Phenazopyridine hydrochloride; sulfisoxazole - Generic Drug Details

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What are the generic sources for phenazopyridine hydrochloride; sulfisoxazole and what is the scope of freedom to operate?

Phenazopyridine hydrochloride; sulfisoxazole is the generic ingredient in one branded drug marketed by Roche and is included in one NDA. Additional information is available in the individual branded drug profile pages.

Summary for phenazopyridine hydrochloride; sulfisoxazole

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	1
DailyMed Link:	phenazopyridine hydrochloride; sulfisoxazole at DailyMed

Anatomical Therapeutic Chemical (ATC) Classes for phenazopyridine hydrochloride; sulfisoxazole

G04BX	Other urologicals
G04B	UROLOGICALS
G04	UROLOGICALS
G	Genito-urinary system and sex hormones

US Patents and Regulatory Information for phenazopyridine hydrochloride; sulfisoxazole

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Roche	AZO GANTRISIN	phenazopyridine hydrochloride; sulfisoxazole	TABLET;ORAL	019358-001	Aug 31, 1990		DISCN	Yes	No

Phenazopyridine Hydrochloride and Sulfisoxazole: Market Dynamics, Regulatory Status, and Financial Trajectory

Last updated: September 25, 2026

Phenazopyridine hydrochloride is a mature urinary analgesic with an established over-the-counter market in the United States. Sulfisoxazole is an older sulfonamide antibacterial with limited commercial relevance and little current branded-market activity. The combined commercial opportunity is small because the products occupy different market positions: phenazopyridine is a consumer symptom-relief product, while sulfisoxazole has largely been displaced by newer antibiotics.

Public product-level revenue for either ingredient is limited. Market value is concentrated in private-label, pharmacy-brand, and low-cost generic products rather than in a single innovator franchise.

What are phenazopyridine hydrochloride and sulfisoxazole used for?

Phenazopyridine hydrochloride is a urinary tract analgesic. It relieves burning, pain, urgency, and discomfort associated with irritation of the lower urinary tract. It does not treat bacterial infection. In the United States, products containing phenazopyridine are marketed under brands such as AZO and as store-brand urinary pain relievers.

Sulfisoxazole is a sulfonamide antibacterial. It was historically used for urinary tract infections, otitis media, and other susceptible bacterial infections. Its use has declined because of antimicrobial resistance, adverse-reaction concerns, and the availability of more effective antibiotics.

Ingredient	Primary role	Current U.S. commercial position	Prescription or OTC
Phenazopyridine hydrochloride	Urinary tract pain relief	Active consumer-health and generic market	OTC and prescription products
Sulfisoxazole	Antibacterial treatment	Limited or discontinued prescription activity	Historically prescription
Combination products	Symptom relief plus antibacterial treatment	Obsolete or commercially limited	Primarily historical prescription use

Phenazopyridine is often sold alongside urinary tract infection test kits and cranberry products. Sulfisoxazole has no comparable consumer marketing platform.

What is the FDA regulatory status of phenazopyridine hydrochloride?

Phenazopyridine products are marketed in the United States through both OTC monograph-based pathways and prescription drug approvals. OTC products commonly contain 95 mg phenazopyridine hydrochloride per tablet, while prescription products historically used higher-strength formulations.

The FDA has recognized phenazopyridine as an OTC urinary analgesic active ingredient. OTC labeling limits treatment duration because persistent urinary symptoms may indicate infection or another condition requiring medical evaluation. Product labeling generally states that consumers should not use the product for more than two days without consulting a physician.

Key regulatory characteristics include:

• No current new-drug exclusivity supports the ingredient.
• OTC products compete primarily on price, retail placement, packaging, and brand recognition.
• Prescription phenazopyridine products have limited differentiation.
• The FDA does not treat phenazopyridine as an antibacterial agent.
• Renal impairment is a central safety consideration because the drug and metabolites are eliminated through the kidneys. [1]

The market is therefore regulated more like a mature consumer-health category than an innovative prescription-drug market.

What is the FDA status of sulfisoxazole?

