List of Excipients in Branded Drug PHENYTEK

Generic Drugs Containing PHENYTEK

Company	Ingredient	NDC	Excipient
Mylan Pharmaceuticals Inc	extended phenytoin sodium	0378-2670	D&C YELLOW NO. 10 ALUMINUM LAKE
Mylan Pharmaceuticals Inc	extended phenytoin sodium	0378-2670	FD&C BLUE NO. 1 ALUMINUM LAKE
Mylan Pharmaceuticals Inc	extended phenytoin sodium	0378-2670	FD&C BLUE NO. 2
Mylan Pharmaceuticals Inc	extended phenytoin sodium	0378-2670	FD&C RED NO. 40
Mylan Pharmaceuticals Inc	extended phenytoin sodium	0378-2670	FERROSOFERRIC OXIDE

What are the Most Frequently-Used Excipients in PHENYTEK?

# Of NDCs	Excipient
2	D&C YELLOW NO. 10 ALUMINUM LAKE
2	FD&C BLUE NO. 1 ALUMINUM LAKE
2	FD&C BLUE NO. 2
2	FD&C RED NO. 40
2	FERROSOFERRIC OXIDE

PHENYTEK Excipient Strategy and Commercial Opportunities

Last updated: September 24, 2026

PHENYTEK is an extended-release phenytoin sodium capsule used for seizure control. Its commercial opportunity is driven by formulation reliability, supply continuity, hospital and pharmacy substitution, and the technical difficulty of matching an established modified-release product. The strongest excipient strategy is a conservative, compositionally familiar capsule platform that controls phenytoin release without materially changing food effects, dose dumping risk, or bioavailability.

What is PHENYTEK and how is it formulated?

PHENYTEK contains phenytoin sodium in extended-release hard capsules. The marketed strengths are 100 mg and 200 mg capsules. The product is intended to maintain phenytoin exposure over an extended dosing interval and is not interchangeable on a milligram-for-milligram basis with all other phenytoin formulations.

The PHENYTEK label identifies inactive ingredients associated with the capsule fill and shell. Public labeling should be used as the controlling source for any regulatory or formulation decision because excipient composition can change across approved manufacturers and manufacturing sites. The reported formulation platform includes conventional pharmaceutical excipients such as lactose, maize starch, sodium lauryl sulfate, talc, magnesium stearate, gelatin, and colorants.[1]

Product attribute	PHENYTEK position
Active ingredient	Phenytoin sodium
Dosage form	Extended-release hard capsule
Commercial strengths	100 mg and 200 mg
Therapeutic area	Epilepsy and seizure disorders
Release type	Extended release
Regulatory pathway	FDA-approved NDA product
Substitution risk	Formulation-dependent; requires attention to therapeutic drug monitoring
Key formulation concern	Maintaining comparable phenytoin exposure and release behavior

Phenytoin has a narrow therapeutic range and nonlinear pharmacokinetics. Small changes in dose or exposure can produce disproportionate changes in plasma concentration. Formulation changes therefore carry more commercial and regulatory risk than changes to a conventional immediate-release product.[2]

What excipients are most important in PHENYTEK?

The commercial formulation strategy should prioritize excipients that control powder flow, capsule-fill uniformity, release behavior, lubrication, and physical stability.

Fill diluent and dose uniformity

Lactose or another inert diluent provides bulk and supports capsule-fill consistency. The 100 mg and 200 mg strengths require reliable content uniformity because phenytoin sodium is a high-potency active ingredient relative to the total capsule fill.

A replacement diluent could create opportunities for:

• lactose-free positioning;
• reduced moisture sensitivity;
• improved powder flow;
• lower capsule weight;
• simplified global sourcing;
• improved compatibility with automated encapsulation.

Any replacement should preserve blend uniformity and dissolution. Direct substitution of lactose with microcrystalline cellulose, mannitol, dibasic calcium phosphate, or pregelatinized starch could alter density, wettability, compactability, and gastrointestinal release.

Starch and disintegration control

Maize starch can support dispersion and capsule-fill performance. In an extended-release product, the amount and grade of starch require careful control. Excessive disintegration can shorten release, while insufficient dispersion can create variability between capsules.

A commercial developer should evaluate:

• native versus pregelatinized starch;
• particle-size distribution;
• water uptake;
• swelling behavior;
• effect on dissolution after capsule-shell rupture;
• interaction with hydrophobic lubricants.

