PHENMETRAZINE HYDROCHLORIDE - Generic Drug Details

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

Phenmetrazine hydrochloride is the generic ingredient in one branded drug marketed by Boehringer Ingelheim and is included in two NDAs. Additional information is available in the individual branded drug profile pages.

Summary for PHENMETRAZINE HYDROCHLORIDE

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	2
Raw Ingredient (Bulk) Api Vendors:	21
DailyMed Link:	PHENMETRAZINE HYDROCHLORIDE at DailyMed

Medical Subject Heading (MeSH) Categories for PHENMETRAZINE HYDROCHLORIDE

Appetite Depressants

Central Nervous System Stimulants

Sympathomimetics

US Patents and Regulatory Information for PHENMETRAZINE HYDROCHLORIDE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Boehringer Ingelheim	PRELUDIN	phenmetrazine hydrochloride	TABLET, EXTENDED RELEASE;ORAL	011752-003	Approved Prior to Jan 1, 1982		DISCN	No	No
Boehringer Ingelheim	PRELUDIN	phenmetrazine hydrochloride	TABLET;ORAL	010460-005	Approved Prior to Jan 1, 1982		DISCN	No	No
Boehringer Ingelheim	PRELUDIN	phenmetrazine hydrochloride	TABLET, EXTENDED RELEASE;ORAL	011752-004	Approved Prior to Jan 1, 1982		DISCN	No	No

Phenmetrazine Hydrochloride Market Dynamics, Patent Status, and Financial Trajectory

Last updated: September 5, 2026

Phenmetrazine hydrochloride is a discontinued central nervous system stimulant and anorectic formerly marketed in the United States as Preludin. Its commercial market has effectively ended. The product has no meaningful current FDA-approved pharmaceutical sales, no active biosimilar pathway, no identifiable modern Orange Book strategy, and limited commercial value outside historical, research, or illicit channels. Public revenue data are not available for the original product, so a precise historical sales curve cannot be established.

What is phenmetrazine hydrochloride and how was it marketed?

Phenmetrazine hydrochloride is the hydrochloride salt of phenmetrazine, a sympathomimetic stimulant that was used as an appetite suppressant. Its pharmacology is associated with central nervous system stimulation and monoamine release, creating therapeutic effects alongside abuse and dependence risks.

The principal historical product was Preludin. It was marketed for weight reduction before the broader withdrawal of many amphetamine-like anorectics from the U.S. market. Phenmetrazine was later controlled as a Schedule II substance under the U.S. Controlled Substances Act because of its abuse potential (U.S. Drug Enforcement Administration [DEA], n.d.).

Attribute	Phenmetrazine hydrochloride
Drug class	Sympathomimetic stimulant and anorectic
Historical brand	Preludin
Former sponsor	Ciba-Geigy and predecessor commercial entities are associated with historical U.S. marketing
U.S. status	Discontinued commercial product
Controlled-substance status	Schedule II
Current FDA commercial position	No meaningful active branded market
Current Orange Book relevance	No current commercially significant reference product listing identified
Biosimilar relevance	None
Primary current use	Research, forensic, historical, and illicit contexts

Phenmetrazine is listed in chemical and pharmacological databases as a controlled stimulant rather than as an actively commercialized therapeutic product (National Center for Biotechnology Information [NCBI], n.d.).

When did phenmetrazine lose commercial exclusivity?

Phenmetrazine lost practical commercial exclusivity decades ago. The relevant issue is no longer patent expiry alone. The product’s commercial decline resulted from the interaction of patent aging, regulatory control, safety concerns, abuse liability, and the removal or discontinuation of historical products.

The original patents covering phenmetrazine, its synthesis, and early formulations would have expired many decades ago under modern patent-term rules. Any U.S. patent protection associated with the original product is therefore presumed expired based on the product’s mid-20th-century commercialization. A current blocking patent estate is not commercially apparent.

