United States Patent 6,709,676: Desloratadine-Pseudoephedrine Bilayer Patent Scope and Landscape

U.S. Patent No. 6,709,676 covered bilayer tablets combining desloratadine with pseudoephedrine, including formulations designed to protect desloratadine from degradation while providing immediate desloratadine release and sustained pseudoephedrine release. The patent was assigned to Schering Corporation and issued on March 23, 2004. Its U.S. patent term expired in 2022, leaving no live U.S. patent exclusivity under this patent.

The commercial product most closely associated with the claimed technology was Clarinex-D, containing desloratadine and pseudoephedrine sulfate. The patent’s historical importance was greatest for the 2.5 mg/120 mg and 5 mg/120 mg bilayer presentations.

What does U.S. Patent 6,709,676 protect?

The patent protects a physical dosage-form architecture rather than desloratadine or pseudoephedrine as chemical entities.

The core combination requires:

A first tablet layer containing desloratadine.
A second tablet layer containing pseudoephedrine or a pharmaceutically acceptable pseudoephedrine salt.
A formulation arrangement that limits desloratadine degradation.
In several claims, a specified desloratadine dissolution profile.
In narrower claims, immediate release of desloratadine and sustained release of pseudoephedrine.

The independent composition claims use the term “comprising.” That language generally permits additional ingredients, excipients, coatings, processing aids and other components, provided the accused product still contains every required claim element.

Claim architecture

Claim group	Principal subject matter	Relative breadth
Claims 1-10	Bilayer composition using a water-insoluble basic calcium, magnesium or aluminum salt, antioxidants, or both	Broad
Claims 11-16	Bilayer composition requiring a water-insoluble basic salt in the desloratadine layer	Broad to intermediate
Claims 17-23	Antioxidants in both layers and degradation control	Intermediate
Claims 24-25	Immediate-release desloratadine layer and sustained-release pseudoephedrine layer, with dissolution and degradation limits	Intermediate
Claims 26-27	Specific 2.5 mg desloratadine formulation and 120 mg pseudoephedrine sulfate formulation	Narrow
Claims 28-29	2.5 mg desloratadine, 120 mg pseudoephedrine and basic-salt stabilization	Narrow to intermediate
Claims 30-31	5 mg desloratadine, 120 mg pseudoephedrine and antioxidant stabilization	Narrow to intermediate
Claims 32-33	Specific 5 mg desloratadine/120 mg pseudoephedrine formulation	Narrow
Claims 34-35	Alternative 5 mg formulation using edetate disodium and citric acid	Narrow
Claims 36-37	Alternative 2.5 mg formulation using edetate disodium and citric acid	Narrow
Claims 38-41	Treatment methods using the bilayer composition	Use-based

How broad is claim 1 of U.S. Patent 6,709,676?

Claim 1 is the principal broad composition claim. It requires a bilayer solid composition with:

Desloratadine in the first layer;
Pseudoephedrine or a pharmaceutically acceptable salt in the second layer;
A desloratadine-protective water-insoluble basic salt, an antioxidant, or both;
A pharmaceutically acceptable excipient in the pseudoephedrine layer.

The claim does not require:

A specific desloratadine dose;
A specific pseudoephedrine dose;
Immediate release of desloratadine;
Sustained release of pseudoephedrine;
A specific tablet weight;
A specific manufacturing process;
The exact excipients used in the examples;
A particular brand or therapeutic indication.

The alternative stabilizer language is commercially significant. A competing formulation could fall within claim 1 through either of two routes:

Use of a water-insoluble basic calcium, magnesium or aluminum salt; or
Use of one or more antioxidants.

Because claim 1 is written in the alternative, avoiding one stabilizer category would not necessarily avoid infringement if the formulation uses another claimed category.

What formulations are protected by the patent?

The patent covers both broad formulation classes and specific tablet recipes.

Basic-salt formulations

Claims 1, 11 and 28 focus on a desloratadine layer containing a water-insoluble basic salt of calcium, magnesium or aluminum. Dibasic calcium phosphate is the most evident example in the disclosed formulations.

The claim language does not appear limited to dibasic calcium phosphate. Depending on claim construction and the relevant specification disclosure, other pharmaceutically acceptable water-insoluble basic salts could potentially fall within the literal scope.

The basic salt must be present in a “desloratadine-protective amount.” That functional limitation creates an analytical issue. A product assessment would require evidence that the quantity and identity of the salt actually protects desloratadine against degradation under the patent’s relevant conditions.

Antioxidant formulations

Claims 1, 5, 6, 10 and 17-23 cover antioxidants as stabilizing agents. Claim 5 specifies approximately 0.1% to 10% antioxidant in the first layer. Claims 17 and 24 also address degradation control across the bilayer formulation.

