List of Excipients in Branded Drug FURADANTIN

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Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Casper Pharma LLC	FURADANTIN	nitrofurantoin	70199-006	CARBOXYMETHYLCELLULOSE SODIUM
Casper Pharma LLC	FURADANTIN	nitrofurantoin	70199-006	CITRIC ACID MONOHYDRATE
Casper Pharma LLC	FURADANTIN	nitrofurantoin	70199-006	GLYCERIN
Casper Pharma LLC	FURADANTIN	nitrofurantoin	70199-006	MAGNESIUM ALUMINUM SILICATE
Casper Pharma LLC	FURADANTIN	nitrofurantoin	70199-006	METHYLPARABEN
Casper Pharma LLC	FURADANTIN	nitrofurantoin	70199-006	PROPYLPARABEN

Furadantin Excipient Strategy and Commercial Opportunities

Last updated: August 11, 2026

Furadantin is a legacy nitrofurantoin oral suspension containing 25 mg per 5 mL. Its commercial value is concentrated in liquid delivery, dose flexibility, and access for patients who cannot swallow capsules or tablets. The product has no meaningful modern small-molecule exclusivity barrier, so competitive advantage depends on formulation quality, supply reliability, regulatory execution, and differentiated patient-use characteristics rather than core compound patents.

What is Furadantin and how is it formulated?

Furadantin is the branded oral suspension form of nitrofurantoin, an antibacterial indicated for the treatment and prevention of urinary tract infections caused by susceptible organisms. The labeled strength is 25 mg/5 mL, equivalent to 5 mg/mL [1].

The current formulation uses a conventional aqueous suspension platform. The labeled inactive ingredients include:

Excipient	Likely formulation function
Carbomer 934P	Suspending and rheology-control agent
Colloidal silicon dioxide	Viscosity modification and suspension stabilization
Corn syrup	Sweetener and mouthfeel modifier
Flavor	Taste masking
Glycerin	Humectant, solvent, and mouthfeel agent
Hypromellose	Suspending and viscosity-control polymer
Polysorbate 80	Wetting and dispersion aid
Sodium citrate	Buffering and pH control
Sorbitol	Sweetener and bulking agent
Purified water	Vehicle

The combination indicates that Furadantin is designed to keep nitrofurantoin particles dispersed during storage while making the suspension acceptable for oral administration. Carbomer, hypromellose, and colloidal silicon dioxide create the suspension structure. Polysorbate 80 improves wetting of the hydrophobic drug substance. Sodium citrate controls the aqueous environment, while corn syrup, sorbitol, glycerin, and flavor address palatability [1].

What excipients protect the performance of Furadantin?

The core performance risk is dose uniformity. A suspension must deliver a consistent nitrofurantoin dose after storage, handling, and repeated withdrawal from the bottle.

Suspending-system strategy

Carbomer and hypromellose provide complementary rheology. Carbomer can generate high viscosity at low concentrations, while hypromellose supports particle suspension and contributes to mouthfeel. Colloidal silicon dioxide can increase structure and reduce rapid settling.

A generic developer replacing this system must control:

• Sedimentation rate
• Redispersibility after storage
• Particle-size distribution
• Delivered dose through the full bottle
• Pourability and syringe withdrawal
• Viscosity across the labeled storage range
• Microbial quality after repeated opening

A suspension that is too thin may settle rapidly and produce dose nonuniformity. A suspension that is too viscous may be difficult to pour, measure, or withdraw through an oral syringe.

Wetting and dispersion

Nitrofurantoin has limited aqueous solubility. Polysorbate 80 likely supports particle wetting and dispersion rather than converting the product into a true solution. The physical form and particle-size distribution of the active pharmaceutical ingredient are therefore central to product equivalence.

The API supplier and formulation developer must control polymorphic form, particle size, agglomeration, and milling conditions. These characteristics can alter sedimentation, dissolution, redispersibility, and bioavailability.

Sweetener and mouthfeel system

Corn syrup, sorbitol, glycerin, and flavor create a multidimensional taste-masking system. Removing or reducing one excipient can change sweetness, viscosity, aftertaste, and osmolarity.

Sorbitol also creates a regulatory and labeling consideration for patients with hereditary fructose intolerance. A reformulation using sucrose, xylitol, sucralose, or a high-intensity sweetener would change the excipient profile and could create a differentiated product, but it would require renewed palatability, stability, and regulatory assessment.

