Pharmaceutical suspension aerosol formulations containing a therapeutically effective amount of a drug and HFC 134a, HFC 227, or a mixture thereof.

DETAILED DESCRIPTION OF THE INVENTION

The term "suspension aerosol formulation" as used herein refers to a formulation in which the drug is in particulate form and is substantially insoluble in the propellant.

Amounts expressed herein in terms of percent refer to percent by weight based on the total weight of the formulation.

The formulations of the invention that consist essentially of drug and a propellant contain drug and propellant in relative amounts such that a formulation suitable for aerosol administration is obtained without the need for additional components. Such formulations preferably contain less than an effective stabilizing amount of surfactant and more preferably are substantially free of surfactant and other components.

The formulations of the invention contain a drug in a therapeutically effective amount, that is, an amount such that the drug can be administered as an aerosol (e.g., topically or by oral or nasal inhalation) and cause its desired therapeutic effect with one dose, or less preferably several doses, from a conventional valve, e.g., a metered dose valve. "Amount" as used herein refers to quantity or to concentration as appropriate to the context. The amount of a drug that constitutes a therapeutically effective amount varies according to factors such as the potency, efficacy, and the like, of the particular drug, on the route of administration of the formulation, and on the device used to administer the formulation. A therapeutically effective amount of a particular drug can be selected by those of ordinary skill in the art with due consideration of such factors. Particularly in formulations of the invention intended for oral inhalation into the lungs, the drug is preferably micronized, i.e., about 90 percent or more of the particles have a diameter of less than about 10 microns, in order to assure that the particles can be inhaled into the lungs.

The particular amount of drug that will remain suspended in a formulation of the invention for a time sufficient to allow reproducible dosing of the drug depends to some extent on the nature of the particular drug, e.g., its density, and on the particular propellant used in the formulation. Generally, however, it has been found that when drug concentrations of less than about 0.1 percent are used in a formulation of the invention the drug flocculates to some degree but generally does not settle or cream to the extent that the suspension becomes unsuitable for use as an aerosol formulation, e.g., in a metered dose inhaler. Therefore as regards drug concentration such formulations are acceptably homogeneous.

When drug concentrations greater than about 0.1 percent but less than about 0.5 percent are used in a formulation of the invention it is sometimes seen that the drug flocculates considerably in the formulation and therefore might have an increased tendency to cream or settle. As discussed below in connection with the propellant component of the formulations of the invention, in these instances it is preferable to select the propellant in a manner that minimizes creaming and settling of the drug in order to assure that the formulation is acceptably homogeneous as regards drug concentration.

As drug concentration increases, e.g., beyond about 0.5 percent, the tendency of the drug to flocculate generally increases also. However, the volume occupied by the flocculated drug also increases and the flocculated drug begins to occupy substantially all of the volume of the formulation. In such instances the flocculated drug often shows a lesser tendency to cream or settle. As regards drug concentration such formulations are acceptably homogeneous.

Generally the concentration of the drug in a formulation of the invention is preferably less than about 0.1 percent, more preferably less than about 0.08 percent, and most preferably less than about 0.05 percent. Accordingly, it is preferred according to this invention that the drug have a potency such that concentrations less than about 0.1 percent, more preferably less than about 0.08 percent, and most preferably less than about 0.05 percent, are therapeutically effective. Preferred drugs for use in the formulations of the invention therefore include formoterol, salmeterol, and pharmaceutically acceptable salts thereof, particularly formoterol fumarate. Other drugs that can be formulated according to this invention include albuterol, beclomethasone dipropionate, cromolyn, pirbuterol, and pharmaceutically acceptable salts and solvates thereof, particularly albuterol sulfate, disodium cromoglycate, and pirbuterol acetate.

