United States Drug Patent 5,702,725: Scope, Claims, Expiration and Hydromorphone Patent Landscape

U.S. Patent No. 5,702,725 covers an osmotic, controlled-release hydromorphone dosage form. Its core technology combines hydromorphone with a medium-molecular-weight poly(alkylene oxide), polyvinylpyrrolidone and, in the principal dosage-form claims, a high-molecular-weight expandable polymer, an osmotic agent, a semipermeable wall and an outlet passageway. The patent is associated with the ALZA osmotic-delivery platform and is historically relevant to extended-release hydromorphone products such as Palladone.

The patent term has expired. U.S. Patent 5,702,725 is therefore not a current U.S. patent barrier to generic hydromorphone products. Its claims remain relevant for historical freedom-to-operate analysis, patent-family mapping, invalidity analysis and understanding the technical architecture of early extended-release hydromorphone products.

What does U.S. Patent 5,702,725 protect?

The patent protects specific hydromorphone controlled-release compositions and dosage forms rather than hydromorphone as a molecule.

Its claims fall into four principal categories:

Claim category	Claims	Principal subject matter
Therapeutic composition	1-4	Hydromorphone combined with poly(alkylene oxide), polyvinylpyrrolidone and optional lubricant
Bilayer composition	5-7	Drug layer plus expandable push layer
Administration method	8-10	Oral administration of sustained-release hydromorphone
Complete osmotic dosage form	11-14	Drug layer, push layer, semipermeable wall and delivery passageway

The broadest commercially important claims are claims 1, 5, 8 and 11. Claims 2-4, 6-7 and 9-14 add narrower formulation, manufacturing or device limitations.

The patent does not claim every extended-release hydromorphone formulation. A competing product would generally need to contain the claimed ingredients and fall within the stated quantity and molecular-weight ranges to present a literal infringement issue.

What are the required technical elements of claim 1?

Claim 1 requires a therapeutic composition for pain relief containing all of the following:

Element	Claimed range
Hydromorphone	1 to 1,000 mg
Poly(alkylene oxide)	25 to 500 mg
Poly(alkylene oxide) molecular weight	150,000 to 500,000
Polyvinylpyrrolidone	1 to 50 mg
Polyvinylpyrrolidone molecular weight	10,000 to 300,000
Lubricant	0 to 7.5 mg

The use of "comprising" makes the claim open-ended. A composition may contain additional excipients and still fall within the claim if it includes the listed elements in the claimed ranges.

The principal limitation is the combination of:

Hydromorphone;
A medium-molecular-weight poly(alkylene oxide);
Polyvinylpyrrolidone; and
The specified quantitative ranges.

Polyethylene oxide would likely be the principal practical example of the claimed poly(alkylene oxide). The claim language is broader than a claim limited expressly to polyethylene oxide, although construction would depend on the patent specification, prosecution history and the technical meaning of the term at the relevant filing date.

How broad is claim 1 against generic hydromorphone products?

Claim 1 is broad at the formulation level but narrow at the ingredient-range level.

A generic hydromorphone product would not necessarily infringe merely because it is extended release. A literal infringement analysis would examine:

Whether hydromorphone is present in the claimed amount;
Whether the formulation contains a poly(alkylene oxide);
Whether the polymer molecular weight falls between 150,000 and 500,000;
Whether polyvinylpyrrolidone is present;
Whether its molecular weight falls between 10,000 and 300,000; and
Whether the quantities fall within the claimed ranges.

A formulation using hydroxypropyl methylcellulose, ethylcellulose, methacrylate polymers, lipids or another release-control matrix without the claimed poly(alkylene oxide)/polyvinylpyrrolidone combination would have a substantial noninfringement position under claim 1.

The claim is less vulnerable to design-around through additional excipients because of the open-ended "comprising" language. Omitting one required polymer, however, would generally remove literal infringement under the claim.

What does claim 2 add for hydromorphone salts?

Claim 2 covers hydromorphone in several salt forms, including:

Hydromorphone salt;
Hydromorphone sulfate;
Hydromorphone hydrochloride;
Hydromorphone trifluoroacetate;
Hydromorphone mucate;
Hydromorphone oleate;
Hydromorphone acetate;
Hydromorphone phosphate; and
Hydromorphone bitartrate.

The claim depends on claim 1 and therefore retains every limitation of claim 1. It does not independently cover a hydromorphone salt without the claimed polymers and quantity ranges.

Hydromorphone hydrochloride is the most commercially relevant form. Claim 2 was drafted to prevent avoidance of the composition claim by selecting a particular pharmaceutically acceptable salt.

