US Patent 5,980,882: Claim Scope, Expiration, Litigation Risk, and Drug-Resin Patent Landscape

US Patent 5,980,882 covers stabilized pharmaceutical compositions containing a drug-ion-exchange-resin complex and EDTA or an EDTA salt. The patent focuses on reducing degradation of the resin-bound drug by more than 20% over 12 months at room temperature. Its practical scope is concentrated in oral drug-resin products containing dextromethorphan or codeine, although the independent claims also name morphine, hydrocodone, pseudoephedrine, and phenylpropanolamine.

The patent appears to be expired under the standard 20-year US patent-term framework. A current freedom-to-operate analysis should still review terminal disclaimers, patent-term adjustment, reissue activity, and related continuation patents before relying on expiration as a complete clearance position.[1][2]

What does US Patent 5,980,882 protect?

The patent protects four related claim categories:

Claim category	Claims	Core subject matter
Pharmaceutical compositions	1-16, 28-29	Drug-resin complex plus EDTA or EDTA salt
Manufacturing methods	17-19	Forming, drying, suspending, and adding the chelating agent
Product-by-process compositions	20-22	Compositions made through specified manufacturing sequences
Stability and administration methods	23-27, 30-37	Improving stability and administering the stored composition

The central limitation is functional and quantitative. The chelating agent must be present in an amount effective to reduce drug degradation by more than 20% over 12 months at room temperature compared with an otherwise identical composition without the chelating agent.

That limitation narrows the patent materially. Merely including EDTA in a drug-resin product does not necessarily satisfy the claim. The accused product would need to meet the drug, resin, dosage-form, chelator, and comparative stability limitations.

What is the inventive concept?

The claim set combines four technical elements:

A drug bound to an ion-exchange resin.
EDTA or an EDTA salt.
A solid or gel composition, or a liquid composition produced through the claimed process.
Demonstrated stability improvement exceeding 20% over 12 months at room temperature.

The patent therefore targets degradation associated with drug-resin complexes rather than generic pharmaceutical stabilization. The claims do not broadly cover all EDTA-containing pharmaceutical products.

Which drugs fall within the patent claims?

The independent claims identify six drug categories:

Dextromethorphan
Codeine
Morphine
Hydrocodone
Pseudoephedrine
Phenylpropanolamine

The dependent claims narrow the field further to dextromethorphan and codeine. Claims 28-37 create drug-specific fallback positions for those two compounds.

Drug	Expressly identified in independent claims	Drug-specific dependent claims
Dextromethorphan	Yes	28, 30, 32, 34, 36
Codeine	Yes	29, 31, 33, 35, 37
Morphine	Yes	No separate dependent claim
Hydrocodone	Yes	No separate dependent claim
Pseudoephedrine	Yes	No separate dependent claim
Phenylpropanolamine	Yes	No separate dependent claim

The use of a closed drug list is important. A product containing another active ingredient would generally fall outside the literal drug limitation unless a court applied an expansive construction under the doctrine of equivalents. That analysis would depend on prosecution history, claim amendments, specification support, and the specific substitute drug.

What resin systems are protected?

Claim 1 requires a "drug-resin complex," while claim 3 narrows the resin to a cationic exchange resin. Claim 4 further specifies a divinylbenzene sulfonic acid cationic exchange resin.

The claim hierarchy is:

Claim	Resin limitation
1	Drug-resin complex, without a specific resin type
3	Cationic exchange resin
4	Divinylbenzene sulfonic acid cationic exchange resin

The broadest composition claim does not expressly require a cationic resin. Claims 3 and 4 provide narrower positions that may be easier to prove technically but cover fewer products.

An accused product using an anionic exchange resin, neutral adsorbent, polymer matrix, lipid carrier, or nonionic complexing material may challenge the requirement that it contains a drug-resin complex. The analysis turns on whether the resin binds the drug through ion exchange or performs a materially equivalent function in the claimed pharmaceutical structure.

What is the significance of the diffusion-barrier claims?

Claims 9 and 10 cover a drug-resin complex having a diffusion-barrier coating, including an enteric coating.

These claims can reach products where release control is achieved through a coating applied to the drug-resin particles. They do not require the coating to be the only release-control mechanism. Claim 10 narrows the coating to an enteric coating, which may be relevant to products designed to resist release in the stomach.

The claims distinguish between:

Drug-resin binding, which controls or modifies release through ionic interaction.
A diffusion barrier, which adds a physical release barrier.
An enteric coating, which introduces pH-dependent protection or release behavior.

A product with uncoated resin particles may fall within claim 1 if all other limitations are met but would not satisfy claims 9 or 10.

