List of Excipients in Branded Drug SELENIOUS ACID

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
American Regent Inc	SELENIOUS ACID	selenious acid	0517-6560	NITRIC ACID
American Regent Inc	SELENIOUS ACID	selenious acid	0517-6560	WATER

Generic Drugs Containing SELENIOUS ACID

Company	Ingredient	NDC	Excipient
Camber Pharmaceuticals Inc	selenious acid	31722-492	NITRIC ACID
Camber Pharmaceuticals Inc	selenious acid	31722-492	WATER
Gland Pharma Limited	selenious acid	68083-660	NITRIC ACID
Gland Pharma Limited	selenious acid	68083-660	WATER

What are the Most Frequently-Used Excipients in SELENIOUS ACID?

# Of NDCs	Excipient
2	NITRIC ACID
2	WATER

Selenious Acid Excipient Strategy and Commercial Opportunities

Last updated: September 13, 2026

Selenious acid is used primarily as a source of elemental selenium in injectable products for parenteral nutrition. Its commercial value is limited by the low dose, long-established chemistry, and lack of meaningful composition-of-matter exclusivity. The strongest opportunities are formulation execution, ready-to-use parenteral nutrition products, pediatric dosing, supply reliability, and compatibility management rather than new-molecule patent protection.

What is selenious acid used for in pharmaceutical products?

Selenious acid, also called selenium dioxide hydrate, has the formula H2SeO3 and CAS Registry Number 7783-00-8. Pharmaceutical products generally use it as the selenium source in sterile injectable solutions rather than as a conventional therapeutic active ingredient.

The relevant clinical use is selenium supplementation for patients receiving parenteral nutrition, particularly patients who cannot obtain adequate selenium through enteral feeding. Selenium is incorporated into selenoproteins involved in antioxidant defense, thyroid hormone metabolism, and redox regulation. [1,2]

Attribute	Pharmaceutical relevance
Chemical	Selenious acid
Formula	H2SeO3
CAS number	7783-00-8
Therapeutic role	Trace-element supplementation
Typical route	Intravenous administration after dilution or admixture
Primary setting	Total parenteral nutrition and parenteral nutrition admixtures
Principal dosage form	Sterile aqueous injection
Key quality risks	Trace-metal contamination, oxidation-reduction chemistry, pH, particulate matter, container compatibility
Biosimilar exposure	None
Conventional generic exposure	High

The product is not generally positioned as a standalone chronic oral drug. Commercial products are designed for hospital pharmacy use, compounding into parenteral nutrition solutions, or controlled administration under clinical supervision.

What excipients are used with selenious acid injection?

The simplest and most commercially defensible formulation uses water for injection with sodium hydroxide and hydrochloric acid for pH adjustment. A representative selenium injection label identifies selenium supplied as selenious acid and lists water for injection with pH-adjusting agents among the inactive ingredients. [3]

Core excipient platform

Excipient or component	Function	Commercial and regulatory considerations
Water for injection	Vehicle	Must meet injectable-water and sterility requirements
Sodium hydroxide	pH adjustment	Controls solubility and chemical stability
Hydrochloric acid	pH adjustment	Used to establish the target pH range
Nitrogen headspace, where used	Oxygen reduction	May reduce oxidative stress during storage
Container closure system	Product protection	Must control extractables, leachables, adsorption, and oxygen ingress

The formulation should remain as simple as possible. Adding buffers, antioxidants, chelators, surfactants, or tonicity agents can create new compatibility and regulatory burdens without improving the clinical value of a low-dose trace-element injection.

Why excipient selection is unusually important

Selenium is administered at microgram-per-milliliter concentrations. Small changes in concentration, adsorption, precipitation, or assay recovery can materially affect delivered dose. The formulation must be evaluated in the final container and after dilution into clinically used parenteral nutrition solutions.

Key development tests include:

• Assay and related substances over shelf life
• Elemental impurity profile
• Visible and subvisible particulate matter
• pH drift
• Container closure integrity
• Adsorption to glass, elastomer, and plastic surfaces
• Compatibility with amino acids, dextrose, lipids, electrolytes, vitamins, and other trace elements
• Stability after admixture into parenteral nutrition bags
• In-use stability during pharmacy preparation and administration
• Sterility and bacterial endotoxin control

The primary excipient strategy is therefore a compatibility strategy. The commercial advantage comes from demonstrating robust performance in real parenteral nutrition workflows.

