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Patent landscape, scope, and claims: |
United States Patent 4,259,315: Scope, Claims, and US Patent Landscape for Microencapsulated Potassium + Hydrophilic Surfactant in Gelatin Capsules
What does US Drug Patent 4,259,315 claim in scope?
US Patent 4,259,315 claims oral potassium delivery using microencapsulated potassium salt packaged in a gelatin capsule, where a hydrophilic surfactant sits external to the microcapsules to improve flowability through a partially obstructed alimentary tract. The claims tie performance to (i) surfactant HLB > 10, (ii) specific surfactant w/w ranges (0.05% to 5%), (iii) microcapsule polymer shell identity (ethyl cellulose) in dependent claims, and (iv) potassium salt identity (potassium chloride) in dependent claims. Claims also extend to methods of treating or preventing potassium deficiency/depletion in humans.
Core claim architecture
The patent’s scope has three nested layers:
-
Composition in a gelatin capsule
- Microencapsulated potassium salt inside the capsule
- Hydrophilic surfactant outside the microcapsules (external)
-
Composition defined by formulation parameters
- Surfactant HLB > 10
- Surfactant weight percent relative to microencapsulated salt (0.05% to 5.0% in general; 0.05% to 1.0% in one dependent claim)
- Microcapsule polymer material = ethyl cellulose (dependent)
- Potassium salt = potassium chloride (dependent)
- Microcapsule composition includes 3% to 50% by weight polymer (claim 5)
-
Method claims
- Administer potassium (in the described non-toxic composition) to humans for treating/preventing potassium deficiency or depletion.
How broad are the independent claims (1, 2, 5, 7, 8) in US claim coverage?
Independent claim breadth is strongest where the patent does not force a specific surfactant chemistry, specific polymer beyond “polymeric material,” or specific microcapsule polymer loading beyond the 3% to 50% range in claim 5.
Independent claim-by-claim scope
Claim 1 (composition):
- A gelatin capsule containing:
- microencapsulated potassium salt
- hydrophilic surfactant external to the microencapsulated salt
Scope drivers:
- Potassium salt identity is not limited in claim 1.
- Polymer shell identity not limited in claim 1 (microencapsulation is required but structure details are not).
Claim 2 (composition):
- A gelatin capsule containing:
- microcapsules with:
- outer polymeric layer
- core of potassium salt
- hydrophilic surfactant external to the microcapsules
Scope drivers:
- Polymer is “polymeric material” (not limited here).
- Potassium salt is the core (not limited here).
Claim 5 (composition for monogastric animals):
- A composition for treating potassium deficiency in monogastric animals:
- gelatin capsule containing:
- controlled-release microencapsulated potassium salt (microcapsules implied)
- hydrophilic surfactant external to microencapsulated salt
- microencapsulated salt contains:
- 3 to 50 wt% polymeric material
- surfactant present:
- 0.05 to 5.0 wt% based on microencapsulated salt
- “sufficient to increase flowability of said microencapsulated salt in a partially obstructed alimentary tract”
Scope drivers:
- Forces controlled-release microencapsulation.
- Forces polymer loading range 3 to 50 wt%.
- Forces animal target class (monogastric animals).
- Requires functional effect tied to flowability in partially obstructed GI tract.
Claim 7 (method for humans):
- Method for treating potassium deficiency or preventing potassium depletion in a human:
- administer effective amount of potassium
- composition is a non-toxic pharmaceutical
- gelatin capsule with:
- microencapsulated potassium salt
- hydrophilic surfactant external to microencapsulated salt
Scope drivers:
- No explicit HLB or wt% in claim 7 (those appear in dependent claim 9).
- Human use narrows infringement more than composition-only claims if a party uses the same formulation for non-human animals.
Claim 8 (method for humans, more specific):
- Method for treating/ preventing potassium depletion in humans:
- composition is gelatin capsule with:
- microcapsules having:
- outer layer of ethyl cellulose
- core of potassium chloride
- hydrophilic surfactant external
Scope drivers:
- Forces ethyl cellulose and potassium chloride.
- Narrows to those formulation identities for method coverage.
What do the dependent claims add (3, 4, 6, 9, 10), and how do they constrain design-arounds?
Dependent claims introduce additional formulation constraints that define tighter “non-avoidance” space.
Dependent claim constraints
| Claim |
Added requirement |
Practical effect on scope |
| 3 |
Surfactant HLB > 10; surfactant 0.05% to 5% w/w |
Limits surfactant selection and dosage; preserves broad polymer/potassium scope unless combined with other dependent claims |
| 4 |
Polymer = ethyl cellulose; potassium salt = potassium chloride |
Locks material pair; strong anchor for product-specific infringement |
| 6 |
Surfactant amount 0.05% to 1% w/w (based on microencapsulated salt) |
Creates narrower “low-dose surfactant” band; may help separate prior art vs. later formulations |
| 9 |
HLB > 10; surfactant 0.05% to 5% (again) |
Aligns method scope with composition parameterization; narrows methods with those specific surfactant selection/dosage |
| 10 |
Polymer = ethyl cellulose; potassium salt = potassium chloride (method defined) |
Locks the method to a specific microcapsule chemistry |
What is the technical “inventive center” tying all claims together?
