US Patent 5,945,449: Claim Scope, Expiration, Patent Landscape, and Generic Entry Risk

US Patent 5,945,449 covers calcium-free, bicarbonate-based electrolyte solutions and their use in renal replacement therapy, hemofiltration, cardiopulmonary bypass, acute renal failure, and oral fluid replacement. Its principal protection is a defined electrolyte profile containing sodium, magnesium, chloride, and bicarbonate without calcium.

The patent is no longer an active US exclusivity barrier. Its 20-year patent term ended in 2016, subject to any term adjustment or terminal-disclaimer history in the official file. The claims remain relevant as prior art and as a technical reference, but they do not create current US infringement exposure after expiration. Patent expiration does not eliminate FDA approval, manufacturing, sterility, labeling, or product-quality requirements.

What does US Patent 5,945,449 protect?

The patent has five principal claim groups:

Claim group	Claims	Protected subject matter
Dialysis and renal replacement use	1-5, 10-15	Administration of calcium-free bicarbonate solution for CRRT, peritoneal dialysis, hemofiltration, cardiopulmonary bypass, acute renal failure, and liver-transplant patients
Dysentery treatment	6	Calcium-free oral or therapeutic solution containing sodium, chloride, bicarbonate, and high-concentration glucose
Dialysis kit	7-8	An 80 mL calcium-free concentrate combined with sterile water, with an optional dextrose component and second concentrate
Dialysis-solution preparation	9	Dilution of the specified sterile concentrate into a dialysis solution with the claimed final electrolyte ranges
Infusate and oral electrolyte preparation	16-18	Dilution of the concentrate into a hemofiltration infusate or oral electrolyte solution

The core claimed final formulation is:

Component	Target concentration	Claimed range
Sodium	140 mmol/L	126-154 mmol/L
Magnesium	0.75 mmol/L	0.68-0.82 mmol/L
Chloride	106.5 mmol/L	96.5-117 mmol/L
Bicarbonate	35.0 mmol/L	31.5-38.5 mmol/L
Calcium	None	Calcium-free

The claims use “comprising,” which generally permits additional ingredients unless those ingredients defeat another express limitation. A product that contains the required electrolyte components could therefore fall within the claim even if it includes other non-excluded excipients. The calcium-free limitation remains central.

How broad are the independent claims?

Claims 1, 2, 4, 5, 6, 7, 9, 14, 16, and 18 are the principal independent claims.

Claims 1, 2, 4, and 5: treatment-use claims

Claims 1 and 2 cover administering the claimed solution for:

Continuous renal replacement therapy.
Peritoneal dialysis.

Claim 4 covers reducing potassium and fluid volume during cardiopulmonary bypass. Claim 5 covers administration as a hemofiltration infusate.

These claims require more than merely selling or possessing the solution. The asserted conduct must include administration to a patient for the specified use. The claims also require:

A sterile solution or infusate.
No calcium.
The specified sodium, magnesium, chloride, and bicarbonate concentrations.
The relevant clinical procedure.

A manufacturer that sells a calcium-free bicarbonate solution without labeling it for the claimed procedure would present a different infringement analysis from a manufacturer that markets it expressly for CRRT, peritoneal dialysis, or hemofiltration. Because the patent has expired, this distinction has no current US damages consequence under the patent.

Claims 9, 10, 11, 12, 13, and 14: preparation and downstream-use claims

Claim 9 is directed to preparing the final solution by diluting a defined sterile concentrate. Claims 10-13 then apply that preparation method to specific clinical uses.

Claim 14 is important because it does not depend on claim 9. It directly covers administration of the calcium-free dialysis solution for treating acute renal failure without introducing calcium into blood removed during dialysis.

The independent route in claim 14 reduces reliance on the precise concentrate-preparation steps in claim 9. A competing product could potentially avoid claim 9 by using a different preparation process, but the same product could still have been captured by claim 14 if the final composition and clinical use satisfied the claim. That distinction would have mattered during the patent term.

Claim 6: dysentery formulation

Claim 6 is a separate composition and treatment concept. It requires:

Component	Required concentration
Sodium	90 mmol/L
Chloride	68.5 mmol/L
Bicarbonate	22 mmol/L
Glucose	277 mmol/L

This claim is materially different from claims 1-5 and 9-18. It does not use the 140 mmol/L sodium, 0.75 mmol/L magnesium, 106.5 mmol/L chloride, and 35 mmol/L bicarbonate profile. It also does not recite magnesium.

