AZULFIDINE Drug Patent Profile

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When do Azulfidine patents expire, and when can generic versions of Azulfidine launch?

Azulfidine is a drug marketed by Pharmacia And Upjohn and Pfizer and is included in two NDAs.

The generic ingredient in AZULFIDINE is sulfasalazine. There is one drug master file entry for this compound. Ten suppliers are listed for this compound. Additional details are available on the sulfasalazine profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Azulfidine

A generic version of AZULFIDINE was approved as sulfasalazine by WATSON LABS on December 31^st, 1969.

Summary for AZULFIDINE

US Patents:	0
Applicants:	2
NDAs:	2
Finished Product Suppliers / Packagers:	5
Raw Ingredient (Bulk) Api Vendors:	117
Clinical Trials:	4
Patent Applications:	4,812
Drug Prices:	Drug price information for AZULFIDINE
What excipients (inactive ingredients) are in AZULFIDINE?	AZULFIDINE excipients list
DailyMed Link:	AZULFIDINE at DailyMed

See drug prices for AZULFIDINE

Recent Clinical Trials for AZULFIDINE

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
University of Erlangen-Nürnberg Medical School	Phase 3
Columbia University	Phase 4
Brigham and Women's Hospital	Phase 4

See all AZULFIDINE clinical trials

Pharmacology for AZULFIDINE

Drug Class

Aminosalicylate

US Patents and Regulatory Information for AZULFIDINE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Pharmacia And Upjohn	AZULFIDINE	sulfasalazine	SUSPENSION;ORAL	018605-001	Approved Prior to Jan 1, 1982		DISCN	No	No
Pfizer	AZULFIDINE	sulfasalazine	TABLET;ORAL	007073-001	Approved Prior to Jan 1, 1982	AB	RX	Yes	Yes
Pfizer	AZULFIDINE EN-TABS	sulfasalazine	TABLET, DELAYED RELEASE;ORAL	007073-002	Apr 6, 1983	AB	RX	Yes	Yes

Azulfidine Market Dynamics, Patent Status, Competition, and Financial Trajectory

Last updated: October 15, 2026

Azulfidine is Pfizer’s branded formulation of sulfasalazine, an established anti-inflammatory and disease-modifying antirheumatic drug used mainly for ulcerative colitis and rheumatoid arthritis. Its commercial profile is mature and largely genericized: regulatory exclusivity has expired, meaningful U.S. patent barriers are absent, and Pfizer does not report Azulfidine revenue as a separate product. Financial performance therefore depends on residual brand demand, generic pricing, supply continuity, and prescribing in inflammatory bowel disease and rheumatology rather than on new patent-protected growth.

What is Azulfidine and how is it used?

Azulfidine contains sulfasalazine, a 5-aminosalicylate-related prodrug that is metabolized in the colon to sulfapyridine and 5-aminosalicylic acid. The product is available in immediate-release tablets and delayed-release enteric-coated tablets marketed as Azulfidine EN-tabs.

Product	Active ingredient	Main indications	Common strength
Azulfidine	Sulfasalazine	Ulcerative colitis, rheumatoid arthritis	500 mg tablet
Azulfidine EN-tabs	Sulfasalazine delayed-release	Ulcerative colitis, rheumatoid arthritis	500 mg delayed-release tablet
Generic sulfasalazine	Sulfasalazine	Same broad indications	500 mg and other strengths, depending on market

The drug’s clinical value is highest where low cost, long treatment experience, and oral administration matter. It is less competitive in Crohn’s disease, where sulfasalazine has limited utility, and in moderate-to-severe inflammatory disease increasingly treated with biologics, targeted synthetic drugs, or newer oral immunomodulators.

The U.S. prescribing label identifies ulcerative colitis and rheumatoid arthritis as principal indications. Sulfasalazine is also used in some markets for other inflammatory arthritides, subject to local approval and clinical practice. (Pfizer, 2023; U.S. Food and Drug Administration, 2024a)

When does Azulfidine lose exclusivity?

Azulfidine has already lost market exclusivity. Sulfasalazine is an old small-molecule active ingredient, and generic versions have been available for many years.

Exclusivity category	Azulfidine status
New chemical entity exclusivity	Expired
Orphan-drug exclusivity	None identified for the core product
Pediatric exclusivity	No current protection identified
U.S. patent exclusivity	Expired or commercially irrelevant
Generic competition	Established
Biosimilar exposure	Not applicable

Sulfasalazine predates the modern U.S. Hatch-Waxman framework. Its foundational intellectual-property protection expired long before the current commercial period. Current competition is therefore governed by abbreviated new drug applications, manufacturing capacity, product availability, reimbursement, and brand retention rather than patent barriers.

