United States Patent 8,846,091: Oxycodone/Naloxone Formulation Scope, Validity and Patent Landscape

U.S. Patent No. 8,846,091 protects a controlled-release oral formulation combining oxycodone and naloxone in a 2:1 weight ratio within an ethylcellulose/fatty-alcohol diffusion matrix. The broadest independent claim requires all of the following: oxycodone at 10-150 mg, naloxone, ethylcellulose at 1%-15% of the total formulation, at least one fatty alcohol at 10%-25%, and sustained, invariant and independent release of both active ingredients. The dependent claims narrow the estate toward oxycodone hydrochloride, naloxone hydrochloride, stearyl alcohol, tablet dosage forms, and defined release uniformity.

The patent is formulation-specific. It does not cover oxycodone/naloxone products generally, nor does it cover every extended-release opioid combination. A competing product that changes the matrix architecture, active-ingredient ratio, release profile, or excipient ranges may avoid literal infringement, subject to equivalents and claim construction.

What does U.S. Patent 8,846,091 protect?

The patent protects a pharmaceutical formulation rather than a therapeutic indication or a manufacturing process. Claim 1 is the controlling scope provision.

Required limitation in claim 1	Scope
Dosage form	Oral formulation
Opioid	Oxycodone or a pharmaceutically acceptable salt
Oxycodone quantity	10-150 mg
Antagonist	Naloxone or a pharmaceutically acceptable salt
Ratio	Oxycodone:naloxone at 2:1 by weight
Matrix	Diffusion matrix
Ethylcellulose	1%-15% by total formulation weight
Fatty alcohol	10%-25% by total formulation weight
Release	Sustained, invariant and independent release of both actives

The claim is cumulative. An accused product must satisfy every limitation of claim 1, either literally or under the doctrine of equivalents, for direct infringement to be established.

What is the core inventive concept?

The core concept is a diffusion-controlled matrix intended to release oxycodone and naloxone at coordinated rates despite the different physicochemical properties of the two compounds. The matrix uses ethylcellulose and a fatty alcohol as the principal release-controlling components.

The specification's technical distinction is important. The patent does not merely require an extended-release oxycodone tablet containing naloxone. It requires a matrix that provides:

Sustained release over time.
Invariant release behavior.
Independent release of oxycodone and naloxone.
Comparable percentage release per unit of time.

These functional limitations may create both infringement leverage and validity exposure. They narrow the practical claim scope, but they can also raise questions about objective measurement, claim construction and enablement.

How do claims 2 through 20 narrow the patent?

Claims 2-20 create a commercially focused set of fallback positions.

Claims	Limitation
2	Oxycodone hydrochloride
3	Oxycodone hydrochloride and naloxone hydrochloride
4	Naloxone hydrochloride
5	Oxycodone at 10-80 mg
6	Oxycodone at 10-40 mg
7	Oxycodone at 10-30 mg
8	Ethylcellulose at 3%-12%
9	Ethylcellulose at 5%-9%
10	Fatty alcohol at 15%-20%
11	Specified fatty alcohols
12	Stearyl alcohol
13	Stearyl alcohol with 10-80 mg oxycodone
14	Stearyl alcohol with 10-40 mg oxycodone
15	Equal percentage release per time unit
16	No more than 20% deviation from mean release
17	Matrix not based on polymethacrylate
18	No relevant amount of hydroxyalkylcellulose
19	Release characteristics determined by ethylcellulose and fatty alcohol
20	Tablet

The commercially significant fallback combination is claims 3, 7, 9, 12, 16 and 20: a tablet containing oxycodone hydrochloride and naloxone hydrochloride, with 10-30 mg oxycodone, 5%-9% ethylcellulose, stearyl alcohol, and release variability of no more than 20%.

What formulations are protected by U.S. Patent 8,846,091?

A formulation is most exposed when it has the following profile:

Oxycodone hydrochloride and naloxone hydrochloride.
A 2:1 oxycodone-to-naloxone ratio.
Oxycodone strength between 10 mg and 30 mg.
Ethylcellulose between 5% and 9% by total weight.
Stearyl alcohol between 10% and 25%.
A non-polymethacrylate diffusion matrix.
No material amount of hydroxyalkylcellulose.
Tablet presentation.
Matched percentage release of the two actives.