Surfactant and wetting control

Sodium lauryl sulfate can improve wetting of phenytoin sodium and reduce batch-to-batch dissolution variability. It may also increase the risk of an overly rapid initial release if the formulation depends on hydrophobic barriers or poorly wettable particles to moderate release.

A lower-surfactant or surfactant-free version could appeal to customers seeking a simpler excipient profile, but this opportunity is technically difficult. It would require demonstrated control of:

• capsule opening;
• drug wetting;
• initial release;
• terminal release;
• fed-versus-fasted exposure;
• storage-related dissolution drift.

Lubricant and glidant system

Magnesium stearate supports manufacturing but can create a hydrophobic film around particles when overmixed. That effect can slow dissolution and amplify scale-up differences.

Talc can improve flow and reduce adhesion. The combined lubricant and glidant system should be optimized through:

• lubricant concentration;
• blending time;
• shear exposure;
• particle morphology;
• equipment transfer;
• capsule-machine speed.

These variables are commercially relevant because a product that passes laboratory dissolution but fails at commercial scale can generate supply interruptions and regulatory reporting costs.

Capsule shell

The gelatin shell is familiar, inexpensive, and widely accepted. A plant-based shell based on hypromellose could create a differentiated product for vegetarian, religious, or gelatin-sensitive markets. The change would require evaluation of:

• shell moisture;
• brittleness;
• oxygen and moisture permeability;
• machine performance;
• dissolution lag;
• storage stability;
• visual identification;
• compatibility with colorants and printing inks.

The capsule shell is a potential line-extension opportunity, but it is unlikely to create durable exclusivity by itself. Its value would be commercial and operational rather than patent-based.

What excipient strategy best supports a PHENYTEK generic?

The lowest-risk strategy is a close qualitative and quantitative formulation match to the reference product. A generic developer should first target reference-like excipients and process conditions, then pursue differentiated versions after establishing a compliant baseline.

Strategy	Regulatory risk	Commercial value	Technical difficulty
Reference-like formulation	Low to moderate	High	Moderate
Lactose-free formulation	Moderate	Moderate	Moderate to high
Plant-based capsule shell	Moderate	Niche to moderate	Moderate
Surfactant-reduced formulation	High	Moderate	High
New polymer-based release system	High	Potentially high	Very high
Abuse-deterrent or tamper-resistant version	High	Uncertain	High

The reference-like formulation has the clearest path to an abbreviated new drug application. A materially different excipient system could trigger greater bioequivalence risk and may complicate waiver arguments, dissolution comparisons, and manufacturing-process validation.

For phenytoin, the formulation should be designed around exposure equivalence rather than dissolution alone. Dissolution testing remains necessary, but pharmacokinetic comparability is the commercial gatekeeper.

What formulation patents protect PHENYTEK?

PHENYTEK is an old-molecule product, and the core composition is unlikely to be protected by a commercially meaningful, unexpired U.S. patent. The primary competitive barriers are formulation know-how, regulatory approval, manufacturing consistency, physician confidence, and supply reliability.

Potentially relevant intellectual-property categories include:

• extended-release phenytoin capsule compositions;
• coating or matrix systems;
• dissolution-control methods;
• capsule manufacturing processes;
• polymorph or particle-size control;
• methods for reducing food effects;
• manufacturing specifications and analytical methods.

A generic applicant should distinguish between patents listed in the FDA Orange Book and broader historical patents that may have expired or may not block an ANDA. The Orange Book remains the relevant source for listed patents and regulatory exclusivity.[3]

What is the Orange Book status of PHENYTEK?

PHENYTEK should be assessed through the current FDA Orange Book entry for its approved NDA. For an old extended-release phenytoin product, the commercial expectation is limited remaining patent-based protection, with competition determined mainly by approved generic products and market supply.

Key diligence points are:

Orange Book issue	Commercial implication
NDA status	Confirms the reference product and approval status
Listed patents	Determines whether a Paragraph IV certification may be required
Pediatric exclusivity	Could delay approval if present
Exclusivity code	Identifies remaining regulatory protection
Therapeutic-equivalence codes	Indicates substitutability among approved products
Reference-listed drug status	Determines ANDA reference eligibility

The Orange Book status should be reviewed before committing to a launch date because listed patents, delistings, and reference-product designations can change.[3]

When does PHENYTEK lose exclusivity?

PHENYTEK’s principal exclusivity risk is generic substitution rather than biosimilar competition. Phenytoin sodium is a small molecule, so products would use the ANDA pathway rather than the biosimilar pathway.