What patents protect Azulfidine?

No currently material patent estate protects the active ingredient or ordinary tablet formulation of Azulfidine in the United States.

The relevant protection categories are:

1. Active ingredient patents. Sulfasalazine is an historic compound. Any original composition-of-matter rights expired decades ago.
2. Immediate-release formulation patents. No commercially meaningful current patent barrier is associated with the standard 500 mg tablet.
3. Delayed-release formulation patents. Enteric coating and release-control concepts can be patentable in principle, but no current Azulfidine patent position appears to block generic sulfasalazine delayed-release tablets.
4. Method-of-use patents. No active, commercially significant method-of-use patent is known to prevent generic use for the labeled indications.
5. Manufacturing patents. Process patents could affect individual suppliers, but they do not provide market exclusivity for the established product unless tied to a protected and essential manufacturing route.

What is the Orange Book status of Azulfidine?

The FDA Orange Book is relevant to approved prescription products and listed patents. Azulfidine’s commercial position does not depend on a live Orange Book patent listing that would delay generic entry. The product has been exposed to generic substitution for years. Orange Book records should be checked by NDA and presentation because brand and generic product listings can change with sponsor, marketing, or discontinuation status. (U.S. Food and Drug Administration, 2024b)

How many patents cover Azulfidine?

No currently material U.S. patent portfolio appears to cover Azulfidine as a market-blocking product. The effective count of blocking patents is therefore zero for ordinary commercial purposes.

This does not mean that every sulfasalazine-related patent in every jurisdiction has expired or that no later patent can exist. It means that the commercial product is not protected by a credible, active exclusivity position comparable to newer small-molecule medicines.

Patent strength is low because:

• the active ingredient is old;
• generic manufacturers can use established synthetic routes;
• the principal dosage forms are conventional;
• the product has no device or delivery platform creating a separate barrier;
• treatment uses are long established;
• generic substitution is accepted in routine practice.

Are there Paragraph IV challenges to Azulfidine?

A current Paragraph IV litigation strategy is unlikely to be commercially important for Azulfidine because generic sulfasalazine entered long ago. Paragraph IV certifications are primarily relevant when a listed patent remains active and generic entry is being attempted before patent expiry.

The likely competitive pathway is ordinary generic approval under an ANDA, with bioequivalence and pharmaceutical equivalence requirements. A later generic entrant would not need to overcome a meaningful modern patent estate if no blocking patent is listed for the relevant presentation.

No major current Paragraph IV case is central to the Azulfidine market based on the product’s mature status. Litigation risk is more likely to involve manufacturing, supply, labeling, product liability, or commercial contracting than patent invalidity.

What formulations are protected by Azulfidine patents?

No active formulation patent is known to provide meaningful market protection for the standard Azulfidine products.

Immediate-release tablets

Immediate-release sulfasalazine tablets are technically straightforward. Competition is based on API sourcing, tablet manufacture, quality control, distribution, and reimbursement.

Delayed-release tablets

Azulfidine EN-tabs use enteric coating to delay release until the product reaches the intestinal tract. Delayed release creates higher manufacturing requirements than an ordinary tablet, including coating uniformity, dissolution testing, stability control, and batch consistency. These requirements can produce supply or quality barriers, but they are not equivalent to patent exclusivity.

A generic delayed-release product may face greater development and manufacturing complexity than an immediate-release product. That can limit the number of reliable suppliers even after patents expire. The result is a possible supply-based advantage for an established brand without a legal monopoly.

What is the FDA regulatory status of Azulfidine?

Azulfidine is an FDA-approved prescription drug. The product is regulated as an established small-molecule oral medicine, not as a biologic.

FDA-related commercial issues include:

• continued compliance with current good manufacturing practices;
• maintenance of approved labeling;
• facility inspection outcomes;
• drug-supply continuity;
• postmarketing safety reporting;
• generic ANDA approvals for equivalent presentations.

Sulfasalazine has recognized safety risks, including hypersensitivity reactions, blood dyscrasias, hepatic injury, renal effects, and gastrointestinal intolerance. Monitoring and contraindications remain relevant to prescribing and product liability. The label also identifies limitations and adverse reactions associated with sulfapyridine exposure. (Pfizer, 2023)

How does Azulfidine compare with competing drugs?

Azulfidine competes across two distinct markets: conventional therapy for ulcerative colitis and conventional disease-modifying therapy for rheumatoid arthritis.

