Patent Application
20080305166
A rapidly disintegrating, low friable tablet formulation is provided. The tablet formulation comprises: an ethylcellulose binder which is co-formulated with typical disintegrants and other common tablet aids such as fillers and tablet lubricants and flow aids. When tested, the tablet produced from the formulation exhibited a friability of about 5% or less and disintegrated in less than about 60 seconds.
Rapidly disintegrating or fast dissolving tablets or oral dosage forms which are intended to rapidly break up and deliver an active ingredient in the oral cavity are gaining importance as a vehicle for administering nutraceutical and pharmaceutical active ingredients, especially in pediatric and geriatric populations. Generally such tablets are expected to have a very short residence time in the mouth. They should therefore disintegrate in less than 60 seconds and more ideally in less than 30 seconds when tested using a standard USP tablet disintegration test. In addition, the tablets should not provide an unpleasant mouthfeel, should not be excessively hard, in case they are chewed, and should also not have an unpleasant taste. From a manufacturing point of view, its is desirable that the tablet formulation yields mechanically robust tablets with low friability and is directly compressible, thus obviating time consuming co-processing such as granulation steps, spray drying and freeze drying. A desirable friability can be defined as less than 1% and ideally less than 0.5% weight loss on attrition in a standard friabilator.
It is common to combine an active ingredient with soluble tablet fillers especially sugar alcohols (polyols) as many of these are not only soluble and compressible, but also provide a pleasant mouthfeel and may also provide some non-calorigenic sweetening effect. Frequently used polyols include mannitol, xylitol, sorbitol and lactiol. Other soluble tablet fillers include soluble sugars and starch derivatives such as sucrose, lactose, dextrose, maltodextrin, isomalt and polydextrose.
Typically, the soluble filler, such as a sugar alcohol, is further combined with a high level (5% or more by weight) of a hydrophilic, highly swellable disintegrant, such as cross-linked povidone (crospovidone), cross-linked sodium carboxymethyl cellulose (croscarmellose sodium), cross-linked sodium carboxymethyl starch (sodium starch glycollate) or low-substituted hydroxypropyl cellulose.
However when using such a formulation approach to make directly compressible tablets, it is difficult to simultaneously minimize disintegration times, friability and hygroscopicity. For example, disintegrants as a class are generally poorly compressible and have low tablet binding efficiency and are very hygroscopic. By increasing the amount of disintegrant to shorten disintegration time, the resultant tablets exhibit an increased hygroscopicity and a lower compactibility with increased friability. Moreover in direct compression and without additives such as binders, the majority of suitable tablet fillers, as named above tend to yield only marginally robust tablets. The addition of common water soluble tablet binders such as hydroxypropylcellulose (HPC), hydroxypropylmethyl cellulose (HPMC) or povidone (PVP) tends to be ineffective or result in longer disintegration times as the binder develops viscosity, gels and retards the break-up of the wet tablet.
In summary, common disadvantages of the above formulations are that due to the nature of materials used, these formulations tend to be hygroscopic and are also relatively poorly compactable, resulting in stability issues, high friabilities and relatively poor mechanical handling properties when compared to traditional directly-compressed immediate release tablets. As many drugs are poorly directly compressible, performance of the tablets worseness as the proportion of drug in the tablet increases. Therefore, special precautions need to be taken during mass handling and packaging of rapid disintegrating tablets to protect these tablets from excessive atmospheric moisture as well as excessive mechanical forces.
Several formulation strategies have been developed. In International Patent Application WO2006058250 A1, a rapidly disintegrating oral tablet formulation comprising a combination of two sugar alcohols which are co-processed to yield non-filamentous particles is disclosed. This mixture is combined with a third supplemental sugar alcohol, disintegrants and other components such as flow aids. The formulation produces rapidly disintegrating tablets with low friability.
In U.S. Pat. No. 6,284,272, the use of effervescent agents which result in rapid tablet break up on contact with the saliva has been taught. However, effervescent agents are generally a combination of acids and bases which destabilizes many active ingredients.