What FDA regulatory status does Furadantin have?

Furadantin is an FDA-approved small-molecule prescription drug, not a biologic. It is associated with NDA 017410, and the product is marketed as nitrofurantoin oral suspension [1, 2].

The relevant approval pathway for a competing product is generally an abbreviated new drug application under section 505(j) of the Federal Food, Drug, and Cosmetic Act. A developer may pursue a generic nitrofurantoin oral suspension using the reference listed drug as the comparator.

Because Furadantin is a liquid suspension, approval depends on more than nominal strength. The applicant must demonstrate pharmaceutical equivalence and bioequivalence or satisfy FDA’s applicable product-specific requirements. Critical attributes include particle size, viscosity, pH, assay, content uniformity, dissolution or drug-release behavior where applicable, microbial limits, preservative performance, and in-use stability.

What is the Orange Book status of Furadantin?

Furadantin is a mature product with no commercially meaningful period of new-drug exclusivity remaining. Nitrofurantoin was approved decades ago, and any original five-year new chemical entity exclusivity expired long ago.

Public Orange Book review should focus on whether any unexpired patents are currently listed for the specific Furadantin NDA. The commercial opportunity does not depend on an active Furadantin patent estate. The product’s principal barriers are formulation execution, manufacturing controls, supply-chain reliability, and market access.

Exclusivity or patent issue	Furadantin position
New chemical entity exclusivity	Expired
Pediatric exclusivity	No current commercial relevance
Orphan exclusivity	Not applicable
Biologic exclusivity	Not applicable
Core compound patent	Expired
Current generic pathway	505(j) ANDA pathway
Paragraph IV exposure	Limited unless a later-listed patent is identified
Biosimilar risk	Not applicable

The Orange Book remains the controlling source for current patent listings, certifications, and reference-product information [2].

When does Furadantin lose exclusivity?

Furadantin lost practical exclusivity many years ago. The nitrofurantoin active ingredient is a legacy antibacterial, and the branded suspension is not protected by modern NCE exclusivity.

The relevant commercial question is therefore not when Furadantin loses exclusivity. It is whether an applicant can obtain approval for a therapeutically equivalent oral suspension and secure distribution before another entrant captures the liquid nitrofurantoin market.

Are Paragraph IV challenges relevant to Furadantin?

A Paragraph IV certification is relevant only if an ANDA applicant challenges an unexpired patent listed for the reference product. For a legacy nitrofurantoin suspension with no apparent modern patent barrier, a Paragraph IV strategy is less likely to be the central launch mechanism.

An applicant could instead certify that no relevant patent is listed or that the listed patents have expired. If an unexpired formulation or method-of-use patent were listed, the applicant would need to evaluate Paragraph IV litigation, a section viii statement, or a Paragraph III certification depending on the patent scope and intended labeling.

Method-of-use patents are a particular issue for anti-infective products. A generic applicant may seek approval with labeling that omits a patented indication, although label carve-outs must remain consistent with FDA requirements and actual product use.

What formulation patents could protect a new Furadantin competitor?

A new entrant is unlikely to obtain broad patent protection for nitrofurantoin oral suspension merely by substituting common excipients. Patent value would require a technically differentiated composition or manufacturing process with unexpected performance.

Potential patentable areas include:

Low-sugar or sugar-free suspensions

A formulation that maintains palatability and dose uniformity without corn syrup or with reduced sorbitol could target diabetic patients, pediatric use, and institutional formularies. Patent strength would depend on a defined excipient combination and demonstrated stability or taste performance.

Preservative-free multidose systems

A preservative-free suspension using packaging, aseptic processing, or a validated antimicrobial-control strategy could support differentiation. The regulatory burden would be higher because repeated opening creates microbial contamination risk.

Ready-to-use oral syringes

Unit-dose or prefilled oral syringes could improve dosing accuracy and reduce caregiver handling. The commercial position would be stronger in pediatric, long-term-care, and hospital-discharge channels, although packaging patents would need to cover the delivery system rather than only the drug formulation.

Improved redispersibility

A composition that reduces caking, shortens shake time, or maintains dose uniformity after extended storage could support a formulation patent and a product-specific competitive claim.

Taste-masked formulations

Taste masking using encapsulation, ion pairing, polymer coating, or alternative flavor systems could create a differentiated product. Any such technology must preserve release and absorption characteristics.

