United States Patent 6,743,442: Scope, Claim Construction, Expiration, and Pharmaceutical Patent Landscape

U.S. Patent No. 6,743,442 covers sustained-release oral dosage forms made by hot-melt extrusion of an active pharmaceutical ingredient with hydrophobic polymers and wax-like fusible carriers. The broadest independent formulation claim requires a specific combination of composition, extrusion process, dosage-unit structure, and 8-to-24-hour release performance. The patent is directed particularly to opioid formulations, including hydromorphone, morphine, oxycodone, hydrocodone, and tramadol.

The patent’s practical significance is now historical. Its enforceable term has expired under the 20-year patent-term framework applicable to modern utility patents, subject to any patent-term adjustment or terminal-disclaimer data in the USPTO file. The claims therefore remain relevant for prior-art, freedom-to-operate history, and patent-landscape analysis, but they do not ordinarily create a current U.S. blocking right.

What technology does U.S. Patent 6,743,442 protect?

The patent protects a hydrophobic matrix sustained-release system manufactured by extrusion. The core technology combines:

A therapeutically active agent.
One or more hydrophobic release-retarding materials.
A hydrophobic fusible carrier.
Thermal or melt processing in an extruder.
Formation of a strand or extrudate.
Cutting or dividing the strand into multiparticulates.
Incorporation into capsules or tablets.
Sustained release over approximately 8 to 24 hours.

The hydrophobic materials are selected from alkylcelluloses, acrylic polymers, or combinations of those materials. The fusible carrier is selected from waxes, fatty acids, fatty alcohols, or mixtures of those materials and must have a melting point of approximately 30°C to 200°C.

The claims are directed to a matrix system rather than to a drug-specific molecular entity. The same claim architecture can potentially cover multiple opioid APIs and, under claim 1, non-opioid active agents as well.

How broad is independent claim 1?

Claim 1 is the principal composition claim. A product must satisfy all of the following limitations:

Claim element	Required limitation
Dosage form	Sustained-release pharmaceutical formulation
Manufacturing structure	Extruded blend
Active ingredient	Therapeutically active agent
Hydrophobic material	Alkylcellulose, acrylic polymer, or mixture
Fusible carrier	Wax, fatty acid, fatty alcohol, or mixture
Carrier melting point	Approximately 30°C to 200°C
Processing	Ingredients mixed and extruded through an extruder
Dose structure	Extruded blend divided into a unit dose
Release period	Approximately 8 to 24 hours
Therapeutic function	Effective amount producing the desired therapeutic effect

The claim is narrower than a generic sustained-release formulation claim because it requires extrusion and a defined hydrophobic carrier system. A formulation using only direct compression, aqueous granulation, spray drying, fluid-bed coating, or solvent evaporation would not literally satisfy the extrusion limitation.

A formulation could still present an infringement issue under the doctrine of equivalents if it uses a substantially equivalent manufacturing operation, but the extrusion limitation creates a significant noninfringement pathway for products manufactured by materially different processes.

What formulation ingredients are protected?

Hydrophobic polymers

The claim expressly identifies:

Alkylcelluloses, such as ethylcellulose.
Acrylic polymers.
Mixtures of alkylcelluloses and acrylic polymers.

The claim does not require a particular polymer grade, viscosity, substitution level, or commercial brand. A formulation using a chemically different hydrophilic polymer as the primary matrix former would fall outside the literal polymer category unless another listed hydrophobic component is present.

Hydrophobic fusible carriers

The listed carriers include:

Natural waxes.
Synthetic waxes.
Fatty acids.
Fatty alcohols.
Mixtures of those materials.

The 30°C-to-200°C melting-point range is material. A carrier outside that range may avoid literal infringement of claim 1, although the analysis would depend on the full claim set and whether the carrier is characterized as an equivalent.

Optional excipients

Claims 20 through 23 add:

Plasticizers, including diethyl phthalate, tributyl citrate, and triacetin.
Lubricants, including magnesium stearate, stearic acid, and talc.

These claims do not define the full patent. They add narrower alternatives to the broad formulation claim. A product does not need to contain a plasticizer or lubricant to implicate claim 1.

What dosage forms and particle dimensions are covered?

Claims 2 and 3 add physical dimensions to the extrudate:

Feature	Claimed range
Multiparticulate length	Approximately 0.1 to 5 mm
Extrudate diameter	Approximately 0.1 to 5 mm
Method-claim strand diameter	Approximately 0.1 to 3 mm

The claims contemplate a strand-shaped matrix cut into non-spheroidal multiparticulates. This is an important distinction from spherical pellets produced by extrusion-spheronization. A product made as a spherical pellet may not meet the literal “strand” or “non-spheroidal multiparticulate” limitations in the narrower claims.

