United States Drug Patent 5,695,743: Claim Scope, Expiration, and Patent Landscape

U.S. Patent No. 5,695,743 covers chlorofluorocarbon-free pressurized inhalation aerosols using 1,1,1,2-tetrafluoroethane, commonly called HFA-134a or norflurane. Its claims reach formulations containing a therapeutically effective medicament, selected respiratory drugs, optional surfactants, and inhalation methods for delivering or treating a mammal. The patent issued on December 9, 1997, and its 17-year post-grant term would have expired on December 9, 2014, absent a term adjustment or other exceptional term event.[1]

The patent is therefore an expired formulation-platform patent. It does not currently block generic or branded inhaler development in the United States. Its historical importance lies in the transition from CFC-based metered-dose inhalers to HFA-134a products.

What does U.S. Patent 5,695,743 protect?

The patent protects a broad HFA-134a aerosol formulation and two related inhalation methods.

Claim	Subject matter	Principal limitation
1	Aerosol formulation	Medicament plus CFC-substantially-free propellant comprising HFA-134a; suitable for lung delivery
2	Narrow formulation genus	Claim 1 formulation containing one of eight specified medicaments
3	Surfactant formulation	Claim 1 formulation further comprising a surface-active agent
4	Delivery method	Administering a claim 1 aerosol to a mammalian lung
5	Treatment method	Administering a claim 1 aerosol to treat an inhalation-responsive condition

The claims are directed to a pressurized inhalation aerosol, generally corresponding to a metered-dose inhaler formulation. They do not expressly require a particular canister, metering valve, actuator, particle-size distribution, dose strength, suspension state, solution state, or manufacturing process.

How should claim 1 be construed?

Claim 1 has five material elements:

An aerosol formulation.
A therapeutically effective amount of a medicament.
A propellant substantially free of chlorofluorocarbons.
The propellant comprises 1,1,1,2-tetrafluoroethane.
The formulation is suitable for delivery to the lung by inhalation.

The word “comprising” makes the claim open-ended. A formulation can contain HFA-134a together with other propellants, excipients, cosolvents, stabilizers, or processing agents, provided the remaining limitations are met.

HFA-134a is a required claim element

A formulation using only HFA-227ea, HFA-152a, carbon dioxide, nitrogen, or another propellant would not literally satisfy claim 1 because the claim requires HFA-134a. A mixed-propellant formulation containing HFA-134a could fall within the claim even if HFA-134a is not the only propellant.

The claim does not specify a minimum concentration of HFA-134a. That omission potentially broadens the literal scope, although a court would still examine whether the formulation is genuinely a propellant system suitable for pulmonary delivery and whether the asserted composition satisfies the patent’s written-description and enablement requirements.

“Substantially free of chlorofluorocarbons”

This limitation targets the CFC phaseout that affected pressurized metered-dose inhalers. It excludes formulations that materially rely on CFC propellants. The term is quantitative in application but is not assigned a numerical threshold in the claim text supplied.

A formulation containing trace CFC contamination would present a different issue from a formulation intentionally using a CFC as a propellant. The practical design-around question is whether the product uses a non-CFC propellant system, not whether every molecule of CFC has been eliminated.

“Suitable for delivery to the lung”

This limitation narrows the claim to pulmonary inhalation products. Oral aerosols, nasal sprays, topical aerosols, and industrial aerosol systems fall outside the claim unless they are also suitable for lung delivery.

The claim does not require a particular disease, patient population, device brand, dose, or administration schedule.

Which drugs are covered by claim 2?

Claim 2 limits the medicament to the following compounds:

Listed medicament	Common commercial or therapeutic identity
Salbutamol	Albuterol, a short-acting beta-2 agonist
Beclomethasone dipropionate	Inhaled corticosteroid
Disodium cromoglycate	Cromolyn sodium
Pirbuterol	Short-acting bronchodilator
Isoprenaline	Isoproterenol
Adrenaline	Epinephrine
Rimiterol	Short-acting beta agonist
Ipratropium bromide	Anticholinergic bronchodilator

Claim 2 is narrower than claim 1 because it requires one of the listed medicaments. Claim 1 is not expressly limited to those eight drugs. A different inhaled drug could potentially fall within claim 1 if all other elements are met.

