List of Excipients in Branded Drug DARIFENACIN HYDROBROMIDE

Generic Drugs Containing DARIFENACIN HYDROBROMIDE

Company	Ingredient	NDC	Excipient
Par Pharmaceutical Inc	darifenacin hydrobromide	10370-170	CALCIUM PHOSPHATE, DIBASIC, ANHYDROUS
Par Pharmaceutical Inc	darifenacin hydrobromide	10370-170	D&C YELLOW NO. 10
Par Pharmaceutical Inc	darifenacin hydrobromide	10370-170	FD&C YELLOW NO. 6

What are the Most Frequently-Used Excipients in DARIFENACIN HYDROBROMIDE?

# Of NDCs	Excipient
1	CALCIUM PHOSPHATE, DIBASIC, ANHYDROUS
1	D&C YELLOW NO. 10
1	FD&C YELLOW NO. 6

Darifenacin Hydrobromide Excipient Strategy and Commercial Opportunities

Last updated: August 27, 2026

Darifenacin hydrobromide is a mature, orally administered antimuscarinic used for overactive bladder. Its commercial value is concentrated in extended-release tablet technology, reliable excipient sourcing, generic manufacturing, and regional supply agreements rather than new-molecule exclusivity. The core formulation opportunity is a once-daily hydrophilic matrix tablet that controls darifenacin release without compromising dose uniformity, dissolution performance, or long-term stability.

What is the FDA regulatory status of darifenacin hydrobromide?

Darifenacin hydrobromide is approved in the United States as an extended-release tablet under the brand Enablex. The product is indicated for adults with symptoms of overactive bladder, including urge urinary incontinence, urgency, and frequency.[1]

Regulatory attribute	Publicly reported status
Active ingredient	Darifenacin hydrobromide
Dosage form	Extended-release oral tablet
Strengths	7.5 mg and 15 mg
Reference brand	Enablex
Original NDA	NDA 021513
FDA approval	2004
Administration	Once daily
Therapeutic class	Muscarinic M3 receptor antagonist
Primary market	Overactive bladder
Generic pathway	Abbreviated New Drug Application, subject to product-specific requirements
Biosimilar pathway	Not applicable because darifenacin is a small molecule

The recommended initial dose is 7.5 mg once daily, with an increase to 15 mg once daily based on response and tolerability.[1] The tablets are designed for extended release and should be swallowed whole rather than crushed, divided, or chewed.

What excipients are used in darifenacin extended-release tablets?

The Enablex formulation uses conventional oral solid-dose excipients, with the release profile primarily dependent on the matrix and tablet manufacturing process. Public labeling identifies the following inactive ingredients.[1,2]

Excipient category	Examples associated with the marketed formulation	Functional role
Hydrophilic matrix former	Hypromellose	Controls water penetration, swelling, gel formation, and drug diffusion
Diluent	Microcrystalline cellulose	Provides tablet mass, compressibility, and mechanical strength
Diluent or bulking agent	Lactose monohydrate	Improves tablet weight and manufacturability
Lubricant	Magnesium stearate	Reduces die-wall friction during compression
Glidant	Colloidal silicon dioxide	Improves powder flow and content uniformity
Film-coat polymer	Hypromellose or related coating polymer	Provides protection, appearance, and swallowability
Plasticizer	Polyethylene glycol	Improves coating flexibility
Anti-adherent or coating aid	Talc	Reduces sticking and supports coating performance
Opacifier and colorant	Titanium dioxide and iron oxide, depending on strength and market	Provides product identification and light protection

The precise excipient composition may differ between the reference product and individual generic products. FDA labeling and product-specific regulatory filings remain the controlling sources for each marketed product.

How does the excipient strategy control darifenacin release?

Darifenacin is suitable for an extended-release matrix because once-daily administration reduces dosing frequency and provides a controlled exposure profile. The formulation must prevent rapid drug liberation while maintaining acceptable release across the gastrointestinal tract.

Hydrophilic matrix design

Hypromellose is the most commercially important excipient in the formulation strategy. After hydration, the polymer forms a gel layer around the tablet. Drug release then occurs through a combination of:

• Water penetration into the matrix
• Polymer swelling
• Drug diffusion through the hydrated gel
• Progressive erosion of the matrix

The grade and viscosity of hypromellose materially affect release. Higher-viscosity grades generally produce a stronger gel and slower release, but they can increase compression sensitivity, prolong dissolution, and create scale-up challenges.

Diluent selection

Microcrystalline cellulose and lactose provide different processing characteristics. Microcrystalline cellulose improves compactability and tablet strength. Lactose can improve powder handling and tablet mass but introduces lactose exposure for patients with intolerance and can affect moisture behavior.

