US Patent 9,808,431: Guaifenesin Oral Solution Claims, Patent Scope, Expiration and Competitive Landscape

US Patent 9,808,431 protects immediate-release oral liquid formulations containing guaifenesin, water, propylene glycol and glycerol, where the formulation achieves specified guaifenesin exposure and at least four hours of therapeutically effective plasma concentration. The claims also cover combination products containing a cough suppressant, decongestant, antihistamine or analgesic.

The patent is a formulation and pharmacokinetic patent. It does not broadly claim guaifenesin, guaifenesin tablets, extended-release dosage forms, or every liquid guaifenesin product. Infringement generally requires both the claimed formulation characteristics and the required pharmacokinetic performance, subject to claim construction and proof under the applicable infringement standard.

What does US Patent 9,808,431 cover?

The patent covers two principal claim strategies:

A composition-defined formulation containing specified amounts of propylene glycol and glycerol.
A performance-defined formulation that produces materially higher guaifenesin exposure than a comparable aqueous control.

The independent claims are claims 1 and 16.

Claim group	Core limitation	Commercial significance
Claim 1	Immediate-release oral solution containing guaifenesin, an additional drug, water, and 48% to 72% total propylene glycol plus glycerol	Directly targets high-solvent liquid combination products
Claims 2-5	Narrower solvent concentration and ratio ranges	Creates fallback positions around the preferred formulation window
Claims 6-9	Higher Cmax and AUC thresholds	Covers formulations with stronger pharmacokinetic performance
Claims 10-15	Decongestant, antihistamine or analgesic species	Expands coverage across cough, cold and flu combinations
Claim 16	Both propylene glycol and glycerol, with at least 1.5-fold Cmax and/or 1.4-fold AUC versus an aqueous control	Captures formulations outside the express 48%-72% solvent range if the performance test is met
Claims 17-18	Higher comparative exposure and 48%-72% solvent range	Provides an overlapping, narrower combination
Claims 19-20	Decongestant or antihistamine	Narrows the combination-drug field

The claim set therefore combines composition, formulation architecture, comparative bioavailability and therapeutic-duration limitations.

How broad is claim 1 of US 9,808,431?

Claim 1 is broad in the identity of the accompanying drug but relatively specific in solvent composition and pharmacokinetic outcome.

The claim requires:

An immediate-release solution for oral administration.
Guaifenesin.
At least one additional drug.
The additional drug must be an antitussive, decongestant, antihistamine or analgesic.
Water as a solvent.
Propylene glycol and glycerol as additional solvents.
A combined propylene glycol and glycerol concentration of 48% to 72% by weight.
A single adult dose affording 200 mg of guaifenesin.
Cmax of at least 3,600 ng/mL and/or AUC(0-inf) of at least 3,700 ng·hr/mL.
A therapeutically effective guaifenesin plasma concentration for at least four hours.

The claim does not require a particular commercial brand, flavor, preservative, sweetener, container, measuring device or manufacturing process. It also does not specify a particular decongestant, antihistamine or analgesic in the independent claim.

That breadth is narrowed by the pharmacokinetic requirements. A liquid product with the claimed solvent percentages may still fall outside claim 1 if it cannot satisfy the specified guaifenesin exposure or duration limitations. Conversely, a product may create risk under claim 16 even if it does not fall within claim 1's 48%-72% solvent window.

What formulations are protected by claims 2 through 9?

Claims 2 through 9 establish a concentration and performance hierarchy.

Solvent concentration limits

Claim 2 narrows the total propylene glycol and glycerol concentration to 54%-66% by weight.

Claims 4 and 5 separately require:

Propylene glycol: 15%-23% by weight.
Glycerol: 33%-49% by weight.

These ranges imply an intended formulation region centered on a high glycerol content with a lower propylene glycol content. The ranges overlap with claim 2 and claim 1, but they do not independently require a particular propylene glycol-to-glycerol ratio unless claim 3 is also met.

Propylene glycol-to-glycerol ratio

Claim 3 requires a glycerol-to-propylene glycol weight ratio of 1.7:1 to 2.5:1.

The dependent concentration claims create a commercially relevant formulation window. For example, a formulation containing 20% propylene glycol and 40% glycerol has a 2:1 ratio and satisfies the principal concentration limitations, assuming the remaining claim 1 requirements are met.

Pharmacokinetic thresholds

Claims 6 and 7 raise the minimum Cmax to:

At least 3,800 ng/mL under claim 6.
At least 4,000 ng/mL under claim 7.