Because PHENYTEK is an established product, its commercial exclusivity is generally expected to depend on:

1. remaining Orange Book patents;
2. any unexpired statutory exclusivity;
3. the existence of approved therapeutically equivalent products;
4. state substitution rules;
5. pharmacy and wholesaler contracting.

The product’s practical exclusivity is therefore more likely to have expired or become limited well before the current commercial period. The main question is not whether generic entry is legally possible, but whether a new entrant can achieve reliable bioequivalence, obtain adequate manufacturing economics, and secure pharmacy distribution.

Are there Paragraph IV challenges to PHENYTEK?

A Paragraph IV challenge is relevant only if an unexpired Orange Book patent is listed for the reference product. For a legacy phenytoin sodium extended-release capsule, the likelihood of a commercially meaningful current Paragraph IV event is lower than for a recently approved product.

A new applicant should evaluate:

• whether any listed patent remains unexpired;
• whether the patent covers the drug substance, formulation, or method of use;
• whether the patent is relevant to the proposed strength and dosage form;
• whether a certification under Paragraph IV is required;
• whether a Paragraph IV notice would expose the applicant to a 30-month stay under the Hatch-Waxman framework.[4]

The absence of a significant patent barrier does not eliminate launch risk. Product-specific bioequivalence requirements and manufacturing observations can delay approval without litigation.

What generic entry risks exist for PHENYTEK?

Generic entry risk is high at the legal level but more moderate at the execution level.

Legal risk

The underlying active ingredient is old and widely used. Core compound protection is not the expected barrier. Any remaining protection would more likely relate to formulation or method of use.

Regulatory risk

Extended-release phenytoin capsules require careful control of exposure. Risk areas include:

• dose dumping;
• food-related exposure changes;
• interbatch dissolution variability;
• strength proportionality;
• capsule-shell effects;
• nonlinear pharmacokinetics;
• failure to match the reference product at clinically relevant time points.

Commercial risk

Phenytoin is a mature, price-sensitive market. A new entrant could face low margins, limited formulary differentiation, and incumbent generic competition. The opportunity improves where there are:

• recurring shortages;
• few active suppliers;
• hospital demand for reliable supply;
• pharmacy preference for a specific capsule presentation;
• demand for alternative excipient profiles;
• contract-manufacturing capacity constraints.

Which companies are challenging or competing with PHENYTEK?

Competition is likely to come from three groups:

1. generic manufacturers of phenytoin sodium extended-release capsules;
2. manufacturers of other phenytoin dosage forms, including immediate-release products and injectable formulations;
3. alternative antiseizure medicines such as levetiracetam, carbamazepine, valproate, and lamotrigine.

The most direct competitors are FDA-approved therapeutically equivalent extended-release phenytoin capsules. Competitive analysis should use current FDA Orange Book therapeutic-equivalence data rather than brand visibility alone.[3]

A generic company with an existing capsule platform, established pharmacokinetic infrastructure, and controlled-substance distribution capability would have a stronger position than a new entrant building the entire supply chain from scratch.

How does PHENYTEK compare with Dilantin and other phenytoin products?

PHENYTEK and Dilantin Kapseals occupy similar extended-release capsule categories, but the products should not be treated as automatically interchangeable without confirming their approved therapeutic-equivalence status and labeling.

Attribute	PHENYTEK	Dilantin Kapseals	Immediate-release phenytoin
Active ingredient	Phenytoin sodium	Phenytoin sodium	Usually phenytoin sodium or phenytoin
Dosage form	Extended-release capsule	Extended-release capsule	Capsule, tablet, or suspension
Main commercial issue	Reliable extended exposure	Established brand recognition	More flexible dosing, higher fluctuation risk
Formulation sensitivity	High	High	Moderate to high
Substitution concern	Exposure and seizure control	Exposure and seizure control	Different dosing interval and profile
Generic opportunity	Established	Established	Established

The relevant commercial differentiation is unlikely to be therapeutic efficacy. It is more likely to involve supply assurance, capsule-shell preferences, excipient exclusions, packaging, and consistent pharmacokinetic performance.

What commercial opportunities exist for a PHENYTEK excipient strategy?

1. Lactose-free PHENYTEK-compatible capsule

A lactose-free version could target patients with lactose intolerance and institutional buyers seeking simplified excipient profiles. The opportunity is limited by the need to preserve powder flow, fill weight, dissolution, and bioequivalence.

Potential replacements include microcrystalline cellulose, mannitol, dibasic calcium phosphate, or alternative starch systems. Each replacement affects density and release differently.

