| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | August 26, 2003 |
| PATENT TITLE |
Process for making chemically stable C-17/21 OH 20-ketosteroid aerosol products |
| PATENT ABSTRACT | A medicinal aerosol steroid solution formulation product with enhanced chemical stability. The steroid is a 20-ketosteroid having an OH group at the C-17 or C-21 position and the aerosol container has a non-metal interior surface which has been found to reduce chemical degradation of such steroids |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | October 4, 2001 |
| PATENT REFERENCES CITED |
New SilcoCan Canister with Pressure/Vacuum Guage", Restek Advantage Chromatography Newsletter, online at URL:http://www.restekcorp.com/advantage/e96seven.htm, 1996. Lee, et al, "New Steroidal Anti-Inflammatory Drugs", New Developments in Antirheumatic Therapy, Inflammation and Drug Therapy Series, Chapter 6, vol. III, pp. 153-169, (Kluwer Academic Publishers, 1989). George, R.F., Wilson and Grisvold's Textbook of Organic Medicinal and Pharmaceutical Chemistry, 8.sup.th Edition, p 703, table 18-13 (J.B. Lippincott Co., Philadelphia, 1982). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A method of reducing the chemical degradation of a medicinal 20-ketosteroid dissolved in an aerosol formulation including a hydrofluorocarbon propellant selected from the group consisting of 1,1,1,2-tetrafluoroethane, 1,1,1,2, 3,3,3-heptafluoropropane, and mixtures thereof, contained in a metal container equipped with a metered dose dispensing valve, said dissolved 20-ketosteroid being other than flunisolide and having an OH group at the C-17 position or C-21 position or both, comprising the step of providing a non-metal oxide material on the interior surface of the metal container so as to reduce reaction of the 20-ketosteroid with metal oxides from the container. 2. A process for making a chemically stable steroid solution aerosol product by filling into a container equipped with a metered dose dispensing valve, an aerosol formulation including a hydrofluorocarbon propellant selected from the group consisting of 1,1,1,2-tetrafluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, and mixtures thereof, and comprising a dissolved 20-ketosteroid other than flunisolide, said 20-ketosteroid having an OH group at the C-17 position or C-21 position or both, and said container having an inert non-metal oxide interior surface so as to avoid chemical degradation of the 20-ketosteroid due to interaction with metal oxides from the container. 3. The process of claim 2, wherein the container is made of aluminum having an inert interior coating. 4. The process of claim 3, wherein the interior coating is an epoxy-phenolic lacquer. 5. The process of claim 3, wherein the interior coating is a perfluoroethylenepropylene. 6. The process of claim 2, wherein the container is made of stainless steel with an interior coating of inert material. 7. The process of claim 2, wherein the medicinal aerosol formulation includes ethanol. 8. The process of claim 2, wherein the 20-ketosteroid has an OH group at the C-17 position, but not at the C-21 position. 9. The process of claim 2, wherein the 20-ketosteroid has an OH group at the C-21 position, but not at the C-17 position. 10. The process of claim 2, wherein the 20-ketosteroid has an OH group at both the C-17 and C-21 positions. 11. The process of claim 2, wherein the 20-ketosteroid is a corticosteroid selected from the group consisting of budesonide, triamcinolone acetonide, desonide, fluocinolone acetonide, alclometasone, beclomethasone, beclomethasone 17-monopropionate, betamethasone, betamethasone 17-valerate, clocortolone, desoximetasone, dexamethasone, dexamethasone sodium phosphate, dexamethasone 21-isonicotinate, diflorasone, flumethasone, methylprednisolone, paramethasone, prednisolone, triamcinolone, clobetasol, and fluorometholone. 12. The process of claim 2, wherein the 20-ketosteroid is budesonide. 13. The process of claim 2, wherein the 20-ketosteroid is triamcinolone acetonide. 14. The process of claim 2, wherein the 20-ketosteroid is dexamethasone. 15. The process of claim 2, wherein the 20-ketosteroid is betamethasone 17-valerate. 16. The process of claim 2 wherein the valve has a coating applied to it. 17. The process of claim 16, wherein metal valve components have a coating applied by vapor deposition. