List of Excipients in Branded Drug AMANTADINE HYDROCHLORIDE

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Generic Drugs Containing AMANTADINE HYDROCHLORIDE

Company	Ingredient	NDC	Excipient
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	ANHYDROUS CITRIC ACID
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	METHYLPARABEN
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	PROPYLENE GLYCOL
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	PROPYLPARABEN
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	SODIUM HYDROXIDE
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	SORBITOL
PAI Holdings LLC dba PAI Pharma	amantadine hydrochloride	0121-0646	WATER

What are the Most Frequently-Used Excipients in AMANTADINE HYDROCHLORIDE?

# Of NDCs	Excipient
1	1,4-SORBITAN
11	ALCOHOL
7	ALUMINUM OXIDE
17	AMMONIA
11	ANHYDROUS CITRIC ACID
1	BENZOIC ACID
13	BUTYL ALCOHOL

Amantadine Hydrochloride Excipient Strategy and Commercial Opportunities

Last updated: October 21, 2026

Amantadine hydrochloride is an established small-molecule API with limited composition-of-matter protection and substantial formulation opportunity. Immediate-release tablets and capsules are mature generic products. Commercial value is concentrated in extended-release systems, dyskinesia-focused dosing, abuse-resistant delivery, pediatric or geriatric dosage forms, and manufacturing platforms that improve release control, stability, or patient adherence.

The strongest current product differentiation is in modified-release products such as Gocovri and Osmolex ER. Excipient selection is central to their commercial positioning because release rate, food effect, dose proportionality, capsule or tablet size, and once-daily performance determine whether a product can compete against low-cost immediate-release amantadine.

What is the FDA regulatory status of amantadine hydrochloride?

Amantadine hydrochloride is FDA-approved in multiple dosage forms and indications, including Parkinson's disease and drug-induced extrapyramidal reactions. The extended-release products Gocovri and Osmolex ER added Parkinson's-related formulations with differentiated release profiles.

Product	Active ingredient	Dosage form	Strengths	Principal FDA-approved use
Generic amantadine	Amantadine hydrochloride	Tablets and capsules	Commonly 100 mg	Parkinson's disease and drug-induced extrapyramidal reactions
Gocovri	Amantadine hydrochloride	Extended-release capsules	68.5 mg, 137 mg	Dyskinesia associated with Parkinson's disease; adjunctive use with levodopa-based therapy
Osmolex ER	Amantadine hydrochloride	Extended-release tablets	129 mg, 193 mg, 258 mg	Parkinson's disease and drug-induced extrapyramidal reactions

Gocovri was approved in 2017. Osmolex ER was approved in 2018. FDA labeling identifies both as extended-release products with distinct dosing and release characteristics rather than simple line extensions of immediate-release amantadine.[1,2]

Amantadine is a small molecule, not a biologic. Biosimilar competition is therefore irrelevant. Competition occurs through abbreviated new drug applications, 505(b)(2) applications, reformulations, and authorized or licensed products.

What excipients are used in amantadine hydrochloride products?

Immediate-release amantadine products generally use conventional tablet and capsule excipients. Extended-release products use polymer matrices, coatings, osmotic systems, or multiparticulate technologies to control delivery.

Immediate-release excipient platform

Typical excipients in generic amantadine hydrochloride tablets and capsules include:

• Lactose monohydrate
• Microcrystalline cellulose
• Pregelatinized starch or maize starch
• Povidone
• Crospovidone or croscarmellose sodium
• Colloidal silicon dioxide
• Talc
• Magnesium stearate
• Gelatin for hard capsules
• Titanium dioxide and approved capsule colorants

The commercial objective for immediate-release products is cost, supply reliability, compressibility, capsule fill performance, and regulatory simplicity. A formulation with fewer excipients and a well-established inactive-ingredient precedent can reduce development and review risk.

