US Patent 6,613,357: Scope, Claim Construction, Expiration, and Fexofenadine-Pseudoephedrine Patent Landscape

US Patent 6,613,357 protects a multipart oral dosage form combining immediate-release fexofenadine with controlled-release pseudoephedrine in a specific osmotic architecture. Its central commercial concept is the 24-hour Allegra-D-type profile: rapid antihistamine delivery and prolonged decongestant delivery from one tablet. The patent issued to ALZA Corporation and has reached the end of its ordinary US patent term. Its claims remain relevant for historical validity, infringement, prosecution, and freedom-to-operate analysis, but they do not provide a currently enforceable US exclusionary right.

What invention does US Patent 6,613,357 protect?

The patent protects an osmotic tablet with four required structural components:

A pseudoephedrine-containing core.
A semipermeable membrane around the core.
A passageway through that membrane.
An external fexofenadine-containing soluble or erodible coating.

The claimed design separates the two pharmacologic release functions. Fexofenadine is released rapidly from the outer coating, while pseudoephedrine is released more slowly through the osmotic core and membrane.

Element	Claimed function
Pseudoephedrine core	Delivers pseudoephedrine over approximately 18 to 24 hours
Semipermeable membrane	Controls water influx and drug release from the core
Passageway	Provides the outlet for osmotic delivery
Inert soluble or erodible coating	Covers the membrane and plugs the passageway before use
Fexofenadine outer coating	Delivers substantially all fexofenadine in less than 90 minutes
Dissolution profile	Defines specified pseudoephedrine release percentages at selected time points

The patent therefore claims more than a simple combination tablet. The dosage form must have a particular layered construction and must meet quantitative release limitations.

The patent disclosure is directed to a combination product containing fexofenadine hydrochloride, an H1 antihistamine, and pseudoephedrine hydrochloride, a sympathomimetic decongestant. The commercial product most closely associated with the technology is Allegra-D 24 Hour, which contains 180 mg of fexofenadine hydrochloride and 240 mg of pseudoephedrine hydrochloride [1, 3].

How many independent claims does US 6,613,357 contain?

The patent has five independent claims: claims 1, 18, 19, 36, and 37.

Claim	Category	Core subject matter
1	Device	First specified pseudoephedrine dissolution profile
18	Method	Treating respiratory-congestion disorders using claims 1-3, 6-7, 12-13, or 15-17
19	Device	Second, more narrowly timed pseudoephedrine profile
36	Device	Third, broader pseudoephedrine dissolution profile
37	Method	Treating respiratory-congestion disorders using claims 19-35 or 36

Claims 2-17 depend from claim 1. Claims 20-35 depend from claim 19. The claim groups largely repeat the same technical limitations under different pseudoephedrine dissolution profiles.

Claims 1, 19, and 36 are the principal product claims. Claims 18 and 37 are method-of-treatment claims, but their practical value is limited because a competing product would generally be analyzed first under the product claims.

What are the key limitations of independent claim 1?

Claim 1 requires all of the following:

An osmotic device.
A pseudoephedrine-containing core.
Controlled pseudoephedrine delivery for approximately 18 to 24 hours.
A semipermeable membrane surrounding the core.
A passageway through the membrane.
An inert soluble or erodible coating surrounding the membrane.
The coating must plug the passageway.
An outer fexofenadine-containing soluble or erodible coating.
Substantially all fexofenadine must be released in less than approximately 90 minutes.
Pseudoephedrine must satisfy five specified release ranges.

The claim 1 release profile is:

Time point	Required pseudoephedrine released
Within 3 hours	10%-25%
Within 7 hours	25%-50%
Within 11 hours	50%-66%
Within 15 hours	66%-79%
Within 23 hours	79%-100%

The claim uses “comprising,” which generally makes it open-ended. A product can contain additional excipients, coatings, or components and still fall within the claim if every required element is present.

The most important limitations are not the presence of the two active ingredients alone. They are the osmotic architecture, the plugged passageway, the rapid-release external fexofenadine layer, and the measured pseudoephedrine dissolution profile.