No modern product-specific exclusivity period is relevant. The following forms of U.S. exclusivity do not create a current barrier:

Exclusivity category	Current relevance
New chemical entity exclusivity	Expired or historically unavailable
Orphan-drug exclusivity	Not applicable
Pediatric exclusivity	Not applicable
Qualified infectious-disease exclusivity	Not applicable
Biologic exclusivity	Not applicable
Data exclusivity for a modern approval	Not commercially relevant
Patent term extension	No current commercial significance
Orange Book listed patent exclusivity	No meaningful current protection identified

The principal commercial constraint is regulatory status, not patent duration.

What is the FDA regulatory status of phenmetrazine hydrochloride?

Phenmetrazine is not an actively marketed FDA-approved pharmaceutical product in the U.S. The historical product was withdrawn from commercial use, and the active ingredient does not have a current branded growth platform comparable with modern obesity or central nervous system medicines.

The U.S. regulatory position has three practical consequences:

1. A company cannot treat the historical Preludin approval as a straightforward commercial asset.
2. Any modern development program would require a new regulatory strategy, including contemporary nonclinical, clinical, manufacturing, abuse-liability, and risk-management data.
3. The Schedule II classification would materially increase development, distribution, monitoring, and compliance costs.

The FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, commonly called the Orange Book, is the primary U.S. reference for approved products and listed patents. A historical product that is no longer marketed does not provide the same regulatory or commercial value as an active reference listed drug (U.S. Food and Drug Administration [FDA], n.d.-a).

What is the Orange Book status of phenmetrazine?

Phenmetrazine has no meaningful current Orange Book position for commercial planning. Even if historical records or legacy entries are located, they would not establish an active growth market or a modern patent barrier.

For generic-drug strategy, the key distinction is between:

• an active reference listed drug that supports an abbreviated new drug application;
• a discontinued drug that may require FDA suitability or approval analysis;
• an unapproved or nonmarketed controlled substance that requires a substantially different development pathway.

A company evaluating phenmetrazine would therefore face more than ordinary Paragraph IV analysis. The central question would be whether a legally marketable reference product and viable FDA approval route exist.

How many patents cover phenmetrazine hydrochloride today?

No commercially material active patent estate is apparent for the historical active ingredient itself. Original composition-of-matter, manufacturing, and formulation patents would be expected to have expired.

Patent category	Expected current position
Original composition of matter	Expired
Salt-form protection	Expired
Early synthesis patents	Expired
Historical immediate-release formulations	Expired
Modern extended-release formulations	No established commercial estate identified
Abuse-deterrent formulations	No established commercial estate identified
Combination products	No established commercial estate identified
Method-of-use patents	No active commercial position identified

A new patent estate could theoretically be built around a novel formulation, delivery system, abuse-deterrent design, or new therapeutic use. Such claims would need to satisfy novelty, nonobviousness, written-description, enablement, and utility requirements. A patent on a reformulation would not restore exclusivity to the old product as a whole.

Are there Paragraph IV challenges involving phenmetrazine?

No commercially significant current Paragraph IV litigation involving phenmetrazine hydrochloride is apparent. The likely reason is economic: there is no established high-value branded product with substantial protected revenue for a generic challenger to attack.

Paragraph IV litigation generally becomes attractive when a branded product has:

• material remaining sales;
• an active Orange Book patent estate;
• an approved reference listed drug;
• a viable generic substitution market;
• a clear launch-at-risk opportunity.

Phenmetrazine does not present that profile. A generic company would face regulatory and controlled-substance barriers without the revenue opportunity that normally justifies patent litigation.

What formulation patents could protect a revived phenmetrazine product?

A revived product would need differentiated intellectual property because the active ingredient itself is old. Potential claim categories could include:

Extended-release formulations

Modified-release delivery could reduce dosing frequency and produce a patentable product profile if the formulation provides a non-obvious pharmacokinetic or clinical advantage. The commercial challenge would be demonstrating an acceptable benefit-risk profile for a controlled stimulant.

