List of Excipients in Branded Drug DILANTIN-125

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Parke-Davis Div of Pfizer Inc	DILANTIN-125	phenytoin	0071-2214	ALCOHOL
Parke-Davis Div of Pfizer Inc	DILANTIN-125	phenytoin	0071-2214	ANHYDROUS CITRIC ACID
Parke-Davis Div of Pfizer Inc	DILANTIN-125	phenytoin	0071-2214	CARBOXYMETHYLCELLULOSE SODIUM
Parke-Davis Div of Pfizer Inc	DILANTIN-125	phenytoin	0071-2214	FD&C YELLOW NO. 6

DILANTIN-125 Excipient Strategy and Commercial Opportunities

Last updated: August 5, 2026

DILANTIN-125 is a phenytoin oral suspension containing 125 mg of phenytoin per 5 mL. Its commercial opportunity is primarily generic substitution and differentiated liquid delivery, not originator patent exclusivity. The strongest product-development targets are dose uniformity, redispersibility, microbial protection, sugar reduction, alcohol reduction or elimination, palatability, and dosing-device accuracy.

What is DILANTIN-125 and how is it formulated?

DILANTIN-125 is an immediate-release oral suspension for seizure control. The product contains phenytoin in a liquid suspension vehicle rather than as a fully dissolved solution. The formulation is designed for oral administration where patients may have difficulty swallowing capsules or tablets.

The labeled inactive ingredients include:

Excipient or component	Likely formulation function
Sucrose	Sweetener, viscosity and mouthfeel modifier
Glycerin	Humectant, cosolvent and viscosity modifier
Polysorbate 80	Wetting and dispersion aid
Sodium benzoate	Preservative
Citric acid	pH adjustment
Sodium citrate	Buffering capacity
Flavoring agents	Palatability
Purified water	Vehicle
Alcohol, at a low concentration where specified in the product labeling	Cosolvent and preservation support

The exact current composition should be controlled against the applicable FDA labeling and manufacturing specification because inactive-ingredient declarations can change by manufacturing site or approved supplement. FDA labeling identifies DILANTIN-125 as a phenytoin oral suspension with 125 mg per 5 mL [1].

Phenytoin is poorly water-soluble and has nonlinear pharmacokinetics. These properties make particle size, wetting, suspension stability, dose withdrawal and gastrointestinal availability commercially important. An excipient change can affect exposure even when the active ingredient and labeled strength remain unchanged.

What patents protect DILANTIN-125?

DILANTIN-125 does not present a material current patent barrier to generic oral-suspension development based on its FDA Orange Book record. The original product and historical formulation rights are outside the normal term of U.S. patent protection. The Orange Book record for the product does not identify an unexpired patent or regulatory exclusivity block that prevents ANDA competition [2].

Patent and exclusivity position

Issue	DILANTIN-125 position
Active ingredient	Phenytoin
Dosage form	Oral suspension
Strength	125 mg/5 mL
FDA pathway	Original NDA product with generic ANDA pathway
Listed patent barrier	No material unexpired Orange Book barrier identified
New chemical entity exclusivity	Expired
Pediatric exclusivity	No current blocking period identified
Biosimilar exclusivity	Not applicable
Primary competitive barrier	Formulation performance, manufacturing control and commercial execution

The absence of an Orange Book patent does not eliminate the possibility of non-Orange-Book intellectual property. A competitor could pursue patents covering a specific particle-size distribution, suspension vehicle, preservative system, taste-masking system, device, packaging configuration or manufacturing process. Those rights would need to satisfy novelty, nonobviousness and written-description requirements and would not automatically block a conventional phenytoin suspension.

When does DILANTIN-125 lose exclusivity?

DILANTIN-125 has already lost the practical exclusivity associated with its original approval. The product is exposed to generic competition through ANDA filings, subject to FDA approval and applicable product-specific bioequivalence requirements.

Generic entry is not dependent on a new clinical efficacy program. An ANDA applicant generally must demonstrate pharmaceutical equivalence, bioequivalence, quality and manufacturing compliance against the reference listed drug. The applicant must also address the reference product’s labeling, dosage form and strength under the Hatch-Waxman framework [3].