Claims 8 and 9 add higher AUC requirements:

Claim 8: Cmax of at least 3,800 ng/mL and AUC(0-inf) of at least 3,900 ng·hr/mL.
Claim 9: Cmax of at least 4,000 ng/mL and AUC(0-inf) of at least 4,100 ng·hr/mL.

These claims are useful fallback claims because they narrow the performance profile without changing the basic formulation concept.

What additional drugs are covered?

The patent claims combinations with broad therapeutic categories and selected named ingredients.

Category	Expressly identified examples
Antitussive	Covered as a class in claims 1 and 16; claim 15 also covers an analgesic, while the supplied claim text does not enumerate antitussive species
Decongestant	Pseudoephedrine and pharmaceutically acceptable salts; phenylephrine and pharmaceutically acceptable salts
Antihistamine	Brompheniramine, chlorcyclizine, chlorpheniramine, dexbrompheniramine, dexchlorpheniramine, diphenhydramine, doxylamine, phenindamine, pheniramine, pyrilamine, thonzylamine and triprolidine, including acceptable salts
Analgesic	Covered as a category by claims 1 and 16

The claims are drafted to cover single additional drugs and combinations of additional drugs. A guaifenesin product containing pseudoephedrine and an antihistamine can therefore present multiple independent and dependent claim pathways if the solvent and pharmacokinetic limitations are satisfied.

How does claim 16 differ from claim 1?

Claim 16 is the principal alternative infringement route.

Claim 1 uses absolute pharmacokinetic thresholds and a defined solvent concentration range. Claim 16 uses a comparative bioavailability test. The claimed product must contain water, propylene glycol and glycerol and must produce:

A Cmax at least 1.5 times that of a specified aqueous control and/or
An AUC(0-inf) at least 1.4 times that of the aqueous control; and
A therapeutically effective guaifenesin plasma concentration for at least four hours.

Claim 17 raises the comparative thresholds to:

At least 1.6-fold Cmax; and
At least 1.5-fold AUC.

Claim 18 adds the 48%-72% total solvent range.

The aqueous comparator is important. It must contain the same concentrations of guaifenesin and the relevant additional drug, but without propylene glycol and glycerol. Product testing would need to control for dose, concentration, administration conditions, subject population and analytical methodology. A dispute over the correct comparator could materially affect infringement and validity.

When does US Patent 9,808,431 lose exclusivity?

US Patent 9,808,431 issued on November 7, 2017. Its term is generally governed by the 20-year period measured from the applicable earliest nonprovisional US filing date, subject to patent-term adjustment, terminal disclaimers and any applicable statutory extension recorded in the patent file.[1]

The patent is therefore expected to provide protection into the early 2030s, subject to the official USPTO Patent Center term calculation. The issue date alone does not determine the expiration date. A precise freedom-to-operate analysis should use the patent's bibliographic record, continuity data, patent-term-adjustment calculation and any terminal disclaimer.

The patent's practical exclusivity may end earlier than the statutory expiration date if:

The patent expires for failure to pay maintenance fees.
All commercially relevant claims are invalidated or narrowed.
A marketed product does not satisfy the pharmacokinetic limitations.
A competitor designs around the solvent system or therapeutic-performance limitations.
Regulatory exclusivity expires before patent protection.

What is the Orange Book status of US 9,808,431?

US Patent 9,808,431 is a formulation patent covering an oral guaifenesin solution. Orange Book relevance depends on whether the patent is submitted for a qualifying approved NDA product and whether FDA accepts the patent as an NDA patent under applicable listing rules.[2]

Guaifenesin is widely marketed in over-the-counter products under FDA's OTC monograph framework. A patent covering an OTC formulation does not automatically create an Orange Book-listed patent or an ANDA Paragraph IV dispute. The Orange Book is principally relevant to approved prescription and certain approved nonprescription NDA products, not to every OTC formulation patent.[2]

The regulatory risk should therefore be separated into two questions:

Whether the patent is enforceable against a commercial product.
Whether the patent is listed for an FDA-approved reference product and can trigger statutory ANDA certification consequences.

A patent can create formulation litigation risk without appearing as an Orange Book-listed patent.

Are Paragraph IV challenges likely?