Claims 7 and 19 cover gelatin capsules containing the multiparticulates. Claim 8 covers compression of the multiparticulates into a tablet. The patent therefore reaches both capsule and tablet presentations, provided the underlying extruded matrix and release limitations are satisfied.

Which opioid drugs are included?

Claims 4 through 6 and 18 expressly identify opioid analgesics. The listed compounds include:

Hydromorphone.
Morphine.
Oxycodone.
Oxymorphone.
Hydrocodone.
Codeine.
Dihydrocodeine.
Dihydromorphine.
Tramadol.
Fentanyl.
Methadone.
Meperidine.
Buprenorphine.
Pentazocine.
Propoxyphene.
Other listed opioid compounds and pharmaceutically acceptable salts.

Claim 6 narrows the opioid group to a shorter list that includes the commercially important drugs hydromorphone, morphine, oxycodone, hydrocodone, oxymorphone, and tramadol.

The opioid listing does not itself create a patent right in any one opioid molecule. The protection concerns the combination of the opioid with the claimed release matrix and extrusion process.

What dose ranges are covered?

Claims 24 through 34 specify dose ranges for three opioid APIs:

API	Claimed unit-dose range
Hydromorphone	Approximately 4 mg to 64 mg
Morphine	Approximately 5 mg to 800 mg
Oxycodone	Approximately 5 mg to 400 mg

These limitations are useful for claim scope but create narrower coverage. A product outside the specified dose range may still fall within broader claims 1, 4, 5, 6, 7, 8, 10, or 17 if all applicable elements are present.

Several issued claims contain apparent typographical or dependency defects. For example, claim 28 refers to claim 32 even though claim 32 is not the expected method claim, and claims 32 and 33 use “dosage from” rather than “dosage form.” Those defects can affect construction and enforceability, but they do not necessarily invalidate the broader correctly structured claims.

What release profiles are protected?

Claims 11, 12, 13, 14, 15, and 16 add performance limitations.

In-vitro release profile

Claim 11 requires specified release windows under a USP Paddle or Basket test at 100 rpm, 900 mL aqueous buffer, pH 1.6 to 7.2, and 37°C:

Time	Opioid released
1 hour	Approximately 1% to 42.5%
2 hours	Approximately 5% to 65%
4 hours	Approximately 15% to 85%
6 hours	Approximately 20% to 90%
12 hours	Approximately 35% to 95%
18 hours	Approximately 45% to 100%
24 hours	Approximately 55% to 100%

Claim 16 provides a faster early-release profile:

Time	Opioid released
1 hour	Approximately 12.5% to 42.5%
2 hours	Approximately 25% to 65%
4 hours	Approximately 45% to 85%
8 hours	Greater than approximately 60%

The release claims are range claims. A product must be tested under substantially comparable conditions before a reliable infringement conclusion can be reached. Differences in buffer pH, agitation speed, apparatus, sampling, dose strength, particle size, or test method can materially affect the result.

Pharmacokinetic profile

Claims 12 through 15 require in-vivo characteristics, including:

Peak plasma level at approximately 2 to 8 hours.
W50 of approximately 4 to 12 hours.
Rapid initial plasma-concentration rise.
Absorption half-life of approximately 1 to 8 hours in the fasted state.

These claims create evidentiary issues because infringement depends on pharmacokinetic testing rather than solely on formulation composition. Food effects, opioid salt form, dose strength, patient population, and study design can affect the measured result.

What manufacturing process is claimed?

Independent method claim 17 covers a sequence of manufacturing steps:

Blend the active ingredient with the hydrophobic material and fusible carrier in an extruder.
Heat the blend sufficiently to soften it.
Extrude the blend as a strand.
Maintain a strand diameter of approximately 0.1 to 3 mm.
Cool the strand.
Divide it into non-spheroidal multiparticulates approximately 0.1 to 5 mm long.
Divide the multiparticulates into unit doses.
Produce 8-to-24-hour sustained release.

A manufacturer may avoid literal claim 17 by using:

A solvent-based process.
Direct compression.
Fluid-bed coating.
Spray drying.
A non-extrusion melt process.
Extrusion followed by spheronization rather than cutting into non-spheroidal units.
A strand diameter or particle length outside the claimed ranges.

The process claim is narrower than a composition claim because every required process step must be practiced. It can nevertheless be commercially important if the accused product is manufactured using the claimed hot-melt extrusion sequence.