Generic entry timeline

Stage	Commercial implication
Reference listed drug identification	Determines the product used for ANDA comparison
ANDA formulation development	Applicant matches strength, dosage form and performance
In vitro characterization	Particle size, assay, content uniformity and redispersibility become important
Bioequivalence program	Phenytoin’s narrow therapeutic index and nonlinear exposure increase execution risk
FDA review	Deficiencies may concern formulation, controls, stability or comparative performance
Approval	Product can enter subject to applicable certifications and litigation status
Commercial launch	Price, pharmacy substitution, supply reliability and patient acceptance determine share

What excipients are most important in a phenytoin suspension?

The highest-value excipient work concerns physical stability rather than simple solubility enhancement.

Suspending and wetting system

Polysorbate 80 can improve wetting of hydrophobic phenytoin particles. A substitute surfactant may reduce oxidation or regulatory complexity, but the replacement must preserve particle dispersion and avoid excessive foaming.

A structured suspending system may use a polymeric thickener, colloidal material or other rheology modifier. The objective is controlled sedimentation with rapid redispersion. Excessive viscosity can impair pouring, syringe withdrawal and dose accuracy. Low viscosity can produce hard cake formation and nonuniform dosing after storage.

Buffer and pH control

Citric acid and sodium citrate provide pH control. The formulation must balance chemical stability, preservative activity, taste and the physical behavior of phenytoin particles. A higher pH may alter apparent solubility, but partial dissolution followed by precipitation can create particle-growth and dose-uniformity problems.

A differentiated product should characterize:

• pH over shelf life
• particle-size distribution
• crystal habit and polymorphic state
• sedimentation volume
• redispersibility after defined storage stress
• delivered dose at the beginning, middle and end of the container
• assay after repeated opening

Preservative system

Sodium benzoate supports microbiological protection in a multidose liquid. A preservative-free product could appeal to pediatric, chronic-use or excipient-sensitive populations, but it would require a robust package, microbial-control strategy and preservative-free stability rationale.

Potential alternatives include potassium sorbate, benzoate systems at adjusted pH, or packaging that limits microbial ingress. Each change affects taste, regulatory justification and antimicrobial effectiveness testing under USP requirements [4].

Sugar and alcohol reduction

Sucrose improves sweetness and mouthfeel but creates a commercial limitation for patients with diabetes, dental concerns or dietary restrictions. A sugar-reduced or sugar-free formulation could use sucralose, saccharin, acesulfame potassium, polyols or a combination of high-intensity sweeteners.

Glycerin can support mouthfeel and viscosity, but high levels may produce a heavy sensory profile and gastrointestinal intolerance. A lower-alcohol or alcohol-free formulation could broaden use in children and institutions. The excipient replacement must preserve wetting, microbiological quality and stability.

What formulation patents could protect a new DILANTIN-125 competitor?

The most defensible patent opportunities would require a measurable technical distinction from a conventional phenytoin suspension.

Potential formulation patent clusters

Patent cluster	Potential claim focus	Commercial value
Redispersible suspension	Defined sedimentation and redispersion limits	Reduces dose variability
Particle engineering	Narrow particle-size distribution or controlled morphology	Improves uniformity and dissolution behavior
Sugar-free vehicle	Specific sweetener, buffer and rheology system	Expands patient and institutional use
Alcohol-free product	Preservative and wetting system without ethanol	Supports pediatric positioning
Taste masking	Coating, ion pairing or flavor system	Improves adherence
Unit-dose packaging	Sachet, cup or prefilled oral syringe	Reduces contamination and dosing errors
Device integration	Calibrated syringe or bottle adapter	Supports accurate administration
Stability system	Reduced particle growth and improved shelf life	Lowers waste and supply risk

A broad claim to "phenytoin suspension with excipients" would face substantial prior-art risk. Stronger claims would define composition ranges together with performance parameters, such as redispersion time, dose uniformity, particle-size limits, dissolution profile or stability after temperature cycling.

How does DILANTIN-125 compare with phenytoin capsules and tablets?

The liquid suspension has a different commercial role from solid oral phenytoin products.

