NARDIL Drug Patent Profile

Which patents cover Nardil, and what generic alternatives are available?

Nardil is a drug marketed by Parke Davis and is included in one NDA.

The generic ingredient in NARDIL is phenelzine sulfate. There are four drug master file entries for this compound. Three suppliers are listed for this compound. Additional details are available on the phenelzine sulfate profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Nardil

A generic version of NARDIL was approved as phenelzine sulfate by NOVEL LABS INC on December 8^th, 2010.

Summary for NARDIL

US Patents:	0
Applicants:	1
NDAs:	1
Finished Product Suppliers / Packagers:	2
Raw Ingredient (Bulk) Api Vendors:	53
Clinical Trials:	5
Drug Prices:	Drug price information for NARDIL
What excipients (inactive ingredients) are in NARDIL?	NARDIL excipients list
DailyMed Link:	NARDIL at DailyMed

See drug prices for NARDIL

Recent Clinical Trials for NARDIL

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

Sponsor	Phase
Boehringer Ingelheim	Phase 1
Liverpool Cancer Therapy Centre	Phase 1
The Canberra Hospital	Phase 1

See all NARDIL clinical trials

Pharmacology for NARDIL

Drug Class	Monoamine Oxidase Inhibitor
Mechanism of Action	Monoamine Oxidase Inhibitors

US Patents and Regulatory Information for NARDIL

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Parke Davis	NARDIL	phenelzine sulfate	TABLET;ORAL	011909-002	Approved Prior to Jan 1, 1982	AB	RX	Yes	Yes

Nardil Market Dynamics and Financial Trajectory: Phenelzine Patent Status, Generic Supply, and Commercial Outlook

Last updated: August 7, 2026

Nardil is the brand name for phenelzine sulfate, an irreversible monoamine oxidase inhibitor approved in the United States for major depressive disorder, particularly depression with atypical, neurotic, or nonendogenous characteristics and depression that has not responded adequately to other treatments.[1] Its commercial profile is defined by low prescription volume, generic substitution, limited manufacturer participation, supply interruptions, and the absence of meaningful remaining patent exclusivity.

Nardil does not have a separately reported public revenue stream. Pfizer, the historical brand owner, does not disclose Nardil sales in current financial filings, and generic manufacturers do not report phenelzine revenue by product. The commercial opportunity is therefore a small, specialized off-patent market rather than a conventional branded pharmaceutical franchise.

What is Nardil and how is phenelzine used?

Nardil contains phenelzine sulfate, an oral, nonselective and irreversible MAO-A and MAO-B inhibitor. The labeled strength is 15 mg per tablet.[1]

FDA-approved indication and dosing

The FDA label positions Nardil for patients with depression who have failed to respond to other antidepressants or who have atypical depressive symptoms.[1] The drug is generally reserved for later-line use because of:

• Hypertensive reactions associated with tyramine-containing foods
• Potentially severe interactions with serotonergic and sympathomimetic medicines
• Required washout periods between MAO inhibitors and many antidepressants
• Orthostatic hypotension and other tolerability limitations
• Dietary and medication-management requirements

The approved indication creates a narrow market compared with selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, atypical antidepressants, and newer adjunctive therapies.

Nardil versus other MAO inhibitors

Phenelzine competes most directly with tranylcypromine, sold historically as Parnate, and with selegiline formulations. Tranylcypromine is also an irreversible nonselective MAOI, while selegiline transdermal delivery provides a different administration route and, at lower doses, may reduce dietary restrictions.[2]

Drug	Active ingredient	Delivery	Commercial position	Main competitive issue
Nardil	Phenelzine sulfate	Oral tablet	Generic and legacy brand market	Low volume, supply and interaction burden
Parnate	Tranylcypromine sulfate	Oral tablet	Generic and legacy brand market	Similar specialist use and safety constraints
Emsam	Selegiline	Transdermal patch	Branded specialty product	Different delivery system and pricing structure
SSRIs/SNRIs	Multiple	Mostly oral	Mainstream first-line therapy	Larger clinical and commercial base

Nardil's differentiation is clinical familiarity among psychiatrists treating refractory depression. Its weakness is the operational burden imposed on patients and prescribers.

When did Nardil lose exclusivity?