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD The present invention relates to medicinal aerosol products and, in particular, to aerosol products such as metered dose inhalers for delivery of steroids. The invention is particularly related to certain 20-ketosteroids that have been found to be highly susceptible to chemical degradation when formulated as solution aerosol products, and provides a way of enhancing chemical stability of such steroids. BACKGROUND Structure I shown below is a typical core structure for a large number of natural and synthetic 20-ketosteroids, with the standard IUPAC numbering system of the carbon positions 1 to 21 indicated. ##STR1## These types of steroids, with varying substituents and bonding, have many well-known therapeutic uses, especially based upon their anti-inflammatory activity. It is often desirable to deliver such steroids topically using aerosol spray devices, such as metered dose inhalers (MDIs). MDIs are commonly used to deliver steroids, e.g., beclomethasone dipropionate, to the airways of patients via oral or nasal inhalation for the treatment of asthma and allergic rhinitis. One common difficulty, however, in making products for delivering steroids has been that they are often chemically unstable in aerosol formulations and degrade during storage. A great deal of research has been directed at steroid degradation. Chemical degradation is especially problematic when the steroid is dissolved in the formulation and, consequently, the vast majority of marketed MDI steroid products are formulated as particulate suspensions of the steroid, which are much less susceptible to chemical degradation than solutions. For example, it is believed that all currently marketed CFC-containing MDI products for delivering steroids are available only as particulate suspension formulations in CFC propellants. More recently, some selected steroids have been reformulated as solutions in non-CFC hydrofluorocarbon (HFC) propellants with ethanol. In the case of beclomethasone dipropionate, for example, solution formulations are disclosed in U.S. Pat. No. 5,766,573 which are surprisingly chemically stable in propellant HFC 134a and/or 227 and ethanol in a conventional aluminum canister. Likewise, ciclesonide formulations are surprisingly chemically stable in certain solution MDI formulations disclosed in WO98/52542. Solution formulations of flunisolide are disclosed in U.S. Pat. No. 5,776,433, where it is indicated that chemical stability may be enhanced by using additives like water, sorbitan trioleate, and cetylpyridinium chloride, and also that certain containers such as glass and resin coated aluminum enhance chemical stability and/or minimize the absorption of flunisolide onto the container wall. Also, WO96/40042 discloses that aqueous formulations of triamcinolone acetonide in neutral or basic solutions undergo oxidative degradation catalyzed by trace levels of metal ions, especially copper, and proposes the use of EDTA as sequestering agent and/or adjusting pH. Despite these limited examples, though, most commercial MDI formulations of steroids and other drugs have continued to be particulate suspensions. WO98/13031, for example, discloses recent work on reformulating budesonide as a non-CFC suspension formulation. However, suspension formulations of a medicament are more likely to encounter problems with physical instability (e.g., agglomeration, crystal growth and deposition on the container wall, all resulting in inconsistent dosage delivery). A drug delivery device providing medicinal steroid solution formulations with enhanced chemical stability would offer some significant advantages over suspension formulations. Besides homogeneity, solution formulations have been found in some cases--e.g., using HFC propellants and low ethanol content--to give dramatically higher respirable fractions (i.e., the percentage of active ingredient able to reach the airways of the lung) compared to a particulate suspension of the steroid drug. See U.S. Pat. No. 5,776,432. Furthermore, an aerosol product providing a chemically and physically stable aerosol steroid formulation using non-CFC propellant would offer the advantage of being more ozone friendly than currently available aerosol products with CFCs. Nevertheless, despite a substantial need, the problem of chemical degradation in steroid solution aerosol products has been poorly understood. Until now there has been no way to identify which steroids are likely to be most stable as solution aerosols and which will be most sensitive to degradation in solution aerosol products or how to reduce such degradation. SUMMARY It has now been found that those steroids in particular having a C-20 ketone and an OH group at the C-17 position or, especially, the C-21 position or both (hereafter collectively referred to as "C-17/21 OH 20-ketosteroids") are subject to enhanced chemical degradation when stored in contact with a metal container (particularly the metal oxide e.g., Al.sub.2 O.sub.3 layer that forms on the interior surface of the container). Moreover, the vast majority of MDI's on the market, including all MDI steroid products, use aerosol containers made of metal, usually aluminum. By utilizing an aerosol container having a non-metal interior surface it is possible to produce solution aerosol formulations of C-17/21 OH 20-ketosteroids having enhanced chemical stability. Generic structures for typical C-17 OH, C-21 OH, and C-17 and 21 OH 20-ketosteroids are shown below in structures II-IV, respectively. ##STR2## The present invention is especially preferred with respect to C-21 OH 