A Paragraph IV challenge is relevant only if the patent is listed in the Orange Book against an NDA reference product and an ANDA applicant seeks approval for a product covered by the listed claims.[2]

For this patent, the main technical bases for a Paragraph IV position would include:

The proposed product does not contain both propylene glycol and glycerol.
The combined solvent concentration is below 48% or above 72%.
The glycerol-to-propylene glycol ratio falls outside 1.7:1 to 2.5:1.
The product lacks a qualifying additional drug.
The product does not provide the claimed Cmax or AUC.
The product does not maintain the required therapeutic concentration for at least four hours.
The proposed dosage form is not an immediate-release solution.
The asserted claims are anticipated or rendered obvious by prior art liquid guaifenesin formulations.

A generic applicant could also pursue a formulation design that avoids the comparative-performance limitations in claim 16. Because claim 16 is performance-based, laboratory and clinical pharmacokinetic data would be central to any dispute.

What patent litigation affects US Patent 9,808,431?

The claim text alone does not establish a current litigation record. The principal litigation question is whether the patent has been asserted against a specific manufacturer, ANDA applicant or OTC competitor.

For diligence purposes, the relevant litigation searches include:

USPTO Patent Center for prosecution history, ownership and continuity.
PACER and district court docket systems for infringement complaints.
PTAB records for inter partes review, post-grant review or covered business-related proceedings.
FDA Orange Book records for patent listing and NDA association.
FDA ANDA litigation records where available.

The technical disputes would likely focus on claim construction for "immediate release," "solution," "therapeutically effective plasma concentration," "single dose," and the identity of the aqueous comparator. The pharmacokinetic limitations may also create proof issues because infringement cannot be determined solely from the ingredient list in every case.

How strong is the patent estate for guaifenesin liquid products?

The estate is strongest against products that reproduce the claimed formulation architecture:

Guaifenesin in an immediate-release oral liquid.
Water, glycerol and propylene glycol.
Total glycerol plus propylene glycol near 48%-72%.
A common cough, cold, allergy or analgesic ingredient.
Pharmacokinetic exposure materially above a water-only formulation.

The estate is weaker against:

Guaifenesin-only liquids, because the independent claims require an additional drug.
Products using glycerol without propylene glycol.
Products using propylene glycol without glycerol.
Syrups with lower solvent concentrations.
Solid immediate-release or extended-release products.
Products with insufficient guaifenesin exposure.
Products where four-hour therapeutic concentration cannot be established.
Formulations using alternative cosolvents, provided the resulting product does not otherwise meet the claim limitations.

The patent has meaningful claim redundancy. Claims 1 and 16 use different infringement theories, while claims 2-9 and 17-18 provide narrower fallback positions. Its vulnerability is that many key limitations are measurable and potentially predictable from formulation and pharmacokinetic testing.

What generic launch risks exist?

A generic or private-label launch would face three separate risk layers.

Formulation risk

The manufacturer should identify whether the proposed product contains both solvents and falls within the claimed ranges. A formulation outside the express percentage ranges may still require testing under claim 16.

Pharmacokinetic risk

A product may avoid claim 1 if its Cmax is below 3,600 ng/mL and its AUC is below 3,700 ng·hr/mL. It may still face claim 16 if its exposure is at least 1.5 times the aqueous comparator or its AUC is at least 1.4 times that comparator.

Regulatory risk

If the patent is tied to an NDA and listed in the Orange Book, an ANDA applicant may need a Paragraph III or Paragraph IV certification, depending on the patent term and proposed labeling. If the product is marketed under the OTC monograph pathway, the applicant may not receive the same Orange Book-driven pathway, but patent infringement exposure remains possible.

What manufacturing and intellectual-property barriers matter?

The patent does not principally claim a manufacturing process. Its manufacturing relevance arises from the need to reliably produce a homogeneous, stable, palatable solution with high concentrations of glycerol and propylene glycol.

Commercial development barriers include:

Solubility and precipitation control.
Viscosity and pourability.
Taste masking.
Compatibility with preservatives, flavors and dyes.
Container and closure compatibility.
Dose uniformity.
Stability over the labeled shelf life.
Reproducibility of the claimed pharmacokinetic profile.

A competitor may design around the patent through a different cosolvent system, a solid dosage form, a modified-release product or a liquid formulation that does not meet the claimed exposure thresholds. Such design-around strategies require separate analysis of other guaifenesin formulation patents and applicable FDA requirements.

How does this patent compare with older guaifenesin patents?

Older guaifenesin patents generally focused on the active ingredient, dosage form, sustained release, tablet architecture or broad pharmaceutical composition concepts. US 9,808,431 is narrower in dosage form but more sophisticated in its use of pharmacokinetic endpoints.

