United States Patent 4,364,923: Scope, Claims, Expiration, and Beclomethasone Aerosol Patent Landscape

U.S. Patent 4,364,923 protected stabilized suspension aerosols containing inhalable corticosteroid crystals, particularly beclomethasone dipropionate solvates suspended in chlorofluorocarbon propellants. The patent issued on December 21, 1982, and its 17-year term expired on December 21, 1999, absent an unusual extension or adjustment. It therefore has no current blocking effect in the United States.

The patent was commercially important because it addressed crystal growth in suspension metered-dose inhalers. Its claims focused on the physical form of the steroid, the propellant environment, inhalable particle size, and metered-dose delivery. The claims do not broadly cover beclomethasone dipropionate, inhaled corticosteroids, or all aerosol formulations. They are limited to specified crystalline-solvate and suspension characteristics, with several claims tied to obsolete CFC propellants.

What patent is U.S. Patent 4,364,923?

Item	Data
Patent	U.S. Patent No. 4,364,923
Title	Aerosol formulations
Patent type	Pharmaceutical formulation and drug-delivery patent
Priority era	Late 1970s
Issue date	December 21, 1982
Original statutory term	17 years from issue for the applicable pre-1995 application regime
Estimated expiration	December 21, 1999
Principal technology	Suspension aerosol containing crystalline steroid solvates
Principal drug	Beclomethasone 17,21-dipropionate, also called beclomethasone dipropionate
Propellants expressly claimed	Trichlorofluoromethane, dichlorodifluoromethane, and trichlorotrifluoroethane
Current enforceability	Expired

The patent record identifies the invention as an aerosol formulation technology associated with Glaxo Group Limited. The patent predates the modern 20-year term measured from the earliest effective nonprovisional filing date. Its original term was therefore governed by the former 17-year-from-issue framework.[1]

What problem did the patent solve?

The invention addressed physical instability in suspension inhalers. Steroid crystals dispersed in a propellant can grow during storage. Excessive crystal growth can cause:

poor suspension uniformity;
inconsistent metered doses;
valve or actuator blockage;
reduced respirable fraction;
changes in aerodynamic particle-size distribution; and
diminished delivery to the bronchial system.

The patent sought to stabilize the steroid in the propellant by using a crystalline solvate or a partially or completely desolvated form of that solvate. It also required the steroid particles to remain sufficiently small for bronchial inhalation.

The technology was directed to pressurized metered-dose inhalers using CFC propellants. Those propellants were widely used in early inhaled corticosteroid products but were later phased out under the Montreal Protocol and related U.S. regulatory measures.[2]

How many independent claims does U.S. Patent 4,364,923 have?

The supplied claims contain two principal independent formulation claims:

Claim 1, which covers a broad class of steroid aerosol formulations.
Claim 11, which focuses specifically on beclomethasone dipropionate.

Claims 2 through 10 depend from claim 1 or its intervening limitations. Claim 12 depends from claim 11.

Claim	Principal subject matter	Claim category
1	Anti-inflammatory steroid crystalline solvate or partly/completely desolvated solvate in aerosol propellant, stabilized against crystal growth, with inhalable particle size	Independent formulation claim
2	Claim 1 limited to beclomethasone dipropionate	Dependent formulation claim
3	Claim 1 limited to specified betamethasone derivatives	Dependent formulation claim
4	Claim 1 limited to trichlorofluoromethane	Dependent formulation claim
5	Claim 1 limited to dichlorodifluoromethane or trichlorotrifluoroethane	Dependent formulation claim
6	Particle size below 20 microns	Dependent particle-size claim
7	Particle size from 2 to 5 microns	Dependent particle-size claim
8	Beclomethasone dipropionate with trichlorofluoromethane	Dependent formulation claim
9	Metered-dose container delivering 10 to 1,000 micrograms	Dependent device and dosage claim
10	Beclomethasone dipropionate, trichlorofluoromethane, and 30 to 80 micrograms per dose	Dependent dosage claim
11	Beclomethasone dipropionate crystalline solvate suspension with stabilized crystal growth and inhalable particle size	Independent formulation claim
12	Claim 11 using a halogenated hydrocarbon propellant	Dependent formulation claim

What does claim 1 cover?