The claim language does not expressly distinguish salts, solvates, polymorphs, particle-size grades, or crystalline forms. The scope of a particular drug version would depend on the patent specification, prosecution history, and applicable claim-construction principles.

What formulations are protected by claim 3?

Claim 3 covers a claim 1 formulation that also contains a surface-active agent. Surfactants can improve suspension stability, reduce particle aggregation, modify wetting, or support dose uniformity in a metered-dose inhaler.

Examples of formulation categories that could have been relevant include:

HFA-134a suspensions containing micronized drug particles.
HFA-134a formulations with lecithin or related surfactants.
HFA-134a formulations containing a surfactant and one or more cosolvents.
Drug formulations using a surfactant to improve valve or canister performance.

Claim 3 does not identify a specific surfactant, concentration, drug, device, or particle-size range. Its dependency on claim 1 means the formulation must still contain HFA-134a, be substantially free of CFCs, and be suitable for pulmonary delivery.

A product using no surface-active agent could still be within claim 1. Claim 3 adds a narrower formulation category; it does not define the entire patent’s coverage.

What do claims 4 and 5 cover?

Claims 4 and 5 are method claims.

Claim 4 covers delivering a drug to the lung of a mammal by administering a claim 1 aerosol. It is primarily a drug-delivery method.

Claim 5 covers treating a mammal with an inhalation-responsive condition by administering a claim 1 aerosol to the lung. It adds a therapeutic-treatment context.

Both claims incorporate the limitations of claim 1. They therefore require an aerosol formulation containing HFA-134a and a therapeutically effective amount of medicament. They do not expressly incorporate claim 2’s eight-drug list or claim 3’s surfactant requirement.

The distinction between claims 4 and 5 is modest. Claim 4 focuses on delivery; claim 5 requires treatment of a condition. In an infringement dispute, the method claims would also raise issues concerning the identity of the actor, induced infringement, prescribing or dispensing conduct, and the relevant patient-use evidence.

When did U.S. Patent 5,695,743 lose exclusivity?

The patent issued on December 9, 1997.[1] For a U.S. utility patent subject to the pre-June 8, 1995 filing regime, the ordinary term was 17 years from grant rather than 20 years from the earliest effective nonprovisional filing date.[2]

Event	Date
Patent issued	December 9, 1997
Ordinary 17-year term endpoint	December 9, 2014
Current status	Expired
Current enforceability	No ordinary enforcement rights remain

The expiration analysis should be based on the patent’s official term record and any terminal disclaimer or exceptional term event. On the ordinary statutory calculation, the patent expired in December 2014. An expired patent cannot support a new U.S. infringement action for post-expiration commercial activity.

The patent’s expiration does not invalidate later patents covering a specific formulation, device, manufacturing method, container, valve, or combination product. It removes this patent as a current blocking right.

What is the Orange Book status of U.S. Patent 5,695,743?

U.S. Patent 5,695,743 should not be treated as a current Orange Book exclusivity barrier. Orange Book patent listings are tied to approved drug products and must meet FDA listing requirements under the Hatch-Waxman framework.[3]

The patent’s claims are platform-style claims covering HFA aerosol formulations and inhalation methods. They are not limited to a single approved product, dosage strength, label, or brand. Even if the patent was historically relevant to an inhaled product, its expiration removes any remaining patent-term barrier attributable to this patent.

For an ANDA applicant, current Orange Book review must focus on the patents actually listed against the relevant reference listed drug, including later formulation, device, method-of-use, or pediatric-use patents. Patent 5,695,743 itself does not create a live Paragraph IV issue after expiration.

Are Paragraph IV challenges still relevant?

