List of Excipients in Branded Drug EXTENDED PHENYTOIN SODIUM

Generic Drugs Containing EXTENDED PHENYTOIN SODIUM

Company	Ingredient	NDC	Excipient
NCS HealthCare of KY LLC dba Vangard Labs	phenytoin sodium	0615-8556	CELLULOSE, MICROCRYSTALLINE
NCS HealthCare of KY LLC dba Vangard Labs	phenytoin sodium	0615-8556	FERROSOFERRIC OXIDE
NCS HealthCare of KY LLC dba Vangard Labs	phenytoin sodium	0615-8556	GELATIN
NCS HealthCare of KY LLC dba Vangard Labs	phenytoin sodium	0615-8556	HYPROMELLOSE 2910
NCS HealthCare of KY LLC dba Vangard Labs	phenytoin sodium	0615-8556	MAGNESIUM OXIDE

What are the Most Frequently-Used Excipients in EXTENDED PHENYTOIN SODIUM?

# Of NDCs	Excipient
7	CELLULOSE, MICROCRYSTALLINE
4	D&C RED NO. 28
4	D&C RED NO. 33
4	D&C YELLOW NO. 10
7	FD&C BLUE NO. 1

Extended-Release Phenytoin Sodium: Excipient Strategy and Commercial Opportunities

Last updated: August 9, 2026

Extended-release phenytoin sodium is a mature, price-sensitive oral dosage market. The strongest commercial opportunities are not broad patent exclusivity plays. They are formulation-control, supply reliability, patient-tolerability, and differentiated presentation opportunities built around phenytoin's narrow therapeutic index, nonlinear pharmacokinetics, and sensitivity to changes in dissolution and absorption.

The principal product is extended-release phenytoin sodium capsules, historically marketed as Dilantin Kapseals. Generic manufacturers compete through abbreviated new drug applications, manufacturing efficiency, contract supply, dosage-form differentiation, and reliable distribution. Excipient selection is commercially important because changes in particle wetting, capsule fill, bead structure, dissolution, and gastrointestinal release can affect exposure.

What is extended-release phenytoin sodium?

Extended-release phenytoin sodium is an oral dosage form designed to release phenytoin over a longer period than immediate-release capsules or suspensions. It is used primarily for seizure control and seizure prophylaxis.

Phenytoin has two properties that drive formulation strategy:

1. It has a narrow therapeutic range, so clinically relevant exposure changes can occur from modest differences in absorption.
2. It follows nonlinear, capacity-limited metabolism. Small dose increases can produce disproportionate increases in plasma concentration.[1]

The active ingredient is phenytoin sodium, not equivalent by weight to the same nominal amount of phenytoin base. Product labeling typically expresses capsule strength in terms of phenytoin sodium while identifying the corresponding phenytoin content.

Typical commercial presentations

Presentation	Common commercial use	Excipient and manufacturing considerations
100 mg extended-release capsule	Core chronic-maintenance strength	Highest-volume presentation; fill weight, content uniformity, dissolution and capsule-shell performance are critical
30 mg extended-release capsule	Dose titration and maintenance adjustment	Commercial value comes from dose flexibility and reduced need for capsule splitting
Immediate-release capsule	Alternative oral presentation	Different absorption profile; not automatically interchangeable with extended-release products
Oral suspension	Pediatric or swallowing-related use	Sedimentation, redispersibility, particle-size control and preservative strategy are central
Injection	Acute loading or inpatient use	Requires separate parenteral formulation, solvent, pH and container-compatibility controls

What excipients are used in extended-release phenytoin sodium capsules?

Extended-release phenytoin sodium capsules generally use conventional oral solid-dose excipients, including fillers, binders or granulation aids, lubricants, glidants, wetting agents, and capsule-shell materials. The exact composition varies by manufacturer and should be taken from the current product label and inactive-ingredient listing.[2]

Excipient classes and their functions

Excipient class	Potential function	Commercial relevance
Lactose or another filler	Provides bulk and improves fill consistency	Low cost, established supply chain, but may create a lactose-intolerance or label-positioning issue
Sucrose or other soluble carbohydrate	Supports pellet or bead formation	Can affect dissolution, moisture sensitivity and manufacturing robustness
Talc or colloidal silicon dioxide	Improves flow and reduces adhesion	Useful for capsule-filling consistency; excessive use can alter powder behavior
Magnesium stearate	Lubrication during compression or encapsulation	Over-lubrication can reduce wetting and slow dissolution
Sodium lauryl sulfate or another surfactant	Improves wetting of poorly soluble phenytoin	May improve dissolution but can create tolerability and regulatory justification issues
Gelatin or hypromellose	Capsule shell	Hypromellose may support vegetarian or religious-market positioning
Titanium dioxide and colorants	Appearance and product identification	Relevant to patient recognition, supply continuity and colorant restrictions
Coating polymers	Modified release or bead protection	Determine release profile, mechanical durability and scale-up risk

The commercial objective is not to maximize the number of excipients. It is to produce a reproducible release profile with a defensible manufacturing process and a low risk of clinically meaningful exposure changes.