When did U.S. Patent 6,743,442 lose exclusivity?

U.S. Patent 6,743,442 is an issued utility patent subject to the 20-year term under 35 U.S.C. § 154, measured from the effective nonprovisional filing date, with adjustments for patent-term adjustment and possible terminal disclaimers (U.S. Patent and Trademark Office, n.d.-a).

Because the patent issued in 2004 and claims priority to an earlier U.S. filing, its ordinary patent term ended approximately two decades after the earliest effective nonprovisional filing, not 20 years after issuance. The patent is therefore expired by 2026. Any patent-term adjustment would have been reflected in the USPTO patent record and would not ordinarily extend the patent into the current decade.

The expiration of this patent does not eliminate other patents covering:

A particular opioid product.
A specific dosage strength.
A particular abuse-deterrent formulation.
A manufacturing process.
A crystalline or salt form.
A method of treatment.
A device or delivery system.
A later-developed formulation.

What is the Orange Book status of U.S. Patent 6,743,442?

A patent number alone does not establish Orange Book listing. The FDA Orange Book lists patents in connection with approved drug products and their relevant NDA or supplement, not as a universal database of all pharmaceutical patents (FDA, n.d.-a).

U.S. Patent 6,743,442 is a formulation-platform patent. Its inclusion in an Orange Book entry would depend on whether an NDA holder submitted it for a specific approved product and whether FDA accepted the listing under the applicable statutory and regulatory criteria.

For current generic-entry analysis, an expired patent cannot ordinarily support a new Paragraph IV certification as an enforceable barrier. A generic applicant could still address the patent in its ANDA patent certifications if the reference product’s regulatory history includes the patent, but the commercial blocking effect would be limited by expiration.

Are Paragraph IV challenges or generic litigation relevant?

Paragraph IV litigation is relevant historically where a generic applicant challenged a listed patent as invalid, unenforceable, or not infringed under the Hatch-Waxman Act (21 U.S.C. § 355(j)(2)(A)(vii)(IV)).

For this patent, the principal historical challenge points would have been:

Whether the accused product used extrusion.
Whether its matrix contained a listed hydrophobic material.
Whether its carrier fell within the 30°C-to-200°C melting range.
Whether the product supplied 8-to-24-hour release.
Whether its multiparticulates were strand-derived and non-spheroidal.
Whether the product met the claimed dissolution or pharmacokinetic ranges.
Whether the claims were obvious over earlier wax-matrix, acrylic-polymer, and extrusion references.
Whether the claims were enabled across the full opioid genus.

As of the patent’s expiration, a new Paragraph IV challenge would generally have little practical value unless the patent remained relevant to a pending regulatory exclusivity issue or historical damages dispute.

How strong was the patent estate?

The patent’s historical strength was mixed.

Strengths

Independent claim 1 combines composition, process, dosage-unit, and release limitations.
The claims cover several commercially important opioid APIs.
The extrusion process creates a concrete manufacturing limitation.
Claims 11 and 16 define measurable dissolution windows.
Claims 24 through 26 address commercially relevant dose ranges for hydromorphone, morphine, and oxycodone.
The formulation can be presented in either capsules or tablets.

Weaknesses

The active-ingredient genus is extremely broad.
Hydrophobic matrices using waxes and alkylcellulose were established formulation technologies.
Extrusion and hot-melt processing were known pharmaceutical manufacturing techniques.
The 8-to-24-hour release limitation may be difficult to distinguish from routine optimization.
Pharmacokinetic claims can be vulnerable to variability in study conditions.
Several dependent claims contain apparent drafting or dependency errors.
The claim set does not, by itself, protect a specific commercial product or opioid molecule.
The patent has expired, eliminating current injunctive leverage.

The strongest historical claims were likely the narrower claims combining a defined opioid, dose range, extruded strand-derived multiparticulate, and specified release profile. The broadest claims were more exposed to anticipation and obviousness arguments based on prior sustained-release matrix systems.

How does this patent compare with competing opioid patent estates?

Patent category	Typical protection	Relevance to U.S. 6,743,442
API patents	New chemical entity or salt	Generally separate; the patent does not claim opioid molecules
Conventional controlled-release patents	Matrix, coating, osmotic, or multiparticulate delivery	Overlapping technical field
Abuse-deterrent patents	Physical or chemical resistance to tampering	Usually distinct from the claims here
Method-of-use patents	Treatment of pain or dosing regimens	Separate from the formulation and extrusion claims
Manufacturing patents	Granulation, extrusion, coating, or compression	Potentially overlapping with claim 17
Product-specific patents	Particular marketed formulation	May create later or narrower barriers
Regulatory exclusivity	NCE, orphan, pediatric, or other FDA exclusivity	Separate from patent rights

This patent should be analyzed as one layer of a broader opioid product estate. A product can be outside this patent and still face other formulation, process, method-of-use, or abuse-deterrence patents.