What do claims 3 and 4 protect?

Claim 3 adds a compression-force limitation. The composition must be compressed under 1/8 to 10 ton-force of compression.

This limitation is primarily relevant to manufacturing evidence. It is narrower than claim 1 and may be difficult to enforce without batch records, manufacturing-process evidence or reliable forensic testing. A finished tablet alone may not establish the compression force used during manufacture.

Claim 4 requires the composition to be encased in a semipermeable composition with a passageway. This moves the claim from a formulation claim toward an osmotic dosage-form claim. The wall must permit fluid movement, and the passageway must provide the route for hydromorphone delivery.

What is the scope of the bilayer claims 5 through 7?

Claim 5 requires two separate compositions:

A hydromorphone composition with the same core formulation described in claim 1; and
An expandable composition containing a high-molecular-weight poly(alkylene oxide), optional osmagent, hydroxyalkylcellulose and other optional excipients.

The expandable composition must contain:

Element	Claimed range
High-molecular-weight poly(alkylene oxide)	15 to 250 mg
Polymer molecular weight	3,000,000 to 7,500,000
Osmagent	0 to 75 mg
Hydroxyalkylcellulose	1 to 50 mg
Tableting lubricant	0 to 10 mg
Antioxidant	0 to 10 mg
Colorant	0 to 10 mg

This architecture is characteristic of an osmotic push-pull system. The drug layer contains hydromorphone. The push layer absorbs gastrointestinal fluid and expands, forcing the drug composition toward the outlet.

Claim 6 specifies that the two compositions are in a bilayered arrangement and identifies permitted tableting lubricants, including magnesium stearate, calcium stearate, starch and citric acid.

Claim 7 adds the semipermeable coating and passageway. A product lacking a bilayer arrangement or using a non-semipermeable release system would have a stronger noninfringement position against these claims.

What do method claims 8 through 10 cover?

Claim 8 covers orally administering the claimed hydromorphone composition to a patient for sustained pain relief. The claim includes the formulation limitations of claim 1 and adds a functional delivery requirement: hydromorphone must be delivered at a sustained rate over time.

Claim 9 requires an expandable composition in layered contact with the hydromorphone composition.

Claim 10 requires:

An expandable composition containing high-molecular-weight poly(alkylene oxide);
A semipermeable wall permeable to fluid;
The wall surrounding the hydromorphone composition; and
A passageway through the wall for drug delivery.

These claims are directed to use of the dosage form, but they do not create a broad method patent covering all oral sustained-release hydromorphone therapy. The administered product must still satisfy the detailed composition and device limitations.

What does claim 11 add to the osmotic dosage-form protection?

Claim 11 is the most complete device claim. It requires:

A therapeutic hydromorphone composition;
A push composition;
A semipermeable wall surrounding both compositions; and
An exit in the wall for delivery of hydromorphone.

Unlike claim 5, claim 11 expressly recites the wall and exit in one independent dosage-form claim. It is therefore directed to the assembled delivery device rather than merely the two-layer formulation.

Claims 12-14 narrow claim 11 by specifying materials:

Dependent claim	Limitation
12	Hydroxypropylmethylcellulose as the hydroxyalkylcellulose
13	Polyethylene glycol in the semipermeable wall
14	Cellulose acylate, cellulose diacylate or cellulose triacylate in the wall

The wall limitations are important because they identify common components of osmotic tablet coatings. A product using a different wall material may avoid claims 13 and 14, although it could still implicate claim 11 if it satisfies the broader semipermeable-wall language.

What patent protects the OROS-style hydromorphone delivery system?

U.S. Patent 5,702,725 protects a hydromorphone-specific implementation of an osmotic delivery system. The relevant structural features are:

A drug layer;
A swellable push layer;
A semipermeable outer wall;
An osmotic or fluid-driven expansion mechanism; and
A drilled, molded or otherwise formed exit passageway.

The patent should be analyzed together with the broader ALZA osmotic-delivery patent family. Earlier ALZA patents, including U.S. Patent Nos. 4,111,202 and 4,327,725, describe foundational osmotic dosage-form concepts. Those patents are relevant prior-art and technology-background references, but they do not replace the hydromorphone-specific analysis under U.S. Patent 5,702,725.

The existence of earlier osmotic-system patents would not by itself establish invalidity. The validity question would focus on whether the claimed hydromorphone formulation and claimed polymer combinations were novel and nonobvious over the cited prior art.

When did U.S. Patent 5,702,725 lose exclusivity?

U.S. Patent 5,702,725 has expired under the standard U.S. patent-term framework. It is no longer an enforceable patent blocking U.S. manufacture, sale or importation of a product that would have fallen within its claims during the patent term.