Sulfisoxazole is an older antibacterial drug with limited modern U.S. commercial availability. Historical products included sulfisoxazole tablets, oral suspensions, and combination products. The drug has been affected by the same forces that reduced the commercial role of many first-generation sulfonamides:

1. Resistance among bacterial pathogens.
2. Greater use of beta-lactams, fluoroquinolones, macrolides, and trimethoprim-containing regimens.
3. Safety concerns involving hypersensitivity, crystalluria, hematologic effects, and serious cutaneous reactions.
4. Reduced physician demand for legacy sulfonamide antibiotics.
5. Limited commercial incentive to maintain broad product portfolios.

Sulfisoxazole may remain referenced in historical labeling and regulatory databases even where commercial supply is unavailable or highly constrained. A regulatory listing does not establish active market availability.

What products contain phenazopyridine hydrochloride?

The commercial market includes several product formats:

Product format	Typical positioning	Competitive factor
95 mg tablets	OTC urinary pain relief	Brand and retail distribution
97.5 mg or comparable tablets	Store-brand or generic substitution	Lowest cost
Prescription-strength tablets	Physician-directed use	Limited differentiation
Combination urinary products	Pain relief plus adjunct ingredients	Convenience and packaging
Test-kit bundles	Symptom management and self-screening	Retail-channel integration

Brand competition is led by consumer recognition rather than intellectual property. Large retailers and pharmacy chains can source equivalent products from contract manufacturers and generic suppliers.

What patents protect phenazopyridine hydrochloride and sulfisoxazole?

The principal patent estates for both ingredients are effectively legacy estates. Original composition-of-matter patents expired decades ago. Current products depend on manufacturing capability, regulatory compliance, trademarks, packaging, and distribution rather than blocking patents.

Patent category	Phenazopyridine hydrochloride	Sulfisoxazole
Composition-of-matter patents	Expired	Expired
Original product patents	Expired	Expired
Modern formulation patents	Limited commercial significance	Minimal
Method-of-use patents	No meaningful exclusivity	No meaningful exclusivity
Manufacturing patents	Potentially relevant at process level, but unlikely to block routine supply	Potentially relevant, with low commercial value
Trademark protection	Relevant for brands such as AZO	Limited
FDA exclusivity	None of strategic importance	None of strategic importance

No meaningful patent barrier is expected to prevent generic or private-label entry for either ingredient. Formulation patents, if any remain enforceable in particular jurisdictions, are unlikely to create a durable market monopoly because competitors can use conventional immediate-release formulations.

What formulation patents protect these drugs?

Phenazopyridine formulations are generally simple oral tablets. Possible patent claims could cover coating, disintegration, taste masking, packaging, or combinations with other urinary-health ingredients. These claims do not ordinarily protect the active ingredient itself.

Sulfisoxazole formulations historically included tablets, suspensions, and combinations. Any remaining formulation claims would have limited economic value unless they covered a commercially important pediatric, modified-release, or combination product. No such formulation appears to support a major current U.S. franchise.

When do phenazopyridine and sulfisoxazole lose exclusivity?

Both ingredients lost meaningful market exclusivity long ago. The relevant commercial question is not patent expiry but continued supply.

Exclusivity element	Phenazopyridine hydrochloride	Sulfisoxazole
Patent expiry	Historical	Historical
FDA new-drug exclusivity	Expired	Expired
OTC monograph access	Supports continuing entry	Not applicable as a principal pathway
Generic competition	Extensive	Limited because demand is low
Brand protection	Trademark and retail recognition	Minimal
Expected generic launch barrier	Low	Low legally, but demand may not support launch

For phenazopyridine, the absence of exclusivity supports a stable low-price market. For sulfisoxazole, the absence of exclusivity does not guarantee competition because manufacturers may avoid products with weak demand, low margins, or supply-chain complexity.

Are there Paragraph IV challenges or patent litigation?

No major current Paragraph IV litigation is associated with the core active ingredients. Any historical patent disputes would be commercially remote because the basic compounds and standard oral dosage forms are long off patent.

Paragraph IV litigation is also unlikely to be economically rational for phenazopyridine. A generic applicant can compete through an abbreviated or monograph-based pathway without challenging a valuable innovator estate. The market has no large branded prescription product whose revenue would justify prolonged patent litigation.

