pemoline - Profile

What are the generic sources for pemoline and what is the scope of freedom to operate?

Pemoline is the generic ingredient in two branded drugs marketed by Abbott, Actavis Elizabeth, Teva Pharms, Fosun Pharma, Mallinckrodt, Vintage Pharms, and Watson Labs, and is included in ten NDAs. Additional information is available in the individual branded drug profile pages.

Summary for pemoline

US Patents:	0
Tradenames:	2
Applicants:	7
NDAs:	10

US Patents and Regulatory Information for pemoline

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Abbott	CYLERT	pemoline	TABLET, CHEWABLE;ORAL	017703-001	Approved Prior to Jan 1, 1982		DISCN	No	No
Actavis Elizabeth	PEMOLINE	pemoline	TABLET, CHEWABLE;ORAL	075678-001	Jul 26, 2000		DISCN	No	No
Teva Pharms	PEMOLINE	pemoline	TABLET, CHEWABLE;ORAL	075555-001	Feb 18, 2000		DISCN	No	No
Abbott	CYLERT	pemoline	TABLET;ORAL	016832-001	Approved Prior to Jan 1, 1982		DISCN	No	No
Abbott	CYLERT	pemoline	TABLET;ORAL	016832-002	Approved Prior to Jan 1, 1982		DISCN	No	No
Abbott	CYLERT	pemoline	TABLET;ORAL	016832-003	Approved Prior to Jan 1, 1982		DISCN	No	No

Pemoline Investment Analysis: Patent Status, FDA Withdrawal, Market Fundamentals, and Generic Entry Risk

Last updated: August 1, 2026

Pemoline is not an investable commercial pharmaceutical asset in the United States. The central facts are regulatory withdrawal, severe hepatotoxicity, loss of market exclusivity, and the absence of a viable branded market. Pemoline was marketed primarily as Cylert for attention-deficit/hyperactivity disorder (ADHD) and narcolepsy, but the FDA requested its withdrawal in 2005 after reports of serious liver injury, including liver failure and death.[1][2]

The molecule has no meaningful remaining U.S. patent moat. Any historic composition, formulation, or manufacturing patents have expired or lost commercial relevance. The principal investment question is therefore not whether pemoline can defend a premium price. It is whether a company could lawfully and profitably redevelop the molecule despite its safety record. The risk-adjusted answer is unfavorable.

What is pemoline and how was it commercialized?

Pemoline is a central nervous system stimulant and oxazolidinedione derivative. It was sold in the United States under the brand name Cylert and in generic forms as tablets and chewable tablets. Abbott Laboratories was the original commercial sponsor of Cylert.[1]

Attribute	Pemoline
Primary indication	ADHD
Historical brand	Cylert
Original U.S. sponsor	Abbott Laboratories
Drug class	CNS stimulant
U.S. regulatory status	Withdrawn from commercial distribution
Historical dosage forms	Tablets and chewable tablets
Controlled-substance status	Schedule IV during U.S. marketing
Principal safety issue	Severe hepatotoxicity
Current branded-market status	No active U.S. commercial franchise
Biosimilar relevance	None

Pemoline had a pharmacologic profile distinct from amphetamine and methylphenidate. It was initially viewed as having lower abuse potential than traditional stimulants, but that perceived advantage did not offset its liver-safety liability.[1]

When did pemoline lose exclusivity and commercial protection?

Pemoline’s commercial exclusivity ended long before its U.S. withdrawal. The original product patents and any ordinary regulatory exclusivity associated with the historical approval are no longer commercially relevant. The molecule is old, chemically simple, and available through historical generic formulations.

The important commercial dates are:

Date	Event
1975	FDA approval of Cylert, according to historical FDA product information
1980s-1990s	Generic pemoline products entered the U.S. market
1996	FDA strengthened warnings concerning serious liver injury
1999	Abbott announced withdrawal of Cylert from the Canadian market
2005	FDA requested withdrawal of pemoline products from the U.S. market
2005 onward	U.S. commercial availability ended or became highly restricted

The patent estate should be treated as expired for investment analysis. No current U.S. composition-of-matter patent can reasonably be assumed to protect pemoline itself. Any patent-centered valuation would require evidence of a new, active patent on a differentiated formulation, prodrug, delivery system, or clinically superior use. The historical product does not provide that protection.

What is the FDA regulatory status of pemoline?

