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Lipophilic Compositions
This invention relates to compositions and methods thereof for preparing pharmaceutical dosage forms comprising biologically active compounds with low water solubility complexed with water insoluble polymers to increase solubility in aqueous media.
BACKGROUND OF THE INVENTION
Lipophilic compounds should be in the molecular state to allow optimum transport across membranes. Size reduction techniques employing intensive mechanical, fluid or ultra sound energy are extensively used to obtain fine powders, which have large surface areas exposed to dissolution medium. However, this alone may not be sufficient to increase solubility and reach bioavailability targets of at least 30%. Other methods used to increase solubility include derivitisation and formation of soluble salts, amorphous forms, molecular complexes, eutectics, solid solutions, self emulsifying compositions, etc.
Given the wide range of water insoluble compounds it is unlikely that one particular technology will be universally suitable to improve solubility. Hence there is a requirement ' for novel, industrially applicable methods for increasing dissolution of new and existing compounds without resorting to chemical modification or derivatisation.
PRIOR ART
US-A-4,992,278 describes compositions comprising drugs embedded in high viscosity grades of water insoluble polymers to modify the release of drugs with low solubility in the GI tract.
WO 00/33817 describes hardened lipid compositions comprising either hydrophilic or lipophilic compounds with phospholipids and hydrocolloids in solid oral dosage forms.
/. Microencapsulation 1996 Jan-Feb; 13(1), pp 89-98 describes micro-matrices comprising the lipophilic drug ketoprof en and solid blends of high viscosity 14 cP ethylcellulose and cellulose acetate trimellitate. It does not disclose compositions comprising a lipophilic drug and low viscosity lipophilic polymers without pH sensitive cellulose ester. Furthermore, the compositions do not require organic solvents to co-solubilise ethyl cellulose and the hpophilic compound in preparing the micro-matrix. J. Control Release 66(2000) 107-113, describes tramadol complexed with a resin. A suspension of the drug resin complex is coated by spray drying using ethylcellulose with viscosities between 10 and 100 cP. It does not disclose a drug complexed with ethyl cellulose.
US-A-5,389,382 describes injectable liquid compositions comprising colloidal hydrosols of a lipophilic compound and ethyl cellulose suspended in water. A hydrosol is a sol that has water as its liquid phase and is outside the claims of the present invention which describe
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Extant methods and compositions employed for improving dissolution and aqueous solubility result in complexes consisting of lipophilic compounds and essentially hydrophilic polymers. The references teach away from the invention and do not suggest a method of preparing oral compositions comprising lipophilic compounds complexed with water insoluble polymers and hydrophilic agents to improve solubility as well as compositions comprising lipophilic compounds complexed with low viscosity grades of ethyl cellulose and/ or lipophilic resins for improving solubility.
SUMMARY OF THE INVENTION
The invention is in the area of 'lipophilic precipitates' and 'lipophilic polymer matrices' or 'Hpophilic polymer complexes' comprising compounds with low water solubility and essentially water insoluble polymers.
The invention relates to a method of preparing dry solid particles to increase the physical stability, dissolution rate and solubility of water insoluble compounds. Thus the invention describes methods and compositions thereof comprising lipophilic compounds homogeneously dispersed and associated in a dry /particulate polymeric matrix for use in oral or topical dosage forms.
Subject matter of the present invention is a method of preparing a pharmaceutical dosage form for oral or topical administration of a therapeutic agent with low water solubility, which method comprises, a) Homogeneously dispersing the therapeutic agent and at least one lipophilic polymer in at least one water-miscible organic solvent, diluting the resulting solution with water, collecting the resulting precipitate and drying, or b) Homogeneously dispersing the therapeutic agent in at least one water-immiscible or water miscible solvent and at least one lipophilic polymer, removing the solvent and collecting the dry precipitate obtained and, after performing either one of process steps a) or b) further processing the resulting powder into a pharmaceutical dosage form.
The residual water content of the particulate/ solid lipophilic complex from either method is preferably below 10 wt %.
DETAILED DESCRIPTION OF THE INVENTION
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The following definitions apply in this specification:
'Homogenously dispersed' or 'dissolved' refers to colloidal or molecular distribution of the component/ s in a medium, matrix or solvent.
'Pharmaceutical dosage form' for oral or topical administration include hard gelatine powder capsules, soft gelatine capsules and their likes, tablets, powders for (DPI) dry powder inhalers, paste like creams, ointments and gels.
"Compounds" are biologically active substances that have a physiological and/ or pharmacological effect. They are also referred to as drugs or agents and include nutriceuticals, feed components, cosmetic and diagnostic substances.