Abuse-deterrent formulations

An abuse-deterrent tablet, capsule, or multiparticulate system could support formulation claims. FDA approval would still require evidence that the product’s abuse-deterrent properties translate into meaningful public-health benefits. Abuse deterrence would not eliminate Schedule II obligations.

Combination products

A combination with another appetite-regulating or metabolic agent could generate new composition and method-of-use claims. The combination would face clinical-development and safety requirements for each component and for the combination as a whole.

Alternative delivery systems

Transdermal, implantable, nasal, or other delivery systems could create new patent opportunities. These routes would also raise manufacturing, human-factors, abuse-liability, and pharmacokinetic issues.

What patent litigation and settlement agreements affect phenmetrazine?

No current material patent litigation or branded-generic settlement agreement is associated with phenmetrazine hydrochloride. The absence of litigation is commercially informative. It indicates that the product does not currently support the standard branded drug lifecycle of patent challenges, Paragraph IV settlements, authorized generics, or launch-date negotiations.

There is also no evident modern licensing market centered on phenmetrazine. Historical ownership, distribution, or manufacturing arrangements may have existed, but they do not create a current commercial network comparable with active pharmaceutical assets.

What is the financial trajectory of phenmetrazine?

Phenmetrazine’s financial trajectory is best described as a completed commercial decline rather than a continuing pharmaceutical market.

Period	Commercial condition	Financial implication
Initial commercialization	Prescription anorectic and stimulant market	Historical product revenue generated
Expansion of amphetamine-like anorectics	Broader demand for weight-loss stimulants	Product competed within a crowded stimulant class
Rising abuse and safety concerns	Increased regulatory scrutiny	Reduced commercial durability
Product discontinuation	Loss of branded sales	Revenue stream ended
Post-discontinuation period	Controlled-substance and illicit use	No transparent pharmaceutical revenue base
Current period	Research and historical relevance	No established investable commercial market

No reliable public dataset provides annual Preludin sales, operating profit, contribution margin, or manufacturer-specific revenue. The product predates modern pharmaceutical disclosure practices, and its historical commercial information is not reported with the granularity now used for listed pharmaceutical companies.

A current valuation based on historical brand recognition would be unsupported. The relevant value drivers would instead be:

• the feasibility of a new FDA development program;
• the ability to obtain a new indication;
• formulation differentiation;
• controlled-substance manufacturing capacity;
• abuse-liability mitigation;
• reimbursement acceptance;
• competitive positioning against modern obesity medicines.

What generic entry risks exist?

Generic entry risk is low because there is little or no active branded revenue to displace. Development risk is high because a company attempting to commercialize phenmetrazine would need to overcome regulatory and commercial barriers that do not arise with a routine generic.

The principal risks are:

1. No meaningful current branded benchmark.
2. Uncertain FDA pathway for a discontinued controlled anorectic.
3. High abuse-liability scrutiny.
4. Competition from GLP-1 receptor agonists and other modern obesity therapies.
5. Limited physician demand for an older stimulant mechanism.
6. Restricted distribution and controlled-substance compliance.
7. Potential payer resistance.
8. Reputational and liability exposure associated with stimulant use.

A generic manufacturer would have little incentive to enter absent a clear FDA pathway and evidence of durable demand.

How does phenmetrazine compare with modern obesity drugs?

Phenmetrazine is commercially disadvantaged against current obesity medicines. Modern products increasingly rely on metabolic mechanisms, chronic-disease positioning, structured titration, outcomes data, and large commercial infrastructure.

Factor	Phenmetrazine hydrochloride	Modern GLP-1-based obesity medicines
Mechanism	CNS stimulant and anorectic	Incretin-based metabolic regulation
Regulatory status	Historical and discontinued	Active FDA-approved products
Abuse potential	High regulatory concern	Generally not classified as Schedule II stimulants
Patent position	Historical patents expired	Active composition, formulation, and method patents
Clinical positioning	Short-term appetite suppression	Chronic weight management
Commercial demand	Minimal current pharmaceutical demand	Large and expanding market
Reimbursement strategy	Weak	Supported by clinical-outcomes and obesity-market development
Manufacturing barriers	Controlled-substance controls	Biologic or peptide manufacturing complexity

Phenmetrazine would not compete primarily on price. It would need a clinically differentiated use, such as a narrowly defined population or delivery profile, to justify development.

