US Patent 11,433,044: Claim Scope, Exclusivity, Litigation Risk, and Furosemide Patent Landscape

US Patent 11,433,044 protects a narrow combination of high-concentration subcutaneous furosemide, tris(hydroxymethyl)aminomethane, controlled pH, isosmoticity, and a specified molar ratio. The strongest commercial coverage is directed to a patch-pump administration system using furosemide concentrations of at least 15 mg/mL. The patent does not broadly cover all furosemide formulations, all injectable furosemide products, or all subcutaneous diuretic treatment.

What does US Patent 11,433,044 protect?

The patent claims methods of treating edema, hypertension, or heart failure by administering a liquid furosemide formulation subcutaneously. The formulation must satisfy several limitations simultaneously:

Required limitation	Independent claim 1	Independent claim 8
Therapeutically active agent	Furosemide as sole therapeutically active agent	Same
Route	Subcutaneous administration	Subcutaneous administration
Device	Not required	Patch device required
Furosemide concentration	About 5 mg/mL or greater	About 15 mg/mL or greater
Tris concentration	About 50-500 mM	About 50-500 mM
Osmolality	Isosmotic	Isosmotic
pH	About 7.0-8.5	About 7.2-8.0
Tris:furosemide molar ratio	Greater than about 1.5	Greater than or equal to about 1.5

Claims 2-7 narrow claim 1 by specifying the molar ratio, pH, concentration of tris, furosemide concentration, and pump-device administration. Claims 9-13 further narrow claim 1. Claims 14-20 create corresponding limitations under claim 8.

The patent therefore has two principal claim groups:

A broad subcutaneous formulation-and-treatment group under claim 1.
A more commercially targeted patch-device group under claim 8.

How broad are the independent claims?

Claim 1: formulation and treatment coverage

Claim 1 requires both a formulation and a therapeutic act. A potentially infringing product must be administered subcutaneously to a human with edema, hypertension, or heart-failure symptoms. The claim is not limited to congestive heart failure, although that indication is commercially central to subcutaneous furosemide products.

The formulation must contain:

Furosemide as the sole therapeutically active agent.
At least about 5 mg/mL furosemide.
Tris at 50-500 mM.
A pH of approximately 7-8.5.
Isosmotic characteristics.
A tris-to-furosemide molar ratio above approximately 1.5.

The "sole therapeutically active agent" limitation excludes a formulation in which another pharmacologically active drug is included. It does not necessarily exclude inactive excipients, buffers, tonicity agents, preservatives, or pH-adjusting substances.

Claim 8: high-concentration patch-pump coverage

Claim 8 is narrower in route and device but commercially more significant. It requires administration "using a patch device" and a furosemide concentration of at least about 15 mg/mL.

A conventional syringe, vial, intravenous bag, or non-patch infusion pump would not satisfy the express patch-device limitation of claim 8, although it could fall within claim 1 or claim 6 if the other limitations are met.

What do the dependent claims add?

Claims	Added limitation
2 and 14	Tris:furosemide molar ratio of at least 2
3 and 15	Tris concentration of about 50-250 mM
4	pH of about 7.2-8.0
5	Furosemide concentration of about 6-15 mg/mL
6	Subcutaneous administration using a pump
7	Pump is a patch device
9, 16	Tris concentration of about 50-150 mM
10, 17	Tris concentration of about 50-100 mM
11 and 18	Furosemide concentration of at least about 15 mg/mL
12 and 19	Furosemide concentration of at least about 20 mg/mL
13 and 20	Furosemide concentration of at least about 25 mg/mL

The dependent claims create layered fallback positions. A challenger may avoid one narrow claim while remaining exposed under a broader parent claim.

What formulation space does the molar-ratio limitation cover?

The molar ratio is central to the patent's formulation scope. Furosemide has a molecular weight of approximately 330.37 g/mol, while tris has a molecular weight of approximately 121.14 g/mol.