The patent issued on December 30, 1997. Its expiration occurred after the applicable 20-year term measured from the relevant U.S. nonprovisional filing date, subject to any patent-term adjustment or other term calculation shown in USPTO records. The patent's current commercial significance is historical rather than exclusionary.

Patent expiration does not eliminate the value of the technical disclosure. It can still affect:

Prior-art analysis;
Patentability of later hydromorphone formulations;
Inventorship and priority disputes;
Interpretation of related patent families;
Product development benchmarking; and
Assessment of whether later patents claim a genuine technical distinction.

What was the FDA and Orange Book status of products associated with this patent?

The patent is associated with the ALZA-controlled-release hydromorphone technology used in the development and commercialization of Palladone. The FDA approved Palladone extended-release hydromorphone capsules in 2004 under NDA 021217. The product was withdrawn from the U.S. market in 2005 after concerns involving alcohol-induced dose dumping and potentially dangerous hydromorphone release.

The withdrawal was a product-safety and commercial event, not a revival or extension of U.S. Patent 5,702,725. An FDA withdrawal does not restore patent rights.

The Orange Book analysis should distinguish among:

The original Palladone NDA;
Listed patents that may have accompanied the NDA;
Any later extended-release hydromorphone products;
Regulatory exclusivity; and
Patent term.

FDA approval, Orange Book listing and patent enforceability are separate issues. An expired patent may remain historically listed in archived regulatory materials, but it cannot create a current patent-based launch prohibition.

Which companies challenged hydromorphone extended-release exclusivity?

The principal commercial competition has involved manufacturers of immediate-release hydromorphone, later extended-release hydromorphone products and generic manufacturers pursuing abbreviated new drug applications.

The best-known branded extended-release product was Exalgo, marketed by Covidien and later associated with Mallinckrodt. Exalgo used an extended-release hydromorphone formulation and was approved through the FDA's new-drug application pathway. Its patent estate was separate from, and later in time than, U.S. Patent 5,702,725.

A Paragraph IV challenge to a later-listed patent would have required a generic applicant to certify that the listed patent was invalid, unenforceable or would not be infringed. Such a challenge would not have revived the expired ALZA patent. The relevant litigation and settlement analysis for Exalgo must therefore be conducted at the later patent-family level rather than by treating U.S. Patent 5,702,725 as the only relevant patent.

What generic launch risks remain after expiration?

The expired patent presents no current U.S. patent-launch risk. Residual risks can arise from other sources:

Risk category	Relevance
Later formulation patents	Potentially material for extended-release or abuse-deterrent products
Method-of-use patents	Usually narrower and dependent on the claimed indication or dosing regimen
Regulatory exclusivity	Relevant only during the applicable FDA exclusivity period
Trade secrets	May affect manufacturing but do not create patent exclusivity
Process patents	Could restrict a particular manufacturing route
Device patents	Relevant if the product uses a protected osmotic architecture
Litigation settlements	May delay launch under later patent estates
Product-specific FDA requirements	May require bioequivalence, food-effect and alcohol-interaction studies

For a conventional generic hydromorphone product, the expired patent is not the principal barrier. For an osmotic, bilayer, abuse-deterrent or multiparticulate product, later patents covering release kinetics, coating systems, manufacturing methods or dosage-form architecture may remain more important.

How strong was the patent estate for U.S. Patent 5,702,725?

The patent had meaningful historical strength against products replicating the claimed osmotic architecture, but its scope was not universal.

Strengths

Multiple independent claim formats covered composition, method and dosage form.
The claims recited specific polymer molecular-weight ranges.
Claim 11 combined the drug layer, push layer, wall and exit.
The open-ended "comprising" language allowed additional excipients.
Dependent claims covered common hydromorphone salts and common osmotic-wall materials.
The specification likely provided a technical framework for implementing the claimed delivery system.

Limitations

The claims required poly(alkylene oxide) and polyvinylpyrrolidone in stated ranges.
The bilayer claims required a high-molecular-weight expandable polymer.
The device claims required a semipermeable wall and an exit.
Claim 3's compression-force limitation could be difficult to prove.
Functional language such as "sustained rate over time" could create construction and proof issues.
Broad terms such as "poly(alkylene oxide)" and "semipermeable composition" could invite claim-construction disputes.
The patent did not cover all hydromorphone extended-release matrices or all oral controlled-release systems.

The patent was strongest against a close copy of the ALZA push-pull osmotic system. It was weaker against matrix tablets, multiparticulate systems, liquid-filled capsules, ion-exchange systems and formulations using different release-controlling polymers.