Claim 17 is narrower than claim 1 because it requires:

At least one antioxidant in the first layer;
At least one antioxidant in the second layer; and
Total desloratadine degradation products of no more than approximately 2% by weight.

Immediate-release and sustained-release formulations

Claim 24 is commercially important because it expressly requires:

An immediate-release first layer containing desloratadine; and
A sustained-release second layer containing pseudoephedrine.

It also requires:

Total desloratadine degradation products of no more than approximately 2% by weight; and
At least approximately 80% desloratadine dissolution in 0.1N hydrochloric acid at 37°C in approximately 45 minutes.

This claim maps closely to the product concept of rapid antihistamine release combined with extended decongestant release.

Specific 2.5 mg/120 mg formulation

Claim 26 recites a 450 mg total bilayer tablet containing:

2.5 mg micronized desloratadine;
Corn starch;
Dibasic calcium phosphate dihydrate;
Microcrystalline cellulose;
Talc;
Colorant; and
120 mg pseudoephedrine sulfate in a sustained-release layer containing hydroxypropyl methylcellulose, microcrystalline cellulose, povidone, silicon dioxide and magnesium stearate.

Claim 28 separately captures a 2.5 mg desloratadine/120 mg pseudoephedrine composition using the basic-salt stabilization concept.

Specific 5 mg/120 mg formulation

Claim 32 recites a 450 mg tablet containing:

5 mg micronized desloratadine;
120 mg pseudoephedrine sulfate;
Dibasic calcium phosphate dihydrate;
Hydroxypropyl methylcellulose;
Microcrystalline cellulose;
Povidone;
Silicon dioxide; and
Magnesium stearate.

Claim 30 separately covers a 5 mg desloratadine/120 mg pseudoephedrine formulation using antioxidant protection.

Chelator and acid formulations

Claims 34 and 36 describe alternative formulations using:

Edetate disodium;
Citric acid;
Microcrystalline cellulose;
Corn starch;
Stearic acid; and
A colorant in the desloratadine layer.

These claims are narrower because they recite detailed ingredient quantities and a specific tablet construction.

The supplied claim text contains apparent transcription errors. In particular, claim 35 appears to depend on claim 33 even though its subject matter corresponds more naturally to claim 34. Claim 7 also contains a typographical error in “pharmaceutically acceptableater.” The issued patent and USPTO file history control over the reproduced text.

What are the key functional limitations?

Desloratadine dissolution

Claims 3, 13, 19, 24, 27, 29, 31, 33 and 37 require that at least approximately 80% of desloratadine dissolve in 0.1N hydrochloric acid at 37°C in approximately 45 minutes.

This limitation is not satisfied merely because a formulation is described as “immediate release.” A product-specific dissolution test would be required. The relevant assessment would include:

The test medium;
Temperature;
Sampling time;
Apparatus and agitation conditions;
Assay method;
Whether the result is measured per tablet or as a batch average; and
Whether “about 45 minutes” permits a defined analytical tolerance.

Desloratadine degradation

Several claims require total desloratadine degradation products of no more than approximately 2% by weight. Claims 25 and related embodiments reduce the threshold to approximately 1.5%.

The limitation creates two separate infringement questions:

Whether the accused product contains the required bilayer and active ingredients; and
Whether the product meets the degradation threshold under the applicable analytical method.

A formulation could contain the same active ingredients and release profile but fall outside a claim if its measured degradation products exceed the stated threshold. Conversely, a formulation using different stabilizers could remain within a broad claim if it satisfies the structural and functional limitations.

When did U.S. Patent 6,709,676 lose exclusivity?

Event	Date
Earliest identified priority date	May 25, 2001
U.S. nonprovisional filing	May 24, 2002
U.S. publication	December 5, 2002
Patent issued	March 23, 2004
Standard 20-year term measured from nonprovisional filing	May 24, 2022
U.S. patent status	Expired

The patent’s enforceable term ended in 2022, subject to any patent-term adjustment or disclaimer recorded in the official USPTO patent record. Public patent databases identify U.S. Patent 6,709,676 as expired. The patent therefore does not presently block an ANDA applicant from marketing a product solely because the product practices the expired claims.

Patent expiration does not eliminate the historical relevance of the patent. It remains relevant to:

Earlier Paragraph IV disputes;
Settlement timing;
Prior generic launch analysis;
Damages periods;
Foreign patent family review; and
Freedom-to-operate analysis involving related continuation or formulation patents.

What was the Orange Book status of the patent?