Excipients should be screened for compatibility with the hydrochloride salt. Key risks include moisture uptake, electrostatic behavior during capsule filling, powder segregation, and altered dissolution from excessive hydrophobic lubricant.

Gocovri excipient strategy

Gocovri uses extended-release capsules containing a polymer-based release system. FDA labeling identifies excipients including ammonium methacrylate copolymer, hypromellose, microcrystalline cellulose, lactose monohydrate, povidone, croscarmellose sodium, colloidal silicon dioxide, magnesium stearate, talc, triethyl citrate, titanium dioxide, gelatin, and colorants.[1]

The formulation strategy combines:

• A release-controlling polymer system
• Hydrophilic matrix and capsule-fill components
• Plasticization through triethyl citrate
• Flow and lubrication aids
• Conventional capsule-shell materials

Gocovri's commercial differentiation is primarily the once-daily extended-release profile and its indication for levodopa-associated dyskinesia. The excipient system supports a formulation patent estate and a product profile that is more difficult to reproduce than an immediate-release capsule.

Osmolex ER excipient strategy

Osmolex ER is an extended-release tablet. Its product design uses an oral controlled-release platform rather than a conventional immediate-release matrix. FDA labeling identifies excipients that include polymeric film-coating and tableting components, with the precise formulation defined in the approved product labeling and regulatory filings.[2]

An extended-release tablet may offer manufacturing advantages over a multiparticulate capsule, including:

• High-speed compression
• Lower packaging complexity
• No gelatin shell
• Potentially lower unit cost
• More efficient automated inspection and coating

The tradeoff is that tablet performance depends heavily on compression force, coating weight gain, core porosity, polymer viscosity, and dissolution robustness across pH conditions.

Which excipient technologies offer the strongest commercial opportunities?

The most attractive opportunities are not basic excipient substitutions. They are formulation platforms that solve a defined commercial problem.

Opportunity	Relevant excipient strategy	Commercial rationale
Once-daily extended release	Hypromellose, ammonium methacrylate copolymers, ethylcellulose, osmotic polymers	Reduces dosing frequency and differentiates from generic immediate-release products
Sprinkleable capsules	Multiparticulate pellets with polymer coatings	Supports patients with dysphagia and avoids tablet swallowing barriers
Low-dose titration	Dilution-capable granules, mini-tablets, scored matrices	Enables gradual initiation and dose adjustment
Pediatric formulation	Taste-masked granules, oral suspension, dispersible mini-tablets	Expands use where swallowing and palatability limit capsules or tablets
Geriatric formulation	Smaller tablets, capsules, or orally disintegrating systems	Addresses Parkinson's disease patients with dysphagia
Alcohol-resistant release	Robust polymer matrix or osmotic design	Reduces dose-dumping risk and improves product quality
Gluten-, lactose-, or gelatin-free products	Alternative fillers, binders, and capsule shells	Expands market access and simplifies patient restrictions
Stable liquid formulation	Buffer, preservative, viscosity modifier, and suspension stabilizer	Creates a 505(b)(2) or specialty-generic opportunity
Cost-reduced modified release	Lower-cost polymer and coating process	Targets payer-sensitive markets without copying a proprietary excipient system exactly

What formulations are protected by amantadine hydrochloride patents?

Patent protection for amantadine hydrochloride is concentrated in formulation, dosing, and method-of-use claims. The active ingredient itself has been marketed for decades and does not provide meaningful new-molecule exclusivity.

Gocovri patent strategy

Gocovri's patent position is associated with extended-release amantadine formulations and their use in Parkinson's disease dyskinesia. The relevant claim categories may include:

• Extended-release capsules containing specified amantadine doses
• Release profiles over defined dissolution intervals
• Once-daily administration
• Treatment of dyskinesia associated with levodopa therapy
• Combination use with dopaminergic therapy
• Pharmacokinetic exposure parameters

The commercial strength of this estate depends on whether a competing product can use a different polymer system, different dosage form, different release profile, or different dosing regimen while still obtaining FDA approval for the same clinical use.

