US Patent 6,031,007: Claim Scope, Expiration, Orange Book Status, and Patent Landscape

US Patent 6,031,007 protects a thermoreversible emulsion or microemulsion containing oil-phase local anesthetic, water, and at least one thermogelling surfactant. The strongest commercial embodiment is a periodontal formulation containing a eutectic lidocaine-prilocaine mixture and Poloxamer 188 and Poloxamer 407. The patent also covers specified concentration ranges, pH conditions, manufacturing processes, and use in periodontal scaling.

The patent’s ordinary US term has expired. It therefore does not provide current US blocking exclusivity, although its claim structure remains relevant to freedom-to-operate analysis, invalidity research, prior-art mapping, and assessment of historical protection for Oraqix-type products.

What does US Patent 6,031,007 protect?

The patent claims a temperature-responsive local-anesthetic formulation. At room temperature, the composition is sufficiently fluid for administration. After contact with a mucous membrane, the formulation becomes more viscous because of the thermoreversible gelling behavior of the surfactant system.

The independent composition claim requires all of the following elements:

Required element	Claim requirement
Local anesthetic	One or more local anesthetics in oil form
Surfactant	One or more surfactants in an amount effective to produce a homogeneous formulation
Thermogelling component	At least one surfactant has thermoreversible gelling properties
Aqueous phase	Water
Physical form	Emulsion or microemulsion
Rheology	Less viscous at room temperature than after introduction onto a patient’s mucous membrane

The claim is narrower than a generic local-anesthetic gel claim. It requires a particular combination of composition, physical form, and temperature-dependent viscosity behavior.

The patent does not require a particular local anesthetic in claim 1. Later claims narrow the formulation to particular concentration ranges, eutectic mixtures, surfactants, and manufacturing methods.

How broad is independent claim 1?

Claim 1 has four principal limitations that determine its practical scope.

Oil-phase local anesthetic

The anesthetic must be present in oil form. This language distinguishes the claimed formulation from an aqueous solution in which the anesthetic is dissolved predominantly in the water phase.

The claim can potentially cover:

Lidocaine;
Prilocaine;
Other oil-compatible local anesthetics;
Combinations of local anesthetics;
Eutectic local-anesthetic mixtures.

The claim does not require lidocaine or prilocaine unless a dependent claim is asserted.

The phrase “in oil form” may create an infringement issue for products in which the active ingredient is present as a salt, is fully solubilized in water, or is incorporated into a separate delivery system rather than an oil phase. The technical characterization of the finished formulation would be material.

Thermoreversible gelling surfactant

At least one surfactant must have thermoreversible gelling properties. Claims 10 through 12 identify nonionic surfactants and poloxamers, with claim 12 specifically requiring Poloxamer 188 and Poloxamer 407.

The patent’s central technical concept is the use of a surfactant system that remains comparatively fluid during handling but gels or becomes more viscous at physiological temperature. This supports retention in a periodontal pocket or on a mucous membrane.

A formulation that uses a mucoadhesive polymer, carbomer, cellulose derivative, or crosslinked hydrogel without a thermogelling surfactant may avoid the literal surfactant limitation, depending on the formulation’s composition and prosecution history.

Emulsion or microemulsion

The composition must be an emulsion or microemulsion. A conventional aqueous solution, suspension, anhydrous gel, liposome, or solid implant is not within the literal language of claim 1 unless it also satisfies the emulsion or microemulsion requirement.

The patent does not appear to require a particular droplet size, phase ratio, particle-size distribution, or surfactant-to-oil ratio in claim 1. Those parameters may become relevant to claim construction and infringement proof, particularly where a competing product is described as a “gel” rather than an emulsion.

Temperature-dependent viscosity

The composition must be less viscous at room temperature than after introduction onto a mucous membrane. This functional limitation links the claim to the product’s rheological performance.

An accused product would likely require testing at defined temperatures and shear conditions. A product that thickens because of evaporation, ionic crosslinking, pH change, or irreversible polymerization may present a noninfringement argument if the increase is not caused by thermoreversible gelling.

What dependent claims add to the patent scope?

The dependent claims create several fallback positions.

