United States RE33239 Patent Landscape for Packaged 5-ASA Enema Solutions: Scope, Claim Strength, and Expiration Risk

RE33239 is a US reissue patent built around a narrow formulation-and-packaging “system” for 5-aminosalicylic acid (5-ASA, aka 5-aminosalicylic acid) enema solutions or suspensions. The core claim theme is the combination of (i) 5-ASA and specific stabilization chemistry (chelating agent + antioxidant + buffer) at an acidic, controlled pH (about 4.8 and variants), and (ii) a packaging architecture that limits oxygen, moisture and light exposure by using inert gas inside a plastic bottle and a diffusion-tight, light-impervious outer package sealed in the same inert gas.

What is RE33239, and what exactly do its claims cover?

Answer: RE33239 claims a packaged enema solution or suspension containing 5-ASA (or its salt/ester), a chelating agent (eg EDTA), an antioxidant (pyrosulfite salts), and a buffer system that holds the product at pH about 4.8 (or generally 4 to 5). The product must be contained in a plastic bottle filled and stored under an inert gas and then packaged in a diffusion-tight, light-impervious package in the same inert gas.

Claimed invention architecture (technology stack)

Actives and stabilization inputs
- 5-ASA or pharmaceutically acceptable salt/ester
- Chelating agent: EDTA or alkali metal EDTA salts
- Antioxidant: sodium pyrosulfite or potassium pyrosulfite
- Buffer: citric acid/sodium hydroxide in dependent claims; other buffer variants appear (including sodium bicarbonate + hydrochloric acid in the earlier claim set you provided, though it is shown as bracketed/redacted content in your text)
Target physicochemical window
- pH about 4.8 (primary claim in your excerpt)
- Expanded range claims: pH 4 to 5, and narrower pH ranges depending on dependency (about 4.8 and 4.5 to 5)
Packaging and atmosphere constraints
- Bottle: plastic, including polyethylene (explicitly claimed)
- Inert gas inside bottle: argon, nitrogen, or carbon dioxide
- Outer package: diffusion-tight, light-impervious, containing the same inert gas
- Explicit packaging sequencing concepts:
  - bottle produced from deoxidized polyethylene granulate (nitrogen alternation evacuation/flooding)
  - bottle filled under inert gas
  - bottle packed into an “aroma-tight” bag welded before exposure to air
  - bag described as plastic aluminum laminate

This combination is the enforcement backbone. Avoiding any one of these elements typically changes infringement posture from “literal match” to “design-around or equivalence argument,” depending on how strictly each element is required (“consisting essentially of” narrows the admissible equivalents).

How broad is RE33239 claim scope across formulations, pH, and packaging?

Answer: Scope is moderately broad on the inert gas species (3 options) and on general pH range (4 to 5), but it is narrow on the stabilization chemistry and the packaging system. The claims are tightly anchored to:

5-ASA + (EDTA/EDTA salt) + (pyrosulfite antioxidant) + buffer
acidic pH window
inert-gassed plastic bottle and diffusion-tight light-impervious outer packaging in the same inert gas

Claim stratification from independent to dependent

Your excerpt shows two major “independent-style” anchors:

Claim 1 (packaging + stabilization at pH about 4.8)
“consisting essentially of” language plus:
- pH about 4.8
- plastic bottle under inert gas
- diffusion-tight light-impervious package with same inert gas as bottle
Claim 14 (packaging + stabilization at pH 4 to 5)
Similar architecture but pH broadened (4 to 5)

Everything else is a mix of:

specification of antioxidant (sodium vs potassium pyrosulfite; potassium singled out)
specification of chelator (EDTA vs alkali metal EDTA salts)
specification of buffer composition (citric acid + sodium hydroxide)
specification of purity (5-ASA sufficiently pure to avoid autooxidation with no additional HPLC/UV peaks)
specification of packaging materials and manufacturing steps (polyethylene deoxidation, extrusion and inert-gas bottle formation, inert-gas bagging with welding; plastic aluminum laminate)

What parts are likely “hard requirements” vs “soft features”?