Sulfisoxazole presents an even weaker litigation profile. The main market constraint is product demand and clinical relevance, not patent enforcement.

What is the Orange Book status of these products?

The Orange Book may contain historical or current entries associated with prescription products containing phenazopyridine or sulfisoxazole, depending on the product and marketing status. Orange Book presence should not be interpreted as evidence of active commercial sales.

The relevant distinctions are:

• A listed product may have been discontinued commercially.
• A product may remain in FDA records while no longer being actively marketed.
• OTC products generally do not create the same Orange Book-based competitive framework as prescription NDAs.
• Historical NDA records can persist after a product leaves the market.
• Patent listings, where present, may be expired or irrelevant to current generic entry.

For commercial diligence, Drugs@FDA, the Orange Book active ingredient search, FDA discontinuation records, and current labeling should be reviewed together. [2]

How strong is the patent estate for phenazopyridine and sulfisoxazole?

The patent estate is weak for both products.

Phenazopyridine has modest commercial defensibility through:

• Established consumer recognition.
• Pharmacy distribution.
• Retail shelf placement.
• Packaging and product-line extensions.
• Manufacturing and quality-control know-how.
• Trademarks.

Those protections can support pricing above the lowest-cost private label, but they do not prevent substitution.

Sulfisoxazole has little strategic defensibility. Its value is constrained by:

• Low clinical demand.
• Generic substitutability.
• Alternative antibiotics.
• Limited prescriber familiarity.
• Potential sourcing and quality-control burdens.
• Antimicrobial stewardship policies.

The strongest barriers for sulfisoxazole are economic and clinical rather than legal.

What generic-entry risks exist?

Phenazopyridine

Generic-entry risk is high, but the risk is largely absorbed by the existing market structure. Numerous manufacturers and private-label suppliers can compete. New entrants would likely take share from incumbent suppliers rather than expand the total market materially.

Competitive pressure is highest in:

• 95 mg immediate-release tablets.
• Store-brand products.
• E-commerce channels.
• Retail pharmacy generic shelves.
• Multi-pack and value-pack formats.

The main risks to incumbent revenue are price erosion, retailer substitution, manufacturing interruptions, and loss of shelf space.

Sulfisoxazole

Legal entry risk is also high, but commercial entry risk is lower because demand is limited. A new supplier could face:

• Low annual volume.
• Weak reimbursement economics.
• Limited prescriber demand.
• Difficulty forecasting procurement.
• Few commercial reasons for brand loyalty.
• Competition from more commonly used antibiotics.

The product could experience supply shortages without creating an attractive long-term market opportunity.

How do the products compare with competing urinary and antibacterial drugs?

Phenazopyridine competes with nonprescription symptom-relief products, not directly with antibiotics on therapeutic effect. Ibuprofen, acetaminophen, hydration, and urinary-health products compete for consumer spending, although they do not have identical indications.

Sulfisoxazole competes with modern antibiotics used for urinary or respiratory infections. Depending on the indication and local resistance patterns, alternatives may include trimethoprim-sulfamethoxazole, nitrofurantoin, fosfomycin, amoxicillin-clavulanate, and cephalosporins.

Market factor	Phenazopyridine	Sulfisoxazole
Demand source	Consumer symptom relief	Prescription antibacterial therapy
Clinical differentiation	Limited	Low versus modern antibiotics
Price sensitivity	High	High
Brand value	Moderate in OTC retail	Low
Prescription growth potential	Minimal	Minimal
Patent strength	Weak	Weak
Supply-chain opportunity	Moderate for private label	Narrow
Revenue durability	Stable but low-growth	Declining or sporadic

What licensing deals affect these products?

No major current licensing transaction is known to drive the commercial outlook for phenazopyridine hydrochloride or sulfisoxazole. The products are generally supplied through direct manufacturing, contract manufacturing, private-label arrangements, or generic distribution agreements.

Licensing value is limited because:

• The active ingredients are off patent.
• Regulatory exclusivity is absent.
• Brand value is concentrated in consumer packaging.
• Product differentiation is limited.
• Sales are fragmented across retailers and generic suppliers.

A transaction involving phenazopyridine would more likely concern a consumer-health portfolio, a regional brand, or a manufacturing arrangement than a license to core drug technology.

