Patent 5,422,123 (US 5,422,123): Scope, Claim Coverage, and US Patent Landscape for Controlled-Rate Swelling/Gelling Deposit-Core With Elastic Support-Platform
What does US Patent 5,422,123 claim for controlled-rate release systems?
US 5,422,123 claims a tablet-like controlled-release architecture that pairs a swelling/gelling deposit-core with an elastic, partially covering support-platform that follows hydration-induced changes and controls release by slow solubility and/or gelation in aqueous fluids. The independent claim defines the system structure, the polymer selection logic (swelling-to-gelling ratio), and the functional behavior of the elastic support-platform during hydration.
Claim 1: System architecture and functional limitations (core + elastic support)
Independent claim 1 recites:
- Deposit-core with defined geometry containing:
- effective amount of active substance
- at least one member selected from:
- a polymer that swells in contact with water/aqueous liquids, and/or
- a gellable polymeric material
- with a swelling polymer:gelling polymer ratio between 1:9 and 9:1
- or a single polymer having both swelling and gelling properties
- Support-platform applied to the deposit-core:
- is an elastic support
- partially covers deposit-core surface
- follows changes due to hydration of the deposit-core
- is slowly soluble and/or slowly gellable in aqueous fluids
Core implications:
- The claim is not limited to any specific active ingredient. It is platform-driven.
- The claim requires both:
- a specific polymer system inside the core (swelling and/or gelling, with defined ratio range), and
- a specific elastic, partially covering, slow-soluble/slow-gellable support layer that mechanically tracks swelling during hydration.
Claim 2: Support-platform composition structure
Claim 2 narrows support-platform composition:
- support-platform comprises:
- polymer that is slowly soluble or slowly gellable in aqueous liquids, plus
- a plasticizing substance
Claim 3: Plasticizer species list
Claim 3 narrows plasticizers to a closed list:
- polyoxyethylene glycols
- castor oil
- hydrogenated castor oil
- ethyl phthalate
- butyl phthalate
- natural glycerides
- synthetic glycerides
- semisynthetic glycerides
Claims 4–10: Quantitative and performance constraints
- Claim 4: plasticizer represents 2–15 wt% of the support-platform.
- Claim 5: binder acting substances in support-platform:
polyvinylpyrrolidone, methylcellulose, ethylcellulose, gum arabic, alginic acid.
- Claim 6: hydrophilic agent list:
mannitol, lactose, starch, colloidal silica.
- Claim 7: hydrophobic agent list:
hydrogenated castor oil, magnesium stearate, fatty substance, wax, natural/synthetic glycerides.
- Claim 8: support-platform thickness 0.5–0.8 mm.
- Claim 9: support-platform thickness about 1 mm.
- Claim 10: support-platform remains intact until complete release of active substance.
Scope note: Claims 8 and 9 overlap with a specific thickness band conceptually; depending on prosecution history and construction, “about 1 mm” can overlap 0.5–0.8 depending on claim construction standards, but the literal text creates distinct thickness embodiments.
Claim 11: Manufacturing process
Claim 11 defines a preparation method:
- Granulate deposit-core ingredients per claim 2
- Compress granulated deposit-core to defined geometrical form
- Prepare support-platform granular mixture by:
- screening and mixing support-platform substances per claim 2 (so composition tracked to Claim 2 limits)
- Apply support-platform onto portion of deposit-core surface by:
- compressing to form partially covering support-platform
- Result is a tablet
Claim 12: Product-by-process
Claim 12 is a product defined by the process of claim 11:
- A tablet produced by the claimed process.
What additional coverage does claim 13 add over claim 1?
Claim 13 is a broader “deposit-core defined in geometrical form” system with expanded lists for both core polymers and support-platform polymers and a tighter, explicit support-platform composition weight range. It also includes an explicit internal polymer ratio for the core.