"A compound of low water solubility" includes any compound that requires more than 10 parts of water at pH 7 to dissolve 1 part of the compound or excipient. It spans the definitions between sparingly soluble (from 10 to 30) to very slightly soluble (from 1000 to lO'OOO) and practically insoluble or insoluble (10000 and over) as defined in USP 24.
"Low viscosity" defines the viscosity of a 5 % solution of a polymer (previously dried 30 min at 100 °C) in a solution of toluene/ ethanol 80/20 w/w wherein the viscosity is equal or lower then 11 cP .
"Molecular" and "amorphous" define the distribution states of poorly water soluble compounds in the polymer complex whereby at least 50 % of the compound transfers to a dissolution medium described in USP or an appropriate dissolution medium at 37 °C within 18 hours.
'Monomolecular' refers to a uniform distribution of molecules throughout a medium or matrix.
"Polymer" includes high molecular wt natural and synthetic compounds and excipients with repetitive units. The definition also includes resins and rosins.
"Water insoluble", ''Hpophilic" and "hydrophobic" polymers are used synonymously in this specification. The terms include polymers that are practically insoluble in water; partially soluble in volatile water miscible or hydrophilic solvents such as ethanol; freely soluble in volatile lipophilic solvents such as methylene chloride; non-volatile hydrophilic solvents particularly N-methyl pyrollidone (NMP); mixtures of hydrophilic solvents and water.
"Water-miscible" or 'hydrophilic" solvent refers to an organic liquid that can be diluted with at least an equal part of water without separation.
"Water-immiscible" or 'lipophilic" solvent refers to an organic liquid that can not be diluted with at least an equal part of water without separation.
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"Lipophilic polymer complex", "lipophilic matrix" and "precipitates" are particulate compositions comprising compounds with low water solubility in molecular association either as mono olecular species, or as amorphous particles complexed in a polymeric matrix. The particle size range of the complex is between 5 μm to 500 μm.The compound may be in monomolecular distribution in the lipophilic polymer or it may be associated as amorphous particles. The compound dissociates easily from the complex comprising low viscosity water insoluble polymer which may contain a minor amount of hydrophilic agent.
As used herein, the terms 'a', 'an' and 'any' are intended to include both the singular and plural terms.
Precipitates prepared using lipophilic compounds and preferably an excess of hpophilic polymers homogeneously dispersed/ dissolved in suitable solvents form molecular complexes when diluted with water or if the solvent is removed. Typically, depending on the physico-chemical properties of the compound and/ or ratio of drug substance to polymer, the compound in the precipitated lipophilic matrix is complexed either monomolecularly or forms particulate amorphous associates embedded in the polymer matrix. Generally the particle size range of the associates is between 5 μm to 500 μm. In some cases, a small but consistent fraction of the drug content, up to 10 % by weight may be crystalline, whilst about 90% are in molecular complex. Be it monomolecular association and/ or amorphous formation, the compound is likely to show a faster dissolution rate due to weak hydrophobic bonding between Hpophilic components. For instance, 98 wt % of, a highly insoluble HIV compound complexed with a low viscosity grade of a Hpophilic polymer such as ethyl ceHulose is released from a HpophiHc matrix within 6 hours.
Furthermore, the HpophiHc polymer matrix helps to stabilise amorphous particles against excess moisture and prevents or delays crystalHsation. Preferred HpophiHc polymers for this purpose are low viscosity grades of polymers which unexpectedly aUow the compound to disassociate more easily either from a molecular state or from amorphous particles, into aqueous media. This contrasts with compositions for improving solubiHty of HpophiHc compounds using hydrophiHc coHoids. The HpophiHc compound is more Hkely to separate out as insoluble crystals from a hydrophiHc matrix.
It should be clearly understood that the invention relates to a method of preparation and to dry solid or particulate compositions thereof comprising HpophiHc compounds that have improved solubiHty and dissolution properties for use in soHd oral dosage or semi-soHd topical forms. Depending on the hydrophobicity of the HpophiHc compound, the compositions may optionaUy comprise smaHer amounts of hydrophiHc agents or polymers relative to the low viscosity HpophiHc polymers including but not limited to surfactants, sugars and hydrophilic and osmotic components that dissolve easily in water. Since the
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In one aspect, the invention describes a method of preparing a composition comprising a HpophiHc polymer complex which comprises in Process variant A; i) homogeneously dispersing a therapeutic compound with low water solubiHty, a HpophiHc polymer and optionaUy a hydrophiHc agent in at least one water miscible organic solvent; u) diluting the resulting solution/ molecular dispersion with water;
Hi) coUecting the resulting co-precipitate and drying; iv) further processing the resulting powder into a pharmaceutical dosage form.
