United States Patent 11,612,566 (Lamotrigine Oral Liquid Suspension): Scope, Claim Architecture, and U.S. Patent Landscape

What is the core invention in US 11,612,566?

US 11,612,566 claims a method of treating neurological and/or mental disorders by administering a specific lamotrigine oral liquid suspension defined by (1) drug identity and potency, (2) a defined, multi-component formulation, and (3) multiple functional product attributes (particle size, viscosity, pH, specific gravity, microbial control, dissolution performance, and PK).

The claims are not directed to a new molecular entity. The invention scope is the dose-formulation-manufacturing performance package for lamotrigine, with downstream method claims that tie the package to treating epilepsy and bipolar disorder and to specific adjunctive and conversion scenarios.

What do the independent claim and dependent claims cover?

Claim 1: Product-defined administration method

Claim 1 requires:

Method: treating at least one of a neurological disorder and a mental disorder.
Population: “a subject suffering from the disorder.”
Dosage form: administering 0.1 to 25.0 mL of an oral liquid suspension comprising:
- Lamotrigine (3,5-diamino-6-(2,3-dichlorophenyl)-as-triazine) at 10 ± 1 mg/mL
- Excipients: water, glycerin, propylene glycol, polyethylene glycol, methylparaben, sodium benzoate, sorbitol, saccharin, sucralose, xanthan gum, carboxymethyl cellulose, sodium phosphate, microcrystalline cellulose, colloidal silicon dioxide
The claim uses a formulation-with-range strategy (composition and concentration anchored to 10 mg/mL; excipient list fixed; administration volume limited).

Dependent claims: disease framing

Claim 2: neurological disorder comprises epilepsy.
Claim 3: mental disorder comprises bipolar disorder.
Claim 4: specifies clinical use cases:
- Epilepsy (age 2+) as adjunctive therapy for:
  - partial-onset seizures
  - primary generalized tonic-clonic seizures
  - generalized seizures of Lennox-Gastaut syndrome
- Epilepsy (age 16+) conversion to monotherapy for partial-onset seizures in patients receiving one of:
  - carbamazepine
  - phenytoin
  - phenobarbital
  - primidone
  - valproate
- Bipolar disorder: delaying time to occurrence of mood episodes in acute mood episode patients treated with standard therapy

Dependent claims: particle size distribution (PSD)

Two alternative PSD-dependent limitations appear:

Claim 5: D90 ≤ 200 µm, D50 ≤ 100 µm, D10 ≤ 30 µm
Claim 6: D90 ≤ 140 µm, D50 ≤ 63 µm, D10 ≤ 26 µm

These claims create capture thresholds for formulation milling/particle engineering. A design-around must either move outside these PSD limits or change the formulation architecture such that lamotrigine is not within the defined PSD.

Dependent claims: physical performance

Viscosity
- Claim 7: 100–200 mPa·s at 25°C
- Claim 8: 117.5 ± 10 mPa·s at 25°C
pH
- Claim 9: 6.5–8.0
- Claim 10: 7.1–7.2
Specific gravity
- Claim 11: ≤ 1.2
- Claim 12: ≤ 1.03

These limitations are product-property defined. Changing formulation concentrations, polymer grade/level (e.g., xanthan gum vs CMC), or buffering system is a direct route to potential non-infringement, but only if it avoids the claim windows.

Dependent claims: optional sensory agents

Claim 13: optional flavoring agent
Claim 14: cherry flavor
Claim 15: optional coloring agent
Claim 16: FD&C Red #40 and FD&C Yellow #6

