US Patent 8,263,581: Scope, Claims, Expiration, Orange Book Status, and Cetirizine Injection Patent Landscape

US Patent 8,263,581 protects the clinical use of injectable racemic cetirizine for acute urticaria associated with an acute allergic reaction. Its core limitation is a 2 mg to 10 mg dose administered from an aqueous injectable composition with a pH of 3 to 9. The patent also covers pharmacokinetic equivalence to oral cetirizine, clinical comparison with injectable diphenhydramine, placebo superiority, intravenous administration, intramuscular administration, and use in anaphylaxis.

The patent is commercially significant because it covers the use of injectable cetirizine marketed as Quzyttir, rather than the older oral cetirizine products Zyrtec and generic cetirizine. The known patent term extends into 2029, while FDA regulatory exclusivity for the injectable product expired earlier.

What does US Patent 8,263,581 protect?

US 8,263,581 is directed to methods of treating acute urticaria in an emergency or acute-care setting with injectable racemic cetirizine. The patent does not primarily claim cetirizine as a new chemical entity. It claims a dosage form and clinical use of an established antihistamine.

Patent element	Scope
Active ingredient	Racemic cetirizine or a salt, including cetirizine hydrochloride
Dosage form	Injectable aqueous composition
pH	3 to 9
Dose	2 mg to 10 mg racemic cetirizine
Disease	Acute urticaria associated with an acute allergic reaction
Setting	Emergency situation
Routes	Intravenous or intramuscular injection
Combination agents	Ranitidine, cimetidine, epinephrine, methylprednisolone, prednisolone, or combinations
Additional conditions	Anaphylaxis is expressly covered
Comparator limitations	Oral cetirizine pharmacokinetics, diphenhydramine clinical response, or placebo response

The independent claim is claim 1. Claims 2 through 9 depend on claim 1 and inherit every limitation of the base claim.

How broad is claim 1 of US 8,263,581?

Claim 1 has meaningful commercial breadth but is narrower than a general composition claim. A potentially infringing method must satisfy all of the following conditions:

An individual is treated in an emergency situation.
The condition is acute urticaria associated with an acute allergic reaction.
The treatment uses an effective amount of injectable racemic cetirizine or a salt.
The injectable composition is aqueous.
The composition has a pH from 3 to 9.
The administered dose is 2 mg to 10 mg of racemic cetirizine.

The claim is not limited to a specific excipient system, vial size, concentration, preservative, container, or manufacturing process. It therefore reaches multiple aqueous injectable formulations that fall within the stated pH and dose ranges.

The claim is limited by the treatment method. A product containing injectable cetirizine is not, by itself, necessarily within the literal scope of claim 1 unless it is used in the claimed manner. Commercial activity can still create infringement exposure through induced infringement if labeling, promotional materials, dosing instructions, or distributor conduct encourage the claimed use.

The phrase "in an emergency situation" creates a potential claim-construction issue. Quzyttir is labeled for acute urticaria and is administered in acute-care settings, but the patent claim requires more than ordinary outpatient treatment. The strength of an infringement case would depend on the product label, prescribing context, clinical protocol, and evidence showing that the administration occurred in an emergency situation.

What do claims 2 through 9 add?

What does claim 2 protect?

Claim 2 adds a pharmacokinetic limitation. The 90% confidence limits for the ratio of the logarithmically transformed geometric mean AUC from zero to infinity for the injectable composition versus an oral racemic cetirizine reference must fall within 0.80 to 1.25.

This is a bioequivalence-style range. It narrows the patent to injectable products whose systemic exposure is statistically comparable to the specified oral reference product. A competing formulation that produces materially higher or lower exposure could avoid claim 2 while remaining within claim 1.

What does claim 3 protect?

Claim 3 covers injectable cetirizine combined with one or more specified active agents:

Ranitidine
Cimetidine
Epinephrine
Methylprednisolone
Prednisolone

The claim also covers combinations of those agents. The claim is relevant to emergency allergy protocols in which antihistamines are administered alongside corticosteroids, H2 antagonists, or epinephrine.