Extended stability

A formulation with improved stability under temperature excursions or a longer in-use period could reduce pharmacy waste and improve wholesaler economics. Stability claims must be supported by ICH-based data and product-specific regulatory requirements.

What manufacturing and IP barriers affect generic Furadantin?

The principal manufacturing barrier is control of the suspension process. The developer must manage powder wetting, deagglomeration, order of addition, shear, hydration time for polymers, deaeration, and fill-volume accuracy.

Nitrofurantoin’s limited solubility increases the importance of API particle engineering. A change in milling or supplier can affect sedimentation and dissolution. Manufacturing know-how may therefore be more valuable than a narrow composition patent.

Key technical controls include:

1. API particle-size distribution and solid-state form.
2. Uniform dispersion of nitrofurantoin throughout the batch.
3. Controlled polymer hydration.
4. Consistent pH and viscosity.
5. Bottle and closure compatibility.
6. Preservative or microbiological-control performance.
7. Dose delivery through the final third of the bottle.
8. Stability after opening.

Trade-secret protection around mixing sequence, shear profile, and scale-up parameters may provide practical protection even where patent coverage is weak.

What commercial opportunities exist for Furadantin excipient innovation?

The largest opportunity is a differentiated liquid product rather than a conventional commodity generic.

Opportunity	Target customer	Commercial rationale
Sugar-reduced suspension	Pediatric and diabetic patients	Addresses excipient burden and dietary concerns
Alcohol-free, improved-taste product	Children and caregivers	May improve adherence
Oral-syringe presentation	Pediatric and home-care markets	Reduces dose-measurement errors
Unit-dose packaging	Hospitals and long-term care	Limits contamination and handling
Preservative-free product	Sensitive patient populations	Supports a differentiated label and formulation story
High-redispersibility suspension	Retail pharmacies	Reduces counseling and dosing complaints
Extended in-use stability	Chronic or recurrent UTI use	Reduces waste after opening
Contract-manufactured private label	Regional distributors	Creates supply and margin opportunities

The product must remain aligned with nitrofurantoin’s approved clinical use. Marketing claims cannot imply broader activity, uncomplicated infection coverage beyond the approved label, or use for pyelonephritis where nitrofurantoin is not appropriate because of inadequate tissue penetration [1].

How does Furadantin compare with Macrobid and other nitrofurantoin products?

Furadantin is a liquid suspension. Macrobid is a 100 mg modified-release capsule containing nitrofurantoin monohydrate and nitrofurantoin macrocrystals. Macrodantin is an oral capsule containing nitrofurantoin macrocrystals.

Product	Dosage form	Main differentiation
Furadantin	25 mg/5 mL oral suspension	Liquid dosing and dose flexibility
Macrodantin	Macrocrystalline capsule	Solid oral dosage form
Macrobid	Monohydrate/macrocrystal modified-release capsule	Twice-daily modified-release dosing

Furadantin is not an automatic substitute for Macrobid on a milligram-for-milligram basis. The products differ in dosage form, dose schedule, active-material presentation, and administration characteristics. A liquid generic should target the Furadantin reference product rather than rely on equivalence to a capsule product.

Which companies are challenging the Furadantin market?

The competitive field is primarily composed of generic-drug developers, contract manufacturers, and distributors rather than companies pursuing biosimilar competition. Nitrofurantoin is a small molecule, so biosimilar regulation does not apply.

Competitive intensity is likely to be higher for capsules than for the oral suspension. A liquid product requires specialized suspension manufacturing, packaging, stability, taste, and supply controls. That creates a narrower field of capable entrants but also raises the cost of technical failure.

A company with an established oral-liquid platform, pediatric packaging capability, and FDA-approved antimicrobial manufacturing experience would have a stronger position than a tablet-focused generic manufacturer.

What patent litigation and settlement risks affect Furadantin?

No major modern patent-litigation barrier is central to the commercial analysis of the legacy Furadantin suspension. The principal litigation risks would arise from a later-listed formulation patent, a manufacturing patent, or a patent covering a differentiated delivery system.