Dependent claims: explicit quantitative formulation example

Claim 17 recites a specific composition (w/v) with stated ranges/uncertainties, including:
- Lamotrigine 1 ± 0.1% w/v (interprets as 10 mg/mL in claim 1 context)
- Water 84.75 ± 8.5%
- Glycerin 3.25 ± 0.33%
- Propylene glycol 2.25 ± 0.23%
- PEG 400 3.00 ± 0.3%
- Methylparaben 0.1 ± 0.01%
- Sodium benzoate 0.03 ± 0.003%
- Sorbitol (70% solution) 3.0 ± 0.3%
- Saccharin sodium dihydrate 0.08 ± 0.008%
- Sucralose 0.75 ± 0.08%
- Xanthan gum 0.20 ± 0.02%
- Sodium CMC (medium viscosity; 2% aqueous solution at 25°C 400–800 cPs) 0.10 ± 0.01%
- Sodium phosphate dibasic (dried) 0.03 ± 0.01%
- Microcrystalline cellulose + colloidal silicon dioxide 1.26 ± 0.15%
- Cherry flavor 0.2 ± 0.02%
- FD&C Red #40 0.002 ± 0.0002%
- FD&C Yellow #6 0.0002 ± 0.00002%

This is the formulation “anchor” claim set used by freedom-to-operate (FTO) teams to test similarity in the most detail.

Dependent claims: dosage volume and delivered dose

Claim 18: oral liquid suspension volume in container: 0.2 mL, 0.5 mL, 2.5 mL, 10 mL, 15 mL, 20 mL
Claim 24: delivered lamotrigine doses:
- 2 ± 0.2 mg in 0.2 mL
- 5 ± 0.5 mg in 0.5 mL
- 25 ± 2.5 mg in 2.5 mL
- 100 ± 10 mg in 10 mL
- 150 ± 15 mg in 15 mL
- 200 ± 20 mg in 20 mL

Dependent claims: microbial and shelf-type constraints

Claim 19: essentially free from microbial growth for at least 24 months under ambient conditions
Claim 20: essentially free from E. coli for at least 24 months under ambient conditions
Claim 21: essentially free from Burkholderia cepacia complex (BCC) for at least 24 months under ambient conditions

These claims read like preservation and microbiological stability controls. A product that meets label shelf-life but does not match these “essentially free” conditions may attempt to position outside these dependent limitations.

Dependent claims: immediate release and dissolution

Claim 22: immediate release dosage form
Claim 23: dissolution performance:
- >85% drug release within 15 minutes
- dissolution vessel: 900 mL
- 0.1N HCl, pH 1.2
- 37 ± 0.5°C
- stirred 50 rpm
- USP Type II (paddle) apparatus

Dependent claims: PK profile

Claim 25: fasted healthy adult single-dose and multiple-dose PK characteristics:
- AUC 0–24: 142 (micrograms per hour per ml)
- Cmax (steady state): 7.93 (micrograms per ml)
- Tmax: 2.79 h
- t1/2 (single): 32.8 h
- t1/2 (multiple): 25.4 h

This is a strong linkage to product performance and is often difficult to “equivalence” around without reformulation and re-testing.

Dependent claims: adverse reaction profile

Claim 26: lower incidence, severity, and/or duration of adverse reactions vs oral tablets or chewable dispersible tablets containing equivalent lamotrigine, including dizziness, headache, diplopia, ataxia, nausea, blurred vision, somnolence, rhinitis, pharyngitis, rash, vomiting, infection, fever, accidental injury, diarrhea, abdominal pain, tremor, backpain, fatigue, xerostomia.

This is comparatively broad in symptom set but is still limited to the method context and the oral liquid suspension administration.

How does the claim set structure translate into infringement risk?

The practical infringement surface is the intersection of:

Administration method (treating epilepsy/bipolar disorder via lamotrigine oral liquid suspension)
Formulation constraints (lamotrigine concentration at 10 ± 1 mg/mL; excipient list)
Product-property constraints (PSD, viscosity, pH, specific gravity)
Performance constraints (dissolution threshold; PK profile)
Stability microbiology constraints (24-month “essentially free” for microbial growth, E. coli, and BCC)

Claim dependency creates a tiered barrier

Claim 1 sets a baseline that captures any oral liquid suspension meeting the excipient list and lamotrigine concentration range, even without PSD/viscosity/dissolution limitations (unless argued otherwise during claim construction).
Dependent claims narrow further with measurable properties. A challenger can still look for a route that avoids Claim 1 by changing only the formulation definition (concentration/excipients) or avoids dependent claims by staying inside claim 1 but failing PSD/viscosity/pH/specific gravity/dissolution/PK thresholds.

