Last updated: October 4, 2026

Pemoline is a discontinued central nervous system stimulant formerly marketed in the United States as Cylert by Abbott Laboratories for attention-deficit/hyperactivity disorder (ADHD). Its commercial decline resulted from severe, sometimes fatal, liver toxicity, regulatory restrictions, generic competition, and the availability of safer ADHD therapies. The U.S. market effectively ended in 2005 after FDA action and manufacturer withdrawal. Pemoline has no meaningful current U.S. revenue base, no active Orange Book exclusivity, and no conventional biosimilar or Paragraph IV opportunity.

What was pemoline, and what was it used for?

Pemoline was a synthetic stimulant indicated primarily for ADHD. It was available in tablet form, including 18.75 mg, 37.5 mg, and 75 mg strengths. The brand product was Cylert.

Pemoline differed pharmacologically from amphetamine and methylphenidate products. It had a relatively long duration of action and was once considered useful for patients requiring once-daily treatment. The drug was also associated with abuse and dependence concerns, although its market withdrawal was driven mainly by hepatotoxicity rather than by diversion risk.

The FDA approved Cylert in 1975. Generic pemoline products later entered the market after the relevant product and regulatory exclusivity periods ended. By the late 1990s and early 2000s, pemoline competed with established stimulant products such as Ritalin, Concerta, Dexedrine, Adderall, and later Vyvanse, as well as nonstimulants such as atomoxetine.

When did pemoline lose exclusivity and patent protection?

Pemoline lost meaningful U.S. market exclusivity decades before its withdrawal. The product was approved in 1975, and any original compound or formulation patent protection would have expired well before the 2000s. The commercial market was therefore genericized long before regulatory action ended distribution.

Commercial attribute	Pemoline status
U.S. brand	Cylert
Original U.S. sponsor	Abbott Laboratories
U.S. approval	1975
Dosage forms	Tablets
Generic availability	Yes, before withdrawal
Current U.S. patent exclusivity	None of commercial significance
Current Orange Book exclusivity	None
Current U.S. marketed product	None
Biosimilar pathway	Not applicable

Pemoline’s patent estate was not the principal commercial barrier. The product’s value was based on historical regulatory approval, physician familiarity, and manufacturing authorization rather than enforceable patent exclusivity.

What is the Orange Book status of pemoline?

Pemoline has no active commercial Orange Book position supporting a current U.S. branded or generic market. FDA’s Orange Book is relevant to approved drug applications and listed patents, but it does not preserve market rights after a product has been withdrawn and its applications are no longer commercially active.

The former Cylert product and generic pemoline applications are not current growth assets. Any historical Orange Book listings would have expired, been delisted, or become commercially irrelevant after market withdrawal. There is no current reference-listed drug strategy comparable to an active small-molecule product with patent-term or regulatory-exclusivity exposure.

Why was pemoline withdrawn from the market?

The decisive market event was pemoline’s association with serious liver injury. FDA labeling warned about hepatic failure, including cases requiring transplantation or resulting in death. The risk was difficult to manage because clinically significant liver injury could occur without a reliable early-warning signal.

In 1996, FDA strengthened warnings and recommended baseline and periodic liver-function testing. FDA later concluded that the risk-benefit profile was unfavorable in view of the availability of alternative ADHD therapies. Abbott discontinued Cylert in the United States, and FDA announced withdrawal actions affecting pemoline products in 2005.[1]

The withdrawal was not a normal patent-expiration event. It was a safety-driven exit from a mature generic market.

What was the financial trajectory of pemoline?

Pemoline’s financial trajectory followed four stages:

Initial commercialization: Cylert entered the ADHD market as an alternative stimulant with long-duration dosing.
Generic erosion: Generic competition reduced brand pricing power and shifted volume away from Abbott.
Safety-driven contraction: Liver toxicity warnings reduced prescribing and increased monitoring costs.
Market exit: Abbott discontinued the brand, and the remaining generic market disappeared after regulatory and commercial withdrawal.

Public filings do not provide a consistent, standalone revenue series for Cylert or generic pemoline across its full commercial life. Abbott reported product categories and broader pharmaceutical results rather than a complete historical product-level revenue record for Cylert. As a result, a defensible dollar-by-dollar revenue curve cannot be established from public company reporting.