Hard requirements for likely literal infringement
- 5-ASA (or acceptable salt/ester) present in “effective amount”
- chelating agent present (EDTA or specified EDTA species in some claim dependencies)
- antioxidant present (pyrosulfite salts)
- buffer present with pH within claimed range
- plastic bottle under inert gas
- outer package diffusion-tight and light-impervious in same inert gas
Softening in scope via “consisting essentially of” “Consisting essentially of” allows minor additional ingredients that do not materially affect the basic and novel characteristics. That tends to make infringement fights revolve around whether an added stabilization agent, different chelator, or different buffer materially changes the stabilized product characteristics the claim protects.

Which formulation parameters are explicitly claimed (and therefore infringement-critical)?

Answer: RE33239 explicitly claims key ranges for pyrosulfite, chelator amounts, buffer ingredients, and a defined purity requirement in at least one dependent claim.

Pyrosulfite antioxidant ranges

Sodium pyrosulfite / potassium pyrosulfite variants appear via dependent claims.
Quantification (your excerpt):
- 50 to 200 mg per 100 mL (claim 17 for potassium pyrosulfite)
- For citric acid/sodium hydroxide + sodium EDTA + sodium pyrosulfite variant, quantitative examples appear in claim 12 and claim 13:
  - sodium pyrosulfite: 50 mg to 200 mg
  - sodium EDTA: 5 mg to 30 mg (claim 12)
  - citric acid: 0.5 to 1.5 g
  - sodium hydroxide: 0.5 to 2 g
- Alternative example composition in claim 13:
  - 5-ASA about 1 g
  - sodium pyrosulfite about 200 mg
  - citric acid about 1 g
  - sodium EDTA about 20 mg
  - sodium hydroxide adjusted for pH about 4.8

Chelating agent specificity

EDTA is explicitly named as the chelating agent in a dependent claim (claim 2 in your excerpt).
Another dependent claim specifies EDTA as ethylenediaminetetraacetic acid or alkali metal salt (claims 18-19).
Independent claims are phrased generically (chelating agent), but your excerpt indicates EDTA is the intended chelator locked to the disclosure and likely the claim support.

Buffer chemistry and pH windows

Buffer system is anchored to acidic conditions:
- claim 1: pH about 4.8
- claim 14: pH from 4 to 5
- additional claims narrow to pH 4.5 to 5 and about 4.8
Dependent claim 2 specifies:
- buffer comprises citric acid and sodium hydroxide
Another bracketed buffer variant in your excerpt indicates:
- sodium bicarbonate and hydrochloric acid, though the way it appears suggests it may be a removed/altered claim element in the source document text you provided.

5-ASA purity requirement (autooxidation control)

Claim 4 in your excerpt requires:
- 5-aminosalicylic acid “sufficiently pure to avoid autooxidation,” with “no additional HPLC, fluo(spectrophotometric) and spectrophotometric peaks.” This is a manufacturing and analytical control hook. It is a common avenue in litigation: not whether the packaging works, but whether the delivered drug substance meets the stability-related analytical purity metric tied to reduced autooxidation.

How do the packaging and inert-atmosphere constraints drive claim strength?

Answer: The packaging limitations are designed to defeat conventional “open-bottle” or ambient-exposed competitor products. They also create evidence leverage around manufacturing process and packaging line controls.

Inert gas selection and co-packaging in the same inert atmosphere

Inert gas is explicitly defined as one of:
- argon, nitrogen, carbon dioxide
The claims require:
- plastic bottle under inert gas
- outer diffusion-tight, light-impervious package containing the product in the same inert gas as present in the bottle

This means a competitor cannot simply inert-gas fill the bottle then move into an outer package equilibrated to air. That divergence is central to non-infringement arguments if “same inert gas” is interpreted strictly.

Bottle material: polyethylene

Dependent claims specify the plastic bottle as polyethylene.
Another dependent claim covers polyethylene granulate deoxidation:
- alternately evacuating granulate and flooding with nitrogen gas
- extruding and forming bottle under inert gas
- bottle filled with enema solution

This is process-specific. Competitors using different resins (eg PP, PET, multilayer barrier polymers) may argue they avoid the “polyethylene bottle” element in dependent claim embodiments, but they could still infringe independent claim elements if polyethylene is not required there.

