United States Patent 8,062,667: Scope, Claim Architecture, and Patent-Landscape Implications
US Patent 8,062,667 claims an aqueous, orally ingestible suspension in which a drug-ion exchange resin complex is embedded in a particulate matrix and then overcoated with a cured, water-permeable diffusion barrier. The barrier is a polyvinyl acetate (PVA, “polyvinylacetate” in the claims)-based coating applied from an aqueous dispersion and cured to provide a modified release profile. Claim scope is defined through (1) drug-ion exchange resin chemistry, (2) particle size and composition ranges, and (3) barrier coating composition, cure performance, and weight-gain mechanics.
What is the core claimed dosage form? (composition + structural layers)
Claim 1 (independent) is a three-part particulate system
Claim 1 recites an aqueous suspension containing particles made of:
-
Particulate matrix (layer 1 bulk)
- A particulate matrix comprising:
- a particulate drug-ion exchange resin complex, plus
- a water insoluble polymer/copolymer or hydrophilic polymer
- The particulate matrix is capable of passing through a #40 mesh screen.
- The drug-ion exchange resin complex is:
- a pharmaceutically acceptable drug bound to
- a pharmaceutically acceptable water insoluble ion exchange resin
- Ion exchange resin is restricted to:
- (A) a sulfonated copolymer of styrene/divinylbenzene, or
- (B) a styrene/divinylbenzene copolymer with quaternary ammonium functional groups.
- The water insoluble polymer/copolymer or hydrophilic polymer is present at about 3% to about 30% by weight, based on the weight of the drug-ion exchange resin complex.
-
Cured diffusion barrier coating (layer 2 coating)
- A cured, high tensile strength, water permeable, water insoluble, non-ionic polymeric diffusion barrier coating over the particulate matrix described above.
- Coating is:
- applied as an aqueous dispersion
- comprising:
- polyvinylacetate
- a stabilizer
- at least an amount of plasticizer effective to enhance tensile strength
- The cured barrier coating provides a modified release profile of the drug.
-
Suspension vehicle (layer 3 external)
- A pharmaceutically acceptable aqueous suspension base in which the coated particulate system is suspended.
Product-level summary
The invention is not just “ion exchange resins in a suspension.” It is a specific particulate architecture:
- drug-resin complex particle
- blended with a defined polymer matrix in a defined weight ratio
- then coated with a cured PVA-based diffusion barrier that is non-ionic, water permeable, and made from an aqueous dispersion with plasticizer and stabilizer.
What does the claim language lock down on resin chemistry?
Claim 1 narrows the ion exchange resin to two explicit classes:
- Sulfonated styrene/divinylbenzene copolymer resin (acidic/sulfonated type)
- Styrene/divinylbenzene with quaternary ammonium functional groups resin (basic type)
This is important because many ion exchange resins exist (carboxylated, acrylic backbones, different functional groups). Claim 1 limits functional group chemistry through the explicit examples.
Independent claim scope thus turns on whether the resin is one of these two (or a resin that reads as those classes).
What does the claim language lock down on particle size and polymer loading?
Particle size
- Particles must be able to pass a #40 mesh screen (Claim 1).
Polymer matrix loading
- 3% to 30% by weight water insoluble polymer/copolymer or hydrophilic polymer, based on weight of the drug-ion exchange resin complex (Claim 1).
- Dependent claims add tighter bands:
- 5% to 20% (Claim 2)
- 10% to 15% (Claim 41)
Barrier coating weight mechanics
Claim 49–50 and Claim 24–27 establish coating/buildup ranges via weight gain and resin fraction inside the coating system.
- Coating includes defined mass fractions and yields weight gain to the complex:
- about 25% to about 50% w/w weight gain (Claim 49)
- about 30% to about 45% w/w weight gain (Claim 50)
- Barrier coating composition is tied to complex weight fraction:
- 5% to 200% by weight of particulate drug-ion exchange resin complex within the coating definition (Claim 24)
- 35% to 50% (Claim 25)
- 30% to 45% (Claim 26)
- 50% (Claim 27)
Landscape implication: This ties the claim to particulate process outcomes (e.g., coating deposition level and resulting mass ratios), not just “presence of PVA.”
What does the claim language lock down on the diffusion barrier coating?
Coating material system
The diffusion barrier coating is defined as:
- polyvinylacetate (PVA “polyvinyl acetate”)
- stabilizer
- plasticizer to enhance tensile strength
- coating applied from aqueous dispersion
- must be cured into a coating with high tensile strength that is
- water permeable
- water insoluble
- non-ionic
Plasticizer
- Dependent claim 21: about 5% to about 10% w/w of solids in cured barrier coating
- Dependent claim 22: plasticizer is triacetin
Stabilizer
- Dependent claims define stabilizer as polyvinylpyrrolidone (PVP):
- Claim 15: “stabilizer comprising polyvinylpyrrolidone” with PVA and stabilizer weight ratio 10:1
- Claim 46: stabilizer in about 5% to about 10% w/w of the cured barrier coating layer
- Claim 54: hydrophilic polymer is PVP (in the particulate matrix)
Cure performance (texture analyzer)
- Claim 3: barrier coating has elongation factor 125% to 400% measured by texture analyzer.
