Controlled Release Pharmaceutical Composition

The present invention relates to a solid controlled release pharmaceutical composition.

A "controlled release pharmaceutical composition" is one that achieves slow release of a drug over an extended period of time and extends the duration of drug action over that achieved by conventional delivery. Preferably, such a composition maintains drug level in the blood or target tissue within the therapeutic range for 8 hours or more.

A controlled (sustained) release pharmaceutical composition containing an active ingredient has many advantages over a normal release form of the same ingredient. These include a reduction of the frequency of administration, a decrease in side effects and the maintenance of effective concentrations of the active material in the blood.

Accordingly, a large number of controlled release forms have been prepared in the past few years. For example, the composition may contain a large amount of an excipient that disintegrates slowly in the stomach or intestines. Alternatively, granules or tablets containing the active ingredient may be covered with a gastro-resistant coating or with a semipermeable membrane. A further device is to mix the active ingredient with a hydrophilic polymer.

Of these controlled release forms, the use of hydrophilic polymers (in matrices for active ingredients) has been particularly successful. Amongst the most widely used of these hydrophilic polymers are hydroxyalkylcelluloses such as hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose.

It is an object of the present invention to provide a controlled release pharmaceutical composition containing a hydrophilic polymer that, in controlled release formulations, exercises better control over the release of the active ingredient than a hydroxyalkylcellulose.

Other objects and advantages of the present invention will become apparent from the following detailed description thereof.

According to the present invention, therefore, there is provided a solid, controlled release, pharmaceutical composition comprising an active ingredient incorporated in a controlled release matrix comprising a water-soluble polydextrose.

In the present specification, a "water soluble polydextrose" is a polydextrose that dissolves to a level of at least 1% (w/w) in water at 25.degree. C.

Although the polydextrose employed in the present composition may have an average molecular weight of between about 360 and 10.sup.6, preferably the polydextrose has a number average molecular weight between 1000 and 12000. Polydextrose is a non-nutritive polysaccharide, prepared by the condensation polymerisation of saccharides in the presence of polycarboxylic acid catalysts, under reduced pressure. Polydextrose is described in U.S. Pat. Nos. 3,766,105 and 3,786,794 (the contents of which documents are incorporated herein by reference) and is available from Pfizer Inc., N.Y. Commercially available polydextrose polymer is generally a low molecular weight, water-soluble, randomly bonded polymer of glucose containing minor amounts of sorbitol end groups and citric acid residues attached to the polymer by mono- and di-ester bonds. The number average molecular weight of this commercially available material is 1500, ranging from about 360 to about 20,000.

The amount of polydextrose present in the composition of this invention will be determined by a number of factors, including the active ingredient to be administered and the rate of drug release required. Preferably, however, the composition will contain between 1% and 80% (w/w), especially between 1% and 50% (w/w) of polydextrose, most especially between 2% and 40% (w/w) of polydextrose.

In addition to the polydextrose, the present composition may also include further ingredients which can contribute to the control of the active ingredient's release and are compatible with polydextrose.

Suitable materials are,

(a) Hydrophilic or hydrophobic polymers, such as gums, cellulose ethers and protein derived materials. Of these polymers, the cellulose ethers, especially hydroxyalkyl celluloses and carboxyalkylcelluloses, most especially hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose and sodium carboxymethylcellulose, are preferred.

(b) Digestible, long chain (C.sub.8 --C.sub.50, especially C.sub.8 --C.sub.40), substituted or unsubstituted hydrocarbons, such as fatty acids, fatty alcohols, glyceryl esters of fatty acids, mineral oils and waxes. Preferably the hydrocarbons have a melting point between 25.degree. and 90.degree. C. Of these long chain hydrocarbon materials, fatty alcohols, most especially C.sub.14 --C.sub.22 fatty alcohols, such as cetyl alcohol, stearyl alcohol, cetostearyl alcohol or myristyl alcohol are preferred.

(c) Polyalkylene glycols, especially polyethylene glycol.

