List of Excipients in Branded Drug SODIUM PHENYLBUTYRATE

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Generic Drugs Containing SODIUM PHENYLBUTYRATE

Company	Ingredient	NDC	Excipient
Sigmapharm Laboratories LLC	sodium phenylbutyrate	42794-086	CALCIUM STEARATE
Sigmapharm Laboratories LLC	sodium phenylbutyrate	42794-086	SILICON DIOXIDE
ENDO USA Inc	sodium phenylbutyrate	49884-006	CALCIUM STEARATE
ENDO USA Inc	sodium phenylbutyrate	49884-006	SILICON DIOXIDE
ENDO USA Inc	sodium phenylbutyrate tablets, 500 mg	49884-170	CALCIUM STEARATE
ENDO USA Inc	sodium phenylbutyrate tablets, 500 mg	49884-170	CELLULOSE, MICROCRYSTALLINE

What are the Most Frequently-Used Excipients in SODIUM PHENYLBUTYRATE?

# Of NDCs	Excipient
4	CALCIUM STEARATE
4	CELLULOSE, MICROCRYSTALLINE
4	MAGNESIUM STEARATE
2	POVIDONE K30
6	SILICON DIOXIDE

Sodium Phenylbutyrate Excipient Strategy and Commercial Opportunities

Last updated: September 27, 2026

Sodium phenylbutyrate is a mature orphan-drug active ingredient with limited current patent protection and substantial formulation opportunity. The commercial gap is not basic API access. It is the ability to deliver high daily doses in a more palatable, lower-burden, pediatric-friendly format while preserving dose accuracy, chemical stability, and FDA substitutability.

The principal opportunities are:

• Taste-masked granules or powder for children.
• Lower-volume, dose-flexible oral products.
• Improved moisture and odor control.
• Excipient systems that reduce gastrointestinal intolerance.
• Compounded and hospital-use presentations.
• Generic or 505(b)(2) products differentiated from legacy tablets and powder.
• Regional products for markets where sodium phenylbutyrate remains less competitive than glycerol phenylbutyrate.

What is sodium phenylbutyrate used for?

Sodium phenylbutyrate is an ammonia-scavenging therapy for chronic management of patients with urea cycle disorders. It is metabolized to phenylacetate, which conjugates with glutamine to form phenylacetylglutamine. The conjugate is excreted through the kidneys, providing an alternative route for nitrogen elimination [1].

The FDA-approved BUPHENYL label covers tablets and oral powder. The products are used with dietary protein restriction and, in some cases, essential amino acid or nitrogen-free supplementation [1].

What are the main formulation constraints?

Sodium phenylbutyrate creates four commercial formulation problems:

Constraint	Commercial effect
High daily dose	Large tablet burden and high powder volume
Strong taste and odor	Low pediatric acceptability and adherence risk
High sodium load	Clinical concern in patients with cardiac, renal, hepatic, or hypertensive conditions
Dose variability in children	Need for flexible, accurate measurement across body weights

The sodium content is approximately 124 mg per gram of sodium phenylbutyrate. A patient receiving 10 grams per day therefore receives roughly 1.24 grams of sodium from the active ingredient alone, before dietary sodium is considered [1].

What excipients are used in sodium phenylbutyrate products?

The BUPHENYL tablet formulation uses conventional direct-compression excipients, including microcrystalline cellulose, colloidal silicon dioxide, magnesium stearate, povidone, and sodium starch glycolate, according to the FDA prescribing information [1].

The powder formulation uses a different excipient system intended for bulk oral dosing. The commercial purpose is dose delivery rather than tablet performance. Powder products must maintain uniformity during filling, storage, dispensing, and reconstitution or administration with food.

What does the current excipient strategy accomplish?

The legacy tablet formulation supports:

• Mechanical strength.
• Disintegration.
• Powder flow.
• Manufacturing scalability.
• Conventional solid-dose stability.

It does not fully solve the product’s primary patient-use problems. The tablet burden remains high, and the active ingredient’s taste and odor remain clinically relevant. The powder improves dose flexibility but introduces issues involving scoop accuracy, bulk density, segregation, dusting, and acceptability.

Which excipients offer the strongest commercial opportunity?

Taste-masking excipients

Taste masking is the highest-value formulation objective. Suitable systems may include:

• Lipid coating materials.
• Ethylcellulose or other water-insoluble polymers.
• Methacrylate copolymers.
• Hypromellose-based coatings.
• Ion-exchange resins.
• Cyclodextrin complexes.
• Multiparticulate polymer-coated granules.
• Flavor systems with sweeteners and acidulants.

A simple flavor addition is unlikely to be sufficient because sodium phenylbutyrate has both a strong taste and a characteristic odor. A physical barrier or complexation approach is more defensible commercially.