High PVA fraction
- Claim 43: cured barrier layer comprises at least about 75% w/w polyvinylacetate
- Claim 44: 75% to 90% w/w
- Claim 45: plasticizer 2.5% to 20% w/w (based on weight of cured barrier)
These dependent claims create a relatively tight composition window if a competitor’s PVA content is materially different or if tensile and elongation properties are outside the claimed texture-analyzer band.
What is claimed about the suspension base and optional surfactants?
Claim 1 includes only “pharmaceutically acceptable aqueous suspension base.”
Dependent claims introduce dispersion surfactant specifics:
- Claim 38: aqueous dispersion further comprises an effective amount of surfactant
- Claim 17: stabilizer uses PVP with surfactant
- Claim 18: detailed example formulation includes sodium lauryl sulfate (SLS):
- matrix prepared by mixing resin complex with aqueous dispersion containing:
- PVA
- PVP
- SLS
- then drying and milling through 40 mesh
- dispersion contains 30% w/w solids
- amounts within dispersion:
- PVA 27% w/w
- PVP 2.7% w/w
- SLS 0.3% w/w
Claim 23: cured barrier coating further comprises a surfactant comprising sodium lauryl sulfate.
Landscape implication: Many suspension formulations include surfactants; these claims are meaningful when they require the barrier coating (or dispersion) to include specific surfactant identities and when the formulation history aligns with the described preparation.
What drugs fall within the scope? (broad genus + specific exemplars)
Independent claim coverage
Claim 1 lists “pharmaceutically acceptable drug” with resin-bound complex. The drug set is not limited on its face in the independent claim.
Dependent claim 28: explicit drug genus list
Claim 28 enumerates many drug candidates bound to the resin in the particulate matrix, including:
- methylphenidate/dexmethylphenidate
- dexchlorpheniramine, chlorpheniramine
- fexofenadine, diphenhydramine, carbemazepine
- morphine, oxycodone, oxymorphone, hydrocodone
- pseudoephedrine, phenylephrine
- venlafaxine
- ibuprofen, naproxen, diclofenac
- paroxetine, venlafaxine
- amoxicillin
- plus additional agents in the listed group
(Claim 28)
Dependent claims 29–36: specific drug callouts
- hydrocodone (Claim 29)
- clonidine (Claim 30)
- pseudoephedrine (Claim 31)
- diphenhydramine (Claim 34)
- ibuprofen (Claim 35)
- morphine (Claim 36)
Dependent claims 32–33: methylphenidate/dexmethylphenidate and carbinoxamine
- methylphenidate and dexmethylphenidate (Claim 32)
- carbinoxamine (Claim 33)
Claim 37: dextromethorphan-specific independent-like recitation
Claim 37 recasts the system with:
- a dextromethorphan-ion exchange resin complex,
- sulfonated styrene/divinylbenzene resin,
- particulate size passable through 40 mesh,
- matrix polymer loading 5% to 20%,
- cured barrier coating details with:
- PVA
- PVP stabilizer in 10:1 weight ratio
- plasticizer 5% to 10% of dry barrier coating
- plus both coated and uncoated particulate complexes suspended in the aqueous base.
This claim is effectively a more concrete “exemplar” claim that would be easier to map in an infringement or design-around.
Landscape implication
The drug list suggests broad formulation coverage where the novelty lies in:
- resin-bound complex particulate
- polymer-matrix blending
- cured PVA diffusion barrier with plasticized, stabilized, non-ionic properties
rather than in a single drug entity.
What are the key scope-expanding or scope-reducing claim features?
Scope-expanding elements
- Broad ion exchange resin classes (sulfonated styrene/divinylbenzene; quaternary ammonium styrene/divinylbenzene).
- Broad drug genus (via Claim 28 list plus “pharmaceutically acceptable drug” in Claim 1).
- Broad polymer matrix loading band (3% to 30% by weight in Claim 1; 5% to 20% in Claim 2).
- Broad coating composition windows via multiple dependent claims (plasticizer and weight ranges; PVA fraction and coating weight gain ranges).
Scope-reducing elements
- Coating must be:
- cured
- water permeable
- water insoluble
- non-ionic polymeric diffusion barrier
- Must contain:
- polyvinylacetate
- stabilizer
- plasticizer
- Must satisfy:
- texture analyzer elongation factor 125% to 400% (Claim 3)
- Multiple dependent claims require:
- PVP stabilizer
- SLS surfactant
- triacetin plasticizer
- specific dry weight ratios and dispersion solids formulation
Design-around pressure point: competitors can aim at either (a) different coating chemistry (ionic polymer, different polymer family than PVA, different barrier mechanism), (b) resin chemistry outside the two enumerated classes, (c) particle-size classes outside #40 mesh, or (d) barrier property targets outside elongation/tensile response.
What is the patent landscape likely to look like around this family concept?
A defensible landscape read requires the claim-to-technology mapping. Here the claim ties together three historically active research areas:
-
Drug-resin complexes for oral delivery
- Binding drugs to ion exchange resins for taste masking, solubility control, or controlled release.