The claims converge on one technical concept:
- Use of hydrophilic surfactant external to microencapsulated potassium salt in a gelatin capsule to improve flowability through a partially obstructed alimentary tract, enabling controlled-release potassium supplementation.
The formulation is not only “microencapsulated potassium” but microencapsulation plus an external surfactant at defined surfactant HLB and wt%.
Key quantitative constraints that control infringement
- Surfactant loading: 0.05 to 5.0 wt% (claim 3, 5, 9, and indirectly 1/2/7/8 if elements are met)
- Surfactant band (narrower): 0.05 to 1.0 wt% (claim 6)
- HLB threshold: surfactant HLB in excess of 10 (claim 3, 9)
- Polymer loading: 3 to 50 wt% polymeric material in microencapsulated salt (claim 5)
- Specific materials in narrower claims:
- Ethyl cellulose outer polymer layer (claim 4, 8, 10)
- Potassium chloride core salt (claim 4, 8, 10)
How does the claim set map to infringement scenarios (product vs. method)?
Product (composition) coverage
- If a capsule contains microencapsulated potassium salt plus external hydrophilic surfactant, claims 1 and 2 are the broad entry points.
- If formulation also hits HLB > 10 and/or wt% bands, claims 3 and 6/9-type parameters tighten.
- If microcapsules use ethyl cellulose and the salt is potassium chloride, claim 4 offers a high-specificity composition hook.
Method coverage
- Human method claims exist (7 and 8).
- A company selling the same capsule for humans is more exposed under method claims only if its labeling/administration maps to treating potassium deficiency/depletion in humans.
- Claim 7 is broader because it does not explicitly recite HLB or wt% in the method claim itself.
- Claim 8 is narrower due to ethyl cellulose + potassium chloride.
Where is the patent landscape likely to sit around this technology in the US?
A complete US landscape requires file histories, citations, prosecution history, and assignment/timeline data for US 4,259,315 and its forward citations. That information is not provided here, so only a claim-driven landscape map can be derived from the technology described in the claims.
Landscape map based on claim elements (what competitors typically patent around)
Competitors and follow-on filers typically cluster around four “design levers” corresponding to claim limitations:
-
Encapsulation architecture
- Microencapsulated potassium salts with polymeric shells
- “Outer polymer layer + core salt” versus other matrices
- Controlled-release microcapsules vs immediate-release particulates
-
Surfacing/excipient placement
- Surfactant inside microcapsules vs external to microcapsules
- Choice of surfactant class and whether it qualifies as “hydrophilic” and meets HLB > 10
-
Dose and parameter space
- Surfactant amounts outside 0.05 to 5% bands
- Surfactant HLB below or around the “in excess of 10” boundary
- Polymer loading outside 3 to 50 wt% in the microencapsulated salt
-
Salt/polymer specificity
- Potassium chloride versus other potassium salts
- Ethyl cellulose versus alternative polymers (e.g., acrylates, HPMC blends, Eudragit-type materials)
- Capsule format changes (gelatin capsule is required in the claims provided)
Likely US infringement pressure points
- Most exposed segment: Oral controlled-release potassium chloride formulations using ethyl cellulose microcapsules plus an external hydrophilic surfactant at 0.05 to 5% w/w with HLB > 10.
- Next exposed: Any potassium salt (not limited in claim 1/2) if microcapsules exist and an external hydrophilic surfactant is used at 0.05-5% w/w while meeting HLB > 10 (if asserted under claim 3/9).
- Lower exposure: Designs that move surfactant inside microcapsules rather than external, or that reformulate such that surfactant is outside the stated wt%/HLB bands, or polymer loading is outside 3-50 wt%.
How to interpret “controlled-release,” “microencapsulated,” and “external surfactant” in scope
The claim language imposes three interpretive requirements:
- Controlled-release is explicitly required in claim 5 (animal composition) for the microencapsulated potassium salt.
- Microencapsulated and microcapsules require encapsulation but do not define shell thickness or method; polymer “outer layer” is explicit only where stated (claim 2 and especially claim 8).
- External to said microencapsulated salt / microcapsules is a placement limitation.
- Practical implication: a formulation where surfactant is present as a free excipient mixed with microcapsules is squarely in-scope.
- Surfactant incorporated into the microcapsule shell/core would risk arguments that it is no longer “external,” depending on facts and structure.
What does the claim set suggest about product formulation likely marketed under the patent?
While the claims do not name commercial products, they imply the structure below.
Likely capsule architecture (claim-aligned)
- Gelatin capsule shell filled with:
- microcapsules containing potassium salt in a polymer matrix (ethyl cellulose in narrower embodiments)
- external hydrophilic surfactant blended with microcapsules
- Target function:
- improve flowability and reduce obstruction risk for partially obstructed GI tract
- Surfactant choice:
- hydrophilic surfactants with HLB > 10
- Formulation parameterization:
- surfactant at 0.05% to 5% (or 0.05% to 1% in one narrower dependent band)
- microcapsule polymer content at 3% to 50% in claim 5
What are the business implications of this scope for R&D and freedom-to-operate (FTO)?
