United States Drug Patent 5,035,237: Claim Scope, Expiration, and Inhaler Patent Landscape

U.S. Patent No. 5,035,237 covered a patient-powered inhalation device using puncturable containers holding finely divided solid medicament. Its central architecture combined a pivoting lid and plunger with a sliding tray, carrier-mounted dose containers, and an inhalation air path. The patent issued July 30, 1991, and its 17-year patent term expired July 30, 2008, assuming no earlier terminal disclaimer or unusual adjustment. It is no longer an enforceable barrier to generic or follow-on inhaler development.

The patent is primarily a device patent, not a patent covering a particular active pharmaceutical ingredient. It would not ordinarily be listed in the FDA Orange Book for a drug product unless it qualified as a patent claiming the drug substance, formulation, or approved method of use. Its commercial relevance was tied to dry-powder inhaler architecture, particularly blister-based and multiple-dose carrier systems.

What does U.S. Patent 5,035,237 protect?

The patent protects a mechanical inhaler platform in which the patient’s inhalation draws powdered medicament through a punctured dose container. Claim 1 is the broadest independent claim and requires the following combination:

A device for administering finely divided solid medicament.
At least one puncturable medicament container mounted on a carrier.
A housing with a base and pivoting lid.
A plunger connected to the lid.
A tray sliding between:
- a substantially enclosed first position; and
- an extended second position that remains connected to the housing.
A support on the tray for the medicament carrier.
A mechanism that slides the tray into alignment with the plunger.
A mechanism that pivots the lid and punctures the container.
An air inlet and patient inhalation outlet.
An airflow path that entrains medicament released from the punctured container.

The claim is therefore a combination claim. A competing inhaler would not infringe claim 1 merely because it uses a puncturable blister or a piercing member. The accused device would need to practice the claimed housing, tray, lid, plunger, registration sequence, and inhalation path, either literally or under the doctrine of equivalents.

What is the inventive center of the patent?

The patent’s technical center is the coordinated interaction of three subsystems:

A sliding dose-selection tray.
A pivoting lid-mounted puncturing plunger.
A patient-generated airflow path through the punctured dose container.

The device allows the user to extend the tray, load or expose the carrier, return the tray to the housing, and then operate the lid to puncture the dose container. The claim language places importance on the mechanical sequence, not only on the use of blister packaging.

This structure differs from a simple capsule inhaler in which a capsule is placed manually into a chamber and pierced by separate needles. It also differs from a fully automatic blister inhaler in which a strip is advanced by a rotary wheel, ratchet, or motor rather than by the claimed sliding tray and pivoting lid.

How broad is claim 1 of U.S. Patent 5,035,237?

Claim 1 has relatively broad functional language but a narrow structural combination. Its breadth is limited by several mandatory elements.

Limitations that materially narrow claim 1

The device must have a tray that moves between two defined positions. The tray must be substantially surrounded by the housing in the first position and must remain in contact with the housing in the second position. A removable magazine or completely detachable cartridge would not necessarily satisfy this limitation.

The plunger must be connected to a pivoting lid. A fixed puncture needle, independently actuated piston, or rotary puncturing mechanism would be outside the literal language unless an equivalent analysis applied.

The container must be brought into registration with the plunger by sliding the tray. A system that advances the blister through a wheel, rotates the dose carrier without a sliding tray, or moves the plunger instead of the tray presents a stronger non-infringement position.

The claim also requires patient inhalation to generate the airflow that releases and entrains the medicament. A device using a propellant, powered fan, or external compressed-air source may not satisfy the claim’s patient-generated airflow limitation.

Claim construction risks

The terms “substantially surrounded,” “registration,” “air flow,” and “entrained” are functional and potentially fact-dependent. Their interpretation would depend on the specification, prosecution history, technical evidence, and the accused device’s operation.

The claim does not expressly require a specific dose number, blister material, medicament, particle-size range, or inhalation-resistance value. Those omissions give claim 1 broader coverage across different powders and container materials, but only when the required mechanical architecture is present.