What chelating-agent limitations apply?

Claims 1 and 17-27 limit the chelating agent to EDTA or an EDTA salt. Claims 5 and 6 address whether the chelating agent is covalently bound to the drug-resin complex.

Claim limitation	Scope
EDTA or EDTA salt	Required by the independent claims
0.001% to 10% by weight	Claim 7
0.1% to 5% by weight	Claim 8
Not covalently bound	Claim 5
Covalently bound	Claim 6

Claims 5 and 6 appear to cover opposite structural alternatives. A formulation may therefore fall within one or the other depending on how the EDTA is incorporated. The distinction may create proof issues involving formulation composition, manufacturing conditions, analytical characterization, and whether the EDTA is chemically attached to the resin or simply blended into the product.

The concentration limitations apply only to dependent claims 7 and 8. A product outside those percentages could still be evaluated against claim 1 if the product meets the functional stability limitation.

How strong is the 20% stability limitation?

The 20% degradation-reduction requirement is the main technical and evidentiary boundary.

A comparison would generally require:

The same drug-resin complex.
The same dosage form and excipients, except for EDTA.
Comparable packaging and storage conditions.
Room-temperature storage.
A 12-month period.
A validated assay for drug degradation.
A result showing more than 20% reduction relative to the EDTA-free control.

The claim does not state whether "more than 20 percent" refers to absolute percentage points or a relative reduction. For example, if degradation is 10% without EDTA and 7% with EDTA, the relative reduction is 30%, while the absolute reduction is 3 percentage points. Claim construction and the specification would determine the applicable interpretation.

This limitation can help an innovator against products with incidental EDTA but creates an invalidity and noninfringement vulnerability if the claimed result is not reproducible across batches or if the patent specification does not adequately support the full breadth of the drug, resin, dosage-form, and concentration combinations.

What evidence would be relevant in an infringement dispute?

Relevant evidence would include:

Finished-product specifications.
Certificate-of-analysis data.
Stability protocols and reports.
EDTA identity and concentration.
Drug-resin binding data.
Resin chemistry and particle size.
Coating composition and thickness.
Manufacturing batch records.
Accelerated and long-term stability data.
Comparative control batches without EDTA.
Regulatory submissions describing formulation composition.

A generic applicant may argue that the reference listed drug and the proposed generic do not use the same resin, do not include EDTA, or cannot satisfy the comparative degradation limitation.

What formulations are protected?

The patent covers a broad set of dosage forms, but the independent composition claim requires a solid or gel. Claim 14 expands the administration routes, while claim 15 identifies specific dosage forms.

Dosage form or route	Claim coverage
Solid	Claims 1-2
Gel	Claim 1
Tablet	Claim 15
Capsule	Claim 15
Powder	Claim 15
Lotion	Claim 15
Cream	Claim 15
Suppository	Claim 15
Oral administration	Claims 14 and 16
Topical administration	Claim 14
Rectal administration	Claim 14
Vaginal administration	Claim 14
Nasal administration	Claim 14
Ophthalmic administration	Claim 14
Suspension	Claim 26, for the stability method

The independent composition claims do not expressly require an oral product. Claims 14 and 16 provide route-specific limitations. In commercial terms, oral drug-resin suspensions and solid oral dosage forms are the most likely relevant products because dextromethorphan and codeine are commonly delivered through oral formulations.

Are liquid suspensions covered?

Claims 18 and 21 cover a process in which a dried solid is subsequently suspended in an appropriate liquid. Claims 19 and 22 cover a different sequence in which the drug-resin complex is dried, suspended, and then exposed to the chelating agent.

Claim 23 separately covers improving stability in a composition containing a drug-resin complex by adding EDTA or an EDTA salt. Claims 24-26 narrow that method to a solid, gel, or suspension.

The drafting creates potential overlap between:

A composition claim directed to a solid or gel.
A process claim directed to preparation of a liquid product.
A stability method directed to adding EDTA.
A product-by-process claim directed to a composition made using the specified sequence.

How do the manufacturing claims differ?

Claims 17-19 establish three manufacturing routes.

Route one: EDTA before drying

Claim 17 requires:

Combining the drug and ion-exchange resin in a liquid.
Forming the drug-resin complex.
Adding EDTA or an EDTA salt.
Drying the mixture into a solid or gel.

Route two: EDTA before suspension

Claim 18 requires:

Forming the drug-resin complex.
Adding EDTA.
Drying the mixture into a solid.
Suspending the dried material in a liquid.

Route three: EDTA after suspension

Claim 19 requires:

Forming the drug-resin complex in a first liquid.
Drying the complex.
Suspending it in a second liquid.
Adding EDTA.

