Compositions for Treating Hypercholesterolemia

The present invention relates to methods and compositions for reducing blood cholesterol levels by oral administration of cholestyramine and polyol polyesters.

High blood cholesterol (hypercholesterolemia) is recognized as being a risk factor in cardiovascular disease which comprises a major health care problem, today. Epidemiological studies have demonstrated that, with few exceptions, populations consuming large quantities of saturated fat and cholesterol have a relatively high concentration of serum cholesterol and a high mortality rate from coronary heart disease. While it is recognized that other factors can also contribute to the development of cardiovascular disease, there appears to be a causal relationship between the concentration of serum cholesterol, in which hypercholesterolemia results in the accumulation of undesirable amounts of cholesterol in various parts of the circulatory system (arteriosclerosis) or in soft tissues (xanthomatosis), and coronary disease and coronary mortality rates.

A variety of dietary and drug regimens have been suggested for alleviating or preventing hypercholesterolemia. However, many of these have undesirable side effects or give suboptimal results. Accordingly, the search for materials which reduce blood cholesterol has continued.

In the present invention, nonabsorbable, non-digestible polyesters are used in combination with cholestyramine resin as orally-administered cholesterol-lowering compositions. In one mode, the compositions herein are additionally fortified with fat-soluble vitamins.

The use of cholestyramine resin as adjunctive therapy to diet in the management of patients with elevated cholesterol levels is noted in Remington's Pharmaceutical Sciences, 15th Ed. Mack Publishing Co. (1975) pp 733-734.

There are a considerable number of United States patents relating to the use of nonabsorbable, nondigestible polyol polyesters of the type employed herein as cholesterol lowering agents. See, especially, U.S. Pat. Nos. 3,600,186; 4,005,195; 4,005,196 (includes fat-soluble vitamins); U.S. Pat. No. 4,034,083 (with fat-soluble vitamins); in various food compositions, e.g., U.S. Pat. Nos. 4,368,213; 4,461,782; 3,579,548; and in pharmaceutical products, e.g., U.S. Pat. Nos. 3,954,976; 4,241,054; 4,264,583; and 4,382,924. Manufacturing processes for the polyol polyesters are described in U.S. Pat. Nos. 3,963,699; 4,517,360; and 4,518,772. All of these patents are incorporated herein by reference.

The present invention encompasses orally-administered compositions of matter for reducing blood cholesterol levels in humans or lower animals, comprising a mixture of:

a) cholestyramine; and

b) a nonabsorbable, nondigestible polyol polyester.

The invention also encompasses a method for reducing blood cholesterol in a patient (including both humans and lower animals) in need of such treatment, comprising orally administering to said patient a safe and effective amount of:

a) cholestyramine; and

b) a nonabsorbable, nondigestible polyol polyester; or

c) mixtures of (a) and (b).

The compositions herein can be provided in bulk form as granules, or in unit dosage forms such as tablets, capsules, effervescing granules or tablets, and the like. The compositions can contain various flavorings, extenders, tableting aids, and the like, well-known to formulators of pharmaceutical products.

In an optional embodiment, the compositions herein can be fortified with fat-soluble vitamins, since the cholestyramine and the polyol polyesters can undesirably deplete the body's stores of these vitamins.

All percentages, ratios and proportions herein are by weight, unless otherwise specified.

The cholestyramine resin used herein is a strongly basic anion exchange resin consisting of styrene-divinylbenzene copolymer with quaternary ammonium functional groups, prepared by co-polymerizing polystyrene trimethylbenzylammonium chloride through cross-linkage with divinylbenzene. Cholestyramine resin USP is commercially available under the tradenames CUEMID (MSD) and QUESTRAN (Mead-Johnson).

Cholestyramine resin, administered orally, has sometimes been associated with constipation and preparations containing cholestryamine often have an unpleasant sandy or gritty quality. Advantageously, these problems associated with cholestyramine are alleviated when the polyol polyesters are employed therewith.