2. Vegetarian or plant-based capsule shell

A hypromellose capsule could provide a clear marketing distinction. This is most relevant in retail, specialty pharmacy, and international markets where gelatin restrictions influence purchasing.

The product would need a strong identification system because capsule appearance changes can increase dispensing errors in a narrow-therapeutic-index drug.

3. Supply-chain-secure formulation

The highest practical value may come from reducing dependence on a single excipient supplier. A dual-source strategy for diluent, starch, lubricant, colorant, and capsule shell can protect margins more effectively than a new patentable excipient system.

4. Pediatric and geriatric usability

An extended-release capsule is not always convenient for patients with swallowing difficulty. A new sprinkle, multiparticulate, or alternative dosage form could create a separate commercial opportunity, but it would likely require a new regulatory strategy and substantial bioequivalence work.

5. International excipient harmonization

A formulation using globally accepted excipients can reduce country-specific reformulation. This supports expansion into regulated markets where colorants, gelatin, lactose, or sodium lauryl sulfate may face different labeling or market-access constraints.

How strong is the PHENYTEK patent estate?

The core patent estate is likely weak as a current exclusivity barrier because phenytoin sodium and conventional extended-release capsule technology are longstanding. The stronger assets are operational:

• validated release-control process;
• product-specific dissolution method;
• manufacturing scale-up knowledge;
• supplier qualification;
• stability data;
• pharmacokinetic data;
• regulatory history;
• reliable commercial supply.

Trade secrets covering blending, lubrication, encapsulation, and release specifications may have more practical value than patent filings. These assets can support licensing or contract-manufacturing arrangements even when they do not prevent generic entry.

What patent litigation and settlement risks affect PHENYTEK?

The likelihood of major current litigation is lower than for a recently launched branded drug. Historical or future disputes would most likely concern:

• the scope of any remaining formulation patent;
• ANDA Paragraph IV certification;
• 30-month stay eligibility;
• therapeutic-equivalence coding;
• trademark or trade-dress issues;
• manufacturing-site compliance;
• product withdrawal or shortage-related contracts.

A settlement involving delayed generic entry would require review of the specific patent, timing, consideration exchanged, and antitrust implications under current FTC and court precedent.[5]

Key Takeaways

• PHENYTEK is an extended-release phenytoin sodium capsule available in 100 mg and 200 mg strengths.
• The primary technical risk is maintaining comparable exposure, dissolution, food effect, and dose-dumping performance.
• A reference-like excipient strategy offers the clearest ANDA path.
• Lactose-free and plant-based capsule versions are the most credible excipient-led commercial extensions.
• Core patent protection is unlikely to be the main barrier for a new entrant; regulatory execution and manufacturing reliability are more important.
• Phenytoin is a small molecule, so biosimilar risk does not apply.
• The market is mature and price-sensitive, but supply shortages, limited suppliers, and excipient differentiation can create targeted opportunities.
• Current Orange Book listings and therapeutic-equivalence codes should control any final launch or Paragraph IV assessment.

FAQs About PHENYTEK Excipient and Commercial Strategy

Can PHENYTEK capsules be reformulated without a new FDA approval?

No. A material excipient or release-profile change would require regulatory assessment and could require a new product filing, supplemental approval, or new ANDA, depending on the applicant and the extent of the change.

Is a lactose-free phenytoin extended-release capsule commercially attractive?

Yes, but the opportunity is niche. The main challenge is preserving blend uniformity and pharmacokinetic equivalence after replacing lactose.

Does PHENYTEK face biosimilar competition?

No. Phenytoin sodium is a small-molecule drug. Competitive products would generally proceed through the generic-drug framework rather than the biosimilar pathway.

Is a plant-based capsule shell likely to receive patent protection?

Usually not by itself. A plant-based shell may support branding and market segmentation, but durable patent protection would require a novel, nonobvious composition or manufacturing process.

What is the best entry strategy for a new PHENYTEK competitor?

The strongest strategy is a reference-like extended-release capsule supported by redundant excipient sourcing, robust dissolution control, adequate pharmacokinetic studies, and a commercial plan focused on supply reliability rather than premium pricing.

References

1. U.S. Food and Drug Administration. (n.d.). PHENYTEK- phenytoin sodium capsule, extended release prescribing information.
2. U.S. Food and Drug Administration. (2017). Phenytoin sodium: Product-specific guidance for industry.
3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
4. U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, 21 U.S.C. § 355(j).
5. Federal Trade Commission. (2013). Agreements filed with the Federal Trade Commission under the Medicare Prescription Drug, Improvement, and Modernization Act of 2003.