Last updated: September 8, 2026
Nefazodone hydrochloride is a mature, low-volume generic antidepressant with limited commercial relevance in the United States. The branded product, Serzone, was withdrawn from the U.S. market after declining sales, while concerns about rare but severe liver toxicity sharply reduced prescribing. Nefazodone has no biosimilar exposure, no meaningful current branded revenue base, and limited publicly reported financial data. Its remaining market value is concentrated in niche generic supply, clinical familiarity, and possible repositioning research rather than conventional branded pharmaceutical sales.
What is the current FDA status of nefazodone hydrochloride?
Nefazodone hydrochloride received U.S. Food and Drug Administration approval in 1994 as an oral antidepressant. It is a serotonin-norepinephrine modulating agent indicated for major depressive disorder.
The original U.S. branded product was Serzone, commercialized by Bristol-Myers Squibb. The product was later discontinued in the United States. The FDA determined that the discontinuation was not based on a finding that nefazodone was unsafe or ineffective for its approved use, although the drug’s hepatotoxicity risk materially affected prescribing and commercial demand (FDA, 2004).
Nefazodone labeling contains a prominent warning regarding potentially life-threatening hepatic failure. The label identifies symptoms requiring evaluation, including jaundice, anorexia, gastrointestinal complaints, malaise, and abnormal liver function tests. The risk is rare but commercially important because alternative antidepressants with less prominent liver-safety concerns are widely available (DailyMed, 2023).
FDA regulatory milestones
| Milestone |
Date or status |
| Initial U.S. approval |
1994 |
| Original U.S. brand |
Serzone |
| Dosage forms |
Immediate-release tablets |
| Common strengths |
50 mg, 100 mg, 150 mg, 200 mg, 250 mg |
| Key safety issue |
Severe hepatotoxicity, including hepatic failure |
| Branded U.S. discontinuation |
Early 2000s |
| Current commercial position |
Limited generic and specialty availability |
| Biosimilar status |
Not applicable |
The product should not be confused with newer antidepressants such as vilazodone, vortioxetine, desvenlafaxine, or brexpiprazole. Those products have different mechanisms, patent estates, and commercial positions.
When did nefazodone lose exclusivity and patent protection?
Nefazodone’s core U.S. market exclusivity expired before the major generic-entry period of the early 2000s. The drug is now a legacy small-molecule product rather than a patent-protected branded therapy.
Publicly relevant commercial protection has ended. Current economic barriers are manufacturing, regulatory maintenance, pharmacovigilance, market size, and supplier economics rather than enforceable composition-of-matter exclusivity.
What patents protect nefazodone hydrochloride?
No active composition-of-matter patent is generally recognized as a current barrier to generic nefazodone hydrochloride supply in the United States. Historical patents covering nefazodone or its pharmaceutical use are expired or commercially immaterial.
The practical intellectual-property position is:
| IP category |
Current commercial relevance |
| Active ingredient patent |
No material blocking protection |
| Salt or polymorph protection |
No known current barrier of market significance |
| Formulation patents |
No meaningful current exclusivity identified |
| Method-of-use patents |
No current branded protection of commercial importance |
| Manufacturing patents |
Potentially relevant to individual suppliers but not a broad market barrier |
| Regulatory exclusivity |
Expired |
| Orange Book patent protection |
No current branded patent moat of practical importance |
Because nefazodone is an established small molecule, an applicant generally competes through an abbreviated new drug application pathway rather than a 505(b)(2) product strategy, unless the applicant develops a materially different formulation, dosage form, or clinical use.
What is the Orange Book status of nefazodone?
Nefazodone has no active U.S. branded Orange Book position comparable to products with continuing innovator commercialization. Historical listings may remain relevant for regulatory records, discontinued-product review, and abbreviated application history, but they do not create a current market monopoly.
The key distinction is between an FDA product record and an active commercial listing. A drug can remain visible in FDA databases after the branded product has been discontinued. That database presence does not establish ongoing sales, enforceable patent protection, or active manufacturer support.
The FDA’s discontinued-drug framework is important in this case. The agency has treated the Serzone discontinuation as a commercial discontinuation rather than a withdrawal from sale for reasons of safety or effectiveness. That classification can affect how subsequent generic applications are evaluated (FDA, 2004).
How strong is the nefazodone patent estate?
The current patent estate is weak from a commercial-defense perspective.
Nefazodone lacks the characteristics that support a strong modern pharmaceutical patent estate:
- No active core patent appears to block generic entry.
- No current branded formulation franchise dominates the market.
- No long-dated method-of-use program supports exclusivity.
- No biologic manufacturing platform creates technical barriers.
- No FDA-recognized pediatric or orphan exclusivity remains commercially relevant.
Manufacturing know-how can still matter. A supplier must control validated synthesis, impurity specifications, analytical methods, stability data, and compliant production. Those factors may restrict the number of reliable manufacturers, but they do not operate like patent exclusivity.
What formulations are protected by nefazodone patents?