What do claims 2 through 14 add?

Claim	Added limitation	Practical effect
2	Tray has a third position in which it is completely removed from the housing	Covers a removable-tray configuration in addition to the partially extended position
3	Rotatable support for a carrier with multiple circularly arranged containers	Targets a rotary multi-dose carrier
4	Indexing caused by moving the tray out and back	Covers dose advancement driven by tray reciprocation
5	Disc-shaped support with circular apertures for containers	Narrows claim 3 to an apertured disc
6	Plunger completely penetrates the container; ribs define an isolated airflow path	Adds a specific through-container airflow architecture
7	Support receives a carrier with a single container	Covers a single-dose configuration
8	Magazine receives at least one additional carrier	Adds storage for replacement single-dose carriers
9	Plunger located adjacent to the lid pivot axis	Narrows plunger placement
10	Plunger is curved to reduce the hole produced in the container	Covers a puncture geometry intended to limit foil or seal damage
11	Carrier is a blister pack	Expressly covers blister-based packaging
12	Two such devices form an integral device	Covers combined inhaler assemblies
13	The second device is back-to-back with the first	Narrows claim 12 to a tandem configuration
14	Plunger penetrates on lid opening and withdraws as the lid closes	Adds the puncture and withdrawal sequence

Claim 6 is one of the most technically specific claims. It requires more than a punctured container. The plunger must pass fully through the container, and ribs on the support must cooperate with housing structure to create a substantially isolated path from the plunger-side surface, through the container, and toward the outlet.

Claim 10 addresses puncture geometry. A curved plunger can reduce the size or configuration of the opening created in a blister or other container. This limitation may be difficult to apply to a straight needle system but could raise equivalence issues for curved, angled, or otherwise shaped piercing elements.

Claim 14 is a timing limitation. The lid-opening movement must cause penetration, while movement toward closure must cause withdrawal. An inhaler that punctures during a separate button actuation or during tray movement would have a stronger argument that it falls outside claim 14.

What formulations and dose containers are protected?

The patent does not claim a particular active ingredient or formulation. It covers the delivery device when used with “medicaments being in solid finely divided form.” The language can encompass dry powders containing:

Small-molecule bronchodilators.
Inhaled corticosteroids.
Anticholinergic agents.
Combination respiratory products.
Other powdered drugs suitable for patient-powered inhalation.

Claim 11 specifically identifies blister packs. Claims 3 through 6 address a multi-dose circular carrier, while claims 7 and 8 cover a single-container carrier and a magazine for additional carriers.

The patent does not expressly claim:

A particular blister foil laminate.
A specific powder excipient.
A defined aerodynamic particle-size distribution.
A specific dose mass.
A particular drug molecule.
A particular moisture-barrier coating.
A specific blister-forming process.

Those technologies could have been protected by separate formulation, packaging, manufacturing, or drug-product patents.

When did U.S. Patent 5,035,237 expire?

Event	Date or status
Patent issued	July 30, 1991
Governing term	17 years from issue for this pre-June 8, 1995 patent
Expected expiration	July 30, 2008
Current enforceability	Expired
FDA Orange Book status	Not ordinarily expected for a device-only patent
Current Paragraph IV exposure	None based solely on this expired patent

The applicable pre-1995 patent-term rule generally provided 17 years from grant. The American Inventors Protection Act changed the standard term for later applications to 20 years from the earliest effective nonprovisional filing date, subject to statutory adjustments. U.S. Patent 5,035,237 was issued under the earlier regime. [2]

A patent-term extension under 35 U.S.C. § 156 is generally associated with qualifying patents claiming a regulated product or method of using or manufacturing that product. A mechanical inhaler patent of this type would not ordinarily receive such an extension. [3]

What is the Orange Book status of U.S. Patent 5,035,237?