The propellant in a formulation of the invention can be HFC 134a, HFC 227, or a mixture thereof in any proportion. The propellant is present in an amount sufficient to propel a plurality of doses from a metered dose inhaler. The density of HFC 134a differs from the density of HFC 227. Therefore the density of the propellant can be adjusted within limits by using mixtures of HFC 134a and HFC 227 in order to accommodate the density of the drug. It is sometimes preferred that the propellant be selected such that the propellant density is as closely matched as possible to the drug density in order to minimize tendencies for the drug to settle or cream, particularly when drug concentration is greater than 0.1 percent or when the drug concentration is between about 0.1 percent and about 0.5 percent.

The pirbuterol acetate formulations of the invention contain a therapeutically effective amount of pirbuterol acetate. Preferably, the pirbuterol acetate constitutes about 0.4 to about 1.0 percent by weight, more preferably about 0.45 to about 0.9 percent by weight, of the aerosol formulation. Preferably the pirbuterol acetate is micronized.

Ethanol can optionally be included in a pirbuterol acetate aerosol formulation of the invention. When ethanol is present it constitutes from about 0.1 to about 12 percent by weight, preferably from about 5 to about 12 percent by weight of the aerosol formulation. In another aspect of this invention ethanol preferably constitutes from about 2 to about 8 percent by weight of the formulation. Oleic acid can optionally be included in a pirbuterol acetate formulation of the invention that includes ethanol. When oleic acid is present it constitutes about 0.01 to about 0.5 percent by weight of the formulation.

Typically the propellant constitutes the remainder of the weight of the formulation once the pirbuterol acetate and the optional ethanol and oleic acid are accounted for. Accordingly the propellant is generally present in an amount of at least about 85 percent by weight based on the total weight of the formulation. The propellant in a pirbuterol acetate formulation of the invention comprises HFC 227, preferably as substantially the only propellant. However, one or more other propellants such as propellant 142b (1-chloro-1,1-difluoroethane), HFC 134a, and the like can be used, preferably in pirbuterol acetate formulations of the invention containing ethanol.

Preferred pirbuterol acetate formulations of the invention exhibit substantially no growth in particle size or change in crystal morphology of the pirbuterol acetate over a prolonged period, are substantially and readily redispersible, and upon redispersion do not flocculate so quickly as to prevent reproducible dosing of pirbuterol acetate.

The albuterol sulfate formulations of the invention contain a therapeutically effective amount of micronized albuterol sulfate. Preferably micronized albuterol sulfate constitutes about 0.2 to about 0.5 percent by weight, more preferably from about 0.35 to about 0.42 percent by weight of the aerosol formulation.

Ethanol can optionally be included in such an albuterol sulfate formulation of the invention. When ethanol is present it constitutes from about 0.1 to about 20 percent by weight, preferably from about 5 to about 15 percent by weight of the formulation. A surfactant selected from the group consisting of oleic acid and sorbitan trioleate can also optionally be included in the formulation when the formulation also includes ethanol. When a surfactant is present it constitutes about 0.01 to about 0.5 percent by weight of the aerosol formulation. Albuterol sulfate formulations of the invention that do not contain ethanol are preferably substantially free of perfluorinated surfactant.

Certain preferred albuterol sulfate suspension aerosol formulations of the invention comprise HFC 227 as substantially the only propellant. Typically the propellant constitutes the remainder of the weight of the formulation once the albuterol sulfate and the optional surfactant and/or ethanol are accounted for. Accordingly the propellant is generally present in an amount of at least about 75 percent by weight based on the total weight of the formulation.

Preferred albuterol sulfate formulations of the invention exhibit substantially no growth in particle size or change in crystal morphology of the albuterol sulfate over a prolonged period, are substantially and readily redispersible, and upon redispersion do not flocculate so quickly as to prevent reproducible dosing of albuterol sulfate.