The patent was associated with the desloratadine/pseudoephedrine product category marketed by Schering-Plough under the Clarinex-D brand. Clarinex-D products used desloratadine with pseudoephedrine sulfate, including 2.5 mg/120 mg and 5 mg/120 mg presentations. FDA product labeling identifies the combination as an immediate-release antihistamine component paired with extended-release pseudoephedrine technology.[1]

The Orange Book historically listed patents associated with approved desloratadine/pseudoephedrine drug products. U.S. Patent 6,709,676 was the principal formulation patent relevant to the bilayer combination. Following its 2022 expiration, the patent ceased to provide a current patent-based barrier to generic approval or launch.

The relevant regulatory distinction is:

FDA approval of a generic product depends on the approved reference listed drug, applicable exclusivity, labeling, bioequivalence and patent certifications.
Patent expiration removes the legal barrier created by this patent.
It does not guarantee immediate generic market entry because other patents, regulatory exclusivities, manufacturing controls or commercial decisions may remain relevant.

Were there Paragraph IV challenges or patent litigation?

The claims alone do not establish a litigation history. Public patent and FDA records should be read together for any historical Paragraph IV certification, ANDA litigation, settlement agreement or launch restriction involving a particular generic applicant.

For this patent, the principal legal exposure was likely concentrated in ANDA filings directed to:

The 2.5 mg/120 mg Clarinex-D presentation;
The 5 mg/120 mg presentation;
Bilayer tablets with immediate-release desloratadine;
Sustained-release pseudoephedrine sulfate; and
Desloratadine stabilization and degradation specifications.

A Paragraph IV certification against an Orange Book-listed patent could have triggered an infringement action under 35 U.S.C. §271(e)(2). A timely suit could have created a statutory 30-month stay of FDA approval, unless the stay was shortened, terminated or otherwise resolved.[2]

The patent’s expiration date means any historical litigation is no longer a current barrier to launch under this patent. A settlement that delayed generic entry until patent expiry would have no continuing exclusionary effect after expiry, although settlement terms may remain relevant to antitrust review or historical damages analysis.

How strong was the patent estate?

Historical strength

The patent had meaningful historical coverage because claim 1 reached a wide range of bilayer compositions without requiring exact ingredient quantities. The alternative use of basic salts or antioxidants increased formulation flexibility.

Its strongest practical features were:

A clear bilayer structure;
Specific desloratadine and pseudoephedrine actives;
A commercially recognizable 2.5 mg/120 mg dosage;
A commercially recognizable 5 mg/120 mg dosage;
Immediate-release and sustained-release functionality;
Quantified dissolution performance; and
Quantified degradation limits.

Weaknesses and design-around points

The estate also had several limitations:

All composition claims require a bilayer solid composition.
The narrower claims depend on specific dose levels or excipient systems.
Dissolution and degradation limitations require reproducible testing.
A monolithic tablet, capsule, multiparticulate system or separate dosage units could potentially avoid the bilayer limitation, subject to claim construction and other patents.
A formulation that uses different release technology may avoid claims requiring an immediate-release first layer and sustained-release second layer.
The patent did not claim desloratadine or pseudoephedrine broadly as active ingredients.

The patent’s strength is now historical rather than blocking. An expired formulation patent cannot support a current injunction against a new generic product.

How does this patent compare with biosimilar and generic risk?

This is a small-molecule generic issue, not a biosimilar issue.

Desloratadine and pseudoephedrine sulfate are chemically defined small molecules. A competing applicant would generally use the ANDA pathway rather than the biosimilar pathway under the Public Health Service Act. Relevant regulatory issues include:

Pharmaceutical equivalence;
Bioequivalence;
Immediate-release desloratadine performance;
Extended-release pseudoephedrine performance;
Stability;
Dissolution testing; and
Labeling compatibility.

There is no biologic interchangeability or biosimilar substitution issue for this product.

What generic launch scenarios existed?

Launch before patent expiry

Before May 2022, a generic applicant could have pursued:

A Paragraph IV challenge;
A non-infringement position based on a non-bilayer dosage form;
A design-around using separate immediate- and extended-release units;
A formulation that did not meet the claimed dissolution profile;
A formulation outside the claimed degradation threshold; or
A different stabilizer and release system.

A successful Paragraph IV challenge could have enabled earlier launch. A settlement could have established a negotiated entry date.

Launch after patent expiry

After May 2022, a generic applicant no longer needed to avoid U.S. Patent 6,709,676 for patent-term reasons. The principal remaining issues would be FDA requirements, any other unexpired patents, manufacturing capability and commercial demand.