Claims	Subject matter
2	Taste-masking agents
3	Local anesthetic concentration of 0.5% to 20% by weight
4	Local anesthetic concentration of 2% to 7% by weight
5-6	Eutectic local-anesthetic mixture, including lidocaine and prilocaine
7	A local anesthetic represented by the chemical structure in the patent
8	More than one surfactant, with at least one thermogelling surfactant
9	Total surfactant concentration up to 50% by weight
10	Nonionic surfactant
11	Poloxamer
12	Poloxamer 188 and Poloxamer 407
13	Treatment of periodontal-scaling pain
14-15	Two alternative manufacturing processes
16	Combined concentration ranges for anesthetic and surfactant
17	pH at least pKa minus one

Claim 7 cannot be fully analyzed from the text supplied because the chemical structure is represented only by the placeholder “##STR2##.” Its scope depends on the actual structure and the corresponding specification disclosure.

What formulation is most closely associated with the patent?

The commercially important embodiment is an aqueous thermoreversible periodontal formulation containing:

Lidocaine;
Prilocaine;
Poloxamer 188;
Poloxamer 407;
Water;
A pH-adjusting system and excipients.

Oraqix is a 2.5% lidocaine and 2.5% prilocaine periodontal gel marketed for local anesthesia in periodontal pockets. The FDA labeling describes its use during scaling and root planing and identifies Dentsply Pharmaceutical as the applicant or sponsor associated with the US approval. The formulation corresponds closely to the subject matter of claims 6 and 12, although product-specific infringement requires analysis of every limitation and the relevant patent file history (U.S. Food and Drug Administration, 2003).

The 5% combined local-anesthetic concentration is within the 2% to 7% range of claim 4 and within the 0.5% to 20% range of claim 3.

What do the method-of-use and manufacturing claims cover?

Periodontal-scaling use

Claim 13 covers applying an effective amount of the composition to a periodontal pocket to treat pain associated with periodontal scaling.

This claim is narrower than a general oral-anesthesia claim. It requires:

A patient;
Pain associated with periodontal scaling;
Application to the periodontal pocket; and
The composition of claim 1.

A competing product used for topical oral anesthesia, dental injections, mucosal anesthesia, or treatment of unrelated pain may fall outside claim 13 even if it satisfies the composition limitations.

The claim is also subject to the legal limits applicable to method-of-treatment claims, including direct infringement requirements and the evidentiary difficulty of proving a third party’s specific clinical use.

Manufacturing processes

Claims 14 and 15 protect two process variants.

Claim 14 applies where the composition contains more than one surfactant. The process requires:

Melting the anesthetic with the lowest-molecular-weight surfactant;
Adding water during homogenization to form an emulsion concentrate;
Separately dispersing the remaining surfactant or surfactants in water;
Combining the emulsion concentrate and surfactant solution;
Adjusting pH to at least pKa minus one; and
Adding water to final weight.

Claim 15 applies where only one surfactant is used. It requires melting the anesthetic and surfactant together, adding water during homogenization, adjusting pH, and bringing the composition to final weight.

These claims are process-specific. A manufacturer that uses a cold-mixing process, solvent evaporation, high-pressure homogenization, premixed surfactants, or a different pH-adjustment sequence may avoid literal infringement. The doctrine of equivalents would depend on the prosecution history and the importance of the ordered process steps.

How does the pH limitation affect infringement?

Claim 17 requires a pH greater than or equal to pKa minus one, using the local anesthetic with the lowest pKa.

This limitation helps preserve sufficient unionized anesthetic for partitioning into tissue while maintaining formulation stability. It also provides a measurable claim boundary.

For a lidocaine-prilocaine composition, the relevant value would be based on the lower pKa of the two active ingredients. A formulation outside the specified pH relationship would not literally meet claim 17, although claims 1 through 16 would need to be assessed separately because most do not expressly contain the pH limitation.

The pH limitation is therefore a dependent-claim limitation, not a universal limitation of the core composition claim.

When did US Patent 6,031,007 expire?

US Patent 6,031,007 issued on February 29, 2000. Its US term ran for approximately 20 years from the relevant nonprovisional filing date, subject to any applicable patent-term adjustment or extension. Public patent records identify the patent as expired, with the ordinary term ending in 2016.

