United States Patent 10,231,931: Claim Scope, Patent Strength, and Levothyroxine Packaging Landscape

U.S. Patent No. 10,231,931 protects a narrowly defined packaged levothyroxine immediate-release solid dosage product. The claims combine tablet composition, package volume, tablet count, desiccant quantity, sealing conditions, and measured stability performance. The patent is not directed broadly to levothyroxine, HPMC, BHA, or desiccant packaging in isolation.

The core commercial risk is product-specific. A competing levothyroxine tablet could avoid the independent claims by changing the formulation, package size, tablet count, desiccant load, or stability profile. Claims 2-4 and 7-8 add nitrogen purging and, for claim 4, induction sealing. Claim 5 adds an accelerated-storage stability limitation.

What does U.S. Patent 10,231,931 protect?

The patent protects two package configurations:

Claim group	Dosage forms per container	Container volume	Desiccant	Stability requirement
Claims 1-5	About 90-100	About 55-125 cm³	At least about 6 g	At least 95% levothyroxine remaining after six months at about 23-27°C and 55-65% RH
Claim 5	About 90-100	About 55-125 cm³	At least about 6 g	At least 95% remaining after up to three months at about 38-42°C and 70-80% RH
Claims 6-8	About 900-1,000	About 225-360 cm³	At least about 16 g	At least 95% remaining after six months at about 23-27°C and 55-65% RH

The independent claims are product-by-process-like in commercial effect. They do not merely require a levothyroxine tablet and a bottle. They require a complete packaged product that satisfies specified quantitative and performance conditions.

The relevant patent is U.S. Patent No. 10,231,931. The legal analysis below is based on the supplied claims and the statutory framework governing patent infringement, patent term, pharmaceutical patent listing, and abbreviated new drug applications. [1-4]

How broad are the independent claims?

Claim 1 scope

Claim 1 requires all of the following:

An immediate-release oral solid dosage form.
About 0.1% to 1% levothyroxine salt by weight.
About 0.1% to 8% HPMC by weight.
About 0.01% to 5% BHA by weight.
A container with approximately 55-125 cm³ internal or specified volume.
A sealing closure.
Approximately 90-100 dosage forms in the container.
At least approximately 6 g of desiccant.
At least 95% retention of the initial levothyroxine salt after six months under the stated temperature and humidity conditions.

Every limitation must be met for literal infringement. A generic manufacturer could therefore create design-around positions by using fewer than 90 units, more than 100 units, a container outside the stated volume range, less than 6 g of desiccant, or a formulation outside one of the composition ranges.

The stability limitation creates a separate proof issue. The claim requires the packaged dosage forms to retain at least 95% of the initial levothyroxine salt under specified conditions. A product may fall within the composition and package ranges but avoid literal infringement if the claimed stability result is not demonstrated or does not occur.

Claim 6 scope

Claim 6 covers the larger-count commercial package. It requires:

900-1,000 dosage forms;
a 225-360 cm³ container;
at least 16 g of desiccant; and
six-month stability at approximately ambient temperature and moderate humidity.

Claim 6 does not recite BHA. It retains the levothyroxine salt and HPMC ranges but omits the BHA limitation present in claim 1. This omission materially broadens claim 6 relative to claim 1 from a formulation standpoint.

A product containing no BHA may still fall within claim 6 if it satisfies the levothyroxine, HPMC, packaging, quantity, desiccant, and stability limitations.

Which dependent claims add nitrogen purging and induction sealing?

Claims 2-4 narrow claim 1:

Claim	Added limitation
Claim 2	Container purged with an inert gas before sealing
Claim 3	Inert gas is nitrogen
Claim 4	Container is induction sealed after nitrogen purging

Claims 7 and 8 apply similar limitations to claim 6:

Claim	Added limitation
Claim 7	Container purged with inert gas before sealing
Claim 8	Inert gas is nitrogen

The dependent claims create narrower infringement positions but may be harder to enforce commercially because competitors can use ordinary air, carbon dioxide, another inert gas, or a different sealing method. A manufacturer that uses nitrogen but seals without induction may fall within claim 3 or claim 8, but not claim 4.

What formulation is protected by the patent?

Levothyroxine salt

The claims use the generic term “levothyroxine salt.” The supplied claim language does not limit the product to levothyroxine sodium. A formulation containing another pharmaceutically acceptable levothyroxine salt could potentially fall within the literal scope if the salt satisfies the concentration and stability requirements.