Approximate relationships are:

Furosemide concentration	Approximate furosemide molarity	Minimum tris concentration at 1.5:1 ratio
5 mg/mL	15.1 mM	22.7 mM
6 mg/mL	18.2 mM	27.3 mM
15 mg/mL	45.4 mM	68.1 mM
20 mg/mL	60.5 mM	90.7 mM
25 mg/mL	75.7 mM	113.6 mM

Because the claims require at least 50 mM tris, the ratio limitation becomes especially important at higher furosemide concentrations. For example:

A 5 mg/mL formulation with 50 mM tris has a ratio of approximately 3.3.
A 15 mg/mL formulation with 50 mM tris has a ratio of approximately 1.1 and would not satisfy the approximately 1.5 ratio requirement.
A 25 mg/mL formulation requires approximately 114 mM tris to meet a 1.5 ratio.

This interaction narrows the practical formulation window at 15-25 mg/mL furosemide. A product developer cannot assess infringement by concentration alone.

What formulations are protected by US 11,433,044?

The most defensible formulation reading covers an aqueous or liquid preparation containing furosemide and tris in a substantially neutral-to-mildly alkaline, isosmotic environment. The claims do not expressly require a particular furosemide salt, preservative, surfactant, container, reservoir material, or manufacturing process.

Potentially covered formulations include:

Furosemide at 15-25 mg/mL.
Tris at approximately 100-250 mM.
pH 7.2-8.0.
Isosmotic formulation characteristics.
Use in a subcutaneous patch pump.

Potentially outside the literal scope are formulations that:

Use less than approximately 5 mg/mL furosemide.
Use less than approximately 50 mM tris.
Have a tris:furosemide ratio at or below approximately 1.5, subject to construction of "about."
Fall outside the claimed pH range.
Are not isosmotic.
Use another active diuretic as a therapeutically active agent.
Are administered intravenously, orally, or intramuscularly.
Are administered subcutaneously without the claimed patch device, where only claim 8 is considered.

"About" introduces a potential claim-construction dispute. The permissible deviation depends on the specification, examples, prosecution history, measurement method, and technical meaning in the field. A formulation marginally outside a numerical boundary may still present infringement risk under the doctrine of equivalents.

Does the patent cover FUROSCIX?

The claims are directed to the product architecture associated with subcutaneous furosemide delivery for heart-failure patients, including a high-concentration formulation and a wearable or patch-based delivery device. FUROSCIX is a subcutaneous furosemide product approved by the FDA for at-home treatment of congestion due to fluid overload in adults with chronic heart failure [2].

The claims provided are technically aligned with a product that uses:

Furosemide as the active drug.
A concentrated liquid formulation.
Subcutaneous delivery.
A wearable delivery system.
Pump-based administration.

That alignment does not establish that every FUROSCIX presentation practices every claim. Claim coverage requires comparison against the approved formulation, actual concentration, pH, osmolality, tris concentration, molar ratio, and delivery-device configuration.

What is the FDA regulatory status?

The FDA approved FUROSCIX, a subcutaneous furosemide delivery product, through New Drug Application 214987 in October 2022 [2]. The product is intended for selected adults with chronic heart failure who require diuresis and are at risk of hospitalization or have inadequate response to oral loop diuretics.

The regulatory status matters because:

The approved indication can support method-of-use enforcement theories.
The approved formulation and device provide the commercial product against which claim practice is evaluated.
Any later generic or follow-on product would need to address the formulation, delivery route, device, and labeling limitations.
FDA approval does not itself establish patent validity or infringement.

What is the Orange Book status of US 11,433,044?

Orange Book listing must be evaluated against the patent's approved-product relationship, not the patent number alone. A method-of-use patent may be listed if it claims an approved use and satisfies FDA listing requirements. A formulation or delivery-system patent may also be listed if it claims the drug product or an approved method of use.

For a listed patent, an ANDA applicant may submit:

Paragraph I, if no patent information is listed.
Paragraph II, if the patent has expired.
Paragraph III, if the applicant will wait until expiration.
Paragraph IV, if the applicant asserts that the patent is invalid, unenforceable, or will not be infringed.
A section viii statement, where the applicant seeks approval for a use outside the patented method-of-use indication.

The claims supplied are method claims rather than conventional composition claims. That distinction can affect Orange Book listing, ANDA certification strategy, and the availability of a section viii carve-out. A product that uses the same formulation but is labeled only for a non-patented use may reduce method-of-use exposure, although promotional activity and actual use remain relevant [3].

When does US Patent 11,433,044 lose exclusivity?

The grant date does not determine the patent's expiration date. US utility patent term generally runs 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and applicable priority relationships [4].

