US Patent 12,558,328: Scope, Claims, and US Patent Landscape for Solid-Forming Local Anesthetic Film
US Drug Patent 12,558,328 claims a method for applying and removing a solid-forming topical local anesthetic film that transitions from a semi-solid layer to a cohesive peelable film on skin. The claim set narrows to a specific compositional envelope (notably PVA polymer, dicalcium phosphate filler, and defined water:PVA ratio), specific anesthetic combinations (notably lidocaine + tetracaine, with base forms and eutectic ratios), and performance/procedure constraints (time on skin and peel-off as single piece or 2 to 3 large pieces).
What is the claimed invention’s technical scope (method and material constraints)?
Core method claim (Claim 1)
Claim 1 defines a stepwise process tied to a specific film-forming formulation:
- Apply a layer of a “solid-forming local anesthetic formulation” to skin.
- The formulation includes (by weight ranges):
- Local anesthetic: 4 wt% to 30 wt%
- Filler: 18 wt% to 36 wt% (dicalcium phosphate)
- An emollient
- An emulsifying agent
- Water
- Polymer: polyvinyl alcohol (PVA)
- The formulation further requires a specific water:PVA ratio:
- Water to PVA about 2.16 to about 3.16
- Maintain on skin until:
- the layer transitions from semi-solid to cohesive film, and
- delivers the local anesthetic to the skin surface.
- Remove by peeling:
- peel as a single piece or two to three large pieces.
Claim 1 is a composition-plus-process method claim: scope is limited both by the formulation recipe and the film-forming/removal mechanics.
Claim 2: Film has no backing/support substrate
Claim 2 limits the cohesive film to be free of a backing layer, backing film, or other support substrates. This narrows the field against “wearable patches” that rely on a backing sheet.
Claims 3 to 7: Water:PVA ratio and water content thresholds
- Claim 3: formulation includes > 25.94 wt% water
- Claim 6: water:PVA > 2.4
- Claim 7: water:PVA > 2.5
These claims create narrower sub-ranges within Claim 1’s “about 2.16 to about 3.16” envelope.
Claims 4 and 5: PVA molecular weight window
- Claim 4: PVA average mass 20,000 to 100,000 Daltons
- Claim 5: PVA molecular mass 30,000 to 80,000 Daltons
These claims constrain PVA selection by chain-length distribution.
Claims 8 to 11: Local anesthetic pairing and eutectic ratios
- Claim 8: local anesthetic comprises lidocaine and tetracaine
- Claim 9: lidocaine and tetracaine are each in base form
- Claim 10: eutectic mixture about 2:1 to 1:2 (weight ratio)
- Claim 11: eutectic mixture about 1:1 (weight ratio)
This set tightens scope around the specific chemical identity and phase behavior of the anesthetic component.
Claims 12 to 16: Filler level, application thickness, and dwell time
- Claim 12: dicalcium phosphate present 18 to 32.4 wt%
- Claim 13: application thickness 1 mm or more
- Claim 14: dwell time at least 20 minutes
- Claim 15: dwell time at least 30 minutes
- Claim 16: dwell time at least 45 minutes
These are straightforward operational limits that strongly affect infringement analysis because “thickness” and “time-on-skin” are directly measurable.
Claims 17 to 21: Performance and component exemplars
- Claim 17: method is for local anesthesia
- Claim 18: emollient is petrolatum
- Claim 19: emulsifying agent is sorbitan ester
- Claim 20: emollient petrolatum and emulsifying agent sorbitan ester
- Claim 21: initial viscosity 40,000 to 800,000 cP
How do the dependent claims narrow the scope relative to Claim 1?
The claim set works like a stack of gating elements:
- Composition gate (broad) in Claim 1:
- PVA is required
- dicalcium phosphate filler is required
- water:PVA ratio must be within 2.16–3.16
- anesthetic content 4–30 wt%
- Structural gate via Claim 2:
- film must be backing-free
- Formulation envelope tightening via Claims 3, 6, 7:
- water content and water:PVA ratios move to higher thresholds
- Polymer selection gate via Claims 4 and 5:
- PVA molecular weight window
- Anesthetic identity/solid state gate via Claims 8 to 11:
- lidocaine + tetracaine in base forms with eutectic ratios
- Processing gate via Claims 13 to 16:
- thickness >= 1 mm
- dwell >= 20/30/45 minutes
- Recipe exemplars via Claims 18 to 20:
- petrolatum + sorbitan ester
- Rheology gate via Claim 21:
- initial viscosity within a specific cP range
Net effect: a design-around typically must break at least one of these gates, most efficiently by altering (i) the polymer system, (ii) filler choice, (iii) water:PVA ratio, (iv) presence/absence of backing substrates, (v) peelable film formation characteristics, or (vi) time/thickness and anesthetic identity/phase.
What is the likely claim coverage boundary for “solid-forming topical film” on skin?
Explicit boundary markers
The claims explicitly demand:
- a layer applied to skin
- transition to a cohesive film (not merely a dry patch)
- peeling off as single or 2–3 large pieces
- no backing layer/support substrate
These markers collectively aim at “in situ film formation” rather than preformed sheet materials, and they prioritize removable film behavior instead of cutting, washing off, or wiping.
Practical infringement implications
- If a product uses a backing film (for example, a plasticized polymer sheet, nonwoven, or web), it can fall outside Claim 2.