What formulations are protected by selenious acid patents?

Selenious acid has no meaningful new-chemical-entity patent opportunity. The molecule and its use as a selenium source are long established. Patent value, where available, would have to come from a specific formulation, container, manufacturing process, admixture system, dosing protocol, or delivery device.

Patent opportunity by claim type

Claim category	Likely strength	Commercial assessment
Selenious acid composition of matter	None	Public-domain chemistry
Basic sterile aqueous injection	Low	Easy design-around and established practice
Specific pH and concentration range	Low to moderate	May support regulatory differentiation but narrow protection
Stable admixture with parenteral nutrition	Moderate	Potential value if supported by strong stability data
Ready-to-use premixed nutrition product	Moderate	Product and process claims may be relevant
Container or closure system	Moderate	Useful where adsorption or oxygen ingress is demonstrated
Pediatric low-volume presentation	Low to moderate	Commercial differentiation more likely than patent strength
Manufacturing process	Low to moderate	Protection depends on non-obvious process controls
Method of treating selenium deficiency	Low	Broad therapeutic concepts are old
New delivery device	Moderate	Relevant only if the product uses a distinct device

An applicant seeking patent protection would need data showing an unexpected technical effect, such as improved stability in a difficult parenteral nutrition matrix, reduced selenium loss from adsorption, improved particulate control, or a longer in-use period.

A narrow pH range alone is unlikely to create a strong commercial barrier unless the range produces a demonstrated improvement over known formulations. The same limitation applies to routine use of water for injection, hydrochloric acid, sodium hydroxide, or standard vial systems.

What is the FDA regulatory status of selenious acid products?

Selenious acid injection is regulated as a prescription sterile drug product. The product is used under the FDA framework applicable to injectable drug products and parenteral nutrition components. FDA labeling emphasizes dilution, controlled administration, and the risk of toxicity from excessive selenium exposure. [3]

FDA-relevant development requirements include:

1. Drug Master File or qualified source information for the selenious acid material.
2. Control of elemental impurities and selenium assay.
3. Sterile manufacturing and aseptic-process validation.
4. Container closure integrity testing.
5. Stability data in the commercial container.
6. Compatibility data with parenteral nutrition admixtures.
7. Clear instructions for dilution, preparation, and administration.
8. Risk controls for dosing errors involving microgram quantities.

The product is distinct from an oral dietary supplement. Injectable selenium products must meet pharmaceutical standards for sterility, particulate matter, endotoxins, assay, and container performance.

What is the Orange Book status of selenious acid?

The Orange Book is the controlling FDA reference for approved drug products, therapeutic equivalence evaluations, and listed patent or exclusivity information. [4]

Selenious acid injection does not present the typical Orange Book patent profile associated with a branded small-molecule drug. The relevant commercial conclusion is:

• No new chemical entity exclusivity remains available for selenious acid.
• Biosimilar exclusivity does not apply.
• A conventional selenium injection is exposed to generic competition.
• Any patent value would be product-specific and dependent on an approved formulation, device, manufacturing process, or method of use.
• Patent listings must be checked against the exact NDA, strength, dosage form, and sponsor because selenium products can be marketed under different regulatory histories.

A generic applicant could pursue an abbreviated pathway if the reference product, dosage form, strength, route, and regulatory status support that pathway. Where an exact reference product is unavailable or formulation differences are material, a 505(b)(2) strategy may be more practical.

When does selenious acid lose exclusivity?

Selenious acid has effectively lost molecule-level exclusivity because the active substance and basic clinical use are established. The commercial exclusivity timeline is therefore driven by product approval, not by a remaining active-ingredient patent.