Competitive area	Azulfidine position	Main alternatives	Commercial effect
Mild-to-moderate ulcerative colitis	Low-cost oral option, particularly in selected colonic disease	Mesalamine, balsalazide, olsalazine, corticosteroids	Generic mesalamine and other 5-ASA products limit pricing power
Rheumatoid arthritis	Established conventional DMARD	Methotrexate, leflunomide, hydroxychloroquine, biologics, JAK inhibitors	Newer therapies reduce use in patients needing stronger disease control
Moderate-to-severe inflammatory bowel disease	Limited role	Anti-TNF drugs, vedolizumab, ustekinumab, IL-23 drugs, JAK inhibitors	Biologic and targeted therapies capture high-value treatment segments
Cost-sensitive care	Competitive	Other low-cost generics	Price and availability are more important than brand identity

Azulfidine’s strongest commercial defense is not clinical exclusivity. It is familiarity, low acquisition cost, established dosing, and use in patients for whom a conventional therapy is clinically appropriate.

Which companies compete with Azulfidine?

The market includes Pfizer’s branded Azulfidine products and multiple generic sulfasalazine suppliers. Generic availability varies by country and presentation. In the U.S., supplier participation can change because of discontinuations, manufacturing constraints, shortages, and commercial decisions.

Relevant competitive groups include:

• Pfizer, as the historical and branded Azulfidine supplier;
• generic manufacturers with approved sulfasalazine tablets;
• contract manufacturers and API suppliers;
• distributors and pharmacy benefit channels;
• manufacturers of alternative 5-ASA products;
• manufacturers of biologic and targeted immunology products.

The competitive landscape is fragmented at the generic level and concentrated among larger manufacturers of alternative inflammatory-disease therapies.

What is the financial trajectory for Azulfidine?

Pfizer does not publicly disclose standalone Azulfidine revenue in its reported product tables. Any product-specific sales estimate must therefore be inferred from prescription volume, channel data, price, geography, and brand-versus-generic share.

The financial trajectory is best characterized as mature, low-growth, and declining in strategic importance.

Financial driver	Expected effect on Azulfidine
Generic substitution	Reduces branded volume and net price
Low-cost treatment demand	Supports baseline unit volume
Brand loyalty and physician familiarity	Preserves some residual branded demand
Retail reimbursement pressure	Compresses net realized price
Delayed-release manufacturing complexity	Can support temporary pricing or supply resilience
New biologic and targeted therapies	Reduces use in advanced disease
Lack of patent protection	Prevents premium pricing and market exclusivity
Pfizer portfolio prioritization	Limits investment in brand expansion

Revenue is likely to be driven more by price-volume erosion than by prescription growth. Unit demand may remain stable in some chronic-care segments, but net sales can fall as payers substitute generic products and pharmacies dispense lower-cost equivalents.

Revenue exposure for Pfizer

Azulfidine is unlikely to have material exposure to Pfizer’s consolidated financial results relative to the company’s major innovative medicines, vaccines, and established products. The product’s commercial importance is more relevant to:

• continuity of supply;
• legacy portfolio management;
• manufacturing utilization;
• generic and branded channel economics;
• patient access in low-cost treatment settings.

A supply interruption could affect patients and competitors disproportionately to its contribution to Pfizer’s total revenue.

What generic entry risks exist?

Generic entry is no longer a future risk. It is the established market structure.

The remaining risks are operational and commercial:

1. Supplier withdrawal. A small number of manufacturers may create vulnerability if one exits.
2. API concentration. Dependence on limited sulfasalazine API sources can affect availability.
3. Delayed-release quality failures. Coating or dissolution problems can disrupt supply.
4. Contracting pressure. Pharmacy benefit managers can shift volume rapidly among suppliers.
5. Shortage-driven price spikes. Temporary shortages can raise acquisition costs without creating durable brand value.
6. Therapeutic substitution. Physicians may use mesalamine or other agents when coverage or tolerability favors those products.

Generic competition is therefore a continuing margin risk, while manufacturing complexity can produce intermittent supply protection.

What patent litigation affects Azulfidine?

No major active patent litigation appears to define the Azulfidine market. The absence of a live patent dispute is consistent with the product’s age and genericized status.

Potential disputes would more likely involve:

• ANDA-related issues for a new presentation;
• trade dress or trademark use;
• product liability;
• manufacturing defects;
• supply agreements;
• distributor or rebate arrangements;
• regulatory enforcement.

Trademark rights in the Azulfidine name may remain relevant even though the drug’s composition and formulation patents do not. Trademark protection does not prevent generic manufacturers from selling sulfasalazine under their own names.