U.S. Patent 5,035,237 is not, by its claim language, a patent directed to a drug substance, drug formulation, or approved method of use. It is a mechanical delivery-device patent. The FDA Orange Book identifies patents submitted by new drug application holders that claim the approved drug product or an approved method of use. [4]

The practical consequences are:

The patent would not normally create an Orange Book patent listing for an inhaled drug.
A generic applicant would not ordinarily need to submit a Paragraph IV certification against this patent.
The patent would not independently block an abbreviated new drug application.
Any relevant device-performance or design risk would arise through product architecture, not Orange Book certification.

A product using the same active ingredient could still face separate patents covering the drug, formulation, particle engineering, dose strength, approved use, manufacturing process, or a different inhaler platform.

What generic entry risks existed?

During the patent term, the main risk applied to inhalers that copied the claimed mechanical arrangement. The highest-risk configuration would have included:

A circular blister disc.
A support with apertures receiving individual doses.
A tray that moved between extended and enclosed positions.
A lid-mounted plunger.
Indexing caused by tray movement.
A through-blister airflow path.
A curved or pivot-adjacent puncturing member.

Lower-risk designs would have used different architectures, such as:

A capsule rather than a blister.
A rotary dose wheel without a sliding tray.
A fixed mouthpiece and separate piercing actuator.
A strip-based system advanced by a ratchet.
A powered airflow source.
A device in which the dose container did not form part of the airflow path.

Because the patent expired in 2008, these distinctions now have historical rather than current infringement significance. They remain relevant to understanding how competing inhaler platforms avoided or differentiated around the patent.

Which companies and products occupied the relevant inhaler landscape?

The patent sits within the broader development of dry-powder inhalers and unit-dose or multi-dose blister delivery systems. Relevant commercial categories included:

Platform category	Representative commercial approach	Relationship to the patent
Circular blister carrier	Multiple doses arranged around a disc	Closest to claims 3 through 6
Blister strip inhaler	Linear strip advanced dose by dose	May avoid circular-support limitations
Capsule inhaler	Powder capsule pierced in a chamber	May avoid blister-pack and circular-carrier claims
Reservoir inhaler	Bulk powder metered from a reservoir	Generally outside puncturable-container claims
Turbine or passive multi-dose inhaler	Internal metering and patient airflow	Depends on whether the claimed tray and plunger are present
Dual inhaler assembly	Two inhalers integrated in one housing	Relevant to claims 12 and 13

Companies active in respiratory delivery included Fisons, Glaxo, Astra, Boehringer Ingelheim, 3M, Schering-Plough, Novartis, and later manufacturers of generic inhalers. Commercial products such as Diskhaler-type blister systems, capsule-based HandiHaler-type systems, and reservoir-based Turbuhaler-type systems used different combinations of dose packaging and airflow mechanics.

The existence of a similar commercial product does not establish infringement. A claim comparison must map each limitation to the product’s structure and operating sequence.

How strong was the patent estate?

The patent appears strongest as a focused mechanical patent and weaker as a platform-wide inhaler monopoly.

Strengths

Claim 1 combines the major housing, tray, lid, plunger, and airflow elements.
Claims 3 through 6 create a detailed position around circular multi-dose carriers.
Claim 11 expressly identifies blister packs.
Claim 14 captures the opening-and-closing puncture sequence.
The patent covers both multi-dose and single-dose embodiments through claims 3 and 7.

Weaknesses

The claims do not cover the active ingredient.
They do not claim formulation chemistry or powder engineering.
They depend heavily on a specific tray-and-lid mechanical sequence.
The claim language leaves substantial design-around space.
The patent expired more than 15 years ago.
Any historical value was concentrated in device configuration, not in continuing drug-product exclusivity.

The estate would have been more commercially meaningful if accompanied by unexpired continuation patents, formulation patents, manufacturing patents, or drug-specific method-of-use patents. U.S. Patent 5,035,237 alone does not establish that broader protection.

What patent litigation and settlement risk exists today?