How does excipient selection affect phenytoin bioavailability?

Excipient selection can affect phenytoin through wetting, particle dispersion, gastric emptying interactions, dissolution rate, bead integrity and gastrointestinal transit. Phenytoin is poorly water soluble, so the formulation must control the balance between dissolution and release.

For an extended-release capsule, the most important variables are:

• Active-particle size and polymorphic form
• Sodium phenytoin crystallinity and moisture content
• Granule or pellet porosity
• Surfactant concentration
• Lubricant level and mixing time
• Coating weight gain
• Capsule-shell disintegration
• Dissolution behavior across pH conditions
• Stability under humidity and temperature stress

A formulation that releases phenytoin too quickly can increase peak exposure and adverse-event risk. A formulation that releases too slowly can reduce trough concentrations or delay attainment of therapeutic concentrations. Both outcomes can create clinical and substitution concerns.

FDA labeling warns that dosage-form changes can affect phenytoin exposure and that patients should be monitored when switching between formulations.[1] This creates a higher commercial premium for manufacturing consistency than would apply to many conventional immediate-release generic products.

What excipient strategy is strongest for a generic extended-release phenytoin product?

The strongest strategy is usually a conservative, reference-aligned formulation combined with robust control of critical material attributes and dissolution.

Strategy 1: Reference-product matching

A generic manufacturer can minimize regulatory and substitution risk by matching the reference product's key performance characteristics rather than pursuing unnecessary excipient novelty. This approach reduces the probability that a new excipient system creates a bioequivalence or post-approval change problem.

Priority controls include:

• Similar release mechanism
• Comparable dissolution across multiple media
• Consistent capsule fill and weight
• Tight assay and content-uniformity limits
• Controlled active-particle size
• Defined lubricant mixing limits
• Moisture-protective packaging
• Stability data under long-term and accelerated conditions

Strategy 2: Lactose-free positioning

A lactose-free capsule could create a modest commercial niche among patients reporting lactose intolerance or among institutions that prefer simplified excipient profiles. The opportunity is limited because lactose intolerance does not necessarily preclude use of the small quantities present in pharmaceutical capsules.

A lactose-free product would need to demonstrate:

• Equivalent dissolution and bioavailability
• Similar manufacturability
• Stable supply of the replacement filler
• No adverse impact on capsule fill weight or content uniformity
• Clear labeling that avoids unsupported clinical claims

Mannitol, microcrystalline cellulose, starch derivatives and dibasic calcium phosphate are possible replacement categories, but each changes density, flow, moisture behavior or compaction characteristics.

Strategy 3: Hypromellose capsule shells

Hypromellose shells can support vegetarian, halal, kosher and gelatin-avoidance positioning. They may also reduce dependence on animal-derived gelatin supply.

The main technical issue is not the shell's marketing value. It is shell performance. Differences in moisture content, mechanical strength, disintegration and compatibility with the fill can affect release and stability. A hypromellose-shell product requires comparative dissolution work and robust packaging validation.

Strategy 4: Improved bead or pellet technology

Multiparticulate delivery can improve release control and reduce the impact of a single unit defect. It also supports more consistent distribution of phenytoin through the gastrointestinal tract.

The principal barriers are manufacturing complexity and cost. Coating uniformity, friability, agglomeration, capsule-fill segregation and scale-up reproducibility can erode the commercial advantage.

Strategy 5: Sprinkle or swallowing-related presentation

A capsule that can be opened and sprinkled on soft food could address swallowing difficulties, but this is a high-risk claim for an extended-release product. The manufacturer would need evidence that opening the capsule does not damage the release mechanism, alter dose uniformity or cause dose dumping.

A sprinkle presentation would have greater commercial value in pediatric, geriatric and long-term-care channels, but the regulatory burden would be materially higher than for a conventional capsule.

What regulatory pathway applies to extended-release phenytoin sodium?