Patent characteristic	US 9,808,431	Typical older guaifenesin patent
Dosage form	Immediate-release oral solution	Often tablet, capsule or extended-release dosage form
Active ingredient	Guaifenesin plus specified drug class	Guaifenesin alone or in broader combinations
Formulation focus	Glycerol and propylene glycol solvent system	Release matrix, coating or general composition
Performance limitation	Cmax, AUC and four-hour concentration	Often absent or less central
Design-around path	Change solvents, concentrations or exposure profile	Change release mechanism or dosage form
Regulatory overlap	Potential OTC and NDA formulation issues	Often tied to approved extended-release products

The patent should therefore be analyzed as part of a layered estate rather than as a substitute for an Orange Book or freedom-to-operate review covering all guaifenesin products.

Key Takeaways

US Patent 9,808,431 targets immediate-release guaifenesin oral solutions containing both propylene glycol and glycerol.
Claim 1 requires 48%-72% combined propylene glycol and glycerol, specified guaifenesin exposure and at least four hours of therapeutic concentration.
Claims 2-9 narrow the solvent ranges, solvent ratio and pharmacokinetic thresholds.
Claim 16 creates a separate comparative-bioavailability pathway based on an aqueous control.
Combination products with pseudoephedrine, phenylephrine, antihistamines, antitussives or analgesics fall within the intended commercial field.
The patent does not broadly cover guaifenesin tablets, capsules, extended-release products or guaifenesin-only liquids.
Orange Book listing and Paragraph IV consequences depend on association with a qualifying FDA-approved NDA product.
The expected patent term extends into the early 2030s, subject to the official USPTO term calculation and any terminal disclaimer or adjustment.
The principal design-around routes are omission of one solvent, use of alternative solvents, lower solvent concentration, a different dosage form or failure to meet the claimed pharmacokinetic thresholds.
The principal litigation issues are likely to involve immediate-release status, solution construction, comparator methodology, pharmacokinetic testing and the meaning of "therapeutically effective plasma concentration."

FAQs

Does US 9,808,431 cover Mucinex liquid products?

It may cover a Mucinex or competing guaifenesin liquid only if the product satisfies the claimed solvent, combination-drug, dosage-form and pharmacokinetic limitations. Brand identity alone does not establish infringement.

Can a guaifenesin liquid avoid the patent by replacing glycerol with sorbitol?

Replacing glycerol may avoid the express requirement for both propylene glycol and glycerol in claims 1 and 16. The complete formulation and all asserted claims must still be analyzed for literal or equivalent infringement.

Does the patent cover phenylephrine-guaifenesin liquid combinations?

Yes, claim 12 expressly identifies phenylephrine and its pharmaceutically acceptable salts as a covered decongestant, provided the remaining limitations of the applicable independent claim are met.

Is a four-hour therapeutic concentration the same as an extended-release claim?

No. The patent claims an immediate-release solution with a specified plasma concentration duration. The four-hour pharmacokinetic limitation does not by itself convert the product into an extended-release dosage form.

Can an ANDA applicant challenge the patent without a Paragraph IV certification?

Only if the patent is not an applicable listed patent for the relevant reference product or the statutory certification framework does not apply. If the patent is listed against an NDA product, the ANDA strategy must account for the applicable Hatch-Waxman certification requirements.

References

United States Patent and Trademark Office. (2017). U.S. Patent No. 9,808,431, pharmaceutical compositions comprising guaifenesin. USPTO Patent Center.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. FDA.
U.S. Food and Drug Administration. (2024). Electronic Orange Book. FDA.
U.S. Food and Drug Administration. (2024). Over-the-counter monograph drugs. FDA.
U.S. Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, patent term and patent term adjustment provisions. USPTO.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Sovereign Pharms	OBREDON	guaifenesin; hydrocodone bitartrate	SOLUTION;ORAL	205474-001	Nov 14, 2014		DISCN	Yes	No	9,808,431	⤷ Start Trial	Y	Y		A METHOD OF INCREASING THE BIOAVAILABILITY OF GUAIFENESIN IN A SOLUTION CONTAINING 54% TO 66% BY WEIGHT OF PROPYLENE GLYCOL AND GLYCEROL, WHEREIN THE METHOD INCREASES THE CMAX BY AT LEAST 1.5 AND/OR INCREASES THE AUC (0-INF) BY AT LEAST 1.4	⤷ 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: 9,808,431

Which drugs does patent 9,808,431 protect, and when does it expire?

Summary for Patent: 9,808,431