Osmolex ER patent strategy

Osmolex ER protection is associated with extended-release tablet technology and the administration of amantadine for Parkinson's disease and drug-induced extrapyramidal reactions. Its potential claim categories include:

• Controlled-release tablets
• Osmotic or matrix-based delivery
• Dose strengths and release characteristics
• Methods of treating Parkinson's disease
• Methods of treating drug-induced extrapyramidal symptoms

A competing manufacturer may avoid particular formulation claims by using a different release-control mechanism. That strategy would require comparative dissolution, pharmacokinetic, stability, and potentially clinical data.

Orange Book status and patent verification

The FDA Orange Book is the controlling source for currently listed patents, expiration dates, pediatric exclusivity, and any patent-use codes. Listings can change through patent expiration, delisting, corrections, litigation outcomes, and regulatory updates.[3]

For transaction or launch decisions, the relevant review should distinguish:

1. Listed formulation patents.
2. Listed method-of-use patents.
3. Unlisted manufacturing or know-how rights.
4. Non-patent regulatory exclusivity.
5. Patents covering only a specific indication or dosing regimen.

A formulation patent that does not cover the proposed generic's dosage form or release mechanism may present limited launch risk.

When does amantadine hydrochloride lose exclusivity?

Immediate-release amantadine has no meaningful new-drug exclusivity barrier because the active ingredient has long been approved. Generic competition is therefore established.

The extended-release products had limited regulatory exclusivity tied to their approval dates, but their principal commercial barriers are patent rights and formulation complexity.

Product	Approval milestone	Regulatory protection profile	Primary competitive barrier
Generic immediate-release amantadine	Historical	No current NCE exclusivity	Price and distribution
Gocovri	2017	Limited dosage-form and indication exclusivity	Formulation and method-of-use patents
Osmolex ER	2018	Limited dosage-form exclusivity	Extended-release tablet patents and development cost

The key issue is not whether amantadine is old. It is whether a proposed generic can reproduce the required pharmacokinetic and dissolution profile without infringing listed claims.

What Paragraph IV challenges and generic entry risks exist?

A Paragraph IV filer may challenge listed patents by asserting that a patent is invalid, unenforceable, or not infringed. For amantadine extended-release products, the most likely targets are formulation and method-of-use patents rather than composition-of-matter claims.

Likely Paragraph IV theories

A generic applicant could argue that:

• The asserted formulation claims are obvious over earlier controlled-release amantadine products.
• The claimed polymer ratios or release profile lack adequate written description.
• The proposed product uses a noninfringing release mechanism.
• A method-of-use patent is not infringed because the label omits the patented indication.
• The patent claims do not cover the applicant's specific strength or dosage form.
• The patent is invalid for anticipation or obviousness.

Generic launch scenarios

Scenario	Launch timing	Commercial effect
No challenge, patents remain enforceable	After relevant patent expiry	Delayed but lower litigation cost
Paragraph IV challenge with settlement	Settlement-defined date	Controlled entry, potentially with licensed supply
Successful invalidity or noninfringement decision	Before patent expiry	Rapid price erosion and branded volume loss
At-risk launch	Before final resolution	High damages and injunction exposure
Different indication or carve-out	Depends on patent scope	Partial market entry with limited label

The highest-risk product for a generic manufacturer is a direct substitute for Gocovri's once-daily dyskinesia indication using a similar capsule-based release system. A different extended-release tablet or multiparticulate design may offer a stronger noninfringement position, but it can require additional development and regulatory work.

How strong is the amantadine extended-release patent estate?

The estate is materially stronger than the estate for immediate-release amantadine, but weaker than a new chemical entity estate.

Strength factors

• Long clinical history supports safety and regulatory familiarity.
• Extended-release technology can create meaningful formulation barriers.
• Pharmacokinetic and dissolution claims can be difficult to design around.
• Method-of-use claims may protect high-value dyskinesia treatment.
• Different dosage strengths can support multiple claim positions.