Claim 3 does not cover every emergency-allergy combination. An injectable cetirizine product combined with an unlisted active agent would not literally satisfy this dependent claim, although it could remain within claim 1.

What does claim 4 protect?

Claim 4 adds a clinical-response limitation. The confidence interval around the difference in symptom reduction versus a reference injectable formulation must fall within approximately -30.00 to +30.00 for the per-protocol evaluable population.

The relevant symptoms are:

Pruritus
Number of urticaria areas
Urticaria areas

This limitation is tied to a comparative clinical result rather than merely the composition. It may require clinical data to establish infringement, particularly where the competing product has a different formulation or dosing regimen.

What does claim 5 protect?

Claim 5 specifies the reference injectable formulation in claim 4 as a 12.5 mg to 150 mg dose of a 50 mg/mL diphenhydramine injection.

The claim appears directed to a noninferiority-type comparison between injectable cetirizine and injectable diphenhydramine. The unusually broad diphenhydramine dose range covers 0.25 mL to 3 mL of a 50 mg/mL formulation.

What does claim 6 protect?

Claim 6 requires injectable cetirizine to be statistically superior to placebo, with p<0.05, for reduction of pruritus, urticaria count, or urticaria areas.

The claim is dependent on the treatment and formulation requirements of claim 1. Statistical superiority is a substantive limitation. A product used for acute urticaria without supporting data showing the claimed placebo comparison could face a proof issue under claim 6.

What do claims 7 and 8 protect?

Claims 7 and 8 divide the principal administration routes:

Claim 7: intravenous injection
Claim 8: intramuscular injection

These claims are commercially important because an injectable cetirizine product labeled for both IV and IM administration can potentially practice both claims.

What does claim 9 protect?

Claim 9 expressly extends the method to acute urticaria associated with anaphylaxis. The claim does not replace the need to satisfy claim 1. Anaphylaxis must be present in the claimed acute-allergic-reaction context, and the composition, dose, aqueous formulation, pH, and emergency-setting limitations remain applicable.

What product is associated with US 8,263,581?

The commercial product most closely associated with the patent is Quzyttir, cetirizine hydrochloride injection. FDA approved Quzyttir in 2019 for treatment of acute urticaria in adults and pediatric patients six months of age and older [2].

The product is supplied as a 10 mg/mL aqueous injection and is administered intravenously or intramuscularly. The labeled dose varies by age and weight, with a 10 mg dose used in adults and certain older pediatric patients. Lower doses are used in younger children [2].

Product characteristic	Quzyttir
Active ingredient	Cetirizine hydrochloride
Chemical form	Racemic cetirizine salt
Concentration	10 mg/mL
Dosage form	Injectable solution
Routes	IV and IM
FDA indication	Acute urticaria
Sponsor/applicant	JDP Therapeutics
Approval pathway	FDA 505(b)(2) application
Associated patent	US 8,263,581

The product’s 10 mg/mL concentration permits administration of 2 mg to 10 mg through dose-volume adjustment. The product’s IV and IM labeling maps directly to the route limitations in claims 7 and 8.

What is the Orange Book status and expiration date?

US 8,263,581 is associated with the FDA-approved injectable cetirizine product and has been listed in the Orange Book for Quzyttir-related approval information. The patent term is generally reported to expire in April 2029, subject to the official USPTO term calculation and any applicable adjustment or disclaimer [1, 3].

Milestone	Date or status
Priority date	April 18, 2008
Patent grant	September 11, 2012
Patent number	US 8,263,581 B2
FDA approval of Quzyttir	2019
Reported patent expiration	April 2029
Regulatory exclusivity	Expired before the patent term
Orange Book relevance	Patent listed in connection with injectable cetirizine

The patent’s remaining term, rather than FDA exclusivity, is the principal barrier to an injectable cetirizine competitor. The underlying oral cetirizine market does not provide the same protection because cetirizine’s older composition and oral-product patents have expired.

When does injectable cetirizine lose exclusivity?