What is the effective “technical template” of the accused product?

Core formulation template (from Claim 1 + Claim 17)

Parameter	Claimed constraint
Lamotrigine concentration	10 ± 1 mg/mL
Excipients list	water, glycerin, propylene glycol, PEG, methylparaben, sodium benzoate, sorbitol, saccharin, sucralose, xanthan gum, CMC, sodium phosphate, microcrystalline cellulose, colloidal silicon dioxide
Optional	cherry flavor; FD&C Red #40 + FD&C Yellow #6
Specific quantitative template	Claim 17 provides w/v ranges and medium-viscosity CMC grade

Product attribute template

Attribute	Claimed limits
PSD	D90 ≤ 200 µm; D50 ≤ 100 µm; D10 ≤ 30 µm (Claim 5) OR tighter: D90 ≤ 140 µm; D50 ≤ 63 µm; D10 ≤ 26 µm (Claim 6)
Viscosity @ 25°C	100–200 mPa·s (Claim 7) OR 117.5 ± 10 mPa·s (Claim 8)
pH	6.5–8.0 (Claim 9) OR 7.1–7.2 (Claim 10)
Specific gravity	≤ 1.2 (Claim 11) OR ≤ 1.03 (Claim 12)
Dissolution	>85% in 15 minutes in 900 mL 0.1N HCl pH 1.2 at 37 ± 0.5°C, 50 rpm USP II (Claim 23)
PK (fasted healthy adult)	AUC 0–24 = 142; Cmax(ss) = 7.93; Tmax = 2.79 h; t1/2 single = 32.8 h; t1/2 multiple = 25.4 h (Claim 25)
Microbiology/shelf	essentially free from microbial growth/E. coli/BCC for ≥24 months ambient (Claims 19–21)

How broad is the therapeutic scope?

Therapeutic coverage is defined by:

Indications: epilepsy (adjunctive and conversion to monotherapy) and bipolar disorder (delay time to occurrence of mood episodes)
Age gates:
- epilepsy 2+ for adjunctive therapy
- epilepsy 16+ for conversion to monotherapy
Adjunctive therapy comparator set: conversion to monotherapy in patients on carbamazepine, phenytoin, phenobarbital, primidone, or valproate.

This matters because method patents often include a carve-out argument if the product is used outside the claimed regimen. Claim 4 is narrower than claims 1–3, which remain general to “neurological disorder and mental disorder” (but still require the product definition of Claim 1).

What is the U.S. patent landscape implication?

The patent is a formulation-defined method of use patent for lamotrigine oral liquid suspension. The U.S. landscape for lamotrigine is therefore likely segmented into:

Drug substance and early composition families (expired or near-expired)
Specific oral dosage form formulation and performance families (likely where enforceability sits)
Use and formulation performance claims (dissolution/PK/PSD/viscosity/pH and microbial stability)
Regulatory exclusivities that typically govern immediate generic entry for an NDA/505(b)(2), while patents govern launch and design-around choices.

Given the claim structure of US 11,612,566, the most relevant competitive threat is not “different lamotrigine” but different formulation performance. If an ANDA or 505(j) product uses a lamotrigine oral liquid suspension with different PSD, viscosity, pH, specific gravity, dissolution behavior, or microbial control, it can attempt to avoid dependent claim constraints and potentially avoid Claim 1 if formulation composition deviates.

Where are the main design-around levers?

1) Lamotrigine concentration

Claim 1 requires 10 ± 1 mg/mL. Moving outside this window changes infringement posture at the independent-claim level.

2) Excipients list

Claim 1 fixes the excipient set. Removing an element or substituting a different class/material can avoid Claim 1.

3) PSD

Claims 5 and 6 establish tight D10/D50/D90 windows. A competitor can target particle engineering to exceed one threshold while maintaining acceptable oral behavior.