What manufacturing and intellectual-property barriers exist?

Manufacturing phenmetrazine hydrochloride is technically less difficult than manufacturing a complex biologic or peptide, but controlled-substance requirements create operational barriers. A manufacturer would need compliant sourcing, secure handling, inventory controls, diversion prevention, validated analytical methods, and regulated distribution.

The most defensible new intellectual property would likely relate to:

• controlled-release pharmacokinetics;
• reduced peak plasma concentrations;
• abuse-deterrent design;
• a novel therapeutic indication;
• a specific patient population;
• combination therapy;
• manufacturing purity or impurity-control methods.

A process patent alone would probably provide limited market power if competitors could use an alternative synthesis route.

What is the geographic market coverage?

Phenmetrazine’s current geographic commercial coverage is negligible. Historical regulatory treatment varied by country, but the active ingredient is not a mainstream prescription product in major pharmaceutical markets.

Region	Current commercial assessment
United States	Discontinued pharmaceutical market; Schedule II control
European Union	No meaningful active mainstream market identified
United Kingdom	Historical controlled-drug relevance, no established current market
Canada	No significant current pharmaceutical market identified
Emerging markets	No reliable evidence of a substantial regulated market

Country-level legal status can differ, especially for controlled substances. Those differences do not establish a viable multinational pharmaceutical opportunity.

Key Takeaways

• Phenmetrazine hydrochloride is a discontinued stimulant anorectic, historically marketed as Preludin.
• Its original patent and exclusivity position has expired.
• No meaningful current Orange Book, Paragraph IV, biosimilar, or branded-generic litigation strategy is apparent.
• Current pharmaceutical revenue is effectively absent, and historical revenue data are not publicly reported with precision.
• The main barriers are FDA redevelopment requirements, Schedule II controls, abuse liability, and competition from modern obesity medicines.
• Any commercial revival would depend on a new formulation, indication, or delivery platform rather than the legacy active ingredient alone.
• The asset has limited standalone investment value but could have speculative value within a broader controlled-substance or CNS reformulation platform.

FAQs

Is phenmetrazine hydrochloride still sold by a pharmaceutical company?

No meaningful current pharmaceutical market is established for phenmetrazine hydrochloride in the United States. The historical Preludin product is discontinued.

Is phenmetrazine hydrochloride a controlled substance?

Yes. In the United States, phenmetrazine is classified as a Schedule II controlled substance because of its stimulant and abuse potential (DEA, n.d.).

Can a company file an ANDA for phenmetrazine hydrochloride?

An ANDA would depend on the existence of an appropriate FDA reference listed drug and a legally viable abbreviated pathway. A discontinued historical product does not automatically provide a practical ANDA route.

Does phenmetrazine hydrochloride have active formulation patents?

No commercially material active formulation estate is apparent for the historical product. New patents could potentially cover a novel delivery system, abuse-deterrent design, or modified-release formulation.

Is phenmetrazine hydrochloride a competitor to semaglutide or tirzepatide?

Not on current commercial terms. Phenmetrazine is an older CNS stimulant, while semaglutide and tirzepatide are modern metabolic therapies with active approvals, large clinical programs, current patent estates, and established commercial markets.

References

1. National Center for Biotechnology Information. (n.d.). PubChem compound summary for phenmetrazine. U.S. National Library of Medicine. https://pubchem.ncbi.nlm.nih.gov/

2. U.S. Drug Enforcement Administration. (n.d.). Drug scheduling. https://www.dea.gov/drug-information/drug-scheduling

3. U.S. Food and Drug Administration. (n.d.-a). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files

4. U.S. Food and Drug Administration. (n.d.-b). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/