A formulation outside one numerical range may avoid literal infringement of the relevant claim, but it may remain exposed under claim 1 if it falls within the broader ranges. For example, a tablet containing 12% ethylcellulose and 18% stearyl alcohol may avoid claims 9 and 10 but remain within claim 1 and claim 8.

Does the patent cover Targiniq ER or other oxycodone/naloxone products?

The claim architecture is directed to the same general product concept as prolonged-release oxycodone/naloxone products, including products containing oxycodone hydrochloride and naloxone hydrochloride at a 2:1 ratio. That does not establish that every marketed product infringes, because infringement depends on the specific formulation, matrix excipients, quantitative composition and release data.

Targiniq ER was approved by the FDA as an extended-release oxycodone/naloxone product with abuse-deterrent properties. Its regulatory approval does not itself establish infringement of U.S. Patent 8,846,091. FDA labeling and Orange Book information must be compared with the patent's formulation limitations. [2][3]

How should the 2:1 oxycodone-to-naloxone ratio be interpreted?

The ratio is a central limitation. The claim language states that oxycodone and naloxone, or their pharmaceutically acceptable salts, are present in a weight ratio of 2:1.

The principal interpretive issue is whether the ratio is measured:

On the basis of the active moieties;
On the basis of the hydrochloride salts as weighed; or
On another formulation accounting basis disclosed in the specification.

Oxycodone hydrochloride and naloxone hydrochloride have different molecular weights from their respective free bases. A product designed around a 2:1 active-moiety ratio may not have a 2:1 salt-to-salt weight ratio. This distinction can materially affect infringement analysis.

A generic applicant or competing developer would need to assess the patent's specification, prosecution history and any claim-construction record before relying on a salt-basis distinction.

What is the significance of the release limitations?

Claims 1, 15, 16 and 19 contain the patent's principal functional limitations.

"Sustained" release indicates prolonged delivery rather than immediate release. "Invariant" release suggests reproducibility over the relevant release period. "Independent" release indicates that one active ingredient's release is not materially dependent on the release behavior of the other.

Claim 16 provides the clearest quantitative limitation: no more than 20% deviation from the mean release value for either active ingredient. The claim does not, from the text supplied, identify every testing parameter needed to calculate that deviation, including:

Dissolution apparatus;
Medium and pH;
Agitation rate;
Sampling intervals;
Number of dosage units;
Duration of the test; and
Whether the comparison is based on absolute mass release or percentage release.

Those parameters can become central in litigation. A patent owner would typically use dissolution testing and formulation composition data to establish infringement. An accused party would challenge the test method, the meaning of "equal percentage release," and whether the claim requires a particular degree of synchronization throughout the entire dissolution period.

How strong is the patent estate for oxycodone/naloxone formulations?

The patent has moderate formulation value but narrower breadth than a composition-of-matter patent.

Strengths

It targets the commercially important 2:1 oxycodone/naloxone architecture.
It covers a broad initial oxycodone range of 10-150 mg.
It covers several fatty alcohols, not only stearyl alcohol.
It includes both broad and narrow ethylcellulose ranges.
It has fallback claims directed to hydrochloride salts and tablet products.
It excludes polymethacrylate-based matrices and material hydroxyalkylcellulose use, potentially distinguishing common controlled-release systems.

Limitations

It requires both ethylcellulose and a fatty alcohol in specified concentration ranges.
It requires a diffusion matrix rather than any extended-release technology.
The 2:1 ratio may exclude products using different antagonist loading.
The functional release limitations may be difficult to prove consistently.
A nonmatrix delivery system, multiparticulate system or chemically distinct controlled-release platform may avoid literal infringement.
The claim does not cover naloxone-free oxycodone products or oxycodone products using a different antagonist.

The patent is therefore strongest against close formulation copies and weaker against redesigned products using different release polymers, coating systems, ratios or dosage-form technologies.

When does U.S. Patent 8,846,091 lose exclusivity?