Attribute	DILANTIN-125 suspension	Phenytoin capsules or tablets
Primary user benefit	Swallowing flexibility and liquid administration	Convenience and portability
Dose flexibility	High, when the device is accurate	Lower, constrained by unit strength
Dose-uniformity risk	Sedimentation and shaking errors	Unit-dose manufacturing controls
Excipient opportunity	High	Moderate
Packaging risk	Leakage, contamination and dosing-device mismatch	Blister or bottle stability
Patient population	Pediatrics, dysphagia, tube-feeding and dose titration	Patients able to swallow solid dosage forms
Commercial differentiation	Taste, device and suspension performance	Capsule shell, release profile and size

Phenytoin products cannot be treated as interchangeable solely because they contain the same active ingredient. Differences in formulation and dosage form can affect absorption. FDA labeling also warns that phenytoin dosage changes and product changes require clinical attention because of its narrow therapeutic range and nonlinear pharmacokinetics [1].

What FDA regulatory pathway applies to a new phenytoin suspension?

A conventional generic suspension would generally use an ANDA referencing the applicable reference listed drug. A materially different product may require a 505(b)(2) application if the sponsor relies partly on FDA findings for phenytoin but introduces a formulation, dosage device, excipient system or indication that falls outside the standard ANDA framework [3].

Key FDA development requirements

The development package should address:

1. Pharmaceutical equivalence and labeled strength.
2. Assay, impurities and degradation products.
3. Particle-size distribution and morphology.
4. Redispersion and delivered-dose uniformity.
5. Microbial limits and preservative effectiveness.
6. Container-closure integrity.
7. Stability under long-term and accelerated conditions.
8. Comparative dissolution or in vitro performance.
9. Clinical or pharmacokinetic bioequivalence where required.
10. Compatibility with oral syringes, enteral tubes and dosing cups.

Phenytoin’s narrow therapeutic index increases the importance of exposure comparability. A sponsor should not assume that an apparently minor change in surfactant, viscosity, particle size or pH is clinically neutral.

Are there Paragraph IV challenges to DILANTIN-125?

There is no current originator patent block identified in the Orange Book record that would create a conventional Paragraph IV challenge target for DILANTIN-125. Paragraph IV litigation is therefore less likely to determine market entry than ANDA review, product-specific bioequivalence, manufacturing readiness and commercial contracting [2,3].

A Paragraph IV certification could become relevant if a later patent were listed for a reformulated reference product or if a patent owner obtained listing eligibility for a qualifying formulation or method-of-use patent. That is not the present principal risk for the legacy DILANTIN-125 product.

What patent litigation and settlement agreements affect DILANTIN-125?

No material active patent litigation or settlement agreement is identified as a current barrier to generic DILANTIN-125 entry. Historical disputes involving phenytoin products may remain relevant to prior-art analysis, but they do not create current commercial exclusivity without an enforceable, unexpired right.

The more relevant legal issues are:

• Paragraph IV certification strategy.
• Non-Orange-Book formulation patents.
• Trade-secret protection for suspension processing.
• Contract manufacturing and supply agreements.
• Trademark and trade-dress restrictions.
• State substitution rules and authorized-generic arrangements.

Which companies are challenging DILANTIN-125?

Generic pharmaceutical companies with oral-liquid manufacturing capabilities are the natural challengers. The competitive field includes large ANDA manufacturers, specialty generic companies and contract development and manufacturing organizations with suspension expertise.

The market is likely to favor suppliers that can provide:

• Reliable phenytoin particle control.
• High batch-to-batch dose uniformity.
• Stable preservative performance.
• Child-resistant packaging with an accurate oral syringe.
• Consistent flavor and low sensory variability.
• Supply continuity for hospitals and long-term-care providers.

Public FDA approval records, current ANDA approvals and commercial availability determine the active competitor set. A patent-rights analysis alone does not identify which approved generic products are actually selling.

What licensing deals and manufacturing opportunities exist?

The most attractive licensing opportunities are technology-based rather than molecule-based. Phenytoin is an old active ingredient, so value is more likely to arise from delivery and manufacturing technology.

Potential transaction structures include:

Opportunity	Possible partner
Sugar-free suspension platform	Pediatric or specialty generic company
Oral-syringe and bottle-adapter system	Device manufacturer
Improved wetting and redispersion technology	Formulation technology company
Alcohol-free preservative system	Excipient or specialty-vehicle supplier
Regional manufacturing rights	Local generic pharmaceutical company
Hospital and institutional supply	Contract manufacturer or distributor
Co-development of pediatric liquid	Branded-generic or specialty pharmaceutical company

Manufacturing barriers include control of phenytoin particle properties, prevention of agglomeration, reproducible suspension viscosity, microbial control and validated fill-volume accuracy. These barriers are operational rather than patent-based, but they can delay launch and impair product reliability.