The commercially established product is an immediate-release oral tablet. No current high-value formulation franchise is associated with nefazodone hydrochloride.
Potential formulation opportunities could include modified-release tablets, lower-dose products, combination therapies, or delivery systems intended to reduce peak exposure. Each would require new clinical, pharmaceutical, and regulatory support. A reformulated product could potentially pursue 505(b)(2) approval if it relies in part on existing safety or efficacy findings while introducing a meaningful change.
The principal obstacle is not formulation patentability. It is the risk-benefit profile. A new formulation would need to demonstrate a commercial advantage that justifies development costs despite the availability of numerous generic antidepressants.
What generic entry risks exist for nefazodone hydrochloride?
Generic-entry risk is already realized rather than prospective. The product lost its branded franchise years ago, and any remaining market is structurally generic.
The principal risks to a generic supplier are different from those affecting a patented brand:
- Low and unstable demand can make production uneconomic.
- Hepatotoxicity concerns can limit physician prescribing.
- Pharmacies may prefer suppliers with dependable inventory and competitive pricing.
- A small patient population can produce periodic shortages if one manufacturer exits.
- Adverse-event reporting can increase compliance and liability costs.
- Reimbursement pressure can reduce net selling prices below sustainable levels.
For a new entrant, the major barrier is likely market unattractiveness rather than patent litigation. A generic company would need to determine whether expected volume supports FDA filing, validation, pharmacovigilance, inventory, and distribution costs.
Which companies are challenging nefazodone exclusivity?
No major current Paragraph IV challenge is central to the nefazodone market. The relevant competitive event was the historical genericization of Serzone after loss of branded exclusivity.
Generic manufacturers have included firms that supplied nefazodone tablets under abbreviated applications or distributor arrangements. Supplier participation has changed over time, and not every historical approval represents active commercial availability.
What is the Paragraph IV litigation status?
Nefazodone is not associated with an active, commercially material Paragraph IV litigation campaign comparable to protected products such as GLP-1 agonists, oncology drugs, or major immunology biologics.
Any historical Paragraph IV activity would have related to expired or displaced branded protection. Current entry disputes are more likely to concern FDA approval status, manufacturing compliance, product availability, or commercial contracting than patent validity.
What patent litigation affects nefazodone?
No material ongoing U.S. patent litigation is publicly associated with nefazodone hydrochloride as a commercial product. The absence of litigation is consistent with the drug’s age, low sales value, and lack of an active innovator franchise.
Potential disputes could still arise over:
- Abbreviated application certifications
- Product labeling and failure-to-warn claims
- Manufacturing specifications
- Supply contracts
- Trademark use involving historical Serzone branding
- Product liability relating to hepatic injury
These issues differ from patent litigation and should not be treated as evidence of a surviving exclusivity position.
How has the nefazodone market performed financially?
Nefazodone’s financial trajectory has four stages:
| Stage |
Market condition |
Financial effect |
| Launch and expansion |
Branded antidepressant introduction |
Revenue growth under Serzone |
| Peak commercial period |
Established antidepressant competition |
Meaningful but declining brand sales |
| Safety-driven contraction |
Reports and warnings concerning liver injury |
Prescribing and sales erosion |
| Post-brand period |
Generic, low-volume supply |
Limited revenue and low pricing power |
Bristol-Myers Squibb discontinued U.S. Serzone marketing after sales declined. The company’s decision removed the branded revenue stream and left the product dependent on generic demand. Public companies that supply generic nefazodone generally do not report product-level sales, margins, or volumes, so a reliable current market-size estimate is unavailable from public filings.
What is the revenue exposure?
Current revenue exposure is likely immaterial for diversified pharmaceutical companies. Nefazodone is not a major revenue driver for a large generic manufacturer unless a supplier has unusually concentrated exposure to the product.
The commercial economics are typical of a low-volume generic:
- Low average selling prices
- Limited promotional spending
- Weak ability to raise prices
- Small prescription base
- High sensitivity to manufacturing interruptions
- Limited return on new clinical investment
The product may generate intermittent revenue where supply is constrained, but that does not establish a durable growth market.
How does nefazodone compare with competing antidepressants?
Nefazodone competes against substantially larger and better-established categories, including selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, atypical antidepressants, and generic tricyclic products.
| Drug or class |
Commercial position |
Key comparison with nefazodone |
| Sertraline and fluoxetine |
Large generic SSRI markets |
Lower perceived safety and familiarity barrier for nefazodone |
| Venlafaxine and duloxetine |
Established generic SNRI markets |
Broader prescribing base and stronger clinical familiarity |
| Bupropion |
Large generic atypical antidepressant market |
Different adverse-effect and symptom profile |
| Mirtazapine |
Established generic product |
Competes in sleep and appetite-related prescribing |
| Vortioxetine |
Branded product with differentiated positioning |
Greater commercial investment and active innovation |
| Vilazodone |
Branded or limited generic competition depending on market |
More current commercial positioning |
| Nefazodone |
Niche legacy generic |
Hepatic safety concern and limited availability |
Nefazodone can remain clinically relevant for selected patients, particularly where prior treatment history or symptom profile supports its use. That clinical niche is insufficient to recreate a mass-market product.
