United States Drug Patent 6,635,045: Claims, Scope, Expiration, Litigation and Patent Landscape

U.S. Patent No. 6,635,045 protects a manufacturing process for loading a chloride-containing active ingredient, especially lidocaine hydrochloride, into a hydrogel reservoir attached to a silver/silver chloride electrode. Its central limitation is the use of salt in the unloaded reservoir to reduce corrosion of the Ag/AgCl electrode during subsequent loading with an electrode-corrosive ingredient. The patent also claims the resulting electrode assembly and narrow lidocaine/epinephrine formulations.

The patent issued October 21, 2003, from an application filed May 18, 2001. Its ordinary 20-year patent term therefore ran from the nonprovisional filing date and ended in 2021, subject to any patent-term adjustment or terminal-disclaimer effects recorded by the USPTO. The patent no longer provides enforceable U.S. exclusionary rights based solely on its claims. [1]

What does U.S. Patent 6,635,045 protect?

The patent protects a post-assembly loading process for an iontophoretic electrode. The process starts with an unloaded electrode assembly containing:

A silver/silver chloride, or Ag/AgCl, electrode.
A polymer reservoir containing an aqueous composition.
Salt in the aqueous composition at a concentration effective to inhibit electrode corrosion.
A later loading step in which an aqueous solution containing an active electrode-corrosive ingredient contacts the reservoir.

The patent is directed to electrically assisted transmembrane delivery, commonly called iontophoresis. The device uses an electrical current to move an active ingredient through or across skin. Ag/AgCl electrodes are useful in such systems but can be affected by chloride-containing formulations and other corrosive constituents.

The claimed process separates electrode assembly from active-drug loading. A manufacturer can make an unloaded electrode assembly containing a corrosion-inhibiting salt and subsequently introduce a predetermined drug dose into the reservoir.

What is the inventive concept of the patent?

The technical concept is controlling Ag/AgCl corrosion during drug loading by placing salt in the reservoir before the reservoir is contacted with a chloride-containing drug solution.

The independent process claim requires both:

Salt already dispersed in the polymer reservoir aqueous composition; and
Contact with an aqueous loading solution containing an active electrode-corrosive ingredient.

A process that merely mixes lidocaine hydrochloride into a hydrogel before attaching the electrode may fall outside the literal wording of claim 1 if it does not provide the required unloaded electrode assembly and later loading step. A process using a non-Ag/AgCl electrode also does not satisfy the express electrode limitation.

How do the claims divide between process and product protection?

Claims 1 through 14 are process claims. Claims 15 through 19 are electrode claims drafted in product-by-process form.

Claims	Subject matter	Principal limitations
1	Broad loading process	Ag/AgCl electrode, salted polymer reservoir, aqueous loading with corrosive active ingredient
2	Counterion relationship	Reservoir salt contains an ion matching the active ingredient counterion
3	Chloride embodiment	Corrosive ingredient includes chloride ions
4	Drug embodiment	Corrosive ingredient is a drug
5	Hydrochloride embodiment	Ingredient is a hydrochloride salt
6	Lidocaine embodiment	Ingredient is lidocaine HCl
7	Lidocaine/epinephrine embodiment	Loading solution also contains epinephrine
8	Loading technique	One or more droplets applied to the reservoir
9	Reservoir material	Polyvinylpyrrolidone hydrogel
10	Formulation range	Lidocaine HCl, epinephrine bitartrate and NaCl
11	Additive class	Chelating agent, humectant and antioxidant
12	Narrow reservoir and loading parameters	Approximately 24% PVP hydrogel, 0.06% NaCl and approximately 33% loading solution
13	Narrow additive formulation	EDTA, citric acid, glycerin and sodium metabisulfite
14	Defined loading composition	Specific lidocaine/epinephrine/stabilizer formulation
15	Product-by-process electrode	Electrode prepared using the claim 1 process
16	Narrow product formulation	Claim 15 product with claim 12 parameters
17	Product additives	Chelating agent, humectant and antioxidant
18	Product formulation	Lidocaine HCl, epinephrine bitartrate and NaCl
19	Product additives and formulation	Claim 18 formulation with EDTA, citric acid, glycerin and sodium metabisulfite

Claims 1 and 15 are the commercial center of gravity. Claims 6, 7, 9, 10 and 14 are more directly tied to the LidoSite-type lidocaine iontophoretic system.