The nonabsorbable, nondigestible polyol polyesters (or, simply, polyesters) employed in this invention comprise certain polyols, especially sugars or sugar alcohols, esterified with at least four fatty acid groups. Accordingly, the polyol starting material must have at least four esterifiable hydroxyl groups. Examples of preferred polyols are sugars, including monosaccharides and disaccharides, and sugar alcohols. Examples of monosaccharides containing four hydroxyl groups are xylose and arabinose and the sugar alcohol derived from xylose, which has five hydroxyl groups, i.e., xylitol. (The monosaccharide, erythrose, is not suitable in the practice of this invention since it only contains three hydroxyl groups; but the sugar alcohol derived from erythrose, i.e., erythritol, contains four hydroxyl groups and accordingly can be used.) Suitable five hydroxyl group-containing monosaccharides are galactose, fructose, and sorbose. Sugar alcohols containing six --OH groups derived from the hydrolysis products of sucrose, as well as glucose and sorbose, e.g., sorbitol, are also suitable. Examples of disaccharide polyols which can be used include maltose, lactose, and sucrose, all of which contain eight hydroxyl groups.

Preferred polyols for preparing the polyesters for use in the present invention are selected from the group consisting of erythritol, xylitol, sorbitol, glucose and sucrose. Sucrose is especially preferred.

The polyol starting material having at least four hydroxyl groups must be esterified on at least four of the -OH groups with a fatty acid containing from about 8 to about 22 carbon atoms. Examples of such fatty acids include caprylic, capric, lauric, myristic, myristoleic, palmitic, palmitoleic, stearic, oleic, ricinoleic, linoleic, linolenic, eleostearic, arachidic, arachidonic, behenic, and erucic acid. The fatty acids can be derived from naturally occurring or synthetic fatty acids; they can be saturated or unsaturated, including positional and geometrical isomers, depending on the desired physical properties (e.g., liquid of a desired viscosity or solid) of the polyol fatty acid polyester compound being prepared.

Fatty acids per se or naturally occurring fats and oils can serve as the source for the fatty acid component in the polyol fatty acid polyester. For example, rape-seed oil provides a good source of C.sub.22 fatty acids. The C.sub.16 -C.sub.18 fatty acids can be obtained from tallow, soybean oil, and cottonseed oil. Shorter chain fatty acids can be obtained from coconut, palm kernel, and babassu oils. Corn oil, lard, oil, palm oil, peanut oil, safflower seed oil, sesame seed oil, and sunflower seed oil are examples of other natural oils which can serve as the course of the fatty acid used to prepare the polyesters herein.

Preferred fatty acids for preparing the polyol polyesters herein are the C.sub.14 to C.sub.18 acids, and are most preferably selected from the group consisting of myristic, palmitic, stearic, oleic, and linoleic fatty acids. Thus, natural fats and oils which have a high content of these fatty acids represent preferred sources for the fatty acid component, i.e., soybean oil, olive oil, cottonseed oil, corn oil, tallow and lard.

The polyol fatty acid polyesters useful in this invention must contain at least four fatty acid ester groups. Polyol fatty acid polyester compounds that contain three or less fatty acid ester groups are digested in and the products of digestion are absorbed from the intestinal tract much in the manner of ordinary triglyceride fats, whereas the polyol fatty acid polyester compounds that contain four or more fatty acid ester groups are substantially nondigestible and consequently nonabsorbable by the human body. It is not necessary that all of the hydroxyl groups of the polyol be esterified with fatty acid, but it is preferable that the polyester contain no more than two unesterified hydroxyl groups. Most preferably, substantially all of the hydroxyl groups of the polyol are esterified with fatty acid, i.e., the compound is substantially completely esterified. The fatty acids esterified to the polyol molecule can be the same or mixed.

To illustrate the above points, a sucrose fatty triester would not be suitable for use herein because it does not contain the required four fatty acid ester groups. A sucrose tetra-fatty acid ester would be suitable, but is not preferred because it has more than two unesterified hydroxyl groups. A sucrose hexa-fatty acid ester would be preferred because it has no more than two unesterified hydroxyl groups. Highly preferred compounds in which all the hydroxyl groups are esterified with fatty acid include the sucrose octa-fatty acid esters.

In any given polyol fatty acid polyester compound the fatty acid ester groups can be selected on the basis of the desired physical properties of the compound. For example, the polyol polyesters which contain unsaturated fatty acid ester groups and/or a preponderance of short chain, e.g., C.sub.12, fatty acid ester groups are generally liquid at room temperature. The polyols esterified with longer chain and/or saturated fatty acid groups such as stearoyl are solids at room temperatures.