U.S. Patent 8,846,091 issued on September 30, 2014. Its likely ordinary patent-term endpoint is approximately 2029, calculated from the relevant earliest nonprovisional or international filing date, subject to patent-term adjustment, terminal disclaimers and any legally applicable corrections. The exact expiration date should be taken from the USPTO patent record and the patent's term calculation.

Event	Date or status
U.S. patent	8,846,091
Issue date	September 30, 2014
Patent type	Utility patent
Subject matter	Oxycodone/naloxone controlled-release formulation
Expected term	Approximately 2029, subject to USPTO term calculation
Regulatory exclusivity	Separate from patent term
Pediatric exclusivity	Must be confirmed from FDA records
Orange Book impact	Depends on FDA listing and active NDA association

Patent expiration does not automatically authorize launch. Other patents, regulatory exclusivity, litigation injunctions, regulatory requirements and product-specific patents may affect market entry.

What is the Orange Book status of U.S. Patent 8,846,091?

The Orange Book listing question must be analyzed separately from patent validity. FDA lists patents submitted by NDA sponsors for approved drug products. A patent can be valid and enforceable without being listed in the Orange Book, particularly where the patent is not submitted for an approved product or does not claim the drug, formulation or approved method of use in a listing-eligible manner. [3]

For an oxycodone/naloxone product, the relevant inquiry is whether U.S. Patent 8,846,091 is listed against the applicable NDA and whether the listing remains active. FDA's electronic Orange Book and patent-listing data, rather than the patent document alone, control the listing analysis.

If listed, a generic applicant submitting an ANDA may need to address the patent with a Paragraph IV certification unless it accepts a later launch date. If not listed, the patent may still support a separate infringement action, but the ANDA certification and automatic-stay framework may differ.

What Paragraph IV challenges and litigation affect the patent?

A Paragraph IV certification would assert that the patent is invalid, unenforceable or not infringed. For this patent, likely technical grounds would include:

Lack of novelty over earlier oxycodone/naloxone matrix disclosures;
Obviousness based on known opioid matrices, ethylcellulose systems and fatty alcohol excipients;
Indefiniteness of "sustained, invariant, and independent release";
Indefiniteness or lack of written support for "equal percentage release per time unit";
Enablement challenges across the full 10-150 mg and excipient ranges;
Noninfringement based on a different ratio, matrix, excipient concentration or release profile.

A complete litigation conclusion cannot be drawn from the claim text alone. Patent litigation status, settlements and Paragraph IV activity are separate database questions and must be tied to the relevant NDA, patent listing and district-court docket.

Which companies are relevant to the competitive landscape?

The principal commercial and patent stakeholders include:

Company or entity	Relevance
Grünenthal GmbH	Associated with oxycodone/naloxone controlled-release technology and related patent activity
Purdue Pharma	U.S. developer and marketer associated with Targiniq ER
FDA	NDA approval, labeling, Orange Book and regulatory exclusivity
Generic drug applicants	Potential ANDA filers and Paragraph IV challengers
Specialty formulation companies	Potential competitors using alternative matrices or multiparticulate systems

The competitive risk is not limited to direct generic substitution. A company may design around the patent with a coated multiparticulate, osmotic system, polymethacrylate matrix, hydroxyalkylcellulose matrix, different opioid-antagonist ratio, or non-tablet oral dosage form.

What manufacturing and intellectual-property barriers remain?

The patent's manufacturing relevance lies in controlling excipient distribution and achieving reproducible dissolution behavior. A developer must manage:

Uniform dispersion of ethylcellulose;
Fatty alcohol particle size and melting behavior;
Drug loading across the 10-150 mg range;
Matrix compression and tablet hardness;
Stability of oxycodone and naloxone salts;
Batch-to-batch release matching;
Dissolution-method sensitivity.

Manufacturing know-how may remain valuable even after patent expiration. Process parameters, granulation conditions, excipient grades and dissolution controls may be protected through trade secrets or separate process patents.

How does this patent compare with abuse-deterrent oxycodone patents?

U.S. Patent 8,846,091 is primarily a controlled-release and dual-active formulation patent. Abuse-deterrent patents may instead focus on tablet hardness, gelling, resistance to crushing, chemical barriers, tamper-resistant dosage forms or extraction-resistant matrices.

