US Patent 6,489,329: Claim Scope, Core Technical Boundaries, and US Landscape

US Patent 6,489,329 claims a two-component pharmaceutical composition defined by (i) a pseudoephedrine component and (ii) a piperazinyl-phenylmethyl ethoxy acetic acid component (an enantiomer or racemate) in specific weight ranges, with optional dosage form and formulation features. The patent’s enforceable scope tracks three elements: component identity, mixture composition by weight, and dosage/formulation structure.

What does claim 1 cover in technical terms?

Core composition definition (independent claim 1)

Claim 1 is a composition claim with three limiting features:

Compound (i): pseudoephedrine, an individual optical isomer thereof, or a pharmaceutically acceptable salt
- Weight: about 70 to about 99% by weight
Compound (ii): 2-[2-[4[(4-chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]-acetic acid (an enantiomer or racemate), or a pharmaceutically acceptable salt
- Weight: about 1 to about 30% by weight
The composition “consists essentially of” the mixture, meaning:
- The composition contains the stated actives as the essential components.
- It may include carriers/excipients if they do not materially change the basic and novel characteristics of the invention (claim 3 expressly adds carriers/excipients).

Component interpretation

(i) pseudoephedrine covers multiple stereochemical variants and salt forms.
(ii) the acetic-acid piperazine ether is tied to a single chemical backbone:
- Racemate of the specified acid, or levorotary/dextrotary enantiomers, or salts.

Weight ranges define the practical boundary

Claim 1 sets the actives on a broad but bounded axis:

pseudoephedrine: 70% to 99%
chiral piperazinyl-ethoxy acetic acid: 1% to 30%

This is not a functional claim (no potency/clinical effect limitation appears). It is a structural composition claim anchored on identity + ratio.

How narrow are the ratio limits in dependent claims?

Claim 2: narrower ratio band

Claim 2 limits claim 1 to:

Compound (ii): about 3 to about 15 wt%
Compound (i): about 85 to about 97 wt%

This narrows the lower bound for the second active from claim 1’s 1% minimum to 3%, and caps the second active at 15% (vs 30% in claim 1).

Business implication: Claim 2 creates a stronger infringement position against formulations that choose the “mid-range” coupling of the second active with predominantly pseudoephedrine.

What excipient and dosage-form coverage exists?

Claim 3: carriers/excipients

Claim 3 adds:

“includes at least one pharmaceutically acceptable carrier or excipient.”

This makes the claim practical for solid oral formulations while keeping the core actives constrained.

Claim 4: dose amount

Claim 4 requires:

a dose containing about 15 to about 300 mg of the mixture of (i) and (ii).

This does not separately limit each component dose, but it constrains total mixture loading per dose unit.

Boundary effect: Many combination products may use fixed pseudoephedrine mg amounts; claim 4 adds a total-mixture constraint that can matter for unit-dose equivalents.

Claim 5: specific coated tablet architecture

Claim 5 requires a coated tablet with two structural zones and functional materials:

Tablet coating
- contains the effective amount of compound (ii)
Tablet core
- contains the effective amount of compound (i)
- contains a swellable hydrophilic polymer
both coating and core contain excipients/carriers.

This claim has three clear limitations:

Geographic separation of actives between coating and core:
- (ii) in the coating
- (i) in the core
A swellable hydrophilic polymer in the core
Standard excipient presence in both layers

Practical meaning: A formulation that places all actives together in the core would fall outside claim 5 even if it meets ratio and identity limits of claim 1.

Claim 6: capsule form

Claim 6 covers:

the pharmaceutical composition in the form of a capsule.

This is broad on its face: it does not add layer/controlled release architecture.

What is the enforceable claim strategy implied by this set?

The six claims create a tiered structure:

Claim 1: broad composition coverage by identity and weight ratio (plus “consists essentially of”).
Claim 2: narrower ratio band that strengthens validity-to-enforcement overlap against formulations with 3 to 15% of compound (ii).
Claim 3: explicitly permits excipients, preserving practical manufacturability.
Claim 4: unit-dose mixture loading range.
Claim 5: formulation-layer specificity with polymer and separation of actives.
Claim 6: capsule format.

This architecture suggests two likely infringement targets:

Direct product formulations matching the ratio and unit-dose ranges (claims 1 to 4).
Solid oral controlled or delayed release tablet designs using coating/core separation with hydrophilic swellable polymer (claim 5).

What does the “consists essentially of” language do to scope?

Claim 1 says the composition “consists essentially of” the two-actives mixture.

In practice, that language is a hard limit against materially different compositions. It generally allows excipients (claim 3 does), but it constrains:

additional active ingredients, if they materially change the novel characteristics, and
excipient systems that alter the basic functional behavior tied to the formulation concept.

Because claim 5 already specifies a coated tablet coating/core split and a swellable hydrophilic polymer, a manufacturer’s ability to change formulation excipients without moving materially beyond the basic characteristics will depend on how the product’s structure and dissolution behavior map to claim 5’s required elements.

How does this map to a patent landscape view in the US?

1) Likely relevant technology clusters

Even without a full prosecution history, the claim text indicates these landscape nodes:

Combination of pseudoephedrine with an enantiomeric piperazinyl acetic acid ether
- The ratio bands (1 to 30% wt of compound ii) imply intentional coupling beyond trace amounts.
Chiral specificity for compound (ii)
- Claim 1 covers racemate and individual enantiomers.
- Claim scope is not limited to one stereoisomer; it covers multiple, which broadens infringement coverage.
Solid oral formulation design
- tablet coating/core separation and swellable hydrophilic polymer (claim 5)
- capsule format (claim 6)

2) How to read this in infringement terms

For US enforcement and freedom-to-operate review, the key question is not whether a product contains the same actives, but whether it matches the exact legal boundaries:

Does the product include:
- pseudoephedrine (or a salt or optical isomer) at roughly 70 to 99 wt% of total actives?
Does it include:
- the specified piperazinyl-ethoxy acetic acid compound (racemate or enantiomer) at roughly 1 to 30 wt% of total actives?
If tablet:
- does it place (ii) specifically in the coating, and (i) in the core with a swellable hydrophilic polymer?

