United States Patent 6,488,962: Scope, Claim Strength, and US Landscape

US Patent 6,488,962 is directed to a controlled-release oral dosage form built around a solid, monolithic, water-swellable matrix that expands unrestrictedly along two orthogonal axes of unequal length. The protection hinges on a tightly defined geometric swelling profile (unswollen dimensions and post-immersion minimum lengths over defined times) combined with a shape projection constraint (oval or parallelogram) and a water-swellable polymer (often poly(ethylene oxide) (PEO)). The drug identity is also narrowed through multiple dependent claims that name specific actives.

Because the claims are structured as a device-geometry + swelling kinetics + polymer and drug properties combination, the patent landscape is best understood as a blocking position against similar swellable “non-circular” monolithic matrix systems rather than a broad method-of-use monopoly for any controlled-release oral formulation.

What do the independent claim elements require?

Claim 1: What must be present for infringement?

Claim 1 defines the core protected invention as follows (paraphrased only for readability; all limiting concepts are retained):

A controlled-release oral drug dosage form that releases drug into at least a portion of the region defined by the stomach and upper gastrointestinal tract.

It must comprise:

Solid monolithic matrix with drug contained therein.
Matrix is non-circular in shape with first and second orthogonal axes of unequal length.
The matrix is one that swells in an unrestricted manner along both axes upon imbibition of water.
Geometric swelling performance constraints
- The longer axis has a maximum length of 3.0 cm when the matrix is unswollen.
- The shorter axis achieves a minimum length of 1.2 cm within one hour of immersion in water.
Shape projection constraint
- When projected onto a plane, the matrix is either an oval or a parallelogram.

This independent claim is not limited to a specific drug or a specific polymer in claim 1, but it does require:

Monolithic form (not a coated pellet blend).
Water uptake swelling behavior that is unrestricted along both orthogonal axes.
Specific initial and time-dependent dimensional parameters.

Claim 1: What it excludes by implication

Claim 1’s “unrestricted swelling along both axes” and the “monolithic matrix” language tends to exclude:

Systems where swelling is constrained by membranes, rings, or anchored edges that restrict expansion.
Multipart or layered matrix systems whose dominant drug release mechanism is not governed by unrestricted swelling dimensions.
Approaches that focus on controlled release by diffusion through pores without bulk swelling to the claimed lengths.

How narrow is the timing and the geometry?

Claims 2–4: Shorter-axis swelling kinetics

These claims provide time-dependent refinements of claim 1:

Claim 2: shorter axis reaches minimum 1.2 cm within 30 minutes
Claim 3: shorter axis reaches minimum 1.3 cm within 1 hour
Claim 4: shorter axis reaches minimum 1.3 cm within 30 minutes

These additions tighten infringement risk for products that swell more slowly or less than the claimed thresholds.

Claims 5–7: Shorter-axis unswollen size ranges

These define the starting dimension when unswollen:

Claim 5: shorter axis length 0.7 to 1.5 cm (unswollen)
Claim 6: shorter axis length 0.75 to 1.2 cm (unswollen)
Claim 7: shorter axis length 0.8 to 1.0 cm (unswollen)

Claim 8–9: Longer-axis unswollen size ranges

Claim 8: longer axis maximum length 2.5 cm (unswollen)
Claim 9: longer axis length 1.5 to 2.5 cm (unswollen)

Geometry summary table (as claimed)

Parameter	Claim language	Practical meaning for design
Longer axis (unswollen) upper bound	≤ 3.0 cm (Claim 1)	Initial length cap
Longer axis (unswollen) tighter	≤ 2.5 cm (Claim 8)	Design space reduction
Longer axis (unswollen) range	1.5 to 2.5 cm (Claim 9)	Must land inside range
Shorter axis (unswollen) ranges	0.7–1.5 cm (C5); 0.75–1.2 cm (C6); 0.8–1.0 cm (C7)	Starting width constraints
Shorter axis swelling after time	≥1.2 cm at 1 hour (C1); ≥1.2 cm at 30 min (C2)	Kinetics requirement
Shorter axis swelling higher threshold	≥1.3 cm at 1 hr (C3); ≥1.3 cm at 30 min (C4)	Faster or greater swelling requirement
Swelling shape	projection = oval or parallelogram	Strict 2D projection form

What polymers are covered, and how does that shape claim enforceability?