Pemoline is not a current mainstream FDA-approved commercial treatment for ADHD. The FDA’s 2005 action followed continued reports of serious liver injury despite labeling changes and monitoring requirements.[2]

The FDA concluded that the risk of liver failure outweighed the benefits of the drug for ADHD. The agency requested that manufacturers voluntarily withdraw pemoline products from the U.S. market. This was a risk-benefit decision rather than a patent or manufacturing decision.[2]

The historical labeling required liver-function monitoring and warned about potentially fatal hepatic injury. Those requirements created a significant operational burden:

• Baseline liver-function testing
• Periodic monitoring during treatment
• Discontinuation when liver abnormalities emerged
• Patient counseling regarding hepatic symptoms
• Limited tolerance for delayed diagnosis

A redevelopment program would face the historical safety record during every regulatory interaction. A sponsor would need to establish why a new formulation, dosing regimen, or patient-selection strategy materially changes the benefit-risk profile.

What patents protected pemoline and are any still enforceable?

The relevant historical IP consisted primarily of early chemical and pharmaceutical patents associated with pemoline and its formulations. Those rights are now expired or commercially exhausted.

Composition-of-matter patents

Pemoline was discovered and commercialized decades ago. Any foundational composition patent would have expired under the historical U.S. patent term rules or, at the latest, under the modern 20-year-from-filing framework. The molecule cannot support a new composition-of-matter exclusivity period merely because a company acquires or rebrands the historical product.

Formulation patents

Historical tablets and chewable tablets do not create a current patent barrier. A new formulation could theoretically support patent protection if it delivered a genuine technical improvement, such as:

• Controlled release
• Reduced hepatic exposure
• Improved pediatric tolerability
• A novel absorption profile
• A nonoral delivery system

A formulation patent would protect only the claimed formulation. It would not restore exclusivity to ordinary pemoline tablets or prevent all alternative formulations.

Method-of-use patents

New use claims could potentially cover a narrowly defined patient population or dosing regimen. The commercial value would be limited by the safety record and by the difficulty of showing a clinically meaningful advantage over established ADHD medicines.

A method-of-use patent also would not prevent unapproved or off-label use outside the claimed indication. Enforcement would be difficult if generic or compounded pemoline became available through other channels.

How strong is the patent estate for pemoline?

The current patent estate is effectively weak for commercial purposes.

Patent category	Current defensive value
Original composition patent	Expired
Historical tablet formulation	Expired or commercially irrelevant
Chewable formulation	Expired or commercially irrelevant
ADHD method of use	Historical rights have no meaningful current exclusivity
New controlled-release formulation	Potentially patentable, but requires new development
New prodrug or delivery system	Potentially patentable, with high development risk
Manufacturing process	Limited value unless difficult to design around
Regulatory exclusivity	No current U.S. exclusivity

The absence of a current patent moat is not the largest investment problem. The larger issue is that new intellectual property would need to support a regulatory and clinical strategy capable of overcoming pemoline’s liver toxicity.

What was the FDA Orange Book status of pemoline?

Pemoline had historical Orange Book listings for approved products and generic equivalents. The relevant listings are no longer a meaningful source of market protection because the U.S. products were withdrawn and the underlying patents are expired.

The Orange Book does not transform an old, withdrawn drug into an active commercial asset. It primarily records approved products, patents, exclusivity, and therapeutic-equivalence information. For pemoline, the practical status is:

• No current branded U.S. franchise
• No active market exclusivity
• No meaningful current patent listing supporting premium pricing
• No conventional generic-launch opportunity tied to an active reference product

A company seeking to reintroduce pemoline would likely need to pursue a new regulatory strategy rather than rely on the historical approval structure.

Which companies challenged or competed with pemoline?

Pemoline competed in the ADHD stimulant market against methylphenidate and amphetamine products. The principal commercial alternatives included:

• Ritalin and other methylphenidate products
• Adderall and other mixed amphetamine salts
• Dextroamphetamine products
• Later nonstimulants such as atomoxetine
• Guanfacine and clonidine products

The competitive disadvantage was structural. Physicians already had established medicines with broader clinical use, clearer commercial infrastructure, and stronger prescribing familiarity. Pemoline would need to demonstrate a specific benefit, such as lower abuse potential or a differentiated duration of action, while addressing its liver-safety liability.

What generic entry risks exist for pemoline?

Generic entry is not the principal current risk because the U.S. branded market has already disappeared. If a sponsor attempted to commercialize pemoline again, competition could arise from:

1. Historical generic manufacturers returning to the market.
2. Compounding pharmacies supplying formulations where legally permitted.
3. Alternative stimulant products with established clinical adoption.
4. Nonstimulant ADHD medicines.
5. New CNS products that avoid controlled-substance restrictions.