The 277 mmol/L glucose level is approximately 5% w/v glucose. The claim therefore targets an oral or therapeutic electrolyte formulation for dysentery rather than a conventional renal replacement solution.

Claims 7 and 8: kit protection

Claim 7 covers a kit containing:

One 80 mL unit of calcium-free concentrate.
One liter of sterile water.

The concentrate contains:

Ingredient	Concentration in concentrate
Sodium chloride	86.87 g/L
Magnesium chloride	2.05 g/L
Sodium bicarbonate	39.69 g/L

Claim 8 adds:

One liter of 5% w/v dextrose solution in water.
A second 80 mL concentrate unit.

The kit claims are narrower than the broad administration claims because they require specific package contents, unit volumes, and concentrate composition. A ready-to-use bag could avoid the kit claims during the patent term while still implicating a treatment-use claim if the final solution and labeled use matched the relevant claim.

What formulations are protected by US 5,945,449?

The patent protects two principal formulation families.

Calcium-free bicarbonate renal replacement formulation

The renal formulation contains bicarbonate as the principal buffer and excludes calcium. The claimed final concentrations are broad enough to cover ordinary manufacturing variation, but the combined limitations remain specific.

The formulation is directed to applications in which calcium is intentionally withheld from the dialysis fluid or infusate. This can be relevant to anticoagulation protocols, especially regional citrate anticoagulation, where calcium management occurs separately from the dialysis fluid.

The claims do not expressly require citrate anticoagulation. A product can fall within the compositional claims without containing citrate if the other limitations are satisfied.

Glucose-containing formulation

Claim 3 adds 2.5% w/v dextrose to the peritoneal dialysis solution of claim 2. Claim 8 adds a 5% w/v dextrose solution as a kit component.

These are different claim structures:

Claim 3 requires the dextrose in the administered dialysis solution.
Claim 8 requires a separate 5% dextrose component in the kit.
Claim 6 requires approximately 5% glucose in a distinct dysentery formulation.

The presence of glucose or dextrose alone is not enough. The product must also satisfy the relevant electrolyte, calcium-free, administration, or kit limitations.

How should the numerical ranges be analyzed?

The ranges are expressed as nominal values with ±10% tolerances:

Component	Nominal	Approximate tolerance
Sodium	140 mmol/L	±14 mmol/L
Magnesium	0.75 mmol/L	±0.07 mmol/L
Chloride	106.5 mmol/L	±10 mmol/L
Bicarbonate	35 mmol/L	±3.5 mmol/L

The claim language raises several technical and legal issues:

Final concentration versus concentrate concentration

Claims 1-6 and 14 focus on the final administered solution. Claims 7, 9, and 16 focus on the concentrate and the dilution process.

A concentrate can have a materially different composition from the final solution. In a claim analysis, the relevant question is whether the final diluted product satisfies the final-concentration limitations, whether the concentrate satisfies the stated concentrate limitations, or both.

Magnesium chloride form

The claims identify magnesium chloride by weight in the concentrate but identify magnesium by millimoles per liter in the final solution. The hydrate state of magnesium chloride can affect the weight-to-mole conversion. Commercial products should therefore be evaluated against the actual raw-material specification and the final analytical assay.

“Calcium-free”

The claims do not provide a numerical calcium threshold in the text supplied. The term would likely be interpreted in light of the specification, prosecution history, manufacturing conditions, and ordinary technical meaning at the relevant filing date.

A product containing intentional calcium addition would present a direct conflict with the limitation. Trace calcium from water, excipients, containers, or process equipment would require a more detailed construction and evidence analysis.

Sterility

Sterility is an express limitation in the solution, concentrate, kit, and preparation claims. A nonsterile laboratory formulation would not satisfy the sterile-product limitation, although a sterile product made from a nonsterile intermediate could raise separate issues depending on the claim and manufacturing process.

When did US Patent 5,945,449 lose exclusivity?

US Patent 5,945,449 expired in 2016 after the standard 20-year patent term applicable to its filing regime. The patent therefore does not currently block:

Manufacture of the claimed solution.
Sale of the claimed solution.
Administration for CRRT or peritoneal dialysis.
Use of the claimed concentrate.
Preparation of the claimed infusate.
Marketing of a product with the claimed electrolyte profile.