Diffusion-tight light-impervious packaging

Outer package is defined as:
- diffusion-tight
- light-impervious
Later dependent claims describe:
- “aroma-tight bag” sealed by welding before contact with air
- bag as “plastic aluminum laminate”

These features are also favorable for enforcement because they leave a paper trail through packaging material specs and line procedures (gas blanketing, seal sequence).

What are the likely design-around strategies against RE33239?

Answer: RE33239’s enforceable perimeter clusters around (i) stabilization chemistry and (ii) atmosphere + barrier packaging. Practical design-arounds typically target at least one cluster:

1) Change stabilization system (target the “chelating agent + antioxidant + buffer + pH” core)

Replace EDTA chelation with another chelator not captured by the “chelating agent” limitation (but note: claim 1 is generic “chelator,” so this strategy is stronger against dependent EDTA-specific claims than against independent generic chelator claims).
Use an antioxidant system not based on pyrosulfites (stronger against dependent pyrosulfite-specific claims; harder against independent claims if antioxidant category is interpreted broadly).
Adjust pH outside the claimed window (hard to do because formulation stability and solubility likely tie pH tightly to 5-ASA stability and rectal tolerability).

2) Break the packaging “same inert gas” requirement

Inert-fill the bottle but package into an outer barrier that is not in the same inert atmosphere, or where residual oxygen/moisture is not controlled as claimed.

3) Avoid polyethylene bottle, deoxidized polyethylene process, or welding sequence

Use a different bottle polymer and a different resin conditioning method, and ensure packaging sequence does not match deoxidized granulate + inert-gas bottle formation + welded aroma-tight bag under inert conditions.

4) Switch product form (solution vs suspension)

Dependent claims explicitly include suspension (claim 21 and claim 26). If a competitor uses a true solution format rather than a suspension, it may avoid those dependent claims, but independent claims still cover “solution or suspension” in the title and core wording.

What does the number RE33239 imply for patent term and reissue effects?

Answer: “RE” indicates reissue. In US practice, reissue can extend the patent life in some circumstances, subject to reissue timing rules and the original filing priority/expiration framework. The reissue does not rewrite prior art as if it were new. The practical implication for exclusivity planning is that the operative expiration is tied to the underlying application priority and the reissue dates that affect adjustment, not to the reissue number alone.

Because the user-provided content does not include the filing date, original non-provisional date, reissue grant date, or maintenance status, a precise expiration computation cannot be produced from the excerpt alone.

How strong is the patent estate for enforcement given these claim features?

Answer: The claims are strong in a litigation setting because they combine:

a chemically specific stabilization recipe (pyrosulfite + chelator + buffer at acidic pH), and
a mechanically specific packaging method (inert-gassed plastic bottle + diffusion-tight light-impervious outer package in the same inert gas),
with additional manufacturing specificity (deoxidized polyethylene granulate, inert formation, sealed welded laminate bag), and
analytical purity requirements tied to autooxidation control.

Strength is highest where accused products replicate both chemistry and packaging. If competitors diverge on either cluster, the case becomes more dependent on claim construction of “consisting essentially of,” “diffusion-tight light-impervious,” and “same inert gas as present in the bottle,” plus proof of infringement at the product and packaging configuration level.

US competitive and regulatory exposure: what matters for enema 5-ASA products?

Answer: The key exposure for generic or alternate brands is not only the active ingredient identity (5-ASA) but whether they match:

the stabilized acidic pH formulation at the claimed values,
the stabilization chemistry (EDTA and pyrosulfite),
and the inert-atmosphere packaging architecture.

For Paragraph IV-type challenges or narrow-formulation licensing, the liability model typically hinges on:

whether the generic filing is tied to a product configuration that can satisfy the stabilization and packaging requirements without infringing.

Claim-by-claim scope map (from your excerpt)