At least one of the materials within categories (b) and (c) is particularly preferred.

When the polydextrose is combined with at least one of a digestible, C.sub.8 --C.sub.50 substituted or unsubstituted hydrocarbon and a polyalkylene glycol, the matrix itself is novel. Thus, in another aspect of the present invention, there is provided a preparation for use in the production of a solid, controlled release pharmaceutical composition comprising a matrix of polydextrose and at least one of a digestible C.sub.8 --C.sub.50 substituted or unsubstituted hydrocarbon and a polyalkylene glycol. Optionally, the matrix may also contain at least one of a hydroxyalkylcellulose and a carboxyalkylcellulose.

In a particularly preferred embodiment of the present composition, the matrix comprises polydextrose, at least one of a C.sub.12 --C.sub.36 fatty alcohol and a polyalkylene glycol and, optionally, at least one of a hydroxyalkylcellulose and a carboxyalkylcellulose. In such an embodiment the ratio of polydextrose/cellulose to fatty alcohol/glycol is preferably between 6 to 1 and 1 to 6, especially between 4 to 1 and 1 to 4. Preferably a C.sub.14 --C.sub.22 fatty alcohol is employed.

This matrix is also a novel composition and, therefore, according to a further aspect of the present invention, there is provided a preparation for use in the production of a solid, controlled release, pharmaceutical composition comprising a matrix of polydextrose, at least one of a C.sub.12 --C.sub.36 fatty alcohol and a polyalkylene glycol and, optionally, at least one of a hydroxyalkylcellulose and a carboxyalkylcellulose. Preferably the matrix comprises a C.sub.14 --C.sub.22 fatty alcohol.

In addition to the above materials, the present controlled release composition may also contain excipients such as binders, disintegrating agents, colours, flavours, preservatives, stabilisers, glidants and lubricants, the use of which will be known to those skilled in the pharmaceutical art.

Although the present controlled release composition may be in any solid dosage form, for example, a suppository or a pessary, it is preferably adapted for oral administration. In the present specification "oral administration" incorporates buccal and sublingual administration. Thus, the preferred oral dosage forms include tablets, buccal tablets, sublingual tablets, pills, lozenges, capsules containing, for example, granules or pellets, and dragees.

Any active ingredient that may be administered by the oral, buccal, sublingual, rectal or vaginal routes may be employed in the controlled release composition of this invention. Those medicaments having a biological half-life below about 8 hours, however, are particularly suitable for incorporation in the present composition.

Examples of active ingredients that may advantageously be incorporated in the present composition are,

(1) Anti-allergic drugs, such as cyclizine, dimethindene maleate and triprolidine hydrochloride,

(2) Anti-diabetic drugs, such as chlorpropamide, glibenclamide, metformin and tolbutamide,

(3) Hormones,

(4) Antiarrhythmic agents, such as disopyramide, procainamide, propranolol and quinidine,

(5) Anti-inflammatory agents, such as aspirin, diclofenac sodium, flurbiprofen, ibuprofen, indomethacin, ketoprofen, naproxen and phenylbutazone,

(6) Antiemetic drugs, such as metoclopramide,

(7) Diuretics, such as amiloride, bendrofluazide, bumetanide, cyclopenthiazide, ethacrynic acid, frusemide, hydrochlorothiazide, triampterene, chlorthalidone and spironolactone,

(8) Anti-anginal agents, such as nitroglycerin, isosorbide dinitrate, pentaerythritol tetranitrate, verapamil and diltiazem,

(9) Vasodilators, such as nifedipine, naftidrofuryl oxalate, and nicardipine,

(10) Antihypertensive agents, such as clonidine, indoramin, guanethidine, methyldopa, oxprenolol, captopril, hydralazine and propranolol,

(11) Bronchodilators, such as salbutamol, isoprenaline and terbutaline,

(12) CNS stimulants, such as caffeine and amphetamine,

(13) Anti-histamines, such as clemastine fumarate, mepyramine, chlorpheniramine, brompheniramine, diphenhydramine.