The relevant concentration is stated as a percentage by weight of the dosage form. The claims do not specify whether the percentage is calculated on an anhydrous basis, a salt basis, or another analytical basis. That issue may become important in claim construction and infringement testing.

HPMC

HPMC is required in both independent claims at approximately 0.1%-8% by weight. The claims do not specify:

HPMC viscosity grade;
substitution type;
particle size;
source;
manufacturing method; or
function within the tablet.

A tablet containing a low level of HPMC may satisfy the claims even if HPMC is used only as a binder or processing aid rather than as a release-control polymer. The “immediate release” limitation may constrain formulations that use HPMC at levels or grades that materially delay dissolution.

BHA

BHA is required by claim 1 and its dependents but not by claim 6 or its dependents. The claimed BHA range is approximately 0.01%-5% by weight, a broad range that covers low antioxidant concentrations commonly used for stabilization.

Claim 1 is therefore a combined formulation-and-package claim. Claim 6 is a package-and-stability claim with a narrower commercial package configuration but no BHA requirement.

What package configurations are covered?

The patent creates two distinct package-density regimes.

Small package

The first regime is approximately 90-100 tablets in a 55-125 cm³ container with at least 6 g of desiccant. The package has a relatively high desiccant-to-tablet ratio:

6 g per 90 tablets: approximately 66.7 mg per tablet;
6 g per 100 tablets: approximately 60 mg per tablet.

Large package

The second regime is approximately 900-1,000 tablets in a 225-360 cm³ container with at least 16 g of desiccant:

16 g per 900 tablets: approximately 17.8 mg per tablet;
16 g per 1,000 tablets: approximately 16 mg per tablet.

The large package contains roughly ten times as many tablets but only approximately 2.67 times the minimum desiccant quantity. This suggests that the claims distinguish package formats rather than applying one uniform desiccant ratio.

The claims do not expressly limit:

bottle material;
desiccant type;
desiccant placement;
closure material;
tablet shape;
tablet weight;
blister versus bottle presentation outside the claimed container system; or
commercial label strength.

A blister-packaged product would likely avoid these claims if it does not use the claimed container-and-closure configuration. Whether a blister system satisfies the “container” limitation would depend on claim construction and the patent’s specification.

How strong is the patent estate for levothyroxine packaging?

The patent has moderate claim strength against an exact-copy product and weaker strength against a deliberately engineered alternative.

Strength factors

The claims have several cumulative limitations that may make a direct design-around difficult:

specific dosage-form composition;
narrow package-volume bands;
defined tablet-count ranges;
minimum desiccant amounts;
required sealing closure;
quantified stability performance;
optional nitrogen purge; and
optional induction sealing.

A competitor may need to validate a different package design and conduct stability studies before launch. That creates a manufacturing and regulatory barrier even where literal infringement can be avoided.

Weakness factors

The same limitations reduce breadth. A competitor may avoid the independent claims by:

using a different HPMC concentration;
excluding HPMC;
excluding BHA where claim 1 is at issue;
changing the unit count;
selecting a bottle outside the claimed volume;
using a smaller desiccant quantity;
using a different package type;
adopting a different tablet composition; or
demonstrating that the product does not satisfy the 95% retention limitation.

The patent is stronger as a package-specific barrier than as a broad levothyroxine formulation patent.

What patents protect levothyroxine products beyond U.S. Patent 10,231,931?

The levothyroxine patent landscape generally divides into five categories.

Patent category	Typical protected subject matter	Relevance to Patent 10,231,931
Drug substance patents	Levothyroxine or salt forms	Usually limited relevance because levothyroxine is an established active ingredient
Formulation patents	Excipients, particle properties, dose uniformity, dissolution, stability	May overlap with the HPMC and BHA limitations
Packaging patents	Bottle volume, desiccant, closure, purge, moisture control	Directly adjacent and potentially overlapping
Method-of-use patents	Treatment of hypothyroidism or dosing methods	Separate from the claimed packaged product
Manufacturing patents	Blending, compression, coating, testing, packaging processes	Can create independent freedom-to-operate risks

The relevant competitive analysis must compare the claims of each patent family, not only the presence of levothyroxine in the product. A formulation patent may be infringed by the tablet before packaging. Patent 10,231,931 requires the final package and specified storage performance.

