United States Patent 10,238,640: Claim Scope, Validity Risks, and Patent Landscape for Thixotropic Ibuprofen Liquids

U.S. Patent No. 10,238,640 protects narrowly defined thixotropic oral liquid formulations containing ibuprofen, xanthan gum, microcrystalline cellulose/carboxymethylcellulose sodium, glycerin, sorbitol, polysorbate, citrate, citric acid, edetate disodium, sodium benzoate, sucralose, flavoring, coloring, and water. Claims 1 and 2 cover fixed-ingredient formulations with chlorpheniramine or no additional antihistamine, while claim 3 covers a broader ibuprofen and diphenhydramine concentration range.

The patent’s commercial scope is formulation-specific rather than molecule-specific. It does not broadly protect ibuprofen, diphenhydramine, pseudoephedrine, chlorpheniramine, or thixotropic liquids as standalone concepts. A competing product must be assessed against every limitation of at least one claim, including the specified excipients and concentration ranges.

What does U.S. Patent 10,238,640 protect?

The patent protects thixotropic oral liquid pharmaceutical compositions. A thixotropic liquid becomes less viscous when shaken or subjected to shear and returns toward a higher resting viscosity after standing. In an oral suspension, that behavior can support dose uniformity, pourability, and physical stability.

The core formulation architecture is:

Component	Claims 1-2	Claim 3
Xanthan gum	0.2 g/100 mL	0.2 g/100 mL
Microcrystalline cellulose/carboxymethylcellulose sodium	1.5 g/100 mL	About 1.5 g/100 mL
Ibuprofen	About 2 g/100 mL	About 1-3 g/100 mL
Glycerin	About 28.8 g/100 mL	About 28.8 g/100 mL
Sorbitol solution, 70%	20 g/100 mL	About 20 g/100 mL
Polysorbate	0.3 g/100 mL	0.3 g/100 mL
Sodium citrate	About 0.55 g/100 mL	About 0.55 g/100 mL
Citric acid	About 0.75 g/100 mL	About 0.75 g/100 mL
Edetate disodium	About 0.05 g/100 mL	About 0.05 g/100 mL
Sodium benzoate	About 0.25 g/100 mL	About 0.25 g/100 mL
Sucralose	About 0.2 g/100 mL in claims 1-2	Sucralose required, amount not fixed
Additional active	Chlorpheniramine in claim 1; none in claim 2	Diphenhydramine, about 0.01-0.40 g/100 mL
Other ingredients	Flavoring, coloring, water	Flavoring, water; claim text does not expressly require coloring

The use of “consisting of” is material. It generally creates a closed claim format, limiting the claimed composition to the listed components and ingredients that do not materially alter the basic and novel characteristics of the composition. The precise effect depends on the prosecution history and judicial construction, but an accused formulation containing a materially different active ingredient or an additional functional excipient may have a substantial noninfringement argument.

How do claims 1, 2, and 3 differ?

Claim 1: ibuprofen, chlorpheniramine, and pseudoephedrine

Claim 1 is the most compositionally specific claim. It requires:

About 2 g/100 mL ibuprofen;
About 0.02 g/100 mL chlorpheniramine maleate;
About 0.3 g/100 mL pseudoephedrine;
The specified thixotropic system and preservative/buffer package;
Flavoring, coloring, and water.

This claim targets a multi-symptom cold formulation combining an analgesic, antihistamine, and decongestant. A product omitting either chlorpheniramine or pseudoephedrine would not literally satisfy claim 1.

Claim 2: ibuprofen-only formulation

Claim 2 removes chlorpheniramine and pseudoephedrine but retains the excipient system. It covers an ibuprofen liquid with the same principal rheology, vehicle, sweetener, preservative, chelating-agent, surfactant, and buffer components.

Claim 2 may be commercially important because it is not limited to a combination cold product. A pediatric or adult ibuprofen suspension using the listed concentrations could fall within its literal scope even without an antihistamine or decongestant.

Claim 3: ibuprofen and diphenhydramine

Claim 3 covers:

Ibuprofen at about 1-3 g/100 mL;
Diphenhydramine at about 0.01-0.40 g/100 mL;
The same principal xanthan gum and cellulose-based thixotropic system;
The same glycerin, sorbitol, surfactant, preservative, citrate, citric acid, and edetate disodium package.

Claim 3 is broader for ibuprofen concentration than claims 1 and 2. It is narrower in requiring diphenhydramine. The concentration range creates potential literal infringement exposure for products at common ibuprofen concentrations within the 1-3% range, assuming the other limitations are met.

What formulation technology is protected?

The patent’s principal technical contribution is the combination of two rheology modifiers:

Xanthan gum at approximately 0.2 g/100 mL; and
Microcrystalline cellulose/carboxymethylcellulose sodium at approximately 1.5 g/100 mL.

