Scope and claims of US Patent 6,528,086: evaporation-triggered, peelable local-anesthetic delivery with controlled, rate-limited dosing

US 6,528,086 is a US utility patent that claims a method and related composition for anesthetizing a human skin surface using (1) a liquid formulation containing a local anesthetic plus an evaporable-solvent vehicle and (2) a “conversion agent” that transforms the formulation into a peelable, coherent solid phase after application, with the anesthetic “delivery” rate controlled by solvent evaporation time and with delivery substantially stopping when evaporation and conversion complete. The claim set is drafted broadly across trigger mechanisms (passive/active), conversion agents (PVA, boron-borate systems, carrageenan, cellulose derivatives, Pluronic F127 and other polymers), and local anesthetic actives (tetracaine, lidocaine), and it spans both method claims and at least one formulation claim (paste-to-solid conversion).

What is US Patent 6,528,086 actually claiming: the core inventive concept?

Featured snippet answer: The patent claims a topical anesthetic formulation and method where local anesthetic release is temporally governed by evaporation of a solvent, while a conversion agent changes the formulation from a liquid/paste phase into a peelable, coherent solid phase; anesthetization is achieved during evaporation and dosing substantially stops upon completion of evaporation/conversion.

The “conversion + evaporation + controlled release + peelable solid” architecture

Across independent claim family members (notably claim 1, claim 51, claim 66, and claim 72), the shared technical steps and structural elements are:

Apply formulation to a human body surface (skin)
Formulation contains:
- a local anesthetic
- a conversion agent facilitating transformation from initial liquid phase to a peelable coherent solid phase
- a vehicle medium comprising an evaporable solvent (commonly water)
Conversion occurs after application via evaporation of the evaporable solvent
Delivery of local anesthetic is rate-controlled by controlling:
- evaporation time and
- conversion into peelable coherent solid phase
Temporal delivery limit: anesthetic delivery continues until substantial evaporation/conversion completes and/or delivery substantially stops upon completion of evaporation
Optional peel step: peel the solid after conversion

The delivery-rate “finishing condition”

Multiple dependent claims recite explicit timing and endpoint behavior:

Delivery is completed upon substantial evaporation of solvent and conversion to coherent solid.
Delivery substantially terminates upon completion of conversion (claim 49).
Delivery prevents over dosing (claim 50).
Target conversion windows:
- Conversion within about 30 minutes with complete anesthetization (claims 5 and 56)
- Conversion within about 60 minutes with complete anesthetization (claims 6 and 57)

“Liquid phase vs solid phase” nuance

The independent claim language ties release to the period during evaporation. Some claims also specify that local anesthetic is delivered at sufficient rates during evaporation and in some dependent formulations that release continues until substantial evaporation occurs.

What is the claim scope on local anesthetic actives and skin target?

Which local anesthetics are explicitly recited?

The claim set contains explicit examples/subclasses:

Tetracaine: claims 2, 53, 70
Lidocaine: claims 52, 71

No other actives are expressly named in the claim text you provided, but the independent claims use “local anesthetic” generically.

Does the patent limit the anatomical target?

Several dependent claims specify:

Human body surface is skin (claim 4, 55)

The independent claims use “human body surface” more generally, but the dependent limitations anchor the main commercial intent to transdermal topical anesthetization.

What is the conversion agent scope: polymers, borate/boric acid, thermally reversible gels, and others?

Featured snippet answer: The conversion agent is broadly defined as any substance that transforms a liquid (or paste) formulation into a peelable coherent solid phase after application, with extensive dependent coverage for PVA, borate/boric acid (and boron salts), carrageenan, cellulose derivatives, Pluronic F127, and thermally reversible gel polymers.

Conversion agent chemical classes covered

Polyvinyl alcohol (PVA)
- claim 8, 67, 81, 82, 83, 84, 85
Boron/borylation conversion agents
- sodium borate (claim 11, 18, 23)
- boric acid (claim 12, 18, 19)
- salts of boric acid (claim 13, 19)
- “compound containing boron” (claim 14, 20)
- “compound comprising calcium” appears as a dependent (claim 21), suggesting another ionic crosslink/coacervation system
Carrageenan and other polysaccharides
- carrageenan (claim 15, 62)
- gellan gum (claim 16, 63)
Cellulose derivatives
- polyvinyl pyrrolidone (claim 16, 63)
- sodium carboxymethyl cellulose (claim 16, 63)
- hydroxyethyl cellulose (claim 16, 63)
- hydroxypropyl cellulose (claim 16, 63)
- “other cellulose derivatives” (claim 16, 63)
Thermally reversible gel polymers
- thermally reversible gel polymer (claim 9)
- Pluronic F127 (claim 10, 61)
- thermal gel becoming more solid between 20°C to 37°C (claim 22, 65)

Triggering conversion: passive vs active transformation

Claims 24-32 and 33-42 carve out conversion trigger pathways:

Passive triggered transformation (change in environment or exposure)

change in water content (claim 26)
exposure to body surface temperature (claim 27)
exposure to air (claim 28)
exposure to light (claim 29)
removing from storage environment to allow conversion (claim 30)
ambient environmental conditions (claim 31)
- exposure to various electromagnetic wavelengths (claim 32)

Active triggered transformation (manipulate ambient environment or formulation chemistry)

changing ambient environment (claim 34)
changing chemical makeup of formulation (claim 35)
exposing formulation to high level of light (claim 36)
adding a pharmaceutical ingredient (claim 37)
crosslinking using a crosslink agent (claim 38), including covering with a sheet impregnated with crosslink agent (claim 39)
controlling water loss (claim 40)
crosslinking using ultraviolet radiation (claim 41)

Heat-triggered transformation (device-mediated)

Several claims are device-oriented:

transformation via heating (claim 43)
blowing heated air onto formulation (claim 44)
radiating infrared radiation (claim 45)
patch generating heat (claim 46), exothermic reaction patch (claim 47)
transformation by placing a layer of formulation onto a surface at least 28°C (claim 42)

How broad is the conversion-agent claim coverage?

Even with broad recitations, the functional core remains: conversion to a peelable coherent solid phase and that conversion is tied to evaporation (vehicle solvent). The conversion agent scope is expansive, but the formulation must still fit the system-level mechanism.

What is the evaporation/solidification/release control scope?

Featured snippet answer: The patent ties local anesthetic delivery to evaporation kinetics: anesthetic delivery continues during solvent evaporation and conversion into a peelable coherent solid phase, and delivery substantially stops when evaporation/conversion is complete; delivery is “controlled” by controlling evaporation time.

Key claim mechanics

Control delivery by evaporation time and conversion (claim 1)
Substantially stops delivery upon completion of conversion (claim 49)
Stops delivery upon complete evaporation of the solvent (claim 51)
Substantially completed upon conversion to coherent solid phase (claim 75)
Solvent property that complete evaporation stops delivery (claim 79 and 80-like language)
Conversion takes place within 30-60 minutes with complete anesthetization (claims 5-6, 56-57)

Timing is part of claim scope

The claim set includes specific performance windows:

~30 minutes for conversion and complete anesthetization
~60 minutes for conversion and complete anesthetization

Those dependent limitations can matter in infringement and in designing around by shifting conversion/deposition kinetics outside the claimed ranges, depending on claim dependency structure and interpretation.

What formulations are covered: methods and a paste formulation?

Independent method claims

The independent claims (1, 51, 66, 72 and 75-like variants) claim application-based methods with delivery and conversion conditions. They are centered on a “liquid phase” or “formulation” broadly, then repeatedly narrow via dependent claim examples.

Paste formulation claim

There is an explicit formulation claim for paste-to-solid conversion:

Claim 76: “A paste formulation … comprising a local anesthetic; a conversion agent … transforming from an initial paste phase to a peelable coherent, solid phase; and an evaporable solvent; the presence of said solvent being necessary in order for said formulation to deliver local anesthetic into normal human skin … within sixty minutes.”

Dependent formulation examples:

Lidocaine (claim 77)
Tetracaine (claim 78)
PVA conversion agent (claim 83)

This is important because a separate formulation claim can support a different infringement theory (sale/use/import of the composition) compared with purely method claims.

Claim mapping: how the dependent claims expand around the independent core

The following table summarizes how claim groups broaden scope, with practical “design surface” implications.

Claim cluster	What it adds	Scope impact for competitors
Local anesthetics	Tetracaine (2, 52, 53, 70, 78) and Lidocaine (52, 71, 77)	Confirms coverage includes common topical anesthetic actives
Evaporable solvent	Often water (3, 54, 51 family, 80-like)	Competitors using non-aqueous or mixed solvents may argue non-infringement if claim requires “water” (only where limited)
Human target	Skin (4, 55)	Main use case is topical dermal anesthesia
Conversion agent PVA	PVA expressly recited (8, 67, 81-85)	Strong coverage for PVA-based “peelable” gels
Borate/boric acid	sodium borate, boric acid, salts, boron (11-21, 18-23)	Broad ionic/coacervation conversion possibilities
Thermally reversible	thermally reversible gel polymer, Pluronic F127 (9-10, 61), solidifies 20-37°C (22, 65)	Coverage for thermogel systems triggered by body temperature
Passive vs active triggers	environment change, air/light, humidity, temperature, chemical change, crosslinking (24-42)	Captures many formulation activation approaches
Heat delivery devices	heated air, IR, heat patches, exothermic patch, 28°C surface placement (42-47)	Extends claim concept to external heat triggering
Solvent evaporation controls dosing	delivery controlled by evaporation time; stops on complete evaporation/conversion (1, 51, 75, 79-80)	Central infringement risk: timed release tied to evaporation endpoint
Conversion window performance	~30 min and ~60 min complete anesthetization (5-6, 56-57, 76 within 60 min)	If a competitor designs conversion outside these windows, it may impact validity/infringement depending on dependency and whether “about” is construed broadly

How strong is the likely patent “estate” around US 6,528,086 based on claim architecture?