A lactose-free generic formulation is commercially possible, but it may require dissolution redevelopment and comparative bioequivalence work. Replacing lactose with dibasic calcium phosphate, mannitol, or additional microcrystalline cellulose can alter tablet porosity, hydration, and release kinetics.

Lubrication control

Magnesium stearate concentration and blending time require tight control. Excessive lubrication can reduce tablet tensile strength and slow liquid penetration into the matrix. Under-lubrication can cause sticking, picking, and weight variability.

For darifenacin, lubricant optimization is a critical scale-up variable because small changes in tablet porosity can affect extended-release dissolution.

Film-coating strategy

The film coat generally has limited impact on release if it is nonfunctional and thin. Its primary commercial roles are:

• Product differentiation by strength
• Protection from light and handling damage
• Improved swallowability
• Reduction of tablet dust
• Support for serialization and brand identification

A functional coating could create a new release mechanism, but it would increase development and regulatory complexity. For a mature generic product, a conventional immediate-release film coat is usually the lower-risk approach.

What formulation patents protect darifenacin products?

The original composition, compound, and extended-release intellectual property associated with darifenacin was filed before the 2004 U.S. approval of Enablex. The principal commercial exclusivity period has expired, and darifenacin is now a generic small-molecule opportunity rather than an innovator patent-protection opportunity.

Current commercial protection is more likely to arise from:

1. Product-specific manufacturing know-how
2. Dissolution-control methods
3. Excipient grade selection
4. Tablet compression and coating parameters
5. Regional formulation patents outside the United States
6. Trade secrets covering scale-up and process controls
7. Supplier agreements for critical excipients

An Orange Book patent listing is relevant only if a patent remains listed against the reference NDA. Product developers should distinguish expired compound or formulation patents from nonlisted process patents and foreign rights. Process patents can affect manufacturing strategy, but they do not create the same ANDA certification framework as a listed Orange Book patent.

When did darifenacin lose market exclusivity?

The original FDA approval occurred in 2004. New chemical entity exclusivity for a small-molecule drug generally lasts five years, subject to statutory exceptions for patent challenges and certain certifications.[3] That period would have ended in 2009 for a standard NCE approval.

The commercially important patent term also expired years ago, allowing generic development. The exact endpoint for each historical patent family depends on filing date, patent-term adjustment, patent-term extension, terminal disclaimers, and jurisdiction. Darifenacin therefore has no meaningful remaining U.S. molecule-level exclusivity based on the original Enablex approval.

Exclusivity category	Darifenacin status
NCE exclusivity	Expired
Original compound patents	Expired or commercially exhausted in the United States
Original extended-release patents	Expired or commercially exhausted in the United States
Pediatric exclusivity	No material current barrier identified
Orphan exclusivity	Not applicable
Biosimilar reference-product exclusivity	Not applicable
Current generic opportunity	Open, subject to FDA product-specific requirements

What is the Orange Book status of darifenacin?

The FDA Orange Book identifies approved drug products, reference-listed drugs, therapeutic-equivalence evaluations, and relevant patent or exclusivity information.[4] Darifenacin extended-release tablets are treated as conventional small-molecule generic products, not biologics.

For an ANDA applicant, the key regulatory issues are:

• Identification of the correct reference-listed drug
• Matching the approved dosage form and strengths
• Demonstration of bioequivalence
• Comparative extended-release dissolution
• Compliance with product-specific FDA guidance, if applicable
• Proper labeling and tablet-handling instructions
• Evaluation of inactive ingredients under FDA requirements

The absence of an active listed patent does not eliminate all commercial risk. A manufacturer can still face intellectual-property claims involving manufacturing processes, nonlisted formulation rights, trade secrets, trademarks, or foreign-market patents.

What generic entry risks exist for darifenacin?

Darifenacin has a lower legal barrier than a recently approved branded drug, but formulation and commercial risks remain.

Bioequivalence risk

Extended-release products require more than simple immediate-release dissolution matching. The applicant must demonstrate that the test product produces comparable exposure to the reference product. Depending on FDA requirements, this can involve fasting and fed studies, multiple-dose studies, and additional pharmacokinetic comparisons.[5]

The main technical risks include:

• Early drug release or dose dumping
• Food-effect differences
• Failure to match terminal exposure
• Strength proportionality problems
• Tablet-to-tablet dissolution variability
• Sensitivity to manufacturing scale
• Interaction between polymer viscosity and compression force

Manufacturing risk

A matrix tablet may appear simple but can be sensitive to:

• Hypromellose particle size and viscosity
• Granulation endpoint
• Water content
• Lubricant blending time
• Compression force
• Tablet hardness
• Coating weight gain
• Storage humidity

Manufacturers that rely on direct compression may reduce process steps but face greater sensitivity to powder flow and content uniformity. Wet granulation can improve blend uniformity and compressibility but introduces moisture and drying variables.