What are the key limitations of independent claim 1?

Claim 1 is narrower than a general claim to loading a drug into an iontophoretic patch. An accused process would need to satisfy each of the following elements:

Ag/AgCl electrode

The electrode must be silver/silver chloride. A carbon, platinum, stainless-steel, titanium or other electrode would not literally meet this limitation.

Polymer reservoir with aqueous composition

The reservoir must contain a polymer with an aqueous composition dispersed in it. The claim does not restrict the polymer in the independent claim to PVP, but claim 9 narrows the reservoir to a polyvinylpyrrolidone hydrogel.

Salt effective to inhibit corrosion

The salt must be present in the reservoir before drug loading and must be present in an amount effective to inhibit electrode corrosion. This is a functional limitation. The patent's dependent claims identify NaCl and a salt having an ion corresponding to the active ingredient's counterion.

Aqueous loading solution

The active ingredient must be introduced through an aqueous loading solution. Dry powder loading, solvent-free impregnation or a process using a nonaqueous loading medium would raise a literal-scope issue.

Active electrode-corrosive ingredient

The ingredient must be active and electrode-corrosive. Claims 3 through 6 identify chloride ions, drugs, hydrochloride salts and lidocaine HCl as progressively narrower embodiments.

Timed contact sufficient for predetermined loading

The loading solution must contact the reservoir for enough time to load a predetermined amount. The claim does not require a particular loading duration, but the process must be controlled to achieve a defined drug quantity.

What formulations are protected by U.S. Patent 6,635,045?

The narrow formulation claims focus on lidocaine HCl with L-epinephrine bitartrate. The most specific claimed composition includes:

Component	Claimed amount
Lidocaine HCl	About 30% by weight
L-epinephrine bitartrate	About 0.57% by weight
NaCl	About 0.06% to about 0.9% by weight; claim 14 specifies about 0.06%
EDTA	About 0.03% by weight
Citric acid	About 0.06% by weight
Glycerin	About 30% by weight
Sodium metabisulfite	About 0.15% by weight

Claims 12, 13 and 16 add reservoir and loading quantities. The reservoir contains approximately 24% by weight, plus or minus 1%, of PVP hydrogel and approximately 0.06% NaCl. It is contacted with approximately 33%, plus or minus 10%, by weight of the loading solution.

The range limitations matter. A formulation containing materially different concentrations could avoid literal infringement of the narrow claims even if it performs the same general function. The broad claims remain dependent on the process architecture and Ag/AgCl electrode.

How strong is the patent estate for this technology?

The patent was technically focused rather than platform-wide. Its strongest scope was the combination of:

Ag/AgCl electrode construction;
PVP hydrogel reservoir;
chloride-containing active ingredient;
preloaded corrosion-control salt;
post-assembly loading; and
lidocaine/epinephrine formulation chemistry.

Its practical strength during the term depended on whether a competitor used the same manufacturing sequence. The claims do not broadly cover every iontophoretic lidocaine device, every Ag/AgCl electrode or every hydrogel reservoir.

Claim-strength assessment

Issue	Assessment
Core manufacturing concept	Stronger where the competitor uses pre-salted reservoirs and later aqueous drug loading
Electrode limitation	Narrows the field to Ag/AgCl systems
PVP limitation	Appears only in dependent claims, preserving broader polymer scope in claim 1
Lidocaine scope	Claims 6, 10, 12-14 and 16-19 are commercially specific but narrow
Functional corrosion limitation	Potentially important for infringement and validity analysis
Product-by-process claims	Useful against products having the claimed product characteristics, but less certain where process differences produce indistinguishable products
Design-around potential	Meaningful through different electrodes, loading order, reservoir chemistry or formulation

The patent's strongest commercial relevance was therefore to a specific patch-manufacturing process, not to the entire iontophoresis market.

When did U.S. Patent 6,635,045 lose exclusivity?

The patent's ordinary term ended in 2021. A patent term adjustment could have extended the expiration date, but any such adjustment would be reflected in the USPTO patent record. The patent cannot now support a new U.S. infringement action based on conduct occurring after expiration. [1]

The expiration eliminated patent enforcement risk from this patent itself. It did not automatically eliminate risk from:

Continuations or divisionals;
Separate formulation patents;
Electrode-structure patents;
Device-control patents;
Manufacturing patents;
Trade secrets;
Regulatory exclusivity; or
Foreign counterparts with different term histories.