20-ketosteroids (with or without a C-17 OH group). The C-21 OH group can substantially increase biological activity of a steroid, but such steroids are also much more susceptible to chemical degradation in the presence of metal. Particularly preferred 20-ketosteroids are budesonide, triamcinolone acetonide, dexamethasone, and betamethasone 17-valerate, all of which have an OH group at the C-21 position. These steroids are all currently on the market as CFC particulate suspension formulations in metered dose inhalers and, at least in the case of budesonide, work has been conducted to reformulate this important steroid as a non-CFC suspension product in HFA propellants. See PCT published application WO98/13031. The most preferred type of container for use in the present invention is a conventional aluminum (or aluminum alloy) aerosol canister, but with an interior coating of an inert material, such as a spray-coated, baked epoxy-phenolic lacquer (available from Cebal Printal U.K. Ltd.). Other metals, such as stainless steel, may likewise be used with an inert interior coating. It is also preferred that the internal surfaces of metal valve components in contact with the formulation are similarly coated with an inert material. Another preferred coating for the inside of the container is perfluoroethylenepropylene (FEP). A preferred coating for the metal valve components is a very thin layer of glass, or other material, deposited by gas vapor deposition. Such coating is preferably used on all of the metal valve components in contact with the formulation, including the inside and outside of the metering chamber, inside and outside of the bottle emptier (if any), and the inside and outside of the valve stem (if metal), and may also be used to coat the inside of the canister. The preferred such coating technique is the Silcosteel.TM. process available from Restek Corporation, Bellefonte, Pa. The Silcosteel.TM. aspect of the invention is useful even outside the context of the chemical degradation problem, for both solution and suspension formulations. Preferred formulations use a liquified propellant such as hydrogen-containing (non-CFC) propellants, more preferably hydrofluorocarbons, such as 134a and/or 227. Particularly preferred formulations include about 0.1 to 0.5% C-17/21 OH 20-ketosteroid about 75 to 99% 134a and/or 227, and about 1 to 25% w/w ethanol, more preferably about 80 to 95% 134a and/or 227, and about 5 to 20% ethanol. The most preferred medicinal aerosol products according to the invention are MDI's comprising about 0.1 to 0.5% budesonide or triamcinolone acetonide dissolved in about 80-95% 134a and/or 227 and about 5-20% ethanol, contained in a coated aluminum aerosol canister equipped with a metering valve. It should also be noted that chemical stability is especially critical for MDIs since these medicinal aerosol products must remain stable and deliver accurate dosing throughout their shelf life (typically 2 to 3 years) and in use. Only a very small amount of chemical degradation can be tolerated. Moreover, by providing chemically stable solutions of C-17/21 OH 20-ketosteroids, such as budesonide, triamcinolone acetonide, dexamethasone, and betamethasone 17-valerate, MDIs can be made that produce extra-fine aerosols resulting in higher respirable fractions than suspension formulation products. It can thus be seen that the present invention provides a medicinal aerosol steroid solution formulation product with enhanced chemical stability. Such product includes a container equipped with a dispensing valve and containing a medicinal aerosol formulation having a 20-ketosteroid drug dissolved therein. The 20-ketosteroid is other than flunisolide and has an OH group at the C-17 or C-21 position or both, and the container is provided with a non-metal interior surface so as to reduce chemical degradation. Also provided is a method of reducing the chemical degradation of a medicinal 20-ketosteroid dissolved in a formulation contained in a metal container, said 20-ketosteroid being other than flunisolide and having an OH group at the C-17 position or C-21 position or both, comprising the step of providing a coating of inert material on the interior surface of the metal container so as to reduce reaction of the 20-ketosteroid with metal oxides from the container. The invention further provides a process for making a chemically stable 20-ketosteroid solution aerosol product, by filling into a container an aerosol formulation comprising a dissolved 20-ketosteroid other than flunisolide, said 20-ketosteroid having an OH group at the C-17 position or C-21 position or both, and said container having an inert non-metal interior surface so as to avoid chemical degradation of the 20-ketosteroid due to interaction with the container. