THE USE OF SOLUBLE FLUOROSURFACTANTS FOR THE PREPARATION OF METERED-DOSE AEROSOL FORMULATIONS

Abstract: Pharmaceutical suspension aerosol formulations using one or more perfluorinated sulfonamido alcohol phosphate esters as surface-active dispersing agents and 1,1,1,2-tetra-fluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, or a mixture thereof, as the propellant.

Description: THE USE OF SOLUBLE FLUOROSURFACTANTS FOR THE PREPARATION OF METERED-DOSE AEROSOL FORMULATIONS TECHNICAL FIELD OF THE INVENTION This invention relates to suspension aerosol formulations suitable for the administration of medicaments. More particularly, it relates to pharmaceutical suspension aerosol formulations using 1,1,1,2-tetrafluoroethane or 1,1,1,2,3,3,3-heptafluoro- propane as the prope11ant. BACKGROUND OF THE INVENTION Pharmaceutical suspension aerosol formulations currently use a mixture of liquid chlorofluorocarbons as the prope1lant. Fluorotrichloromethane, dichlorodifluoromethane and dichlorotetrafluoroethane are the most commonly used propellants in aerosol formulations for administration by inhalation. Chlorofluorocarbons have been implicated in the destruction of the ozone layer and their production is being phased out. Hydrofluorocarbon 134a (HFC-134a, 1,1,1,2-tetrafluoroethane) and hydrofluorocarbon 227 (HFC-227, 1,1,1,2,3,3,3-heptafluoropropane) are viewed as being more ozone friendly than many chlorofluorocarbon propellants; furthermore, they have low toxicity and vapor pressures suitable for use in aerosols. U.S. Pat. No. 4,352,789 discloses a self- propelling, powder dispensing aerosol composition comprising between about 0.001 and 20 percent by weight of a finely-divided solid material coated with a dry coating of a perfluorinated surface-active dispersing agent of a particular type which constitutes between about 0.1 to 20 percent by weight of the coated solid and a halogenated propellant. The solid material can be a medicament. The use of 1,1,1,2-tetrafluoroethane or 1,1,1,2,3,3,3-heptafluoropropane as a propellant is not specifically disclosed. SUMMARY OF THE INVENTION This invention provides suspension aerosol formulations comprising an effective amount of a powdered medicament, between about 0.001 and 0.6 percent by weight of a perfluorinated surface-active dispersing agent and a propellant comprising a hydrofluorocarbon selected from the group consisting of 1,1,1,2- tetrafluoroethane and 1,1,1,2,3,3,3-heptafluoropropane, and a mixture thereof. The perfluorinated surface-active agent is selected from the group consisting of a perfluorinated sulfonamido alcohol phosphate ester having the general formula O [R f SO^RJR'O^PCOH)^ wherein R f is a perfluorinated radical selected from the group consisting of aliphatic and cycloaliphatic C n F-j n -i where n is an integer from about 4 to about 10, R is selected from the group consisting of hydrogen and alkyl having about 4 to about 12 carbon atoms, R' is alkylene having about 2 to about 8 carbon atoms and m is an integer from 1 to 3, and a mixture of two or more of said esters; the formulation exhibiting substantially no growth in particle size or change in crystal morphology of said medicament over a prolonged period, being substantially readily redispersible, and upon redispersion not flocculating so quickly as to prevent reproducible dosing of the medicament. Preferably, the formulation is prepared by combining the dispersing agent and propellant rather than coating the dispersing agent onto the powdered medicament prior to addition of said propellant. The pharmaceutical suspension aerosol formulations of the invention are suitable, for example, for dermal, pulmonary, or mucosal (e.g., buccal or nasal) administration. DETAILED DESCRIPTION OF THE INVENTION The term "suspension aerosol" means that the medicament is in powder form and is substantially insoluble in the propellant. By "prolonged period" as used herein in the context of crystallization is meant at least about four (4) months. The medicament is micronized, that is, over 90 percent of the particles have a diameter of less than about 10 microns. The medicament is generally present in an amount effective to bring about the intended therapeutic effect of the medicament, i.e., an amount such that one or more metered volumes of the formulation contains an effective amount of the drug. The amount of medicament, however, depends on the potency of the particular medicament being formulated. Generally, the medicament constitutes from about 0.01 to 5 percent by weight of the total weight of the formulation, preferably about 0.01 to about 2 percent