METRIZAMIDE - Generic Drug Details

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

Metrizamide is the generic ingredient in one branded drug marketed by Ge Healthcare and is included in one NDA. Additional information is available in the individual branded drug profile pages.

Summary for METRIZAMIDE

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	1
Drug Master File Entries:	1
Raw Ingredient (Bulk) Api Vendors:	36
DailyMed Link:	METRIZAMIDE at DailyMed

Medical Subject Heading (MeSH) Categories for METRIZAMIDE

Contrast Media

Anatomical Therapeutic Chemical (ATC) Classes for METRIZAMIDE

V08AB	Watersoluble, nephrotropic, low osmolar X-ray contrast media
V08A	X-RAY CONTRAST MEDIA, IODINATED
V08	CONTRAST MEDIA
V	Various

US Patents and Regulatory Information for METRIZAMIDE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Ge Healthcare	AMIPAQUE	metrizamide	INJECTABLE;INJECTION	017982-001	Approved Prior to Jan 1, 1982		DISCN	No	No
Ge Healthcare	AMIPAQUE	metrizamide	INJECTABLE;INJECTION	017982-004	Sep 12, 1983		DISCN	No	No
Ge Healthcare	AMIPAQUE	metrizamide	INJECTABLE;INJECTION	017982-002	Approved Prior to Jan 1, 1982		DISCN	No	No

Expired US Patents for METRIZAMIDE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Ge Healthcare	AMIPAQUE	metrizamide	INJECTABLE;INJECTION	017982-001	Approved Prior to Jan 1, 1982	3,701,771
Ge Healthcare	AMIPAQUE	metrizamide	INJECTABLE;INJECTION	017982-002	Approved Prior to Jan 1, 1982	3,701,771

Metrizamide Market Dynamics, Patent Status, Regulatory Position, and Financial Trajectory

Last updated: September 9, 2026

Metrizamide is a legacy nonionic iodinated contrast agent whose commercial trajectory ended after newer agents, including iohexol, iopamidol, and iopromide, displaced it in radiology. The product has no meaningful current branded-drug market, no active exclusivity position, and no identifiable public revenue stream. Its remaining economic relevance is limited to historical clinical use, reference standards, analytical research, and possible residual inventory in specialized markets.

What is metrizamide and what was it used for?

Metrizamide is a water-soluble, nonionic iodinated contrast medium formerly used for myelography, computed tomography, and other diagnostic imaging procedures. It was marketed internationally under the brand name Amipaque and was among the first nonionic contrast agents used in clinical practice (National Library of Medicine, 2024).

Attribute	Metrizamide
Active ingredient	Metrizamide
Chemical class	Nonionic iodinated contrast medium
CAS number	31112-62-6
Molecular formula	C18H22I3N3O8
Historical brand	Amipaque
Principal historical use	Intrathecal myelography and diagnostic imaging
Current commercial position	Legacy or discontinued product in major markets
Biosimilar relevance	None
Current U.S. Orange Book position	No active marketed product listing identified
Current exclusivity	None of commercial significance

Metrizamide was less osmotically active than older ionic contrast agents, which reduced some adverse effects. Its clinical limitations included neurotoxicity, seizures, headache, nausea, and other complications associated with intrathecal administration. Newer nonionic agents offered improved safety, handling, imaging performance, and commercial support.

When did metrizamide lose exclusivity and commercial relevance?

Metrizamide lost commercial exclusivity decades ago. Its core composition and early clinical-use patent rights are no longer commercially enforceable in the United States or other mature pharmaceutical markets.

The more important event was not patent expiry but therapeutic substitution. Metrizamide was progressively replaced from the 1980s onward by newer low-osmolar nonionic contrast agents. Iohexol, iopamidol, iopromide, and related products provided manufacturers with more competitive products for broad radiology use and, in several cases, improved clinical utility for intrathecal procedures.

Historical exclusivity timeline

Period	Market event	Commercial effect
1960s-1970s	Development and clinical introduction of metrizamide	Established the nonionic contrast-medium category
1970s-1980s	Expansion in myelography and diagnostic imaging	Product gained clinical adoption
1980s	Introduction of newer low-osmolar nonionic agents	Metrizamide began losing share
1990s	Broad adoption of iohexol, iopamidol, and related agents	Metrizamide became commercially marginal
2000s onward	Withdrawal or discontinuation in major markets	No meaningful branded-drug growth remained
Current period	Limited research and reference-material demand	No material prescription-drug market

The absence of a current Orange Book listing is commercially more important than historical patent dates. FDA Orange Book listings identify approved drug products with active regulatory relevance, including products subject to approved ANDAs and listed patents. Metrizamide does not have an active U.S. market position comparable with current contrast agents (U.S. Food and Drug Administration, 2024).

What is the FDA regulatory status of metrizamide?

Metrizamide has no meaningful current FDA commercial status as an actively marketed contrast product. Historical U.S. regulatory records and older product labeling document its use as a diagnostic contrast medium, but modern clinical practice has moved to other agents.

