US Patent 5,858,383: Claim Scope, Expiration, and Ectoparasite Treatment Patent Landscape

US Patent 5,858,383 covers topical ectoparasite-treatment methods and compositions that use a water-soluble or water-dispersible, substantially air-impermeable liquid containing a skin-compatible surfactant. The claims extend to human head-lice treatment, animal ectoparasites, thickened gels or jellies, prolonged contact, rinsing, and enzyme-assisted nit removal. The patent issued on January 12, 1999, and its ordinary statutory term has expired. It therefore does not create a current US patent barrier to commercial development, although it remains relevant as prior art and as a possible source of technical disclosure. [1]

What does US Patent 5,858,383 protect?

The patent protects two related categories:

Methods for treating ectoparasites by applying an occlusive, surfactant-containing liquid to skin, maintaining contact until the parasites die, and removing the composition and dead parasites.
Compositions containing the specified liquid formulation and an enzyme that loosens nits from skin or hair.

The patent is directed principally to physical suffocation or immobilization of parasites rather than to a conventional neurotoxic insecticide. The claims do not require a named active pesticidal ingredient such as permethrin, pyrethrin, ivermectin, or malathion.

The principal technical limitations are:

Limitation	Significance
Water-soluble or water-dispersible liquid	Excludes many purely oil-based or water-insoluble formulations
Substantially air-impermeable	Requires an occlusive or suffocating layer in the intended use
Skin-compatible surfactant	Requires at least one surfactant within the listed functional or chemical categories
Contact until parasites are killed	Makes treatment duration and efficacy relevant
Removal of composition and dead parasites	Requires a removal step in the method claims
Enzyme for nit removal	Required by composition claim 11 and its dependents
Thickener or gum	Narrows certain dependent claims to gel or jelly products
Human scalp and head lice	Narrows claims 3, 9, and 10 to pediculosis capitis

How do the independent claims differ?

Claims 1, 9, and 11 are the principal scope-defining claims.

Claim	Claim type	Covered subject matter	Key additional limitation
1	Method	Topical treatment of ectoparasites on animal skin	Surfactant-containing, substantially air-impermeable liquid; contact; removal
9	Method	Treatment of human scalp infected with head lice	Same core formulation and treatment sequence as claim 1
11	Composition	Treatment of ectoparasites and nits	Requires the surfactant-containing liquid plus at least one nit-loosening enzyme

Claim 1 is the broadest method claim in subject-matter terms because it applies to animal skin generally. “Animal” includes humans in ordinary patent usage unless the specification or prosecution history indicates otherwise, but claim 9 removes that ambiguity by expressly targeting the human scalp and head lice.

Claim 9 is narrower than claim 1 because it requires:

Human scalp;
Head lice;
The specific application, contact, and removal sequence; and
The same broad surfactant category.

Claim 11 is structurally different. It is a composition claim, not a treatment-method claim, and requires an enzyme. A product lacking an enzyme would generally fall outside claim 11 even if it satisfied the liquid, surfactant, and occlusion limitations.

What surfactants fall within the patent claims?

The claims use a long Markush-style list covering seven broad surfactant classes:

Synthetic anionic surfactants;
Nonionic surfactants;
Cationic surfactants;
Amphoteric surfactants;
Zwitterionic surfactants;
Polar nonionic surfactants with a semipolar bond; and
Soaps.

The anionic class is particularly broad. It covers compounds with an organic hydrophobe containing 8 to 26 carbon atoms and a solubilizing group selected from sulfonate, sulfate, carboxylate, phosphonate, and phosphate groups. It also expressly identifies acyl sarcosinates, isethionate reaction products, acyl N-methyl taurides, and phosphate esters, including ethoxylated phosphate esters.

The nonionic class includes:

Ethoxylated hydrophobic compounds;
Alcohols carrying oxyethylene and oxypropylene chains;
Ethylene oxide-propylene oxide-ethylene diamine condensates; and
Alkyl saccharides.

This drafting strategy creates broad chemical coverage but also introduces infringement questions about whether a particular commercial surfactant fits one of the enumerated categories. A product does not infringe merely because it is a detergent or produces a suffocating film. It must satisfy the claim’s water-dispersibility, skin-compatibility, and listed surfactant limitations.