That combination is used with a high-polyol vehicle containing glycerin and 70% sorbitol solution. The formulation also includes polysorbate, which may support wetting or dispersion of ibuprofen and other hydrophobic ingredients.

The buffer and stability system includes:

Sodium citrate;
Citric acid;
Edetate disodium;
Sodium benzoate.

The formulation therefore combines rheology control, wetting or dispersion support, sweetness and mouthfeel, preservation, chelation, and pH control. The patent’s enforceable value depends on whether this complete combination produces a result that was nonobvious over earlier ibuprofen suspensions and conventional thixotropic vehicles.

How broad are the concentration limitations?

The concentration language is mixed.

Fixed or near-fixed limitations

Claims 1 and 2 recite concentrations such as:

0.2 g/100 mL xanthan gum;
1.5 g/100 mL microcrystalline cellulose/carboxymethylcellulose sodium;
28.8 g/100 mL glycerin;
0.3 g/100 mL polysorbate;
0.25 g/100 mL sodium benzoate;
0.55 g/100 mL sodium citrate;
0.75 g/100 mL citric acid;
0.05 g/100 mL edetate disodium.

The terms “about” create tolerance questions. Courts commonly interpret “about” in light of the specification, examples, analytical precision, and prosecution history. The patent does not automatically cover every formulation with a materially different concentration.

Express range limitation in claim 3

Claim 3 recites ibuprofen at about 1-3 g/100 mL and diphenhydramine at about 0.01-0.40 g/100 mL. Products outside those ranges may avoid literal infringement, although the doctrine of equivalents could remain relevant depending on the deviation and prosecution history.

The narrow excipient concentrations can make claim 3 vulnerable to design-around strategies. A manufacturer could evaluate changes to:

Xanthan gum level;
Cellulose-based suspending-agent level;
Glycerin or sorbitol concentration;
Polysorbate type or concentration;
Buffer composition;
Preservative;
Chelating agent;
Sweetener;
Antihistamine.

A design-around must be tested against all claims, equivalents, prosecution-history estoppel, and any related continuation or divisional patents.

What is the likely patent term and expiration date?

U.S. Patent No. 10,238,640 was issued on March 26, 2019. Its enforceable term is generally governed by the 20-year term from the earliest effective nonprovisional filing date, subject to patent-term adjustment, terminal disclaimers, and any patent-term extension.

The patent should not be treated as expiring solely on the issue date plus 20 years. The controlling date must be confirmed through the USPTO patent record and the patent’s continuity data. A patent-term adjustment can move the expiration date beyond the ordinary 20-year calculation.

The patent is directed to an OTC-style liquid formulation rather than a new molecular entity. Hatch-Waxman five-year NCE exclusivity is therefore not the relevant exclusivity mechanism. The commercial barrier is the patent term and any related patents, regulatory exclusivity, trade secrets, and manufacturing know-how.

Does Patent 10,238,640 have Orange Book status?

The patent’s Orange Book relevance is likely limited.

The FDA Orange Book lists patents and exclusivity associated with approved drug applications, primarily prescription products and products approved through applicable NDA or ANDA pathways. A formulation patent covering an OTC monograph product is not automatically listed merely because it covers a marketed drug.

The patent may be Orange Book-listed only if:

It is submitted for an applicable FDA-approved product;
The sponsor identifies it as a patent that claims the drug, formulation, or approved method of use;
The FDA accepts the listing under its regulatory framework.

A product-specific Orange Book assessment should distinguish:

Issue	Assessment
Active ingredient	Ibuprofen and established OTC combination actives
Likely regulatory pathway	OTC monograph or NDA, depending on product and indications
NCE exclusivity	Not expected for established actives
Formulation patent listing	Product- and application-dependent
ANDA Paragraph IV relevance	Relevant only if an approved reference product and listed patent support an ANDA challenge
OTC monograph competition	May proceed without an ANDA, depending on formulation and labeling

The patent itself does not create a regulatory exclusivity period comparable to NCE, orphan-drug, or pediatric exclusivity.

What Paragraph IV and generic-entry risks exist?

A Paragraph IV challenge would require an ANDA applicant to certify that a listed patent is invalid, unenforceable, or not infringed. The commercial relevance depends on whether the patented formulation is tied to an approved reference listed drug and whether the patent appears in the Orange Book.

Potential Paragraph IV theories include:

Noninfringement. The proposed product omits a required ingredient or uses a concentration outside the claimed range.
Indefiniteness. Terms such as “about,” “thixotropic,” “flavoring agent,” and “coloring agent” may be challenged if the specification and prosecution history do not provide objective boundaries.
Anticipation. An earlier reference may disclose the full combination, including the rheology modifiers and concentrations.
Obviousness. Separate references may disclose ibuprofen suspensions, xanthan gum, cellulose suspending systems, polyol vehicles, preservatives, and combination cold actives.
Written description or enablement. A challenger could argue that the disclosure does not support the full scope of claimed concentration tolerances or active combinations.
Patent-term defenses. Any terminal disclaimer or PTA calculation may affect the enforceable term.