The product should not be treated as an active FDA-regulated growth product. There is no current commercial pathway analogous to a newly approved NDA, an active supplemental indication, or an ANDA-driven generic market.

What is the Orange Book status of metrizamide?

No active Orange Book product position is identifiable for metrizamide as a currently marketed product. That means:

• No active listed-drug exclusivity is protecting a current U.S. product.
• No current Paragraph IV dispute is driving market entry.
• No active branded product appears to be generating an ANDA-based litigation strategy.
• Any historical NDA or product approval has no apparent current commercial significance.

A discontinued product may remain in historical regulatory databases even after the market has ended. Historical presence should not be confused with active marketing authorization or commercial availability.

What patents protect metrizamide today?

No commercially meaningful patent estate protects metrizamide today. The molecule is an older small-molecule contrast agent, and any composition-of-matter patents associated with its original development would have expired many years ago.

Patent categories historically relevant to metrizamide

The historical patent estate would have centered on:

1. Composition-of-matter claims covering the iodinated compound.
2. Synthetic methods for producing metrizamide.
3. Pharmaceutical compositions containing the active ingredient.
4. Diagnostic-use claims covering radiographic or intrathecal administration.
5. Manufacturing and purification processes.

These rights would have had limited practical duration because metrizamide entered the market several decades ago. Any remaining patent risk would more likely concern a newly developed formulation, process, or use rather than the active ingredient itself.

No current formulation-patent strategy, method-of-use patent program, or patent-term-extension position appears to create an effective barrier to commercial substitution. The molecule's commercial decline occurred before modern lifecycle-management strategies became central to contrast-agent portfolios.

Are there Paragraph IV challenges or generic-launch risks?

There is no active Paragraph IV market event associated with metrizamide. A Paragraph IV certification applies when an ANDA applicant challenges listed patents for an approved reference drug. Without an active listed reference product and relevant Orange Book patents, there is no current litigation pathway of practical importance.

Generic entry scenario

A theoretical generic metrizamide product would face limited patent barriers but also weak commercial incentives. The principal obstacles would be:

• Very limited clinical demand.
• Physician preference for newer contrast media.
• Existing hospital protocols favoring current agents.
• Procurement requirements tied to broad product supply and service support.
• Potential regulatory and manufacturing costs disproportionate to market size.
• Clinical reluctance to reintroduce an older intrathecal agent.

The market therefore has a low patent-entry barrier but a high commercial-entry barrier. This distinction is important. An unprotected molecule does not automatically support a viable generic business.

What formulations were protected by metrizamide patents?

Historical formulations likely covered sterile aqueous solutions containing metrizamide at concentrations suitable for diagnostic administration. The commercial product was supplied for radiographic use, including intrathecal administration.

The original formulation value has largely disappeared because current contrast agents compete on clinical performance, osmolality, viscosity, neurotoxicity profile, packaging, storage, and institutional familiarity. A modern formulation based on metrizamide would need to establish a clear benefit over established alternatives. That benefit is not evident from the current market position.

Manufacturing and intellectual-property barriers

Metrizamide contains three iodine atoms per molecule and requires controlled synthesis, purification, sterilization, and quality testing. These requirements create technical barriers, but they are not strong proprietary barriers.

The relevant manufacturing risks are operational rather than patent-based:

• Small-volume production may be uneconomic.
• Specialized analytical controls may increase unit cost.
• Legacy manufacturing processes may no longer be supported.
• Raw-material and sterile-fill capacity may be difficult to secure.
• Regulatory reactivation could require updated chemistry, manufacturing, and controls documentation.

These factors reduce the probability of a commercial relaunch even though the underlying molecule is old and unpatented.

How does metrizamide compare with current contrast agents?

Metrizamide has been commercially displaced by newer nonionic iodinated agents with broader indications and stronger supplier support.

Product	Active ingredient	Historical or current role	Relative market position
Amipaque	Metrizamide	Legacy myelography and imaging	Discontinued or marginal
Omnipaque	Iohexol	Broad radiology and intrathecal use	Established current product
Isovue	Iopamidol	Broad diagnostic imaging	Established current product
Ultravist	Iopromide	Broad diagnostic imaging	Established current product
Visipaque	Iodixanol	Iso-osmolar imaging applications	Established specialty product

Current products benefit from established hospital contracts, validated protocols, global distribution, and modern regulatory documentation. Metrizamide has none of these advantages at a scale that supports meaningful competition.

Which companies challenged or displaced metrizamide?

The competitive threat came from manufacturers that developed and commercialized newer nonionic contrast agents, rather than from a focused patent challenge to metrizamide.

Important companies in the broader iodinated contrast market have included:

• GE Healthcare
• Bracco
• Bayer
• Guerbet
• Mallinckrodt, historically
• Nycomed and predecessor organizations associated with older contrast products

The market shifted from a single-product innovation cycle to portfolio competition. Suppliers competed on safety, imaging quality, indication breadth, supply reliability, and hospital economics. Metrizamide did not retain a differentiated position as these products expanded.

