Executive summary
US Patent 4,201,211 covers transdermal clonidine and a related imidazolidinylidene benzeneamine (“benzeneamine”) skin-patch therapeutic system defined by (i) a clonidine/benzeneamine reservoir adjacent an essentially drug-impermeable backing, (ii) controlled-rate drug release via an intervening release means including a microporous membrane (claims 3-14), (iii) a drug-permeable skin-adhesive layer that immobilizes a substantial portion of drug at the skin interface (claims 3-14), and (iv) in narrower claims, specific composition ranges (gelled mineral oil + polyisobutene blend; microporous membrane porosity/tortuosity/thickness; polypropylene membrane; aluminized PET backing; strippable impermeable coating). The claim structure is primarily device and material-configuration oriented, not a bare “method of treating hypertension with clonidine.” Enforcement leverage is strongest against patches that replicate the same laminate architecture and parameter ranges for drug distribution, permeability, and microporous membrane properties. Patent term and any remaining enforceability in the US are effectively expired given the application era.
US Patent 4,201,211 scope and claims for clonidine and transdermal patch systems
Core claim architecture: controlled transdermal delivery of an alpha-adrenergic agonist through “a predetermined area of unbroken skin” for a “prolonged time period” using a patch with (a) impermeable backing, (b) drug reservoir, (c) release means, and (d) affixing means. Independent claim 1 uses clonidine and is broad on the “release means” and “affixing means.” Dependent claims 2-14 progressively constrain drug type (claim 3), and then constrain the patch’s sandwich laminate and its material specs.
What does Claim 1 cover (clonidine patch)?
Claim 1 requires all of the following:
- Therapeutic system in the form of a skin patch for transdermally administering clonidine.
- Delivery through “a predetermined area of unbroken skin” with controlled manner and prolonged time period to effect central alpha-adrenergic stimulation.
- Patch components:
- (a) Backing “substantially impermeable to clonidine,” one face is the top of the patch.
- (b) Clonidine reservoir adjacent the opposite face of the backing with enough clonidine for prolonged time at a central alpha-adrenergic stimulating rate.
- (c) Means for releasing clonidine from the reservoir to the skin at that rate.
- (d) Means for affixing the patch to the skin.
Scope implication: Claim 1 is strong for any transdermal clonidine system that uses an essentially clonidine-impermeable backing + adjacent clonidine reservoir + controlled release + skin attachment. It does not, on its face, require a microporous membrane, drug-permeable adhesive, or specific formulation ranges.
How Claim 2 narrows (hypertension rate)
- Claim 2 narrows the “central alpha-adrenergic stimulating rate” to one that provides hypertension therapy.
- This does not require a specific mcg/hr in claim 2.
What Claim 3 adds (sandwich laminate and “benzeneamine” version)
Claim 3 switches the active: “2,6-dichloro-N-2-imidazolidinylidene benzeneamine” and specifies a sandwich-type laminate with four laminae:
- Backing lamina: substantially impermeable to the benzeneamine (top).
- Benzeneamine reservoir lamina adjacent to backing:
- amount sufficient for prolonged time at alpha-adrenergic stimulating rate
- dispersed in a carrier permeable to the benzeneamine
- Microporous membrane lamina adjacent and below reservoir:
- benzeneamine released through it “at said rate” after patch affixed to skin
- Contact adhesive lamina adjacent and below microporous membrane:
- adhesive is permeable to benzeneamine
- adhesive contains benzeneamine amount constituting at least a substantial portion of drug “immobilized” by predetermined area of skin
Scope implication: Claim 3 is narrower than claim 1 in that it requires the specific laminate architecture and two drug-permeable functional layers:
- a carrier-permeable reservoir and
- a benzeneamine-permeable adhesive, plus a microporous membrane as the release control.
How Claims 4-7 narrow (hypertension, dosing ranges, strippable layer)
- Claim 4 ties rate to hypertension therapy.
- Claim 5: rate 0.1 to 100 mcg/hr; adhesive benzeneamine amount 10 to 300 mcg/cm².
- Claim 6: rate 0.2 to 70 mcg/hr; adhesive benzeneamine amount 150 to 250 mcg/cm².
- Claim 7: includes a strippable coating lamina below the contact adhesive that is substantially impermeable to adhesive components and stripped before use.
How Claims 8-10 narrow (gelled mixture composition with polyisobutene blend)
- Claim 8: carrier and contact adhesive are a gelled mixture of mineral oil (approx. 10 to 100 cP at 25°C) and polyisobutene.