No current infringement claim can be based on an expired patent for post-expiration conduct. Historical litigation could still have involved the patent before July 30, 2008, but the patent number and claim text alone do not establish a litigation or settlement history.

There is no current Paragraph IV settlement exposure attributable to this patent. A generic inhaler developer must instead assess:

Unexpired device patents.
Patents listed for the reference drug.
Formulation and particle-engineering patents.
Manufacturing-process patents.
Regulatory exclusivity.
Device sameness and human-factors requirements.
Trade dress and trademark issues.

Biosimilar risk is not applicable. The patent concerns a device for delivering solid medicament and does not claim a biologic. For an inhaled small-molecule product, the relevant FDA pathway is generally an ANDA or, depending on the product and regulatory posture, a 505(b)(2) application rather than a biosimilar application. [5]

What geographic coverage did the patent provide?

The patent provided protection only in the United States. Foreign equivalents, if filed and granted, would have required separate analysis in each jurisdiction. Patent rights are territorial, and the expiration of the U.S. patent did not itself determine the status of corresponding patents in Europe, Canada, Japan, Australia, or other markets.

A global freedom-to-operate review would therefore require a family-level assessment of:

Priority applications.
PCT filings.
National-phase patents.
Continuations and divisionals.
Patent-term adjustments or extensions.
Local lapse, renewal, and expiration records.

The U.S. patent’s expiration does not create a worldwide public-domain date.

Key Takeaways

U.S. Patent 5,035,237 covered a dry-powder inhaler using a puncturable container, sliding tray, pivoting lid, and lid-mounted plunger.
Claim 1 is broad in function but narrow in its required mechanical combination.
Claims 3 through 6 focus on circular multi-dose carriers and isolated airflow through the punctured container.
Claims 7 and 8 cover single-dose carriers and replacement-carrier magazines.
Claims 10 and 14 target puncture geometry and lid-operated puncture timing.
The patent issued July 30, 1991, and expired July 30, 2008.
It is not a current enforceable patent barrier.
It is not ordinarily an Orange Book drug patent because it claims an inhaler device rather than an active ingredient, formulation, or approved method of use.
No biosimilar issue arises from this patent.
Current generic-entry risk depends on later device, formulation, manufacturing, and drug-product patents.

FAQs

Does U.S. Patent 5,035,237 cover the drug inside the inhaler?

No. The claims cover the inhaler structure and operating sequence. They do not identify a specific active pharmaceutical ingredient or formulation.

Could a circular blister inhaler still be marketed in the United States?

Yes. This patent expired in 2008. A current product would need to avoid unexpired patents and satisfy FDA requirements, but U.S. Patent 5,035,237 alone does not prevent commercialization.

Is a puncturable blister enough to infringe this patent?

No. The accused product would also need to satisfy the claimed housing, sliding tray, pivoting lid, plunger, registration, and patient-generated airflow limitations.

Does the patent cover a capsule inhaler?

Not expressly. Claim 11 identifies a blister pack, while the broader claims require a puncturable container mounted on a carrier. A capsule product would require a separate element-by-element analysis and may not satisfy the claimed tray and lid structure.

Can a company rely on the patent’s expiration outside the United States?

No. The expiration of the U.S. patent does not establish the status of foreign counterparts. Each jurisdiction requires separate patent-family and legal-status analysis.

References

United States Patent and Trademark Office. (1991). U.S. Patent No. 5,035,237, Device for administering medicaments.
35 U.S.C. § 154(c). Patent term for applications filed before June 8, 1995.
35 U.S.C. § 156. Extension of patent term for regulatory review.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: The Orange Book.
U.S. Food and Drug Administration. (2018). Abbreviated new drug application submissions: User fees and review procedures.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	8519141	Jul 30, 1985
United Kingdom	8525067	Oct 10, 1985

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	396872	⤷ Start Trial
Austria	A204086	⤷ Start Trial
Australia	591152	⤷ Start Trial
Australia	6065586	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,035,237

Summary for Patent: 5,035,237