by weight of the total weight of the formulation. Medicaments for delivery by inhalation include, for example, analgesics, anginal preparations, antiallergics, antibiotics, antihistamines, antiinflammatories, antitussives, bronchodilators, enzymes, hormones, peptides, steroids, or a combination of these. Examples of medicaments falling within the above therapeutic classes are: adrenochrome, albuterol, albuterol sulfate, atropine methylnitrate or sulfate, beclomethasone dipropionate, chlorotetracycline, codeine, colchicine, cortisone, disodium cromoglycate, ephedrine, ephedrine hydrochloride or sulfate, epinephrine bitartrate, fentanyl, flunisolide, formoterol, glucagon, heparin, hydrocortisone, hydroxy- tetracycline, insulin, isoproterenol hydrochloride or sulfate, morphine, nedocromide, neomycin, oscapine, penicillin, phenylephrine bitartrate or hydrochloride, phenylpropanolamine hydrochloride, pirbuterol acetate or -4- hydrochloride, prednisolone, salmeterol, streptomycin, tetracycline, triamcinolone acetonide, and trypsin. Preferred medicaments in the practice of this invention include albuterol, albuterol sulfate, beclomethasone dipropionate, disodium cromoglycate, epinephrine bitartrate, fenoterol hydrobromide, ipratropium bromide, isoproterenol hydrochloride, isoproterenol sulfate, metaproterenol sulfate, phenylephrine bitartrate, phenylephrine hydrochloride, pirbuterol acetate, pirbuterol hydrochloride, procaterol hydrochloride, salmeterol, triamcinolone acetonide, and mixtures thereof. Perfluorinated surface-active dispersing agents useful in the invention are perfluorinated sulfonamido alcohol phosphate esters or mixtures of such compounds that are soluble in 1,1,1,2-tetrafluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, or a mixture thereof. Suitable perfluorinated sulfonamido alcohol phosphate esters include those described in U.S. Pat. No. 3,094,547, which is incorporated herein by reference, having the general formula: [R f S0 2 N(R)R » 0] B P s(OH) 3 - ιn where R f is a perfluorinated radical selected from the group consisting of aliphatic C n F-^ + i and cycloaliphatic c n F 2n -i / where n is an integer from about 4 to about 10, R is selected from the group consisting of hydrogen and alkyl having about 4 to about 12 carbon atoms, R* is alkylene having about 2 to about 8 carbon atoms and m is an integer from 1 to 3. Particularly preferred perfluorinated sulfon- amido alcohol phosphate esters include bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate, tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate, and mixtures thereof. For some medicaments a combination of the bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate and the tris(perfluorooctyl-N-ethylsulfonamidoethyl)- phosphate affords aerosol formulations with superior suspension qualities compared to suspensions obtained by using either ester alone. The total amount of ester and the ratio of the bis(perfluorooctyl-N-ethyl¬ sulfonamidoethyl)phosphate to the tris(perfluorooctyl-N- ethylsulfonamidoethyl)phosphate can be optimized by those skilled in the art for particular medicaments. The perfluorinated surface-active dispersing agent preferably has a solubility of at least 0.1 percent by weight, more preferably at least 0.3 percent by weight, and most preferably at least 0.8 percent by weight in the propellant. The perfluorinated surface-active dispersing agent constitutes from about 0.001 to about 0.6 percent by weight, preferably about 0.001 to about 0.5 percent by weight, of the aerosol formulation. The particular preferred amount depends on the particular medicament being formulated and on the particular surface-active dispersing agent being used. It is preferred to use approximately the minimum amount of agent needed to provide a suitable suspension. The hydrofluorocarbon. or mixture thereof is preferably the only propellant present in the formulations of the invention. However, one or more other propellants such as propellant 142b (l-chloro-l,l-difluoroethane) can also be present. The suspension aerosol formulations of the invention can be prepared by first preparing a solution of the perfluorinated surface-active dispersing agent in the propellant and then suspending the medicament in the solution. In order to prepare a formulation in this manner, the perfluorinated surface-active dispersing agent is placed in an aerosol vial, a continuous valve is crimped onto the vial and the vial is pressure filled with the propellant. The vial is shaken on an automatic shaker until all of the dispersing agent is in solution. The micronized medicament is then placed