What is the geographic commercial opportunity?

The United States offers a mature generic market with limited molecule-level exclusivity and potentially strong demand for dependable liquid supply. European and other regulated markets may use different reference products, strengths, excipient restrictions and device requirements. A formulation accepted in the United States may require region-specific technical documentation.

Geographic differentiation may focus on:

• Sugar-free or alcohol-free labeling.
• Pediatric dosing devices.
• Unit-dose packaging.
• Tube-administration compatibility.
• Local preservative restrictions.
• Cold-chain avoidance.
• Hospital procurement and shortage resilience.

The commercial opportunity is strongest where liquid phenytoin is clinically needed but supplier reliability is poor. A low-price generic without a differentiated device or supply proposition is likely to face rapid commoditization.

How strong is the DILANTIN-125 patent estate?

The legacy patent estate is weak as a current exclusivity mechanism. Its commercial defensibility is low at the active-ingredient level and modest at the product level unless a new entrant develops protectable formulation or device technology.

Estate component	Relative strength
Phenytoin molecule	Very low
Conventional oral suspension	Low
Standard preservative system	Low
Sugar-free differentiated vehicle	Moderate if technically narrow
Particle-engineered suspension	Moderate to high if performance is unexpected
Integrated dosing device	Moderate
Manufacturing process	Moderate, with trade-secret value
Brand and distribution	Moderate, depending on channel access

What generic launch scenarios exist for DILANTIN-125?

Three launch scenarios are commercially plausible:

Price-led generic launch

A conventional suspension enters at a discount and competes through pharmacy substitution. This strategy requires low manufacturing cost and dependable supply but offers limited long-term margin protection.

Differentiated liquid launch

A sugar-free, alcohol-free or improved-taste product targets pediatric, institutional and dysphagia populations. The sponsor can support a premium through patient usability and reduced dosing error.

Device-led launch

A product combines the suspension with a calibrated oral syringe, bottle adapter or unit-dose package. The device can improve adherence and reduce administration errors, although device qualification and packaging cost increase.

Key Takeaways

• DILANTIN-125 is a 125 mg/5 mL phenytoin oral suspension.
• Its original exclusivity has expired, and no material current Orange Book patent barrier is identified.
• The principal opportunity is generic or reformulated competition, not molecule-level patent licensing.
• Excipient priorities are wetting, sedimentation control, redispersibility, preservative performance, taste and dose accuracy.
• Sugar-free, alcohol-free and device-integrated products offer the clearest differentiation.
• Phenytoin’s nonlinear pharmacokinetics and narrow therapeutic index make formulation changes commercially and regulatorily sensitive.
• New patent value would likely depend on defined composition ranges linked to measurable performance results.
• Manufacturing execution, supply reliability and institutional distribution are more important than legacy patent rights.

FAQs

Can DILANTIN-125 be reformulated without conducting new clinical trials?

A conventional ANDA may avoid a full clinical efficacy program, but the sponsor must satisfy FDA bioequivalence and quality requirements. A material formulation change may require additional pharmacokinetic, in vitro or clinical support.

Is a sugar-free phenytoin suspension commercially attractive?

Yes. It could address pediatric, diabetic, dental-health and institutional-use preferences. Its value depends on acceptable taste, preservative performance, stability and dose uniformity.

Can phenytoin suspension be administered through an enteral feeding tube?

Administration may be feasible, but tube compatibility, adsorption, flushing volume and delivered-dose recovery require product-specific validation. The label and institutional protocols control use.

Does DILANTIN-125 have biosimilar competition?

No. Phenytoin is a small-molecule drug. Competition proceeds through generic-drug pathways rather than the FDA biosimilar pathway.

What is the best patent strategy for a new phenytoin liquid?

The strongest strategy would combine a narrowly defined excipient system with objective performance limits, such as rapid redispersion, controlled particle growth, improved dose uniformity or validated stability under stress.

References

1. Pfizer Inc. (2023). DILANTIN-125 phenytoin suspension: U.S. prescribing information. U.S. Food and Drug Administration labeling database.

2. U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

3. U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions: Content and format. FDA.

4. United States Pharmacopeia. (2024). General chapter <51>: Antimicrobial effectiveness testing. United States Pharmacopeial Convention.