Taste masking must not delay release in the gastrointestinal tract. A coated granule platform should release the active ingredient rapidly after swallowing while limiting exposure in the oral cavity.

Granulation and flow-control excipients

A high-dose oral powder requires predictable bulk density and flow. Useful excipient categories include:

• Microcrystalline cellulose.
• Mannitol.
• Isomalt.
• Dibasic calcium phosphate.
• Colloidal silicon dioxide.
• Calcium silicate.
• Low-substituted hydroxypropyl cellulose.
• Crospovidone or related disintegrants in compacted granules.

Mannitol and isomalt can improve mouthfeel and reduce the gritty perception associated with mineral fillers. They also provide a neutral or mildly cooling sensory profile. Their use must be balanced against product volume because bulking excipients increase the amount administered per dose.

Moisture-control excipients

Moisture control is important because powder flow, coating integrity, odor, and chemical stability can deteriorate under high humidity. Commercial approaches include:

• Desiccant-integrated packaging.
• High-barrier multilayer bottles.
• Aluminum-based sachets.
• Moisture-scavenging closures.
• Low-moisture granulation processes.
• Silica or calcium-silicate flow aids.

The strongest product strategy combines a robust formulation with protective packaging. Packaging-only protection is less valuable if the product is repeatedly exposed to humidity during daily use.

Odor-control excipients

Odor control may require a different mechanism from taste masking. Potential approaches include:

• Polymer microencapsulation.
• Adsorbent carriers.
• Cyclodextrins.
• Inclusion complexes.
• Flavor systems with controlled release.
• Oxygen- and moisture-barrier packaging.

Odorants released during opening can affect caregiver acceptance even when the product is swallowed quickly. A formulation that controls the first-opening odor has a practical adherence advantage.

What formulations are protected or commercially differentiated?

The most defensible product concepts are not basic mixtures of sodium phenylbutyrate and standard excipients. They are integrated delivery systems with measurable performance advantages.

High-potential formulation concepts

Product concept	Patient benefit	Regulatory path	Commercial value
Taste-masked granules	Better pediatric acceptance	ANDA or 505(b)(2), depending on differences	High
Sachet-based powder	Portability and dose protection	ANDA or 505(b)(2)	Moderate to high
Unit-dose oral packets	Lower dosing error	ANDA or 505(b)(2)	High in pediatrics and hospitals
Sprinkle granules	Administration with soft food	Likely requires product-specific performance data	High
Rapid-dispersing powder	Easier administration	ANDA if pharmaceutically equivalent	Moderate
Chewable or orally disintegrating tablet	Reduced swallowing burden	Likely 505(b)(2) if materially different	Moderate to high
Low-volume concentrated liquid	Flexible dosing	505(b)(2) or new NDA strategy	High, but stability risk is material
Modified-release product	Reduced dosing frequency	505(b)(2) or new NDA	High development risk

A sodium phenylbutyrate suspension presents technical and commercial risks. The active ingredient’s high dose requires a large volume unless the formulation is highly concentrated. Sedimentation, taste, preservative selection, container compatibility, and microbial control would also complicate development.

When does sodium phenylbutyrate lose exclusivity?

Sodium phenylbutyrate has no meaningful remaining U.S. orphan exclusivity tied to the original BUPHENYL approval. BUPHENYL was approved in 1996, and orphan-drug exclusivity lasts seven years from approval under the Orphan Drug Act [1, 2].

The product’s principal U.S. commercial protections are therefore based on:

• FDA approval status.
• Brand recognition.
• Distribution and reimbursement relationships.
• Manufacturing reliability.
• Formulation know-how.
• Potentially private formulation or process patents.
• Clinical familiarity among metabolic-disease specialists.

The original active ingredient and basic oral dosage concepts are mature. A new entrant is more likely to compete through formulation, supply, price, or patient-support services than through composition-of-matter exclusivity.

What is the Orange Book status of sodium phenylbutyrate?

The FDA Orange Book identifies BUPHENYL as an approved prescription product under NDA 020572. The product includes tablet and powder dosage forms [2].

The commercial significance is that an ANDA applicant can potentially pursue a conventional generic pathway for a pharmaceutically equivalent sodium phenylbutyrate product. A materially different dosage form, taste-masking system, release profile, or administration method may require a 505(b)(2) application rather than a standard ANDA.

How do Orange Book listings affect a formulation entrant?

A formulation entrant must separate three questions:

1. Whether the active ingredient and dosage form are eligible for an ANDA.
2. Whether the proposed excipient system creates a pharmaceutical-equivalence issue.
3. Whether the formulation is sufficiently different to support a 505(b)(2) application and potentially new patent claims.

An excipient change alone does not guarantee 505(b)(2) status. The regulatory pathway depends on the extent of the difference, the reference product, and the additional clinical or product-performance data required by FDA.