What is the financial trajectory for these drugs?

Phenazopyridine should produce a stable but low-growth revenue profile. Its financial trajectory is supported by recurring consumer demand for urinary discomfort relief, broad retail availability, and low-cost manufacturing. Growth is more likely to come from distribution expansion, private-label penetration, combination packs, and e-commerce than from increased medical adoption.

Key financial pressures include:

• Retailer bargaining power.
• Generic price competition.
• Low switching costs.
• Product recalls or manufacturing interruptions.
• Advertising costs for branded products.
• Substitution by store brands.

Sulfisoxazole has a declining or irregular financial trajectory. Revenue is likely concentrated in small institutional, regional, or legacy-product channels. The product does not have the demand characteristics required for meaningful commercial expansion.

Because neither ingredient is typically reported as a standalone segment by public companies, market sizing must rely on retail scanner data, prescription databases, wholesaler data, import records, and company-level product disclosures. Public filings generally do not provide revenue figures specific to phenazopyridine or sulfisoxazole.

What generic launch scenarios are most likely?

Phenazopyridine launch scenario

A new entrant would likely launch an immediate-release tablet under a private-label or generic brand. The launch would compete on unit cost, retailer relationships, and supply reliability. A premium launch based on clinical differentiation would have little chance of success unless paired with a novel delivery format or strong consumer brand.

Sulfisoxazole launch scenario

A new launch would probably require a supply-driven rationale, such as a shortage, institutional demand, or a specialized regional market. A broad commercial launch is unlikely to generate attractive returns without a guaranteed purchaser or procurement contract.

What geographic markets matter?

The United States is the most commercially visible market for phenazopyridine because of its OTC urinary analgesic category. Canada and selected Latin American markets also have urinary analgesic products, but regulatory classifications and brand structures differ.

Sulfisoxazole has greater historical relevance in markets where older sulfonamides remain available. Current opportunity depends on local antimicrobial guidelines, resistance rates, national registration status, and procurement practices. Global sales cannot be inferred from U.S. regulatory records.

Key Takeaways

• Phenazopyridine hydrochloride is a mature OTC and generic urinary analgesic market.
• Sulfisoxazole is an obsolete or commercially limited antibacterial with declining demand.
• Both compounds are long off patent, and neither has a meaningful current composition-of-matter estate.
• Phenazopyridine retains commercial value through brand recognition, retail distribution, and private-label demand.
• Sulfisoxazole has limited financial potential because modern antibiotics have displaced it.
• Paragraph IV litigation and major patent disputes are unlikely.
• The principal risks are price erosion, supply continuity, regulatory compliance, and clinical substitution.
• Phenazopyridine has a stable low-growth revenue profile; sulfisoxazole has a declining or sporadic profile.
• Licensing value is concentrated in brands, manufacturing, and distribution rather than drug technology.

FAQs

Is phenazopyridine hydrochloride an antibiotic?

No. Phenazopyridine is a urinary analgesic that relieves discomfort. It does not eradicate bacterial infection.

Is sulfisoxazole still prescribed for urinary tract infections?

Use is limited. Prescribers generally favor antibiotics with stronger contemporary evidence, better resistance profiles, and broader availability.

Can generic manufacturers enter the phenazopyridine market?

Yes. The active ingredient and standard tablet formulations have no meaningful remaining patent barrier. Entry depends primarily on FDA compliance, manufacturing economics, and retail distribution.

Does phenazopyridine have biosimilar competition?

No. Phenazopyridine is a small-molecule drug, not a biologic. Biosimilar rules do not apply.

Are phenazopyridine and sulfisoxazole commonly sold as a combination today?

No. Combination use is primarily historical. Modern commercial products generally separate symptom relief from antibacterial treatment.

References

1. U.S. Food and Drug Administration. (n.d.). Phenazopyridine hydrochloride labeling and over-the-counter drug information. FDA.

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

3. U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs database. FDA.

4. U.S. National Library of Medicine. (n.d.). DailyMed: Current medication labeling. National Library of Medicine.

5. U.S. Pharmacopeial Convention. (n.d.). Phenazopyridine hydrochloride and sulfisoxazole monographs. United States Pharmacopeia.