- Claim 9: polyisobutene blend:
- first PI with viscosity-average molecular weight 35,000 to 50,000
- second PI with viscosity-average molecular weight 1,000,000 to 1,500,000
- Claim 10 sets weight ranges:
- mineral oil 35% to 65%
- first PI 10% to 40%
- second PI 10% to 40%
Scope implication: these claims anchor the technology to a particular adhesive/carrier gel system and specify PI molecular weight distribution by viscosity-average MW, plus mineral oil viscosity at 25°C. Designing around means changing adhesive/carrier chemistry or removing this exact polymer blend architecture.
How Claims 11-14 narrow (membrane and backing materials + fully specified embodiment)
- Claim 11: microporous membrane lamina:
- porosity 0.1 to 0.85
- tortuosity 1 to 10
- thickness 10^-3 to 10^-2 cm
- Claim 12: microporous membrane made of polypropylene.
- Claim 13: backing layer made of aluminized polyethylene terephthalate.
- Claim 14 compiles a full parameter set: rate 0.2 to 70 mcg/hr; adhesive drug 150 to 250 mcg/cm²; undissolved benzeneamine particle size 5 to 20 microns; carrier composition per claims 8-10; contact adhesive is the same gelled mixture; microporous membrane polypropylene; backing aluminized PET.
Scope implication: Claim 14 reads like an implemented product configuration. Any close product using the same laminate and parameter windows has direct infringement risk if “substantially impermeable/permeable” elements map and the release rate and loading are met.
How broad are “substantially impermeable/permeable” terms in US 4,201,211?
Most enforceable elements are the structural relationships and functional layers, not the exact numeric ranges in the dependent claims.
What’s most likely to be argued as claim scope anchors
- “Substantially impermeable to clonidine/benzeneamine” (backing) forces selection of a backing that blocks drug migration upward/back into backing.
- “Reservoir adjacent the opposite face of the backing” requires spatial adjacency.
- Claim 3’s “microporous membrane lamina adjacent and below the benzeneamine reservoir lamina” makes the release-control layer a required structural element.
- “Contact adhesive lamina … permeable to benzeneamine” and drug immobilized “by predetermined area of skin” links the adhesive formulation to drug partitioning.
Where design-arounds typically focus
- Removing the microporous membrane as a distinct lamina (or shifting the rate control to a different mechanism).
- Changing the adhesive such that it is no longer permeable to the drug in the claim sense, or altering how drug is immobilized.
- Substituting backing materials not meeting aluminized PET, where a doctrine-of-equivalents argument would be more difficult for product-specific defenses tied to materials and specs in dependent claims.
What patents protect transdermal clonidine with controlled release patches in the US around this era?
This patent’s claim set aligns with a broader transdermal delivery technology cluster (reservoir + membrane + adhesive laminate). For “what patents protect” questions, the relevant analysis is a layer-by-layer claim overlap strategy:
- Reservoir + controlled release: claims overlap with patents covering controlled-rate transdermal reservoirs.
- Microporous membrane release-control: overlap with membrane-controlled delivery systems.
- Drug-permeable adhesives with drug loading: overlap with pressure-sensitive adhesive and drug-immobilization interfaces.
- Impermeable backing: overlap with film backings designed to block drug permeation.
However, without the complete bibliographic data for US 4,201,211 (filing date, assignee) and without a prepared set of neighboring US family members and cited references, a definitive “patent landscape” cannot be computed from the claim text alone.
When does US Patent 4,201,211 lose exclusivity in the US (patent expiration and term)?
Given the patent number (US 4,201,211) and the issuance era, the US patent term has run.
- US utility patents generally expire 20 years from earliest non-provisional US filing date, subject to adjustments.
- For patents issued as “4,2xx,xxx,” term typically falls in the late 1980s/1990s window barring unusual priority/filing delays.
No later regulatory exclusivity is created by device claims; exclusivity would be driven by patent term. As of the current date, infringement exposure is not tied to active US enforceability of this patent’s claims.
Is US 4,201,211 relevant to FDA Orange Book listings for clonidine products?
This patent is a classic early-generation transdermal patch patent. Whether it appears in the Orange Book depends on whether it was listed for a specific NDA or ANDA with the transdermal clonidine product for which it is claimed.
From the claim text provided, there is no direct linkage to:
- specific NDA/ANDA product codes,
- the drug sponsor,
- or any Orange Book listing identifiers.
Therefore, a correct Orange Book status call cannot be made here.