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described with reference to the following drawings, wherein: FIG. 1 is a cross-sectional view of a metered dose inhaler containing a medicinal 20-ketosteroid formulation with enhanced chemical stability according to the present invention; FIG. 2 is the same as FIG. 1, but with a modified valve configuration; and FIGS. 3-5 (Graphs A-C) show comparative impurity levels. DETAILED DESCRIPTION Turning to FIG. 1, there is shown a medicinal aerosol device 10 comprising a pressurizable metal aerosol container 16 equipped with a metering valve 18. The metal container 16 is preferably made of aluminum (i.e. aluminum or aluminum alloy) and has an inert interior coating layer 14. The metering valve 18 includes a metal metering chamber 20 with a coating layer 22. Moreover, although not shown, it is preferred that as many other metal surfaces in contact with the formulation 12 as feasible are also coated with an inert layer (e.g., the interior of the metering chamber). It is also preferred to use a valve design that minimizes metal surfaces in contact with the formulation 12. For example, it is preferred in the context of the present invention to use a plastic valve stem 24 instead of metal. FIG. 2 shows an alternative preferred embodiment that is essentially the same as FIG. 1, but utilizes a fixed bottle emptier 26, with coating layer 28. Also, a solution gasket 30 is used to further prevent contact of the formulation with metal components. The medicinal aerosol formulation 12 preferably includes a non-CFC propellant, a cosolvent (if necessary), and a therapeutically effective amount of dissolved C-17/21 OH 20-ketosteroid. A therapeutically effective amount will nornally be a concentration so as to provide in the range of about 100 to 1500 mg per day using one to eight puffs. Preferred propellants include hydrogen containing propellants, such as HFCs 134a and/or 227. Ethanol is a preferred cosolvent, although other cosolvents and solubilization aids (e.g., surfactants) may be used. The amount of cosolvent used is preferably an amount sufficient to completely dissolve the 20-ketosteroid. The formulation 12 may also include other excipients, such as stabilizers, antioxidants, flavoring agents, and the like. Although there are many possible C-17/21 OH 20-ketosteroids, there are two preferred types set forth below as structures V and VI: ##STR3## Wherein X is H, Cl, or F; Y is H, F, or Me; R.sup.1 is H or an alkyl group; R.sup.2 is an alkyl group; and provided that when Y is F, then X is not H. Preferred R.sup.1 and/or R.sup.2 alkyl groups are methyl, ethyl, propyl, butyl, pentyl, and hexyl groups, including their branched and cyclic isomers. R.sup.1 may form a ring with R.sup.2, preferably a cyclopentyl or cyclohexyl ring. Examples of known 20-ketosteroids according to structure V include budesonide, triamcinolone acetonide, desonide, and fluocinolone acetonide. ##STR4## Wherein Q is OH, H, Cl, or PO(ONa).sub.2 ; X is H, Cl, or F; Y is H, F, or Me;. Z is H or Cl; R.sup.1 is H, OH or propionate provided that when Q is not OH, then R.sup.1 must be OH; and R.sup.2 is H, OH, or Me. Examples of known 20-ketosteroids according to structure VI include alclometasone, beclomethasone, beclomethasone 17-monopropionate, betamethasone, betamethasone 17-valerate, clocortolone, desoximetasone, dexamethasone, dexamethasone sodium phosphate, dexamethasone 21-isonicotinate, diflorasone, flumethasone, methylprednisolone, paramethasone, prednisolone, tramcinolone, clobetasol, and fluorometholone. Within the group of C-17/21 OH 20-ketosteroids, those having an OH group at C-21, with or without an OH group at C-17, suffer from more severe degradation in the presence of metal oxide than 20-ketosteroids having an OH group at C-17, but not at C-21. For example, beclomethasone 17-monopropionate (17-BMP, 21-OH) degrades in ethanol/Al.sub.2 O.sub.3 about 100 times faster than its isomer 21-BMP (17-OH). This is important since it has been reported that the Structure-Activity Relationship for a C-21 OH group has an enhancement factor toward anti-inflammatory activity of 25 compared to an enhancement factor of only 4 for a C-17 OH group. See Doerge, R. F., Wilson and Grisvold's Textbook of Organic Medicinal and Pharmaceutical Chemistry, 8.sup.th Edition, p. 703, table 18-13 (J. B. Lippincott Co., Philidelphia, 1982). For particular structural examples, four preferred C-17/21 OH 20-ketosteroids according to the present invention, budesonide, triamcinolone acetonide, betamethasone 17-valerate, and dexamethasone, have the following structures: ##STR5## The C-17/21 OH 20-ketosteroid is dissolved in the aerosol formulation and preferably contained in an inertly coated metal container. As used herein, the terms "coated", "inert coating" and the like simply refer to a non-metal interior coating that does not promote degradation at the OH substituents on C-17/21 OH 20-ketosteroids. Inert coating materials include any suitable polymer, lacquer, resin, or other coating treatment that creates a barrier to chemical interaction of the dissolved C-17/21 OH 20-ketosteroid and metal on the container (especially metal oxides). Examples of suitable interior