What do the dependent claims add?

Claim	Added limitation
2	Enzyme that loosens nits from skin and hair
3	Human scalp and head lice
4	Thickening agent
5	Viscosity of at least about 1 centipoise at 20°C
6	Water-based pharmaceutically acceptable jelly containing gum
7	Contact time of about 4 to 24 hours
8	Removal by rinsing with water
10	Enzyme limitation applied to the human scalp/head-lice method
12	Thickener in the composition
13	Viscosity of at least 1 centipoise at 20°C
14	Enzyme concentration of about 0.0001% to 10% by weight
15	Thickener plus viscosity of at least about 1 centipoise

Claims 5 and 13 have limited narrowing effect. A viscosity of at least 1 centipoise at 20°C is close to the viscosity of water, so most practical liquid, gel, lotion, and shampoo formulations would likely satisfy the numerical threshold. The more consequential viscosity limitation is the requirement for a thickener in claims 4, 12, and 15.

Claim 7 is commercially important because it covers a contact period of approximately four to 24 hours. A formulation marketed for overnight use could satisfy this limitation if the other claim elements are met. A short-contact shampoo used for several minutes would not necessarily fall within claim 7, although it could still implicate claims 1 or 9.

What formulations are protected by US 5,858,383?

The patent is directed to formulations with four central characteristics:

An aqueous or water-dispersible liquid base;
A surfactant capable of supporting a substantially air-impermeable coating;
Optional thickening or gelling components; and
In the composition claims, an enzyme capable of loosening nits.

Potentially relevant formulation types include:

Formulation type	Likely relevance
Aqueous surfactant lotion	Core formulation category
Thickened aqueous gel	Covered by dependent claims if the other limitations are met
Gum-containing jelly	Specifically addressed by claim 6
Overnight scalp treatment	Potentially relevant to claim 7
Enzyme-containing lice gel	Directly relevant to claims 11-15
Conventional insecticide shampoo	Not automatically covered; must satisfy all claim elements
Silicone or mineral-oil occlusive product	May avoid the claims if it lacks the required water-soluble or water-dispersible surfactant
Dry powder or aerosol	Generally outside the liquid-composition limitations
Water-insoluble oil without qualifying surfactant	Potentially outside the literal claim scope

The claims do not require a specific enzyme. The functional language focuses on an enzyme that loosens nits from skin and hair. Candidate technologies could include proteolytic, keratinolytic, or other enzymes, but technical function and claim construction would depend on the specification, prosecution history, and evidence of nit-loosening activity.

How strong is the patent estate for US 5,858,383?

The issued patent appears to have a single principal US patent covering the disclosed concept. Its strength during the enforceable period would have varied by claim.

Claim group	Relative scope	Principal vulnerability
Claims 1 and 9	Broad method claims	Prior art involving occlusive lice treatments, surfactants, shampoos, and removal steps
Claims 2 and 10	Narrower enzyme methods	Enablement, written-description, and obviousness issues across broad enzyme classes
Claims 3 and 9	Human head-lice use	Prior art directed specifically to pediculosis
Claims 4-8	Formulation and use details	Limited commercial reach because of added limitations
Claim 11	Enzyme-containing composition	Requires all composition elements, including the enzyme
Claims 12-15	Narrow composition claims	Easier design-around through formulation architecture or enzyme concentration

The broadest claims combine familiar elements: a topical liquid, a surfactant, an occlusive effect, parasite killing, and physical removal. That combination may have been commercially useful, but it also creates potential obviousness arguments under 35 U.S.C. § 103 if earlier references disclosed occlusive lice treatments, surfactant-based scalp products, prolonged contact, or enzyme-assisted nit removal. [2]

The composition claims are narrower because they require an enzyme. They may have offered stronger protection against an enzyme-containing commercial product, but they also presented more demanding proof requirements. A patentee would need to establish that the accused product contains a qualifying enzyme and that the enzyme performs the claimed nit-loosening function.

When did US Patent 5,858,383 lose exclusivity?