(14) Analgesic agents, such as morphine, codeine, phenazocine, dihydrocodeine, hydromorphone, meptazinol, phenacetin, pethidine, paracetamol, oxycodone, diamorphine, nalbuphine, buprenorphine, and mefenamic acid,

(15) Vitamins, such as Vitamin B1, Vitamin B2, Vitamin B6, Vitamin C and Vitamin E,

(16) Antidepressants, such as lofepramine, amitriptyline, doxepin, maprotiline, imipramine, desipramine and mianserin,

(17) Tranquilisers, such as chlordiazepoxide and diazepam,

(18) Hematinic agents, such as ferrous fumarate,

(19) Respiratory stimulants, such as nikethamide,

(20) Antibacterial agents, such as polymyxin, streptomycin, sulphonamides, penicillins, erythromycin, cephalosporins, nalidixic acid, tetracyclines, hexamine salts, gentamicin and nitrofurantoin,

(21) Hypnotic agents such as barbiturates, dichloral phenazone, nitrazepam and temazepam,

(22) Antiviral agents, such as idoxuridine,

(23) Vasoconstrictors, such as angiotensin amide, dihydroergotamine, and ergotamine,

(24) Topical anaesthetics, such as benzocaine,

(25) Anticholinergic agents, such as scopolamine, atropine and propantheline,

(26) Adrenergic drugs, such as phenylephrine hydrochloride, phenylpropanolamine hydrochloride and pseudoephedrine,

(27) Anthelmintic agents, such as diethylcarbamazine,

(28) Corticosteroids, such as dexamethasone, prednisone, prednisolone and triamcinolone acetonide,

(29) Inorganic drugs, such as lithium carbonate, potassium chloride and lithium sulphate,

(30) Antacids, such as aluminium trisilicate and aluminium hydroxide,

(31) Antiulcer agents, such as cimetidine and ranitidine,

(32) Cofactors, such as nicotinic acid,

(33) Antipsychotic agents, such as thioridazine, trifluoperazine, fluphenazine and haloperidol,

(34) Laxatives, such as bisacodyl and magnesium hydroxide,

(35) Antiperistaltic agents, such as diphenoxylate,

(36) Anticoagulant agents, such as warfarin,

(37) Haemostatic agents, such as epsilon-aminocaproic acid,

(38) Antinauseant agents, such as metoclopramide, pyridoxine and prochlorperazine,

(39) Anticonvulsant agents, such as sodium valproate and phenytoin sodium,

(40) Neuromuscular drugs, such as dantrolene sodium,

(41) Hypoglycaemic agents, such as chlorpropramide, glucagon and tolbutamide,

(42) Thyroid drugs, such as thyroxine, triiodothyronine and propylthiouracil,

(43) Uterine relaxant, such as ritodrine,

(44) Appetite suppressants, such as phentermine, diethylpropion HCl and fenfluramine HCl,

(45) Erythropoietic substances, such as folic acid, calcium gluconate, and ferrous sulphate,

(46) Expectorants, such as carbocisteine and, guiaphenesin,

(47) Cough suppressants, such as noscapine, dextromethorphan and oxycodone,

(48) Antiuricaemic drugs, such as allopurinol, probenecid and sulphinpyrazone,

When the present controlled release matrix contains polydextrose, but no digestible, long chain substituted or unsubstituted hydrocarbon or polyalkylene glycol, the active ingredient is preferably a water-insoluble drug. In the present specification, a water insoluble drug is a drug that dissolves in water (pH 5) at 20.degree. C. to a concentration of less than 1.0 mgml.sup.-1, preferably less than 0.5 mgml.sup.-1.