No current Paragraph IV challenge can be directed to an expired patent as a basis for blocking approval. Paragraph IV certifications address listed patents that the applicant asserts are invalid, unenforceable, or not infringed. An expired patent does not provide a remaining period of patent protection against launch.

Historically, an ANDA applicant could have confronted this patent if it was listed against the relevant reference product while unexpired. The principal arguments would have included:

The proposed product does not contain HFA-134a.
The propellant is not “substantially free” of CFCs under the claim construction.
The formulation is not suitable for delivery to the lung.
The product lacks a therapeutically effective amount of medicament.
The asserted formulation does not contain a claimed surfactant for claim 3.
The method claims are not infringed by the applicant’s manufacturing or commercial conduct.
The claims are invalid for anticipation, obviousness, lack of enablement, written-description deficiencies, or indefiniteness.

Those arguments have commercial significance only as historical litigation analysis because the patent has expired.

How strong was the patent estate?

The patent was strong as a broad transition-platform patent but weak as a current commercial barrier because it has expired.

Factor	Assessment
Technical breadth	Broad at the level of HFA-134a pulmonary aerosols
Drug coverage	Broad under claim 1; narrower and enumerated under claim 2
Device coverage	Limited; no express valve, actuator, canister, or inhaler-device requirement
Manufacturing coverage	No dedicated manufacturing-process claim in the supplied claims
Formulation detail	Limited in the claims; no express concentration or particle-size requirement
Method coverage	Broad delivery and treatment claims tied to claim 1
Design-around potential	Meaningful through non-HFA-134a propellants, different dosage forms, or nonpulmonary delivery
Current blocking power	None after expiration

The principal vulnerability of the claim set is that many technical parameters are absent. Later patents could obtain narrower protection around suspension stability, solution formulations, cosolvents, particle engineering, valve performance, dose uniformity, and device integration.

What was the broader HFA inhaler patent landscape?

The patent landscape surrounding HFA-134a inhalers generally divided into six layers.

Propellant and formulation patents

These patents addressed replacement of CFC propellants with HFA-134a or HFA-227ea. They could cover:

Specific drug-propellant combinations.
HFA concentration ranges.
Ethanol or other cosolvents.
Surfactants and stabilizers.
Solution versus suspension formulations.
Chemical and physical stability.

Patent 5,695,743 occupies this broad formulation layer.

Drug-specific formulation patents

Later patents commonly narrowed the technology to a particular active ingredient, dose, particle-size distribution, or suspension system. These patents could remain commercially relevant after the expiration of a broad platform patent.

Inhaler-device patents

Separate rights could cover:

Metering valves.
Actuator geometries.
Dose counters.
Canister coatings.
Breath-actuated systems.
Spray plume and particle-size control.

Patent 5,695,743 does not, based on the supplied claims, claim those device features.

Manufacturing and filling patents

HFA products can require specialized filling, crimping, pressure control, suspension handling, and content-uniformity processes. These process patents may create practical manufacturing barriers even when the basic formulation patent has expired.

Method-of-use patents

A product can face later method-of-use patents directed to a disease, dose, patient subgroup, dosing schedule, or treatment combination. Those rights are separate from the general claim to an HFA aerosol.

Regulatory and product-specific rights

FDA approval, pediatric exclusivity, orphan-drug exclusivity, new chemical entity exclusivity, and product-specific Orange Book listings can affect generic entry independently of Patent 5,695,743.[3][4]

Which companies and products were commercially exposed?

The technology was relevant to manufacturers transitioning pressurized inhalers from CFCs to HFA propellants. Historical exposure could include companies marketing albuterol, beclomethasone, cromolyn, ipratropium, and other inhaled products in HFA metered-dose formats.

The patent cannot be used to assign revenue exposure to a particular brand without product-level evidence linking that brand’s formulation and market period to the patent. Current revenue exposure is zero from this patent because the patent is expired. Historical revenue exposure may have been material for companies commercializing HFA-134a inhalers before December 2014, particularly where no narrower formulation or device patent independently controlled the product.

What generic launch risks remain after expiration?