U.S. Pat. No. 5,631,023 teaches a rapid disintegrating tablet made from a lyophilized mixture of actives and excipients. By freeze drying the tablet formulation, the formulation is rendered amorphous and highly porous and thus extremely water-soluble. However, freeze drying is a specialized and time consuming process and the resultant tablets are extremely hygroscopic, necessitating additional manufacturing and packaging precautions for moisture control.
US Patent Application No. 20030138369A1 discloses a grade of calcium metasilicate with low particle aspect ratio and high oil or water absorption characteristics. According to the manufactures literature, these calcium metasilicate products function as co-agents in concert with other known disintegrants when used at levels up to 30% in fast dissolve formulations. However, the addition of calcium metasilicate may result in loss of tablet robustness and compactibility. A similar effect is found when calcium metasilicate is combined with dicalcium phosphate as illustrated in Example 6 of US Patent Application No. 20050244343A1. It should also be noted that calcium silicate in general is characterized by an alkaline surface pH which may be detrimental to the stability of alkali-labile drugs. Similar use of other inorganic additives such as titanium dioxide, silica or calcium carbonate in combination with a disintegrant and a sugar alcohol has also been disclosed, as in International Patent Application WO 2005110376 A3.
U.S. Pat. No. 5,747,068 teaches materials for use in readily dissolvable tablets include specially modified starches for fast dissolve tablets. Additionally, numerous rapidly disintegrating formulations for specific drugs can be found in the literature. For instance U.S. Pat. No. 5,747,068 additionally discloses dispersible tablets comprising fluoxetine and various disintegrants and soluble fillers.
U.S. Pat. No. 6,592,901 teaches a pharmaceutical dosage form composition composed of ethylcellulose that has an ethoxyl range lower limit of 49.6%, and a viscosity of less than 53 cps. This pharmaceutical dosage form is highly-compressible and compactable and is capable of forming harder tablets or pellets with good release retardation.
There remains a need for a rapidly disintegrating mechanically robust low friable tablet formulation for fast and effective delivery of an active ingredient in the oral cavity.
The present invention relates to the use of ethylcellulose (EC) as a water-insoluble, inert tablet binder at levels of about 1 to about 20% by weight for rapid disintegrating tablets. EC is well known for its drug release retarding properties and use in non-disintegrating hydrophobic matrix tablets. However, the present invention relates to use of EC in a dosage form generally understood to require rapid disintegration and high solubility in water which is surprising, especially at the relatively high binder use of levels (e.g. 15% by weight of the tablet formulation).
More particularly, the present invention relates to a rapidly disintegrating, low friable tablet formulation comprising about 1 to 20% by weight of an ethylcellulose binder and about 2 to 15% by weight of a disintegrant. The ethylcellulose binder has an ethoxyl content in the range of 44 to 54.9% and 5% solution viscosity in the range of about 3 to 200 cps in a 80:20 toluene:ethanol solvent blend. The disintegrant is selected from the group consisting of cross-linked povidone, sodium cross carmellose (cross-linked sodium carboxymethyl cellulose), sodium starch glycollate, low-substituted hydroxypropyl cellulose, and guar.
The present invention also relates to a method for producing a rapidly disintegrating, low friable tablet. The method comprising the steps of obtaining and blending an ethylcellulose binder, a disintegrant, and optionally a filler and a flow aid to produce a mixture. Coprocessing the mixture and compressing the coprocessed mixture to form the rapidly disintegrating, low friable tablet. The coprocessing may be accomplished by either co-milling, roller compacting or though the wet agglomeration of the mixture. A lubricant may be added to the mixture prior to compression into the tablet form.
The rapidly disintegrating, low friable tablet of the present invention also can be combined with at least one active pharmaceutical ingredient.
It has been found that EC, a water-insoluble, hydrophobic cellulose ether, which is commonly used as a drug release retarding agent in barrier film coatings or hydrophobic non-disintegrating matrix tablets, can act as a synergistic tablet binder for rapidly disintegrating tablet formulations. EC, a non-hygroscopic, non-reactive tablet binder can readily be dry blended or co-processed (for example by co-milling or through use of agglomeration techniques including but not limited to roller compaction and wet granulation) with other formulation components to provide the combined attributes of fast disintegration (less than 60 seconds and frequently less than 20 seconds), relative inertness, near pH neutrality, ease of manufacturing by conventional direct compression tablet technology, and high tablet robustness as defined by low tablet friability (less than 1% and frequently less than 0.5% friable by weight).