The expiration date for US 11,433,044 cannot be calculated from the claims supplied. It requires the patent's front-page priority and filing data, terminal-disclaimer status, and any patent-term adjustment or extension recorded by the USPTO. Patent expiration should therefore be distinguished from:

FDA regulatory exclusivity.
Orphan-drug exclusivity, if applicable.
New chemical entity exclusivity.
Pediatric exclusivity.
Other patents in the same product estate.

A later-issued continuation can expire on the same date as an earlier family member if terminally disclaimed or subject to the same effective filing chain. A later grant date does not necessarily create a later expiration date.

What patent landscape surrounds subcutaneous furosemide?

The relevant estate is broader than US 11,433,044. A commercial subcutaneous furosemide product may implicate separate patent families covering:

Technology layer	Typical protection
Active formulation	Furosemide concentration, buffer, pH, osmolality, stability
Delivery route	Subcutaneous administration for edema or heart failure
Device	Wearable pump, patch, reservoir, cannula, delivery sequence
Treatment regimen	Dose, infusion duration, outpatient administration, conversion from oral therapy
Manufacturing	Preparation, filling, sterilization, container compatibility
Commercial use	Treatment of congestion, fluid overload, or diuretic resistance

US 11,433,044 is strongest at the intersection of formulation and administration. It is less useful against a product that uses a materially different buffer, a different concentration, a non-isosmotic formulation, or another delivery route.

The patent does not create a broad monopoly over furosemide. Furosemide is an old generic active ingredient, and conventional oral and intravenous furosemide products remain outside the claim scope unless they are used in the claimed subcutaneous manner with the claimed formulation parameters.

Which companies are challenging the patent estate?

The supplied record does not identify a Paragraph IV filer, ANDA applicant, district-court defendant, inter partes review petitioner, or settlement agreement directed specifically to US 11,433,044. No such event can be inferred from the claims.

The likely competitive threats are:

A generic or specialty-pharma applicant developing a non-patch subcutaneous formulation.
A device company pairing a different furosemide formulation with a wearable pump.
A formulation developer using a buffer other than tris.
An applicant using a different pH or tonicity profile.
A manufacturer pursuing a section viii carve-out for non-infringing indications.

A Paragraph IV challenge would likely focus on anticipation or obviousness based on known furosemide injections, buffer systems, subcutaneous infusion technologies, and wearable pump systems. The challenger would also examine whether the claimed combination produces an unexpected technical result, such as stability at high concentration, tolerability, reduced injection-site reactions, or improved delivery performance.

How strong is the patent estate?

Strengths

The claims combine multiple measurable formulation parameters.
The patch-device claims track a differentiated commercial delivery system.
The claims cover high-concentration furosemide, which is relevant to compact wearable devices.
The molar-ratio limitation may provide a formulation-specific distinction over ordinary furosemide injections.
Dependent claims create multiple concentration and buffer ranges.

Weaknesses

The claims are vulnerable to numerical claim-construction disputes.
Isosmoticity may depend on the measurement method and formulation conditions.
The "sole therapeutically active agent" limitation can create labeling and product-design opportunities.
Prior art may separately disclose furosemide injections, tris buffers, subcutaneous infusion, and wearable pumps.
Method claims require an administration act, creating enforcement complexity against manufacturers that sell components or formulations.
A competitor may design around the patch limitation while remaining outside claim 8.

The estate is commercially meaningful but technically narrow. Its strongest enforcement position is against a product that closely replicates the approved high-concentration tris-buffered subcutaneous formulation and patch-pump method.

What generic entry risks exist?

Scenario 1: Same formulation and same patch device

This presents the highest risk. An ANDA or 505(b)(2) applicant using the same concentration, pH, osmolality, tris range, and device would face direct claim exposure and likely a Paragraph IV dispute if the patent is listed.

Scenario 2: Same drug, different buffer

Replacing tris with another buffering system may avoid literal infringement, but equivalence risk would depend on whether the buffer performs substantially the same function in substantially the same way with substantially the same result.

Scenario 3: Same formulation, syringe or conventional pump

This may avoid claim 8 but could still implicate claim 1 or claim 6 if the product is administered subcutaneously and meets the formulation limitations.