The commercial conclusion is clear even without a precise revenue series: pemoline was a low-value, mature product by the time safety restrictions intensified. Generic pricing, limited physician adoption, monitoring requirements, and competing ADHD medicines reduced its economic value. The liver-risk profile also created liability and pharmacovigilance costs that were disproportionate to the product’s remaining revenue opportunity.

How did pemoline compare with competing ADHD drugs?

Pemoline competed in a crowded ADHD market where alternative therapies had stronger commercial positions and, in several cases, better-established safety profiles.

Drug or class	Principal commercial position relative to pemoline
Methylphenidate	Established first-line stimulant class with multiple immediate- and extended-release products
Amphetamine salts	Strong branded and generic presence, including Adderall
Dexmethylphenidate	Branded and generic stimulant alternative
Atomoxetine	Nonstimulant option with a different safety and abuse profile
Guanfacine and clonidine	Nonstimulant or adjunctive ADHD therapies
Lisdexamfetamine	Branded extended-release stimulant with substantial commercial adoption
Pemoline	Discontinued because of severe hepatotoxicity

Pemoline had one commercial advantage: a relatively long duration of action. That benefit was insufficient to offset liver toxicity and the availability of other once-daily or extended-release products.

What formulation patents protected pemoline?

No active formulation patent is commercially relevant to pemoline in the United States. Historical products were conventional oral tablets rather than complex delivery systems, depot injections, transdermal systems, or biologic formulations.

Pemoline did not develop the type of secondary patent estate commonly associated with modern lifecycle management, such as:

Extended-release delivery systems
Abuse-deterrent formulations
New salts or crystalline forms
Pediatric liquid formulations
Combination products
Device-based administration
Method-of-use patents for new indications

The absence of a durable formulation strategy limited the sponsor’s ability to defend the product after basic patent protection and regulatory exclusivity ended.

What method-of-use patents covered pemoline?

No active method-of-use patent has meaningful commercial relevance today. Historical use centered on ADHD, and the drug did not establish a major new indication capable of extending its lifecycle.

Method-of-use protection would also have faced practical limitations. Physicians could select competing stimulants and nonstimulants for the same condition, while the liver-safety warnings constrained the addressable market. A new-use strategy would not have resolved the fundamental safety issue.

Were there Paragraph IV challenges involving pemoline?

Pemoline is not a current Paragraph IV litigation opportunity. Generic entry occurred after the product had matured, and no active patent estate now blocks an ANDA applicant.

Historical generic filings may have involved patent certifications, but those events no longer affect market access. There is no current commercial dispute comparable to an active Paragraph IV challenge against a branded ADHD drug.

Litigation issue	Current assessment
Active Paragraph IV litigation	None of commercial significance
Patent-based generic delay	None
Active settlement restricting generic entry	None identified as commercially operative
Hatch-Waxman exposure	Historical only
Current launch blocker	Regulatory and commercial viability, not patent protection

What FDA regulatory status does pemoline have today?

Pemoline is not an active U.S. commercial ADHD therapy. The FDA withdrawal process followed years of safety warnings and declining clinical use. The product’s regulatory status should be distinguished from a simple discontinued brand: the market was removed because the risk-benefit profile no longer supported continued availability.

Pemoline was also subject to controlled-substance regulation in the United States. That status increased compliance obligations for prescribing, distribution, recordkeeping, and inventory controls. Controlled-substance classification did not create a durable commercial advantage.

What generic entry risks exist for pemoline?

Patent barriers do not create a meaningful generic-entry risk because there is no active commercial patent estate. The principal barriers are regulatory, clinical, and economic.

A company attempting to reintroduce pemoline would face:

FDA scrutiny of hepatic safety
Requirements for an approvable regulatory pathway
Potential need for extensive risk-management controls
Physician resistance because of historical liver toxicity
Competition from low-cost generic stimulants
Competition from branded extended-release products
Limited payer and formulary interest
Product-liability exposure
Manufacturing economics that would not support a conventional launch

A reintroduction would therefore be a regulatory-redevelopment project, not a standard patent-protected generic launch.

How strong is the pemoline patent estate?

The current patent estate is commercially weak to nonexistent. Pemoline has no meaningful blocking patents, no active exclusivity period, and no formulation platform that supports premium pricing.

Its historical intellectual-property position may have supported initial commercialization, but the commercial lifecycle ended through safety failure rather than through a successful transition to a protected specialty product. For investment, licensing, or acquisition analysis, the patent value should be treated as zero unless a separate jurisdiction contains an unusual surviving right, which would not change the U.S. commercial assessment.