Injectable cetirizine has two separate exclusivity layers:

FDA regulatory exclusivity.
Patent exclusivity.

FDA granted Quzyttir approval based on clinical investigations supporting the injectable formulation and indication. The product received a period of three-year exclusivity under the new clinical investigation provisions applicable to certain previously approved active ingredients, dosage forms, or indications. That regulatory exclusivity expired before the reported April 2029 patent expiration.

The patent therefore remains the key barrier to a competing product using the same claimed treatment approach. A competitor could seek approval after regulatory exclusivity ended, but it would still need to address US 8,263,581 if its proposed label or use falls within the patent claims.

Are there Paragraph IV challenges or patent settlements?

The cited FDA and patent records do not identify a publicly reported Paragraph IV challenge, district-court infringement action, or settlement directed specifically to US 8,263,581. The Orange Book listing supports a patent certification issue for an ANDA or other abbreviated pathway applicant, but it does not by itself establish that a Paragraph IV notice has been served.

Because the patent claims methods of treatment, an ANDA applicant would face several possible strategies:

File a Paragraph IV certification and challenge validity or noninfringement.
Use a section viii statement that omits the patented acute-urticaria use, if FDA permits the omission.
Develop a product whose labeling avoids the claimed emergency use, dose range, or route.
Wait for patent expiration.

A section viii strategy would be difficult if the proposed product is intended to compete directly with Quzyttir for the same acute-urticaria indication. A Paragraph IV challenge would likely focus on obviousness, written description, enablement, clinical-result limitations, and whether the prior art disclosed injectable cetirizine for emergency urticaria treatment.

How strong is the patent estate for injectable cetirizine?

The patent estate appears concentrated rather than layered. US 8,263,581 provides the principal identified US patent protection for the injectable acute-urticaria use. The estate is stronger against a direct Quzyttir substitute than against peripheral products.

Risk category	Assessment
Direct IV/IM injectable cetirizine for acute urticaria	High
Injectable cetirizine for an unrelated indication	Lower
Oral cetirizine	Minimal relevance
Different active antihistamine	Outside literal active-ingredient scope
Nonemergency outpatient use	Potentially outside claim 1
Dose above 10 mg or below 2 mg	Potential design-around issue
Non-aqueous formulation	Potential design-around issue
Different pH outside 3 to 9	Potential design-around issue
Combination with unlisted agent	Avoids claim 3, but not claim 1
IV-only or IM-only product	May practice only one route claim

The principal vulnerability is that the patent is a method patent with several fact-intensive limitations. The principal strength is that a directly competing product is likely to use the same active ingredient, aqueous injectable format, 2 mg to 10 mg dose range, acute-urticaria indication, and IV or IM administration.

What prior patents and products compete with US 8,263,581?

The competitive landscape separates into three groups.

Oral cetirizine products

Zyrtec and generic cetirizine products are not direct substitutes for the claimed injectable emergency treatment. Their patents have expired, and they do not satisfy the injectable-composition limitation.

Injectable first-generation antihistamines

Diphenhydramine injection is the principal clinical comparator identified in the patent. It is an established injectable antihistamine, but it is sedating and is not the claimed non-sedating racemic cetirizine product.

Other acute-allergy medicines

Epinephrine, corticosteroids, and H2 antagonists address different components of acute allergic reactions. They may be co-administered with cetirizine, but they do not independently practice the cetirizine claims.

No biosimilar pathway applies. Cetirizine is a small molecule, not a biologic. A competing injectable product would proceed through an abbreviated or full small-molecule drug pathway, not a biosimilar application under the Public Health Service Act.

What manufacturing and formulation barriers remain?

The patent does not claim a narrowly defined manufacturing process. Its manufacturing relevance arises from the need to produce a stable sterile aqueous injectable meeting the claimed pH and dose parameters.