What do claims 19 and 36 add to the patent scope?

Claims 19 and 36 create separate infringement routes based on different dissolution envelopes.

Claim 19 profile

Claim 19 requires:

Time point	Required pseudoephedrine released
Within 3 hours	9%-11%
Within 5 hours	19%-22%
Within 7 hours	28%-31%
Within 9 hours	35%-40%
Within 11 hours	45%-50%
Within 13 hours	50%-55%
Within 15 hours	60%-65%
Within 23 hours	At least 75%

This claim is more detailed than claim 1 because it includes eight time points. Its narrower ranges may make it easier to distinguish over prior art, but they also create more opportunities for a commercial product to fall outside the claim at one required time point.

Claim 36 profile

Claim 36 requires:

Time point	Required pseudoephedrine released
Within 3 hours	5%-23%
Within 7 hours	20%-52%
Within 11 hours	36%-72%
Within 15 hours	53%-82%
Within 23 hours	At least 75%

Claim 36 has the broadest dissolution ranges of the three independent device claims. It does not expressly require the dosage ranges, excipient classes, or quantitative coating compositions recited in the dependent claims.

From an enforcement perspective, claim 36 is potentially the broadest claim. From a validity perspective, its broad ranges may be more exposed to prior-art combinations involving conventional osmotic pseudoephedrine systems and immediate-release antihistamine coatings.

What formulations are protected by the dependent claims?

The dependent claims narrow the formulation through dose ranges, excipient classes, coating weight, and specific composition ranges.

Active-ingredient amounts

Claims 2 and 20 require:

Pseudoephedrine: approximately 60-240 mg.
Fexofenadine: approximately 60-180 mg.

These ranges encompass the 240 mg pseudoephedrine and 180 mg fexofenadine strengths associated with Allegra-D 24 Hour.

Outer coating weight

Claims 3-5 and 21-23 require the fexofenadine-containing coating to constitute:

At least approximately 25% by weight of the device.
Approximately 25%-40% by weight.
Approximately 30%-40% by weight.

This limitation is commercially significant. A formulation that uses a thin fexofenadine film may avoid these dependent claims even if it satisfies the broader device architecture.

Core and membrane excipients

Claims 12-17 and 30-35 recite combinations of:

Osmagent.
Diluent.
Binder.
Cellulose ester membrane.
Membrane plasticizer.
Water-soluble polymer.
Opaquant.
Filler.
Film-forming polymer.
Disintegrant.

The listed osmაგენტs include sodium chloride, mannitol, sugars, acids, bases, calcium salts, sodium salts, and lactose. The diluent and binder lists are similarly broad.

The membrane is based on a cellulose ester, including cellulose acetate, cellulose acylate, cellulose fatty-acid ester, or cellulose acetate phthalate. Plasticizers include polyethylene glycol, citrate esters, triacetin, propylene glycol, glycerin, sorbitol lactate, ethyl lactate, butyl lactate, ethyl glycolate, and dibutyl sebacate.

The external fexofenadine coating uses a film-forming polymer, such as hydroxypropyl methylcellulose or polyvinylpyrrolidone, together with a disintegrant such as crospovidone, sodium starch glycolate, starch, alginate, or carboxymethylcellulose.

Quantitative excipient embodiments

Claims 15-17 and 33-35 provide three formulation families.

Component	Claim 15 / 33	Claim 16 / 34	Claim 17 / 35
Osmagent	70-90 mg	70-90 mg	70-90 mg
Diluent	30-40 mg	30-40 mg	30-40 mg
Binder	40-60 mg	40-60 mg	40-60 mg
Cellulose ester	35-45 mg	40-50 mg	35-45 mg
Film-forming polymer	20-25 mg	10-20 mg	20-40 mg
Disintegrant	50-70 mg	5-10 mg	20-30 mg
Water-soluble copolymer	Not required	20-30 mg	Not required

These claims are substantially narrower than claims 1, 19, and 36. They may be relevant to a formulation comparison, but they are less likely to capture a product using different excipient quantities or different coating-process parameters.