US Patent 5,858,383 is expired. It issued on January 12, 1999. Under the pre- and post-1995 patent-term rules, the ordinary term would generally have ended no later than 2016, subject to the patent’s actual filing history and any applicable term adjustment. [1,3]

The practical timeline is:

Event	Date or period
Patent issued	January 12, 1999
Ordinary 17-year issue-based endpoint, if applicable	January 12, 2016
Expected end of ordinary enforceability	2016
Current status	Expired
Current blocking effect	None for new US manufacture, sale, or use

Patent expiration does not erase the patent from the prior-art record. The disclosure can remain relevant to later patentability analyses, freedom-to-operate assessments, and validity disputes involving later patents.

What is the Orange Book status of US 5,858,383?

US Patent 5,858,383 is not itself an Orange Book listing. The Orange Book lists patents submitted for approved drug products, not every patent directed to a pharmaceutical composition or treatment method. [4]

The patent claims a formulation and treatment approach for ectoparasites, but the patent number alone does not establish:

An FDA-approved product;
An approved new drug application;
An Orange Book-listed product patent;
A regulatory exclusivity period; or
A market exclusivity period.

A commercial lice product using the claimed approach could face separate FDA classification and labeling questions. A product that claims to kill head lice is generally regulated according to its intended use and active ingredients, while a product positioned only as a mechanical removal aid may be assessed differently. FDA’s OTC drug framework and the applicable pediculicide monograph or approval pathway must be analyzed separately from patent status. [5]

Did the patent create Paragraph IV or generic-entry risk?

The patent could have been relevant to a generic or follow-on product only if it had been listed for an approved reference product in the Orange Book. No Orange Book listing is established by the patent number itself.

A Paragraph IV certification would therefore depend on a separate approved drug product and listing record. The patent’s expired status eliminates any current Paragraph IV-based launch barrier from this patent. During the enforceable period, a generic applicant would have needed to assess:

Whether the patent was listed against the reference drug;
Whether the proposed product practiced the treatment method;
Whether the formulation contained a qualifying surfactant;
Whether the product was enzyme-containing;
Whether the proposed labeling induced performance of a claimed method; and
Whether the patent was invalid or unenforceable.

For a non-listed, non-NDA topical product, ordinary patent litigation rather than Hatch-Waxman litigation would have been the more likely framework. [4,6]

What generic launch scenarios exist today?

Because the patent has expired, the main launch scenarios are:

Product design	Current risk from US 5,858,383
Permethrin or pyrethrin lice treatment	No live patent risk from this patent
Dimethicone or silicone-based suffocation product	No live patent risk from this patent
Aqueous surfactant lotion without enzyme	No live patent risk; historical claim relevance only
Enzyme-containing nit-removal gel	No live patent risk; may implicate later patents
Overnight occlusive scalp formulation	No live patent risk; later formulation patents require review
Animal ectoparasite product	No live patent risk from this patent
Product using the same commercial formulation disclosed in the patent	No live patent risk from this expired patent

The relevant current risk is likely to come from later patents covering specific ingredients, delivery systems, dimethicone concentrations, botanical actives, enzyme combinations, applicators, treatment protocols, or veterinary indications.

Which companies or technologies may challenge the commercial concept?

The patent’s commercial concept competes across several technology groups:

Technology group	Mechanism	Typical competitive position
Pyrethrins and piperonyl butoxide	Neurotoxic insecticidal activity	Established OTC lice-treatment category
Permethrin	Insecticidal activity	Established pharmaceutical treatment
Malathion	Organophosphate insecticide	Prescription or regulated product category
Spinosad	Insecticidal activity	Prescription treatment in some markets
Ivermectin	Neuroactive antiparasitic activity	Prescription topical or oral use
Dimethicone and silicone systems	Physical immobilization or suffocation	Directly competitive with occlusive approach
Combing and nit-removal systems	Mechanical removal	May avoid drug-active ingredient claims
Enzyme-assisted products	Nit loosening	Closest to claims 2, 10, and 11-15

The expired patent does not determine whether a competing product is free of later patent rights. A company commercializing a modern lice product would need a current landscape search around the specific active ingredient, formulation, manufacturing process, packaging, and labeling.

What patent litigation or settlement issues affect the patent?