A competitor would need to address:

Sterility assurance
Injectable-grade excipients
Chemical stability of cetirizine hydrochloride
Container-closure compatibility
Dose uniformity
Particulate and endotoxin controls
IV and IM administration tolerability
pH control within the claimed or commercially appropriate range

A formulation outside pH 3 to 9 may avoid literal claim 1, but that approach could create stability, tolerability, or regulatory problems. A nonaqueous product could create a similar tradeoff. The practical design-around space is therefore narrower than the claim language alone suggests.

What generic launch scenarios exist?

Three launch scenarios are commercially plausible:

Direct launch after patent expiry.
A competitor launches an injectable racemic cetirizine product after the reported April 2029 expiration.
Paragraph IV launch.
An ANDA applicant challenges the patent before expiration and argues invalidity, noninfringement, or both.
Carved-out launch.
A competitor omits acute-urticaria emergency-use language or another patented use, subject to FDA acceptance and the actual promotional conduct.

The direct-launch case has the lowest litigation risk but delays market entry. A Paragraph IV strategy could accelerate entry but would expose the applicant to patent litigation and a potential 30-month stay under the Hatch-Waxman framework if the statutory requirements are met. A carve-out strategy would reduce claim exposure but also limit the commercial addressable market.

Key Takeaways

US 8,263,581 is a method patent for injectable racemic cetirizine in acute urticaria and acute allergic reactions.
Claim 1 requires an aqueous injectable composition, pH 3 to 9, emergency administration, and a 2 mg to 10 mg racemic cetirizine dose.
Claims 7 and 8 separately cover IV and IM administration.
Claim 9 expressly covers acute urticaria associated with anaphylaxis.
Claims 2, 4, and 6 add pharmacokinetic, clinical-comparison, and placebo-superiority limitations.
Quzyttir is the principal commercial product associated with the patent.
The reported patent expiration is in April 2029.
FDA regulatory exclusivity ended before the patent term.
No publicly reported Paragraph IV litigation or settlement was identified in the cited records.
No biosimilar pathway applies because cetirizine is a small-molecule drug.
The patent estate is concentrated, but it presents substantial risk to a direct IV or IM injectable cetirizine competitor.

FAQs

Can an oral generic cetirizine product infringe US 8,263,581?

Not on the face of the claims. The claims require an injectable aqueous composition and do not cover ordinary oral cetirizine tablets, capsules, or oral solutions.

Does the patent cover levocetirizine injection?

The claims recite racemic cetirizine or a salt thereof. Levocetirizine is the single-enantiomer form and is not automatically within the literal scope of a claim limited to racemic cetirizine. The analysis would depend on the exact product composition and claim construction.

Does a cetirizine injection for chronic urticaria fall within the patent?

The claims require acute urticaria associated with an acute allergic reaction. A product used solely for chronic spontaneous urticaria would present a stronger noninfringement position, although labeling and actual use would control the practical risk.

Can a competitor avoid the patent by using a dose above 10 mg?

A dose above 10 mg would not literally satisfy the 2 mg to 10 mg limitation of claim 1. Other claims and infringement theories would still require separate analysis, particularly if the product is promoted for the same patented use.

Is diphenhydramine itself covered by US 8,263,581?

No. Diphenhydramine appears as a reference injectable formulation in claim 5 and is listed as a possible comparator. The patent does not claim diphenhydramine as the active ingredient.

References

United States Patent and Trademark Office. (2012). US Patent No. 8,263,581 B2: Injectable compositions of cetirizine. https://patents.google.com/patent/US8263581B2/en
U.S. Food and Drug Administration. (2019). Quzyttir (cetirizine hydrochloride injection) prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Esteve	QUZYTTIR	cetirizine hydrochloride	SOLUTION;INTRAVENOUS	211415-001	Oct 4, 2019		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				TREATMENT OF ACUTE URTICARIA	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2010266103	⤷ Start Trial
Canada	2803987	⤷ Start Trial
European Patent Office	2477634	⤷ Start Trial
Spain	2616703	⤷ Start Trial
World Intellectual Property Organization (WIPO)	2011003074	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,263,581

Which drugs does patent 8,263,581 protect, and when does it expire?

Summary for Patent: 8,263,581