What manufacturing and IP barriers did the patent create?

The patent's commercial barrier was not limited to formulation ingredients. A replicating manufacturer would also need to address:

High-molecular-weight polymer handling;
Bilayer tablet compression;
Layer adhesion and mechanical integrity;
Semipermeable coating uniformity;
Creation and control of the delivery passageway;
Osmotic swelling performance;
Dose-dumping resistance;
Drug-release reproducibility;
Equipment qualification; and
Process controls for tablet weight, coating thickness and outlet dimensions.

These manufacturing requirements could create practical barriers even after patent expiration. They are not, however, patent exclusivity unless protected by separate unexpired patents or trade secrets.

What is the geographic coverage of U.S. Patent 5,702,725?

The patent provided rights only in the United States. Foreign counterparts, if any, required separate national or regional rights and separate expiration analysis.

A U.S. patent cannot prevent manufacture or sale in Europe, Canada, Japan, China or other jurisdictions unless corresponding patents were granted and remained in force. The global landscape should therefore be reviewed by patent family, national phase, grant status and local term.

The expiration of the U.S. patent does not establish the status of foreign counterparts. It also does not affect regulatory approval requirements in other jurisdictions.

What is the current commercial significance of the patent?

U.S. Patent 5,702,725 is best classified as an expired foundational hydromorphone formulation patent. It has no current Orange Book-style blocking effect by itself, but it remains relevant in three areas:

Historical analysis of Palladone and early extended-release hydromorphone products;
Prior-art review for later osmotic or polymeric hydromorphone patents; and
Technical comparison of generic and branded controlled-release products.

The commercial exposure that once depended on this patent was tied to extended-release hydromorphone, particularly products using an osmotic push-pull platform. Current revenue exposure must instead be assessed against the later patent and regulatory estate for the particular marketed product.

Key Takeaways

U.S. Patent 5,702,725 covers an osmotic controlled-release hydromorphone dosage form.
Claim 1 requires hydromorphone, medium-molecular-weight poly(alkylene oxide), polyvinylpyrrolidone and specified quantity ranges.
Claims 5 and 11 add a bilayer or push-pull architecture with a high-molecular-weight expandable polymer.
Claims 4, 7 and 11-14 require or narrow the semipermeable wall and delivery passageway.
The patent covers a specific formulation and device architecture, not all extended-release hydromorphone products.
The patent has expired and is not a current U.S. launch barrier.
Palladone was FDA-approved in 2004 and withdrawn in 2005 because of alcohol-related dose-dumping concerns.
Later hydromorphone products, including Exalgo, required separate patent and FDA analyses.
Current generic-entry risk depends primarily on later formulation, method-of-use, device, process and regulatory rights.
Foreign patent status must be assessed separately from the U.S. patent.

FAQs about U.S. Patent 5,702,725

Does U.S. Patent 5,702,725 cover Dilaudid?

No. Dilaudid is an immediate-release hydromorphone product. The patent covers specified controlled-release compositions and osmotic dosage forms, not hydromorphone itself or every Dilaudid formulation.

Does the patent cover a hydromorphone matrix tablet?

Not necessarily. A matrix tablet would need to satisfy the specific polymer, molecular-weight and quantity limitations. A formulation using a different release-control system could avoid the claims.

Is U.S. Patent 5,702,725 still listed as an active Orange Book patent?

It may appear in historical regulatory records, but its patent term has expired. An expired listing does not create a current enforceable patent barrier.

Could a generic manufacturer use the same osmotic design today?

The expired patent does not prevent use of the claimed design in the United States. The manufacturer would still need to evaluate later patents, FDA requirements, product safety and manufacturing controls.

Does the patent cover hydromorphone hydrochloride specifically?

Yes, dependent claim 2 identifies hydromorphone hydrochloride, but the claim also requires all limitations inherited from claim 1, including the specified polymers, molecular-weight ranges and quantity ranges.

References

U.S. Patent No. 5,702,725. (1997). Controlled release hydromorphone composition. United States Patent and Trademark Office.
U.S. Patent No. 4,111,202. (1978). Osmotic dispenser. United States Patent and Trademark Office.
U.S. Patent No. 4,327,725. (1982). Osmotic device. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2004). Palladone hydromorphone hydrochloride extended-release capsules, NDA 021217. FDA.
U.S. Food and Drug Administration. (2005). Palladone withdrawal information and alcohol interaction safety communication. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	227575	⤷ Start Trial
Austria	230992	⤷ Start Trial
Australia	2908395	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,702,725

Summary for Patent: 5,702,725