The order of addition is therefore material. A process may avoid claims 18 or 19 depending on when EDTA is added, although claim 17 may remain relevant if EDTA was added before drying.

Product-by-process claims 20-22 may be more difficult to apply where the finished product is chemically indistinguishable from a product made by another process. Under US patent law, product-by-process limitations generally remain limitations on the claimed product, although the legal treatment can differ between infringement and patentability analyses.[3]

When did US Patent 5,980,882 lose exclusivity?

US Patent 5,980,882 was issued on November 9, 1999. For a utility patent subject to the post-1995 US term regime, the baseline term is generally 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and other statutory modifications.[1][2]

On the information supplied, the patent should be treated as expired by 2026. A precise expiration date cannot be established solely from the claims. The operative record should be confirmed through the USPTO Patent Center file, including:

Earliest effective nonprovisional filing date.
Patent-term adjustment.
Terminal disclaimer.
Certificate of correction.
Reexamination certificate.
Reissue activity.
Maintenance-fee status.

Because the patent is more than 20 years past issuance, ordinary patent-term extension under 35 U.S.C. § 156 would not ordinarily preserve meaningful market exclusivity at this stage. A patent-expiration determination should still distinguish this patent from later continuation, divisional, or improvement patents.

What is the Orange Book status?

US Patent 5,980,882 is not, by itself, evidence of an Orange Book-listed patent. FDA listing depends on the approved drug application, the NDA holder, the patent type, and the statutory listing requirements under 21 U.S.C. § 355(b)(1) and FDA regulations.[4][5]

The claims are formulation, manufacturing, stability, and use claims. They are not composition-of-matter claims covering dextromethorphan, codeine, or the other listed drugs as chemical entities. If listed for an approved product, the most plausible regulatory category would be a formulation, method-of-use, or drug-delivery patent, subject to FDA’s listing rules.

The supplied information does not identify:

An NDA associated with the patent.
A commercial product associated with the patent.
An Orange Book listing.
A listed patent-use code.
A delisting event.
A paragraph IV certification.

Accordingly, the patent number alone should not be treated as an Orange Book barrier to an ANDA.

Are Paragraph IV challenges or generic entry disputes associated with this patent?

A Paragraph IV certification applies to a patent listed in the Orange Book for a reference listed drug. It is not triggered merely because a patent exists or because a patent covers a formulation technology.[6]

For a generic dextromethorphan or codeine product, the commercial relevance of this patent would depend on whether:

The patent was listed for the reference product.
The generic uses a drug-resin complex.
The generic includes EDTA or an EDTA salt.
The generic’s product meets the 20% stability limitation.
The patent remained unexpired when the ANDA was filed.
Related patents were listed for the same product.

Because the patent appears expired under the ordinary term calculation, a current Paragraph IV challenge to this patent would generally have little practical value. Later formulation patents, abuse-deterrence patents, release-control patents, and product-specific patents could present the operative entry risk.

Which companies are likely to be relevant?

The patent landscape should be divided into four groups:

Participant group	Relevance
Originator or patent owner	May have developed the stabilized drug-resin platform
Branded cough and analgesic companies	May commercialize dextromethorphan or codeine resin products
Generic manufacturers	May develop resin-bound oral products or noninfringing alternatives
Resin and excipient suppliers	May control technical know-how and supply-chain access

The patent itself does not establish current ownership, licensing, or commercialization. Ownership should be traced through USPTO assignment records rather than inferred from the product name or the identity of a resin supplier.

Are there licensing deals?

No licensing agreement can be established from the claim text. A complete licensing review would require assignment records, SEC filings, transaction announcements, product-development agreements, and related patent-family documents.

A commercial license could be important even after patent expiration if it covers:

Manufacturing know-how.
Resin specifications.
Coating technology.
Stability data.
Regulatory filings.
Trademark rights.
Confidential formulation information.

Patent expiration does not terminate contractual or trade-secret restrictions.

What manufacturing and IP barriers remain after patent expiration?

The patent’s expiration would remove the exclusionary effect of its claims, but technical barriers may remain.

Key barriers include:

Controlled drug handling for codeine, morphine, and hydrocodone.
Resin qualification and reproducible drug loading.
Particle-size control.
Drug-release testing.
EDTA compatibility with the resin and active ingredient.
Long-term stability data.
Taste masking and abuse-deterrence performance.
Enteric or diffusion-barrier coating processes.
Scale-up of drying and suspension manufacture.
FDA requirements for bioequivalence and product quality.