A conventional abbreviated new drug application (ANDA) strategy would be commercially unattractive without an active reference product and a viable reimbursement market. A new drug application or 505(b)(2) pathway could offer a more realistic route for a differentiated formulation, but that path would still require substantial safety and pharmacology work.

Are there Paragraph IV challenges involving pemoline?

No current, commercially material Paragraph IV dispute is apparent for pemoline. Paragraph IV litigation is relevant when an ANDA applicant challenges an unexpired Orange Book patent. Pemoline lacks the commercial conditions that typically produce such litigation:

• No important active branded reference product
• No valuable unexpired composition patent
• No meaningful current market revenue
• No high-value formulation franchise
• No apparent litigation-driven launch opportunity

Historical generic competition occurred before the 2005 U.S. withdrawal. Those events do not create a present-day patent challenge opportunity.

Does pemoline have biosimilar risk?

Pemoline has no biosimilar risk because it is a small-molecule chemical drug, not a biologic. The relevant competition is generic, hybrid, reformulated, or therapeutically substitutable competition.

The closest regulatory categories would be:

• ANDA generic competition for an equivalent product
• 505(b)(2) development for a modified formulation or dosing approach
• Full new drug development for a materially differentiated product

A biologics-style interchangeability framework does not apply.

What manufacturing and intellectual-property barriers affect pemoline?

Pemoline’s manufacturing barrier is likely modest at the active pharmaceutical ingredient level. The molecule is old and does not require biologic production, complex cell culture, or specialized device technology.

The more material barriers are clinical and regulatory:

Barrier	Investment impact
Hepatotoxicity	High
Need for liver monitoring	High
Pediatric risk perception	High
Differentiation against methylphenidate and amphetamine	High
Controlled-substance compliance	Moderate
API manufacturing complexity	Low to moderate
Formulation patentability	Moderate
Reimbursement access	Weak
Physician adoption	Weak

A technically simple API does not produce an attractive investment when the product requires intensive monitoring and competes against safer, established alternatives.

What licensing deals involve pemoline?

No major current licensing transaction creates a credible investment thesis around pemoline. The historical commercial rights were associated with Abbott and generic manufacturers, but the original branded franchise has ended.

A licensing deal involving pemoline today would likely concern one of four assets:

• A new formulation
• A prodrug
• A combination product
• A narrowly targeted method of use

The value of such a transaction would depend on new clinical evidence, not on the historical Cylert brand or expired patents. Licensing the old molecule without a differentiated development program would have limited strategic value.

What patent litigation affects pemoline?

There is no prominent current patent litigation affecting pemoline’s U.S. commercial outlook. The litigation profile is effectively inactive because the relevant patent and product markets have expired or withdrawn.

Any future dispute would more likely concern:

• Ownership of a newly developed formulation patent
• Trade secrets relating to manufacturing
• Regulatory exclusivity for a reformulated product
• False-marking or patent-enforcement issues
• Compounded-drug distribution and regulatory compliance

The old pemoline franchise does not present a current Hatch-Waxman litigation platform comparable to active blockbuster products.

What revenue exposure did pemoline create?

Pemoline’s historical revenue exposure was limited relative to leading ADHD medicines. The product’s commercial value declined as liver-safety warnings intensified and physicians shifted toward methylphenidate, amphetamine, and nonstimulant therapies.

Revenue driver	Effect on pemoline
Low-cost generic competition	Reduced pricing power
Safety warnings	Reduced prescribing
Monitoring requirements	Increased treatment friction
Established stimulant alternatives	Reduced differentiation
U.S. withdrawal	Eliminated U.S. branded revenue
Limited international use	Constrained global opportunity

There is no meaningful current public-company revenue stream that can be modeled from pemoline itself. Any investment thesis based on historical Cylert sales would be disconnected from current market conditions.

How does pemoline compare with competing ADHD drugs?

Factor	Pemoline	Methylphenidate	Amphetamine products	Atomoxetine
Current U.S. commercial status	Withdrawn	Active	Active	Active
Abuse potential	Lower than many stimulants, but not absent	Material	Material	Lower
Severe liver injury concern	Major historical issue	Not the defining liability	Not the defining liability	Known but less central
Patent opportunity today	Minimal for old product	Product-specific	Product-specific	Product-specific
Physician familiarity	Low	High	High	High
Monitoring burden	Liver-function monitoring	Controlled-substance monitoring	Controlled-substance monitoring	Clinical monitoring
Reentry attractiveness	Low	Established market	Established market	Established market

Pemoline’s lower perceived abuse potential cannot compensate for the regulatory and safety disadvantages unless a new product shows a strong and reproducible clinical benefit.

