List of Excipients in Branded Drug PHENYTOIN SODIUM

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Generic Drugs Containing PHENYTOIN SODIUM

Company	Ingredient	NDC	Excipient
Mylan Pharmaceuticals Inc	phenytoin sodium	0378-1560	CELLULOSE, MICROCRYSTALLINE
Mylan Pharmaceuticals Inc	phenytoin sodium	0378-1560	D&C RED NO. 28
Mylan Pharmaceuticals Inc	phenytoin sodium	0378-1560	D&C RED NO. 33

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

# Of NDCs	Excipient
1	AKA3
11	ALCOHOL
1	AMMONIA

Phenytoin Sodium Excipient Strategy and Commercial Opportunities

Last updated: September 24, 2026

Phenytoin sodium is an old, low-cost anticonvulsant with no meaningful active-ingredient patent barrier. Commercial value is concentrated in formulation performance, supply reliability, patient usability, and differentiated delivery systems. The strongest opportunities are alcohol-free pediatric liquids, improved injectable presentations, low-excipient solid dosage forms, and hospital-ready products that reduce preparation and administration risks.

What is the current regulatory and commercial status of phenytoin sodium?

Phenytoin sodium is an established active pharmaceutical ingredient used for seizure treatment and prevention. FDA-approved dosage forms include extended-release capsules, chewable tablets, oral suspension, and injectable products. Dilantin is the reference brand associated with Pfizer, while multiple manufacturers market generic phenytoin sodium products.

Product category	Typical strength	Primary excipient issue	Commercial position
Extended-release capsules	30 mg, 100 mg	Dissolution control, lot-to-lot exposure	Mature generic market
Chewable tablets	50 mg	Taste, tablet robustness, pediatric acceptability	Niche opportunity
Oral suspension	125 mg/5 mL	Sedimentation, redispersibility, microbial control, alcohol content	Differentiation opportunity
Injection	50 mg/mL	High pH, precipitation, tissue injury, administration rate	Hospital and specialty opportunity
Fosphenytoin injection	Equivalent-dose product	Prodrug-specific patent and formulation history	Competing rescue product

Phenytoin has nonlinear pharmacokinetics. Small changes in dose or bioavailability can produce disproportionate changes in plasma concentration, increasing the importance of dissolution, particle size, excipient selection, and manufacturing control. The product label recommends therapeutic drug monitoring, particularly when formulations or dosage regimens change (FDA, 2024a).

The drug also has a narrow therapeutic range. The FDA label identifies total plasma concentrations of approximately 10 to 20 mcg/mL as a commonly used therapeutic range, although clinical interpretation depends on patient factors such as albumin concentration and renal function (FDA, 2024a).

What excipients are used in marketed phenytoin sodium products?

Extended-release capsules

Generic extended-release phenytoin sodium capsules commonly use lactose, sugar, talc, magnesium stearate, gelatin, and colorants, although the exact composition varies by manufacturer. The formulation must maintain extended release while avoiding excessive variability in absorption.

Key formulation variables include:

• API particle size and polymorphic form.
• Drug loading and capsule fill uniformity.
• Granulation method.
• Lubricant concentration.
• Hydrophilic or hydrophobic release-control materials.
• Capsule shell composition.
• Dissolution performance across physiological pH conditions.

Lactose is commercially practical but excludes patients with certain excipient sensitivities and can complicate line extensions positioned as allergen-conscious or low-excipient products. A manufacturer could pursue a lactose-free capsule using microcrystalline cellulose, mannitol, dibasic calcium phosphate, or a combination of fillers. The substitution would require comparative dissolution and bioequivalence work because phenytoin exposure is sensitive to formulation changes.

Chewable tablets

Phenytoin sodium chewable tablets use sweeteners, flavoring agents, binders, disintegrants, lubricants, and colorants. Product acceptability depends heavily on taste masking because phenytoin has a pronounced bitter taste.

Potential excipient systems include:

• Mannitol or isomalt for cooling mouthfeel.
• Sucralose, acesulfame potassium, or steviol glycosides for sweetness.
• Ion-exchange resin complexes for taste masking.
• Coated API particles for reduced immediate bitterness.
• Crospovidone or croscarmellose sodium for rapid dispersion.
• Direct-compression systems for efficient manufacturing.

The main commercial target is pediatric and caregiver use. A more acceptable 50 mg chewable tablet could compete on adherence and administration convenience rather than molecule cost.