How should the pseudoephedrine release limitations be construed?

The claims use cumulative dissolution percentages measured after exposure to an aqueous environment. The claim text does not identify the specific dissolution apparatus, medium, agitation speed, temperature, sampling method, or analytical method in the supplied claim set. Those parameters would ordinarily be located in the patent specification, examples, prosecution history, product specifications, or regulatory filings.

The release limitations have four legal effects:

They are express claim limitations.
They require experimental comparison against the claimed time points.
They can create infringement disputes over test conditions and statistical variation.
They may limit the ability to rely on formulation similarity alone.

The term “about” applies to several temporal and quantitative limitations. It may provide some tolerance around 18-24 hours, 90 minutes, and related periods, but it does not eliminate the need for a product to fall within the overall claimed release profile.

The “zero-order or pseudo-zero-order” limitation in claims 6 and 24 narrows the claim further. A product does not necessarily satisfy this limitation merely because it is labeled “extended release.” The release curve would need to support a substantially constant or approximately constant delivery rate over the relevant period.

What is the likely infringement scope of US 6,613,357?

A product is most exposed when it combines the following characteristics:

Fexofenadine and pseudoephedrine in one oral unit.
Immediate-release fexofenadine on the outside of an osmotic pseudoephedrine tablet.
A semipermeable cellulose-based membrane.
A membrane passageway initially blocked by an erodible coating.
Approximately 18-24-hour pseudoephedrine delivery.
A dissolution profile matching one of the three independent claim sets.

A competing product could reduce literal infringement risk by changing one required feature, such as:

Using a bilayer tablet instead of an outer drug-containing coating.
Placing fexofenadine in a separate immediate-release layer.
Using a nonosmotic extended-release matrix.
Omitting a plugged membrane passageway.
Using a different release profile.
Delivering fexofenadine over a materially longer period.
Separating the two active ingredients into different dosage units.

A design-around analysis must account for the doctrine of equivalents. A structural change that performs substantially the same function in substantially the same way may still create litigation risk, although the quantitative dissolution limitations and prosecution history may constrain an equivalents theory.

When did US Patent 6,613,357 lose exclusivity?

US Patent 6,613,357 issued on September 2, 2003. Its US term ran for approximately 20 years from the relevant nonprovisional filing date and ended in 2021. Public patent databases report an expiration date of February 12, 2021, subject to any applicable patent-term adjustment reflected in the USPTO record [1, 2].

Event	Date
Patent issued	September 2, 2003
Ordinary US term end	February 12, 2021
Current enforceability	Expired by term

The patent is therefore no longer an active US barrier to a properly authorized generic or other competing product. Historical validity remains relevant to damages, prior litigation, licensing audits, and patent-term analysis, but a new US infringement suit based solely on an expired patent generally cannot provide prospective exclusionary relief.

What is the Orange Book status of Allegra-D and this patent?

The FDA Orange Book identifies patents submitted by NDA sponsors for approved drug products. Allegra-D products have historically been associated with fexofenadine and pseudoephedrine combination NDAs, including 12-hour and 24-hour presentations [3].

US 6,613,357 was relevant to the extended-release fexofenadine-pseudoephedrine product line and to historical generic-entry analysis. Its listing, if present for the applicable NDA and strength, does not extend the patent term. Orange Book listing and patent enforceability are separate questions.

The product regulatory profile is also affected by pseudoephedrine controls. Pseudoephedrine products are subject to federal and state sales restrictions, identification requirements, purchase-quantity limits, and behind-the-counter controls under the Combat Methamphetamine Epidemic Act framework [4]. Those restrictions affect commercial distribution but do not create patent exclusivity.

What FDA exclusivity protected the combination product?

FDA marketing exclusivity is distinct from patent protection. The relevant combination product was approved under an NDA pathway, and any applicable five-year new chemical entity exclusivity or three-year clinical-investigation exclusivity would have run before the 2021 patent expiration.