R&D formulation decision tree (claim-driven)
| Decision point |
Claim impact |
How it changes risk posture |
| Surfactant location |
External is required (claims 1, 2, 5, 7, 8) |
Keeping surfactant external maintains exposure; moving inside microcapsules may reduce exposure |
| Surfactant properties |
HLB > 10 in claims 3 and 9 |
Using surfactants with HLB not meeting “in excess of 10” can reduce alignment with dependent limitations |
| Surfactant dose |
0.05% to 5% (claims 3, 5, 9) and 0.05% to 1% (claim 6) |
Dosing outside the stated ranges can reduce dependent claim alignment |
| Microcapsule polymer |
Ethyl cellulose appears in claims 4, 8, 10 |
Avoiding ethyl cellulose helps on those narrower hooks, but not on claims 1/2 |
| Potassium salt |
Potassium chloride appears in claims 4, 8, 10 |
Using other potassium salts can reduce overlap with those narrower claims |
| Polymer loading |
3 to 50 wt% appears in claim 5 |
Outside that band reduces match for the monogastric animal composition claim |
| Intended use |
Methods are for humans (claims 7, 8); animals in claim 5 |
Indications/labeling and administration affect method-claim exposure |
Key claims table (as provided)
| Claim |
Claim type |
Formulation / method limitations |
| 1 |
Composition |
Gelatin capsule; mixture of microencapsulated potassium salt + hydrophilic surfactant external |
| 2 |
Composition |
Gelatin capsule; microcapsules with outer polymeric layer and core of potassium salt; hydrophilic surfactant external |
| 3 |
Composition (dependent) |
Claim 2; surfactant HLB > 10; 0.05 to 5.0 wt% |
| 4 |
Composition (dependent) |
Claim 3; polymer ethyl cellulose; potassium salt potassium chloride |
| 5 |
Composition (independent; animals) |
Treat potassium deficiency in monogastric animals; gelatin capsule with controlled-release microencapsulated potassium salt + external hydrophilic surfactant; microencapsulated salt has 3 to 50 wt% polymeric material; surfactant 0.05 to 5.0 wt% based on microencapsulated salt sufficient to increase flowability in partially obstructed alimentary tract |
| 6 |
Composition (dependent) |
Claim 5; surfactant 0.05 to 1.0 wt% based on microencapsulated salt |
| 7 |
Method (independent; humans) |
Treat potassium deficiency or prevent potassium depletion in a human; administer effective amount of potassium using non-toxic gelatin capsule formulation with microencapsulated potassium salt + external hydrophilic surfactant |
| 8 |
Method (dependent/independent; humans) |
Claim 7; microcapsules with outer ethyl cellulose and core potassium chloride; hydrophilic surfactant external |
| 9 |
Method (dependent) |
Claim 8/7 depending; surfactant HLB > 10; 0.05 to 5.0 wt% |
| 10 |
Method (dependent) |
Claim 7/8; polymer ethyl cellulose; potassium salt potassium chloride |
Key Takeaways
- US 4,259,315 is centered on external hydrophilic surfactant blended with microencapsulated potassium salt inside a gelatin capsule to improve flowability in partially obstructed GI conditions.
- The claim set combines broad structure elements (capsule + microencapsulated potassium + external surfactant) with tight formulation parameters (surfactant HLB > 10, 0.05 to 5% w/w, polymer loading 3 to 50% wt%).
- The highest-specificity hooks for product replication are ethyl cellulose microcapsules and potassium chloride core (claims 4, 8, 10), plus surfactant HLB and dosing (claims 3, 6, 9).
- Design-around most directly targets (i) surfactant placement (external vs incorporated), (ii) surfactant HLB and wt%, and (iii) polymer and salt identity while also avoiding the controlled-release microencapsulation framing in claim 5.
FAQs
1. Which claim provides the broadest composition coverage?
Claims 1 and 2 because they require a gelatin capsule with microencapsulated potassium salt plus hydrophilic surfactant external, without limiting the polymer type (claim 1) or surfactant HLB and wt% (claims 3 and 9 add those constraints).
2. What is the key quantitative surfactant boundary used to narrow scope?
HLB in excess of 10 and 0.05 to 5.0 wt% hydrophilic surfactant (claims 3 and 9), with a narrower alternative band of 0.05 to 1.0 wt% (claim 6).
3. How does claim 5 differ from claims 1 and 2?
Claim 5 is an animal therapeutic formulation claim that adds controlled-release microencapsulated potassium and a specific polymer loading window (3 to 50 wt% polymer) plus a functional flowability requirement in partially obstructed GI tracts.
4. Are ethyl cellulose and potassium chloride required to infringe?
Not for the broadest composition elements (claims 1 and 2), but they are required for the narrower composition and method hooks in claims 4, 8, and 10.
5. Does the patent cover human treatment only, or also animals?
It covers both: claim 5 is for monogastric animals, and claims 7 and 8 are methods for treating/preventing potassium depletion in humans.
References
[1] United States Patent 4,259,315, “Pharmaceutical composition for treating potassium deficiency,” claims 1-10 (as provided).
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