A freedom-to-operate review must therefore distinguish Patent 6,635,045 from the broader family and related LidoSite technology.

What is the Orange Book status of the related lidocaine product?

The relevant commercial product was the LidoSite Topical System, an iontophoretic delivery system using lidocaine hydrochloride and epinephrine. The FDA approved LidoSite through an NDA pathway rather than an ANDA pathway because the product was a drug-device combination with a proprietary delivery system. FDA Orange Book records identify approved drug products, patent listings and exclusivity information, but Orange Book treatment does not convert every manufacturing patent into a continuing barrier to generic or follow-on entry. [2, 3]

The FDA approval and Orange Book status of the product must be separated from the patent status:

Regulatory issue	Relevance
NDA approval	Establishes FDA authorization for the listed product
Orange Book patent listing	Can trigger patent certification procedures for an ANDA
Patent expiration	Removes the listed patent's exclusionary force after expiration
Product discontinuation	Does not by itself determine patent validity
Drug-device combination	May require a tailored regulatory pathway rather than a conventional small-molecule ANDA
Device changes	Can create new regulatory and patent questions independent of the original patent

The product's regulatory history is relevant to commercial precedent, but Patent 6,635,045 does not create current FDA exclusivity.

Were Paragraph IV challenges or patent litigation directed to this patent?

A Paragraph IV certification applies to an ANDA applicant challenging an Orange Book-listed patent. The commercial complexity of an iontophoretic lidocaine system makes a conventional generic challenge less straightforward than a tablet or injectable-drug challenge. A follow-on applicant may need to address both the active ingredient and the delivery-device system.

The key legal point is that any Paragraph IV significance of Patent 6,635,045 ended when the patent expired. A Paragraph IV certification cannot create a new infringement exposure for an expired patent. A historical listing could still appear in FDA records, but it has no present term-based blocking effect.

No current litigation risk should be attributed to Patent 6,635,045 alone. Any continuing dispute would need to arise from a different unexpired patent, a related patent family member or nonpatent rights.

Which companies are associated with the technology?

The technology is associated with Vyteris and the LidoSite iontophoretic delivery platform. Commercial and regulatory records also identify B. Braun-related commercialization activity for LidoSite. Ownership, licensing and enforcement rights must be checked by patent-family member because assignee changes, mergers, security interests and licenses can differ across jurisdictions and time.

The relevant commercial roles were:

Entity or category	Role
Vyteris	Developer and technology holder associated with the iontophoretic platform
B. Braun-related entities	Commercial and medical-product distribution involvement associated with LidoSite
FDA	Approval and postmarket regulatory oversight
Generic or combination-product applicants	Potential follow-on entrants, subject to applicable FDA pathway and patent certifications

Public records do not establish a continuing license or an active enforcement position for Patent 6,635,045 after expiration.

What generic launch risks exist?

The patent does not create a current generic launch block. During its term, the main design-around routes were:

Use a different electrode material.
Load the active ingredient before attaching or integrating the Ag/AgCl electrode.
Avoid chloride-containing active ingredients.
Use a reservoir without the claimed salt arrangement.
Use a non-PVP reservoir to avoid dependent-claim limitations.
Change the lidocaine, epinephrine or excipient concentrations.
Use a different delivery platform, such as passive topical delivery, microneedles or another electrically assisted configuration.

A competitor that used the same Ag/AgCl/PVP/post-loading process with lidocaine HCl and epinephrine would have faced materially greater historical infringement risk. That risk is now time-limited by patent expiration.

How does this patent compare with conventional lidocaine patents?

Patent 6,635,045 differs from ordinary lidocaine composition patents in three ways.

First, it is process-centered. It does not primarily claim lidocaine as a chemical entity.

Second, it is device-dependent. The Ag/AgCl electrode is essential to the independent claims.

Third, it claims manufacture and loading rather than only administration. A product could contain lidocaine HCl yet avoid the patent if it uses a different delivery technology or electrode architecture.

