Hour Percent of Dimenhydrinate Dissolved 1 15.00 2 29.00 3 47.00 4 70.00 5 77.00 6 91.00 In Example 2, the method of Example 1 was followed, except that the amount of cetostearyl alcohol was increased to 50 mg per capsule or tablet. Dissolution results of Examples 2, using USP paddle method, 50 rpm were then obtained in deionized water. The results are set forth in Table 3. Hour Percent of Dimenhydrinate Dissolved 1 25.00 2 34.00 3 38.00 4 53.00 6 71.00 In Example 3, the method of Example 1 was followed except the amount of dimenhydrinate was decreased to 50 mg and the amount of lactose increased to 70 mg. Dissolution results of Example 3, using USP paddle method, 50 rpm were then obtained in deionized water. The results are set forth in Table 4. Hour Percent of Dimenhydrinate Dissolved 1 22.00 2 47.00 3 82.00 4 92.00 6 100.00

Claims: A controlled release pharmaceutical composition for oral administration, comprising a controlled release matrix comprising a controlled release matrix comprising a pharmaceutically acceptable sodium alginate, a pharmaceutically acceptable calcium salt which cross-links with the sodium alginate when said composition is exposed to aqueous solutions, and a higher aliphatic alcohol containing from about 8 to about 18 carbon atoms; and an effective amount of an active agent distributed or suspended in said controlled release matrix, said higher aliphatic alcohol being in a predetermined amount to obtain a desired rate of release of said active agent from said matrix when said composition is exposed to aqueous solutions. The composition of claim 1, wherein the sodium alginate comprises from about 10 to about 50 percent by weight of said composition, and the calcium salt comprises from about 1 to about 12 percent by weight of the sodium alginate present in the composition. The composition of claim 1, wherein the sodium alginate is a amount from about 15 to about 30 percent by weight of the composition. The composition of claim 1, wherein said calcium salt is selected from the group consisting of calcium phosphate, dicalcium phosphate, calcium chloride, calcium carbonate, calcium acetate and calcium gluconate. The composition of claim 1, wherein said pharmaceutical agent is amitriptyline, atropine, chlorpromazine, codeine, diclofenac, diphenhydramine, doxylamine, ephedrine, hyoscyamine, morphine, metoclopramide, hydromorphone, naproxyn, oxycodone, papaverine, phenyl-propaolamine, propranolol, quinidine, scopolamine, theophylline, thioridazine. WM:DG:aw The composition of claim 1, further comprising one or more excipients selected from the group consisting of monosaccharides, disaccharides, polyhydric alcohols, and mixtures of the foregoing. The composition of claim 6, wherein said composition is filled into a capsule. The composition of claim 6, wherein said composition is granulated and compressed into a tablet. A controlled release matrix for the release of a orally administered therapeutically active agent, comprising from about 10 to about 50 percent by weight of a pharmaceutically acceptable sodium alginate, a sufficient amount of a pharmaceutically acceptable calcium salt to cross-link with said sodium alginate when said matrix is exposed to aqueous solutions or gastric fluid, and a predetermined amount of a higher aliphatic alcohol to obtain a desired rate of release of a active agent to be incorporated into said matrix, said higher aliphatic alcohol containing from about 8 to about 18 carbon atoms. The controlled release pharmaceutical composition of claim 1 wherein said controlled release matrix consists essentially of said sodium alginate, said calcium salt and said higher aliphatic alcohol. The controlled release matrix of claim 9, consisting essentially of said sodium alginate, said calcium salt and said higher aliphatic alcohol.

Inventors: KRISHNAMURTHY THINNAYAM N, KRISHNAMURTHY, THINNAYAM N.
Applicants: EURO CELTIQUE SA, EURO-CELTIQUE S.A.
Application year: 1992
Main classification: A61K9
IPC codes: A61K9, A61K47