Scenario 4: Lower concentration

A formulation below approximately 5 mg/mL may avoid claim 1, while a formulation below approximately 15 mg/mL may avoid the high-concentration limitations in claim 8 and claims 11-20. Commercial feasibility would depend on reservoir volume and treatment duration.

Scenario 5: Different indication or carved-out labeling

A non-heart-failure label may reduce method-of-use exposure. It would not automatically eliminate infringement if the product is promoted or routinely used for a claimed condition.

What patent litigation affects US 11,433,044?

The supplied information does not establish a filed infringement action, Paragraph IV case, inter partes review, post-grant review, or settlement involving this patent. Litigation analysis must distinguish US 11,433,044 from other patents in the same furosemide product family. A dispute involving a related patent does not automatically determine the validity, enforceability, or scope of this patent.

The main litigation issues would likely include:

Written description support for the claimed numerical ranges.
Enablement of the full 50-500 mM tris and 5 mg/mL-or-greater furosemide ranges.
Obviousness of combining concentrated furosemide, tris, isosmoticity, and subcutaneous delivery.
Construction of "about," "isosmotic," and "sole therapeutically active agent."
Whether a manufacturer induces the claimed patient administration.
Whether a generic label actively encourages the patented use.
Whether a patch device is structurally or functionally equivalent to the claimed device.

Key Takeaways

US 11,433,044 is a combination patent, not a basic furosemide patent.
The core invention claimed is subcutaneous treatment using concentrated furosemide with tris, controlled pH, isosmoticity, and a minimum tris:furosemide ratio.
Claim 8 is commercially important because it targets a patch-device method using at least approximately 15 mg/mL furosemide.
The claims do not broadly cover oral furosemide, conventional intravenous furosemide, or every subcutaneous furosemide formulation.
Concentration, buffer identity, pH, osmolality, and molar ratio must be analyzed together.
The patent's expiration date cannot be determined from the claims alone.
The supplied information does not establish a Paragraph IV challenge, litigation event, or settlement involving this patent.
Generic design-around opportunities include changing the buffer, concentration, route, device, pH, or therapeutic labeling.
The strongest infringement case would involve a product closely matching the FUROSCIX formulation and patch-pump delivery method.

FAQs

Does US Patent 11,433,044 cover intravenous furosemide?

No. The asserted claims require subcutaneous administration. An intravenous product would not satisfy that express route limitation, although other patents could apply.

Can a competitor avoid the patent by using sodium hydroxide instead of tris?

Potentially. The claims expressly require tris(hydroxymethyl)aminomethane. A formulation using a different buffering system may avoid literal infringement, subject to claim construction and potential doctrine-of-equivalents analysis.

Does a 15 mg/mL furosemide formulation automatically infringe?

No. It must also satisfy the tris concentration, molar-ratio, pH, isosmoticity, sole-active-agent, subcutaneous-use, and applicable device limitations.

Are furosemide biosimilars relevant to this patent?

No. Furosemide is a small-molecule drug, not a biologic. Competitive products would generally be generics, 505(b)(2) products, or specialty drug-device combinations rather than biosimilars.

Can a generic launch after FDA approval if the patent remains unexpired?

FDA approval and patent freedom to operate are separate questions. A company may obtain approval but delay launch, certify under Paragraph IV, carve out a patented use, settle with the patent holder, or launch subject to litigation risk.

References

United States Patent and Trademark Office. (2022). U.S. Patent No. 11,433,044.
U.S. Food and Drug Administration. (2022). FUROSCIX (furosemide injection), prescribing information and approval materials.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
United States Code. (2023). 35 U.S.C. §§ 154, 271, and 282.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Scpharmaceuticals	FUROSCIX	furosemide	SOLUTION;SUBCUTANEOUS	209988-001	Oct 7, 2022		RX	Yes	Yes	11,433,044	⤷ Start Trial				USE OF A LIQUID FORMULATION COMPRISING FUROSEMIDE TO TREAT CONGESTION DUE TO FLUID OVERLOAD (EDEMA) IN ADULTS WITH NYHA CLASS II/III CHRONIC HEART FAILURE	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2014248164	⤷ Start Trial
Brazil	112015025204	⤷ Start Trial
Canada	2908935	⤷ Start Trial
China	105431145	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,433,044

Which drugs does patent 11,433,044 protect, and when does it expire?

Summary for Patent: 11,433,044