Generic NORFLOXACIN INN equivalents, drug patent expiry and freedom to operate

Sponsor	Phase
Institute of Liver and Biliary Sciences, India	NA
Tanta University	PHASE4
Ospedali Riuniti di Foggia	Phase 3

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Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Merck	NOROXIN	norfloxacin	TABLET;ORAL	019384-002	Oct 31, 1986		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
Merck	CHIBROXIN	norfloxacin	SOLUTION/DROPS;OPHTHALMIC	019757-001	Jun 17, 1991		DISCN	No	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Exclusivity Expiration

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Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Merck	CHIBROXIN	norfloxacin	SOLUTION/DROPS;OPHTHALMIC	019757-001	Jun 17, 1991	4,146,719	⤷ Start Trial
Merck	NOROXIN	norfloxacin	TABLET;ORAL	019384-002	Oct 31, 1986	4,639,458	⤷ Start Trial
Merck	NOROXIN	norfloxacin	TABLET;ORAL	019384-002	Oct 31, 1986	4,146,719	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>Patent No.	>Patent Expiration

Last updated: September 2, 2026

Norfloxacin is a mature, largely generic fluoroquinolone with minimal remaining patent value and declining commercial relevance in major markets. Its original composition-of-matter and primary use patents expired years ago. Current demand is constrained by fluoroquinolone safety restrictions, substitution by nitrofurantoin, trimethoprim-sulfamethoxazole, fosfomycin, ciprofloxacin, and other antibiotics, and the withdrawal or nonmarketing of branded products in several jurisdictions. Public sources do not report a reliable standalone global revenue figure for norfloxacin because sales are fragmented across low-price generic manufacturers and combination or institutional channels.

What is the current market position of norfloxacin?

Norfloxacin is an oral, second-generation fluoroquinolone formerly marketed principally for urinary tract infections, bacterial prostatitis, and selected gastrointestinal infections. Its commercial position has shifted from branded prescription medicine to a low-margin generic antibiotic.

Market factor	Current assessment
Active ingredient	Norfloxacin
Drug class	Fluoroquinolone antibacterial
Primary historical brand	Noroxin
Original innovator	Merck & Co. and regional licensees
Main dosage form	Immediate-release oral tablets, commonly 400 mg
U.S. commercial status	Brand Noroxin is no longer a major marketed product; generic availability is limited and product-specific
Patent position	Core patent protection expired
Regulatory exclusivity	Expired
Biosimilar exposure	None; norfloxacin is a small-molecule drug
Generic competition	High where products remain registered
Pricing power	Low
Commercial trajectory	Mature, declining, and regionally fragmented

Norfloxacin no longer has the characteristics of a high-value branded pharmaceutical. Manufacturers compete mainly through regulatory registration, supply reliability, hospital tenders, distributor access, and low production cost.

When did norfloxacin lose exclusivity?

Norfloxacin lost meaningful exclusivity after expiration of its original chemical and use patents. The exact dates differ by jurisdiction, patent family, patent-term adjustment, and regulatory history, but the relevant protection expired decades ago.

The U.S. Food and Drug Administration’s Orange Book does not provide a current exclusivity framework that would prevent ordinary generic competition for norfloxacin. Any historical listed patents associated with Noroxin are no longer commercially material as barriers to entry. Current entrants would generally face abbreviated new drug application requirements rather than a protected branded market.

Norfloxacin exclusivity timeline

Period	Commercial event	Effect on market
1980s	Norfloxacin introduced and marketed as Noroxin	Branded, patent-protected market
1990s	Generic and regional products expand	Price competition begins
2000s	Core patent protection expires in major markets	Broad generic availability
2010s	Fluoroquinolone safety restrictions intensify	Prescribing declines in several indications
2020s	Mature generic market with uneven regional availability	Low pricing and limited commercial investment

There is no current data indicating a live U.S. composition-of-matter patent or regulatory exclusivity period that materially protects norfloxacin.

What patents protect norfloxacin?

The original norfloxacin patent estate protected the quinolone chemical structure and related pharmaceutical uses. Those rights are expired in the major commercial jurisdictions.

Historical patent categories

Patent category	Historical subject matter	Current commercial significance
Composition of matter	Norfloxacin and related quinolone structures	Expired
Synthetic process	Preparation of norfloxacin intermediates and final compound	Generally expired or circumventable
Pharmaceutical composition	Oral formulations and dosage forms	Expired or commercially weak
Method of treatment	Treatment of urinary and gastrointestinal infections	Expired, unenforceable, or limited by prior art
Combination therapy	Use with other antibacterial agents	Limited value and generally generic
Manufacturing know-how	Crystallization, impurity control, scale-up, and yield optimization	Potential operational advantage, not market exclusivity

The remaining intellectual-property value is more likely to reside in manufacturing know-how, quality systems, impurity specifications, and supply-chain execution than in enforceable exclusivity.