A conventional generic extended-release capsule would generally use the 505(j) ANDA pathway if it can demonstrate pharmaceutical equivalence and bioequivalence to the reference-listed drug.[3]

The regulatory package typically includes:

• Active ingredient and dosage-form equivalence
• Comparative dissolution
• In vitro release characterization
• Pharmacokinetic bioequivalence
• Stability data
• Manufacturing-process validation
• Container-closure qualification
• Inactive-ingredient justification
• Labeling consistent with the reference product

A materially different delivery system, novel patient population claim, or significant formulation change may require a 505(b)(2) application rather than a standard ANDA. That route could support a differentiated product but would involve greater development cost and clinical or bridging requirements.

What is the Orange Book and patent status of extended-release phenytoin sodium?

Extended-release phenytoin sodium is a mature small-molecule product. The original composition, formulation and basic use patents associated with early branded products are generally historical rather than current sources of meaningful exclusivity. Commercial entry is therefore primarily governed by FDA approval status, manufacturing capability, product quality and contracting position.

The FDA Orange Book identifies reference-listed drugs, approved generic equivalents and relevant patent or exclusivity information.[4] For a specific product, the applicable assessment should distinguish:

• The reference-listed drug
• Current approved ANDAs
• Listed patents, if any
• Pediatric exclusivity
• Other regulatory exclusivity
• Discontinued or withdrawn products
• Therapeutic-equivalence codes

Are Paragraph IV challenges a major issue?

For a mature extended-release phenytoin product, Paragraph IV litigation is usually less important than it is for a recently launched branded medicine. The principal risks are more likely to involve:

• Approval delays from deficiencies
• Bioequivalence disputes
• Manufacturing inspections
• Product-quality enforcement
• Supply interruptions
• State substitution and contracting dynamics

A current Paragraph IV assessment must be based on the live Orange Book listing and the applicant's certification. Historical patents should not be treated as active barriers without confirming their listing and expiration status.[4]

What patent opportunities exist in phenytoin excipients and formulations?

Broad patent protection for phenytoin sodium itself is weak because the active ingredient is old and widely available. Potentially protectable subject matter is narrower and may include:

• Specific multiparticulate release architecture
• Defined coating compositions and thickness ranges
• Stabilized phenytoin sodium particles
• Novel capsule-shell and fill combinations
• Sprinkle formulations with preserved extended release
• Abuse-deterrent or tamper-resistant presentations
• Improved dissolution under specified pH conditions
• Manufacturing processes that reduce batch variability
• Packaging systems that control moisture-related degradation
• Combination products involving therapeutic monitoring or adherence technology

Patent strength depends on claim scope, enablement, freedom-to-operate, design-around options and whether the product can command a reimbursement premium. A patent covering a narrow coating range may have limited commercial value if competitors can use a different polymer or process.

What manufacturing and intellectual-property barriers matter?

The main barriers are technical rather than molecule-level patent barriers:

1. Reproducible extended-release performance at commercial scale.
2. Consistent phenytoin sodium particle attributes.
3. Demonstrated bioequivalence despite narrow-therapeutic-index concerns.
4. Reliable supply of capsule shells and specialized coating materials.
5. Control of moisture, dissolution drift and fill-weight variation.
6. Documentation supporting post-approval changes.

These barriers can protect a capable manufacturer even when formal patent protection is limited.

What commercial opportunities exist for manufacturers?

Generic supply and contract manufacturing

The largest opportunity is reliable supply of 30 mg and 100 mg capsules. Hospitals, wholesalers and managed-care buyers value continuity because phenytoin switching can require therapeutic-drug monitoring and clinical oversight.

A manufacturer can compete through:

• Dual-source raw materials
• Domestic or regional capsule-shell supply
• Capacity reserved for shortage response
• Consistent product availability
• Low-cost packaging configurations
• Institutional supply contracts
• Pharmacist-facing substitution support

Premium generic positioning

A modest premium may be available for:

• Lactose-free formulations
• Hypromellose capsules
• Colorant-reduced products
• Unit-dose hospital packaging
• Tamper-evident packaging
• Verified sprinkle-compatible presentations
• Better dose-strength availability
• Supply commitments for underserved markets

The premium must be supported by a meaningful procurement or adherence benefit. Excipient novelty alone is unlikely to support durable pricing power.

Geographic expansion

The strongest geographic opportunities are markets where:

• Extended-release capsules are approved but intermittently supplied
• Local production is limited
• Imported products have long lead times
• Phenytoin remains widely used because newer antiseizure medicines are less affordable
• Regulatory pathways accept established active ingredients with local bioequivalence data

Local requirements for bioequivalence, stability zones, packaging, colorants and gelatin sourcing can affect launch timing.