According to another feature of the present invention, the solid, controlled release, pharmaceutical composition is prepared by mixing an active ingredient with a water soluble polydextrose, optionally in the presence of one or more of the following excipients, a hydrophilic or hydrophobic polymer (other than polydextrose), a digestible long chain, substituted or unsubstituted hydrocarbon, a polyalkylene glycol, a binder, a disintegrating agent, a granulating aid, a colour, a flavour, a preservative, a stabiliser, a lubricant and a glidant.

Preferably, the active ingredient is mixed with polydextrose and, at least, a C.sub.12 --C.sub.36 fatty alcohol, especially a C.sub.14 --C.sub.22 fatty alcohol such as cetyl alcohol, stearly alcohol, cetostearyl alcohol or myristyl alcohol, and/or a polyalkylene glycol, especially polyethylene glycol.

In a particularly preferred embodiment of this feature of the invention a solid, controlled release, pharmaceutical composition, in unit dosage form and for oral administration (as hereinbefore defined), is prepared by granulating an active ingredient with a water soluble polydextrose and, optionally, mixing with one or more of the following excipients, a hydrophilic or hydrophobic polymer (other than polydextrose), a digestible, long chain, substituted or unsubstituted hydrocarbon, a polyalkylene glycol, a binder, a disintegrating agent, a colour, a flavour, a preservative, a stabiliser, a lubricant, a glidant, to form granules and compressing the granules to give an oral, solid, unit dosage form containing a predetermined, therapeutically active, quantity of the active ingredient.

Depending on the particular case, the method of preparation of the granules may involve for example wet granulation or direct compression.

Preferably, the active ingredient is granulated with polydextrose and the granules formed are mixed with a C.sub.12 --C.sub.36 fatty alcohol, especially a C.sub.14 --C.sub.22 fatty alcohol such as cetyl alcohol, stearyl alcohol, cetostearyl alcohol or myristyl alcohol, and/or a polyalkylene glycol, especially polyethylene glycol.

Once the oral, solid unit dosage form has been prepared it may, if desired, be coated for example, with a gastro-resistant coating.

In a further, particularly preferred embodiment of this feature of the invention a solid, controlled release, pharmaceutical composition in the form of a capsule is prepared by pelletising, spheronising or granulating an active ingredient with a water-soluble polydextrose and, optionally, one or more of the optional ingredients employed in the preparation of the oral, unit dosage form above, to form pellets, spheroids or granules and encapsulating the pellets, spheroids or granules to give a capsule containing a predetermined, therapeutically active, quantity of the active ingredient.

Prior to filling the capsule with the pellets, the spheroids or the granules, the pellets/spheroids/granules may be coated, for example with a gastro-resistant coating.

According to another feature of the present invention, there is provided a process for the preparation of a matrix for admixture with an active ingredient to form a controlled release pharmaceutical composition comprising mixing a water soluble polydextrose with at least one of a digestible, C.sub.8 --C.sub.50 substituted or unsubstituted hydrocarbon and a polyalkylene glycol. Preferably the polydextrose is mixed with at least one of a C.sub.12 --C.sub.36 fatty alcohol (especially C.sub.14 --C.sub.22) and a polyalkylene glycol, especially polyethylene glycol. The mixing stage is preferably a granulation step.

Once the matrix has been granulated it can then be mixed with a predetermined amount of the active ingredient and, optionally compressed, to give a controlled release pharmaceutical composition according to this invention.

Predetermined release patterns of unusually reliable and constant characteristics can be secured using the present composition. This is often very important medically, especially when treating patients having coronary diseases, such as angina pectoris, or related problems, such as circulatory disorders or abnormal blood pressure, or when treating psychotropic disorders, such as manic depression or schizophrenia or when treating bronchial disorders or moderate to severe pain. The present composition may also be extremely useful in the treatment of ulcerated tissues or mucous lesions and other conditions which arise from local hyperacidity or metabolic dysfunction in the physiological system. The present composition is therefore extremely versatile and adaptable giving a wide range of application and end use.