in a separate aerosol vial, a continuous valve is crimped onto the vial and the vial is pressure filled with the previously prepared solution. The medicament is then dispersed in the solution by mixing or homogenizing. If the medicament being formulated is moisture sensitive, these steps should be performed in a dehumidified atmosphere using only dry materials and equipment. The following examples are provided to illustrate the invention but should not be construed as limiting the invention. In the following examples the quality of the aerosol suspension is rated on a scale of l to 5 with 1 indicating a "poor" suspension and 5 indicating an "excellent" suspension. A poor suspension is characterized by one or more of the following: it has a rapid rate of settling or separation, it is difficult to redisperse after settling or separation, it forms large floes quickly, or it exhibits crystal formation. In contrast, an excellent suspension is slow to settle or separate, is easily redispersed, has minimal flocculation, and exhibits no crystallization or crystal morphology changes. Substantially no crystal formation, relative ease of redispersion, and absence of rapid flocculation after redispersion are important properties in order to provide reproducible dosing of the medicament. Absence of substantial crystal formation provides for maximization of the fraction of the dose deliverable to the target area of the lung. Ease of redispersion permits dosing of a uniform suspension. Finally, rapid flocculation results in a large variation in the dose delivered from the aerosol canister. Suspensions exhibiting a rating of 1 or 2 are not considered desirable in terms of an overall balance of properties of degree of crystallization, ease of redispersibility, and nature of any flocculation, whereas ones exhibiting a rating of 3, 4 or 5 are considered desirable and fall within the scope of this invention. As used in the Examples below, the term "diester" refers to bis(perfluorooctyl-N-ethyl¬ sulfonamidoethyl)phosphate, and the term "triester" refers to tris(perfluorooctyl-N-ethylsulfonamidoethyl)- phosphate. Except as otherwise indicated the propellant in the Examples below is 1,1,1,2-tetrafluoroethane (HFC-134a) . Example 1 A 11.528 mg portion of bis(perfluorooctyl-N- ethylsulfonamidoethyl)phosphate was placed in a 4 ounce vial, the vial was sealed with a continuous valve then pressure filled with 115.65 g of 1,1,1,2- tetrafluoroethane. The vial was then shaken on an automatic shaker for 15 minutes. The resulting stock solution contained 0.01 % by weight of bis(perfluorooctyl-N-ethylsulfonamidoethyl)- phosphate. A 100 mg portion of micronized albuterol sulfate was placed in a 15 cc vial along with 5 mL of glass beads, the vial was sealed with a continuous valve then pressure filled with the previously prepared stock solution. The vial was shaken on a WIG-L-BUG™ mixer for 30 seconds. The resulting suspension contained 0.5% by weight of albuterol sulfate and had a quality rating of 5 (excellent) . Examples 2-13 Using the general method of Example 1, a series of micronized albuterol sulfate suspensions were prepared. Table 1 shows the amount (percent by weight based on the total weight of the formulation) and identity of the surface-active dispersing agent (ratios are weight:weight) used and the quality rating of the suspension. The suspensions of Examples 2 and 3 contained 0.5% by weight of albuterol sulfate, that of Example 4 contained 0.46% by weight and the remaining Examples contained 0.45 % by weight of albuterol sulfate. Using the general method of Example 1, a series of suspension aerosol formulations containing 0.5% percent by weight micronized pirbuterol hydrochloride was prepared. Table 2 shows the amount (percent by weight based on the total weight of the formulation) and identity of the surface-active dispersing agent used and the suspension quality rating. Table 2 Using the general method of Example 1, a series of aerosol suspension formulations containing 1.6% by weight based on the total weight of the formulation of micronized disodium cromoglycate was prepared. Table 3 shows the amount (percent by weight based on the total weight of the formulation) and identity (ratios are weight:weight) of the surface-active dispersing agent used and the suspension quality rating. Table 3 Using the general method of Example 1, a series of suspension aerosol formulations containing 0.45% by weight of micronized pirbuterol acetate was prepared. Table 4 shows the amount (percent by weight based on the total weight of the formulation) and identity (ratios are weight: eight) of the surface-active dispersing agent used and the suspension quality rating. Table 4 Using the general method of Example 1, a series of suspension aerosol formulations containing 0.5% by weight based on the total weight of the formulation of micronized epinephrine bitartrate was prepared. Table 5 shows the amount (percent by weight based on the total weight of the formulation) and identity (ratios are weight: eight) of the surface-active dispersing agent used and the suspension quality rating. Table 5 A 16.6 mg portion of perfluorooctyl-N- ethylsulfonamidoethylphosphate was mixed with 1 g of ethanol in a 4 gram glass vial. The resulting solution was transferred to a 4 ounce glass aerosol vial which was then sealed with a continuous valve and pressure filled with 100 g of 1,1,1,2-tetrafluoroethane to give a stock solution containing 0.016 percent by weight of the ester and 1 percent by weight of ethanol. A 100 mg portion of micronized albuterol sulfate was placed in a 15 cc glass vial along with 5 mL of glass beads, the vial was sealed with a continuous valve and then pressure filled with the stock solution. The vial was placed on a WIG-L-BUG™ mixer for at least 30 seconds. The resulting suspension contained 0.5% by weight of albuterol sulfate and had a quality rating of 2. Example 48 Using the general method of Example 47, a suspension aerosol containing 0.5% by weight of micronized albuterol sulfate, 0 * 05% by weight of perfluoroocty1-N-ethylsulfonamidoethyIphosphate, 1.2% by weight of ethanol and 1,1,1,2-tetrafluoroethane was prepared. The resulting suspension had a quality rating of 1. Example 49 Using the general method of Example 47, a suspension aerosol containing 0.5% by weight of micronized albuterol sulfate, 0.005% by weight of perfluorooctyl-N-ethylsulfonamidoethyIphosphate, 0.5% by weight of ethanol and 1,1,1,2-tetrafluoroethane was prepared. The resulting suspension had a quality rating of 4. Example 50 A 10.0 mg portion of bis(per luorooctyl-N- ethylsulfonamidoethyl)phosphate and a 50.7 mg portion of tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate were placed in a vial, the vial was sealed with a continuous valve then pressure filled with 99.879 g of 1,1,1,2-tetrafluoroethane. The resulting stock solution contained 0.01% by weight of bis(perfluorooctyl-N- ethylsulfonamidoethyl)phosphate and 0.05% by weight of tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate. A 30 mg portion of micronized beclomethasone dipropionate was placed in a vial along with 3 mL of glass beads, the vial was sealed with a continuous valve and pressure filled with 10 g of the previously prepared stock solution. The vial was placed on a WIG-L-BUG™ mixer for at least 30 seconds. The resulting suspension contained 0.3% by weight of beclomethasone dipropionate and had a quality suspension rating of 4 (excellent) . Examples 51-55 Using the general method of Example 50 and the stock solution prepared in Example 50, a series of suspension aerosols was prepared. Table 6 shows the amount (percent by weight based on the total weight of the formulation) and identity of the medicament used and the quality rating of the suspension. All of the suspensions contained 0.01% by weight of bis(perfluorooctyl-N-ethylsulfonamidoethyl) hosphate and 0.05% by weight of tris(perfluorooctyl-N- ethylsulfonamidoethyl)phosphate. Table 6 Example Medicament Rating 51 0.3% triamcinolone acetonide 5 52 0.5% pirbuterol acetate 5 53 1.5% disodium cromoglycate 5 54 0.5% albuterol sulfate 5 55 0.45% salmeterol 3 Examples 56-58 Using the general method of Example 1, a series of suspension aerosol formulations containing 0.1% by weight of micronized salmeterol was prepared. Table 7 shows the amount (percent by weight based on the total weight of the formulation) and identity of the surface-active dispersing agent used and the suspension quality rating. Table 7 A series of suspension aerosol formulations in which 1,1,1,2,3,3,3-heptafluoropropane (HFC-227) serves as the propellant was prepared using the general method of Example 1. Table 8 shows the amount (percent by weight based on the total weight of the formulation) and identity of the surface-active dispersing agent used and the suspension quality rating. The formulations of Examples 59-61 contained 0.3 percent by weight based on the total weight of the formulation of -14- icronized triamcinolone acetonide. Those of Examples 62-64 contained 0.5 percent by weight of micronized pirbuterol acetate. Table 8 In the claims that follow, all weight percentages are based on the total weight of the formulation unless otherwise stated.