4) Viscosity, pH, and specific gravity

Claims 7–12 create multiple windows. Even if PSD is met, altering polymer hydration, buffering, or suspension solids density can move the product outside one or more constraints.

5) Dissolution and PK

Claims 23 and 25 impose performance conditions. Even if composition matches, the competitor must match dissolution release and the specific PK profile in the claimed test context.

6) Microbiology and shelf constraints

Claims 19–21 impose “essentially free” conditions for microbiology over 24 months ambient conditions. This is an enforceable target if the product challenges stability.

7) Labeling/use regimen

If a competitor product is used in a different dosing regimen outside adjunctive or conversion definitions, Claim 4 narrows. But Claims 1–3 remain broader method coverage as long as the product is used to treat epilepsy and/or bipolar disorder.

Key Takeaways

US 11,612,566 is a method-of-treatment patent where the method is defined by a lamotrigine oral liquid suspension with fixed excipient categories and concentration at 10 ± 1 mg/mL.
The infringement surface is dominated by measurable product attributes: PSD, viscosity, pH, specific gravity, plus functional performance: immediate release dissolution >85% in 15 minutes and a specified PK profile.
Dependent claims narrow to specific epilepsy and bipolar disorder regimens with age gates and comparator sets (carbamazepine, phenytoin, phenobarbital, primidone, valproate).
The strongest practical design-around levers are moving outside Claim 1 formulation definition or, failing that, moving outside PSD/physicochemical/performance windows and/or the 24-month microbiological criteria.

FAQs

1) Does US 11,612,566 cover lamotrigine tablets or capsules?
No. It is limited to a lamotrigine oral liquid suspension administered in specified volumes and concentration (Claim 1), with optional flavor/color features.

2) What are the tightest technical constraints in the claims?
The most specific constraints are the PSD thresholds (Claims 5 and 6), the dissolution requirement (>85% in 15 minutes under USP II in 0.1N HCl), and the fasted PK profile values (Claim 25).

3) Can a generic avoid the patent by targeting different dissolution behavior?
If Claim 23 is asserted, moving outside the >85% in 15 minutes condition can avoid that dependent limitation. However, the product may still face independent-claim exposure under Claim 1 if formulation/excipient definition matches.

4) Does the patent require a specific patient age?
Age gates appear in Claim 4 for specific epilepsy regimens (2+ adjunctive; 16+ conversion to monotherapy). Claims 1–3 are not age-limited.

5) What is the commercial relevance of the microbiology claims?
Claims 19–21 tie the suspension’s shelf life to being “essentially free” from microbial growth, E. coli, and BCC for at least 24 months under ambient conditions, which impacts formulation and preservative system strategy.

References

[1] United States Patent No. 11,612,566. (Claims as provided in user prompt).

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Owp Pharms	SUBVENITE	lamotrigine	SUSPENSION;ORAL	218879-001	Sep 16, 2025		RX	Yes	Yes	11,612,566	⤷ Start Trial				ADJUNCTIVE THERAPY FOR PARTIAL-ONSET, PRIMARY GENERALIZED TONIC-CLONIC (PGTC), OR LENNOX-GASTAUT SEIZURES IN PATIENTS 2 YEARS AND OLDER	⤷ Start Trial
Owp Pharms	SUBVENITE	lamotrigine	SUSPENSION;ORAL	218879-001	Sep 16, 2025		RX	Yes	Yes	11,612,566	⤷ Start Trial				MAINTENANCE TREATMENT OF BIPOLAR I DISORDER TO DELAY MOOD EPISODES	⤷ Start Trial
Owp Pharms	SUBVENITE	lamotrigine	SUSPENSION;ORAL	218879-001	Sep 16, 2025		RX	Yes	Yes	11,612,566	⤷ Start Trial				CONVERSION TO MONOTHERAPY FOR PARTIAL-ONSET SEIZURES IN PATIENTS 16 YEARS AND OLDER	⤷ 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: 11,612,566

Which drugs does patent 11,612,566 protect, and when does it expire?

Summary for Patent: 11,612,566