Because claim 1 is a “mixture consisting essentially of” structure, products that include the same actives but change ratios outside the bands (or shift actives spatially in a way that does not meet claim 5) may avoid some dependent-claim hooks, though claim 1 may still capture them depending on where ratios and solids distribution land.

What are the claim-strength implications for validity and design-around?

Ratio limitation as both strength and design knob

Strength: ratio constraints reduce the number of prior art combinations that could anticipate the claim, because the actives must co-occur at defined proportions.
Design-around: a competitor can attempt to avoid:
- claim 2 by using compound (ii) <3 wt% or >15 wt%
- claim 1 by using compound (ii) <1 wt% or >30 wt%

Coating/core architecture as a strong dependent hook

Claim 5 adds structural constraints that can be harder to meet inadvertently. It can be designed around by:

moving compound (ii) into the core,
removing the swellable hydrophilic polymer from the core,
eliminating the coating/core separation where (ii) is exclusively in the coating.

However, claim 1 and claim 2 still remain if the ratio and identity limits are met, unless the design-around also changes actives distribution and/or composition beyond claim boundaries.

Capsule route is broad

Claim 6 provides a simple format alternative. A capsule does not need to meet the coating/core polymer requirements, but it still must meet claim 1 composition and (if applicable) claim 2 ratio and claim 4 dose loading.

Potential overlap areas to watch in US filing strategy

Without the full bibliographic context of US 6,489,329 (filing date, assignee, and related family members), the practical landscape review should focus on overlap categories that are directly implicated by the claim language:

Pseudoephedrine + enantiomeric piperazinyl-ethoxy acetic acid combinations
Chiral selection claims for compound (ii)
Solid oral formulation patents that specify:
- swellable hydrophilic polymer matrices,
- coated tablet architectures,
- and actives allocated to coating vs core

In portfolio terms, this patent behaves like a cross between:

a composition ratio claim (claims 1 to 4), and
a formulation-layer claim (claim 5)

That combination often narrows design-around options because switching format alone (capsule vs tablet) may not avoid the ratio-limited composition claims.

Key claim chart (condensed)

Claim	Required elements	Quantitative limits	Structural/formulation limits
1	Pseudoephedrine component (i) + piperazinyl-ethoxy acetic acid component (ii)	(i) ~70 to ~99 wt%; (ii) ~1 to ~30 wt%	“Consists essentially of” mixture
2	Claim 1 composition	(i) ~85 to ~97 wt%; (ii) ~3 to ~15 wt%	None added
3	Claim 1 composition	None added	At least one acceptable carrier/excipient
4	Claim 1 or claim 3	Total mixture per dose: ~15 to ~300 mg	None added
5	Claim 3 + coated tablet	Ratio is claim 1/3 dependent	(ii) in coating; (i) in core; core has swellable hydrophilic polymer
6	Claim 3 + capsule	None added	Capsule format only

Key Takeaways

US 6,489,329 is a two-active combination composition patent anchored on pseudoephedrine plus a specific 2-[2-[4[(4-chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]-acetic acid enantiomer/racemate.
The core enforceable boundaries are identity plus weight ratio: claim 1 covers (i) 70-99 wt% and (ii) 1-30 wt%; claim 2 narrows to (i) 85-97 wt% and (ii) 3-15 wt%.
Dependent claims add practical constraints: unit-dose mixture amount (15 to 300 mg), plus a tablet architecture in which (ii) is in the coating and (i) is in a core containing a swellable hydrophilic polymer.
For landscape and design-around, the most direct avoidance levers are ratio band selection and, for tablets, actives placement (coating vs core) plus polymer inclusion.

FAQs

1) Does claim 1 require a specific enantiomer of the piperazinyl-ethoxy acetic acid?
No. It covers the racemate and individual enantiomers (levorotary or dextrotary), including pharmaceutically acceptable salts, within the specified 1 to 30 wt% band.

2) If a product matches the actives but uses compound (ii) at 2 wt%, is claim 2 implicated?
No for claim 2, because claim 2 requires ~3 to ~15 wt% of compound (ii). Claim 1 may still apply if the overall ratio falls within ~1 to ~30 wt%.

3) Is the swellable hydrophilic polymer required for all dosage forms?
No. The swellable hydrophilic polymer is only required in the dependent coated tablet claim (claim 5). Capsules (claim 6) do not impose that polymer restriction.

4) Can excipients be included without automatically losing coverage?
Yes. Claim 3 expressly requires that at least one pharmaceutically acceptable carrier or excipient is included, while claim 1 uses “consists essentially of” tied to the essential active mixture.

5) What is the most formulation-specific infringement hook in this patent?
Claim 5, because it requires (ii) in the coating, (i) in the tablet core, and a swellable hydrophilic polymer in the core, with acceptable carriers/excipients in both regions.

References

[1] U.S. Patent 6,489,329. “Pharmaceutical composition comprising pseudoephedrine and an enantiomeric piperazinyl-ethoxy acetic acid.” Claims 1-6.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	1774097	⤷ Start Trial
Australia	723364	⤷ Start Trial
Brazil	9701686	⤷ Start Trial
Colombia	4820432	⤷ Start Trial
United Kingdom	2311940	⤷ Start Trial
United Kingdom	9706842	⤷ Start Trial
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Details for Patent: 6,489,329

Summary for Patent: 6,489,329