Is U.S. Patent 10,231,931 likely to be listed in the Orange Book?

A patent directed primarily to packaging may face listing limitations under FDA regulations. Orange Book listing generally focuses on patents claiming the approved drug substance, drug product, or an approved method of use. Packaging-only claims may not qualify for listing in the same manner as composition or method-of-use patents. [3]

The supplied claims are directed to a packaged product, not solely to a method of manufacture. That distinction can support a listing argument, but the exact Orange Book status depends on the approved application, patent-listing submission, FDA review, and the patent’s relationship to the reference-listed drug.

An Orange Book-listed patent can support a Paragraph IV notice and a 30-month stay under the Hatch-Waxman framework. A patent that is not listed may still be asserted in district court but generally will not create the same ANDA certification and automatic-stay consequences. [2-4]

When does Patent 10,231,931 lose exclusivity?

The patent’s enforceable term is generally calculated from the applicable earliest nonprovisional U.S. filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and other statutory adjustments. The issue date alone does not establish the expiration date. [5]

The relevant commercial dates are:

Event	Business significance
Patent grant	Patent became enforceable against post-grant infringement, subject to statutory requirements
Patent-term adjustment	May extend the ordinary 20-year term
Terminal disclaimer	May shorten the term if the patent is tied to an earlier-expiring patent
Patent-term extension	Potentially relevant for qualifying regulatory delay, although packaging patents generally present a limited basis for extension
Expiration	Ends ordinary U.S. patent exclusion rights, subject to accumulated damages and other remedies

A precise expiration date requires the USPTO patent record, including the earliest priority and nonprovisional filing dates, PTA, PTE, and any terminal disclaimer. The claim text does not establish those dates.

What generic entry risks exist for levothyroxine products?

ANDA certification risk

If the patent is listed against a reference product, an ANDA applicant may need to address it through:

Paragraph I certification, if no relevant patent is listed;
Paragraph II certification, if the patent has expired;
Paragraph III certification, if the applicant will wait for expiration; or
Paragraph IV certification, if the applicant asserts that the patent is invalid, unenforceable, or not infringed.

A Paragraph IV certification can trigger patent litigation and, for a listed patent, potentially a 30-month approval stay under the Hatch-Waxman Act. [2]

Infringement-testing risk

The applicant would need to test at least:

levothyroxine salt percentage;
HPMC percentage;
BHA percentage;
bottle volume;
tablet count;
desiccant mass;
closure and sealing method;
nitrogen or other inert-gas purge; and
stability under the claimed storage conditions.

The stability limitations create a special risk. A product may initially be designed outside the claim but later change during scale-up, commercial packaging, or post-approval manufacturing.

Launch scenarios

Launch design	Likely risk profile
100 tablets, 60-125 cm³ bottle, 6 g desiccant, HPMC and BHA	High risk under claim 1 if stability limitation is met
100 tablets with 5 g desiccant	Potential literal design-around, subject to claim construction and equivalents
90-100 tablets in a blister pack	Lower risk under the container-closure claims
1,000 tablets in 225-360 cm³ bottle with 16 g desiccant and HPMC	High risk under claim 6 if stability limitation is met
1,000 tablets with no HPMC	Potential design-around for claim 6
Nitrogen-purged bottle	Risk under claims 2-3 or 7-8 if the base claim is met
Nitrogen purge plus induction seal	Highest risk under claim 4 where claim 1 is otherwise satisfied

The doctrine of equivalents could limit the value of marginal changes, especially changes made solely to avoid a numerical limitation. Courts evaluate equivalence limitation by limitation, and prosecution history may restrict available equivalents. [6]

What litigation or settlement agreements affect the patent?

The supplied claim text does not establish any infringement case, Paragraph IV notice, settlement agreement, license, or covenant not to sue involving Patent 10,231,931. Those matters are separate from claim scope and must be confirmed through USPTO records, PACER, FDA patent listings, and company disclosures.

No licensing conclusion should be drawn solely from the existence of the patent. A patent owner may license manufacturing technology without listing the agreement publicly, while a settlement may include confidential commercial terms, launch dates, or restrictions not visible in the patent record.

How does this patent compare with ordinary levothyroxine formulation patents?

Patent 10,231,931 differs from a conventional formulation patent in three ways.

First, it requires a finished package rather than only a tablet composition. Second, it relies on package geometry and desiccant loading. Third, it includes an empirical stability result as a claim limitation.