Claim 1 requires each of the following elements:

An aerosol formulation.
An aerosol propellant.
An anti-inflammatory steroid suspended in the propellant.
The steroid in the form of a crystalline solvate with a halogenated hydrocarbon, or in a form from which some or all of the halogenated hydrocarbon has been removed.
The halogenated hydrocarbon having one or two carbon atoms and being a chloro or chlorofluoro hydrocarbon.
Stabilization against further crystal growth in the propellant.
A particle size permitting inhalation into the bronchial system.

The claim is not satisfied merely because a corticosteroid is present in an aerosol. The formulation must use the specified crystalline-solvate or desolvated-solvate concept and must meet the crystal-growth and inhalation-particle requirements.

What is the significance of the crystalline-solvate limitation?

The crystalline-solvate limitation is the central technical limitation. A solvate is a crystal structure that incorporates solvent molecules into the crystal lattice. In this patent, the solvent is a halogenated hydrocarbon associated with the steroid crystal.

The language also covers a crystalline solvate from which part or all of the halogenated hydrocarbon has been removed. That wording potentially reaches:

partially desolvated crystals;
completely desolvated crystals retaining a relevant crystal form; and
material prepared from the original solvate where the desolvation process preserves the claimed physical characteristics.

The claim does not necessarily cover every polymorph or every crystalline form of beclomethasone dipropionate. A product would need to satisfy the claim's structural and functional limitations.

What does "stabilized with respect to further growth" require?

This is a functional limitation tied to crystal-growth behavior in the propellant. A formulation would need to show that the steroid does not undergo unacceptable additional crystal growth under relevant storage or use conditions.

The limitation creates potential proof issues in an infringement dispute. Relevant evidence could include:

microscopy;
particle-size distribution before and after storage;
X-ray diffraction;
differential scanning calorimetry;
solvate-content analysis;
suspension stability studies; and
dose-uniformity testing.

The claim is stronger against a formulation that uses the same crystal form and demonstrates the same stability mechanism. It is weaker against a formulation using a different crystal form, a solution rather than a suspension, or a non-CFC propellant system that avoids the claimed solvate behavior.

What do claims 2 through 5 add?

Claim 2 narrows claim 1 to beclomethasone 17,21-dipropionate. This is the commercially most relevant species in the patent.

Claim 3 covers specified betamethasone derivatives:

betamethasone 21-acetate-17-isobutyrate; and
21-chloro-21-desoxy betamethasone-17-propionate.

Claims 4 and 5 limit the propellant:

Claim 4: trichlorofluoromethane, commonly known as CFC-11.
Claim 5: dichlorodifluoromethane, commonly known as CFC-12, or trichlorotrifluoroethane, commonly known as CFC-113.

These limitations sharply restrict the claims to historical CFC systems. Modern hydrofluoroalkane products using HFA-134a or HFA-227 do not literally satisfy a claim requiring one of the expressly specified CFC propellants.

What particle sizes are protected?

Claims 6 and 7 add numerical particle-size limitations:

Claim	Particle-size limitation
6	Less than 20 microns
7	From 2 to 5 microns

These are relatively broad geometric size ranges compared with modern inhalation specifications, which often rely on aerodynamic diameter, fine-particle fraction, mass median aerodynamic diameter, and delivered-dose uniformity.

The patent language refers to particle size sufficient for bronchial inhalation. A technical dispute could therefore distinguish between:

geometric particle size;
aerodynamic particle size;
agglomerated particle size;
primary crystal size; and
the particle-size distribution of the emitted aerosol.