Oral suspension

A typical phenytoin suspension must control sedimentation without creating a dense cake that cannot be redispersed. Common excipients can include glycerin, sodium carboxymethylcellulose, polysorbate 80, saccharin sodium, flavoring agents, and alcohol, depending on the product (DailyMed, 2024a).

The principal excipient challenges are:

1. Maintaining uniform dose delivery after storage.
2. Preventing crystal growth or particle aggregation.
3. Controlling viscosity without making the product difficult to pour.
4. Preserving the product during repeated bottle opening.
5. Improving taste without increasing sugar or alcohol exposure.

A commercial formulation should be evaluated for delivered dose after shaking, dose withdrawal at the beginning and end of bottle use, sedimentation rate, redispersibility, and microbial robustness. Oral syringes are preferable to household spoons because dose accuracy is especially important for a narrow-therapeutic-index drug.

What excipient strategies offer the strongest commercial opportunity?

Alcohol-free pediatric suspension

Alcohol-free phenytoin suspension is the clearest excipient-led opportunity. A formulation could replace alcohol with a combination of glycerin, propylene glycol, polyethylene glycol, or a structured suspending system, subject to pediatric exposure limits and product-specific tolerability.

A differentiated product would combine:

• Alcohol-free composition.
• Low or no sucrose.
• Improved bitterness control.
• Oral-syringe-compatible viscosity.
• Clear shake instructions.
• Tamper-evident packaging.
• Dose-marked syringe.
• Stability after repeated opening.

The product could target children, patients with alcohol restrictions, institutional care, and pharmacies seeking simplified counseling. The main technical risk is maintaining suspension uniformity without excessive viscosity or unacceptable mouthfeel.

Sugar-free and low-sugar formulations

Sugar-free formulations could address dental health, diabetes management, and long-term pediatric use. Polyols such as sorbitol, mannitol, and xylitol require careful gastrointestinal tolerability assessment. High polyol loads can cause bloating or diarrhea, which may undermine adherence.

A practical strategy is a low-sugar or sugar-free formulation using a blend of a bulk sweetener, high-intensity sweetener, flavor modifier, and viscosity-control polymer. Taste masking should be tested against the actual phenytoin concentration because bitterness can increase nonlinearly with dose.

Improved injectable formulation

Marketed phenytoin sodium injection is highly alkaline and contains a substantial amount of organic solvent. A commonly marketed presentation contains 50 mg/mL phenytoin sodium with approximately 40% propylene glycol and 10% alcohol; sodium hydroxide is used to adjust pH (DailyMed, 2024b).

This composition creates several commercial and clinical problems:

• Risk of precipitation after dilution.
• Administration through a large vein or central access in some settings.
• Infusion-rate restrictions.
• Local tissue injury and purple-glove syndrome.
• Compatibility constraints.
• Need for close monitoring during administration.
• Solvent exposure in vulnerable patients.

A new phenytoin sodium injection would face a difficult technical problem: phenytoin sodium has limited aqueous solubility, while reducing solvent or pH can trigger precipitation. Possible approaches include cyclodextrin complexation, alternative cosolvent systems, nanodispersion, lipid-based delivery, or a ready-to-dilute concentrate. Each approach would require extensive compatibility, extractables and leachables, particulate, stability, and toxicology work.

In practice, fosphenytoin is the strongest existing competitor for improved parenteral use. Fosphenytoin is a water-soluble prodrug designed to avoid several administration limitations associated with phenytoin sodium. A new phenytoin sodium product must therefore offer a measurable advantage in cost, availability, dosing convenience, or clinical workflow.

Ready-to-use hospital presentation

A pharmacy-ready product could package phenytoin sodium injection in a premixed or standardized dilution format. Potential benefits include fewer preparation steps, reduced medication errors, and better emergency-department workflow.

The product would need validated stability in the final container, documented compatibility with infusion materials, controls for precipitation, and clear restrictions on dilution and infusion rate. Container selection is important because phenytoin formulations can interact with plastics and tubing materials.

What formulation patents protect phenytoin sodium products?

Phenytoin sodium is an old active ingredient, and the core compound, salt, and conventional dosage forms are outside normal patent life. The commercial landscape is therefore different from a newly approved small molecule.

IP category	Current commercial significance
Core phenytoin compound	No meaningful blocking patent position
Phenytoin sodium salt	Historical protection expired
Conventional capsules	Generally vulnerable to generic competition
Conventional suspension	Potential for formulation patents, but difficult to enforce broadly
Improved injectable delivery	Potentially patentable if technically novel and non-obvious
Taste-masked pediatric product	Potential composition and process protection
Device and packaging	Potential utility or design protection
Fosphenytoin	Separate prodrug and formulation estate

A sponsor pursuing a new product should focus on narrow, defensible claims covering a defined excipient range, particle-size distribution, dissolution profile, stability result, container system, or manufacturing process. Broad claims covering routine use of common suspending agents or sweeteners would face significant obviousness and enablement risk.