The present solid, controlled release, pharmaceutical composition, together with methods for its preparation will now be described by way of example only, with particular reference to the Figures in which,

FIG. 1 illustrates the control exercised over theophylline release by polydextrose, as measured by in vitro dissolution,

FIG. 2 compares the release rates of two theophylline controlled release formulations, one containing hydroxyethylcellulose, the other polydextrose,

FIG. 3 compares the release rates of two pyridoxine hydrochloride controlled release formulations, one containing hydroxyethylcellulose, the other polydextrose, and

FIG. 4 compares the release rates of two metoclopramide hydrochloride controlled release formulations, one containing hydroxyethylcellulose, the other polydextrose.

Anhydrous theophylline (40 gm) was dry mixed with anhydrous lactose (15 gm), microcrystalline cellulose (5 gm) and crosslinked carboxymethyl cellulose (2 gm; Croscarmellose). The mixture was granulated with water until a wet granular mass was obtained. The wet material was then sieved through a 16 mesh screen. The granules were then dried in a Fluid Bed Dryer (FBD) at 60.degree. C. Finally, magnesium stearate (0.5 gm) was added to and mixed with the granules, which were then compressed to give 100 tablets each containing,

Anhydrous theophylline (40 gm) was wet granulated with polydextrose (2.5 gm) and the granules were sieved through a 16 mesh screen. The granules were then dried in an FBD at 60.degree. C. Talc (1.0 gm) and magnesium stearate (1.0 gm) were then added and mixed with the granules. The granules were then compressed to give 100 tablets each containing,

A comparison of the release rates of theophylline from tablets prepared as described in Examples 1 and 2 is shown in FIG. 1. The dissolution rates were measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5).

Anhydrous theophylline (40 gm) was wet granulated with hydroxyethylcellulose (2.5 gm; Natrosol 250HX, Trade Mark) and the granules were sieved through a 16 mesh screen. The granules were then dried in a FBD at 60.degree. C.

To the warmed theophylline containing granules was added a molten mixture of polyethylene glycol (PEG) 6000 (5.0 gm) and, cetostearyl alcohol (4.0 gm). This mixture was allowed to air cool and then passed through a 16 mesh screen.

Talc (1.0 gm) and magnesium stearate (1.0 gm) were then mixed with the granules. The granules were compressed to give 100 tablets each containing,

The procedure of Example 3 was followed except that polydextrose replaced the hydroxyethylcellulose. This gave 100 tablets, each containing

A comparison of the release rates of theophylline from tablets prepared as described in Examples 3 and 4 is shown in FIG. 2. The dissolution rates were measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5).

Pyridoxine hydrochloride (10 gm) and hydrogenated castor oil (1.5 gm) were granulated with hydroxyethylcellulose (2.0 gm, Natrosol 250HX) and the granules were sieved through a 16 mesh screen and dried in a FBD at 60.degree. C.

To the pyridoxine HCl containing granules, molten cetostearyl alcohol (3.5 gm) was added. This mixture was allowed to air cool and then passed through a 16 mesh screen.

Talc (0.3 gm) and magnesium stearate (0.1 gm) were mixed with the granules. This mixture was compressed to give 100 tablets each containing.

The procedure of Example 5 was followed except that polydextrose replaced the hydroxyethylcellulose. This gave 100 tablets each containing.

A comparison of the release rates of pyridoxine HCl from tablets prepared as described in Examples 5 and 6 is shown in FIG. 3. The dissolution rates were measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5).

Metoclopramide HCl (3 gm) was wet granulated with anhydrous lactose (17 gm) and hydroxyethylcellulose (2 gm; Natrosol 250HX) and the granules were sieved through a 16 mesh screen. The granules were then dried in an FBD at 60.degree. C.

To the warmed metoclopramide containing granules was added molten cetostearyl alcohol (7 gm). The mixture was allowed to air cool and then passed through a 16 mesh screen.

Talc (0.6 gm) and magnesium stearate (0.4 gm) were mixed with the granules. The granules were then compressed to give 100 tablets each containing,

Anhydrous lactose (17 gm) and polydextrose (2 gm) were dry mixed. Molten cetostearyl alcohol (7 gm) was added to the dry mixed powders. The mixture was allowed to cool and passed through a 16 mesh screen.