Claim 7 is narrower than claim 6 because it requires a 2-to-5-micron range. Claim 6 may cover a broader set of crystals but still requires compliance with the other formulation limitations.

What dose and device limitations are in claims 9 and 10?

Claim 9 requires an aerosol container equipped with a metering valve and a metered dose containing 10 to 1,000 micrograms of steroid.

Claim 10 narrows the combination to:

beclomethasone dipropionate;
trichlorofluoromethane; and
a 30-to-80-microgram steroid dose.

These claims add a delivery-device and dose limitation. They do not independently cover a metering valve containing any drug. The formulation must first satisfy the underlying claim 1 requirements.

The dose range is also not equivalent to the nominal label strength of a modern inhaler unless the measurement basis is the same. Relevant distinctions include:

drug amount in the formulation;
metered amount leaving the valve;
emitted dose;
delivered dose after actuator losses; and
respirable dose entering the lungs.

What does claim 11 protect?

Claim 11 is the most commercially important independent claim because it specifically identifies beclomethasone dipropionate.

It requires:

an aerosol formulation;
an aerosol propellant;
suspended beclomethasone dipropionate;
beclomethasone dipropionate in crystalline-solvate form;
stabilization against further crystal growth in the propellant; and
particle size permitting bronchial inhalation.

Unlike claim 1, claim 11 does not expressly require a halogenated hydrocarbon in the claim itself. Claim 12 adds that limitation. Claim 11 is therefore textually broader with respect to propellant chemistry, although its scope remains limited by the crystalline-solvate, suspension, stabilization, and inhalability requirements.

This distinction is important in claim-charting. A formulation using a non-halogenated propellant could potentially fall outside claim 12 while still requiring analysis under claim 11, depending on the product's crystal form and technical characteristics.

When did U.S. Patent 4,364,923 lose exclusivity?

The patent expired on December 21, 1999, based on the 17-year term from its issue date.[1] The patent was issued before the change to the modern patent-term system enacted in the Uruguay Round Agreements Act.

Event	Date
Patent issued	December 21, 1982
Standard term under applicable law	17 years from issue
Patent expiration	December 21, 1999
Post-expiration status	Public domain

No current manufacturer faces patent infringement liability based solely on practicing an expired claim of U.S. Patent 4,364,923. The patent may remain relevant as prior art, historical evidence, or a source of technical disclosure, but it cannot support a new U.S. infringement action.

What is the Orange Book status of U.S. Patent 4,364,923?

U.S. Patent 4,364,923 is not a current Orange Book barrier. The FDA Orange Book lists patents and exclusivity associated with approved drug products, but an expired patent does not create current Hatch-Waxman patent protection.[3]

The patent was associated with the technical generation of CFC beclomethasone inhalers, including products historically marketed under brands such as Beclovent and Vanceril. Those products were later discontinued or replaced as CFC inhalers were removed from the U.S. market.

Modern beclomethasone products, including HFA-based products such as QVAR and QVAR RediHaler, depend on later formulation, device, manufacturing, and regulatory records rather than on the expired 1982 patent.

What FDA regulatory changes affected the patented technology?

The patent's named propellants are CFCs. U.S. FDA and EPA policy progressively eliminated CFC-containing metered-dose inhalers because of ozone-depletion concerns.[2][4]

The regulatory transition changed the commercial patent landscape in three ways:

CFC formulation claims became commercially obsolete.
Product sponsors developed HFA formulations and redesigned inhaler systems.
Later patents focused on HFA propellant systems, solution formulations, ethanol content, valve design, actuator geometry, particle engineering, and dose delivery.

HFA products can require a different technical analysis from the CFC suspensions described in Patent 4,364,923. A later HFA product does not infringe the expired patent merely because it contains beclomethasone dipropionate and delivers it by metered inhalation.

How does the patent compare with later beclomethasone aerosol patents?