According to a preferred embodiment the therapeutic compound with low water solubiHty, the HpophiHc polymer and optionally the hydrophiHc agent are dissolved in at least one water miscible organic solvent, preferably N-methylpyrroHdone, ethanol, methanol, isopropanol or mixtures thereof. Typical of the method is that water miscible solvent with high (> 100 °C) as well as low (< 100 °C) boiling points at atmospheric pressure may be used.
The compound is firstly dissolved in the water miscible organic solvent together with at least one HpophiHc polymer such as ethylcellulose and/ or Dammar gum, optionaUy minor amounts of at least one water soluble agent, optionaUy using flash heating procedures for maximum solution. Secondly, the solution is diluted with water. The resulting precipitate may be washed with water to remove the solvent, dried and powdered if necessary. The particle size of the dry powder or particulate composition is below 1000 μm, preferably below 500 μm, more preferably between 5 μm to 100 μm. However, they may be milled to obtain particles which are smaUer than 5 μm for more rapid dissolution in oral dosage forms or for topical appHcations, particularly inhalation. The powder may also be agglomerated into granules suitable for capsule or sachet filling. Using suitable excipients and disintegrants the granules may be further processed into tablets. Preferably, hydrophiHc
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solvents such as NMP and/ or ethanol, isopropanol, and methanol with much less environmental toxicity than e.g. methylene chloride, are particularly suitable for preparing co-precipitates by addition of water and drying the polymer complex with or without heat and vacuum assistance and further particle size reduction.
Suitable water miscible organic solvents that may be removed by washing the precipitate are N-methyl-pyrroHdone (NMP), ethyl lactate and glycofurol and combinations thereof with water miscible solvents such as ethanol, methanol, acetone, etc..
The alternative Process variant B according to the invention comprises, i) homogeneously dispersing compound with low water solubiHty, HpophiHc polymer and optionaUy hydrophiHc agent in at least one water miscible or immiscible solvent, u) removing the solvent, iii) coUecting the resulting dry precipitate, iv) further processing the resulting powder into a pharmaceutical dosage form.
Accordingly, it may be more expedient to prepare HpophiHc powder complexes directly by dispersing the components in water miscible or water immiscible organic solvent/ s foUowed by removal of solvent/s by e.g. spray drying, spray granulation, or a similar process thereby yielding a soHd HpophiHc complex with similar properties to those obtained as if a water miscible solven had been employed in Process A. Suitable water miscible solvents that are also suitable for solvent removal processes such as spray drying, spray granulation, or vacuum drying are e.g. acetone, methanol, ethanol, isopropanol, n -propanol, NMP and mixtures thereof. Suitable water immiscible organic solvents that may be more amenable to solvent removal processes such as spray drying given strict solvent recovery instaUations are dichloromethane and dimethoxymethane, diethoxymethane and dioxacyclopentane.
The present invention also relates to a pharmaceutical composition comprising a therapeutic agent of low water solubiHty, at least one Hpophilic polymer, and, optionaUy conventional pharmaceutical additives, which are water-soluble or have wetting properties, as obtained by the methods a) or b) as described above.
According to a preferred embodiment the present invention relates to a pharmaceutical composition comprising a therapeutic agent of low water solubiHty, at least one HpophiHc polymer selected from the group consisiting of low viscosity ethyl ceHulose or a HpophiHc resin of natural origin or a mixture of both, and, optionaUy conventional pharmaceutical additives.