Weakness factors

• Amantadine has extensive prior-art exposure.
• Conventional polymers and controlled-release techniques are well known.
• The active ingredient is inexpensive and widely available.
• A competitor can pursue a different dosage form.
• Method-of-use claims may be narrowed by label design.
• Patent term is finite and regulatory exclusivity is limited.

The estate is best characterized as a moderate formulation moat. It can support premium pricing while patents remain enforceable, but it does not prevent eventual multi-source competition.

What manufacturing and IP barriers affect commercial entry?

Manufacturing complexity is a larger barrier for extended-release products than API supply.

API and salt production

Amantadine hydrochloride is a mature API with multiple potential sources. Key manufacturing controls include:

• Assay and related substances
• Residual solvents
• Particle-size distribution
• Polymorphic or solid-state consistency
• Water content
• Bulk density
• Microbial quality
• Uniformity after blending

Particle-size variability can affect blend uniformity, dissolution, and capsule-fill weight. A supplier that provides a narrow particle-size distribution may command a premium even when the API itself is commoditized.

Modified-release manufacturing

The major technical barriers include:

• Polymer grade and viscosity control
• Coating uniformity
• Compression-force control
• Dose-to-dose release consistency
• Stability under humidity
• Alcohol-induced dose dumping
• Food-effect control
• Scale-up from laboratory coating to commercial equipment

Excipient suppliers can create value through qualified polymer grades, coating systems, ready-to-use premixes, and process analytical technology. A co-developed excipient platform can generate stronger customer retention than a single commodity excipient sale.

How does amantadine compare with competing Parkinson's disease products?

Amantadine competes with levodopa combinations, dopamine agonists, MAO-B inhibitors, and other dyskinesia treatments. Its formulation opportunity is distinct because the API is inexpensive but the extended-release product can command a premium based on dosing convenience and symptom control.

Product category	Primary differentiation	Excipient opportunity
Immediate-release amantadine	Low cost	Simplified tablets, capsules, and patient-friendly formats
Extended-release amantadine	Once-daily or controlled exposure	Polymer systems, multiparticulates, osmotic delivery
Levodopa/carbidopa	Core motor-symptom treatment	Combination products and gastroretentive systems
Dopamine agonists	Alternative dopaminergic mechanism	Transdermal, oral controlled-release, and taste-masked systems
Dyskinesia-focused products	Symptom-specific treatment	Dose consistency, reduced peak exposure, and adherence formats

Amantadine does not require biosimilar development. Its competitive challenge is formulation substitution and generic pricing.

What licensing and partnership opportunities exist?

Commercial opportunities are most plausible in four areas:

1. A generic extended-release product using a noninfringing polymer or osmotic platform.
2. A regional license for Gocovri or Osmolex ER equivalents.
3. An excipient and process-development partnership with a specialty generic manufacturer.
4. A 505(b)(2) product using a new dosage form, such as sprinkle capsules, oral suspension, or dispersible mini-tablets.

Supernus acquired Adamas Pharmaceuticals, the developer of Gocovri, in 2021. That transaction consolidated Gocovri commercialization under Supernus.[4] Osmolex ER was developed and commercialized by Osmotica Pharmaceutical, making it a separate commercial and IP opportunity from Gocovri.

Potential deal structures include:

• Regional commercialization rights
• Supply-and-license agreements
• Co-development of a noninfringing extended-release product
• Technology licensing for multiparticulate or osmotic delivery
• Contract manufacturing with formulation know-how transfer
• Authorized-generic arrangements after patent settlement

What revenue exposure exists for branded amantadine products?

Revenue exposure is concentrated in extended-release products because immediate-release amantadine is subject to generic pricing.