Are there licensing deals involving Azulfidine?

No major recent licensing transaction appears to be central to Azulfidine’s commercial trajectory. The product is a mature marketed medicine rather than a development-stage asset.

Any commercial transfer would likely involve:

• a brand divestiture;
• a regional marketing agreement;
• a manufacturing or supply contract;
• a portfolio transaction involving multiple established products.

A transaction involving Azulfidine alone would be more likely to reflect manufacturing or portfolio rationalization than a growth-oriented licensing strategy.

Is there biosimilar risk for Azulfidine?

Biosimilar risk is not applicable. Sulfasalazine is a chemically synthesized small molecule, not a biologic. Competitive erosion occurs through generic substitution and therapeutic alternatives, not through biosimilar approval.

The relevant FDA pathway is the ANDA route for chemically equivalent generic products, not the abbreviated biologics pathway under the Public Health Service Act.

What is the geographic coverage of Azulfidine?

Azulfidine’s commercial presence is strongest in markets with established sulfasalazine use and regulated prescription distribution. Brand availability can differ by country because of:

• national marketing authorization;
• local sponsor ownership;
• reimbursement rules;
• generic penetration;
• product discontinuation decisions;
• brand naming conventions;
• supply and import requirements.

In many markets, sulfasalazine is sold primarily as a generic. The brand name has limited global pricing power because treatment guidelines and reimbursement systems often favor low-cost conventional agents.

What is the likely generic launch scenario?

A new generic entrant would not face a conventional patent cliff. The market would instead follow a supply-entry model:

Scenario	Likely commercial outcome
One additional immediate-release generic	Lower prices and modest share redistribution
One additional delayed-release generic	Greater impact if supply is constrained
Multiple entrants	Rapid price compression and reduced brand share
Supplier failure after entry	Temporary shortage and possible price rebound
Strong payer substitution	Accelerated generic uptake
Limited pharmacy stocking	Delayed practical access despite regulatory approval

The most valuable competitive position would come from reliable supply, low manufacturing cost, and broad wholesaler access rather than patent ownership.

Key Takeaways

• Azulfidine is Pfizer’s branded sulfasalazine product, including immediate-release and delayed-release tablets.
• U.S. composition, formulation, and method-of-use exclusivity has expired or is not commercially material.
• The product is exposed to long-standing generic competition.
• No meaningful current Paragraph IV patent campaign or patent litigation appears to define the market.
• Azulfidine is not a biologic and has no biosimilar risk.
• Pfizer does not separately disclose Azulfidine revenue, so product-specific financial performance cannot be read directly from public company filings.
• The financial trajectory is mature and likely shaped by generic substitution, low pricing, supply reliability, and therapeutic displacement.
• Manufacturing complexity, especially for delayed-release tablets, may create supply barriers without creating legal exclusivity.
• The product remains commercially relevant in cost-sensitive ulcerative colitis and conventional rheumatology treatment, but it is not a major growth asset.

FAQs About Azulfidine Market and Patent Economics

Does Azulfidine still have patent protection?

No commercially meaningful U.S. patent protection is known to block generic sulfasalazine entry. The active ingredient and conventional formulations are long established.

Is Azulfidine the same as generic sulfasalazine?

The active ingredient is the same, but inactive ingredients, manufacturing site, tablet design, labeling, and release characteristics can differ. Generic substitution depends on the approved product and local pharmacy rules.

Why might patients still receive branded Azulfidine after generic entry?

Reasons can include prescriber preference, pharmacy inventory, patient tolerance of a specific formulation, payer contracting, historical use, or differences between immediate-release and delayed-release products.

Can a new formulation of sulfasalazine obtain patent protection?

A genuinely novel formulation, delivery system, or manufacturing process could potentially receive a patent if it satisfies statutory patentability requirements. A patent would need to provide a meaningful technical distinction from established sulfasalazine products.

Does Pfizer disclose Azulfidine sales separately?

Pfizer’s public financial reporting does not generally provide a standalone revenue line for Azulfidine. Its sales are embedded within broader product or portfolio reporting, if reported at all.

References

1. Pfizer Inc. (2023). Azulfidine and Azulfidine EN-tabs prescribing information. Pfizer labeling repository.

2. U.S. Food and Drug Administration. (2024a). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/

3. U.S. Food and Drug Administration. (2024b). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book

4. U.S. Food and Drug Administration. (2024c). Electronic Orange Book patent and exclusivity information. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm

5. Pfizer Inc. (2024). Annual report and Form 10-K. Pfizer investor relations.

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