Claims: WHAT IS CLAIMED IS: 1. A suspension aerosol formulation, comprising: a propellant comprising a hydrofluorocarbon selected from the group consisting of 1,1,1,2- tetrafluoroethane and 1,1,1,2,3,3,3-heptafluoropropane, and a mixture thereof; a therapeutically effective amount of a powdered medicament; and between about 0.001 and 0.6 percent by weight of a surface-active dispersing agent of the formula 0 [R f SO^Rj 'O^PfOH)^ wherein R, is a perfluorinated radical selected from the group consisting of aliphatic C n F^-n and cycloaliphatic c n F 2n -ι where n is an integer from about 4 to about 10, R is selected from the group consisting of hydrogen and alkyl having about 4 to about 12 carbon atoms, R* is alkylene having about 2 to about 8 carbon atoms and m is an integer from 1 to 3, and mixture of two or more of said esters; the formulation exhibiting substantially no growth in particle size or change in crystal morphology of said medicament over a prolonged period, being substantially readily redispersible, and upon redispersion not flocculating so quickly as to prevent reproducible dosing of the medicament. 2. A suspension aerosol formulation according to Claim 1 wherein said powdered medicament is present in an amount of about 0.01 to 2 percent by weight; said formulation being prepared by combining said dispersing agent and propellant rather than coating said dispersing agent onto said powdered medicament prior to addition of said propellant. -16- 3. A suspension aerosol formulation according to Claim 1 wherein said dispersing agent is present in an amount of about 0.001 to 0.5 percent by weight. 4. A suspension aerosol formulation according to Claim 1 wherein said dispersing agent has a solubility of at least 0.3 percent by weight in said propellant. 5. A suspension aerosol formulation according to Claim 4 wherein said dispersing agent has a solubility of at least 0.8 percent by weight in said propellant. 6. A suspension aerosol formulation according to Claim 1 wherein said dispersing agent is selected from the group consisting of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate, tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate, and mixtures thereof. 7. A suspension aerosol formulation according to Claim 1 wherein said medicament is selected from the group consisting of an analgesic, an anginal preparation, an antiallergic, an antibiotic, an antihistamine, an antiinflam atory, an antitussive, a bronchodilator, an enzyme, a hormone, a peptide, a steroid, and mixtures thereof. 8. A suspension aerosol formulation according to Claim 1 wherein said medicament is selected from the group consisting of albuterol, albuterol sulfate, beclomethasone dipropionate, disodium cromoglycate, epinephrine bitartrate, fenoterol hydrobromide, ipratropium bromide, isoproterenol hydrochloride, isoproterenol sulfate, metaproterenol sulfate, phenylephrine bitartrate, phenylephrine hydrochloride, pirbuterol acetate, pirbuterol hydrochloride, procaterol hydrochloride, salmeterol, triamcinolone acetonide, and mixtures thereof. 9. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising between 0.1 and 1.0 percent by weight of albuterol sulfate having a substantially uniform particle size of less than about 10 microns in diameter, and between about 0.008 and about 0.06 percent by weight of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate. 10. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising between about 0.5 and about 2 percent by weight of disodium cromoglycate having a substantially uniform particle size of less than about 10 microns in diameter, and between about 0.05 and about 0.4 percent by weight of a mixture of bis(perfluorooctyl-N- ethylsulfonamidoethyl)phosphate and tris(perfluoro¬ octy1-N-ethylsulfonamidoethy1)phosphate. 11. A suspension aerosol formulation according to Claim 10 wherein said bis(perfluorooctyl- N-ethylsulfonamidoethyl)phosphate and said tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate are present in about equal amounts by weight. 12. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising between about 0.1 and about 1 percent by weight of epinephrine bitartrate having a substantially uniform particle size of less than about 10 microns in diameter, and between about 0.02 and about 0.07 percent by weight of a mixture of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate and tris(perfluorooctyl-N-ethylsulfonamidoethyl)- phosphate. 