Patent 5,695,743 creates no current generic launch risk by itself. Remaining risks may arise from other rights or regulatory requirements:

Later-expiring formulation patents.
Device and metering-valve patents.
Method-of-use patents listed against the reference product.
Manufacturing-process patents.
ANDA product-specific bioequivalence or pharmaceutical-equivalence requirements.
FDA requirements for plume geometry, aerodynamic particle size, dose uniformity, and device performance.
Commercial supply constraints for HFA-compatible components.

For a generic HFA inhaler, the strongest practical barriers are likely to be product development, device equivalence, formulation stability, manufacturing validation, and later product-specific patents rather than Patent 5,695,743.

How does this patent compare with later inhaler patents?

Patent 5,695,743 is broad but technologically early. Its claims identify the propellant platform and pulmonary use without claiming detailed product architecture.

Later patents generally have narrower but more commercially targeted claims:

Patent category	Typical claim focus	Relationship to 5,695,743
HFA platform patent	HFA-134a plus inhaled drug	Broad foundation
Drug-specific formulation patent	Particular active ingredient and excipient system	Narrower, potentially later-expiring
Device patent	Valve, actuator, dose counter, or canister	Technically separate
Process patent	Filling, suspension preparation, or manufacturing step	May create manufacturing risk
Method-of-use patent	Disease, dose, or patient population	Separate therapeutic limitation
Combination-product patent	Drug plus device or delivery system	Product-specific protection

The expired patent should therefore be mapped as an historical foundational asset, not as the endpoint of freedom-to-operate analysis.

Key Takeaways

U.S. Patent 5,695,743 covers CFC-substantially-free pulmonary aerosols using HFA-134a.
Claim 1 is the principal broad formulation claim.
Claim 2 narrows the medicament to eight specified inhaled drugs.
Claim 3 adds a surface-active agent.
Claims 4 and 5 cover pulmonary delivery and treatment methods using the claim 1 formulation.
The patent issued December 9, 1997, and the ordinary 17-year term expired December 9, 2014.
The patent is not a current U.S. patent barrier to generic HFA inhaler development.
Later formulation, device, manufacturing, and method-of-use patents may still affect a specific product.
Paragraph IV analysis must focus on currently listed, unexpired patents for the relevant reference product.
The patent’s commercial significance is historical and platform-oriented rather than current and product-specific.

FAQs About U.S. Patent 5,695,743

Can an HFA-134a inhaler still infringe U.S. Patent 5,695,743?

No current infringement liability arises from ordinary post-expiration activity. During the patent term, an HFA-134a pulmonary aerosol containing a therapeutically effective medicament could have implicated claim 1.

Does the patent cover HFA-227ea inhalers?

Not by itself. Claim 1 requires HFA-134a. An HFA-227ea-only formulation would not literally satisfy that limitation.

Does the patent cover dry-powder inhalers?

No. The claims require an aerosol formulation containing a propellant comprising HFA-134a. A conventional dry-powder inhaler does not meet that formulation requirement.

Does claim 2 cover all beta agonists?

No. Claim 2 lists specific compounds. Salbutamol, pirbuterol, isoprenaline, adrenaline, and rimiterol are listed, but the claim does not cover every beta agonist by its terms. Claim 1 is broader because it is not expressly limited to the eight listed medicaments.

Is a surfactant required for infringement?

No. A surfactant is required only for claim 3. Claim 1 does not require a surface-active agent, and claims 4 and 5 depend on claim 1 rather than claim 3.

References

United States Patent and Trademark Office. (1997). U.S. Patent No. 5,695,743, Aerosol formulations.
United States Code. (2024). 35 U.S.C. §§ 154, 155, and 156: Patent term and patent term extension.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. (2024). Abbreviated new drug application regulations, 21 C.F.R. § 314.101 and § 314.127.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	4595689	⤷ Start Trial
Australia	631155	⤷ Start Trial
Canada	2004598	⤷ Start Trial
Canada	2303601	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,695,743

Summary for Patent: 5,695,743