The exact exclusivity period depends on the NDA, approval date, active ingredients, and whether the FDA treated the combination or a component as eligible for a particular exclusivity period. For generic-entry analysis, the practical barrier was primarily the listed patent and the regulatory requirements for demonstrating bioequivalence to the extended-release combination product [3, 5].

The patent expiration did not eliminate the need for an ANDA sponsor to address:

Fexofenadine bioequivalence.
Pseudoephedrine extended-release performance.
Combination-product dissolution.
Labeling and dosing.
Manufacturing consistency.
Pseudoephedrine distribution controls.

Which companies challenged or competed against the patent?

The commercial market has included branded Sanofi products and generic or private-label suppliers of fexofenadine-pseudoephedrine extended-release tablets. Generic competition has generally proceeded through ANDA or other FDA-approved pathways rather than biosimilar procedures.

Publicly available patent materials identify ALZA Corporation as the original patent owner and connect the technology to the Allegra-D product platform. The supplied record does not establish a complete, verified list of Paragraph IV filers, litigation defendants, or settlement counterparties. Patent databases, FDA records, and court dockets should be read together because Orange Book certifications, ANDA approvals, and infringement complaints are separate records.

Were Paragraph IV challenges and patent settlements important?

A Paragraph IV certification would assert that a listed patent is invalid, unenforceable, or not infringed. For a listed patent, the NDA holder may file an infringement action within the statutory period, potentially triggering a 30-month stay of ANDA approval under the Hatch-Waxman framework [5].

For US 6,613,357, any historical Paragraph IV dispute would have concerned:

Whether the proposed product had an osmotic core.
Whether the outer layer was a fexofenadine-containing soluble or erodible coating.
Whether the passageway was plugged by an inert coating.
Whether the proposed dissolution profile met claims 1, 19, or 36.
Whether prior art anticipated or rendered obvious the combination.

No current settlement can extend the expired patent term. A historical settlement may have permitted an agreed generic launch date before expiration, but its commercial significance has ended unless it created separate contractual or licensing obligations.

What biosimilar risk exists for this patent?

There is no biosimilar pathway for this product. Fexofenadine and pseudoephedrine are small-molecule active ingredients, so competing products use generic-drug pathways, principally ANDAs, rather than 351(k) biosimilar applications.

The relevant competitive risks are:

ANDA approval.
OTC or prescription-to-OTC regulatory positioning.
Private-label supply.
Formulation substitution.
Separate immediate-release fexofenadine and extended-release pseudoephedrine products.
Combination-product manufacturing capacity.

How strong is the patent estate for fexofenadine-pseudoephedrine products?

The patent was technically focused but commercially narrow.

Strengths

It claimed the overall layered osmotic architecture.
It covered multiple dissolution profiles.
It included broad excipient Markush groups.
It captured the commercial dose range.
Claims 1, 19, and 36 provided alternative infringement positions.
The rapid-release fexofenadine and sustained pseudoephedrine combination was directly tied to the product’s therapeutic rationale.

Weaknesses

The claims require a specific physical architecture.
The dissolution requirements create testing and claim-construction disputes.
Many dependent claims are limited by detailed excipient quantities.
Conventional osmotic systems and immediate-release coatings could create prior-art pressure.
The patent has expired in the United States.
The claims do not broadly cover every fexofenadine-pseudoephedrine combination product.

The estate was strongest against a direct copy of the ALZA-style osmotic tablet. It was weaker against matrix systems, bilayer tablets, multiparticulates, separate dosage units, or products with materially different dissolution behavior.

What manufacturing and IP barriers remain after patent expiration?

Patent expiration removes the principal US composition-and-device barrier, but manufacturing remains technically demanding. A commercial product must control:

Core compression and mechanical strength.
Membrane thickness and permeability.
Passageway dimensions.
Plugging-coat dissolution.
Fexofenadine coating weight.
Disintegrant distribution.
Pseudoephedrine release across the full 24-hour period.
Dose uniformity and content uniformity.
Coating adhesion and stability.
Packaging and moisture protection.