The invention also provides for tablet formulations with low hygroscopicity prior to compression into tablets and tablets also have very low hygroscopicity, not withstanding the fast dispersion in water. Typical moisture uptake is less than 2% (on a dry weight basis) at 50% relative humidity and 25° C.
Ethylcellulose (EC) is a cellulose ether that is versatile with many uses. A preferred EC is described in U.S. Pat. No. 6,592,901, which is incorporated herein by reference in its entirety. The following grade types of EC are commercially available from Hercules Incorporated:
Types K, N, and T of EC are used in food and food contact applications. More specifically, K and T are used for food and contact such as paper or paperboard in contact with food. N types were used as a binder or coating in pharmaceutical applications. Type X is used in inks and other industrial applications. While any grade of EC is of utility in this invention, the use of optimized direct compression grades such as high ethoxyl, low viscosity EC (T10 EC Pharm grade, available from Aqualon Division, a Business Unit of Hercules Incorporated), is especially preferred. This EC type combines high compressibility with good powder flow characteristics. Other commercially available grades of EC with lower ethoxyl and lower or higher viscosity (such as N7, N10, N14, N22, N50 and N100 Pharm grade EC, all available from Aqualon Division, a Business Unit of Hercules Incorporated), while possibly less effective than T10 EC Pharm grade, are also useful in the tablet formulations of the current invention.
It is well known in the art how to make EC. Normally, either chemical grade cotton linters or wood pulp is used to prepare EC. The sequence of chemical reactions is similar to that for methylation of cellulose. In commercial practice, sodium hydroxide concentrations of 50% or higher are used to prepare the alkali cellulose. Staged additions of solid sodium hydroxide during the reactions can be used to reduce side reactions. Ethyl chloride is added to the alkali cellulose in nickel-clad reactors at 90-150° C. and 828 to 965 kPa (120 to 140 psi) for 6-12 hours. Diluents such as benzene or toluene can be used. At the end of the reaction, the volatiles such as ethyl chloride, diethyl ether, ethanol, and diluent are recovered and recycled. The ethylcellulose in solution is precipitated in the form of granules with further recovery of the carrier solvents. Washing with water completes the processing. Control of metallic impurities is important to achieve stability during storage. Anitoxidants can also be incorporated to inhibit loss of viscosity.
While any grade of EC is of utility in this invention, a preferred EC of use in the present invention has a higher ethoxyl content (greater than 49.6%) and simultaneously a low viscosity (less than 53 cps) and the average particle size is greater than 50 micrometers.
The preferred EC of use in the present invention has an ethoxyl content lower limit of 49.6%, preferably 49.8%, and more preferably 50.0%. The upper limit of the ethoxyl content of the EC is 54.88%, preferably 53.0% and more preferably and more preferably 52.0%. The viscosity of the EC is less than 53.0 cps, preferably less than 25 cps and more preferably less than about 17 cps, with a lower limit of about 3 cps.
The EC binder is co-formulated with typical disintegrants and other common tablet aids such as fillers and tablet lubricants and flow aids. Typical disintegrants include and may be selected from the group consisting of cross-linked povidone, sodium cross carmellose (cross-linked sodium carboxymethyl cellulose), sodium starch glycollate, low substituted hydroxypropyl cellulose, and guar. Low-substituted hydroxypropyl cellulose may be defined as having a hydroxypropoxyl content in the range of 5.0 to 16.0% by weight and an apparent average degree of polymerization in the range of 350 to 700. Low-substituted hydroxypropyl cellulose is disclosed in U.S. Pat. No. 6,380,381, incorporated herein by reference.
Suitable fillers include sucrose, lactose, dextrose, mannitol, xylitol, sorbitol, lactiol, maltodexrin, isomalt, polydextrose, starch and microcrystalline cellulose. Lubricants and flow aids include metal stearates, such as magnesium and calcium stearate, stearic acid, hydrogenated vegetable oils, poletheylene glycols, amino acids, stearyl fumarate, talc and colloidal silicone dioxide.