Claims 10–14: Water-swellable polymer scope

Claim 10 limits claim 1 to a “water-swellable polymer” matrix. Claims 11–14 then enumerate polymer classes and preferred selections:

Claim 11: water-swellable polymer selected from:
poly(ethylene oxide), poly(vinyl alcohol), cellulose, alkyl-substituted cellulose, hydroxyalkyl-substituted cellulose, crosslinked polyacrylic acids, xanthan gum
Claim 12: water-swellable polymer selected from:
PEO, poly(vinyl alcohol), hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose
Claim 13: water-swellable polymer selected from:
PEO, hydroxypropylmethyl cellulose, hydroxyethyl cellulose
Claim 14: polymer is poly(ethylene oxide)

This polymer dependency is significant because it gives the patent a second layer of enforceability: even if a competitor uses the same geometry, they can try to escape by switching polymer class or by using a polymer that does not match the enumerated water-swellable polymers.

Claims 15–19: PEO molecular weight + drug solubility constraints

Claims 15–17 and 18–19 further narrow by combining:

Drug solubility at 37°C (water solubility expressed as parts by weight water per parts by weight drug)
PEO viscosity-average molecular weight ranges

Solubility and molecular weight pairings

Claim	Drug solubility at 37°C (water)	PEO viscosity-average MW
Claim 15	≥ 1 part drug / 20 parts water	~2,000,000 to ~7,000,000
Claim 16	≥ 1 part drug / 10 parts water	~2,000,000 to ~7,000,000
Claim 17	≥ 1 part drug / 3 parts water	~2,000,000 to ~7,000,000
Claim 18	0.005% to 10% by weight	~200,000 to ~2,000,000
Claim 19	0.01% to 5% by weight	~200,000 to ~2,000,000

These constraints function as a compatibility gate: even a geometric match may fall outside dependent claim scope unless drug-polymer solubility relationships align with the claimed solubility category and the PEO MW.

How broad is the drug coverage?

Drug is named in dependent claims

Claims 20–27 name specific actives:

Claim 20: drug is selected from lisinopril, acyclovir, metformin hydrochloride (“rhetformin hydrochloride” appears as a transcription/typographical OCR artifact), baclofen, ciprofloxacin, furosemide, cyclosporin, sertraline hydrochloride, calcium carbonate
Claim 21: drug is an antibiotic
Claim 22: drug is an angiotensin converting inhibitor
Claim 23: ACE inhibitor is one of lisinopril, enalapril, captopril, benazepril
Claim 24: drug is acyclovir
Claim 25: drug is metformin hydrochloride
Claim 26: drug is baclofen
Claim 27: drug is ciprofloxacin

Practical scope implication

Claim 1 itself does not require any specific drug identity.
But the dependent claims create “laddered” coverage: a product containing a named drug with matching polymer and geometry likely risks broader enforceability by landing on specific narrower claim sets.

Claim-structure risk profile (how a competitor would test infringement)

Key infringement hinges

In practice, infringement analysis for US 6,488,962 will turn on whether the accused product meets all limitations in:

Matrix geometry and swelling profile:
- non-circular monolithic matrix
- oval or parallelogram projection
- orthogonal axes of unequal length
- unswollen long-axis max and unswollen short/long ranges (if asserted via dependent claims)
- measured swelling dimension thresholds by defined immersion times
Unrestricted swelling mechanism upon water imbibition (not constrained expansion)
Polymer identity and MW if the asserted claim is dependent (10–19)
Drug solubility category at 37°C if the asserted claim is dependent (15–19)
Drug identity if asserted via 20–27

Design-around vectors implied by the claim language

The claim set suggests several straightforward “escape hatches” used in similar litigations:

Use a circular/other-than-oval-parallelogram projection geometry.
Engineer swelling to be restricted (anchored edges, rigid constraint, or swelling that does not achieve the claimed unrestricted axis expansion).
Avoid the claimed unswollen axis dimensions and/or the time-dependent minimum swelling lengths.
Use a polymer system outside the enumerated water-swellable polymers in the dependent claims.
Use PEO with a viscosity-average molecular weight outside the specified ranges if the asserted dependent claim is 15–19.
Select drugs outside the enumerated list if the asserted dependent claim is 20–27 (though claim 1 could still be asserted).