Nardil lost meaningful market exclusivity decades ago. Phenelzine was first approved in the United States in 1961, placing the product well outside the term of any original composition-of-matter or basic pharmaceutical patent.[1]

Nardil patent expiration and exclusivity timeline

Event	Approximate timing	Commercial effect
FDA approval of Nardil	1961	Original branded market established
Original patent protection	Expired decades ago	No remaining basic compound exclusivity
Generic phenelzine development	Historical	Brand competition reduced
Current market	Generic and limited-source supply	Price and availability depend on manufacturers

No current patent term is known to provide Nardil with meaningful U.S. market exclusivity. Patent term restoration, pediatric exclusivity, and modern regulatory exclusivity provisions do not materially affect this legacy product.

What patents protect Nardil today?

No active U.S. composition, formulation, or method-of-use patent is known to protect Nardil as a commercially meaningful product. The principal intellectual-property barriers expired long ago with the underlying phenelzine compound and conventional tablet formulation.

Formulation patents

The conventional Nardil product is a 15 mg immediate-release oral tablet. This dosage form is technically simple relative to modified-release tablets, depot injections, transdermal systems, or complex biologics.

A later entrant could theoretically pursue patents covering:

• A modified-release phenelzine formulation
• A food-interaction mitigation system
• A transdermal or other nonoral delivery system
• A combination therapy
• A manufacturing process that improves stability or yield

Those concepts would require independent patentable subject matter and would not restore exclusivity to conventional phenelzine tablets. A new delivery system could create a separate product opportunity, but it would compete with the low-price generic tablet rather than replace its legal status.

Method-of-use patents

Nardil's core depression indication is long established. A new patent could potentially cover a narrowly defined patient population, dosing regimen, or combination therapy if supported by new clinical evidence and patentable claims. No broadly relevant active method-of-use patent is publicly established as the basis for current Nardil commercial protection.

What is the Orange Book status of Nardil?

Nardil is a legacy product whose commercial relevance comes from generic phenelzine rather than active brand exclusivity. FDA Orange Book records identify approved drug products and therapeutic-equivalence information, but an Orange Book listing does not itself create patent protection.[3]

Generic approval and therapeutic equivalence

Generic phenelzine products may be approved through abbreviated new drug applications when they meet FDA requirements for pharmaceutical equivalence and bioequivalence. The practical commercial outcome is generic substitution where state law, payer rules, and pharmacy inventory permit it.

The market is different from a high-volume generic category because:

• Prescriber demand is limited
• The product has a specialist prescriber base
• Pharmacy inventory may be inconsistent
• Few manufacturers may support the market at a given time
• A shortage at one manufacturer can affect national availability

Public Orange Book information does not provide a reliable estimate of total phenelzine revenue or market profitability.

Are there Paragraph IV challenges to Nardil?

No major, publicly prominent Paragraph IV litigation campaign involving phenelzine is known. The most likely reason is economic rather than legal: the product is old, generic, low volume, and not protected by a valuable contemporary patent estate.

Paragraph IV litigation normally arises when an ANDA applicant challenges a listed patent for a commercially important branded drug. That structure is largely absent for conventional phenelzine tablets. Any current generic entry would more likely involve routine ANDA approval, manufacturing transfer, or market re-entry than a high-value patent challenge.

Which companies are challenging or supplying Nardil?

The public commercial record does not support a stable list of long-term Nardil suppliers or a reliable ranking of current phenelzine manufacturers. Historical U.S. supply has involved the original brand owner and generic manufacturers, but supplier participation has changed over time.

Brand and generic landscape

Pfizer is associated with the historical Nardil brand. Current commercial activity is primarily generic and may involve contract manufacturing, authorized distribution, or temporary market participation. Manufacturer-level revenue, shipment volume, and market share are not separately disclosed in public annual reports.

The absence of a stable supplier base creates a more important competitive variable than patent ownership. In this market, a company with reliable active pharmaceutical ingredient procurement, validated tablet manufacturing, FDA-compliant packaging, and dependable distribution can obtain disproportionate commercial importance without holding exclusive IP.

How strong is the Nardil patent estate?

Nardil's patent estate is weak from a lifecycle-management perspective.