Other additives which are typically used in small amounts but are important for organoleptic enhancements include sweetners, flavors, tastemasking agents and colorants. Examples of sweeteners include sucralose, sodium saccharin, acesulfame K and aspartame. Examples of flavoring and tastemasking agents include peppermint, citrus and vanilla extracts, amino acid derivatives such as glutamic acid based derivatives. The above is not meant to be an exhaustive list of possible organoleptic enhancing aids.
Suitable use levels of EC are 1-20%, more preferably 3-18% and most preferably 5-15%.
Suitable use levels for disintegrant are 2-15%, more preferably 3-12% and most preferably 5-10%.
Suitable lubricant levels range from 0.1% to 2.5%. More preferably 0.25 to 2.0% and most preferably 0.5% to 1.5%.
While any grade of EC is of utility in this invention, the use of optimized direct compression grades such as high ethoxyl, low viscosity EC (T10 EC Pharm grade, available from Aqualon Division, a Business Unit of Hercules Incorporated), is especially preferred. This EC type combines high compressibility with good powder flow characteristics. Other commercially available grades of EC with lower ethoxyl and lower or higher viscosity (such as N7, N10, N14, N22, N50 and N100 Pharm grade EC, all available from Aqualon Division, a Business Unit of Hercules Incorporated), while possibly less effective than T10 EC Pharm grade, are also useful in the tablet formulations of the current invention.
The rapidly disintegrating, low friable tablet formulation of the present invention also can be combined with an active pharmaceutical ingredient or medicaments to prepare a formulation suitable for tableting or pelletizing. One or more active pharmaceutical ingredients may be combined in a single dosage form, depending on the chemical compatibility of the combined active ingredients and the ability to obtain the desired release rate from the dosage form for each active ingredient. The determination of the effective amount of the medicament per dosage unit is easily determined by skilled clinicians.
Representative types of active pharmaceutical ingredients include antacids, anti-inflammatory substances, anti-infectives, psychotropics, antimanics, anti-Parkinson's agents, anti-Alzheimer's agents, anti-Parkinson's agents, anti-Alzheimer's agents, stimulants, antihistamines, laxatives, decongestants, nutritional supplements, gastrointestinal sedatives, antidiarrheal preparations, antianginal drugs, antiarrhythmics, antihypertensive drugs, vasoconstrictors and migraine treatments, anticoagulants and anti-thrombotic drugs, analgesics, anti-pyretics, hypnotics, sedatives, antiemetics, anti-nauseants, anticonvulsants, neuromuscular drugs, hyper- and hypoglycemic agents, thyroid and antithyroid preparations, diuretics, antispasmodics, uterine relaxants, mineral and nutritional additives, anti-obesity drugs, anabolic drugs, erythropoietic drugs, antiasthmatics, expectorants, cough suppressants, mucolytics, antiuricemic drugs, topical analgesics, local anesthetics, polypeptide drugs, anti-HIV drugs, anti-diabetic agents, chemotherapeutic and anti-neoplastic drugs.
Examples of specific active pharmaceutical ingredients include aluminum hydroxide, prednisolone, dexamethasone, aspirin, acetaminophen, ibuprofen, isosorbide dinitrate, nicotinic acid, tetracycline, ampicillin, dexbrompheniramine, chlorpheniramine, albuterol pseudoephedrine, loratadine, theophylline, ascorbic acid, tocopherol, pyridoxine, methoclopramide, magnesium hydroxide, verapamil, procainamide hydrochloride, propranolol, captopril, ergotamine, furazepam, diazepam, lithium carbonate, insulin, furosemide, hydrochlorothiazide, guaiphenesin, dextromethorphan, benzocaine, ondansetron, cetrizine, dimenhydrinate, diphenhydramine, vitamin B12, famotidine, ranitidine, omerpazole, rabeprazole, esomeprazole, sildenafil, tadalafil, atorvastatin, simvastatin, valsartan, lorsartan, donepezil, galantamine, rivastigmine, carbidopa, levodopa, sertaline, pramipexole and ropinirole. It should be understood that any active pharmaceutical ingredients that is physically and chemically compatible with the EC of the present invention and other dosage form ingredients can be used in the present invention.