Technology generation	Typical propellant	Physical form	Principal patent focus	Relationship to Patent 4,364,923
Early CFC suspension inhalers	CFC-11, CFC-12, CFC-113	Crystalline steroid suspension, including solvates	Crystal-growth control and respirable particle size	Directly within the historical field
HFA suspension inhalers	HFA-134a or HFA-227	Suspension with engineered particles or excipients	HFA compatibility, suspension stability, device performance	Usually outside the express CFC limitations
HFA solution inhalers	HFA, often with ethanol or cosolvent	Drug dissolved rather than suspended	Solubility, vapor pressure, dose delivery, formulation stability	Generally outside suspension and crystalline-solvate limitations
Breath-actuated or redesigned devices	HFA or dry-powder systems	Suspension, solution, or dry powder	Valve, actuator, dose-counter, airflow, and delivery mechanics	Requires separate later patent analysis

The most relevant later patent rights were directed to HFA reformulation and delivery systems. Those rights are separate from the expired CFC-solvate claims and must be analyzed patent by patent.

What patent infringement risks exist for generic beclomethasone inhalers?

There is no current infringement risk from Patent 4,364,923 itself. A generic or authorized generic sponsor could not be sued on that patent after its expiration.

Current risk may instead arise from later patents covering:

HFA formulation composition;
suspension stabilizers;
ethanol or other cosolvents;
beclomethasone particle engineering;
inhaler valve and actuator systems;
dose counters;
breath-actuation mechanisms;
container coatings;
manufacturing processes; and
method-of-use claims for specific patient populations or dosing regimens.

A Paragraph IV challenge would therefore target any unexpired patents listed for the relevant reference product, not Patent 4,364,923. The statutory certification would assert that a listed patent is invalid, unenforceable, or not infringed. An expired patent cannot produce the ordinary 30-month stay associated with a current Orange Book patent challenge.[5]

Are biosimilar or biologic issues relevant?

No. Beclomethasone dipropionate is a chemically synthesized small molecule, not a biologic. Biosimilar provisions under the Public Health Service Act are irrelevant.

The relevant competitive pathways are:

abbreviated new drug applications for suitable generic products;
505(b)(2) applications for reformulated or differently delivered products; and
full or supplemental NDA pathways for new inhaler devices and formulations.

The principal regulatory issue is pharmaceutical equivalence and therapeutic equivalence, not biosimilarity.

Which companies challenged or litigated this patent?

No current litigation can be based on Patent 4,364,923 because the patent expired in 1999. The supplied record does not establish a material present-day Paragraph IV case, settlement, or license involving this patent.

Historically, the patent's commercial significance was tied to branded CFC beclomethasone inhalers and the transition to replacement products. Later competition centered on HFA reformulations and other inhaled corticosteroids, including budesonide, fluticasone propionate, fluticasone furoate, mometasone furoate, and ciclesonide.

The absence of current enforceability is more important for transaction diligence than any historical litigation involving the patent. A license to Patent 4,364,923 alone would have no meaningful U.S. exclusivity value today.

How strong is the patent estate for the claimed technology?

Historical strength

The patent had meaningful historical value because it combined several practical formulation limitations:

a defined steroid crystal form;
a CFC propellant environment;
resistance to crystal growth;
inhalable particle size;
optional metering-valve delivery; and
specific dose ranges.

The combination could distinguish ordinary steroid suspensions and address a recognized manufacturing and product-performance problem.

Current strength

The current legal strength is zero as an exclusionary right because the patent expired. Its residual value is limited to:

prior-art analysis;
freedom-to-operate history;
technical benchmarking;
formulation-development reference material; and
assessment of historical product architecture.

The claims are also commercially narrow for modern products because they emphasize CFC propellants that are no longer used in current U.S. metered-dose inhalers.

What geographic coverage does the patent provide?

The patent provided U.S. rights only. It did not automatically create protection in Europe, the United Kingdom, Canada, Japan, or other markets.