Metoclopramide HCl (3 gm), talc (6 gm) and magnesium stearate (4 gm) were then mixed with the polydextrose/wax granules and then compressed to give 100 tablets each containing,

A comparison of the release rates of metoclopramide HCl from tablets prepared as described in Examples 7 and 8 is shown in FIG. 4. The dissolution rates were measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5).

Anhydrous theophylline (40 gm) was wet granulated with polydextrose (21.8 gm) and the granules were sieved through a 16 mesh screen. The granules were dried in a FBD at 60.degree. C.

To the warmed theophylline containing granules was added a molten mixture of polyethylene glycol 6000 (2.9 gm), polyethylene glycol 1000 (1.45 gm) and cetostearyl alcohol (2.9 gm). This mixture was allowed to air cool and then passed through a 16 mesh screen.

Talc (1.0 gm) and magnesium stearate (0.45 gm) were then mixed with the granules. The granules were compressed to give 100 tablets each containing,

The in-vitro dissolution rate of these tablets were measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5). Results are shown in Table 1.

Naproxen (50 gm), dicalcium phosphate (16.4 gm), lactose (2.5 gm), polydextrose (2.0 gm) and hydroxypropylmethylcellulose (2.0 gm) were wet granulated and the granules were sieved through a 16 mesh screen. The granules were then dried in a FBD at 50.degree. C. Talc (1.35 gm) and magnesium stearate (0.75 gm) were then added and mixed with the granules. The granules were then compressed to give 100 tablets each containing

The in-vitro dissolution rate of these tablets was measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 7.2). Results are shown in Table 2.

Naproxen (50 gm), lactose (11.25 gm), polydextrose (0.75 gm) and povidone (2.0 gm) were wet granulated and the granules were sieved through a 16 mesh screen. The granules were dried in a FBD at 60.degree. C. Talc (1.2 gm) and magnesium stearate (0.6 gm) were mixed with the granules. The granules were compressed to give 100 tablet cores each containing,

The tablet cores were then coated with a aqueous formulation (100 ml) containing polyvinylacetate phthalate (15 gm) and 0.88 ammonia solution (0.18 ml) until the cores were coated with about 20 mg (dry weight) of coat.

The in-vitro dissolution rate of these tablets was measured by placing the tablets in 0.1N hydrochloric acid for 2 hours and thereafter continuing the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer pH 7.2. Results are shown in Table 3.

Polydextrose (28 gm) was mixed with a mixture of molten cetostearyl alcohol (6 gm) and polyethylene glycol 4000 (6 gm). The granules were allowed to cool and sieved through a 20 mesh screen.

Theophylline (40 gm) was granulated with a solution of povidone (1.2 gm) in water. The granules were sieved through a 12 mesh screen and dried in a fluid bed drier. The granules were then sieved through a 20 mesh screen.

The theophylline granules and the polydextrose/wax granules were dry mixed with purified talc (0.6 gm). Prior to compression, magnesium stearate (0.6 gm) and purified talc (0.6 gm) were mixed with the granules. This mixture was then compressed to give 100 tablets each containing,

The in-vitro dissolution rate of these tablets was measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5). Results are shown in TABLE 4.

The procedure of Example 12 was followed except that the amounts used were chosen such that each tablet contained,

The in-vitro dissolution rate of these tablets was measured as described in Example 12. Results are given in TABLE 5.

The procedure of Example 12 was followed except that the amounts used were chosen such that each tablet contained,

The in-vitro dissolutin rate of these tablets was measured as described in Example 12. Results are given in TABLE 6.

The procedure of Example 12 was followed except that the amounts used were chosen such that each tablet contained,

The in-vitro dissolution rate of these tablets was measured as described in Example 12. Results are given in TABLE 7.