- If anesthetic use excludes lidocaine + tetracaine, Claims 8–11 do not apply; only Claim 1 remains available, and that still requires PVA + dicalcium phosphate + specified ratios and peel mechanics.
How should the claims be read for design-around strategy (what changes likely avoid coverage)?
Based on the claim language, the highest-leverage design changes are the elements that are both required (Claim 1) and quantified:
Highest leverage (touch Claim 1 required elements)
- Change polymer away from PVA
- Claim 1 requires PVA specifically.
- Substituting a different film-former (e.g., HPMC, PVP, pullulan systems, or cellulose derivatives) would avoid the literal scope of Claim 1.
- Change filler away from dicalcium phosphate
- Claim 1 requires the filler be dicalcium phosphate in 18–36 wt%.
- Move water:PVA ratio outside 2.16–3.16
- Claims 6 and 7 further enforce higher thresholds, but Claim 1 already sets the primary window.
- Break peelable “single piece or 2–3 large pieces” removal
- Even if the formulation gels, failure to peel as a piece or failure to produce the specified piece geometry can undercut method coverage.
- Break “no backing/support substrate”
- This directly hits Claim 2, but not Claim 1 if the product still has required formulation and peel behavior.
Medium leverage (dependent claims only)
- Switch anesthetic system away from lidocaine + tetracaine base eutectic:
- Adjust dwell time or thickness below asserted thresholds:
- Change specific emollient/emulsifier choices:
- affects Claims 18–20 only
- Adjust initial viscosity:
What is the patent landscape relevance for this claim theme?
US Drug Patent 12,558,328 sits in the niche of:
- topical local anesthetic delivery
- with film-forming polymer matrix
- peelable, backing-free “solid-forming” application on skin
- using PVA and dicalcium phosphate as the filler system
Within US practice, this theme typically clusters around:
- topical anesthetic dosage forms (gels, creams, patches)
- polymer film-forming technologies
- and “patch-free” or “in situ forming” transdermal/topical systems.
However, with the information provided, only the claims are available; no prosecution history, assignee, family members, examiner record, citation list, or related US/WO publications are included in the prompt. A complete, verifiable landscape comparison (e.g., specific US application numbers, priority dates, and claim-chart-level overlap against cited art) cannot be produced from the claim text alone.
US patent landscape mapping: where overlap risk concentrates
Even without listing specific neighboring patents, the overlap risk concentrates around claim elements that are both:
- technically common in film-forming topical systems, and
- explicitly constrained here by quantitative windows.
Overlap risk matrix
| Claim element |
Why it drives overlap |
Typical neighboring art pattern |
| PVA film-forming |
PVA is widely used in topical and transdermal film systems |
Overlap likely if PVA is retained |
| Dicalcium phosphate filler |
Less common than generic fillers; specific filler choice is a discriminator |
Overlap lower unless dicalcium phosphate is also used |
| Water:PVA ratio |
Constrains viscosity, gelation, and film cohesion |
Many formulations will miss the narrow ratio |
| Backing-free film |
Limits against preformed patch architectures |
Overlap lower where backing is used |
| Peel-off removal geometry |
Narrows user interface mechanics |
Fewer documents explicitly define peel piece number |
| Lidocaine + tetracaine eutectic |
Specific anesthetic pairing and phase behavior is narrower |
Overlap depends on eutectic formulation claims |
| Thickness and dwell time |
Operationally measurable; easy to undercut |
Many products avoid long dwell windows |
Key Takeaways
- US 12,558,328 claims a method requiring PVA + dicalcium phosphate + defined water:PVA ratio in a solid-forming topical local anesthetic that transitions to a cohesive, peelable film on skin.
- Claim 1 sets the base coverage boundary; Claim 2 adds a backing-free limitation; Claims 3–7 tighten water content and water:PVA ratios; Claims 4–5 constrain PVA molecular weight.
- Claims 8–11 narrow to lidocaine and tetracaine in base form as a weight-ratio eutectic.
- Claims 12–16 narrow by dicalcium phosphate amount, application thickness (>=1 mm), and dwell time (>=20/30/45 minutes).
- Claims 18–20 narrow to petrolatum (emollient) and sorbitan ester (emulsifying agent); Claim 21 narrows by initial viscosity (40,000 to 800,000 cP).
- Design-around pressure points are the required Claim 1 elements: polymer identity (PVA), filler (dicalcium phosphate), water:PVA ratio, and peel-off as specified pieces.
FAQs
1) Does US 12,558,328 protect a topical composition or a method?
It protects a method of applying the solid-forming local anesthetic formulation and peeling off the resulting cohesive film.
2) What is the minimum formulation dwell time covered by the dependent claims?
At least 20 minutes (Claim 14), with additional dependent thresholds at 30 minutes (Claim 15) and 45 minutes (Claim 16).
3) Must the film be backing-free?
Yes for Claim 2: the cohesive film is free of backing layer/film/support substrates.
4) Is PVA required?
Yes. Claim 1 requires the polymer to be polyvinyl alcohol (PVA) and specifies water:PVA ratio; dependent claims further specify PVA molecular weight ranges.
5) Which anesthetics are explicitly covered in the dependent claims?
Claims 8–11 specify lidocaine and tetracaine, each in base form, as a eutectic mixture at defined weight ratios.
References
[1] US Patent 12,558,328 (claims provided in prompt).