Your provided material is claim text only. From the claim architecture itself, US 6,528,086 appears to be a system-level patent rather than a narrow composition:

It covers method of anesthetizing using a specific mechanism: evaporation-driven conversion plus rate-limited delivery that stops when evaporation is complete.
It covers broad classes of conversion agents, including PVA and borate systems, and also supports alternative trigger routes (environmental/chemical/thermal/light).
It includes at least one composition claim (paste formulation) with a functional performance requirement (deliver anesthetic within 60 minutes).

That combination typically yields a patent that is harder to design around purely by swapping solvent or anesthetic, unless the alternative system avoids the claimed “evaporation-controlled delivery endpoint that substantially stops when evaporation completes” or avoids the “peelable coherent solid phase conversion” architecture.

Which infringement theories are most relevant for this patent?

1) Process infringement (topical administration procedure)

Direct use of the claimed method steps during clinical/consumer use: apply formulation, allow evaporation-based conversion, achieve anesthetization during evaporation, stop dosing upon evaporation/conversion completion.

2) Product infringement (paste formulation claim)

Sale/import/use of a paste formulation meeting:

conversion from paste phase to peelable coherent solid phase
presence of an evaporable solvent necessary for delivery within 60 minutes

3) Indirect infringement risk via “designed to meet” performance

If a competitor’s product is engineered so anesthetic release is limited by evaporation kinetics and ends as the film/paste converts to a peelable coherent solid, it fits the system concept even if some components differ.

Patent landscape implications: where gaps usually appear around this type of claim

Given the breadth of conversion agent and triggers, design-around attempts typically target one of three choke points:

Avoid peelable coherent solid phase conversion
- Use non-peelable gels or non-coherent solidification morphologies
Decouple anesthetic delivery from evaporation completion
- Use controlled release mechanisms that do not “substantially stop” when solvent fully evaporates
Change the conversion-while-evaporating requirement
- Use phase change not driven by evaporable solvent evaporation, or use sustained release after solvent removal

Because the independent claims are anchored to evaporation-based conversion and delivery cessation tied to evaporation, those are the most direct vulnerabilities for an accused product.

Timeline and “exclusivity” positioning for US utility patents (mechanistic, not Orange Book-specific)

You did not provide the application/priority dates, patent grant date context, or any Orange Book listing for a specific NDC. Without those, no accurate expiration schedule, regulatory exclusivity calculation, or Hatch-Waxman/Biosimilar context can be produced from the claim text alone. The mechanism-level claim coverage is what matters for scope now.

Key takeaways

US 6,528,086 claims a topical local anesthetic system where evaporation of an evaporable solvent drives conversion to a peelable coherent solid phase, and anesthetic release is controlled by evaporation time.
The dosing concept is time-limited: local anesthetic delivery continues during evaporation and substantially stops once solvent evaporation/conversion completes, supporting an anti-overdosing rationale embedded in the claims.
The conversion agent is broadly covered, including PVA, boric acid/sodium borate and boron salts, carrageenan, gellan gum, and cellulose derivatives, plus thermally reversible gel polymers such as Pluronic F127.
The patent includes heat- and device-triggered transformation routes (heated air, IR, heat patches) and passive vs active trigger conversion paradigms.
A composition-level claim (paste formulation) adds a functional performance limiter: delivery into normal human skin within 60 minutes.

FAQs

1) What does “peelable coherent, solid phase” mean for infringement scope?
It is a functional-structural requirement: after evaporation-driven conversion, the applied material becomes a coherent solid that can be peeled from skin, not a dispersed or non-coherent residue. The claim language ties that solidification to the solvent evaporation endpoint.

2) Can non-water solvents avoid the patent?
Only where dependent claims explicitly require water (e.g., claims 3 and 54). The independent claims use “evaporable solvent” broadly, so solvent changes must avoid the overall evaporation-driven conversion and delivery-endpoint mechanism.

3) Does using lidocaine instead of tetracaine avoid infringement?
No. Lidocaine is explicitly recited (claims 52 and 71) as an example within the independent claim family, so swapping between these actives does not remove coverage.

4) If a product keeps anesthetic release after solvent evaporation, does it still infringe?
If the release does not substantially stop upon complete evaporation/conversion, it is the clearest potential design-around because the claim repeatedly ties dosing cessation to evaporation/conversion completion.

5) How do heat patches and IR devices factor into claim scope?
They are expressly covered as means to trigger transformation (claims 43-47). Using an external heat source to accelerate conversion does not avoid the patent if the conversion and evaporation-linked, time-limited release endpoint remains the same.

References

US Patent 6,528,086 (claims as provided by user prompt).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	345757	⤷ Start Trial
Australia	7719800	⤷ Start Trial
Canada	2386017	⤷ Start Trial
China	100367927	⤷ Start Trial
China	101219108	⤷ Start Trial
China	1376043	⤷ Start Trial
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Details for Patent: 6,528,086

Summary for Patent: 6,528,086