Patent category	Current strength	Assessment
Composition of matter	None of commercial significance	Expired
Conventional tablet formulation	Low	Old, technically straightforward dosage form
Method of use	Low	Core depression use is established
Manufacturing process	Potentially moderate in a narrow scope	Process claims would not block all generic production
New delivery system	Potentially moderate to high if novel	Would protect a redesigned product, not standard Nardil
Regulatory exclusivity	None of practical significance	Legacy product

The key barrier is not patent infringement risk. It is the cost of maintaining a reliable low-volume supply chain while meeting FDA quality requirements and managing limited demand.

What patent litigation affects Nardil?

No major current Nardil patent litigation is publicly identified as a material market event. The product's litigation risk is low compared with protected antidepressants, long-acting injectable products, and branded combination therapies.

Potential disputes would more likely concern:

• FDA manufacturing compliance
• Product quality or tablet dissolution
• Labeling and medication-guide obligations
• Supply contracts
• Distribution rights
• Trademark use for the Nardil brand
• Business interruption caused by manufacturing changes

These issues can affect availability without creating patent-based market exclusivity.

What is Nardil's FDA regulatory status?

Nardil remains an FDA-approved prescription product when marketed in accordance with an approved application and current labeling. The FDA label warns about serious interactions and dietary restrictions, which materially influence prescribing and patient monitoring.[1]

Regulatory risks

The principal regulatory risks are operational:

1. Maintaining cGMP compliance for a small-volume product.
2. Preserving reliable API sourcing.
3. Meeting stability and dissolution specifications.
4. Managing labeling for MAOI interactions and dietary restrictions.
5. Avoiding interruptions that force patients to switch therapies.

For a low-volume generic, a manufacturing deviation can have a larger market impact than a competitor's promotional campaign. The product's specialized use means some patients cannot switch easily to another therapy without clinical supervision.

What is Nardil's financial trajectory?

Nardil's financial trajectory is mature, fragmented, and low transparency.

Revenue exposure

No public company separately reports Nardil or phenelzine revenue in a way that permits a defensible product-level forecast. The brand's historical sales are not comparable with current generic revenue because generic pricing, manufacturer participation, and reimbursement arrangements differ materially.

The market's financial characteristics are likely to include:

• Low absolute revenue
• Low marketing expenditure
• High sensitivity to supply interruptions
• Limited pricing power where multiple generic suppliers are active
• Potential price spikes during constrained supply
• Uneven profitability by manufacturer
• Minimal value attributable to patent rights

A manufacturer can generate attractive contribution margins during a supply shortage, but that does not establish durable franchise value. Revenue can fall rapidly when another supplier restores inventory or when pharmacies substitute tranylcypromine or another antidepressant.

Demand trajectory

Long-term demand is structurally constrained by the availability of first-line antidepressants and newer treatments for treatment-resistant depression. Demand persists because a subgroup of patients responds to MAOIs after other therapies fail.

The likely demand pattern is stable to modestly declining in broad volume, with periodic increases in commercial value caused by shortages or price changes rather than by expanding diagnosis or new indications.

What generic entry risks exist for Nardil?

Conventional generic entry risk is already realized. The relevant risk is generic supply competition and product withdrawal, not a future patent cliff.

Generic launch scenarios

Scenario	Probability profile	Market effect
Multiple generic suppliers remain active	Base case	Low prices and limited manufacturer margins
One or two suppliers dominate	Material possibility	Higher prices and greater shortage exposure
Temporary manufacturer exit	Recurring operational risk	Pharmacy back orders and patient switching
New branded reformulation	Low probability	Could support premium pricing if clinically differentiated
New generic entrant	Possible but economically limited	More supply, lower prices, weak long-term returns

The market can support a new supplier only if the company can justify the regulatory, quality, and distribution costs of a low-volume product. The absence of patent barriers lowers entry costs legally, but limited demand raises the commercial hurdle.

How does Nardil compare with Parnate and Emsam?

Nardil competes in a narrow segment where prescribing decisions depend more on patient response and tolerability than on conventional brand promotion.

Factor	Nardil	Parnate	Emsam
Ingredient	Phenelzine	Tranylcypromine	Selegiline
Route	Oral	Oral	Transdermal
Patent position	Legacy, off-patent	Legacy, off-patent	Stronger branded-product positioning historically
Food restrictions	Significant	Significant	Dose-dependent and formulation-specific
Generic pressure	High	High	Lower for the patch
Manufacturing complexity	Low to moderate	Low to moderate	Higher than oral tablets
Commercial scale	Small	Small	Specialty branded market

Nardil's main advantage is its established role in treatment-resistant and atypical depression. Its main disadvantages are dietary restrictions, drug interactions, and inconsistent availability.

