United States Patent 4,870,105: Scope, Claims, and US Landscape for Calcium Acetate to Inhibit Phosphate Absorption

What does US 4,870,105 claim, and what is the practical scope?

US Patent 4,870,105 claims an oral dosing method using calcium acetate to inhibit gastrointestinal absorption of phosphorous (phosphate) in an individual. The claim set is a tight, method-of-treatment scope: it does not claim a formulation beyond dosing vehicle (tablet vs. gelatin capsule) and does not claim specific patient populations, kidney stages, disease labels, or administration duration.

The independent claim concept appears in claim 1 and is repeated in claim 5 with “at mealtimes” as the key scheduling limitation. Dependent claims add (i) a dosing range framed as milliequivalents (mEq) of calcium and (ii) solid oral form as tablet or gelatin capsule.

Claim-by-claim scope map (as provided)

Claim	Core limitation(s)	What the claim covers	What it does not cover
1	Orally ingest quantity of calcium acetate sufficient to bind phosphate in GI tract	Any oral dosing regimen where calcium acetate is ingested in an amount that binds phosphate in the gut	No requirement for mealtime dosing; no required dose interval; no patient/disease definition
2	Calcium acetate provides 10 to 200 mEq calcium	Dose-amount constrained method; range covers low to high calcium delivered as “mEq” equivalent	No further limitation on mg calcium, number of tablets/capsules, or exact schedule
3	Tablet form	Tablet products using calcium acetate in the claimed functional/dose range	Non-tablet forms (e.g., liquid suspensions)
4	Gelatin capsule form	Gelatin capsule products in claimed range	Non-capsule vehicles
5	Orally ingest calcium acetate at mealtimes	Meal-timed calcium acetate phosphate binding	Non-mealtime dosing
6	Dose provides 10 to 200 mEq calcium at mealtimes	Meal-time dosing constrained by calcium-equivalent range	Doses outside range or different calcium equivalent mapping
7	Tablet form	Tablets dosed at mealtimes in claimed range	Non-tablet forms
8	Gelatin capsule form	Gelatin capsule dosed at mealtimes in claimed range	Non-capsule forms

Functional claim center: “bind with phosphorous in the gastrointestinal tract”

The “sufficient to bind” functional language drives scope beyond fixed mg amounts. Even where dependent claims impose a numeric range, the independent claims still hinge on achieving phosphate binding in the GI tract. That typically captures calcium acetate products that deliver bioavailable calcium ions in the GI environment to complex dietary phosphate.

How broad is “calcium acetate,” and how limiting are the dose and timing terms?

1) Active ingredient and “chemical identity” boundary

The claims require calcium acetate as the ingested compound. That is a hard boundary. Substituting another calcium salt (e.g., calcium carbonate) or other phosphate binders (sevelamer, lanthanum carbonate, ferric-based binders) is outside the literal scope because the claim language is specific.

However, if an alternative product is chemically calcium acetate (or a salt/hydrate that is treated as calcium acetate in practice), it may still map. The claim set does not say “anhydrous” or “specific hydrate.”

2) Dose boundary: “between 10 to 200 milliequivalents of calcium”

The dose range is expressed as mEq calcium, not mg calcium or mg calcium acetate. That matters for infringement analysis because product labels and prescriber instructions often state mg per tablet/capsule, not mEq.

Operationally, the dose range creates a measurable infringement trigger:

Claim coverage for a given ingestion event depends on whether the total ingested dose equates to 10 to 200 mEq of calcium.
The method is “quantity sufficient to bind,” but dependent claims explicitly lock the equivalent calcium range.

3) Timing boundary: “at mealtimes”

Only claims 5 to 8 require meal-time dosing. That creates two layers:

If a product is used before/after meals rather than “at mealtimes,” it may avoid claims 5-8 while still potentially implicating claims 1-4.
If it is administered with meals (typical practice for phosphate binders), it tends to fall within claims 5-8.

4) Vehicle boundary: tablet vs. gelatin capsule

Claims 3-4 and 7-8 limit the dosage form to tablet or gelatin capsule.

A liquid formulation used to deliver calcium acetate would not literally meet these vehicle-dependent claims, though it could still fall within claims 1-2 and 5-6 (since those do not restrict form).

What is the infringement logic if someone commercializes a calcium acetate phosphate binder?

The claim structure suggests infringement exposure is driven by prescribing and use instructions as well as actual use patterns.

Likely literal mapping patterns

Meal-time calcium acetate tablets delivering calcium in the range 10-200 mEq are in the strongest position to read on claims 5-7 (meal-time + tablet + dose range).
Meal-time calcium acetate gelatin capsules delivering 10-200 mEq map to claims 5-6 and 5-8 (meal-time + capsule + dose range).
Non-meal-time calcium acetate in the same dose range still maps to claims 1-2 (and potentially 1-3/4 depending on form) if the functional “bind phosphate in GI tract” requirement is met.