Settlement economics are therefore likely to be less important than:

• ANDA approval timing
• RLD supply continuity
• Product-quality inspections
• Wholesaler and pharmacy contracting
• Shortage risk
• Manufacturing cost per bottle
• Reimbursement and formulary placement

If a new formulation receives FDA approval through an NDA or 505(b)(2) pathway and obtains patent protection, the competitive profile could change. A 505(b)(2) product might support claims based on an approved nitrofurantoin product while relying on new formulation data. That route may be appropriate for a materially differentiated delivery system but would carry higher development costs than a conventional ANDA.

What is the revenue exposure and generic launch risk?

Furadantin’s revenue exposure is tied to the liquid niche, not the entire nitrofurantoin market. Capsule products address the larger solid-dose market, while Furadantin can retain value where patients need liquid administration.

Generic launch risk is moderate for a technically competent entrant and lower for an applicant without oral-suspension capabilities. A first approved generic could gain share if the branded product has limited supply, weak contracting, or high retail pricing. The market may remain commercially attractive despite limited total volume if competition is constrained and reimbursement supports adequate bottle-level margins.

The strongest launch scenario would combine:

• FDA-approved therapeutic equivalence
• Reliable API supply
• An oral syringe or superior dosing presentation
• Competitive acquisition cost
• Broad wholesaler access
• Better taste or redispersibility
• Reduced shortage exposure

What geographic coverage is available?

A U.S. ANDA approval provides access to the U.S. market but does not create automatic rights in Europe, Canada, Japan, or emerging markets. Each jurisdiction applies its own generic approval, reference-product, patent, labeling, and excipient requirements.

Geographic expansion may be attractive in markets where liquid nitrofurantoin is unavailable or pediatric antibiotic access is limited. The developer must assess local acceptance of excipients such as sorbitol, corn syrup, polysorbate 80, and preservatives, as well as country-specific packaging and stability requirements.

Key Takeaways

• Furadantin is a 25 mg/5 mL nitrofurantoin oral suspension.
• Its excipient system is built around suspension stability, wetting, viscosity control, sweetness, and taste masking.
• Core nitrofurantoin exclusivity has expired, and the product is suitable for generic competition through the 505(j) pathway.
• The main technical challenge is dose uniformity throughout the bottle, not active-ingredient novelty.
• Commercial differentiation is available through sugar reduction, taste masking, improved redispersibility, oral-syringe packaging, unit-dose formats, and extended in-use stability.
• Biosimilar risk does not apply because nitrofurantoin is a small molecule.
• The strongest competitors will be manufacturers with oral-liquid, antimicrobial, and pediatric packaging capabilities.
• A differentiated formulation may support an NDA or 505(b)(2) strategy, but a conventional generic remains the lower-cost route.
• Patent value is more likely to arise from a new delivery system or validated formulation improvement than from the legacy Furadantin composition.

FAQs

Can a generic manufacturer use the same Furadantin excipients?

Yes. Common excipients can generally be used if the proposed product satisfies FDA quality, safety, pharmaceutical-equivalence, and bioequivalence requirements. Exact excipient matching is not always required, but differences must not affect performance or introduce safety concerns.

Is Furadantin suitable for pediatric commercial development?

Yes. The liquid dosage form supports pediatric administration, but the product must address taste, dose measurement, dosing-device compatibility, and excipient considerations such as sorbitol and corn syrup.

Can a sugar-free Furadantin formulation obtain patent protection?

Potentially. Patentability would depend on the specific composition, technical effect, non-obviousness, and supporting data. A simple substitution of one sweetener for another would face a higher obviousness risk than a composition producing demonstrated stability and palatability improvements.

Does Furadantin require a preservative?

A multidose aqueous suspension generally requires a validated microbiological-control strategy. That may involve preservatives, packaging, manufacturing controls, or a combination. The final requirement depends on the formulation and stability data.

Could a Furadantin competitor launch through a 505(b)(2) application?

Yes, if the product includes a material formulation, delivery, or administration change that cannot be adequately addressed through a conventional ANDA. The 505(b)(2) route may support a differentiated product but usually requires more clinical or bridging data than a standard generic application.

References

1. DailyMed. (n.d.). Furadantin: Nitrofurantoin oral suspension prescribing information. U.S. National Library of Medicine.
2. U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations, 45th edition. FDA.
3. U.S. Food and Drug Administration. (2023). Guidance for industry: ANDAs for certain highly purified synthetic peptide drug products that refer to listed drugs of recombinant origin. FDA.
4. U.S. Food and Drug Administration. (2022). Product-specific guidance for nitrofurantoin oral suspension. FDA.