Are licensing deals associated with Nardil?

No major current licensing transaction is publicly established as a driver of Nardil's market value. Any historical rights transfers involving the brand do not create current exclusivity for conventional phenelzine tablets.

A licensing transaction could become relevant if a company developed:

• A novel phenelzine delivery system
• A controlled-release formulation
• A combination product
• A digital or monitoring platform tied to MAOI safety
• A new indication supported by clinical data

Without such a differentiated product, licensing value would likely be limited to manufacturing, distribution, or regional commercialization rights.

What geographic markets are relevant to Nardil?

The United States is the most commercially visible market because of FDA approval and the historical Nardil brand. Phenelzine or equivalent products may be available in other jurisdictions under different brand names, regulatory statuses, or supply arrangements.

Geographic commercial value is constrained by:

• Country-specific MAOI prescribing practices
• Local dietary and labeling requirements
• National reimbursement policy
• Generic registration status
• API and finished-dose supply
• Brand recognition among psychiatrists

U.S. FDA approval does not establish market access in Europe, Canada, Asia-Pacific, or Latin America. Each jurisdiction requires separate authorization or reliance on applicable regulatory pathways.

What manufacturing and IP barriers affect Nardil?

Manufacturing barriers are more important than patent barriers. A supplier must control API quality, tablet uniformity, packaging, stability, and distribution while operating at modest scale.

Potential manufacturing risks include:

• Limited API suppliers
• Low production runs
• Inventory inefficiency
• Specialized labeling and warning requirements
• Batch-release delays
• Product discontinuation economics
• Pharmacy-level stockouts

The commercial moat is therefore operational reliability. A company that can maintain consistent supply may gain prescriber and pharmacy preference, but that advantage is vulnerable to a lower-cost entrant or a manufacturing failure.

Key Takeaways

• Nardil is phenelzine sulfate, an FDA-approved irreversible MAOI for selected patients with depression.
• The product lost meaningful patent and regulatory exclusivity decades ago.
• No current patent estate is known to protect conventional Nardil tablets.
• No major Paragraph IV litigation or active patent dispute is publicly identified as a material market factor.
• Current commercial activity is primarily generic and low volume.
• Product-level revenue is not separately disclosed by Pfizer or generic manufacturers.
• Market value depends more on reliable manufacturing and distribution than on intellectual property.
• Demand is structurally limited but persistent among patients with treatment-resistant or atypical depression.
• Supply interruptions can produce temporary pricing power, but they do not establish durable franchise value.
• A commercially meaningful growth opportunity would require a differentiated formulation, delivery system, combination product, or new clinical use.

FAQs

Is Nardil still available in the United States?

Phenelzine may be available through generic channels, although pharmacy inventory and supplier participation can vary. The historical Nardil brand does not represent a major current branded franchise.

Is phenelzine protected by patents?

The original phenelzine compound and conventional tablet technology are long off-patent. New patents would need to cover a distinct formulation, delivery system, manufacturing process, or narrowly defined clinical use.

Why is Nardil difficult to find at pharmacies?

Nardil has low demand, a limited supplier base, and specialized manufacturing economics. Pharmacies may not routinely stock it and may need to order it from a wholesaler.

Can a generic company launch phenelzine without challenging a patent?

Yes. A generic applicant can pursue FDA approval through an ANDA without a Paragraph IV challenge when no relevant unexpired listed patent blocks approval.

Does Nardil have biosimilar competition?

No. Nardil is a small-molecule chemical drug, not a biologic. The relevant competitors are generic phenelzine products and other antidepressants, including generic tranylcypromine.

References

1. U.S. Food and Drug Administration. (2018). Nardil (phenelzine sulfate) tablets prescribing information. FDA labeling database.

2. U.S. Food and Drug Administration. (2023). Medication guide: Monoamine oxidase inhibitors and antidepressant treatment. FDA Drug Safety Communications and labeling resources.

3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. U.S. Department of Health and Human Services.

4. U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs database. U.S. Department of Health and Human Services.

5. Pfizer Inc. (2024). Annual report and Form 10-K. U.S. Securities and Exchange Commission.

DrugChatter Q&A for NARDIL

Novel labs nardil inactive ingredients?
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