What licensing deals and settlement agreements affected pemoline?

No material current licensing transaction or settlement agreement drives pemoline’s market position. Abbott was the principal historical U.S. brand sponsor, while generic manufacturers supplied the later market.

There is no known active licensing structure that transfers pemoline revenue, preserves market exclusivity, or supports a current development program. Any historical generic licensing or supply arrangements would have no identifiable effect on present U.S. market value.

What patent litigation affects pemoline?

No active U.S. patent litigation materially affects pemoline. The relevant legal event was FDA withdrawal and commercial discontinuation rather than a patent dispute.

The product has no current branded-generic contest, no active infringement case of commercial significance, and no settlement-based launch restriction. Litigation risk is more relevant to historical product-liability exposure than to intellectual-property enforcement.

What is the geographic market coverage for pemoline?

Pemoline’s commercial availability has contracted sharply by jurisdiction. The United States market ended in 2005. Other countries either withdrew pemoline, restricted it heavily, or ceased routine commercial distribution because of the same liver-safety concerns and the availability of alternatives.

Any residual overseas product status should not be treated as a broad global market. Pemoline lacks the international commercial infrastructure, active sponsor base, and regulatory momentum associated with a current pharmaceutical asset.

Key Takeaways

Pemoline was a stimulant for ADHD marketed in the United States as Cylert.
FDA approved the product in 1975.
Generic competition eroded commercial value before withdrawal.
Severe liver toxicity, including hepatic failure and death, drove the U.S. market exit.
Abbott discontinued Cylert, and FDA withdrawal actions followed in 2005.
No active U.S. Orange Book exclusivity or commercially relevant patent estate remains.
There is no current Paragraph IV, biosimilar, or patent-settlement opportunity.
Public filings do not provide a reliable standalone lifetime revenue series.
Any reintroduction would face major safety, regulatory, liability, and market-access barriers.
Pemoline has no meaningful current pharmaceutical investment value based on U.S. market rights.

FAQs About Pemoline Market and Patent Status

Is pemoline still available in the United States?

No. Pemoline is not an active U.S. commercial ADHD product. Cylert and generic pemoline products were withdrawn after serious liver-safety concerns.

Did pemoline have generic competitors?

Yes. Generic pemoline products were available before the market was withdrawn. Generic competition reduced pricing power and accelerated the decline of the branded product.

Could a company launch generic pemoline today?

Patent protection would not be the principal obstacle. The main barriers would be FDA safety requirements, hepatic-risk management, liability exposure, weak physician demand, and competition from established ADHD therapies.

Was pemoline a biologic requiring biosimilar competition?

No. Pemoline was a conventional small-molecule oral drug. Biosimilar rules do not apply.

What caused pemoline’s commercial failure?

The primary cause was severe hepatotoxicity. Generic erosion, alternative ADHD medicines, controlled-substance compliance, monitoring burdens, and declining clinical use compounded the safety problem.

References

U.S. Food and Drug Administration. (2005). Withdrawal of approval of new drug applications for pemoline products. FDA Federal Register notices and drug safety communications.
U.S. Food and Drug Administration. (1996). Cylert (pemoline) labeling changes and liver-function monitoring recommendations. FDA Drug Safety Information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Orange Book.
U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs. FDA database.
U.S. Drug Enforcement Administration. (2024). Controlled substances schedules. U.S. Department of Justice.

US Patents:	0
Applicants:	6
NDAs:	8
Raw Ingredient (Bulk) Api Vendors:	33
Clinical Trials:	5
Patent Applications:	4,430
DailyMed Link:	PEMOLINE at DailyMed

Sponsor	Phase
Medical University of Vienna	Phase 2
California Pacific Medical Center Research Institute	Phase 2
Sheba Medical Center	N/A

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Actavis Elizabeth	PEMOLINE	pemoline	TABLET, CHEWABLE;ORAL	075678-001	Jul 26, 2000		DISCN	No	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
Watson Labs	PEMOLINE	pemoline	TABLET;ORAL	075287-001	Jun 13, 2001		DISCN	No	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
Fosun Pharma	PEMOLINE	pemoline	TABLET;ORAL	075286-002	Jun 30, 1999		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

PEMOLINE Drug Patent Profile

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Pemoline Market Dynamics, Patent Status, FDA Withdrawal, and Financial Trajectory