For dextromethorphan, regulatory barriers are generally lower than for opioid-containing products. Codeine, morphine, and hydrocodone products face additional controlled-substance, diversion-control, labeling, and manufacturing requirements under FDA and Drug Enforcement Administration frameworks.

How does this patent compare with later formulation patents?

US 5,980,882 is an early platform patent. Its claims are broad in dosage-form language but narrow in the required combination of:

A specified drug list.
A drug-resin complex.
EDTA or an EDTA salt.
A demonstrated stability improvement exceeding 20%.
In some claims, a defined manufacturing sequence.

Later patents may be stronger commercially if they claim:

A specific marketed formulation.
A specific resin grade.
A defined drug-to-resin ratio.
A release profile.
A taste-masking architecture.
A coating composition.
A dosing regimen.
A product-specific suspension.
A manufacturing parameter that is difficult to design around.

The primary current risk is therefore unlikely to come from US 5,980,882 itself. It is more likely to arise from later, product-specific patent families or regulatory exclusivities associated with a marketed resin-bound drug product.

Patent-strength assessment

Issue	Assessment
Technical concept	Specific and commercially relevant
Literal breadth	Moderate to narrow because of the drug list, EDTA requirement, and stability test
Composition coverage	Strongest for solid or gel products meeting every limitation
Process coverage	Potentially useful but dependent on order of addition and drying steps
Functional limitation	Important infringement hurdle and possible validity vulnerability
Drug coverage	Broad across six named drugs, with fallback claims for dextromethorphan and codeine
Formulation coverage	Broad dosage-form language, but limited by the drug-resin and EDTA requirements
Current enforceability	Appears low if the patent has expired
Design-around potential	Significant through alternative stabilizers, resins, dosage forms, or manufacturing sequences
Orange Book significance	Cannot be established from the patent number alone

Key Takeaways

US Patent 5,980,882 covers EDTA-stabilized drug-ion-exchange-resin complexes.
The core claims require more than EDTA; they require a greater-than-20% reduction in degradation over 12 months at room temperature.
The expressly named drugs are dextromethorphan, codeine, morphine, hydrocodone, pseudoephedrine, and phenylpropanolamine.
Dextromethorphan and codeine receive separate dependent-claim treatment.
The patent covers solid, gel, suspension, tablet, capsule, powder, lotion, cream, and suppository embodiments through different claim paths.
Manufacturing sequence matters, especially the timing of EDTA addition relative to drying and suspension.
The patent appears expired under the standard US 20-year term framework, but the exact terminal date requires review of the USPTO patent-term record.
No Orange Book listing, Paragraph IV challenge, settlement, litigation, or licensing deal is established by the supplied claims.
Current generic-entry risk is more likely to arise from later product-specific patents than from US 5,980,882.

FAQs About US Patent 5,980,882

Does US Patent 5,980,882 cover all EDTA-containing cough medicines?

No. The product must contain a drug-resin complex and one of the expressly named drugs, and the EDTA must produce the claimed degradation reduction.

Can a product avoid the patent by using a non-EDTA chelator?

Potentially, yes. The independent claims identify EDTA or an EDTA salt. A different chelating agent would generally avoid the literal chelator limitation, subject to the patent’s prosecution history and any doctrine-of-equivalents analysis.

Does the patent cover an uncoated dextromethorphan resin suspension?

It may, if the product satisfies the independent claim limitations. The diffusion-barrier and enteric-coating limitations are dependent claims and are not required by claim 1.

Is a drug-resin complex patent the same as a drug-composition patent?

No. This patent does not claim dextromethorphan, codeine, or the other drugs as chemical compounds. It claims particular pharmaceutical compositions and processes involving those drugs and ion-exchange resins.

Does patent expiration eliminate the need for FDA approval?

No. Patent expiration removes patent exclusivity but does not eliminate FDA requirements for an ANDA, NDA supplement, or other applicable regulatory pathway. Bioequivalence, quality, stability, labeling, and manufacturing requirements continue to apply.

References

United States Code. (2023). 35 U.S.C. §§ 154, 156. https://uscode.house.gov/
United States Patent and Trademark Office. (2024). Patent term calculator and patent term adjustment information. https://www.uspto.gov/
United States Court of Appeals for the Federal Circuit. (1999). Atlantic Thermoplastics Co. v. Faytex Corp., 159 F.3d 1347.
United States Code. (2023). 21 U.S.C. § 355. https://uscode.house.gov/
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book
U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions: Refuse-to-receive standards. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda/annual-reporting-and-paragraph-iv-certifications

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	2234282	⤷ Start Trial
European Patent Office	0911039	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,980,882

Summary for Patent: 5,980,882