No current Orange Book patent barrier is expected to prevent generic phenytoin sodium capsules, chewable tablets, oral suspension, or conventional injection. FDA’s Orange Book identifies reference products and therapeutic-equivalence information, but old phenytoin products generally compete through abbreviated new drug applications rather than active patent exclusivity (FDA, 2024b).

When does phenytoin sodium lose exclusivity?

Phenytoin sodium lost meaningful market exclusivity decades ago. It does not have the commercial profile of a product approaching generic entry. The relevant regulatory barriers are abbreviated application requirements, product-specific bioequivalence, manufacturing controls, and supply reliability.

Exclusivity or barrier	Status
New chemical entity exclusivity	Expired
Core compound patent	Expired
Conventional formulation patents	Generally expired or commercially weak
Orange Book patent litigation	Limited current relevance
Pediatric exclusivity	Not a current market barrier
Generic substitution	Established for multiple presentations
Biosimilar pathway	Not applicable

Paragraph IV challenges remain legally possible when a generic applicant certifies that listed patents are invalid, unenforceable, or not infringed. For conventional phenytoin sodium products, the more relevant pathway is often a paragraph III or non-patent certification because the commercial product may have no active blocking patents listed against the reference product.

What FDA regulatory issues affect phenytoin sodium excipient development?

The main regulatory issue is not approval of the active ingredient. It is demonstrating that excipient changes do not alter exposure or clinical performance.

Oral products

An abbreviated application for a modified generic formulation may require:

• Comparative dissolution across multiple pH conditions.
• Fed and fasting bioequivalence, where applicable.
• Comparative stability.
• In vitro alcohol dose-dumping assessment for extended-release products.
• Demonstration of capsule or tablet content uniformity.
• Evaluation of excipient-related safety.
• Labeling for administration instructions and therapeutic monitoring.

Because phenytoin shows nonlinear pharmacokinetics, conventional average bioequivalence results may require careful interpretation. Small differences in systemic exposure can have clinical consequences.

Injectable products

Injectable development requires particular attention to:

• Particulate matter.
• Sterility and endotoxin.
• pH and osmolality.
• Precipitation during dilution.
• Container closure integrity.
• Infusion-set compatibility.
• In-use stability.
• Local tolerance.
• Administration rate.
• Extractables and leachables.

A formulation with lower solvent content may create a stronger clinical proposition, but it also increases the risk of precipitation and short shelf life.

Which companies are competing in phenytoin sodium?

Competition is fragmented across generic manufacturers and branded or authorized-generic channels. Product availability can change with manufacturing decisions, supply shortages, and discontinuations.

The relevant competitive groups are:

• Pfizer and products associated with Dilantin.
• Generic capsule manufacturers.
• Generic oral-suspension manufacturers.
• Hospital injectable suppliers.
• Manufacturers of fosphenytoin products.
• Contract manufacturers with controlled-release and sterile injectable capabilities.

The commercial market is price-sensitive for capsules and tablets. Injectable products can support better margins because hospitals value continuity of supply, validated compatibility, and reduced preparation burden. Pediatric suspensions can also support differentiated pricing if the product solves taste, alcohol, sugar, or dose-accuracy problems.

What generic entry risks exist for a new phenytoin formulation?

A new formulation faces five principal risks.

First, the active ingredient is inexpensive and widely available. Cost-based competitors can undercut premium pricing.

Second, a formulation patent may be narrow. A competitor can alter polymer grade, sweetener, particle size, or packaging while maintaining similar clinical performance.

Third, bioequivalence can be difficult because phenytoin exposure is nonlinear and formulation-dependent.

Fourth, prescribers and pharmacists may be reluctant to switch stable patients because therapeutic drug monitoring is already part of phenytoin management.

Fifth, hospital products compete against fosphenytoin, which may provide a stronger safety and administration proposition than a reformulated phenytoin sodium injection.

How strong is the patent estate for phenytoin sodium?

The core patent estate is weak because the molecule and conventional dosage forms are old. A commercially relevant new estate would need to be built around formulation-specific evidence.