What is the Orange Book status of norfloxacin?

The U.S. Orange Book is not a meaningful source of current market protection for norfloxacin. The branded Noroxin product was approved historically under a new drug application, while generic products were reviewed through abbreviated applications. Historical patents and exclusivity periods do not create a current barrier comparable to those associated with newer drugs.

The regulatory status of individual generic norfloxacin products must be assessed by product and manufacturer. A drug can have an approved application while being commercially unavailable, discontinued, or marketed only in limited quantities.

FDA regulatory considerations

The relevant FDA issues include:

Historical approval of oral norfloxacin for selected bacterial infections.
Class-wide fluoroquinolone boxed warnings.
Restrictions on use for uncomplicated infections when safer alternatives are available.
Product-specific changes in marketing status and availability.
Generic approval based on pharmaceutical equivalence and bioequivalence.

FDA communications have progressively expanded warnings concerning tendinitis and tendon rupture, peripheral neuropathy, central nervous system effects, hypoglycemia, and aortic aneurysm or dissection risk. These actions affect the entire fluoroquinolone class, including norfloxacin, even when a specific product label or market status differs by jurisdiction. (U.S. Food and Drug Administration, 2016, 2018, 2020)

What formulations are protected by norfloxacin patents?

No commercially important live formulation patent is known to protect the standard immediate-release 400 mg norfloxacin tablet in the United States or other mature markets.

Norfloxacin products have historically included:

Immediate-release tablets
Film-coated tablets
Oral solid-dose formulations with conventional excipients
Regional combination products
Limited research or development formulations intended to improve absorption or reduce gastrointestinal effects

Formulation patents could theoretically cover particle size, salt selection, excipient systems, modified release, or delivery mechanisms. Those approaches have limited practical value because norfloxacin is a low-price generic active ingredient and clinical demand has weakened.

Food and mineral interactions also affect product use. Norfloxacin absorption can be reduced by antacids, iron, zinc, calcium, and certain supplements. These characteristics limit the commercial rationale for premium oral formulations unless a developer can demonstrate a clear clinical or adherence advantage.

What method-of-use patents cover norfloxacin?

Historical method-of-use claims covered infections caused by susceptible organisms, including urinary tract and gastrointestinal infections. Those claims are expired or have little practical value because:

The underlying molecule is long off patent.
Many uses are supported by longstanding medical literature.
Fluoroquinolone stewardship restrictions reduce the addressable market.
Generic labels and physician prescribing practices limit differentiation.
New method-of-use claims would face substantial novelty and obviousness challenges.

No current method-of-use patent appears capable of supporting a meaningful branded norfloxacin franchise in the United States.

Which companies are challenging norfloxacin exclusivity?

Norfloxacin’s exclusivity was challenged historically by generic manufacturers after expiration of the original patent estate. The market is now past the principal Paragraph IV competition phase.

Paragraph IV risk

A Paragraph IV certification is relevant when a generic applicant seeks approval before expiration of an Orange Book-listed patent. For norfloxacin, that risk is largely historical because the key patents expired long ago.

Current generic-entry issues are more likely to involve:

Abbreviated new drug application approval
Bioequivalence and dissolution performance
Manufacturing-site compliance
Drug Master File support
Supply continuity
State or national registration requirements
Pharmacovigilance obligations

The absence of meaningful patent protection does not guarantee market entry. Low expected prices, limited demand, regulatory scrutiny, and manufacturing economics can be stronger deterrents than patents.

What patent litigation affects norfloxacin?

No major current U.S. patent litigation involving norfloxacin is commercially prominent. Historical litigation would have centered on the validity, scope, or infringement of the original quinolone patents and generic approval pathways.

The current litigation profile is more likely to involve:

Product liability claims related to fluoroquinolone adverse effects
Manufacturing and quality disputes
Distribution contracts
Regulatory enforcement
Trademark or packaging issues
Procurement disputes in emerging markets

Patent litigation is unlikely to change the competitive structure of the current norfloxacin market.

How strong is the norfloxacin patent estate?

The patent estate is commercially weak because the principal exclusivity period has ended and the molecule has extensive prior art.