What licensing deals affected metrizamide?

No major current licensing deal appears to generate material value from metrizamide. Historical development and commercialization involved the originating manufacturer and successor corporate entities, but the product is no longer a meaningful licensing asset.

Any residual transaction value would likely involve:

• Legacy regulatory files.
• Historical manufacturing know-how.
• Chemical reference materials.
• Research-use supply.
• Rights bundled with broader contrast-agent portfolios.

There is no clear basis for valuing metrizamide as an independent licensing opportunity in the current pharmaceutical market.

What is the financial trajectory for metrizamide?

Metrizamide followed a classic pharmaceutical lifecycle:

1. Initial growth after introduction of a clinically differentiated nonionic contrast medium.
2. Expansion through myelography and diagnostic imaging.
3. Revenue erosion after the arrival of newer nonionic products.
4. Accelerated decline as hospitals standardized on replacement agents.
5. Commercial discontinuation or residual niche use.

No reliable public company reporting isolates metrizamide revenue by product, geography, or year. Its financial trajectory is therefore best assessed through market position and product substitution rather than reported sales figures.

Revenue exposure

Current revenue exposure is effectively immaterial for major contrast-agent manufacturers. The principal economic effects are negative:

• No significant recurring branded sales.
• No meaningful patent premium.
• No active indication-expansion opportunity.
• No credible biosimilar or follow-on biologic market.
• Minimal potential for price increases based on differentiation.

Research-grade sales may persist, but those transactions do not recreate a pharmaceutical market. They are usually lower-volume and supplied through specialty chemical or laboratory channels.

What generic launch risks exist for metrizamide?

A generic launch would face low legal risk but high market risk. The product could theoretically be manufactured without confronting a live composition-of-matter patent. The commercial challenge would be convincing hospitals and radiologists to use an older agent when established alternatives already have stronger clinical and procurement positions.

A relaunch would also require a regulatory and pharmacovigilance strategy. Historical safety data would not eliminate the need to establish product quality, sterile manufacturing controls, labeling, and current supply reliability.

The most likely commercial outcome of any new metrizamide entrant would be a small specialty or shortage-driven market, not a mass-market generic franchise.

How strong is the patent estate for metrizamide?

The current patent estate is weak to nonexistent for commercial purposes.

Patent-estate factor	Assessment
Core composition patent	Expired
Current Orange Book patents	None of practical relevance
Method-of-use protection	Expired or commercially obsolete
Formulation protection	No current blocking position identified
Manufacturing patents	Historical and unlikely to block entry
Patent-term extension	No current commercial effect
Paragraph IV exposure	No active dispute identified
Freedom to operate	Broad for the old molecule, subject to ordinary regulatory review

The key investment conclusion is that metrizamide is not a protected pharmaceutical asset. Its value is constrained by demand erosion, product obsolescence, and the cost of restoring a legacy product to modern commercial standards.

Key Takeaways

• Metrizamide is a legacy nonionic iodinated contrast agent marketed historically as Amipaque.
• Newer agents, including iohexol and iopamidol, displaced it from mainstream clinical use.
• Core patent protection expired decades ago.
• No active Orange Book exclusivity or Paragraph IV litigation has meaningful commercial relevance.
• No biosimilar risk exists because metrizamide is a small molecule, not a biologic.
• Current revenue is not publicly reported and appears commercially immaterial.
• The main barriers to reentry are demand, clinical substitution, manufacturing economics, and regulatory reactivation, not patents.
• Metrizamide has negligible value as a standalone licensing or investment asset.

FAQs

Is metrizamide still available in the United States?

Metrizamide is not an actively marketed mainstream U.S. contrast agent. Current imaging practice relies on newer iodinated products with broader commercial support.

What brand name was used for metrizamide?

The principal historical brand name was Amipaque. The product was associated with older myelography and diagnostic imaging markets.

Is metrizamide covered by an active patent?

No commercially meaningful active patent protection remains for the original molecule. Any historical composition, use, and formulation patents would have expired.

Can metrizamide be relaunched as a generic drug?

A relaunch is theoretically possible from a patent perspective but commercially unattractive. The product would need to overcome limited demand, established clinical substitutes, sterile-manufacturing costs, and modern regulatory requirements.

Is metrizamide a biologic or biosimilar product?

No. Metrizamide is a chemically defined small molecule. Biosimilar regulations do not apply.

References

1. National Library of Medicine. (2024). Metrizamide. PubChem Compound Summary. https://pubchem.ncbi.nlm.nih.gov/compound/Metrizamide

2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/

3. U.S. Food and Drug Administration. (2024). Discontinued drug product list. https://www.fda.gov/drugs/drug-approvals-and-databases/discontinued-drug-product-list

4. World Health Organization Collaborating Centre for Drug Statistics Methodology. (2024). ATC/DDD index. https://www.whocc.no/atc_ddd_index/