Generally the formulations of the invention can be prepared by combining (i) the drug in an amount sufficient to provide a plurality of therapeutically effective doses; and (ii) the propellant in an amount sufficient to propel a plurality of doses from an aerosol canister; and dispersing the drug in the propellant. The drug can be dispersed using a conventional mixer or homogenizer, by shaking, or by ultrasonic energy. Bulk formulation can be transferred to smaller individual aerosol vials by using valve to valve transfer methods or by using conventional cold-fill methods.

The pirbuterol acetate suspension aerosol formulations of this invention can be prepared by combining the pirbuterol acetate and the propellant and then dispersing the pirbuterol acetate in the propellant using a conventional mixer or homogenizer. Pirbuterol acetate, however, is somewhat soluble in ethanol alone. Accordingly, when oleic acid and/or ethanol are included in the formulation, it is preferred that the pirbuterol acetate be first placed in an aerosol vial. A mixture of the propellant, oleic acid and/or ethanol can then be added, and the pirbuterol acetate dispersed in the mixture.

The albuterol sulfate suspension aerosol formulations of this invention can be prepared by combining the albuterol sulfate and the propellant and dispersing the albuterol sulfate in the propellant using a conventional mixer or homogenizer. When a surfactant and/or ethanol are included in the formulation, they can be added to the propellant along with the albuterol sulfate.

Aerosol canisters equipped with conventional valves, preferably metered dose valves, can be used to deliver the formulations of the invention. It has been found, however, that selection of appropriate valve assemblies for use with aerosol formulations is dependent upon the particular surfactants or adjuvants used (if any), on the propellant, and on the particular drug being used. Conventional neoprene and buna valve rubbers used in metered dose valves for delivering conventional CFC formulations often have less than optimal valve delivery characteristics and ease of operation when used with formulations containing HFC 134a or HFC 227. Moreover, conventional CFC formulations generally contain a surfactant in part as a lubricant for the valve stem. Some formulations of the invention, however, do not contain a surfactant or a lubricant. Therefore certain formulations of the invention are preferably dispensed via a valve assembly wherein the diaphragm is fashioned by extrusion, injection molding or compression molding from a thermoplastic elastomeric material such as FLEXOMER.TM. DFDA 1137 NT7 polyolefin, FLEXOMER.TM. DFDA 1138 NT polyolefin, FLEXOMER.TM. DEFD 8923 NT polyolefin, FLEXOMER.TM. GERS 1085 NT polyolefin, FLEXOMER.TM. DFDA 1163 NT7 polyolefin, FLEXOMER.TM. 1491 NT7 polyolefin, FLEXOMER.TM. 9020 NT7 polyolefin, FLEXOMER.TM. 9042 NT polyolefin (Union Carbide), C-FLEX.TM. thermoplastic elastomer R70-001, C-FLEX.TM. thermoplastic elastomer R70-051, C-FLEX.TM. thermoplastic elastomer R70-041, C-FLEX.TM. thermoplastic elastomer R70-085, C-FLEX.TM. thermoplastic elastomer R70-003, or C-FLEX.TM. thermoplastic elastomer R70-026 (Concept Polymer Technologies), or a blend of two or more thereof.

Conventional aerosol canisters, e.g., those of aluminum, glass, stainless steel, or polyethylene terephthalate, can be used to contain a formulation of the invention.

The formulations of the invention can be delivered to the lung by oral inhalation in order to effect bronchodilation or in order to treat a condition susceptible of treatment by inhalation, e.g., asthma, chronic obstructive pulmonary disease. The formulations of the invention can also be delivered by nasal inhalation in order to treat, e.g., allergic rhinitis, rhinitis, or diabetes, or they can be delivered via topical (e.g., buccal) administration in order to treat, e.g., angina or local infection.
 

Claim 1 of 14 Claims

1. A pharmaceutical suspension aerosol formulation consisting essentially of: (i) particulate drug; (ii) 1,1,1,2-tetrafluoroethane as propellant; and (iii) ethanol in an amount of 5 to about 15 percent by weight, wherein the formulation is further characterized in that it contains no surfactant.

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