Patent category	Typical protected subject matter	Relationship to 6,635,045
Lidocaine composition patent	Chemical composition or salt	Separate from the electrode-loading process
Topical formulation patent	Cream, gel, patch or excipient system	May overlap with narrow formulation claims
Iontophoretic device patent	Electrode, controller or current profile	Complementary technology
Method-of-use patent	Applying lidocaine through skin for anesthesia	Separate from manufacturing claims
Manufacturing patent	Reservoir loading and corrosion control	Direct category of 6,635,045
Combination-product patent	Drug plus delivery device	Potentially overlapping, but independently analyzed

What geographic coverage does the patent have?

U.S. Patent 6,635,045 provides U.S. protection only. Foreign counterparts, if any, required separate examination for:

Filing and priority dates;
National-phase status;
Patent-term adjustment or extension;
Maintenance fees;
Oppositions;
Translations;
Expiration;
Abandonment; and
Local claim scope.

A U.S. expiration does not establish expiration of corresponding European, Canadian, Japanese or other national patents. The geographic patent landscape must be built from the priority family and national registers, not inferred from the U.S. patent number.

What manufacturing and intellectual-property barriers remain?

The expired patent removes one formal patent barrier, but commercial entry can still face operational barriers:

Reproducible hydrogel manufacture;
Controlled drug loading into a preassembled electrode;
Uniform dose distribution;
Ag/AgCl corrosion control;
Shelf-life stability of epinephrine;
Protection from oxidation;
Sterility and packaging;
Skin-contact performance;
Electrical-current control;
Combination-product FDA requirements; and
Manufacturing know-how not disclosed in the claims.

The formulation includes sodium metabisulfite, citric acid, EDTA and glycerin, indicating a stability and processing strategy directed to oxidation control, chelation, pH management and moisture retention. Those functions may be technically important even though the patent claims do not provide continuing exclusivity.

Key Takeaways

U.S. Patent 6,635,045 covers a method for loading an Ag/AgCl iontophoretic electrode reservoir with a chloride-containing active ingredient after incorporating corrosion-inhibiting salt into the reservoir.
The commercial center of the patent is a PVP hydrogel system containing lidocaine HCl and L-epinephrine bitartrate.
Claims 10, 12, 13, 14 and 16 through 19 protect narrow formulation and loading parameters.
Claims 15 through 19 are product-by-process electrode claims.
The patent's ordinary U.S. term ended in 2021, subject to any recorded patent-term adjustment.
The patent does not provide current U.S. exclusivity or a present Paragraph IV blocking right.
Current freedom-to-operate risk must be assessed against related patents, continuations, device patents, formulation patents, regulatory requirements and trade secrets.
The patent is relevant to LidoSite-type manufacturing but does not broadly cover all lidocaine products or all iontophoretic delivery systems.

FAQs About U.S. Patent 6,635,045

Does Patent 6,635,045 cover all lidocaine iontophoresis patches?

No. The claims require the specified Ag/AgCl electrode and reservoir-loading architecture. Many lidocaine iontophoresis systems could fall outside the claims through different electrode materials, loading sequences or reservoir compositions.

Is lidocaine hydrochloride itself patented by U.S. Patent 6,635,045?

No. The patent claims a manufacturing method and electrode assembly involving lidocaine HCl. It does not claim the basic chemical compound as such.

Can a company still sue for infringement of Patent 6,635,045?

The patent's ordinary term ended in 2021. It cannot support a new infringement claim for post-expiration conduct unless an unusual, separately applicable legal issue affects the relevant period. Related unexpired patents would require separate analysis.

Does the patent protect the LidoSite brand?

No. Patent rights, trademarks, FDA approval and commercial branding are separate rights. The patent concerns electrode manufacture and loading, not ownership of the LidoSite name.

Are biosimilar rules relevant to this patent?

No. LidoSite is a small-molecule drug-device combination, not a biologic. Biosimilar procedures under the Public Health Service Act are not the relevant pathway. Follow-on applicants would need to evaluate the applicable drug-device regulatory route and any remaining patent rights.

References

United States Patent and Trademark Office. (2003). U.S. Patent No. 6,635,045, Method for making an electrode assembly for electrically assisted transmembrane delivery of an active ingredient. https://patents.google.com/patent/US6635045
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	369891	⤷ Start Trial
Australia	7310401	⤷ Start Trial
Canada	2413624	⤷ Start Trial
Germany	60129965	⤷ Start Trial
European Patent Office	1294439	⤷ Start Trial
Japan	2004501727	⤷ Start Trial
Japan	4024673	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,635,045

Summary for Patent: 6,635,045