Are there Paragraph IV challenges to sodium phenylbutyrate?

Sodium phenylbutyrate is not characterized by a current, high-value Orange Book patent barrier comparable to newer specialty products. The strategic risk for a generic applicant is therefore less likely to be patent litigation and more likely to involve:

• Product-specific manufacturing validation.
• Demonstration of pharmaceutical equivalence.
• Powder content uniformity.
• Dose-measuring accuracy.
• Stability under moisture stress.
• Labeling differences.
• Supply reliability for a small orphan market.

A Paragraph IV strategy would have limited value if no active, blocking Orange Book patent remains listed for the reference product. Patent disputes could still arise from formulation, process, packaging, or later-developed products, but those rights may not block an ANDA unless they are properly listed and enforceable against the proposed product.

How does sodium phenylbutyrate compare with glycerol phenylbutyrate?

Glycerol phenylbutyrate, marketed as RAVICTI, is a prodrug that provides phenylbutyrate through glycerol phenylbutyrate metabolism. It is not the same active pharmaceutical ingredient or dosage form as sodium phenylbutyrate.

Attribute	Sodium phenylbutyrate	Glycerol phenylbutyrate
Product examples	BUPHENYL and generics	RAVICTI
Sodium load	High	No sodium contribution from the active ingredient
Dosage burden	High	Lower volume in many regimens
Main formulation issue	Taste, odor, tablet or powder burden	Liquid administration and dose measurement
Regulatory history	Older approved product	Later orphan product
Competitive position	Lower-cost and generic-oriented	Premium specialty product
Formulation opportunity	Taste-masked granules and improved powders	Liquid stability, dosing devices, and adherence tools

RAVICTI received FDA approval in 2013 and had its own orphan-exclusivity period and product-specific patent estate [3, 4]. Its regulatory and patent history should not be used to infer equivalent protection for sodium phenylbutyrate.

How strong is the patent estate for sodium phenylbutyrate?

The foundational patent estate is weak from a new-entrant perspective because:

• The active ingredient is old.
• The BUPHENYL approval is more than two decades old.
• Orphan exclusivity has expired.
• Basic tablet and powder presentations are established.
• Generic competition has reduced the value of broad product claims.

The stronger patent opportunity is in narrow formulation claims, such as:

• Defined polymer coatings.
• Specific granule size distributions.
• Moisture-controlled compositions.
• Taste-masking combinations.
• Unit-dose packaging systems.
• Dose-measuring devices.
• Food-compatible sprinkle products.
• Stability-improving manufacturing processes.
• Specific dissolution or release profiles.

A claim directed only to sodium phenylbutyrate plus a conventional filler, lubricant, or sweetener would face substantial validity and obviousness risk. A patent application should tie the excipient system to a measurable technical effect, such as reduced bitterness, reduced odor emission, improved content uniformity, enhanced stability, or a defined dissolution profile.

What manufacturing and intellectual-property barriers exist?

API manufacturing is not the principal barrier. Sodium phenylbutyrate is a small-molecule sodium salt with established chemistry. The practical barriers are quality and scale.

Manufacturing risks

• Control of residual solvents and organic impurities.
• Salt formation and water-content control.
• Powder flow and segregation.
• Batch-to-batch odor variation.
• Uniform distribution in granules.
• Coating reproducibility.
• Moisture ingress during packaging.
• Accurate filling of high-dose sachets.
• Control of elemental impurities and microbial quality.

For pediatric products, dose uniformity is especially important. A multiparticulate product must prevent segregation between active particles, coating materials, sweeteners, and flavor components during transportation and dispensing.

Protectable manufacturing know-how

Trade-secret value may exist in:

• Granulation endpoint control.
• Coating-process parameters.
• Odor suppression.
• Low-shear blending.
• Packaging headspace control.
• Sachet filling.
• In-process content-uniformity testing.
• Long-term stability methods.

These process advantages may be commercially useful even where patent protection is narrow.

Which commercial opportunities are most attractive?

Pediatric taste-masked granules

This is the strongest opportunity. Urea cycle disorders often require chronic treatment beginning in infancy or childhood. A product that can be mixed with a small amount of soft food or liquid, without a strong taste or odor, can compete on adherence rather than price alone.

Unit-dose sachets

Unit-dose packaging can reduce caregiver dosing errors and improve portability. It is suitable for school, travel, hospital discharge, and emergency preparedness. Sachets also reduce repeated exposure of the bulk product to humidity.

Generic tablets with improved usability

A conventional generic tablet remains commercially viable if it offers reliable supply and competitive pricing. The opportunity is limited by dose burden. Tablet-count reduction is difficult without increasing tablet size, so a tablet-only strategy is less differentiated than a granule or powder platform.