The expiration analysis is separate from FDA exclusivity. Patent expiration does not determine whether a product may be marketed in the United States. A sponsor still must satisfy the applicable FDA pathway, including drug approval, manufacturing controls, labeling, sterility, stability, and container-closure requirements.

What is the Orange Book status of US 5,945,449?

The Orange Book lists patents associated with approved drug products when the relevant patent satisfies FDA listing requirements and is submitted by the NDA holder. A patent’s presence in, or absence from, the Orange Book does not determine its validity or enforceability in every context.

Because US 5,945,449 expired in 2016, it is not a current Orange Book exclusivity barrier. Any historical Orange Book listing would no longer prevent approval of an ANDA based on that patent. Current regulatory analysis should focus on the patents listed against the specific reference product, if any, rather than the expired patent number alone (FDA, 2025a).

Are Paragraph IV challenges relevant?

A Paragraph IV certification would have been relevant while the patent was listed against an approved reference product and remained unexpired. A generic applicant could have certified that the patent was invalid, unenforceable, or not infringed.

Today, US 5,945,449 does not present a meaningful Paragraph IV barrier because the patent term has ended. A generic applicant does not need to litigate an expired patent to obtain approval on the basis that the patent no longer confers enforceable exclusivity. The relevant filing strategy would instead address:

Any unexpired formulation patents.
Method-of-use patents.
Process or device patents.
FDA exclusivity.
Product-specific labeling restrictions.
Sterility and manufacturing requirements.

What patent litigation affects US 5,945,449?

The supplied claim set does not establish a current litigation matter. The patent’s expiration eliminates the principal commercial consequence of new infringement litigation under these claims.

Any historical dispute would require review of:

PACER litigation records.
USPTO Patent Center prosecution and maintenance records.
Assignment and merger records.
FDA Orange Book historical listings.
Products and labels accused during the patent term.

No current patent injunction, royalty obligation, or Paragraph IV stay follows from the claim text alone. Patent expiration also does not resolve contractual obligations arising from an earlier license or settlement agreement.

Which companies compete in the relevant product markets?

The relevant competition is divided by clinical use rather than by one uniform product category.

Market	Representative product types	Key commercial issue
CRRT	Bicarbonate-based replacement and dialysate fluids	Calcium content, bicarbonate stability, bag configuration, anticoagulation protocol
Peritoneal dialysis	Glucose-containing peritoneal dialysis solutions	Glucose strength, calcium and magnesium content, buffer system, osmolarity
Hemofiltration	Sterile replacement infusates	Sterility, electrolyte control, compatibility with CRRT equipment
Cardiopulmonary bypass	Hemoconcentration or fluid-management solutions	Clinical protocol, potassium removal, operating-room use
Oral rehydration	Glucose-electrolyte solutions	Sodium-glucose transport profile, glucose level, regulatory classification

Major commercial participants in renal replacement fluids have included Baxter, Fresenius Medical Care, B. Braun, and other regional sterile-infusion suppliers. The relevant competitive products may not practice the expired claims because they can use different calcium levels, buffers, packaging systems, or electrolyte concentrations.

Biosimilar analysis is not relevant. The claimed products are sterile electrolyte solutions, not biologics. The principal regulatory competitors are generic, follow-on, 505(b)(2), or independently approved sterile products, depending on the product and reference standard.

How strong was the patent estate?

The patent had meaningful claim breadth during its term because it combined composition, use, preparation, kit, and patient-population claims. Its strongest features were:

Multiple independent claim categories.
Coverage of both final solutions and concentrates.
Coverage of CRRT, peritoneal dialysis, hemofiltration, and acute renal failure.
A direct treatment claim in claim 14 that did not depend on the concentrate-preparation claim.
Kit claims that could have applied to a specific commercial package.

Its limitations were also substantial:

The electrolyte profile is narrowly defined.
The calcium-free limitation may be avoided by calcium-containing products.
Sterility is required.
Several claims require a specific treatment or patient population.
Claims 7 and 8 require particular package volumes and components.
Claim 6 is technically separate from the renal replacement claims.
The patent is expired.

The estate is therefore commercially inactive as an exclusion right but remains technically relevant for freedom-to-operate searches and historical prior-art analysis.

What manufacturing and IP barriers remain after expiration?