Exclusivity category	Status
New chemical entity exclusivity	Not available for established selenious acid products
Orphan-drug exclusivity	Not inherent to the substance
Pediatric exclusivity	Possible only if separately awarded for a qualifying product
Market exclusivity from approval	Product-specific
Composition-of-matter patent	Not commercially relevant
Formulation patent	Possible but likely narrow
Biosimilar exclusivity	Not applicable
Generic entry	Potentially immediate after approval absent blocking rights

The exact launch date for a generic depends on FDA approval, the reference product’s regulatory pathway, any listed patent, Paragraph IV litigation, and the applicant’s manufacturing readiness.

Which companies are challenging selenious acid products?

The market is more likely to experience ordinary generic and supply competition than high-profile Paragraph IV litigation. A Paragraph IV challenge would require an approved reference product with a relevant Orange Book patent listing. For a conventional selenious acid injection, the most likely patent position is no listed patent or only a narrow product-specific listing.

Potential challengers would include:

• Injectable generic manufacturers
• Parenteral nutrition suppliers
• Contract manufacturers with sterile fill-finish capacity
• Hospital-focused pharmaceutical companies
• Suppliers seeking to convert bulk selenium materials into finished dosage forms

The principal barrier is not patent litigation. It is reliable sterile manufacturing at low concentration, validated assay control, container compatibility, and hospital procurement access.

What generic entry risks exist for selenious acid?

Generic entry risk is high for a basic sterile aqueous product. The following factors make substitution commercially feasible:

• Established active ingredient
• Simple formulation
• Low clinical complexity
• No biosimilar development requirement
• Standard intravenous administration
• Limited need for novel delivery technology
• Hospital purchasing based heavily on availability and price

The strongest differentiation opportunities are operational:

• Shortage-resistant supply
• Multiple vial sizes
• Lower minimum order quantities
• Simplified pharmacy preparation
• Longer shelf life
• Lower overfill
• Improved labeling and barcode controls
• Demonstrated stability in common parenteral nutrition systems
• Domestic or regional sterile manufacturing

A generic sponsor that matches the reference product but cannot demonstrate reliable supply may have limited commercial impact. Hospitals and compounding pharmacies place a high value on continuity for trace-element products because shortages can disrupt nutrition protocols.

What commercial opportunities exist for selenious acid excipient strategy?

Ready-to-use parenteral nutrition

A premixed or pharmacy-ready selenium presentation could reduce preparation steps and dosing errors. The product would need strong compatibility data, clear administration instructions, and packaging that supports hospital workflows.

Pediatric and neonatal presentations

Neonatal and pediatric parenteral nutrition requires very small selenium doses. Commercial opportunities include:

• Low-volume, high-accuracy presentations
• Unit-dose packaging
• Graduated delivery systems
• Reduced overfill
• Low-surface-area containers
• Labels designed for microgram dosing

The regulatory burden is higher because dose accuracy and excipient exposure are more sensitive in small patients.

Hospital shortage mitigation

A second-source product can compete on supply reliability. Opportunities include domestic fill-finish, dual-source raw materials, and inventory programs for hospital systems and group purchasing organizations.

Compatibility data as a commercial asset

Compatibility data can differentiate an otherwise interchangeable product. A sponsor can support adoption by publishing validated stability information for combinations with:

• Dextrose and amino acid solutions
• Lipid emulsions
• Multivitamin products
• Zinc, copper, chromium, and other trace elements
• Common parenteral nutrition bag materials
• Extended administration periods

The data may not create broad patent protection, but it can reduce pharmacy conversion barriers.

Contract manufacturing and licensing

Licensing opportunities are more likely to involve manufacturing and market access than molecule ownership. Attractive partners may have:

• FDA-inspected sterile facilities
• Established parenteral nutrition distribution
• Hospital contracting relationships
• Existing trace-element product portfolios
• Regional regulatory approvals
• Experience with low-dose elemental assays

A deal based solely on access to selenious acid chemistry would have limited value. A deal including validated sterile manufacturing, supply continuity, and regulatory files would be more commercially defensible.

How strong is the patent estate for selenious acid?

The patent estate is weak at the active-ingredient level and potentially moderate for a narrowly defined finished product.