In the below mentioned examples, a cross linked CMC level of 5% by weight of the total formulation was found to be highly effective, yielding fast disintegration and low friability. It is however expected that depending on a formulation requirements e.g., drug solubility, load and desired disintegration time, the disintegrant level may vary between 2 and 15% by weight of the formulation. However, a distinguishing advantage of the current invention is that even though a formulation contains 25% of a hydrophobic drug, dimenhydrinate, the tablet none the less disintegrates in about 15 seconds while only requiring 5% by weight disintegrant—low levels of disintegrant in combination with a non-hygroscopic EC therefore decrease the hygroscopicity of the overall formulation.
Similarly, a T10 EC level of 5-10% by weight was found to be highly effective in reducing tablet friability and maintaining low disintegration time. However it is understood that depending on formulation characteristics, especially compactibility characteristics and mechanical properties and dose of drug, the level of EC binder may vary from 1 to 20% by weight of the total formulation.
The following examples will serve to illustrate the invention, parts and percentages being by weight unless otherwise indicated.
In accordance with ASTM D4794, Ethoxyl content was determined by a Zeisel (sealed) tube method by reacting EC with hydriodic acid, liberating one mole of ethyl iodide for each mole of ethoxyl substitution on the cellulose chain. The ethyl iodide was then extracted with o-xylene and quantitated by gas chromatography using toluene as an internal standard. A typical set of apparatus, reagents and procedures for this test are listed below:
Integrator parameters are given for Hewlett Packard Reporting Integrator Model 3390A.
Viscosity was determined by preparing a 5% solution of EC in a toluene:ethanol (80:20) solvent mixture. Viscosity of the solution was measured using a Hercules Horizontal Capillary Viscometer (following ASTM D914-00, 33.1). The list of apparatus, reagents and procedures are described below.
Friability is measured by placing an accurately weighed sample of 20 tablets in the drum of a standard Roche-type friabilator and rotating the drum for 250 rotations. % Friability is then calculated as the % weight loss of the de-dusted tablets after rotation relative to the same sample of tablets prior to rotation in the friabilator.
Disintegration time is measured by placing 6 tablets into a standard USP disintegration apparatus without disc inserts. The tablets are then dipped and reciprocated in a pH 6.8 phosphate buffer solution (as defined in the USP) and carefully observed and timed. Disintegration time is recorded as the time where no discernible tablet core remains and all the pieces of the disintegrated tablet have fallen through the mesh screen of the disintegration cell. The temperature of the test solution is 37° C.+/−1° C.
For all examples, the various formulation components, with exception of magnesium stearate and stearic acid, were first dry blended in a Patterson-Kelly V-type blender for 15 minutes. Magnesium stearate and stearic acid were then added to the mixture through a 20 mesh screen, and the entire mass was then blended for another 3 minutes. Tablets were then directly compressed at 37 rpm on an instrumented Manesty Beta press, equipped with ¼″ standard concave tooling, except where larger tooling is indicated. A target weight of 100 mg was set, except where a different weight is indicated. Tablets were compressed at 5 kN and approximately 8 kN of compressive force for examples using ¼″ standard concave tooling. For larger tooling, 15, 20 and 25 kN compressive force was used. For larger tooling 15, 20 and 25 kN compressive force was used. Tablet crushing strength was determined by diametrically compressing tablets using a Key Pharmatest HT500S hardness tester.
A 500 gram batch of dry blended powder without EC was prepared and then tableted into 100 mg. tablets as a control formulation:
Table 1. Resultant crushing strength, friability and disintegration times for the control formulation in example 1. Tablets were made at 5 kN and 8 kN compression force using a rotary tablet press.
The combination of mannitol and croscarmellose were able to provide relatively fast disintegration of a tablet comprising 25% of a low soluble drug, dimenhydrinate. However, tablet friability was unacceptably high at 9% weight loss.