-
Modified-release diffusion barriers
- Overcoating particles with diffusion barriers to slow release.
-
Aqueous suspension engineering
- Maintaining pourability, preventing aggregation, sustaining sedimentation control.
Within that space, US 8,062,667 is positioned as:
- a suspension-form specific system,
- using styrene/divinylbenzene resins,
- and a PVA-based cured non-ionic diffusion barrier applied from an aqueous dispersion.
Practical landscape inference for freedom-to-operate (FTO)
Given the tight recitations, infringement risk focuses on whether an accused product:
- uses resin complex particles in an aqueous suspension, and
- applies a cured polyvinylacetate barrier with plasticizer and a stabilizer, and
- meets at least one set of dependent quantitative performance/product parameters (PVA fraction, weight gain, plasticizer window, texture elongation, SLS presence, triacetin use).
If a competitor uses a different barrier polymer class (for example, acrylates, celluloses, ethylcellulose, Eudragit families) or an ionic barrier, they can fall outside core limitations unless the language is read broadly enough to treat those polymers as “polyvinylacetate” equivalents (the claims do not explicitly include equivalents; they specify PVA).
Claim-by-claim highlights that matter for mapping vs. designing around
Drug-resin complex + matrix
- Claim 1 sets: #40 mesh, resin class A or B, polymer/copolymer or hydrophilic polymer 3%-30% by weight (relative to resin complex).
Optimization knobs
- Claim 2: polymer matrix 5%-20%.
- Claim 4-5: resin subclasses explicitly called.
- Claim 41: polymer matrix about 10%-15%.
Barrier coating formulation
- Claim 15: PVA + PVP stabilizer 10:1, coating as an aqueous dispersion, plasticizer 5%-10% (of dry barrier solids in that dependent claim).
- Claim 21-22: plasticizer 5%-10% w/w solids; plasticizer is triacetin.
- Claim 43-44: cured barrier layer PVA at least 75% w/w or 75%-90% w/w.
- Claim 45: plasticizer 2.5%-20% w/w (relative to cured barrier).
Barrier mechanical property
- Claim 3: elongation factor 125%-400% by texture analyzer.
Particle composition ratios and process
- Claim 18 provides a detailed mixing/drying/milling recipe with:
- resin complex mixed with aqueous dispersion of PVA + PVP + SLS
- dispersion solids 30% w/w
- PVA 27%, PVP 2.7%, SLS 0.3% (within the dispersion)
- drying and milling through 40 mesh
Secondary diffusion barrier coated complex
- Claim 42: optionally adds a second diffusion barrier coated drug-resin complex-matrix containing a different drug.
Specific drug examples
- Claim 28 list plus targeted callouts 29-36.
Key takeaways
- US 8,062,667 claims a layered particulate suspension: drug-ion exchange resin complex embedded in a polymer matrix, then overcoated with a cured, water-permeable, non-ionic, PVA-based diffusion barrier prepared from an aqueous dispersion with plasticizer and stabilizer.
- The claim architecture narrows resin chemistry to sulfonated styrene/divinylbenzene or quaternary ammonium styrene/divinylbenzene and narrows key physical inputs to #40 mesh and polymer loading bands.
- Dependent claims tighten infringement mapping through specific coating system choices: PVP stabilizer, triacetin plasticizer, and SLS surfactant, plus performance constraints such as texture analyzer elongation and PVA weight fraction.
- The drug scope is broad in concept but supported by an explicit dependent drug genus list, indicating the invention’s novelty is anchored in the resin + particulate engineering + PVA barrier rather than one drug entity.
- For FTO, the principal risk test is whether a product uses the same PVA diffusion barrier system with plasticized, cured, non-ionic barrier attributes on resin-bound complexes sized for #40 mesh suspension.
FAQs
1) What is the single most important limitation for infringement mapping?
The diffusion barrier coating is a cured, high tensile strength, water permeable, water insoluble, non-ionic polymeric diffusion barrier that includes polyvinylacetate plus stabilizer and plasticizer, applied from an aqueous dispersion.
2) Can the claims cover both sulfonated and quaternary ammonium resins?
Yes. Claim 1 restricts ion exchange resin selection to either sulfonated styrene/divinylbenzene or styrene/divinylbenzene with quaternary ammonium functional groups.
3) How do the claims handle particle size?
They require the particulate matrix (and in some dependent claims, the complex particles) to be capable of passing through a #40 mesh screen.
4) Which dependent claims most directly constrain the formulation chemistry?
Claims 15, 18, 21-23, 43-46, 49-52, and 54-55 collectively lock in specific materials (PVA, PVP, SLS, triacetin) and quantitative fractions (polymer loadings, PVA weight %, plasticizer %, weight gain).
5) Do the claims require a single drug or can multiple drugs appear in the formulation?
The independent claim recites a drug bound to the resin complex; dependent claim 42 allows a second diffusion barrier coated drug-resin complex with a different drug, and claims 10-12 allow additional drug in the suspension base.
References
[1] US Patent No. 8,062,667.