Key design-around levers implied by the claims

Because claim language is restrictive, design-arounds typically target one of these elements:

Not using calcium acetate as the active calcium source.
Using calcium acetate in a regimen that does not deliver 10-200 mEq calcium per dosing event.
Avoiding meal-time dosing (for claims 5-8) or avoiding tablet/capsule (for form-dependent claims).

How does this patent sit within the broader US phosphate-binder landscape?

Market context the claims align with

US 4,870,105 is directed to a classic approach for chronic hyperphosphatemia management: oral calcium-based phosphate binding. In the US market, calcium acetate appears alongside other phosphate binders. While the claim set is narrow to calcium acetate dosing methods, the landscape competition usually includes:

Other calcium salts (e.g., calcium carbonate) that compete on phosphate-binding functionality but do not match the “calcium acetate” identity requirement.
Non-calcium phosphate binders (e.g., polymeric binders, metal-based binders) that differ by chemical class and lack claim identity.

Landscape impact: what this patent is and is not protecting

This patent is protecting a method: “orally ingesting calcium acetate” with sufficient dosing to bind phosphate.
It is not protecting a device, diagnostic method, or disease-specific regimen beyond what is embedded in timing (“at mealtimes”) and dose equivalence (“mEq calcium”).

That positioning affects freedom-to-operate:

If another calcium salt is used, this patent may not be the gating concern for literal infringement.
If calcium acetate is used, the key risk becomes whether dosing instructions fall into the claimed dose range and schedule and whether the dosage form is tablet/capsule for dependent claims.

Scope boundaries that affect claim interpretation in practice

1) “Phosphorous” vs “phosphorus/phosphate”

Claims use “phosphorous.” Practically, phosphate binding methods target dietary phosphate. In infringement analysis, courts often interpret based on the substance intended in the method. The claim language also uses “bind with phosphorous in the gastrointestinal tract,” consistent with phosphate binding in GI.

2) “Inhibiting gastrointestinal absorption”

The method requires an effect: inhibiting absorption by binding in GI. That still typically maps to phosphate binders used with meals. It is not a systemic pharmacokinetic claim; it is tied to GI binding and functional inhibition.

3) “Quantity sufficient”

For claims 1 and 5, the “quantity sufficient” wording is open-ended. Dependent claims 2 and 6 narrow by numeric mEq range. This is the typical structure: broad independent + narrower dependent.

What is known from the information provided about claim scope vs. typical product instructions?

The claims are compatible with standard phosphate-binder use patterns:

Oral administration with meals is reflected in claims 5-8.
Dose range “10-200 mEq calcium” is consistent with dosing adjustments in calcium-based binders, where the number of tablets/capsules is titrated to achieve phosphate control.
Tablets and gelatin capsules cover common commercial dosage forms.

US patent landscape implications for developers and investors

If you are evaluating calcium acetate product IP risk

Literal risk concentrates on calcium acetate and on whether dosing instructions and actual use deliver calcium within 10-200 mEq and, for half the claim set, are at mealtimes.
Dependent claims add product-shape constraints (tablet, gelatin capsule). If your product is calcium acetate in another format, claims 1-2 and 5-6 remain the primary focus.

If you are evaluating competing chemistry (non-acetate binders)

Claims do not read on other phosphate binder actives unless they are calcium acetate (or are effectively equivalent in claim construction, which the language does not suggest).
Chemical identity is a key fence for this patent.

Key Takeaways

US 4,870,105 protects a calcium acetate phosphate-binding method: oral ingestion to inhibit GI absorption of phosphorous/phosphate by GI binding.
The patent is method-only, not a device or diagnostic claim; scope centers on active identity (calcium acetate) plus functional GI phosphate binding.
Dose constraint appears in dependent claims: calcium acetate providing 10 to 200 mEq calcium.
Meal-time timing is a claim limiter: claims 5-8 require dosing at mealtimes.
Dosage form is limited in dependent claims: tablet and gelatin capsule.

FAQs

1) Does US 4,870,105 claim a specific patient population or disease stage?

No. Based on the claim text provided, it is framed as a method for “an individual” without kidney stage or diagnosis limitations.

2) Are the claims limited to tablets only?

No. Tablet and gelatin capsule are specified only in dependent claims (3-4 and 7-8). Independent claim coverage (1 and 5) is not limited by dosage form in the text provided.

3) How critical is the “10 to 200 mEq calcium” range?

It is critical for dependent claim coverage (2 and 6) and forms a measurable dosing boundary for infringement analysis. The independent claims still require a “quantity sufficient” to bind phosphate.

4) If dosing is not at mealtimes, is the patent avoided?

It may avoid claims requiring mealtime dosing (5-8), but it does not eliminate potential exposure to claims 1-4, which do not require mealtime scheduling.

5) Can alternative calcium salts be used to avoid literal scope?

Based on the “calcium acetate” identity requirement in the claims, substituting other calcium salts is outside literal coverage, unless the substituted product is calcium acetate in substance.

References

United States Patent 4,870,105. (Claims provided by user).

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Details for Patent: 4,870,105

Summary for Patent: 4,870,105