What generic launch scenarios are plausible?

Three scenarios are relevant.

Scenario 1: No commercial reentry

This is the base case. Pemoline remains withdrawn in the United States, with no meaningful branded or generic investment. The molecule retains historical or niche scientific interest but no substantial pharmaceutical value.

Scenario 2: Limited compounded or investigational use

Pemoline could appear in tightly controlled research or compounding contexts, subject to applicable law and regulatory oversight. This would not create a scalable branded pharmaceutical market.

Scenario 3: Reformulated redevelopment

A sponsor could pursue a controlled-release formulation, prodrug, or targeted indication. This scenario would require:

• New toxicology and pharmacokinetic work
• Evidence of reduced hepatic risk or improved exposure control
• A regulatory pathway such as 505(b)(2) or a full NDA
• New patent claims
• A commercially credible reimbursement strategy
• Clinical differentiation from established ADHD medicines

This is a high-risk redevelopment project rather than a generic launch opportunity.

What is the investment outlook for pemoline?

Pemoline is a poor standalone pharmaceutical investment. The product has no current U.S. commercial revenue, no meaningful legacy patent protection, no active exclusivity, and a serious safety history documented by the FDA.[1][2]

A potential investment would have to be based on a new asset built around pemoline rather than on pemoline itself. The minimum investable thesis would require a technically credible mechanism for reducing liver toxicity, new intellectual property, and evidence of a target population underserved by existing ADHD treatments.

On the available commercial fundamentals, the risk profile is:

Investment factor	Assessment
Current revenue	None of material U.S. relevance
Patent strength	Weak to nonexistent for historical product
Regulatory risk	Very high
Clinical differentiation	Unproven
Generic threat	Secondary to safety and market absence
Manufacturing risk	Manageable
Licensing value	Low for legacy molecule
Litigation exposure	Low
Reimbursement outlook	Weak
Redevelopment upside	Speculative
Overall investment rating	Avoid as a standalone legacy-drug investment

Key Takeaways

• Pemoline was withdrawn from the U.S. market after the FDA determined that severe liver injury outweighed its ADHD benefits.[2]
• The original composition and formulation patent estate is expired or commercially irrelevant.
• No current Paragraph IV dispute or meaningful Orange Book exclusivity supports a pemoline investment thesis.
• Pemoline has no biosimilar exposure because it is a small-molecule drug.
• Generic manufacturing is not the main barrier; hepatotoxicity, clinical differentiation, and regulatory risk are.
• A new formulation or prodrug could create fresh patent rights, but it would require a new development program.
• Historical Cylert revenue is not a valid basis for current valuation.
• The molecule is unsuitable as a conventional generic, licensing, or royalty investment.

FAQs About Pemoline Patent and Investment Risk

Is pemoline still FDA approved in the United States?

Pemoline is not a currently marketed U.S. ADHD treatment. The FDA requested withdrawal of pemoline products in 2005 because of serious liver-injury risk.[2]

Can a company launch generic pemoline today?

A conventional generic launch would face limited commercial value because the historical U.S. market was withdrawn. A sponsor would also need to address regulatory, supply, and safety requirements.

Does pemoline have an active composition patent?

No meaningful active composition patent should be assumed for the historical pemoline molecule. Its foundational patent protection expired decades after discovery and commercialization.

Could a pemoline prodrug receive new patent protection?

Yes. A novel prodrug, delivery system, or formulation could potentially receive new patent protection if it meets patentability requirements and provides a credible technical advantage. Patentability would not resolve the underlying clinical risk.

Is pemoline a target for pharmaceutical licensing?

The legacy molecule has limited licensing value. A transaction could become relevant only if it included new clinical data, a differentiated formulation, or intellectual property that materially improves safety, dosing, or patient selection.

References

1. U.S. Food and Drug Administration. (2005). Cylert (pemoline) product information and safety communications. FDA.

2. U.S. Food and Drug Administration. (2005, October 4). FDA requests withdrawal of pemoline products from the market. FDA Drug Safety Communication.

3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: The Orange Book. FDA.

4. U.S. Drug Enforcement Administration. (2023). Controlled substances schedules. U.S. Department of Justice.