The technologies can overlap in one product, but they protect different technical features:

Patent category	Principal protection
U.S. 8,846,091-type claims	Oxycodone/naloxone matrix composition and matched release
Abuse-deterrent claims	Physical or chemical resistance to manipulation
Method-of-use claims	Treatment, abuse prevention or reduced opioid exposure
Manufacturing claims	Granulation, compression, coating or matrix-production process
Regulatory exclusivity	FDA approval rights, not formulation ownership

A product could avoid U.S. Patent 8,846,091 yet infringe a separate abuse-deterrent patent, or satisfy this patent while avoiding other formulation claims.

What generic launch risks exist?

The highest-risk generic design would replicate the patented profile: a 2:1 oxycodone/naloxone tablet using oxycodone hydrochloride, naloxone hydrochloride, 5%-9% ethylcellulose and stearyl alcohol in a diffusion matrix.

Potential design-around routes include:

Changing the oxycodone-to-naloxone ratio.
Moving ethylcellulose below 1% or above 15%.
Eliminating the fatty alcohol.
Replacing the diffusion matrix with a coating, osmotic system or multiparticulate platform.
Using a polymethacrylate-based matrix.
Using a material amount of hydroxyalkylcellulose.
Adopting a non-tablet oral dosage form.
Producing materially different release profiles.

Each route creates technical and regulatory consequences. A formulation outside the patent may require a different bioequivalence strategy, different abuse-deterrence data or a new clinical bridging package.

Key Takeaways

U.S. Patent 8,846,091 is a formulation patent covering a 2:1 oxycodone/naloxone controlled-release diffusion matrix.
Claim 1 requires ethylcellulose at 1%-15%, a fatty alcohol at 10%-25%, and oxycodone at 10-150 mg.
The strongest commercial fallback claims target hydrochloride salts, stearyl alcohol, 10-30 mg oxycodone, 5%-9% ethylcellulose and tablet dosage forms.
Release synchronization is a material limitation, not merely a product-performance aspiration.
The patent is most relevant to close copies of prolonged-release oxycodone/naloxone tablets.
Alternative ratios, matrix systems, polymers and dosage forms may create design-around opportunities.
The patent issued September 30, 2014, with an expected ordinary term extending approximately to 2029, subject to the USPTO term calculation.
Orange Book listing, Paragraph IV activity, settlements and current litigation must be evaluated against the relevant NDA and FDA records.
FDA approval of an oxycodone/naloxone product does not by itself establish infringement or freedom to operate.

Frequently Asked Questions

Does U.S. Patent 8,846,091 cover immediate-release oxycodone/naloxone?

No. The claims require a diffusion matrix configured for sustained release. An immediate-release combination would not satisfy the release limitations.

Is stearyl alcohol required in every claim?

No. Claim 1 covers at least one fatty alcohol within the stated range. Stearyl alcohol is required only in claims 12-14 and not in the broadest claim.

Can a product with a 1:1 oxycodone/naloxone ratio infringe?

It would not literally satisfy the express 2:1 ratio limitation. Equivalents analysis could still be relevant, depending on the facts and the legal record.

Does using naloxone base instead of naloxone hydrochloride avoid the patent?

Not necessarily. The independent claim covers naloxone and pharmaceutically acceptable salts. The effect of changing the salt form also depends on how the 2:1 weight ratio is construed.

Does patent expiration eliminate all oxycodone/naloxone launch barriers?

No. Other patents, FDA regulatory requirements, product-specific exclusivity, litigation orders, manufacturing patents and regulatory approval conditions may remain relevant.

References

United States Patent and Trademark Office. (2014). U.S. Patent No. 8,846,091, pharmaceutical formulation comprising oxycodone and naloxone.
U.S. Food and Drug Administration. (2014). Targiniq ER prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	102 15 067	Apr 5, 2002
Germany	102 15 131	Apr 5, 2002

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
African Regional IP Organization (ARIPO)	2043	⤷ Start Trial
African Regional IP Organization (ARIPO)	2397	⤷ Start Trial
Argentina	039378	⤷ Start Trial
Argentina	039379	⤷ Start Trial
Argentina	090677	⤷ Start Trial
Argentina	099437	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,846,091

Summary for Patent: 8,846,091