Commercial risk

Darifenacin competes in a crowded overactive-bladder market that includes oxybutynin, tolterodine, solifenacin, fesoterodine, trospium, and mirabegron. Generic pricing pressure is significant because physicians and payers have multiple pharmacologic alternatives.

The strongest commercial positions are likely to come from:

• Low-cost, high-volume generic supply
• Reliable availability during competitor shortages
• Multi-country registrations
• Dual-source excipient procurement
• Contract development and manufacturing
• Lactose-free or differentiated excipient variants
• Smaller regional markets where generic competition is limited

Which companies are challenging or supplying darifenacin?

Darifenacin has been subject to generic development by multiple pharmaceutical manufacturers. Generic availability has varied by country, strength, and time. Public FDA product databases and national medicine registers should be used to verify the current applicant, marketing authorization holder, and commercial status for a particular jurisdiction.[4,6]

The market structure generally includes:

Participant type	Commercial role
Reference-product sponsor	Maintains the original brand and regulatory reference
Generic pharmaceutical companies	File ANDAs or equivalent national applications
API manufacturers	Supply darifenacin hydrobromide
Excipient suppliers	Provide hypromellose, cellulose, lactose, lubricants, and coating systems
CDMOs	Manufacture tablets, perform packaging, and support registration batches
Regional distributors	Supply pharmacies and hospital channels
Specialty formulation developers	Explore differentiated release profiles or patient-use formats

Because the product is mature, a new entrant generally competes on cost, supply reliability, regulatory execution, and geographic coverage rather than clinical differentiation.

What excipient commercial opportunities exist for darifenacin?

1. Functional hypromellose supply

Hypromellose is the highest-value excipient target because it directly controls extended release. Suppliers can compete through:

• Narrow viscosity specifications
• Lot-to-lot release consistency
• Pharmaceutical-grade documentation
• Global regulatory support
• Supply continuity
• Compatibility with direct compression
• Low microbial and elemental impurity profiles

A supplier able to provide the same functional performance across multiple manufacturing sites can reduce comparability work for generic manufacturers.

2. Excipient substitution programs

Manufacturers may seek alternatives to lactose, titanium dioxide, or specific coating systems. Substitution opportunities include:

• Lactose-free matrix tablets
• Titanium-dioxide-free film coating
• Low-dust excipient systems
• Direct-compression blends
• Plant-based or regional excipient sources
• Moisture-controlled packaging and excipient systems

Each substitution must be evaluated against dissolution, stability, tablet strength, and bioequivalence requirements.

3. Premixed excipient platforms

A prequalified matrix system containing hypromellose, microcrystalline cellulose, and a flow aid can reduce formulation development time. The commercial advantage is strongest when the platform provides predictable compaction and release over several strengths.

For darifenacin, the platform must accommodate low drug loading and maintain content uniformity. The product is therefore a candidate for engineered excipient blends rather than simple commodity excipient sales.

4. CDMO and technology-transfer services

A CDMO can offer value through:

• Small-scale formulation screening
• Dissolution method development
• Pilot and registration batches
• Scale-up of hydrophilic matrix tablets
• Stability programs
• Packaging qualification
• ANDA or national dossier support

The strongest barriers are process reproducibility and regulatory documentation rather than chemical synthesis.

5. Regional supply opportunities

Darifenacin remains commercially relevant in countries where:

• Generic penetration is incomplete
• Enablex or local brands retain physician recognition
• Overactive-bladder treatment is expanding
• Solifenacin or mirabegron prices remain high
• Local production is favored by procurement policy

A regional strategy may support separate excipient and API sourcing if local regulatory rules permit. Manufacturers should avoid unnecessary formulation differences that create multiple dissolution and stability programs.

How does darifenacin compare with competing overactive-bladder drugs?

Drug	Dosage-form opportunity	Main commercial issue	Excipient relevance
Darifenacin	Extended-release tablet	Mature generic market	High relevance of matrix polymers and dissolution control
Solifenacin	Immediate-release tablet	Broad generic competition	Lower release-control complexity
Tolterodine	Immediate- and extended-release products	Multiple generic suppliers	ER products require matrix or multiparticulate control
Oxybutynin	Immediate-, ER, and transdermal products	Strong generic pressure and tolerability concerns	Delivery-system differentiation is more important
Trospium	Immediate- and extended-release products	Niche demand and administration restrictions	Release technology and moisture control matter
Mirabegron	Extended-release tablet	More recent branded and generic-transition dynamics	Greater importance of formulation and regulatory exclusivity

Darifenacin has a narrower technical opportunity than transdermal oxybutynin but a clearer excipient value proposition than an immediate-release antimuscarinic. The product is best positioned as a controlled-release manufacturing and supply-chain opportunity.

What licensing and partnership opportunities exist?