How does extended-release phenytoin compare with newer antiseizure medicines?

Factor	Extended-release phenytoin sodium	Newer antiseizure medicines
Molecule maturity	Very old, widely genericized	Often protected by recent patents or exclusivity
Price	Usually low	Often materially higher
Therapeutic monitoring	Commonly relevant	Less frequent for many products
Pharmacokinetics	Nonlinear and formulation-sensitive	Varies by product
Excipient differentiation	Potentially useful but limited	More room for premium delivery systems
Commercial barrier	Manufacturing consistency and supply	Patent, clinical and regulatory exclusivity
Growth profile	Stable or declining in many high-income markets	Greater opportunity in treatment-switching and new starts

Phenytoin remains commercially relevant in low-cost treatment settings, hospitals, seizure prophylaxis protocols and markets where access to newer agents is limited. Its use can decline as clinicians shift patients to levetiracetam, lamotrigine, valproate and other alternatives.

What revenue exposure and launch risks should investors assess?

Revenue exposure depends on the manufacturer's concentration in phenytoin, customer mix and ability to maintain supply. A product with low unit pricing can still be strategically important if it supports institutional contracts or fills a manufacturing line efficiently.

Key risks include:

• Price erosion from multiple ANDA suppliers
• Low market growth
• Clinical reluctance to switch stable patients
• Supply interruption
• Recall risk from dissolution or content-uniformity failures
• Dependence on one capsule-shell supplier
• Increased monitoring during product transitions
• Declining use in favor of newer antiseizure medicines

A differentiated excipient strategy is most attractive when it improves supply continuity or creates a clearly defined patient-use benefit. It is less attractive when it adds manufacturing complexity without improving reimbursement or procurement access.

Key Takeaways

• Extended-release phenytoin sodium is a mature generic market with limited value from legacy molecule patents.
• Excipient selection matters because phenytoin has nonlinear pharmacokinetics and a narrow therapeutic range.
• Reference-aligned formulations with tight dissolution and manufacturing controls offer the lowest regulatory risk.
• Lactose-free, hypromellose-shell, unit-dose and swallowing-related presentations offer targeted commercial opportunities.
• Sprinkle and novel multiparticulate products could command higher value but require stronger bioequivalence, dose-uniformity and release-control evidence.
• Current Orange Book listings, approved ANDAs and live patent entries determine the actual regulatory and litigation position.
• The strongest barriers are manufacturing reproducibility, supply reliability and clinical confidence rather than broad active-ingredient patent protection.
• Generic launch economics are driven by procurement access, shortage resilience and production cost.

FAQs

Can phenytoin extended-release capsules use a new excipient without a new clinical program?

A new excipient may be used in an ANDA when the formulation remains within the applicable regulatory framework and the applicant supports safety, pharmaceutical equivalence, dissolution and bioequivalence. A materially different excipient system or release mechanism can increase the evidence required.

Is lactose-free extended-release phenytoin a strong commercial opportunity?

It is a targeted opportunity rather than a mass-market strategy. The product would need equivalent performance, reliable replacement-filler supply and a procurement or adherence benefit that justifies development and manufacturing costs.

Can phenytoin extended-release capsules be opened and sprinkled?

The answer depends on the specific product. Opening a modified-release capsule can alter release behavior unless the product is expressly labeled for sprinkling. Product-specific evidence is required before making that claim.

What is the most important quality test for extended-release phenytoin?

Comparative dissolution across relevant media is among the most important tests, together with assay, content uniformity, stability and pharmacokinetic bioequivalence. Dissolution changes can signal clinically relevant release differences.

Are biosimilars relevant to extended-release phenytoin sodium?

No. Phenytoin sodium is a chemically synthesized small molecule, so competition occurs through generic-drug pathways rather than biosimilar applications.

References

1. U.S. Food and Drug Administration. (2023). Dilantin (phenytoin sodium) extended capsules prescribing information. DailyMed.

2. U.S. National Library of Medicine. (2024). DailyMed: Phenytoin sodium extended-release capsules, inactive ingredients and labeling. DailyMed.

3. U.S. Food and Drug Administration. (2024). Abbreviated new drug application (ANDA) process. FDA.

4. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

5. U.S. Food and Drug Administration. (2023). Bioavailability and bioequivalence studies submitted in NDAs or INDs: General considerations. FDA.