A generic launch could affect branded revenue through:

• Rapid price compression
• Pharmacy substitution
• Payer formulary exclusion
• Reduced specialty-pharmacy distribution
• Lower persistence if patient support programs are withdrawn
• Parallel competition between tablet and capsule products

The commercial impact depends on whether the entrant matches the branded indication, dosage schedule, strength range, and reimbursement position. A product approved only for Parkinson's disease may not fully compete with a product positioned for dyskinesia associated with levodopa.

What is the best excipient strategy for a new amantadine product?

The strongest strategy is to avoid a simple copy of an immediate-release capsule and select a differentiated delivery problem.

Recommended development priorities

1. Develop a once-daily multiparticulate capsule with a distinct polymer system.
2. Evaluate sprinkle administration for patients with dysphagia.
3. Screen lactose-free and gelatin-free configurations.
4. Establish alcohol-resistance and food-effect performance early.
5. Use a low-dose strength or titration format to support initiation.
6. Build a formulation patent around release profile, particle architecture, or dosing regimen.
7. Use excipient grades with strong global regulatory precedents.
8. Generate comparative pharmacokinetic data against the relevant reference product.

A formulation that merely substitutes one conventional filler for another is unlikely to create durable commercial value. A formulation that improves administration, dosing frequency, or release robustness can support premium pricing and a defensible 505(b)(2) or specialty-generic position.

Key Takeaways

• Immediate-release amantadine hydrochloride is a mature generic market with limited formulation differentiation.
• Commercial value is concentrated in extended-release products such as Gocovri and Osmolex ER.
• Polymer systems, multiparticulates, osmotic delivery, and patient-friendly dosage forms offer the strongest excipient opportunities.
• Patent exposure is centered on formulation, release profile, dosing, and method-of-use claims.
• Biosimilar risk does not apply because amantadine is a small molecule.
• Generic entry risk is highest for products that directly reproduce once-daily extended-release performance and the branded indication.
• API supply is generally less difficult than modified-release manufacturing.
• The best licensing targets are noninfringing extended-release technologies, specialty generics, and differentiated 505(b)(2) dosage forms.

FAQs

Can amantadine hydrochloride be developed as an orally disintegrating tablet?

Yes. An orally disintegrating tablet could address dysphagia, a common issue in Parkinson's disease. The main formulation risks are taste masking, dose loading, tablet friability, and rapid disintegration without compromising amantadine stability.

Is a liquid amantadine hydrochloride product commercially attractive?

A liquid can address pediatric, geriatric, and dysphagia populations. Its commercial value would depend on palatability, preservative compatibility, dosing accuracy, stability after opening, and whether it provides a clinically differentiated indication.

Which excipient is most important for extended-release amantadine?

No single excipient determines performance. Polymer type, polymer grade, coating level, particle size, compression force, and manufacturing process collectively control release. A change in polymer viscosity can materially alter dissolution and pharmacokinetics.

Does an amantadine generic need to use the same excipients as Gocovri?

No. An ANDA applicant generally must demonstrate pharmaceutical equivalence and bioequivalence to the reference product, not copy every inactive ingredient. The substitute formulation must still meet applicable safety, quality, dissolution, and regulatory requirements.

Can a new amantadine formulation obtain patent protection?

Yes. New patents may protect a novel extended-release architecture, dosage form, release profile, manufacturing process, dosing regimen, or patient population. Patentability is limited where the formulation uses routine excipients and predictable release technology.

References

1. U.S. Food and Drug Administration. (2024). Gocovri (amantadine) extended-release capsules: Prescribing information.
2. U.S. Food and Drug Administration. (2024). Osmolex ER (amantadine hydrochloride) extended-release tablets: Prescribing information.
3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
4. Supernus Pharmaceuticals, Inc. (2022). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.
5. U.S. Food and Drug Administration. (2017). Gocovri approval letter and regulatory review materials.
6. U.S. Food and Drug Administration. (2018). Osmolex ER approval letter and regulatory review materials.