Estate component	Strength	Reason
Active ingredient	Very weak	Old, known chemical
Basic injection	Weak	Routine formulation architecture
Stability-enhanced product	Moderate	Requires comparative data
PN admixture claims	Moderate	Can address practical compatibility problems
Packaging claims	Moderate	Useful if supported by adsorption or oxygen data
Manufacturing controls	Weak to moderate	Vulnerable to design-around
Method-of-use claims	Weak	Selenium supplementation is established
Device-enabled dosing	Moderate	Depends on technical novelty

The most defensible intellectual-property position would combine a specific formulation with a specific container and documented stability benefit. Even then, competitors may be able to avoid infringement through a different pH, concentration, closure, or packaging configuration.

What litigation and settlement risks affect the market?

Litigation risk is likely to be lower than in branded small-molecule markets. The principal disputes would more likely involve:

• ANDA approval and patent certifications
• Product quality or sterility
• False or misleading equivalence claims
• Trade secrets involving sterile manufacturing
• Supply contracts and exclusivity arrangements
• Regulatory exclusivity for a specific finished product

Settlement agreements could delay a generic launch only if a valid listed patent or other enforceable right exists. In the absence of a blocking patent, commercial launch timing would depend primarily on FDA approval and manufacturing capacity.

How does selenious acid compare with other selenium products?

Product type	Main use	Regulatory profile	Commercial position
Selenious acid injection	Parenteral nutrition	Prescription sterile drug	Hospital and pharmacy market
Oral sodium selenite	Dietary or therapeutic supplementation	Depends on product and jurisdiction	Broader retail and clinical use
Selenomethionine	Oral nutritional supplementation	Often dietary supplement or drug-specific	Consumer and nutrition markets
Selenium yeast	Nutritional supplementation	Generally supplement-oriented	Commodity nutrition market
Other injectable selenium salts	Limited or jurisdiction-specific	Product-specific	Potential alternative to selenious acid

For parenteral nutrition, the relevant comparison is not simply elemental selenium content. The decisive factors are sterility, concentration accuracy, compatibility, regulatory acceptance, and supply reliability.

Key Takeaways

• Selenious acid is primarily a selenium source for sterile injectable parenteral nutrition products.
• The active ingredient has no meaningful new-molecule exclusivity opportunity.
• The preferred excipient platform is simple: water for injection with sodium hydroxide and hydrochloric acid for pH adjustment.
• Formulation value lies in stability, compatibility, packaging, and dosing accuracy.
• Generic entry risk is high for conventional aqueous injections.
• Biosimilar risk does not apply.
• The strongest commercial opportunities are ready-to-use formats, pediatric dosing, shortage-resistant supply, and validated compatibility with parenteral nutrition systems.
• Patent protection is likely to be narrow and product-specific.
• Licensing value is concentrated in sterile manufacturing, regulatory files, distribution, and supply continuity.

FAQs

Is selenious acid the same as selenium injection?

No. Selenious acid is the chemical source of selenium. Selenium injection is the finished sterile drug product containing selenium, usually supplied as selenious acid in an aqueous formulation.

Can selenious acid injection be administered directly?

Product labeling generally requires controlled dilution or admixture before administration. Direct administration can create dosing and toxicity risks and must follow the approved labeling. [3]

Does selenious acid have biosimilar competition?

No. Biosimilar pathways apply to biological products. Selenious acid injection is a chemical sterile drug product and is exposed to conventional generic competition instead.

What is the most valuable formulation patent for selenious acid?

A patent covering a stable, low-dose formulation that maintains selenium assay and prevents precipitation or adsorption in parenteral nutrition admixtures would likely have the greatest commercial relevance.

Is selenious acid more attractive as a drug or as an excipient platform?

It is more attractive as a specialized injectable drug component and formulation platform than as a novel drug substance. Commercial value depends on sterile manufacturing, compatibility data, packaging, and hospital distribution.

References

1. National Institutes of Health, Office of Dietary Supplements. (2024). Selenium: Fact sheet for health professionals. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

2. National Academies of Sciences, Engineering, and Medicine. (2000). Dietary reference intakes for vitamin C, vitamin E, selenium, and carotenoids. National Academies Press. https://doi.org/10.17226/9810

3. DailyMed. (n.d.). Selenium injection, solution. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/

4. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book