Is there biosimilar risk for nefazodone?
No. Biosimilar risk does not apply because nefazodone hydrochloride is a chemically synthesized small molecule, not a biologic.
The relevant competition is generic substitution. Regulatory and commercial analysis should use abbreviated new drug application, ANDA, therapeutic equivalence, and generic supply concepts rather than biosimilar terminology.
What licensing deals involve nefazodone?
No significant current licensing transaction is associated with nefazodone hydrochloride. The historical commercial relationship centered on Bristol-Myers Squibb’s development and marketing of Serzone. The product no longer supports the type of licensing economics seen with protected assets, platform technologies, or specialty medicines.
A new licensing transaction would likely require a differentiated asset, such as a reformulated product, a new therapeutic indication, or a delivery technology. Rights to legacy nefazodone alone would have limited valuation.
What generic launch scenarios are plausible?
A conventional generic launch would have limited upside. The most plausible scenarios are:
- A supplier enters to address a temporary shortage.
- An existing manufacturer consolidates remaining demand.
- A specialty company develops a reformulated product for a defined population.
- A research sponsor investigates nefazodone for a new indication but does not pursue commercial development.
- The remaining U.S. supply contracts further if manufacturers exit.
A successful reformulation would face clinical-development costs, safety scrutiny, payer resistance, and competition from established antidepressants. The probability of a large commercial relaunch is low based on the product’s safety history and market maturity.
What manufacturing and geographic barriers affect nefazodone?
The active ingredient and finished tablets can be produced using conventional pharmaceutical manufacturing infrastructure. No biologic cell-line, device, cold-chain, or complex delivery barrier is required.
Geographic coverage is therefore determined mainly by:
- Local marketing authorization
- Manufacturer registration
- Pharmacovigilance obligations
- Product labeling
- Import controls
- Commercial demand
- Availability of qualified active pharmaceutical ingredient suppliers
Nefazodone’s geographic market is fragmented. A product may remain available in one jurisdiction while being discontinued in another because of safety labeling, commercial demand, or manufacturer decisions.
Key Takeaways
- Nefazodone hydrochloride is a mature, low-volume generic antidepressant.
- Serzone, the original branded product, was withdrawn from U.S. marketing after declining sales.
- Hepatotoxicity is the central clinical and commercial issue.
- No active patent estate appears to provide meaningful current market protection.
- Orange Book visibility does not imply active branded commercialization or enforceable exclusivity.
- Paragraph IV litigation and current patent disputes are not material market drivers.
- Biosimilar competition does not apply.
- Product-level revenue is not publicly disclosed by current suppliers.
- Generic economics are constrained by low demand, low pricing power, and supply volatility.
- Commercial upside would require a differentiated formulation or new indication, not conventional generic entry.
FAQs About Nefazodone Hydrochloride
Is nefazodone hydrochloride still available in the United States?
Limited generic availability may exist, but the product is no longer supported by the original Serzone brand. Availability can vary by manufacturer, wholesaler, pharmacy, and dosage strength.
Why was Serzone discontinued?
Bristol-Myers Squibb discontinued U.S. Serzone marketing after declining sales. The drug’s association with rare severe liver injury also reduced physician and patient demand. The FDA classified the discontinuation as commercial rather than a withdrawal for safety or effectiveness reasons.
Does nefazodone have a boxed warning?
Nefazodone labeling contains serious warnings concerning liver injury and hepatic failure. The product requires clinical attention to hepatic symptoms and risk factors.
Can a company launch a new nefazodone product without a patent license?
Expired core exclusivity generally means a company does not need a license to the original branded patent estate. It still must obtain FDA approval, satisfy current manufacturing standards, comply with labeling requirements, and address any new intellectual-property rights associated with a reformulation or new use.
Is nefazodone a commercial opportunity for generic manufacturers?
The opportunity is narrow. A manufacturer could benefit from supply shortages or a focused specialty strategy, but ordinary generic entry is unlikely to produce significant revenue because of low demand, limited pricing power, safety concerns, and competition from widely used antidepressants.
References
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DailyMed. (2023). Nefazodone hydrochloride tablet prescribing information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/
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U.S. Food and Drug Administration. (2004). FDA statement on the discontinuation of Serzone and generic nefazodone. U.S. Department of Health and Human Services. https://www.fda.gov/
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U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations: Orange Book. U.S. Department of Health and Human Services. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
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U.S. Food and Drug Administration. (2023). Discontinued drug product list. U.S. Department of Health and Human Services. https://www.fda.gov/drugs/drug-approvals-and-databases/discontinued-drug-product-list
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National Library of Medicine. (2023). Nefazodone. MedlinePlus. https://medlineplus.gov/druginfo/meds/a698006.html