Patent-strength factor	Assessment
Composition-of-matter protection	Expired
Remaining term	No material term in major markets
Formulation protection	Limited and unlikely to support premium pricing
Method-of-use protection	Weak or expired
Manufacturing IP	Potentially useful but nonexclusive
Regulatory exclusivity	None of commercial significance
Litigation leverage	Low
Generic entry deterrence	Low
Lifecycle-management potential	Low

A company acquiring norfloxacin rights would be purchasing supply, registration, or distribution capabilities rather than a defensible patent franchise.

How does norfloxacin compare with competing antibiotics?

Norfloxacin competes against both other fluoroquinolones and non-fluoroquinolone therapies. The most important competitors vary by infection type and geography.

Drug	Main commercial advantage	Main limitation relative to norfloxacin
Ciprofloxacin	Broad familiarity, extensive generic supply, strong Gram-negative activity	Similar class safety concerns; resistance
Levofloxacin	Once-daily dosing and broader respiratory positioning	Higher substitution risk from generic competition and safety warnings
Ofloxacin	Established oral and ophthalmic use	Limited differentiation
Nitrofurantoin	Preferred option for many uncomplicated urinary infections	Narrower infection scope
Trimethoprim-sulfamethoxazole	Low cost and established UTI use	Resistance and tolerability
Fosfomycin	Single-dose treatment for selected urinary infections	Limited indication breadth and availability
Amoxicillin-clavulanate	Broad primary-care use	Resistance, tolerability, and spectrum limitations

Norfloxacin historically had a stronger position in urinary infections than in respiratory infections because of relatively limited respiratory activity. That positioning became less attractive as guidelines favored narrower agents for uncomplicated urinary tract infections.

What is the financial trajectory for norfloxacin?

Norfloxacin’s financial trajectory is consistent with long-established generic antibiotics:

Branded revenue declined after patent expiry.
Multiple manufacturers compressed prices.
Clinical restrictions reduced prescription volume.
Substitution by newer or better-positioned generic antibiotics increased.
Manufacturers remained in selected markets where production costs and tender prices supported supply.
Revenue became fragmented and difficult to identify in public financial reports.

Public company filings generally do not disclose norfloxacin revenue separately. The product is often included within broader categories such as generic anti-infectives, hospital products, or international formulations.

Revenue and margin profile

Financial variable	Expected profile
Branded revenue	Effectively absent or immaterial in major markets
Generic unit price	Low
Gross margin	Dependent on scale, procurement, and API cost
Marketing expense	Minimal
R&D investment	Minimal
Price elasticity	High
Tender exposure	High in institutional markets
Inventory risk	Material where demand is volatile
Revenue visibility	Low
Strategic value	Portfolio completeness or regional supply, not innovation

Norfloxacin can still generate revenue in countries where it remains registered and prescribed. Those sales are unlikely to support substantial valuation on a standalone basis. The relevant financial question is usually whether a manufacturer can produce the drug profitably as part of a broader generic portfolio.

What generic launch risks exist for norfloxacin?

A generic launch is technically feasible but commercially selective.

Regulatory and manufacturing barriers

Potential barriers include:

Demonstrating bioequivalence for the relevant tablet strength
Meeting dissolution and impurity specifications
Maintaining validated production processes
Passing FDA or local authority inspections
Securing compliant active pharmaceutical ingredient supply
Managing nitrosamine and other impurity controls where applicable
Maintaining pharmacovigilance systems
Obtaining national registrations in markets with limited reimbursement

These are execution barriers rather than patent barriers.

Commercial launch scenarios

Scenario	Likely outcome
U.S. generic launch with no supply contract	Limited demand and weak return
Hospital or government tender supply	Viable if volume and price are contracted
Emerging-market registration	Potentially viable but exposed to price controls
Premium reformulation	Difficult to justify without clinical differentiation
Contract manufacturing	More attractive than branded commercialization
Portfolio bundling with other anti-infectives	Most commercially rational strategy

What licensing deals involve norfloxacin?

Norfloxacin licensing activity is likely to be concentrated in historical brand licenses, regional registrations, manufacturing agreements, and distribution arrangements. The product is unlikely to attract major current transactions based on patent rights.

The most commercially relevant deal structures are:

Regional marketing licenses
Technology-transfer agreements
API supply contracts
Contract manufacturing
Hospital tender arrangements
Generic portfolio acquisitions
Local registration partnerships

A transaction involving norfloxacin should be valued primarily on registered-market access, manufacturing cost, supply reliability, and contract volume. Patent exclusivity should not be assumed without jurisdiction-specific verification.

What is the geographic coverage of norfloxacin?

Norfloxacin has had broad historical geographic coverage, but current commercial availability is uneven.

Mature markets

In the United States, Canada, Western Europe, Japan, and Australia, fluoroquinolone stewardship, generic substitution, and product withdrawals have reduced norfloxacin’s strategic importance. Availability may be limited even where a product remains technically approved.