The strongest potential claim areas are:

• A defined alcohol-free suspension with demonstrated redispersibility.
• A taste-masked particle or resin complex.
• A low-solvent injectable composition that prevents precipitation.
• A stable premixed infusion product.
• A specific controlled-release matrix with a reproducible dissolution profile.
• A package and dosing system that improves delivered-dose accuracy.
• A manufacturing process that controls phenytoin particle size or polymorph.

Manufacturing know-how may provide more practical protection than patents. Critical process parameters include API milling, wetting, dispersion energy, homogenization, polymer hydration, filling temperature, and sterilization conditions.

What licensing deals and partnerships are commercially relevant?

The highest-value partnership targets are not conventional molecule licensors. They are excipient, delivery, packaging, and sterile-manufacturing partners.

Potential collaboration models include:

• Licensing an ion-exchange taste-masking platform.
• Co-developing an alcohol-free pediatric suspension with a specialty pharmaceutical company.
• Using a cyclodextrin or nanodispersion platform for injectable development.
• Contracting a sterile manufacturer with validated high-pH product experience.
• Partnering with a hospital supplier for premixed emergency products.
• Licensing an oral-syringe and bottle system designed for suspension uniformity.

No current transaction is required to justify the commercial strategy. The most defensible value would come from a formulation platform that can be applied to other narrow-therapeutic-index drugs, not from phenytoin sodium alone.

What is the best commercial strategy for phenytoin sodium?

A staged strategy is most rational:

1. Launch an alcohol-free, low-sugar oral suspension with validated dose uniformity.
2. Add an improved pediatric flavor and oral-syringe presentation.
3. Develop a lactose-free extended-release capsule only if a clear substitution or supply advantage exists.
4. Evaluate a ready-to-use injectable or low-solvent product after technical feasibility work.
5. Protect the product through formulation, process, packaging, and device claims.
6. Build manufacturing redundancy because shortages can create more value than marginal formulation differences.

The most attractive near-term opportunity is the pediatric suspension. The most technically valuable opportunity is the injectable reformulation. The capsule market is the easiest to enter but the hardest to differentiate profitably.

Key Takeaways

• Phenytoin sodium has no meaningful core patent or exclusivity barrier.
• Commercial value depends on excipient performance, reliability, and administration convenience.
• Alcohol-free, low-sugar pediatric suspension is the clearest near-term opportunity.
• Taste masking, suspension redispersibility, and oral-syringe dosing are high-value development targets.
• Conventional capsules are mature and price-sensitive.
• Injectable reformulation offers differentiation but faces substantial precipitation, compatibility, and clinical risks.
• Fosphenytoin is the main competing strategy for safer parenteral administration.
• Formulation patents must be narrow, data-supported, and linked to measurable performance.
• Manufacturing controls and supply reliability may provide greater practical advantage than broad composition claims.
• Biosimilar risk does not apply because phenytoin sodium is a small-molecule drug, not a biologic.

FAQs

Is phenytoin sodium a biologic eligible for biosimilar competition?

No. Phenytoin sodium is a synthetic small-molecule drug. Competition occurs through generic drug applications, not the FDA biosimilar pathway.

Can a company patent an alcohol-free phenytoin suspension?

Yes, but patent strength would depend on the specific excipient ranges, stability results, redispersibility, taste-masking system, and demonstrated technical effect. A generic claim that merely removes alcohol would face substantial patentability risk.

Why is phenytoin sodium injection difficult to reformulate?

The drug has limited aqueous solubility. Existing injection products use alkaline conditions and organic solvents to maintain solubility. Reducing solvent or pH can cause precipitation during storage or dilution.

Does a new phenytoin suspension require clinical trials?

The regulatory requirement depends on the formulation and application pathway. Comparative dissolution, bioequivalence, stability, excipient safety, and product-specific studies are typically central. A materially different delivery system may require more extensive clinical evidence.

Is fosphenytoin a substitute for phenytoin sodium?

Fosphenytoin is a prodrug that can provide a more practical parenteral administration option. It is not a direct substitute in every commercial setting because dose conversion, cost, clinical protocols, and product availability differ.

References

1. DailyMed. (2024a). Dilantin-125 phenytoin suspension prescribing information. U.S. National Library of Medicine.

2. DailyMed. (2024b). Phenytoin sodium injection prescribing information. U.S. National Library of Medicine.

3. U.S. Food and Drug Administration. (2024a). Dilantin extended phenytoin sodium capsules prescribing information. FDA.

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

5. U.S. Food and Drug Administration. (2024c). Phenytoin sodium products and abbreviated new drug application guidance materials. FDA.