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Lipophilic compounds which may benefit from the invention are sparingly soluble therapeutic agents suitable for oral and topical administration. They are, e.g. immunosuppressants having a macroHde structure, typicaUy cyclosporin A, cyclosporin G, rapamycin, tacroHmus, deoxyspergualin, mycophenolate-mofetil, gusperi us; non-steroidal antiphlogistic agents and salts thereof, typicaUy acetylsaHcyHc acid, ibuprofen or S(+)- ibuprofen, indomethacin, diclofenac (Na and K-salt), piroxicam, meloxicam, tenoxicam, naproxen, ketoprof en, flurbiprofen, f enoprofen, f elbinac, sulindac, etodolac, oxyphenbutazone, phenylbutazone, , nabumetone COX-2 inhibitors like celcoxib and steroidal antiflogistics like prednisone, cortisone; dihydropyridine derivatives having cardiovascular activity, e.g. nifedipine, nitrendipine, nimodipine, nisoldipine, isradipine, felodipine, amlodipine, nUvadip ne, lacidipine, benidipine, masnipine, furnidipine, niguldipine; angiotensin II receptor antagonists like candesartan, HpophiHc anticoagulants; thrombolytics; irnmunodepressants and stimulants, typicaUy a-Hponic acid; CNS acting agents, e.g. reserpine, ergot alkaloids, typicaUy bromocriptine, dihydroergotamine, dihydroergocristine; carbamazepine, irrύprarnine, benzodiazepines, nicotine, caffeine; antitumour agents, e.g. vincopectin, vincristine, vinblastin, chlorambucU, etoposide, teniposide, idoxifen, tallimustin, teloxantron, tirapazamine, carzelesin, dexniguldipine, intopHcin, idarubicin, mUtef osin, trofosfamide, teloxantrone, melphalan, lomustine, 4,5- bis(4Ηuoroanilino)phthalimide; 4,5-dianilinophthaHmide; immunomodulators Hke tacroHmus, typicaUy thymoctonan, prezatid copper acetate; H2-receptor antagonists, typicaUy famotidine, cimetidine, ranitidine, roxatidine, nizatidine, omeprazole, proteinkinase inhibitors; or H1N-1 or HIV-2 protease inhibitors or leucotriene antagonists, HpophiHc narcotics/ aneasthetics Hke propofol and hormones Hke estrogen, testosterone and their esters.
Instead of the free acid or base, the therapeutic agents may be converted to a salt, typicaUy as hydrobromide, hydrochloride, mesylate, acetate, succinate, lactate, tartrate, fumarate, suUate, maleate, and the Hke, especiaUy if the counter ions form ion-pair which is solvent soluble.
To increase the stabiHty of the active compound against oxidation, it is advantageous to add HpophiHc stabUizers such as alpha-tocopherol, t-butylated hydroxytoluene, t-butylated hydroxyanisole or ethoxyquin. Preferably they are dissolved together with the compound and other HpophiHc excipient in the organic phase.
Typical examples of HpophiHc polymers or excipients used in this invention are water insoluble polymers such as ethylceUulose (Dow Chemical, USA; Hercules, FRG) and Dammar gum (CΝI ; France). Preferred are ethylceUulose grades with not less than 44 % and not more than 51 % by weight of ethoxy groups. More preferred are ceUulose grades meeting the requirements of the National Formulary of 48.0 - 49.5 % ethoxy group content (N-grade)
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(Hercules, Product data brochure on AQUALON® EthylceUulose). In some cases, however, ceUulose grades with less than 44 % or more than 51 % by weight may be used as weU. Depending on the molecular weights, the grade of ceUulose may have viscosities up to 11 cps. Most preferable are ethylceUulose grades with low viscosity, such as N7 or N4 or lower such as N3, obtainable from Dow Chemical or Hercules Inc. The values are obtained from a 5 % w/ w solution comprising 80 parts toluene and 20 parts ethanol.
Dammar gum is a resin characterised by low viscosity and is a preferred alternative to low viscosity ethylceUulose. Dammar gum can also be used in combination with low viscosity ethylceUulose. The foUowing resins can be used either as the Hpophilic excipient on its own or in combination with low viscosity N grade ethylceUulose: A) Natural resins: Batu run resin, Congo run resin, Elemi resin, Kauri resin, Manila gum, Mastic gum, Rosin wood resin, Sandarc resin, sheUac resin, white sheUac, Vinsol® resin; B) Rosin and terpene base resins: Abalyn, Abitol E, Cellolyn 21 102M, Ester gum, Hercolyn D, Lewisol 28, Pentalyn A, H, 830. 856, Pentrex 28, Poly paleresin, StabeHte 3, 10 ester Vinsol ester gum, Zinar, Zirex and Zitro, Uni-Rez 7200;
The ratio of HpophiHc compound to the HpophiHc polymer is between 1:200 to 10 :1. Preferably it is 1:1 to 1:50. more preferably it is 1:1 to 1:10.
Suitable organic solvents may be water im-miscible or preferably water miscible solvents; Examples of water immiscible organic solvents are, methylene chloride, dimethoxymethane etc and mixtures thereof. Examples of preferred water miscible solvents are, e.g. NMP , isopropanol, ethanol, 96% ethanol, methanol ethyl lactate, polyethylene glycol 300, polyethylene glycol 400, 1,2 propanediol, 1,3 butanediol, succinic acid diethyl ester, triethyl citrate, dibutyl sebacate, dimethyl acetamide, DMSO, glycerineformal, glycofurol (tetraglycol), isopropanol, lactic acid butyl ester, propylene carbonate, propylene glycol diacetate, tetrahydrofurfuryl alcohol, diethylene glycol mono ethyl ether and mixtures thereof.