Emerging markets

Norfloxacin may remain available in parts of Asia, Latin America, Africa, and the Middle East. Local demand can persist because of low price, established physician familiarity, and variable access to newer therapies. These markets also present risks from:

National price controls
Informal distribution
Antibiotic-resistance concerns
Changing treatment guidelines
Registration changes
Public procurement concentration
Currency volatility

Geographic registration should not be treated as proof of active sales. A product may remain listed in a national database while being commercially unavailable.

What is the biosimilar risk for norfloxacin?

There is no biosimilar risk because norfloxacin is a chemically synthesized small-molecule drug. The relevant competition is generic substitution, not biosimilar interchangeability.

Generic applicants typically compete through abbreviated regulatory pathways based on pharmaceutical equivalence and bioequivalence. This creates low entry barriers relative to biologic products and prevents sustained premium pricing absent a differentiated formulation or distribution position.

What regulatory changes could affect norfloxacin demand?

The main demand risks are regulatory and clinical rather than patent-related.

Potential demand pressures include:

Further restrictions on fluoroquinolone use
Updated warnings about disabling or irreversible adverse reactions
Antimicrobial stewardship programs
Hospital formulary removal
Resistance-driven guideline changes
Greater preference for narrow-spectrum urinary antibiotics
National withdrawal or nonrenewal of older products

FDA communications have advised that systemic fluoroquinolones should be reserved for certain uncomplicated infections when alternative treatments are available because risks may outweigh benefits. (U.S. Food and Drug Administration, 2016)

Key Takeaways

Norfloxacin is a mature generic fluoroquinolone with no commercially meaningful remaining patent exclusivity.
Core composition, formulation, and use protections expired in major jurisdictions.
The U.S. Orange Book does not provide a current exclusivity barrier of strategic importance.
Paragraph IV litigation is primarily historical; current entry risk is regulatory and economic.
Brand revenue has largely disappeared, while generic revenue is fragmented and rarely disclosed separately.
Fluoroquinolone safety warnings and antimicrobial stewardship have reduced demand.
Nitrofurantoin, trimethoprim-sulfamethoxazole, fosfomycin, ciprofloxacin, and levofloxacin are important competitors.
The strongest remaining commercial assets are manufacturing capability, local registrations, API supply, and tender access.
Norfloxacin is more suitable for low-cost portfolio supply than for a standalone branded or patent-driven investment.

FAQs

Is norfloxacin still approved by the FDA?

Historical FDA approval exists for oral norfloxacin products, but current marketing status is product-specific. Approval, active marketing, and commercial availability are separate issues.

Does norfloxacin have any active U.S. patents?

No current U.S. patent is known to provide commercially meaningful exclusivity for the conventional norfloxacin molecule or immediate-release tablet. Historical patents expired after the original branded market period.

Can a generic company still launch norfloxacin?

Yes. A company may pursue an abbreviated application or applicable local generic pathway, but commercial viability depends on demand, registration requirements, manufacturing cost, and supply contracts.

Why has norfloxacin declined relative to nitrofurantoin?

Norfloxacin has been displaced in many uncomplicated urinary tract infections by narrower therapies such as nitrofurantoin, while fluoroquinolone safety warnings and resistance concerns have reduced routine use.

Is norfloxacin commercially attractive in emerging markets?

It can remain commercially viable in selected emerging markets where it is registered, prescribed, and competitively priced. The opportunity is generally volume-driven and dependent on local distribution or procurement contracts rather than patent protection.

References

U.S. Food and Drug Administration. (2016). FDA updates warnings for oral and injectable fluoroquinolone antibiotics due to disabling side effects. https://www.fda.gov
U.S. Food and Drug Administration. (2018). FDA warns about increased risk of ruptures or tears in the aorta blood vessel with fluoroquinolone antibiotics in certain patients. https://www.fda.gov
U.S. Food and Drug Administration. (2020). FDA reinforces safety information about serious low blood sugar levels and mental health side effects with fluoroquinolone antibiotics. https://www.fda.gov
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/
DailyMed. (n.d.). Norfloxacin drug labeling. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/
World Health Organization. (2023). The WHO AWaRe antibiotic book: Antibiotic book. World Health Organization. https://www.who.int/publications/i/item/9789240062382

US Patents:	0
Tradenames:	2
Applicants:	1
NDAs:	2
Drug Master File Entries:	7
Raw Ingredient (Bulk) Api Vendors:	144
Clinical Trials:	26
DailyMed Link:	norfloxacin at DailyMed

Summary for norfloxacin

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