The present invention relates to the delivery of antihistamines through an inhalation route. Specifically, it relates to aerosols containing antihistamines that are used in inhalation therapy. In a method aspect of the present invention, an antihistamine is delivered to a patient through an inhalation route. The method comprises: a) heating a composition, wherein the composition comprises an antihistamine, to form a vapor; and, b) allowing the vapor to cool, thereby forming a condensation aerosol comprising particles with less than 5% antihistamine drug degradation products. In a kit aspect of the present invention, a kit for delivering an antihistamine through an inhalation route is provided which comprises: a) a thin coating of an antihistamine drug composition and b) a device for dispensing said thin coating as a condensation aerosol.

DETAILED DESCRIPTION OF THE INVENTION

Formation of Antihistamine Containing Aerosols

Any suitable method is used to form the aerosols of the present invention. A preferred method, however, involves heating a composition comprising an antihistamine to form a vapor, followed by cooling of the vapor such that it condenses to provide an antihistamine comprising aerosol (condensation aerosol). The composition is heated in one of four forms: as pure active compound (e.g., pure azatadine, brompheniramine, carbinoxamine, chlorpheniramine, clemastine, cyproheptadine, loratadine, pyrilamine, hydroxyzine, or promethazine); as a mixture of active compound and a pharmaceutically acceptable excipient; as a salt form of the pure active compound; and, as a mixture of active compound salt form and a pharmaceutically acceptable excipient.

Salt forms of antihistamines (e.g., azatadine, brompheniramine, carbinoxamine, chlorpheniramine, clemastine, cyproheptadine, loratadine, pyrilamine, hydroxyzine, or promethazine) are either commercially available or are obtained from the corresponding free base using well known methods in the art. A variety of pharmaceutically acceptable salts are suitable for aerosolization. Such salts include, without limitation, the following: hydrochloric acid, hydrobromic acid, acetic acid, maleic acid, formic acid, and fumaric acid salts.

Pharmaceutically acceptable excipients may be volatile or nonvolatile. Volatile excipients, when heated, are concurrently volatilized, aerosolized and inhaled with the antihistamine. Classes of such excipients are known in the art and include, without limitation, gaseous, supercritical fluid, liquid and solid solvents. The following is a list of exemplary carriers within the classes: water; terpenes, such as menthol; alcohols, such as ethanol, propylene glycol, glycerol and other similar alcohols; dimethylformamide; dimethylacetamide; wax; supercritical carbon dioxide; dry ice; and mixtures thereof.

Solid supports on which the composition is heated are of a variety of shapes. Examples of such shapes include, without limitation, cylinders of less than 1.0 mm in diameter, boxes of less than 1.0 mm thickness and virtually any shape permeated by small (e.g., less than 1.0 mm-sized) pores. Preferably, solid supports provide a large surface to volume ratio (e.g., greater than 100 per meter) and a large surface to mass ratio (e.g., greater than 1 cm.sup.2 per gram).

A solid support of one shape can also be transformed into another shape with different properties. For example, a flat sheet of 0.25 mm thickness has a surface to volume ratio of approximately 8,000 per meter. Rolling the sheet into a hollow cylinder of 1 cm diameter produces a support that retains the high surface to mass ratio of the original sheet but has a lower surface to volume ratio (about 400 per meter).

A number of different materials are used to construct the solid supports. Classes of such materials include, without limitation, metals, inorganic materials, carbonaceous materials and polymers. The following are examples of the material classes: aluminum, silver, gold, stainless steel, copper and tungsten; silica, glass, silicon and alumina; graphite, porous carbons, carbon yarns and carbon felts; polytetrafluoroethylene and polyethylene glycol. Combinations of materials and coated variants of materials are used as well.

Where aluminum is used as a solid support, aluminum foil is a suitable material. Examples of silica, alumina and silicon based materials include amphorous silica S-5631 (Sigma, St. Louis, Mo.), BCR171 (an alumina of defined surface area greater than 2 m.sup.2/g from Aldrich, St. Louis, Mo.) and a silicon wafer as used in the semiconductor industry. Carbon yarns and felts are available from American Kynol, Inc., New York, N.Y. Chromatography resins such as octadecycl silane chemically bonded to porous silica are exemplary coated variants of silica.

The heating of the antihistamine compositions is performed using any suitable method. Examples of methods by which heat can be generated include the following: passage of current through an electrical resistance element; absorption of electromagnetic radiation, such as microwave or laser light; and, exothermic chemical reactions, such as exothermic salvation, hydration of pyrophoric materials and oxidation of combustible materials.