What generic entry risks exist for transdermal clonidine if US 4,201,211 is asserted?
Claim 1’s breadth could have supported earlier “patch architecture” assertions. Risk would rise for generic entrants that:
- use an impermeable backing + clonidine reservoir + controlled release + skin affixing,
- deliver clonidine in a way meeting “prolonged time” and “central alpha-adrenergic stimulating rate.”
But with the patent term effectively expired (see above), generic entry risk is not a function of live enforceability of US 4,201,211.
How does claim scope map to likely transdermal patch designs (where infringement would concentrate)?
Claim 1 (clonidine) infringement map
A candidate product must have:
- a backing that blocks clonidine,
- a reservoir containing clonidine,
- controlled release at a rate aligned with hypertension therapy dosing,
- an affixing means.
The biggest uncertainty for enforcement would be whether the product’s release mechanism qualifies as the claim’s generic “means for releasing” at the required rate, absent a microporous membrane requirement.
Claims 3-14 (benzeneamine) infringement map
Infringement concentration would be high where a competitor replicates:
- laminate sequence: backing → reservoir → microporous membrane → drug-permeable contact adhesive → optionally strippable impermeable coating
- microporous membrane material (polypropylene) and property ranges (porosity/tortuosity/thickness)
- adhesive/carrier gel: mineral oil + polyisobutene blend with specified viscosity-average molecular weights and weight fractions
- drug loading in reservoir and adhesive (including “undissolved particle size” in claim 14)
- adhesive loading per area (mcg/cm²) and release rates (mcg/hr)
A competitor can reduce risk by breaking any mandatory architectural/parameter element, particularly the microporous membrane layer, the gelled PI/mineral oil composition, or the adhesive permeability/drug partitioning.
Patent claim strength scoring for US 4,201,211 (by claim tier)
Highest specificity (strongest in enforcement)
- Claim 14: full parameter embodiment compilation (rates, loading, particle size, carrier gel composition, membrane/backing materials). Strongest as a litigation target because it is tightly circumscribed.
Medium specificity (stronger than claim 1, narrower than claim 14)
- Claims 11-13: microporous membrane properties and materials, backing material.
- Claims 5-7: rate and adhesive loading ranges; strippable coating.
Broadest structural claim (potentially strongest pre-expiration)
- Claim 1: no requirement for microporous membrane or specific gel composition. Broadest device architecture for clonidine.
Net: if the patent were still within term, claim 1 would support broader architecture arguments, while claims 3-14 would support more product-matching infringement.
Key takeaways
- US 4,201,211 claim scope is patch-architecture focused: impermeable backing + drug reservoir + controlled release + skin affixing, with dependent claims that lock in a sandwich laminate featuring a microporous membrane and drug-permeable contact adhesive.
- Claim 1 is broad for clonidine; claims 3-14 are narrow and embodiment-like for the benzeneamine form, specifying membrane properties, polymer blend adhesive composition, backing material, and dosing/loading ranges.
- As a practical matter for current US freedom-to-operate, this patent’s enforceability is effectively not a live risk because its term has run for a patent of this issuance era.
- Litigation/invalidation outcomes would likely hinge on whether an accused patch recreates the required laminate sequence and whether rate control and drug-permeable adhesive behavior meet the functional claim limitations.
FAQs
1) What is the main independent claim in US 4,201,211 and what does it require?
Claim 1 is the independent claim for a clonidine transdermal patch requiring an impermeable backing, a clonidine reservoir adjacent the backing, means for releasing at a central alpha-adrenergic stimulating rate for a prolonged time, and means for affixing to skin.
2) Do claims 3-14 require a microporous membrane lamina?
Yes. Claim 3 requires a microporous membrane lamina adjacent below the reservoir through which the drug is released after the patch is affixed.
3) What parameters in US 4,201,211 are most likely to drive design-arounds?
The microporous membrane properties/material, the gelled adhesive/carrier composition (mineral oil + polyisobutene blend with specified molecular weight distributions and weight ranges), the adhesive loading in mcg/cm², and the release rate in mcg/hr.
4) Is “hypertension therapy” explicitly required in the claims?
Yes in dependent claims 2 and 4, which narrow the central alpha-adrenergic stimulating rate to rates that provide hypertension therapy.
5) Is US 4,201,211 likely to be listed in the Orange Book for clonidine patches?
Orange Book status cannot be determined from the claim text provided, because listing depends on specific FDA product entries and patent listing records.
References (APA)
No external sources were cited in the provided materials; therefore no reference list is included.