US patent landscape positioning (what surrounds it)

Where this patent sits

Based on the claim structure, US 6,488,962 aligns with a specific sub-family of controlled oral dosage forms:

Monolithic swellable matrices (bulk expansion drives release)
Hydrophilic water-swellable polymers, with PEO explicitly featured
Geometry-driven GI residence and release control through dimensional swelling kinetics
Oval/parallelogram projection constraint suggests the inventors targeted a particular “tablet shape” category with predictable swelling expansion

Competitive overlap expected

In the US controlled-release landscape, overlap typically occurs with:

swellable hydrophilic tablet formulations using PEO or cellulose derivatives
dosage forms where swelling rate and matrix expansion correlate to gastric/upper GI residence
bilayer or layered swellable systems where swelling may be non-unrestricted or constrained

The litigation-relevant distinction is not “swellable tablet” in general, but:

unrestricted swelling along two orthogonal unequal axes
measured axis length thresholds within specific times
projection geometry limitation

Landscape in terms of claim susceptibility

Given the dimensional and kinetic thresholds, the patent is most vulnerable to:

accused products engineered to swell differently (even if they swell overall)
shapes that deviate from oval/parallelogram projection
matrix structures that are not monolithic or do not expand unrestrictedly along both orthogonal axes

Conversely, it is strongest against products that copy:

the same swelling kinetics (30 min and 1 hr axis thresholds)
the same unswollen dimensions and aspect ratios
the same PEO type (and MW) plus drug solubility match when dependent claims are asserted

How to read the scope: independent vs dependent coverage map

Coverage map by claim layers

Claim layer	What expands the claim’s reach	What narrows the claim’s reach
Claim 1 (independent)	Broad drug coverage	Strict geometry, monolithic swelling behavior, axis/time thresholds
Claims 2–4	Adds time-specific swelling minima	Narrows to faster swelling products
Claims 5–9	Adds starting dimension ranges	Narrows to specific initial sizes/aspect ratios
Claims 10–14	Adds polymer class	Narrows to enumerated water-swellable polymers
Claims 15–19	Adds PEO MW + drug solubility range	Narrows to specific formulation-property combinations
Claims 20–27	Adds specific drugs and drug classes	Narrows to actives matching enumeration

Key Takeaways

US 6,488,962 protects a controlled-release oral dosage form where a solid monolithic, non-circular, orthogonally-defined geometry swells unrestrictedly in water and is projected as an oval or parallelogram.
The enforceability core is dimension-based swelling performance: long axis ≤ 3.0 cm (unswollen) and short axis ≥ 1.2 cm within 1 hour, with dependent claims locking in 30-minute and 1.3 cm thresholds.
Dependent claims add strong formulation hooks: water-swellable polymer lists and, for PEO, specific viscosity-average molecular weight ranges plus drug solubility at 37°C categories.
Drug coverage becomes sharply enumerated in later dependents (lisinopril, acyclovir, metformin HCl, baclofen, ciprofloxacin, and others) while claim 1 stays drug-agnostic.
The likely competitive threat and litigation focus is on products that replicate the shape projection plus swelling kinetics and axis lengths, not simply on any hydrophilic swellable matrix tablet.

FAQs

1) Is this patent limited to specific drugs?

Claim 1 is not limited to a specific drug identity. Drug specificity appears in dependent claims (notably Claims 20, 22–27).

2) What is the most important limitation in Claim 1?

The most infringement-critical limitation is the swelling profile tied to orthogonal unequal axes, including unswollen axis size and shorter-axis minimum length achieved within defined immersion times, plus the oval/parallelogram projection constraint.

3) Can a competitor avoid infringement by changing the polymer?

Yes, at least for dependent claims. Claims 10–14 and 15–19 narrow the matrix to enumerated water-swellable polymers and, in key dependents, to PEO with specific viscosity-average MW and drug solubility categories.

4) Does the patent cover layered or non-monolithic swellable systems?

Claim 1 requires a solid monolithic matrix. Systems that are layered, segmented, or not monolithic face higher claim-coverage risk.

5) What shape formats are explicitly allowed?

When projected onto a plane, the matrix is limited to oval or parallelogram in claim 1, which is a practical design constraint.

References

[1] US Patent No. 6,488,962. United States Patent and Trademark Office.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	256455	⤷ Start Trial
Australia	2001239893	⤷ Start Trial
Australia	3989301	⤷ Start Trial
Canada	2412671	⤷ Start Trial
Germany	60101581	⤷ Start Trial
Denmark	1294363	⤷ Start Trial
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Details for Patent: 6,488,962

Summary for Patent: 6,488,962