The invention aUows the co-precipitates preferably to include smaUer amounts of hydrophilic excipients and ingredients. These confer or have wetting properties and/ or are highly water soluble. Examples are PEG (polyethylengylcol) with MW 4000-6000, polyvinylpyrroHdone, polyvinylalcohol, crosspovidone, polyvinylpyrroHdone- polyvinylacetate copolyrήer, ceUulose derivatives, Hke hydroxypropylmethylceUulose (HMPC), hydroxypropylceUulose (HPC), hydroxypropylmethylceUulose phthalate (HPMCP), polyacrylates and polymethacrylates, natural hydrocoUoids, gelatine, urea, sugars, polylols, chitosan, organic acids (succinic acid, citric acid) and non ionic, anionic, cationic or amphoteric surfactants such as phosphoHpids.
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The weight ratio of low viscosity grades of lipophilic polymer to hydrophiHc polymer or agent/s in the composition may be between 2:1 to 10 : 0.1. Preferably from 5:1 to 10:1.
The compositions according to the invention are eminently suitable as pharmaceutical dosage forms and in food (including nutriceuticals) and feed formulations. The powder complex may be used as such or incorporated directly into food and feed appHcations.
For oral dosage forms, the dry powder complex or granules may be blended with suitable bulking agents and flow aids to the required fiU weight for hard gelatine capsules or the Hke. OptionaUy, the powder complex may be formulated with disintegrants and compression aids for compaction into tablets.
For pulmonary or nasal deHvery, the dry powder complex may be micronised to below 10 μm, preferably between 2 μm to 7 μm weight mean particle diameter for delivery of HpophiHc compounds in (DPI) dry powder inhalers.
The micronised powder complex may be suspended in creams and ointments and other non aqueous systems for dermatological appHcations. Suitable non aqueous vehicles are eg. polyols, PEGS or fatty acid glycerides, esters and ethers, etc.
There is described dry compositions comprising HpophiHc compounds associated with low . viscosity grades of water insoluble polymer and optionaUy hydrophiHc agent/s associated either as monomolecular or amorphous complexes. There is also described a method of preparing said HpophiHc polymer complexes from a solution or homogeneous dispersion employing either water miscible or immiscible organic solvents. The HpophiHc polymer complex is precipitated from the solution comprising a water miscible solvent by dUution with water, separating out the precipitated complex, washing, drying and conversion to oral and topical dosage forms. The HpophiHc polymer complex may also be prepared by solvent removal involving spray drying or vacuum drying under elevated temperatures using either water miscible or water immiscible solvents. The compositions are characterised by improved dissolution and solubiHty of the associated compound in aqueous medium.
The foUowing examples illustrate the invention.
Example 1
167 mg of an anti HIN compound (solubiHty in water < 0.010 μg/ml), 167 mg of HPMC and 1667 mg EthylceUulose Ν4 (Dow Chemical) are dissolved in 10 ml ethanol/NMP (50/50 v/v). The clear solution is added under stirring to a ten fold excess of water to prepare particulate precipitates that are below 500 μm. The resulting precipitate is coUected on a filter and washed twice with 20 g water to remove the solvents. The wet mass is dried for 8 h at 30
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°C in a vacuum oven. The resulting free flowing fine powder is used to fill hard gelatine capsules, suitable for oral administration.
Example 2
Sirr lar to Example 1, in place of 167 mg HPMC, 167 mg alpha tocopherol is used.
Example 3
Sirrdlar to Example 2, in place of Ethylcellulose N4, EthylceUuUose N3 (Hercules) is used.
Example 4
Similar to Example 3, in place of EthylceUulose N4, EthylceUuUose N7 (Dow) is used.
Example 5
167 mg of an anti HIV compound used in Example 1, 167 mg of HPMC and 1667 mg Dammar gum (NCI) are dissolved in 10 ml methylene chloride. The clear solution is added to a fluidised bed dryer or spray granulator or spray dryer and the solvent is removed at 30 ° C during 4 hours. The resulting free flowing fine powder is used to fiU hard gelatine capsules, suitable for oral administration.
Example 6
100 mg of nifedipine, 1000 mg EthylceUulose N3 (Hercules) are dissolved in 10 ml NMP . The clear solution is added under stirring to a ten fold excess of water. The resulting precipitate is coUected on a fUter and washed twice with 20 g water to remove the solvent. The wet mass is dried for 8 h at 30 °C in a vacuum oven. The resulting free flowing fine powder is used to fill hard gelatine capsules, suitable for oral administration.
Example 7
Analogue to Example 6, instead of nifedipine 100 mg candesartan is used.
Example 8
Analogously to Example 6, instead of Nifedipine 100 mg celcoxib is used.