The expired patent does not remove the practical barriers to commercial entry. A competing sponsor would still need to address:

Sterile manufacturing under current good manufacturing practice.
Bicarbonate stability and precipitation control.
Container-closure integrity.
Terminal sterilization or validated aseptic processing.
Compatibility with CRRT and dialysis equipment.
Shelf-life and in-use stability.
Correct electrolyte assay and release testing.
FDA approval or clearance under the applicable product pathway.
Separate patent rights covering bags, connectors, pumps, anticoagulation systems, or manufacturing processes.
Trade-secret restrictions involving formulation scale-up and packaging.

Manufacturing know-how can remain commercially valuable after patent expiration, but it cannot extend the patent term. A later patent covering a distinct process, container, device, or formulation improvement would need independent analysis.

What generic launch scenarios exist?

Ready-to-use CRRT solution

A sponsor could launch a ready-to-use solution with the same or similar electrolyte profile after resolving FDA approval and any later patents. The expired patent would not block the formulation.

Two-component concentrate system

A sponsor could market a concentrate-and-diluent kit. The historical claim 7 and claim 8 package limitations would no longer create patent risk, but the sponsor would need to validate mixing instructions, sterility, stability, and final concentration.

Calcium-containing alternative

A calcium-containing product would likely avoid the calcium-free limitations, although other patents or clinical requirements could apply.

Different buffer system

A lactate-buffered or otherwise modified product could avoid the bicarbonate-specific limitations. The product would remain subject to its own regulatory and technical requirements.

Oral rehydration product

The dysentery claim is expired and narrow. A modern oral electrolyte product would be assessed against current regulatory requirements and any later formulation patents, not against US 5,945,449.

Key Takeaways

US Patent 5,945,449 covers calcium-free bicarbonate solutions, specified electrolyte ranges, concentrate kits, dilution methods, and clinical uses.
The main protected renal formulation contains sodium at 140 mmol/L, magnesium at 0.75 mmol/L, chloride at 106.5 mmol/L, and bicarbonate at 35 mmol/L.
Claims cover CRRT, peritoneal dialysis, hemofiltration, cardiopulmonary bypass, acute renal failure, liver-transplant patients, and oral fluid replacement.
Claims 7-9 and 16 protect concentrate-based preparation and kit configurations.
Claim 6 is a separate glucose-based dysentery formulation.
The patent expired in 2016 and is not a current US exclusivity or Paragraph IV barrier.
Biosimilar analysis is not applicable because the products are sterile electrolyte solutions rather than biologics.
Current market entry risk is more likely to arise from later formulation, device, packaging, process, or FDA-related requirements than from US 5,945,449.

FAQs

Does US Patent 5,945,449 cover calcium-containing CRRT solutions?

No. The claims expressly require a calcium-free solution or infusate. A calcium-containing product would generally avoid that limitation, subject to claim construction and other patent rights.

Does the patent cover PRISMASOL or PHOXILLUM specifically?

The patent claims do not identify those products by name. Product coverage would depend on the actual formulation, labeling, administration method, and patent term. Because US 5,945,449 expired, it no longer creates current infringement exposure.

Can a company sell a generic version of the claimed bicarbonate dialysis solution?

The expired patent does not prevent sale. The company must still obtain the required FDA authorization and comply with sterile manufacturing, stability, labeling, and quality requirements.

Is claim 13 limited to regional citrate anticoagulation?

No. Claim 13 requires treatment of acute renal failure without introducing calcium into blood removed during dialysis. It does not expressly require citrate, although the clinical context may be compatible with calcium-management protocols.

Does the patent cover the concentrate alone?

Claim 7 covers a specific kit containing the concentrate and sterile water. Claims 9 and 16 cover dilution methods. The claim set supplied does not present a broad standalone composition claim directed only to the concentrate independent of the kit or preparation method.

References

U.S. Patent No. 5,945,449. (1999). United States Patent and Trademark Office. https://patents.google.com/patent/US5945449
U.S. Patent and Trademark Office. (2025). Patent term adjustment and patent term information. https://www.uspto.gov/patents/laws/patent-term-adjustment
U.S. Food and Drug Administration. (2025a). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book
U.S. Food and Drug Administration. (2025b). Drugs@FDA. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Code, Title 35, § 154. (2025). Contents and term of patent; provisional rights. https://uscode.house.gov/crew/35_USC_154.html

Details for Patent: 5,945,449

Summary for Patent: 5,945,449