That structure can make infringement more difficult to detect from a public label. A competitor’s tablet label may disclose levothyroxine strength and inactive ingredients but not bottle volume, desiccant mass, nitrogen purging, or long-term stability data.

The patent therefore has stronger trade-secret and inspection implications than an ordinary excipient patent. Package teardown, regulatory submissions, manufacturing records, and stability reports may be relevant in an infringement investigation.

Key Takeaways

U.S. Patent 10,231,931 is a narrow packaged-product patent for immediate-release levothyroxine solid dosage forms.
Claim 1 requires levothyroxine salt, HPMC, BHA, a 55-125 cm³ container, 90-100 dosage forms, at least 6 g of desiccant, and six-month stability.
Claim 6 covers 900-1,000 dosage forms in a 225-360 cm³ container with at least 16 g of desiccant and does not require BHA.
Nitrogen purging and induction sealing are dependent-claim limitations, not requirements of the independent claims.
The patent is potentially strong against an exact-copy bottle configuration but vulnerable to formulation, package-count, container-volume, desiccant, or dosage-form changes.
Orange Book treatment cannot be inferred solely from the claims because packaging-related listing eligibility depends on the approved drug application and FDA listing requirements.
A precise expiration date requires the USPTO term record, including priority, PTA, PTE, and terminal-disclaimer data.
Generic applicants should treat the patent as a package-and-stability risk distinct from levothyroxine drug-substance and formulation patents.

FAQs

Can a levothyroxine tablet avoid Patent 10,231,931 by using calcium silicate instead of HPMC?

Yes, potentially. Claims 1 and 6 require HPMC within the stated range. A formulation without HPMC would not literally satisfy that limitation, although other patent claims or the doctrine of equivalents could remain relevant.

Does a 30-count levothyroxine bottle infringe the patent?

The supplied independent claims require approximately 90-100 or 900-1,000 dosage forms. A 30-count bottle would generally fall outside those quantity limitations, subject to claim construction and any additional claims not supplied.

Does the patent cover levothyroxine capsules?

The claims recite an immediate-release oral solid dosage form, not expressly tablets. Capsules could potentially fall within the claim if they meet every composition, package, quantity, and stability limitation.

Is BHA required for the large 900-1,000-count package?

No. Claim 6 does not recite BHA. The large-package claims require levothyroxine salt and HPMC but omit the BHA limitation found in claim 1.

Can a manufacturer avoid the patent by using a 4 g desiccant canister?

A 4 g desiccant load is below the “at least about 6 grams” limitation in claims 1-5 and below the “at least about 16 grams” limitation in claims 6-8. That may provide a literal noninfringement position, but the result depends on construction of “about,” prosecution history, and any equivalents analysis.

References

United States Patent No. 10,231,931, claims 1-8. U.S. Patent and Trademark Office.
Drug Price Competition and Patent Term Restoration Act of 1984, 21 U.S.C. § 355(j).
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations (Orange Book).
U.S. Food and Drug Administration. (2016). Applications for FDA approval to market a new drug: Patent submission and listing requirements, 21 C.F.R. § 314.53.
Patent Act, 35 U.S.C. §§ 154, 156.
Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997).

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Genus Lifesciences	LEVOLET	levothyroxine sodium	TABLET;ORAL	021137-003	Jun 6, 2003	AB1,AB2,AB3,AB4	RX	No	No	10,231,931	⤷ Start Trial	Y				⤷ Start Trial
Genus Lifesciences	LEVOLET	levothyroxine sodium	TABLET;ORAL	021137-004	Jun 6, 2003	AB1,AB2,AB3,AB4	RX	No	No	10,231,931	⤷ Start Trial	Y				⤷ Start Trial
Genus Lifesciences	LEVOLET	levothyroxine sodium	TABLET;ORAL	021137-005	Jun 6, 2003	AB1,AB2,AB3,AB4	RX	No	No	10,231,931	⤷ Start Trial	Y				⤷ Start Trial
Genus Lifesciences	LEVOLET	levothyroxine sodium	TABLET;ORAL	021137-006	Jun 6, 2003	AB1,AB2,AB3,AB4	RX	No	No	10,231,931	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Details for Patent: 10,231,931

Which drugs does patent 10,231,931 protect, and when does it expire?

Summary for Patent: 10,231,931