The following are nonlimiting examples of specific polyol fatty acid polyesters containing at least four fatty acid ester groups suitable for use in the present invention: glucose tetraoleate, glucose tetrastearate, the glucose tetraesters of soybean oil fatty acids, the mannose tetraesters of mixed tallow fatty acids, the galactose tetraesters of olive oil fatty acids, the arabinose tetraesters of cottonseed oil fatty acids, xylose tetralinoleate, galactose pentastearate, sorbitol tetraoleate, the sorbitol hexaesters of olive oil fatty acids, xylitol pentapalmitate, the xylitol tetraesters of substantially completely hydrogenated cottonseed oil fatty acids, sucrose tetrastearate, sucrose pentastearate, sucrose hexaoleate, sucrose octaoleate, the sucrose octaesters of partially or substantially completely hydrogenated soybean oil fatty acids and the sucrose octaesters of peanut oil fatty acids.

As noted above, highly preferred polyol fatty acid esters are those wherein the fatty acids contain from about 14 to about 18 carbon atoms and are thus derived from such natural materials as soybean oil and olive oil. Examples of such compounds are the erythritol tetraesters of olive oil fatty acids, erythritol tetraoleate, xylitol pentaoleate sorbitol hexaoleate, sucrose octaoleate, and the sucrose hexa-, hepta- and octaesters of soybean oil fatty acids, partially or substantially wholly hydrogenated.

The polyol fatty acid polyesters suitable for use herein can be prepared by a variety of methods well known to those skilled in the art. These methods include: transesterification of the polyol with methyl, ethyl or glycerol fatty acid esters using a variety of catalysts; acylation of the polyol with a fatty acid chloride; acylation of the polyol with a fatty acid anhydride; and acylation of the polyol with a fatty acid, per se. As an example, the preparation of polyol fatty acid esters is described in U.S. Pat. No. 2,831,854, incorporated herein by reference. The most highly preferred methods of preparing the polyol polyesters used herein are disclosed in U.S. Pat. Nos. 4,517,360 and 4,518,772, incorporated herein by reference.

Specific, but nonlimiting, examples of the preparation of polyol fatty acid esters suitable for use in the practice of this invention are as follows.

Erythritol tetraoleate - Erythritol and a five-fold molar excess of methyl oleate are heated at 180.degree. C., under vacuum, with agitation, in the presence of sodium methoxide catalyst over two reaction periods of several hours each. The reaction product (predominately erythritol tetraoleate) is refined in petroleum ether and crystallized three times from several volumes of acetone at 1.degree. C.

Xylitol pentaoleate - Xylitol and a five-fold molar excess of methyl oleate in dimethylacetamide (DMAC) solution are heated at 180.degree. C. for five hours in the presence of sodium methoxide catalyst, under vacuum. During this time the DMAC is removed by distillation. The product (predominately xylitol pentaoleate) is refined in petroleum ether solution and, after being freed of petroleum ether, is separated as a liquid layer four times from acetone at ca. 1.degree. C. and twice from alcohol at ca. 10.degree. C.

Sorbitol hexaoleate is prepared by essentially the same procedure used to prepare xylitol pentaoleate except that sorbitol is substituted for xylitol.

Sucrose octaoleate is prepared by substantially the same procedure as that used to prepare erythritol tetraoleate except that sucrose is substituted for erythritol.

The fat-soluble vitamins can optionally be used to fortify the foregoing polyesters. It will be appreciated that commercial preparations of the appropriate vitamins and/or appropriate vitamin mixtures which provide vitamins A, D, E and K can be used herein. See U.S. Pat. No. 4,034,083 for details of the role of these vitamins in metabolism and their use in combination with polyesters of the type used in this invention.

In general terms, the vitamins are classified as either "fat-soluble" or "water-soluble". The fat-soluble vitamins are used to fortify the polyester materials herein. The fat-soluble vitamins include vitamin A, vitamin D, vitamin E, and vitamin K.