Publicly reported licensing economics for darifenacin are limited because the product is mature and genericized. Commercial partnerships are more likely to involve supply and manufacturing than new-molecule licensing.

Potential structures include:

• Exclusive regional commercialization rights
• API and finished-dose supply agreements
• Dual-source excipient contracts
• CDMO technology-transfer agreements
• Co-development of lactose-free or coating-modified versions
• In-licensing of country-specific marketing authorizations
• Private-label supply to pharmacy and institutional buyers

The most defensible partnership asset is a validated extended-release platform that can support multiple antimuscarinic products. A single-product darifenacin agreement is more exposed to price erosion and tender competition.

What revenue exposure does darifenacin create?

Darifenacin revenue is difficult to isolate because branded and generic sales are reported inconsistently across manufacturers. The product is a mature, lower-growth prescription medicine, and the principal revenue risks are:

• Generic price erosion
• Payer substitution
• Competition from solifenacin and mirabegron
• Anticholinergic tolerability concerns
• Supply interruptions
• Low reimbursement margins
• Limited differentiation between generic tablets

Excipient suppliers should evaluate the opportunity by annual tablet volume, approved markets, and number of qualified manufacturers rather than relying on brand sales alone. A large-volume contract with one generic manufacturer may be more valuable than a small branded formulation project.

How strong is the patent estate for darifenacin?

The current U.S. patent estate is weak as a barrier to generic entry. The original compound and extended-release exclusivity periods have ended, and the commercial product is exposed to conventional ANDA competition.

Patent strength remains higher in narrow areas:

IP area	Relative strength
Original chemical entity	Low in the United States because historical protection has expired
Original extended-release formulation	Low for blocking current generic entry
Manufacturing process	Potentially relevant if unexpired and enforceable
Excipient composition	Usually weak unless tied to a specific functional release profile
Packaging and device claims	Limited relevance for standard tablets
Trade secrets	Potentially meaningful for process performance
Foreign patent rights	Country-specific and potentially relevant

A new patent strategy would need to claim a technically distinct formulation, delivery system, manufacturing process, or clinical use. Routine substitution of one standard tablet excipient for another is unlikely to create durable exclusivity.

Key Takeaways

• Darifenacin hydrobromide is a mature small-molecule overactive-bladder drug supplied as 7.5 mg and 15 mg extended-release tablets.
• Hypromellose is the central functional excipient because it controls matrix hydration and drug release.
• Microcrystalline cellulose, lactose, magnesium stearate, colloidal silicon dioxide, and film-coating excipients support manufacturability and product presentation.
• U.S. NCE and original product exclusivity have expired, leaving generic entry as the principal commercial pathway.
• Current opportunity is concentrated in low-cost manufacturing, functional excipient supply, CDMO services, regional licensing, and reliable generic distribution.
• The main development risks are extended-release bioequivalence, food-effect performance, dissolution variability, and scale-up reproducibility.
• Biosimilar risk is irrelevant because darifenacin is a chemically synthesized small molecule.
• A new entrant is more likely to win through supply reliability and process economics than through broad patent protection.

FAQs about darifenacin hydrobromide excipients and commercial strategy

Can darifenacin extended-release tablets be made without lactose?

Yes. Lactose can be replaced with other diluents, but the substitute may change tablet porosity, hydration, hardness, dissolution, and stability. A lactose-free product requires formulation redevelopment and regulatory comparability work.

Which hypromellose grade is suitable for darifenacin extended release?

A pharmaceutical-grade hypromellose with a controlled viscosity profile is the likely starting point. The final grade and loading must be selected through dissolution, compression, stability, and bioequivalence development rather than by viscosity designation alone.

Is darifenacin hydrobromide suitable for a 505(b)(2) product?

A 505(b)(2) pathway could be relevant for a materially differentiated dosage form, delivery system, or administration route. A conventional generic extended-release tablet would generally be better aligned with the ANDA pathway.

Does darifenacin have biosimilar competition?

No. Darifenacin is a small-molecule drug. Competition occurs through generic-drug pathways, not biosimilar applications.

What is the most attractive investment area in darifenacin?

The most attractive areas are qualified extended-release excipient systems, API and finished-dose supply, and CDMO manufacturing. A stand-alone branded reformulation has limited value unless it provides a clear clinical or adherence advantage.

References

1. U.S. Food and Drug Administration. (2004). Enablex (darifenacin hydrobromide) extended-release tablets prescribing information.
2. National Library of Medicine. (n.d.). DailyMed: Darifenacin hydrobromide extended-release tablets.
3. U.S. Food and Drug Administration. (2024). New chemical entity exclusivity and generic drug patent certification requirements.
4. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Orange Book.
5. U.S. Food and Drug Administration. (2015). Guidance for industry: Bioequivalence studies with pharmacokinetic endpoints for drugs submitted under an ANDA.
6. U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs database.