Event	Date or status
US patent number	6,031,007
Issue date	February 29, 2000
Ordinary US patent term	Approximately 20 years from the relevant filing date
Commercial relevance	Oraqix-type periodontal anesthetic formulations
Current US status	Expired
Current blocking exclusivity	None from this patent

The patent’s expiration means that a current US manufacturer generally cannot be excluded solely on the basis of US Patent 6,031,007. Expiration does not eliminate the value of the patent for historical validity analysis or for identifying related family members that may have had different expiration dates outside the United States.

What was the Orange Book status of the patent?

The patent was associated with the Oraqix regulatory and commercial record. FDA Orange Book listings are product-specific and may change through administrative updates. The Orange Book distinguishes listed patents from regulatory exclusivity and does not itself determine infringement or validity.

For an Oraqix-related abbreviated new drug application, a listed patent could historically have supported:

A Paragraph IV certification;
A Paragraph III certification if the patent had not yet expired;
A Paragraph II certification if the patent had already expired; or
A certification based on noninfringement, invalidity, or unenforceability.

Because US Patent 6,031,007 has expired, it cannot now create a live Paragraph IV launch barrier. Any current generic applicant would need to examine the current Orange Book entry, if any, and all other listed patents separately.

Were there Paragraph IV challenges or patent litigation?

The patent landscape for a generic Oraqix product would have been shaped by the short product market, the specialized periodontal indication, and the limited number of commercially relevant formulations. A Paragraph IV challenge could target:

Whether the accused product is an emulsion or microemulsion;
Whether the anesthetic is present in oil form;
Whether the surfactant is thermoreversible;
Whether the product becomes more viscous at mucosal temperature;
Whether the product contains Poloxamer 188 and Poloxamer 407;
Whether the process follows the claimed melting and homogenization sequence; and
Whether the pH satisfies claim 17.

No current US enforcement threat arises from Patent 6,031,007 because the patent has expired. A complete litigation conclusion requires review of PACER, district-court docket records, Federal Circuit decisions, and the patent’s prosecution history. The supplied claim text alone does not establish that a particular Paragraph IV case or settlement occurred.

How strong was the patent estate?

The patent had meaningful historical strength for a narrowly defined product but limited breadth outside that formulation architecture.

Strength factor	Assessment
Core formulation concept	Strongly defined by the combination of oil-phase anesthetic, water, emulsion or microemulsion, and thermogelling surfactant
Product specificity	High for lidocaine-prilocaine and poloxamer formulations
Concentration coverage	Broad at 0.5% to 20%, with narrower 2% to 7% fallback
Surfactant coverage	Broad in claim 1, narrower in claims 10-12
Method-of-use coverage	Narrow, focused on periodontal scaling
Manufacturing coverage	Narrower because of ordered process steps
Design-around potential	Moderate to high using non-emulsion systems, nonthermogelling polymers, different phase behavior, or different processing
Current enforceability	None in the United States because the patent expired

The principal vulnerability would have been prior art involving topical anesthetic emulsions, poloxamer thermogels, mucosal drug delivery, and temperature-responsive pharmaceutical vehicles. The patent’s strongest position would have been the specific combination of features rather than any individual ingredient.

What patent and competitive risks exist for generic entry?

A generic or follow-on product could pursue several design strategies:

Non-emulsion formulation

A true aqueous solution, suspension, or polymeric gel may avoid the emulsion limitation. The product would still require separate evaluation for other patent families and regulatory equivalence.

Alternative thermogelling system

A formulation using a different temperature-sensitive polymer or delivery mechanism may avoid claims directed to surfactant-based thermoreversible gelling. The product could still face broader formulation or method patents.

Different local anesthetic

Replacing the lidocaine-prilocaine eutectic with another anesthetic may avoid claims 5 and 6, but not necessarily claim 1, which is not limited to that combination.

Different manufacturing sequence

Changing the order of melting, hydration, homogenization, and pH adjustment may avoid claims 14 and 15 if the process does not meet the specified sequence.

Different clinical indication

A product used for general oral pain, injection anesthesia, or nonperiodontal procedures may avoid claim 13. The composition claims would remain relevant unless the formulation itself is outside the claimed scope.

How does this patent compare with biosimilar and generic risks?

This is a small-molecule drug patent, not a biologic patent. Biosimilar approval under the Public Health Service Act is not relevant. The appropriate regulatory pathway is an abbreviated new drug application or, depending on the product and formulation differences, a 505(b)(2) application under the Federal Food, Drug, and Cosmetic Act.