What generic launch risks existed?

Before expiration, a generic manufacturer would have faced five principal risks:

Composition risk. Use of ethylcellulose or an acrylic polymer with a wax, fatty acid, or fatty alcohol could satisfy the core matrix limitations.
Process risk. Hot-melt extrusion followed by strand cutting could implicate claim 17.
Dissolution risk. A product designed to match an extended-release reference product could fall within claims 11 or 16.
Product-development risk. Changing the particle geometry or manufacturing route could alter bioequivalence and regulatory performance.
Patent-estate risk. Avoiding this patent would not necessarily avoid other patents associated with the reference product.

Current generic launch risk from this patent alone is low because the patent is expired. The relevant commercial risks now are regulatory approval, bioequivalence, controlled-substance requirements, manufacturing validation, and other unexpired patents.

What manufacturing and intellectual-property barriers remain?

The patent does not eliminate manufacturing barriers. A generic or follow-on manufacturer must still control:

Melt viscosity.
Extruder temperature and residence time.
Strand diameter.
Cooling conditions.
Cutting uniformity.
Drug distribution within the matrix.
Dose uniformity across multiparticulates.
Dissolution reproducibility.
Scale-up from laboratory to commercial extrusion.
API degradation during heating.
Abuse-deterrence and tamper-resistance requirements, where applicable.

The key IP barriers may now lie in later patents covering specific products, abuse-deterrent technologies, polymer combinations, tablet architecture, release profiles, or manufacturing controls.

Key Takeaways

U.S. Patent 6,743,442 covers hydrophobic sustained-release formulations made by extrusion.
Claim 1 requires an active ingredient, alkylcellulose or acrylic polymer, hydrophobic fusible carrier, extrusion, unit dosing, and 8-to-24-hour release.
The patent expressly reaches opioid products containing hydromorphone, morphine, oxycodone, hydrocodone, oxymorphone, tramadol, and other listed opioids.
Claims 2, 3, 7, 8, 11, 16, and 17 add particle size, dosage form, dissolution, and manufacturing limitations.
The patent is expired under the applicable 20-year utility-patent term framework.
It does not independently establish current Orange Book protection or current generic-entry blocking rights.
Historical infringement risk centered on hot-melt extrusion, wax-polymer matrices, strand-cut multiparticulates, and claimed dissolution or pharmacokinetic profiles.
Current product risk must be assessed against later patents and FDA regulatory requirements, not this expired patent alone.

FAQs

Does U.S. Patent 6,743,442 cover OxyContin specifically?

No. The claims cover opioid-containing sustained-release matrices, including oxycodone formulations, but they do not claim the OxyContin brand, a particular oxycodone product, or oxycodone as a chemical entity.

Can a formulation avoid the patent by using direct compression?

A direct-compression product would generally avoid the literal extrusion limitations in claims 1 and 17. It could still require analysis under other claims or other patents.

Does the patent cover coated pellets?

Not necessarily. The claims emphasize an extruded strand divided into multiparticulates. Coated pellets made without the claimed extrusion and strand-cutting process may fall outside the literal scope.

Are the dissolution ranges mandatory for every claim?

No. The dissolution ranges appear in narrower dependent claims 11 and 16. They are not required for every formulation falling within claim 1.

Is a biosimilar analysis relevant to this patent?

No. The patent concerns small-molecule pharmaceutical formulations, including opioids. Biosimilar statutes apply to biological products, not conventional opioid drug products.

References

Food and Drug Administration. (n.d.-a). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
United States Congress. (2011). 21 U.S.C. § 355: New drugs. https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title21-section355
United States Congress. (2011). 35 U.S.C. § 154: Contents and term of patent; provisional rights. https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title35-section154
United States Patent and Trademark Office. (n.d.-a). Patent term adjustment. https://www.uspto.gov/patents/laws/patent-term-adjustment
United States Patent and Trademark Office. (2004). U.S. Patent No. 6,743,442, sustained release formulations.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	257375	⤷ Start Trial
Austria	356616	⤷ Start Trial
Austria	357909	⤷ Start Trial
Austria	397441	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,743,442

Summary for Patent: 6,743,442