A formulation patent with many mandatory components can be easier to design around than a broad composition claim. It can still create launch risk if the branded product’s exact excipient profile is copied.

Which products and competitors create the greatest infringement exposure?

The highest-risk products are liquid formulations that replicate the complete excipient system and active combinations.

Product profile	Claim exposure
Ibuprofen liquid with the listed xanthan/cellulose system and concentrations	High under claim 2
Ibuprofen plus diphenhydramine at 1-3% and 0.01-0.40%	High under claim 3
Ibuprofen plus chlorpheniramine and pseudoephedrine at the claimed levels	High under claim 1
Ibuprofen suspension using xanthan gum but no microcrystalline cellulose/carboxymethylcellulose sodium	Reduced literal exposure
Ibuprofen suspension using a different suspending system	Reduced literal exposure
Tablet, capsule, softgel, or chewable dosage form	Outside the literal oral-liquid claims
Liquid with a materially different preservative or buffer system	Potentially outside the claims
Product with ibuprofen concentration below 1% or above 3% and no equivalent argument	Potentially outside claim 3

Large OTC manufacturers, private-label suppliers, and contract manufacturers are the principal competitive actors. The relevant comparison is not limited to companies selling the same brand. A contract manufacturer using the claimed formula can create direct patent exposure even where the product is sold under a retailer or private-label brand.

How strong is the patent estate?

The strength of U.S. Patent 10,238,640 is mixed.

Strengths

The claims identify a detailed and commercially reproducible formulation.
Claim 2 reaches an ibuprofen-only liquid without requiring cold-combination actives.
Claim 3 includes useful concentration ranges for ibuprofen and diphenhydramine.
The claims may be difficult to avoid accidentally if a competitor uses the same formulation specification.

Weaknesses

The “consisting of” format limits claim coverage.
The claims require numerous excipients at narrow concentrations.
The active ingredients are old and widely used.
Thixotropic suspensions and the individual excipients were likely known before the relevant filing date.
Obviousness may be a substantial risk if prior art teaches combining xanthan gum and microcrystalline cellulose/carboxymethylcellulose sodium in oral suspensions.
The patent does not appear, from the claims supplied, to cover a broad functional result independent of composition.
The claims do not expressly recite quantitative rheological performance parameters, such as yield stress, viscosity recovery, sedimentation rate, or redispersibility threshold.

The strongest infringement case would involve a product matching the ingredient list and concentrations. The strongest validity challenge would combine prior art on ibuprofen suspensions, thixotropic rheology systems, polyol vehicles, and OTC cold formulations.

What prior-art categories are most relevant?

A freedom-to-operate and invalidity review should focus on five prior-art groups.

Ibuprofen oral suspensions

References covering pediatric ibuprofen liquids, flavored suspensions, preservatives, sweeteners, and polyol vehicles may disclose most of the formulation except the precise rheology combination.

Xanthan gum and cellulose suspending systems

Pharmaceutical formulation references commonly disclose xanthan gum, microcrystalline cellulose, and carboxymethylcellulose sodium for suspension stability and thixotropic behavior. The key question is whether a reference discloses the claimed concentrations and the complete excipient combination.

Polyol-based oral vehicles

Glycerin and sorbitol are conventional oral-liquid excipients. Their presence alone is unlikely to provide strong patentability. Their role in the claimed combination may matter if the specification shows an unexpected rheological or stability effect.

Combination cold medicines

Chlorpheniramine, pseudoephedrine, diphenhydramine, and ibuprofen have extensive preexisting use in oral pharmaceutical products. Prior-art combination products may be relevant to claims 1 and 3.

Preservation and pH control

Sodium benzoate, citrate, citric acid, and edetate disodium are conventional formulation components. Their individual inclusion is unlikely to distinguish the claims unless the patent demonstrates a specific interaction or unexpected stability result.

What geographic coverage exists?

U.S. Patent 10,238,640 provides enforceable rights only in the United States. International protection depends on related applications and granted patents in jurisdictions such as:

Canada;
Europe;
Australia;
Japan;
China;
Mexico;
Brazil.

A patent-family review should identify priority applications, PCT filings, national-stage applications, continuations, divisionals, and foreign grants. U.S. claim scope cannot be assumed to match foreign claims. European prosecution may produce narrower claims because of added-matter and inventive-step standards, while Canadian, Australian, Chinese, or Japanese claims may differ in scope and term.

The U.S. patent’s geographic risk is therefore highest for manufacture, importation, sale, offer for sale, or use of covered formulations in the United States. Manufacturing abroad does not eliminate U.S. risk if the covered product is imported or sold in the United States.