A 500 gram batch of dry blended powder was prepared as above, however a low viscosity water soluble binder Klucel® EXF Pharm hydroxypropyl cellulose, available from Aqualon Division, a Business Unit of Hercules Incorporated was added and tableted into 100 mg. tablets:
Table 2. Resultant crushing strength, friability and disintegration times for the control formulation in example 2. Tablets were made at 5 kN and 8 kN compression force using a rotary tablet press.
Addition of hydroxypropyl cellulose was very effective in lowering friability and enhancing tablet strength but disintegration times in excess of 180 seconds resulted.
A 500 gram batch of dry blended powder was prepared as above in comparative example 2, however in place hydroxypropyl cellulose, water insoluble T10 Pharm EC, available from Aqualon Division, a Business Unit of Hercules Incorporated, was substituted in the composition and tableted into 100 mg. tablets:
Table 3. Resultant crushing strength, friability and disintegration times for the control formulation in example 1. Tablets were made at 5 kN and 8 kN compression force using a rotary tablet press.
Substitution of hydroxypropyl cellulose with T10 Pharm EC was effective in maintaining the low friability and improved tablet strength relative to control, and was also effective in maintaining a rapid disintegration time of less than 30 seconds.
A 500 gram batch of dry blended powder was prepared as above in example 1, however in place of 15% water insoluble T10 Pharm EC only 10% of T10 Pharm EC was included and tableted into 100 mg. tablets:
Table 4. Resultant crushing strength, friability and disintegration times for the control formulation in example 2. Tablets were made at 5 and 8 kN compression force using a rotary tablet press.
Reducing the EC component from 15% to 10% did not compromise low tablet friability while providing rapid disintegration times similar to those of the control.
A 500 gram batch of dry blended powder was prepared as above in example 2, however in place of 10% water insoluble T10 Pharm EC only 5% of T10 Pharm EC was included and tableted into 100 mg. tablets:
Table 5. Resultant crushing strength, friability and disintegration times for the control formulation in example 3. Tablets were made at 5 kN and 8 kN compression force using a rotary tablet press.
Reducing the EC component from 10% to 5% again allowed significant improvements in tablet friability relative to the control in comparative example 1, while maintaining rapid disintegration times below 30 seconds.
A 500 gram batch of dry blended powder was prepared as above in example 2, however in place of dimenhydrinate, 25% directly compressible (pre-granulated) acetaminophen granulation was included. The tablet weight was increased from 100 mg used in comparative examples 1-2 and examples 1-3 to 120 mg.:
Table 6. Resultant crushing strength, friability and disintegration times for the control formulation in example 2. Tablets were made at 5 kN, 8 kN and 15 kN compression force using a rotary tablet press.
Acetaminophen is commonly known as a poorly compressible drug. The data show that the formulation system is able to accommodate a series of different physico-chemical drug characteristics while maintaining low friability and rapid disintegration.
A 500 gram batch of dry blended powder was prepared as above in example 4, however in addition to granular mannitol, 10% liquid sorbitol was added after initial dry blending of drug, ethylcellulose, mannitol, croscarmellose. The liquid sorbitol (70% sorbitol in 30% water) was added gradually while mixing to form a homogenous, “dry to the touch”, free flowing powder. The amount of ethylcellulose and croscarmelose were also increased. After lubricant addition the 120 mg tablets were then compressed as in example 4.
A 500 gram batch of dry blended powder was prepared as above in example 5, however in place of liquid sorbitol, 10% spray dried sorbitol was used. The tablets were compressed using ⅝″ round troche tooling with circular elevation in the center of the punch face, such that the center of the tablet was thinner than the perimeter of the tablet. Tablet target weight was 900 mg and tablets were compressed at 15, 20 and 25 kN.
Examples 5 and 6 show the versatility of the system with regard to different tablet sizes and geometries, as well as inclusion of a diverse range of and physical forms of sugar alcohols and ingredients.
It is not intended that the examples presented here should be construed to limit the invention, but rather they are submitted to illustrate some of the specific embodiments of the invention.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/928,125 filed on May 8, 2007, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60928125 | May 2007 | US |