Parallel rights would have required separate national applications or regional filings. Any foreign counterparts would have had independent filing dates, prosecution histories, claim scope, and expiration dates. The U.S. expiration date cannot be used as a substitute for a foreign-family analysis.

For a global freedom-to-operate review, the relevant jurisdictions include:

United States;
European Patent Office member states;
United Kingdom;
Canada;
Japan;
Australia; and
major emerging pharmaceutical markets.

The U.S. patent's expiration does not establish that every foreign counterpart has expired, although patents from the same late-1970s priority period would generally also be historical rather than current rights.

What manufacturing and intellectual-property barriers remain?

Patent 4,364,923 does not create a current manufacturing barrier. Practical barriers remain in other areas:

reproducible control of inhaled particle-size distribution;
suspension homogeneity;
valve and actuator compatibility;
container-closure integrity;
dose uniformity over labeled life;
extractables and leachables;
HFA formulation stability;
device performance after storage;
scale-up of micronization or crystallization; and
FDA comparative-performance requirements.

These barriers may be difficult and expensive even when the core patent estate is expired. They are regulatory and manufacturing barriers rather than enforceable rights under Patent 4,364,923.

Key Takeaways

U.S. Patent 4,364,923 covers stabilized inhaled corticosteroid suspensions, especially crystalline-solvate beclomethasone dipropionate formulations.
Claims 1 and 11 are the two principal independent claims.
The most important limitations are crystalline-solvate form, suspension in propellant, resistance to crystal growth, and inhalable particle size.
Claims 4, 5, 8, and 10 are tied to CFC propellants, including CFC-11, CFC-12, and CFC-113.
The patent issued December 21, 1982, and expired December 21, 1999.
It has no current U.S. blocking effect and cannot support a current Paragraph IV stay or infringement suit.
Modern HFA beclomethasone products require analysis of later formulation, device, manufacturing, and method-of-use patents.
Biosimilar analysis is not relevant because beclomethasone dipropionate is a small-molecule drug.
The patent's remaining value is historical, technical, and prior-art related, not exclusionary.

Frequently Asked Questions

Can a company make a beclomethasone CFC aerosol under Patent 4,364,923 today?

Yes, from a patent perspective, the U.S. patent expired in 1999. Separate FDA and environmental restrictions on CFC inhalers remain distinct from patent rights.

Does Patent 4,364,923 cover QVAR RediHaler?

The expired patent does not create a current barrier to QVAR RediHaler. QVAR RediHaler is an HFA-based product with later regulatory and patent considerations.

Does the patent cover dry-powder beclomethasone inhalers?

No claim supplied covers a dry-powder inhaler. The claims require an aerosol propellant and a suspended steroid formulation.

Does claim 11 cover a beclomethasone solution formulation?

On its face, claim 11 requires beclomethasone dipropionate to be suspended in the propellant and present as a crystalline solvate. A true solution would not ordinarily satisfy those suspension and crystal-form limitations.

Can this patent be used to challenge a generic inhaled corticosteroid?

No. An expired patent cannot provide current exclusionary protection or create a Hatch-Waxman stay. Any challenge involving a current generic product would need to address later unexpired patents and applicable FDA exclusivity.

References

U.S. Patent and Trademark Office. (1982). U.S. Patent No. 4,364,923, Aerosol formulations.
United States Environmental Protection Agency. (n.d.). Protection of stratospheric ozone: Listing of substitutes and transition from CFC metered-dose inhalers.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: The Orange Book.
U.S. Food and Drug Administration. (2005). Removal of CFC-containing albuterol and other metered-dose inhalers from the U.S. market.
U.S. Food and Drug Administration. (n.d.). Patent certification and 30-month stays under the Hatch-Waxman Act.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	18421/72	Apr 20, 1972

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	196524	⤷ Start Trial
Austria	348115	⤷ Start Trial
Austria	352973	⤷ Start Trial
Austria	A302275	⤷ Start Trial
Austria	A352973	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,364,923

Summary for Patent: 4,364,923