13. A suspension aerosol formulation according to Claim 12 wherein said bis(perfluorooctyl-N-ethyl¬ sulfonamidoethyl)phosphate and said tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate are present in about equal amounts by weight. 14. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising between about 0.1 and about 1 percent by weight of epinephrine bitartrate having a substantially uniform particle size of less than about 10 microns in diameter, and between about 0.02 and about 0.07 percent by weight of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate. 15. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising between about 0.1 and about 1 percent by weight of pirbuterol hydrochloride having a substantially uniform particle size of less than about 10 microns in diameter, and between about 0.03 and about 0.3 percent by weight of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate. 16. A suspension aerosol formulation according to Claim 1 comprising between about 0.1 and about 1.0 percent by weight of albuterol sulfate having a substantially uniform particle size of less than about 10 microns in diameter, and between about 0.004 and about 0.02 percent by weight of a mixture of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate and tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate, with the proviso that the ratio by weight of said bis ester to said tris ester is about 8:1 to about 1:4. 17. A suspension aerosol formulation according to Claim 1, prepared by combining the dispersing agent and the propellant rather than coating the dispersing agent onto the powdered medicament prior to addition of said propellant. 18. A suspension aerosol formulation according to Claim 1 comprising 1,1,1,2-tetrafluoroethane as essentially the only propellant. 19. A suspension aerosol formulation according to Claim l comprising 1,1,1,2,3,3,3-heptafluoropropane as essentially the only propellant. 20. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising: about 0.02 to about 0.07 percent by weight of a mixture of about one part by weight bis(perfluorooctyl-N-ethyl sulfonamidoethyl)phosphate and about five parts by weight tris(perfluorooctyl-N-ethylsulfonamidoethyl)- phosphate; and a medicament having substantially uniform particle size of less than about 10 microns in diameter selected from the group consisting of beclomethasone dipropionate in an amount of about 0.1 to about 0.5 percent by weight, triamcinolone acetonide in an amount of about 0.1 to about 0.5 percent by weight, pirbuterol acetate in an amount of about 0.3 to about 0.7 percent by weight, disodium chromoglycate in an amount of about 1.0 to about 2.0 percent by weight, albuterol sulfate in an amount of about 0.3 to about 0.7 percent by weight, and salmeterol in an amount of about 0.4 to about 0.5 percent by weight. 21. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2-tetrafluoroethane is essentially the only propellant, and comprising about 0.05 to about 0.2 percent by weight of salmeterol having a substantially uniform particle size of less than about 10 microns in diameter and about 0.001 to about 0.01 percent by weight bis(perfluorooctyl-N-ethylsulfonamido¬ ethy1)phosphate. -20- 22. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2,3,3,3-heptafluoropropane is essentially the only propellant and comprising about 0.1 to about 0.5 percent by weight triamcinolone acetonide having a substantially uniform particle size of less than about 10 microns in diameter and about 0.005 to about 0.05 percent by weight of a dispersing agent selected from the group consisting of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate and a mixture of bis(perfluorooctyl-N-ethyl¬ sulfonamidoethyl)phosphate and tris(perfluorooctyl-N- ethylsulfonamidoethyl)phosphate. 23. A suspension aerosol formulation according to Claim 1 wherein 1,1,1,2,3,3,3-heptafluoropropane is essentially the only propellant and comprising about 0.3 to about 0.7 percent by weight pirbuterol acetate having a substantially uniform particle size of less than about 10 microns in diameter and about 0.005 to about 0.05 percent by weight of a dispersing agent selected from the group consisting of bis(perfluorooctyl-N-ethyl¬ sulfonamidoethyl)phosphate and a mixture of bis(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate and tris(perfluorooctyl-N-ethylsulfonamidoethyl)phosphate.

Inventors: MORIS ROBERT A, SCHULTZ DAVID W, SCHULTZ ROBERT K, THIEL CHARLES G, MORIS, ROBERT, A., SCHULTZ, DAVID, W., SCHULTZ, ROBERT, K., THIEL, CHARLES, G.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1991
Main classification: A61K9
IPC codes: A61K9, A61K47