Scope and Claim Analysis of US Patent 8,992,952 (Topical Ophthalmic Ketorolac with Mixed-Grade Carboxymethyl Cellulose, pH 6–8)
US 8,992,952 is directed to a specific topical ophthalmic ketorolac formulation defined by (i) ketorolac concentration, (ii) a binary carboxymethyl cellulose system that combines “medium molecular weight” and “high molecular weight” grades in a defined total level and weight ratio, and (iii) an ophthalmically acceptable buffered aqueous vehicle with tightly bounded pH (about 6 to about 8) plus electrolyte and acid/base system details. The enforceable claim core is the mixed-grade carboxymethyl cellulose mixture plus the ketorolac/pH/buffer framework. Generic or “equivalent” products that keep ketorolac and pH but substitute a single viscosity grade CMC, change the ratio or total CMC concentration outside the stated ranges, or remove/change key vehicle elements are the most vulnerable design-around targets.
What does US 8,992,952 claim protect for ophthalmic ketorolac?
Featured snippet answer: The patent protects a topical ophthalmic aqueous solution containing ketorolac (or salt) at 0.01%–1.0% w/v combined with a two-grade carboxymethyl cellulose mixture (0.1%–2.0% w/v total; medium:high weight ratio 0.25–4), buffered to pH about 6–8 using sodium chloride and acid/base (NaOH/HCl, including optional 1N), with specific optional dependencies for salt identity, preservative selection, and target pH (about 6.8).
Claim 1 is the independent “composition” backbone
Claim 1 defines the “consisting of” mixture for a topical ophthalmic solution:
- Active: ketorolac or pharmaceutically acceptable salt, 0.01% to 1.0% w/v
- Mucoadhesive/viscosity polymer system: a mixture of
- medium molecular weight CMC and high molecular weight CMC
- total CMC: 0.1% w/v to 2.0% w/v
- weight ratio (medium:high): 0.25 to 4
- pH adjustment: sodium hydroxide and hydrochloric acid to adjust pH
- Electrolyte: sodium chloride
- Buffer: present (buffer type is not specified in claim 1)
- pH window: about 6 to about 8
Two points matter for scope:
- The polymer is not generic “CMC.” It is explicitly a binary system with medium + high molecular weight components and a ratio constraint.
- The vehicle is not only “aqueous buffered ketorolac.” It is bounded to an ophthalmic pH window (6–8) and includes sodium chloride plus NaOH/HCl for pH adjustment.
Claims 2–10 are dependency layers that narrow identity details
- Claim 2: medium and high MW CMC are both sodium carboxymethyl cellulose (CMC-Na).
- Claim 4 & 8: ketorolac is ketorolac tromethamine.
- Claim 5 & 9: NaOH/HCl are 1N.
- Claim 6 & 10: pH is about 6.8 (single point target).
- Claim 3: adds a preservative (buffer remains and pH remains within about 6–8).
- Claim 7: preservative is benzalkonium chloride or chlorine dioxide.
The dependent structure means that Claim 1 is the broadest composition; Claims 2, 4, 5, 6 narrow to specific reagent identities and numeric settings; Claims 3 and 7 narrow further around preservative choice.
What are the practical elements of claim scope that drive infringement risk?
1) “Consisting of” language constrains allowable substitutions
Each independent claim is written as: “A topical ophthalmic solution consisting of …” That formulation language typically functions to restrict the composition to the recited components and excludes other ingredients unless they are trace/immaterial or fall within what the patentee treats as within the scope of “consisting of.” In practice, this boosts the value of proving “all elements” rather than arguing broad equivalency.
2) The binary medium/high CMC mixture is the central differentiator
The patent requires:
- both medium MW CMC and high MW CMC
- total CMC in 0.1%–2.0% w/v
- medium:high weight ratio 0.25–4
Design-around pressure points:
- Use only one CMC grade (medium-only or high-only).
- Use a binary blend but shift the ratio outside 0.25–4.
- Keep total CMC in-range but adjust ratio; or keep ratio in-range but move total out of 0.1–2.0%.
- Use a different polymer system (even if it provides similar viscosity), because claim language is polymer-specific (carboxymethyl cellulose grades).
3) pH is bounded, and claim 6/10 lock a target pH
Claim 1 requires pH about 6–8. Dependent claims require about 6.8.
Design-around pressure point:
- Set pH outside “about 6–8” (or outside “about 6.8”) while maintaining acceptable ophthalmic tolerability. This can be difficult commercially because ketorolac and buffers have solubility and stability constraints, but the claim language makes pH a literal lever.
4) Preservative and acid/base identity are only in dependent claims
If a product avoids the specific preservatives named in Claim 7, it may still infringe Claim 1 if it satisfies all other limitations, because Claim 1 does not require a preservative.
Conversely, if a product includes preservatives but uses different ones, it can remain within Claim 3/7 only if the preservative matches.
5) Ketorolac identity matters only for dependent claims
Claim 4/8 require ketorolac tromethamine. Claim 1 covers ketorolac or salts generically. A product using ketorolac tromethamine is inside Claim 4/8.
How broad is the numeric coverage for the formulation parameters?
Below is the numeric “claim map” derived directly from the asserted claim set you provided.