Delivery of Antihistamine Containing Aerosols

Antihistamine containing aerosols of the present invention are delivered to a mammal using an inhalation device. Where the aerosol is a condensation aerosol, the device has at least three elements: an element for heating an antihistamine containing composition to form a vapor; an element allowing the vapor to cool, thereby providing a condensation aerosol; and, an element permitting the mammal to inhale the aerosol. Various suitable heating methods are described above. The element that allows cooling is, in it simplest form, an inert passageway linking the heating means to the inhalation means. The element permitting inhalation is an aerosol exit portal that forms a connection between the cooling element and the mammal's respiratory system.

One device used to deliver an antihistamine containing aerosol is described in reference to FIG. 1 (see Original Patent). Delivery device 100 has a proximal end 102 and a distal end 104, a heating module 106, a power source 108, and a mouthpiece 110. An antihistamine composition is deposited on a surface 112 of heating module 106. Upon activation of a user activated switch 114, power source 108 initiates heating of heating module 106 (e.g, through ignition of combustible fuel or passage of current through a resistive heating element). The antihistamine composition volatilizes due to the heating of heating module 106 and condenses to form a condensation aerosol prior to reaching the mouthpiece 110 at the proximal end of the device 102. Air flow traveling from the device distal end 104 to the mouthpiece 110 carries the condensation aerosol to the mouthpiece 110, where it is inhaled by the mammal.

Devices, if desired, contain a variety of components to facilitate the delivery of antihistamine containing aerosols. For instance, the device may include any component known in the art to control the timing of drug aerosolization relative to inhalation (e.g., breath-actuation), to provide feedback to patients on the rate and/or volume of inhalation, to prevent excessive use (i.e., "lock-out" feature), to prevent use by unauthorized individuals, and/or to record dosing histories.

Dosage of Antihistamine Containing Aerosols

The dosage amount of antihistamine in aerosol form is generally no greater than twice the standard dose of the drug given orally. For instance, for the treatment of allergy symptoms azatadine, brompheniramine, carbinoxamine, chlorpheniramine, clemastine, cyproheptadine, loratadine, pyrilamine, hydroxyzine and promethazine are typically provided orally at the following respective strengths: 1 mg, 4 mg, 4 mg, 2 mg, 1.34 mg, 4 mg, 10 mg, 30 mg, 25 mg, and 25 mg. As aerosols, the compounds are generally provided in the following amounts per inspiration for the same indication: azatadine, 0.2 mg to 2.5 mg; clemastine, 0.25 mg to 6 mg; chlorpheniramine, 0.5 mg to 5 mg; brompheniramine, 0.8 mg to 10 mg; carbinoxamine, 0.8 mg to 10 mg; cyproheptadine, 0.8 mg to 10 mg; loratadine, 2 mg to 25 mg; promethazine, 5 mg to 60 mg; hydroxyzine, 2 mg to 100 mg; and, pyrilamine, 6 mg to 70 mg. A typical dosage of an antihistamine aerosol is either administered as a single inhalation or as a series of inhalations taken within an hour or less (dosage equals sum of inhaled amounts). Where the drug is administered as a series of inhalations, a different amount may be delivered in each inhalation.

One can determine the appropriate dose of an antihistamine containing aerosol to treat a particular condition using methods such as animal experiments and a dose-finding (Phase I/II) clinical trial. One animal experiment involves measuring plasma concentrations of drug in an animal after its exposure to the aerosol. Mammals such as dogs or primates are typically used in such studies, since their respiratory systems are similar to that of a human. Initial dose levels for testing in humans is generally less than or equal to the dose in the mammal model that resulted in plasma drug levels associated with a therapeutic effect in humans. Dose escalation in humans is then performed, until either an optimal therapeutic response is obtained or a dose-limiting toxicity is encountered.

 

Claim 1 of 53 Claims

1. A method of treating allergy symptoms in a patient comprising administering a therapeutic amount of a drug condensation aerosol to the patient by inhalation, wherein the drug is selected from the group consisting of azatadine, brompheniramine, carbinoxamine, chlorpheniramine, clemastine, cyproheptadine, loratadine, pyrilamine, hydroxyzine and promethazine, and wherein the condensation aerosol is formed by heating a thin layer containing the drug, on a solid support, to produce a vapor of the drug, and condensing the vapor to form a condensation aerosol characterized by less than 10% drug degradation products by weight, and an MMAD of less than 5 microns.

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