The most commercially direct generic target would be a 2.5 mg desloratadine/120 mg pseudoephedrine sulfate extended-release tablet corresponding to Clarinex-D 12 Hour. A 5 mg desloratadine product with a different pseudoephedrine strength would require separate regulatory and commercial analysis.

What manufacturing and intellectual-property barriers remain?

The expired patent does not eliminate manufacturing barriers. A generic manufacturer would still need to control:

Layer compression and interfacial adhesion;
Cross-contamination between layers;
Uniformity of the low-dose desloratadine layer;
Pseudoephedrine extended-release kinetics;
HPMC hydration and matrix performance;
Desloratadine oxidation and degradation;
Tablet hardness and friability;
Dissolution reproducibility; and
Stability through the proposed shelf life.

Manufacturing know-how may remain valuable even where patent protection has expired. Trade secrets concerning granulation, compression force, moisture control, coating, blending order and analytical methods may affect commercial entry without creating patent-based exclusivity.

What is the current commercial and geographic exposure?

U.S. exposure under Patent 6,709,676 ended with expiration in 2022. The patent cannot create current U.S. revenue protection.

Foreign family members may have had different:

Filing dates;
Patent-term calculations;
Supplementary protection certificates;
Claim scope;
Opposition outcomes; and
Expiration dates.

A multinational freedom-to-operate review therefore must examine national-phase members separately. U.S. expiration does not establish that every foreign counterpart expired on the same date.

The revenue exposure was historically concentrated in the Clarinex-D franchise. Current exposure depends on whether the product remains marketed, whether generic alternatives have entered, and whether related patents or regulatory barriers exist. Patent 6,709,676 itself no longer supports a U.S. price premium or exclusionary strategy.

Key Takeaways

U.S. Patent 6,709,676 covered bilayer solid compositions combining desloratadine and pseudoephedrine.
Claim 1 broadly required desloratadine in one layer, pseudoephedrine in another and desloratadine protection through a basic salt, antioxidant or both.
Claims 24 onward focused more specifically on immediate-release desloratadine and sustained-release pseudoephedrine.
Claims 26, 32, 34 and 36 recited detailed 2.5 mg or 5 mg formulations with 120 mg pseudoephedrine sulfate.
The principal functional limitations were at least approximately 80% desloratadine dissolution in 45 minutes and degradation products of no more than approximately 2%.
The patent issued March 23, 2004 and expired in 2022.
It is a small-molecule generic patent, not a biosimilar patent.
Any historical Paragraph IV litigation or settlement no longer creates a current exclusionary right under this patent.
Current commercial analysis must focus on FDA approval requirements, other patent families, manufacturing capability and market demand.

FAQs

Does U.S. Patent 6,709,676 cover Clarinex-D?

Yes. Its claims are directed to the bilayer desloratadine-pseudoephedrine formulation underlying the Clarinex-D product concept.

Can a generic company use the same bilayer structure after patent expiration?

Yes, this patent no longer prevents use of the claimed bilayer structure in the United States. Other unexpired patents or regulatory requirements could still affect launch.

Does the patent cover desloratadine alone?

No. The composition claims require a bilayer containing both desloratadine and pseudoephedrine or a pharmaceutically acceptable pseudoephedrine salt.

Is pseudoephedrine sulfate required?

No. The broad claims cover pseudoephedrine or a pharmaceutically acceptable salt. Several specific claims and examples recite pseudoephedrine sulfate.

What is the main design-around strategy for this patent?

The principal historical design-around options were avoiding the bilayer structure, changing the release architecture, failing to meet the claimed dissolution or degradation thresholds, or using a formulation outside the claimed stabilizer and dosage limitations.

References

U.S. Food and Drug Administration. (n.d.). Clarinex-D prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.
U.S. Patent and Trademark Office. (2004). U.S. Patent No. 6,709,676, pharmaceutical compositions containing desloratadine and pseudoephedrine. U.S. Department of Commerce.
U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, 35 U.S.C. § 271(e)(2).
U.S. Patent and Trademark Office. (n.d.). Patent examination data system and patent term information for U.S. Patent No. 6,709,676. USPTO.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	1110543	⤷ Start Trial	91403	Luxembourg	⤷ Start Trial
European Patent Office	1110543	⤷ Start Trial	CA 2008 00010	Denmark	⤷ Start Trial
European Patent Office	1110543	⤷ Start Trial	300328	Netherlands	⤷ Start Trial
European Patent Office	1110543	⤷ Start Trial	SPC063/2007	Ireland	⤷ Start Trial
European Patent Office	1110543	⤷ Start Trial	08C0004	France	⤷ Start Trial
European Patent Office	1110543	⤷ Start Trial	SPC/GB08/005	United Kingdom	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,709,676

Summary for Patent: 6,709,676