Theophylline (40 gm) and polydextrose (21.8 gm) were mixed and granulated with water. The granules were dried in a fluid bed drier. The dried granules were sieved through a 16 mesh screen. The dried granules were mixed with a molten (70.degree. C.) mixture of PEG 6000 (2.9 gm) and octyl alcohol (2.9 gm). The "waxed" granules were then cooled, before blending with talc (1.0 gm) and magnesium stearate (0.4 gm). Compression of the granules gave 100 tablets each containing,

The procedure of Example 16 was followed except that the octyl alcohol was replaced by, respectively, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol and cetostearyl alcohol.

Polydextrose (12.6 gm) was mixed with molten cetostearyl alcohol (5.4 gm). The granules were allowed to cool and sieved through a 20 mesh screen.

Metoclopramide HCl (3.0 gm) was dry mixed with the polydextrose/alcohol granules and purified talc (0.21 gm). Prior to compression, magnesium stearate (0.21 gm) and purified talc (0.21 gm) were mixed with the granules. This mixture was then compressed to give 100 tablets each containing,

The procedure of Example 23 was followed except that the amounts used were chosen such that each tablet contained,

The procedure of Example 23 was followed except that the amounts used were chosen such that each tablet contained,

Salbutamol sulphate (0.964 gm), equivalent to 0.8 gm base salbutamol was wet granulated with anhydrous lactose (20.8 gm), polydextrose (1.25 gm) and povidone (0.3 gm) and the granules were sieved through a 16 mesh screen. The granules were then dried in a FBD at 60.degree. C.

To the warmed salbutamol containing granules was added molten cetostearyl alcohol (5.5 gm). The mixture was allowed to air cool and then passed through a 16 mesh screen.

Talc (0.8 gm) and magnesium stearate (0.4 gm) were mixed with the granules. The granules were then compressed to give 100 tablets each containing,

The in-vitro dissolution rate of these tablets was measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5). Results are given in TABLE 8.

The procedure of Example 26 was followed except that the amounts used were chosen such that each tablet contained,

The in-vitro dissolution rate of the tablets was measured as described in Example 26. Results are given in TABLE 9.

The procedure of Example 26 was followed except that the amounts used were chosen such that each tablet contained,

The in-vitro dissolution rate of these tablets was measured by the USP Paddle Method at 100 rpm in 900 ml of aqueous buffer (pH 6.5). Results are given in TABLE 10.

Quinidine polygalacturonate (41.25 gm), lactose (4.5 gm), hydroxypropylmethyl cellulose (1.25 gm) and polydextrose (4.5 gm) were granulated with water. The granules were sieved through a 16 mesh screen and dried in a fluid bed drier. The granules were mixed with molten cetostearyl alcohol (9.0 gm) and allowed to cool. The granules were sieved through a 16 mesh screen and blended with purified talc (1.0 gm). The granules were compressed to give 100 tablets each containing,

The in-vitro dissolution rate of these tablets was measured by the USP Paddle Method at 100 rpm in 900 ml of buffer (pH 6.5). Results are given in TABLE 11.

Nifedipine (2.0 gm), lactose (8.0 gm) and polydextrose (2.0 gm) were mixed and granulated with aqueous povidone solution (0.7 gm Povidone K30). The granules were dried in a fluid bed drier. The dried granules were sieved through a 20 mesh screen before blending with purified talc (0.4 gm) and magnesium stearate (0.2 gm). The granules were compressed to give 100 tablets each containing,

The in-vitro dissolution rate of these tablets was measured by the USP Paddle Method at 100 rpm in 900 ml aqueous isopropyl alcohol (4:1 (v/v), water: i-PrOH). Results are given in TABLE 12.

A pharmacokinetic study in 3 healthy volunteers was performed on tablets prepared as described in Example 9. Samples were analysed by enzyme immunoassay. Mean plasma theophylline concentrations are given in TABLE 13.

It can therefore be seen that the composition of Example 9 exhibits excellent control over the release of theophylline in vivo.