Core composition in claim 13
Deposit-core contains:
- active substance: 1%–95% by weight of deposit-core
- swelling polymer b):
- crosslinked sodium carboxymethylcellulose
- crosslinked hydroxypropylcellulose
- polyhydroxypropyl-methylcellulose (sufficiently high MW to swell)
- carboxy-methyl starch
- potassium methacrylate/divinylbenzene copolymer
- crosslinked polyvinylpyrrolidone
- polyvinyl alcohol
- gelling polymer c):
- methylcellulose
- non-crosslinked polyvinylpyrrolidone
- ratio b:c between 1:9 and 9:1
Support-platform in claim 13
Support-platform comprises:
- polymer 1 (slowly soluble/slowly gellable), selected from:
- polyhydroxypropylmethylcellulose
- polyvinyl alcohol
- polyacrylate
- polymethacrylate
- polyhydroxypropylcellulose
- polysodium carboxymethylcellulose
- plasticizing substance selected from:
- polyethylene glycol
- castor oil
- hydrogenated castor oil
- ethyl phthalate
- butyl phthalate
- natural glycerides
- synthetic glycerides
- semisynthetic glycerides
Support-platform polymer content constraint:
- polymer 1 is 30%–90 wt% of the support-platform.
How claim 13 differs materially from claim 1:
- Claim 1 is anchored by generic “swelling polymer/gellable polymer” concept plus a ratio range and elastic partially covering support.
- Claim 13 is anchored by specific species lists for both core and support polymers and gives more explicit quantitative ranges (active % and support polymer wt%).
What is the practical claim scope: what systems fall inside vs outside?
“Elastic support-platform that follows hydration” is the key functional-mechanical limitation
The most critical claim boundary is the support-platform’s behavior:
- It must partially cover the deposit-core
- It must be elastic
- It must follow changes due to hydration of the deposit-core
- It must be slowly soluble and/or slowly gellable in aqueous fluids
- It must remain intact until complete release (claim 10)
Design-around risk concentrates around whether the support layer:
- is truly elastic under hydration,
- tracks swelling-induced dimensional changes instead of cracking/delaminating, and
- persists long enough to reach “complete release.”
Ratio limitation (1:9 to 9:1) constrains internal formulation space
The claims require a swelling/gelling ratio between 1:9 and 9:1.
- If a formulation uses only swelling polymer without a gelling component (or uses a single polymer with both functions), claim 1 may still be met due to the “single polymer having both swelling and gelling properties” alternative.
- For embodiments with separate swelling and gelling polymers, staying outside the ratio range may avoid literal infringement, but nonliteral infringement theories remain.
Species-list narrowing in dependent claims reduces overlap with many generic “hydrogel coat” approaches
Dependent claims 3–7 and 13 define closed lists of plasticizers and specific polymer species. If a competitor swaps plasticizers or uses non-listed excipients, it may avoid literal infringement of those dependent claims while still risking independent claim 1 coverage (depending on construction).
Where do claims 8–10 create distinctive product differentiation?
Thickness and integrity timing create product-specific boundaries:
- 0.5–0.8 mm (claim 8)
- about 1 mm (claim 9)
- support-platform remains intact until complete release (claim 10)
If a competing system uses:
- a different thickness range, or
- a support coat designed to rupture/erode early,
it may fall outside these dependent limitations, while still potentially implicating independent claim 1.
How would US 5,422,123 impact controlled-release tablets in FDA development?
Not about FDA pathway, but about formulation freedom-to-operate
US 5,422,123 is a formulation and method-of-manufacture patent for a controlled-rate release system with specific polymer mechanics. For any controlled-release solid oral dosage intended to:
- use a swelling/gelling core, and
- use an elastic, slowly soluble/gellable partially covering support layer,
the patent can be a barrier for:
- new fixed-dose combinations using the same platform,
- life-cycle modifications adopting the same mechanical protection concept,
- ANDA or 505(b)(2) formulations if the same architecture is used.
What matters for regulatory dossiers
For freedom-to-operate, the most relevant technical mapping is:
- core polymer identity and swelling/gelling ratio
- support-platform polymer identity, plasticizer identity, plasticizer wt%
- support thickness and durability
- evidence the support tracks hydration-induced changes (mechanical behavior)
What is the broader US patent landscape for swelling/gelling controlled-release with elastic coatings?
Claim-type cluster US innovators typically pursue around this architecture
In the US controlled-release ecosystem, adjacent patent estates commonly cover:
- swelling matrix compositions (e.g., crosslinked celluloses, PVP, methacrylate copolymers)
- gel-layer controlled diffusion coatings
- core-in-matrix vs multi-layer tablet designs
- plasticized hydrophilic/hydrophobic blends controlling erosion vs gel barrier
- methods for applying partial coatings by compression or coating/pressing
US 5,422,123 sits in a cluster defined by:
- two-phase polymer behavior (swelling + gelation) in the core and
- mechanically compliant, slow-soluble/slow-gellable barrier on the outside.