Potential post-expiration barriers include manufacturing know-how, regulatory bioequivalence, process validation, supplier qualification, trademark restrictions, trade secrets, and controlled-pseudoephedrine distribution compliance. These are commercial and regulatory barriers rather than continuing rights under US 6,613,357.

How does US 6,613,357 compare with conventional Allegra-D alternatives?

Product architecture	Fexofenadine release	Pseudoephedrine release	Exposure to US 6,613,357
Patented osmotic combination	Rapid outer coating	Osmotic 18-24-hour release	Highest historical exposure
Bilayer tablet	Immediate or rapid layer	Matrix or osmotic layer	Depends on membrane and passageway structure
Matrix combination tablet	Matrix release	Matrix release	Lower if no semipermeable membrane and plugged passageway
Separate tablets	Separate immediate and extended-release units	Extended release	Generally outside single-device claims
Immediate-release combination	Rapid	Rapid	Outside the controlled-release limitations

The patent targeted the integrated osmotic device rather than the active ingredients as such.

Key Takeaways

US 6,613,357 covers a fexofenadine outer coating combined with an osmotic pseudoephedrine core.
Claims 1, 19, and 36 are the main device claims and use different pseudoephedrine dissolution profiles.
Claims 18 and 37 cover treatment methods using the claimed devices.
Dependent claims narrow the invention through dose, coating weight, excipient identity, and quantitative formulation ranges.
The patent was associated with the Allegra-D 24 Hour product concept.
The US patent term ended in 2021, eliminating current patent-based exclusion in the United States.
Generic competition is governed by small-molecule ANDA requirements, not biosimilar law.
The principal historical infringement risk was a direct copy of the osmotic tablet architecture and dissolution profile.
Current commercial barriers are regulatory, manufacturing, supply-chain, trademark, and controlled-pseudoephedrine requirements.

FAQs

Can a generic manufacturer launch an fexofenadine-pseudoephedrine product after expiration of US 6,613,357?

Yes, provided the product satisfies FDA approval, bioequivalence, labeling, manufacturing, and pseudoephedrine-control requirements and does not infringe another unexpired patent.

Does US 6,613,357 cover fexofenadine or pseudoephedrine as active ingredients?

No. It covers a particular combination dosage-form architecture and release profile, not the active ingredients broadly.

Does a bilayer Allegra-D substitute infringe the patent?

Not automatically. The analysis depends on whether the bilayer product contains the claimed semipermeable membrane, passageway, plugged coating, fexofenadine-containing outer coating, and claimed dissolution profile.

Is a separate fexofenadine tablet plus extended-release pseudoephedrine tablet within the claims?

Generally no, because the independent claims require one osmotic device containing both release systems.

Does patent expiration eliminate FDA approval requirements for generic Allegra-D?

No. Expiration removes the patent barrier but does not eliminate ANDA review, bioequivalence testing, dissolution testing, manufacturing controls, labeling requirements, or pseudoephedrine distribution restrictions.

References

United States Patent and Trademark Office. (2003). U.S. Patent No. 6,613,357, Osmotic device comprising fexofenadine and pseudoephedrine.
Google Patents. (n.d.). US6613357B2: Osmotic device comprising fexofenadine and pseudoephedrine.
U.S. Food and Drug Administration. (n.d.). Orange Book: Approved drug products with therapeutic equivalence evaluations.
U.S. Food and Drug Administration. (n.d.). Combat methamphetamine epidemic act and pseudoephedrine sales restrictions.
U.S. Food and Drug Administration. (2017). Abbreviated new drug application approvals and patent certifications under the Hatch-Waxman amendments.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	026818	⤷ Start Trial
Argentina	043468	⤷ Start Trial
Austria	397917	⤷ Start Trial
Australia	2634901	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,613,357

Summary for Patent: 6,613,357