Claim (per your text)	Core coverage	Key limitations that narrow scope
1	Packaged enema solution/suspension with 5-ASA + chelator + antioxidant + buffer at pH ~4.8; plastic bottle under inert gas; diffusion-tight light-impervious package in same inert gas	pH about 4.8; inert gas “same” in bottle and outer package; “consisting essentially of” limits additives
2	Claim 1 where chelator is EDTA, antioxidant sodium pyrosulfite, buffer citric acid + sodium hydroxide	EDTA + sodium pyrosulfite + citric/sodium hydroxide
4	Claim 1 with 5-ASA purity metric to avoid autooxidation (no extra HPLC/fluoro/spectro peaks)	analytical purity requirement
5	Claim 1 inert gas is argon/nitrogen/CO2	specific inert gas set
6	Claim 1 consisting essentially of 5-ASA (or salt/ester), EDTA, sodium pyrosulfite, citric acid, sodium hydroxide, purified water	essentially complete ingredient list
7	Claim 1 bottle is polyethylene	bottle polymer
8-10	Deoxidized polyethylene granulate + extrusion/inert formation + inert-gas filling + direct conveying into welded aroma-tight bag (before air contact)	process sequencing and packaging film type
11	Claim 10 bag is plastic aluminum laminate	outer package structure
12-13	Quantitative per-100 mL ranges for 5-ASA, antioxidant, chelator, buffer components at pH maintained at ~4.8	specific dose ranges
14	Independent-style at pH 4-5 with same packaging concept	pH window broadened
15-17	Antioxidant sodium/potassium pyrosulfite; potassium specified; per-100 mL potassium pyrosulfite 50-200 mg	antioxidant species and dose
18-19	Chelator is EDTA or alkali metal EDTA salts	chelator species
20	pH 4.5-5	narrower pH window
21	“is a suspension”	dosage form type
22-26	“consisting essentially of” composition with potassium pyrosulfite + alkali metal EDTA salt + buffer at pH 4-5; includes pH 4.5-5 and about 4.8; potassium pyrosulfite 50-200 mg; suspension	tight recipe plus packaging system

What patent landscape questions remain unanswered by the provided excerpt?

A complete patent landscape requires:

the full bibliographic record for RE33239 (original patent number, application dates, inventors/assignee, reissue dates),
the full citation set of related US patents (continuations, divisionals, method-of-use, formulation, and packaging patents),
and the FDA/Orange Book mapping to the specific listed 5-ASA enema products.

Your prompt provides only the claim text and the patent identifier. Without bibliographic and Orange Book and litigation data, any attempt to enumerate landscape competitors, expiration dates, or Paragraph IV statuses would be incomplete.

Key Takeaways

RE33239 protects a packaged 5-ASA enema stabilization system combining (1) EDTA-type chelation, (2) pyrosulfite antioxidant, (3) acidic buffer at pH about 4.8 or pH 4 to 5, and (4) inert-atmosphere packaging using a plastic bottle and a diffusion-tight light-impervious outer package in the same inert gas.
Independent claim scope is anchored to the chemistry + packaging system, while dependent claims narrow to specific antioxidant/chelator species, quantitative dose ranges, polyethylene and deoxidation manufacturing, and weld-sealed laminate barrier bagging.
Enforcement leverage is highest when an accused product matches both the stabilization chemistry and the inert-gas barrier packaging architecture.
Practical design-arounds focus on breaking at least one cluster: pH window, pyrosulfite/chelator/buffer recipe, or the “same inert gas” diffusion-tight, light-impervious packaging requirement.

FAQs

1) Does RE33239 cover both enema solutions and suspensions?

Yes. The claim language covers “packaged enema solution or suspension,” and some dependent claims further specify suspension.

2) Is the inert gas limited to nitrogen only?

No. The inert gas is specified as argon, nitrogen, or carbon dioxide in the dependent claim set in your excerpt.

3) What is the pivotal stabilization chemistry in RE33239?

A chelating agent (EDTA/EDTA salt), an antioxidant (pyrosulfite), and a buffer that holds the product at acidic pH (about 4.8 or 4 to 5), in combination with 5-ASA.

4) What packaging element is most likely to determine infringement?

The requirement that the plastic bottle is under inert gas and that the product is then placed in a diffusion-tight light-impervious package in the same inert gas as present in the bottle.

5) Can a competitor avoid infringement by changing bottle material?

Dependent claims specify polyethylene; switching bottle polymer can reduce or avoid infringement of dependent claims, but independent claims still require a plastic bottle under inert gas and the outer barrier in the same inert atmosphere, so polymer-only substitution may not fully remove risk.

References

No sources were provided in the prompt, and no bibliographic or Orange Book records were included in the content you supplied, so no citations can be generated without introducing non-provided material.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	1230056	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: RE33239

Summary for Patent: RE33239