The principal regulatory and IP issues are:

Therapeutic equivalence;
Local anesthetic strength;
Delivery to the periodontal pocket;
Formulation viscosity and temperature response;
Clinical endpoint requirements;
Orange Book patent certifications; and
Any later formulation or manufacturing patents.

The expired patent removes one historical barrier but does not establish that a proposed product is substitutable, pharmaceutically equivalent, therapeutically equivalent, or free of other third-party rights.

What is the geographic patent coverage?

US Patent 6,031,007 provides protection only in the United States. The underlying invention may have been pursued through an international or foreign priority family, but foreign counterparts must be reviewed individually.

Expiration, lapse, abandonment, and prosecution outcomes can differ by jurisdiction because of:

Different national filing dates;
Patent-term adjustment rules;
Patent-term extensions;
Maintenance-fee requirements;
Supplementary protection certificates;
Opposition or invalidity proceedings; and
National-phase prosecution outcomes.

A US freedom-to-operate conclusion cannot be extended automatically to Canada, Europe, Japan, Australia, or other markets.

Key Takeaways

US Patent 6,031,007 covers thermoreversible emulsion or microemulsion formulations containing oil-phase local anesthetic, water, and a thermogelling surfactant.
The most commercially relevant embodiment is lidocaine-prilocaine with Poloxamer 188 and Poloxamer 407.
Claims 3 and 4 cover anesthetic concentrations of 0.5% to 20% and 2% to 7%, respectively.
Claim 13 is limited to periodontal-pocket treatment for pain associated with periodontal scaling.
Claims 14 and 15 protect specific manufacturing sequences involving melting, homogenization, pH adjustment, and water addition.
Claim 17 imposes a pH relationship based on the lowest local-anesthetic pKa.
The US patent issued on February 29, 2000 and expired under its ordinary term in 2016.
The patent does not create a current US generic-entry barrier.
Biosimilar analysis is irrelevant because the product is a small-molecule local anesthetic.
Current commercial risk depends on later patents, Orange Book listings, regulatory equivalence, and non-US rights rather than this expired patent alone.

FAQs

Does US Patent 6,031,007 cover Oraqix?

It covers formulation and use features closely associated with Oraqix, including thermoreversible local-anesthetic emulsions, lidocaine-prilocaine embodiments, poloxamer surfactants, and periodontal-scaling use. The expired patent no longer provides current US exclusivity.

Can a generic use lidocaine and prilocaine in a periodontal gel?

Yes, expiration of Patent 6,031,007 removes this patent as a US blocking right. The proposed product must still satisfy FDA requirements and avoid any unexpired patent rights held by other parties.

Is Poloxamer 407 alone covered by the patent?

Claim 11 covers a poloxamer, but claim 12 specifically requires both Poloxamer 188 and Poloxamer 407. A product using only Poloxamer 407 would require claim-by-claim analysis and would not literally satisfy claim 12.

Does the patent cover injectable local-anesthetic products?

The claims are directed to emulsions or microemulsions with thermoreversible gelling behavior and, for claim 13, periodontal-pocket administration. Conventional injectable local-anesthetic solutions generally fall outside the stated claim architecture.

What is the main design-around strategy?

The clearest strategies are to use a non-emulsion vehicle, avoid a thermogelling surfactant, change the processing sequence, use a different local anesthetic system, or pursue a nonperiodontal indication. Because the patent is expired in the United States, these strategies are more relevant to historical analysis and foreign jurisdictions than to current US blocking risk.

References

U.S. Patent No. 6,031,007. (2000). Pharmaceutical composition. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2003). Oraqix (lidocaine and prilocaine) periodontal gel prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
United States Patent and Trademark Office. (2024). Patent term calculator. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions: Patent and exclusivity information. Center for Drug Evaluation and Research.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Sweden	9601421	Apr 12, 1996

PCT Information
PCT Filed	April 01, 1997	PCT Application Number:	PCT/SE97/00566
PCT Publication Date:	October 23, 1997	PCT Publication Number:	WO97/38675

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	006484	⤷ Start Trial
Austria	248584	⤷ Start Trial
Australia	2416897	⤷ Start Trial
Australia	716540	⤷ Start Trial
Brazil	9702147	⤷ Start Trial
Canada	2222676	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,031,007

Summary for Patent: 6,031,007