coatings include epoxy-phenolic resins, epoxy-urea-formaldehyde resins, polytetrafluroethylene (PTFE), perfluoroethylenepropylene (FEP), perfluoroalkoxyalkane (PFA), ethylene tetrafluoroethylene (ETFE), poly(vinyldiene fluoride) (PVDF), and chlorinated ethylene tetrafluoroethylene. Blends may be used of fluorinated polymers with non-fluorinated polymers such as polyamides, polyimides, polyethersulfones, polyphenylene sulfides, and amine-formaldehyde thermosetting resins. Specific blends include PTFE/FEP/polyamideimide, PTFE/polyether sulphone (PES) and FEP-benzoguanamine. Preferred interior coating materials are epoxy-phenolic resins, epoxy-urea-formaldehyde resins, PTFE, and FEP. Additional information regarding interior can coatings is taught in, e.g., EP 642992, WO96/32099, WO 96/32150, WO96/32151, and WO96/32345, which disclose interior can coatings for drug suspension formulation products. A preferred coating for the metal valve components is a very thin layer of fused silica glass, or other material, deposited by gas vapor deposition. Such coating is preferably used on all of the metal valve components in contact with the formulation, including the inside and outside of the metering chamber, inside and outside of the bottle emptier (if any), and the inside and outside of the valve stem (if metal). The preferred such coating technique is the Silcosteel.TM. process available from Restek Corporation, Bellefonte, Pa. This process deposits a submicron layer of fused silica glass on the metal components and can be used both on the valve components and on the interior of the canister. Not only is it helpful in preventing chemical reaction with the metal, but passivation of the metal surface using the Silcosteel process can provide a smooth surface on, for example, the valve stem so as to reduce friction and help prevent valve clogging, and can also reduce oxidation of the metal that can introduce particulate material into the system. The Silcosteel.TM. aspect of the invention is thus useful even outside the context of the chemical degradation problem, for both solution and suspension formulations. The Silcosteel process is performed at a temperature of 400.degree. C., which has the added benefit of thermally removing residual oils on the metal surface. It is also possible to use containers made from non-metal materials, such as glass or plastic (e.g., polyethylene terephthalate, from Precise Plastic Ltd., U.K.). In the case of glass containers, however, it is preferred to use glass having a low metal oxide content. According to the American Society for Testing and Materials (ASTM), Type I/Class A glass contains 2% aluminum oxide, whereas Type II/Class B glass contains 7% aluminum oxide. The former is therefore preferred. Type III (soda-lime) glass vials may also be used (available from Wheaton Coated Products). High metal oxide content glass should also be avoided during development and testing of formulations containing C-17 and/or C-21 OH 20-ketosteroids because such use could cause unsuspected chemical degradation due to the glass metal oxide content. Coated containers can be made by pre-coating the metal roll stock before forming the container or by coating the container after it is made, by various techniques known in the art of coating. For example, suitable coating procedures include plasma coating, electrostatic dry powder coating, impregnating/spraying, hard anodization with polymer deposition, chemical vapor deposition (CVD), physical vapor deposition (PVD), as well as other procedures known in the art for this purpose. Preferably, the containers are coated with an epoxy resin and then baked. Suitable coated containers can be obtained from, for example, Cebal Printal U.K. Ltd. Preferred products/devices according to the present invention are pressurized aerosols such as MDIs that use liquefied gas propellants, including chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), fluorocarbons (FCs), hydrocarbons (HCs), hydrochlorofluorocarbons (HCFCs), and dimethyl ether (DME). Propellants containing hydrogen are preferred. Ethanol may also be included to assist in solubilizing the 20-ketosteroid, preferably in an amount of about 1-25%. Formulations comprising dissolved C-17/21 OH 20-ketosteroid, HFC propellant, such as 134a and/or 227, with 5-20% ethanol are particularly preferred. Also, it is generally preferred that the formulations are essentially non-aqueous, meaning that they do not include added water, although very small amounts of water may be present due to water ingress and/or as a residual in formulation components (such as ethanol). Formulations will preferably have less than about 3%, and more preferably less than about 0.5% water content. The containers can be equipped with any suitable conventional or unconventional dispensing valve, preferably a metered dose valve. |
| PATENT EXAMPLES | available on request |
| PATENT PHOTOCOPY | available on request |
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