Compounded and hospital products

Hospitals and metabolic centers may value standardized unit-dose powders, pharmacy-ready packets, or products compatible with enteral feeding protocols. A hospital-focused product could compete through packaging and workflow efficiency rather than retail brand recognition.

International markets

The commercial opportunity varies by geography:

• The United States offers established diagnosis, reimbursement, and specialist infrastructure.
• Europe has orphan-disease treatment networks but may favor different product presentations and local reimbursement strategies.
• Emerging markets may favor lower-cost powder or tablet products.
• Markets with limited access to glycerol phenylbutyrate may present demand for sodium phenylbutyrate despite its sodium burden.

Country-level launch strategy must account for local reference products, food and drug regulations, pediatric labeling, and reimbursement.

What revenue exposure does formulation improvement create?

Sodium phenylbutyrate is a niche product, so the absolute market is smaller than for mass-market chronic medicines. Its commercial value comes from high treatment intensity, long duration of use, and specialist prescribing.

Revenue upside is greatest where a new product can:

• Replace a branded product.
• Capture patients who cannot tolerate legacy tablets or powder.
• Reduce switching to glycerol phenylbutyrate.
• Improve persistence in pediatric patients.
• Secure preferred specialty-pharmacy or hospital distribution.
• Obtain orphan-drug positioning for a materially differentiated formulation.

A low-cost ANDA can achieve volume through substitution. A 505(b)(2) product requires a stronger clinical and economic proposition but can support higher pricing if it solves taste, sodium, or administration problems.

What generic launch scenarios exist?

Scenario	Product strategy	Likely market position
Low-cost ANDA	Same dosage form and strength	Price competition
Premium generic powder	Better packaging and measuring system	Moderate differentiation
Taste-masked granules	Pediatric administration advantage	Stronger pricing power
Unit-dose packets	Dosing accuracy and portability	Institutional and specialty use
505(b)(2) liquid	Flexible pediatric dosing	High development and stability burden
Sprinkle formulation	Food-compatible administration	Potential adherence leader

The fastest route is usually a pharmaceutically equivalent product. The most defensible commercial route is a taste-masked multiparticulate product with strong performance data and a focused pediatric label.

Key Takeaways

• Sodium phenylbutyrate has limited remaining exclusivity value and no obvious foundational patent barrier.
• The main commercial problem is administration, not API availability.
• Taste, odor, sodium load, high dose volume, and pediatric measurement are the central formulation targets.
• Taste-masked granules and unit-dose sachets offer the clearest differentiation.
• Conventional tablets remain vulnerable to dose burden and poor pediatric usability.
• A standard generic is likely to compete on price and supply reliability.
• A materially improved formulation may support a 505(b)(2) strategy and new formulation patents.
• Glycerol phenylbutyrate is a competitive benchmark, but its patent and regulatory history should not be attributed to sodium phenylbutyrate.
• Manufacturing know-how in coating, moisture control, dose uniformity, and packaging may have more practical value than broad composition claims.
• The strongest launch strategy combines pediatric acceptability, accurate dosing, moisture protection, and specialist distribution.

FAQs

Can sodium phenylbutyrate be formulated as a pediatric sprinkle product?

Yes. A multiparticulate granule can be designed for administration with soft food or liquid. The principal development requirements are taste masking, rapid release, content uniformity, low segregation, and dose-measuring accuracy.

Does reducing the sodium content create a new sodium phenylbutyrate product?

Not ordinarily. The sodium is part of the active salt. Reducing sodium exposure generally requires a different chemical form, a different active ingredient, or a different treatment strategy. That change may fall outside a conventional sodium phenylbutyrate ANDA.

Is a flavored sodium phenylbutyrate powder likely to be patentable?

Flavor alone is usually a weak basis for patent protection. A stronger application would claim a defined taste-masking system that produces measurable improvement in bitterness, odor, dissolution, stability, or patient administration.

Can a sodium phenylbutyrate product use the same excipients as BUPHENYL?

Potentially, but the proposed product must meet applicable pharmaceutical-equivalence, quality, labeling, and inactive-ingredient requirements. Excipient selection also must account for pediatric exposure and route of administration [5].

What is the most commercially defensible sodium phenylbutyrate product?

A moisture-protected, taste-masked, unit-dose granule that can be mixed with a small amount of food is the strongest differentiated concept. It addresses the product’s principal adherence and dosing problems without requiring a higher-risk modified-release platform.

References

1. U.S. Food and Drug Administration. (2022). BUPHENYL (sodium phenylbutyrate) tablets and powder: Prescribing information.
2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
3. U.S. Food and Drug Administration. (2013). RAVICTI (glycerol phenylbutyrate) oral liquid: Prescribing information.
4. U.S. Food and Drug Administration. (2024). Orphan drug designations and approvals database.
5. U.S. Food and Drug Administration. (2024). Inactive Ingredient Database.