Are manufacturing processes or trade secrets separate barriers?

The supplied claims are composition claims. They do not expressly claim:

A manufacturing sequence;
A specific mixing order;
A homogenization process;
A filling process;
A particular particle-size distribution;
A viscosity measurement protocol;
A packaging configuration.

The formulation may nevertheless require process know-how to reproduce its rheological behavior consistently. The practical barriers can include:

Hydration order for xanthan gum;
Dispersion of microcrystalline cellulose/carboxymethylcellulose sodium;
Wetting of ibuprofen;
Control of shear;
pH adjustment;
Preservative distribution;
Air incorporation;
Fill-weight and dose-uniformity controls.

These manufacturing details may be protected by trade secrets even when they are absent from the patent claims. They can also affect whether an alleged copy performs as a legally equivalent formulation.

What litigation or settlement issues should be reviewed?

A complete litigation assessment requires checking:

PACER for district-court complaints and declaratory-judgment actions;
PTAB for inter partes review or post-grant review;
USPTO Patent Center for prosecution history;
FDA Orange Book listings;
FDA approved-product labeling;
SEC filings and licensing disclosures of the patent owner;
State and federal product-liability filings involving the formulation.

The supplied claim text alone does not establish that Patent 10,238,640 has been litigated, licensed, settled, challenged under Paragraph IV, or reviewed by the PTAB. No litigation or settlement conclusion should be drawn from the patent number alone.

What generic launch scenarios are most plausible?

Scenario 1: Exact formulation copy

A generic or private-label product matching the claimed concentrations and active ingredients would face the highest risk. The manufacturer would need to evaluate infringement, regulatory filing strategy, and potential patent challenge before launch.

Scenario 2: Excipient substitution

Replacing the cellulose-based thixotropic system, changing the surfactant, or using a different preservative may reduce literal infringement risk. The substitute must still satisfy FDA quality, stability, suspension, palatability, and dose-uniformity requirements.

Scenario 3: Different dosage form

A tablet, capsule, chewable, powder, or non-liquid product would generally fall outside these composition claims. Such products may face separate patents, but the supplied claims would not directly cover them.

Scenario 4: Different active combination

Removing chlorpheniramine, pseudoephedrine, or diphenhydramine may avoid claims 1 or 3. Claim 2 remains relevant to an ibuprofen-only liquid if the full excipient system is retained.

Scenario 5: Post-expiration launch

A competitor can launch the claimed formulation after expiration, subject to any unexpired continuation patents, later-issued patents, regulatory requirements, and non-patent restrictions.

Key Takeaways

U.S. Patent 10,238,640 is a narrow formulation patent, not a broad ibuprofen or cold-medicine patent.
Its central limitation is the specified xanthan gum and microcrystalline cellulose/carboxymethylcellulose sodium thixotropic system.
Claim 1 covers an ibuprofen-chlorpheniramine-pseudoephedrine liquid.
Claim 2 covers an ibuprofen-only liquid.
Claim 3 covers an ibuprofen-diphenhydramine liquid with broader ibuprofen and diphenhydramine ranges.
“Consisting of” materially narrows the claims and supports formulation-based design-arounds.
The principal validity risks are anticipation, obviousness, and indefiniteness surrounding “about” and “thixotropic.”
Orange Book and Paragraph IV relevance depends on the specific approved reference product and listing status.
A reliable expiration analysis requires the patent’s continuity, terminal-disclaimer, and patent-term-adjustment records.
No litigation, settlement, licensing, or PTAB conclusion follows from the claims alone.
The highest commercial risk is an exact or near-exact copy of the patented liquid formulation.

FAQs

Does Patent 10,238,640 cover all liquid ibuprofen products?

No. The claims require a specific excipient system, including xanthan gum, microcrystalline cellulose/carboxymethylcellulose sodium, glycerin, sorbitol, polysorbate, citrate, citric acid, edetate disodium, and sodium benzoate.

Can a company avoid the patent by changing only the flavor?

Usually not if all other claim limitations remain satisfied. Flavoring is expressly included in the claims, and changing the flavor may not remove the product from the claimed composition.

Does claim 3 cover diphenhydramine products without ibuprofen?

No. Claim 3 requires both ibuprofen and diphenhydramine within the stated concentration ranges.

Does the patent protect the word “thixotropic” by itself?

No. The claims protect compositions that satisfy the listed compositional limitations and are characterized as thixotropic. The patent does not create a monopoly over every thixotropic oral liquid.

Can an OTC product infringe the patent without an ANDA?

Yes. Patent infringement and ANDA status are separate issues. An OTC product sold under a monograph or NDA pathway can infringe a valid, enforceable patent even if Paragraph IV certification is not required.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	2567075	⤷ Start Trial
China	1988893	⤷ Start Trial
European Patent Office	1748765	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 10,238,640