Claim 1 numeric constraints (core)
| Parameter |
Scope in claim 1 |
| Ketorolac concentration |
0.01% to 1.0% w/v |
| CMC total (medium + high) |
0.1% to 2.0% w/v |
| Medium:high CMC weight ratio |
0.25 to 4 |
| pH |
about 6 to about 8 |
| CMC type |
medium MW + high MW (both are carboxymethyl cellulose grades) |
| Acid/base |
sodium hydroxide and hydrochloric acid (to adjust pH) |
| Electrolyte |
sodium chloride |
| Buffer |
present (type not specified) |
Dependent claim “tighteners”
| Dependent claim |
Added limitation |
| Claim 2 |
each of medium and high MW CMC is sodium carboxymethyl cellulose |
| Claim 3 |
preservative is present |
| Claim 4 / 8 |
ketorolac is ketorolac tromethamine |
| Claim 5 / 9 |
NaOH and HCl are 1N |
| Claim 6 / 10 |
pH about 6.8 |
| Claim 7 |
preservative selected from benzalkonium chloride and chlorine dioxide |
What is the patent landscape around these formulation features in the US?
US 8,992,952 is best understood as a formulation-combination patent. The claim does not seek a new active ingredient; it seeks a particular ophthalmic aqueous vehicle design that uses:
- ketorolac
- buffered near-neutral pH
- sodium chloride
- specific mixed-grade CMC system by molecular weight category and ratio
In a US infringement and freedom-to-operate analysis, that structure typically means:
- Active ingredient patents are usually earlier and expire well before.
- Single-polymer CMC solutions and single-grade CMC compositions may exist in earlier art (or later) and can be used for novelty/obviousness arguments depending on the patent’s prosecution history.
- Binary CMC grade blends plus a ratio constraint are where the novelty often resides. If the prior art teaches mixed CMC grades without the claimed ratio and total concentration boundaries, it is weaker against novelty and more likely to be used in obviousness combinations.
- pH 6–8 buffering is common in ophthalmic liquid formulations, so the strongest differentiators are usually the combination of (i) CMC-grade mixing by molecular weight, (ii) the numeric ratio, and (iii) the defined ketorolac concentration band.
What jurisdictions does this US patent cover?
Only the United States via its US patent rights. In the absence of an accompanying EP/WO family disclosure in your prompt, the landscape discussion is limited to claim scope analysis for US 8,992,952.
How many separate claim “tracks” exist within US 8,992,952?
Even though the claims look similar, they form multiple infringement tracks:
- Track A (Claim 1): core formulation with no requirement for preservative.
- Track B (Claims 3 + 7): Track A plus presence of preservative; preservative limited in Claim 7.
- Track C (Claim 2): Track A but constrains medium/high CMC to sodium carboxymethyl cellulose.
- Track D (Claims 4/8, 5/9, 6/10): Track A with specific ketorolac form and optional pH and acid/base identity.
A competitor product that hits the CMC mixture + pH + ketorolac concentration can fall within Claim 1 even if it diverges on preservative choice, preservative omission, or NaOH/HCl concentration, unless those changes also affect the ability to meet pH/CMC limitations.
What are the most relevant technical design-around strategies (US claim language driven)?
Strategy 1: Change the medium:high CMC ratio outside 0.25–4
Because the ratio is an explicit claim element, shifting the medium/high ratio outside the stated bounds is a clean literal design-around.
Strategy 2: Move total CMC outside 0.1%–2.0% w/v
Total CMC is explicitly bounded. Changing total CMC concentration is also direct.
Strategy 3: Replace the binary CMC system with a single CMC grade or non-CMC thickener
Claim 1 requires “a mixture of medium molecular weight and high molecular weight carboxymethyl cellulose.” A single grade violates the “mixture” requirement.
Strategy 4: Adjust pH outside about 6–8 or avoid about 6.8
pH is a hard numeric element (with “about” flexibility). Setting pH outside the window avoids Claim 1; setting it away from 6.8 avoids Claim 6/10.
Strategy 5: If seeking to avoid Claims 3/7, select a preservative outside the named group
If a product uses benzalkonium chloride or chlorine dioxide, it may fall under Claim 7 if other limitations are met. Using a different preservative can avoid Claim 7, but not Claim 1.
Key Takeaways
- US 8,992,952 claims a topical ophthalmic aqueous ketorolac formulation where the enforceable novelty is anchored to a binary medium/high molecular weight carboxymethyl cellulose mixture with total CMC 0.1%–2.0% w/v and medium:high ratio 0.25–4, plus buffered pH about 6–8 and sodium chloride.
- Claim 1 is broad with respect to preservative. Dependent claims narrow preservative identity, ketorolac form (tromethamine), acid/base concentration (1N), and a specific pH target (about 6.8).
- The cleanest literal design-arounds are to shift CMC ratio, shift total CMC, replace the binary CMC system, or change pH outside the claim window.
FAQs
1) Does US 8,992,952 require a preservative to infringe?
No. Preservative is only required in Claim 3; Claim 1 is preservative-free in its recitation.
2) Can a product with ketorolac and a pH of ~7 avoid infringement by using a single CMC grade?
It is the most straightforward avoidance lever because Claim 1 requires a mixture of medium and high molecular weight carboxymethyl cellulose with a defined ratio.
3) What is the key numeric element besides ketorolac concentration?
The medium:high CMC weight ratio (0.25–4) and the total CMC concentration (0.1%–2.0% w/v).
4) If the formulation uses benzalkonium chloride, is it automatically within the patent?
No. It must also meet the CMC mixture, ratio, total concentration, ketorolac concentration, and pH constraints of the applicable claim(s).
5) Which dependent claim fixes the pH to a specific value?
Claim 6 (and Claim 10 mirror) fixes pH to about 6.8.
References (APA)
No sources were cited because the prompt provided only the claim text and a patent number, without prosecution history, specification, examiner notes, family members, or Orange Book/FDA listing records.