The supplied claim set establishes the patent’s technical scope but does not establish an active US infringement case, settlement, license, or consent judgment. Since the patent is expired, a new infringement action based solely on post-expiration conduct would not provide prospective exclusion.

Historical damages claims would have been limited by the six-year damages window under 35 U.S.C. § 286, subject to litigation-specific facts. [7] Any historical settlement or license would not automatically extend the patent term or create a current market restriction.

The principal litigation issues during the patent’s life would have included:

Whether the accused formulation was substantially air-impermeable;
Whether its surfactant fit the Markush language;
Whether the formulation was water-soluble or water-dispersible;
Whether the product was applied and removed as claimed;
Whether an enzyme actually loosened nits;
Whether the claims were anticipated or obvious; and
Whether the specification enabled the full breadth of the surfactant and enzyme classes.

Does the patent create manufacturing or geographic barriers?

No current US manufacturing barrier remains under this patent. The patent’s territorial rights were limited to the United States. Foreign counterparts, if any, would have required separate analysis of filing, grant, lapse, and expiration dates.

The patent did not claim a narrowly defined manufacturing process. Its principal barriers were product composition and treatment-use limitations. A manufacturer could historically have pursued design-around strategies by:

Using a nonqualifying oil-based occlusive system;
Omitting the claimed surfactant;
Using a non-liquid delivery format;
Avoiding the claimed enzyme;
Modifying the treatment protocol;
Avoiding the claimed scalp or animal indication; or
Developing a formulation that did not form a substantially air-impermeable layer.

Those strategies remain relevant to understanding the patent’s original scope but are no longer needed to avoid the expired US patent.

Key Takeaways

US Patent 5,858,383 covers surfactant-containing, water-dispersible occlusive liquids for killing ectoparasites and removing the residue.
Claims 1 and 9 are method claims; claim 11 is an enzyme-containing composition claim.
The patent reaches animal skin broadly and human head-lice treatment specifically.
Dependent claims address enzymes, thickeners, gums, viscosity, overnight contact, rinsing, and enzyme concentration.
The patent issued January 12, 1999, and its ordinary US term expired by 2016.
It has no current blocking effect on US products.
The patent is not itself an Orange Book listing or FDA exclusivity record.
Current commercial risk is more likely to arise from later patents covering specific lice-treatment actives, silicone systems, enzyme formulations, delivery devices, or manufacturing processes.
Historical validity issues would have centered on anticipation, obviousness, claim construction, and enablement.
The expired patent remains relevant as prior art and as a technical disclosure, not as an enforceable exclusion right.

FAQs About US Patent 5,858,383

Is US Patent 5,858,383 still enforceable?

No. The patent’s ordinary US term ended by 2016. It does not impose a current patent injunction or launch bar.

Does the patent cover dimethicone lice treatments?

Not automatically. Dimethicone products would need to satisfy every applicable claim element, including the water-soluble or water-dispersible liquid requirement and the listed surfactant limitation. In any event, this patent is expired.

Does claim 11 cover a lice product without an enzyme?

Generally no. Claim 11 expressly requires an effective quantity of at least one enzyme that loosens nits from skin and hair. Claims 1 and 9 do not contain that enzyme requirement.

Can a company rely on this patent as FDA approval?

No. A patent grants exclusionary rights; it does not establish FDA approval, an OTC monograph status, an NDA, or an Orange Book listing.

Are foreign equivalents of US Patent 5,858,383 still active?

US expiration does not determine foreign status. Any international family members would require country-by-country review of grant, maintenance, term adjustment, supplementary protection, and lapse records.

References

United States Patent No. 5,858,383, “Treatment of ectoparasites,” issued January 12, 1999. United States Patent and Trademark Office.
35 U.S.C. § 103, Conditions for patentability; non-obvious subject matter.
35 U.S.C. § 154, Contents and term of patents; 35 U.S.C. § 156, Extension of patent term.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. Orange Book.
U.S. Food and Drug Administration. (n.d.). 21 C.F.R. Part 358: External analgesic drug products for over-the-counter human use and applicable OTC drug-labeling provisions.
21 U.S.C. § 355(j), Abbreviated applications and patent certifications.
35 U.S.C. § 286, Time limitation on damages.

Details for Patent: 5,858,383

Summary for Patent: 5,858,383