The amount of the individual fat-soluble vitamins used to fortify the present compositions can vary with the age of the recipient, the dosage regimen used, and the amount of the vitamin ingested from other dietary sources. For example, in younger, growing children or in pregnant females it is recognized that larger amounts of any given vitamin should be ingested to supply optimal nutritional benefits than are needed with adult males. If the user of the present compositions happens to ingest foods which are extremely rich in a given fat-soluble vitamin, less of that vitamin need be used in the present compositions to insure adequate intestinal uptake for good nutrition. In any event, an attending physician can, if so desired, measure the amount of fat-soluble vitamins in the plasma. Based on these data, the appropriate type and amount of fat-soluble vitamin used to fortify the polyesters herein can then be determined on an individual basis.

More simply, the formulator of the compositions herein can fortify the polyesters with a recommended daily allowance (RDA), or increment or multiple of an RDA, of any of the fat-soluble vitamins to insure that the user of the compositions will maintain a nutritionally adequate uptake of said vitamins. For example, with vitamin A a daily amount in the range of 20 international units (I.U. to about 57 I.U. per kilogram of body weight can be employed. With vitamin D, fortification of the compositions to provide about 400 I.U., total, per day is ample. When supplementing with vitamin E, the amount of the vitamin optimal for dietary intake ranges from 3-6 I.U. for infants to 25-30 I.U. total, per day, for adults. When supplementing with vitamin K, it is more difficult to estimate the amount to be ingested to provide adequate nutrition since the microorganisms living in the intestine can synthesize this vitamin. However, it is known that ingestion of from 0.5 mg.-1 mg. of vitamin K per day will prevent insufficiency.

The treatment regimen herein comprises orally administering to a patient in need of having a lowered blood cholesterol level a safe and effective amount of the cholestyramine, and a nonabsorbable, nondigestible polyol polyester of the type described hereinabove, or, conveniently, mixtures of these two materials. Ingestion of from 10 g to 40 g of the cholestyramine and from 5 g to 50 g of the polyester material is appropriate in most circumstances. However, this can vary with the size and condition of the patient, and the patient's blood cholesterol level. Such matters will, of course, be apparent to the attending physician. However, since the cholestyramine and the polyol material are nontoxic and nonallergenic, even higher ingestion levels can be used without undue side effects.

Treatment of the patient comprises chronic ingestion in order to lower and maintain the low cholesterol levels. Daily ingestion is preferred, and a total daily ingestion of from about 12 g to about 32 g of the cholestyramine and from about 15 g to about 50 g of the polyester material is most commonly used, with said ingestion being portion-wise at two, three or four regularly spaced intervals throughout the day. Again, depending on the patient's size and cholesterol level in the patient's blood, this can be varied. Administration just before meals and at bedtime is convenient.

The preferred polyol polyesters used in the foregoing methods are: sucrose octaoleate, sucrose octalinoleate, sucrose oltapalmitate and mixtures thereof.

As mentioned, it is convenient to use the cholestyramine and the polyester as a mixture. Thus, cholestyramine is admixed with the polyester, generally in a weight ratio of about 10:1 to about 1:10, preferably 3:1 to 1:3, conveniently 1:1. The materials readily admix, particularly when a liquid polyester such as sucrose octaoleate is used, and, at a weight ratio of 1:1 the resulting mixed composition has the appearance of resinous granules. These granules can be compacted to provide tablets or capsules, or, conveniently, can be spooned-out from the bulk mixture and either administered by the spoonful or admixed with water and drunk.

The following examples are typical of the compositions of this invention, but are not intended to be limiting thereof.

The chloestyramine granules and sucrose octaoleate are blended to form a unit dose composition, Three such unit doses are ingested each day, orally, curing the course of two weeks to lower blood chloresterol. Thereafter, one dose per day is used, on a continuing basis.

While not intending to be limited by theory, it is surmised that the enhanced cholesterol lowering properties of the instant compositions are due to the differing modes of action of the two ingredients, the cholestyramine removing bile acids via the feces and the polyesters dissolving and removing cholesterol.

In an alternate mode, sucrose octaoleate is administered orally (14 g doses/3 times per day), followed by oral administration of an aqueous suspension of cholestyramine (8 g doses/3 times per day) to lower LDL lipoproteins in the blood.