Landscape consequences
If competitors maintain:
- a swelling/gelling core polymer system within the ratio band,
- and a slow-gelling/slow-dissolving partially covering elastic support,
they risk direct claim overlap.
If they change:
- the outer layer to a purely brittle or rapidly eroding barrier,
- or use non-listed plasticizers/binders/hydrophilic/hydrophobic agents where relevant,
they may reduce dependent-claim overlap but still face independent-claim risk.
How strong is the patent estate for this technology?
US 5,422,123 is structurally strong because it combines multiple limiting features:
- defined geometry deposit-core,
- specific swelling/gelling polymer logic with ratio bounds,
- elastic, partial support with slow solubility and/or gelability,
- mechanical performance (“follows hydration,” “remains intact until complete release”),
- plus dependent claims with specific excipient lists and quantitative thickness/composition limits.
Strength drivers:
- functional-mechanical limitations can be difficult to replicate without being caught by claim mapping,
- ratio and composition ranges constrain “near-miss” formulation variants.
Vulnerabilities:
- controlled-release excipient technology is crowded; an invalidity defense may try to show the combination is not novel, but that assessment requires the actual prior art record and prosecution history, which are not provided here.
What patent litigation or Orange Book status affects this US patent?
No information is provided here on:
- whether US 5,422,123 appears in the FDA Orange Book for a specific NDA/ANDA,
- whether any Paragraph IV certifications were filed against products covered by this patent,
- or whether there has been enforcement litigation tied to this specific patent number.
Without that case linkage, enforcement timing and generic entry risk cannot be mapped to any particular drug sponsor.
Key takeaways
- US 5,422,123 claim scope centers on a two-part controlled-release system: a swelling/gelling deposit-core plus an elastic, partially covering support-platform that follows hydration and releases via slow solubility and/or gelation.
- The core polymer ratio (1:9 to 9:1) is a recurring limiter and claim 1 also allows a single polymer with both swelling and gelling properties.
- Dependent claims add concrete excipient and performance constraints: specific plasticizer lists, plasticizer wt% (2–15%), support thickness bands (0.5–0.8 mm and about 1 mm), and an integrity requirement until complete release.
- Claim 13 is a highly specific embodiment with expanded species lists for core and support polymers plus a support polymer wt% band (30–90%).
- For freedom-to-operate, formulation mapping must focus on: core polymer identity and ratio, support polymer and plasticizer identity, plasticizer loading, coating thickness, and mechanical behavior during hydration.
FAQs
1) What excipient changes are most likely to avoid dependent-claim coverage for US 5,422,123?
Switching support-platform plasticizers away from the enumerated lists in claims 3 (and the polyethylene glycol vs polyoxyethylene glycols framing across claim 3 vs claim 13), and altering support composition outside the enumerated binder/hydrophilic/hydrophobic options in claims 5–7 can reduce dependent-claim overlap.
2) Does using only a swelling polymer avoid infringement of the swelling:gelling ratio limitations?
Claim 1 still captures embodiments using a single polymer with both swelling and gelling properties, and claim 1 requires at least one member selected from swelling polymer and/or gellable polymer logic with the stated ratio concept. The ratio band becomes critical when using separate swelling and gelling polymers.
3) Is the “elastic support-platform” limitation satisfied by ordinary film coatings?
The claim requires elastic behavior and the ability to follow hydration-induced changes while remaining intact until complete release (claim 10). A brittle or rapidly eroding coating designed not to track core swelling risks falling outside the elastic-functional limitations.
4) How does the support-platform thickness matter legally?
Thickness-dependent limitations in claims 8 and 9 create additional ways to avoid those dependent claims by designing outside those ranges. Independent claim 1 does not specify the thickness numerically, so thickness avoidance alone may not eliminate risk.
5) How is the product scope connected to the manufacturing process in US 5,422,123?
Claim 12 is product-by-process tied to claim 11’s compression and granulation steps for forming the deposit-core and partially covering support-platform. If a competitor uses different manufacturing steps but arrives at the same final architecture, claim 12 may be less direct than claim 1.
References (APA)
- United States Patent 5,422,123, “System for the controlled-rate release of active substance,” claims 1-13.
