US Patent 7,915,229: Scope, Claim Analysis, Expiration and Piperacillin-Tazobactam Patent Landscape

US Patent 7,915,229 protects stabilized parenteral piperacillin-tazobactam compositions that use an aminocarboxylic acid chelating agent, principally EDTA, to reduce particulate formation. The patent is directed to formulation composition, concentration ranges, pH, packaging, dosage form, and particulate testing results. It does not claim piperacillin, tazobactam, or their antibacterial combination broadly.

The commercially relevant risk is concentrated in ready-to-use intravenous solutions, dose concentrates, and lyophilized products containing EDTA or a qualifying aminocarboxylic acid chelator. A conventional piperacillin-tazobactam product without the claimed particulate inhibitor would generally fall outside the literal scope of the independent claims, subject to formulation-specific facts and possible doctrine-of-equivalents issues.

What patent is US 7,915,229?

US 7,915,229 is titled “Piperacillin/tazobactam compositions.” The patent covers parenteral compositions containing piperacillin, tazobactam, a particulate-formation inhibitor, and, in many claims, citrate buffer or specified dosage-form characteristics.

Item	Detail
Patent	US 7,915,229 B2
Title	Piperacillin/tazobactam compositions
Patent type	Utility patent
Technology	Sterile parenteral piperacillin-tazobactam formulations
Principal formulation agent	EDTA or another aminocarboxylic acid chelating agent
Patent holder lineage	Wyeth, subsequently associated with Pfizer following the Wyeth-Pfizer transaction
Issue date	March 29, 2011
Earliest priority date	March 29, 2005
Projected basic term	March 29, 2026, before any applicable patent-term adjustment
Relevant product	Piperacillin sodium/tazobactam sodium injection
Regulatory context	NDA 050684 and corresponding abbreviated applications for generic products

The patent record should be read together with the issued claims, prosecution history, maintenance-fee record, terminal disclaimers, and any patent-term-adjustment calculation in USPTO Patent Center.[1]

What do the independent claims of US 7,915,229 cover?

Claims 1, 4, 6, 7, 8, 9, 10, 13 and 16 are the principal independent claims. They divide into five technical groups.

Claims 1 to 3: Chelator-to-piperacillin ratio

Claim 1 requires a pharmaceutical composition for parenteral administration containing:

Piperacillin or a pharmaceutically acceptable salt;
Tazobactam or a pharmaceutically acceptable salt; and
An aminocarboxylic acid chelating agent or salt used as a particulate-formation inhibitor.

The inhibitor-to-piperacillin ratio must be approximately 0.01 to 40 mg per gram of piperacillin.

Claims 2 and 3 narrow the ratio:

Claim	Ratio limitation
1	About 0.01 to about 40 mg inhibitor per gram piperacillin
2	About 0.1 to about 0.5 mg inhibitor per gram piperacillin
3	About 0.25 mg inhibitor per gram piperacillin

A formulation containing 1 mg EDTA per 4 g piperacillin has a ratio of 0.25 mg/g and falls within claim 3 if the remaining elements are satisfied.

The term “comprising” makes these claims open-ended. Additional excipients, buffers, carriers, containers, or active ingredients do not avoid infringement if all required elements are present.

Claims 4 and 5: Ready-to-use IV solution

Claim 4 is materially narrower than claim 1. It requires a solution and a unit dose in an IV bag or IV bottle for intravenous administration containing approximately:

40 mg/mL piperacillin sodium;
5 mg/mL tazobactam sodium;
20 mg/mL hydrous dextrose;
2 mg/mL sodium citrate dihydrate; and
An aminocarboxylic acid chelating agent.

The solution must have a pH of approximately 6.5.

Claim 5 specifically requires 1 mg EDTA. A product matching the commercial concentration profile of 40 mg/mL piperacillin and 5 mg/mL tazobactam, packaged as an IV solution, presents a direct claim-mapping risk if it also contains the specified dextrose, citrate, pH, and EDTA.

The “about” language creates ordinary claim-construction flexibility around the stated concentrations. It does not eliminate the need to evaluate the actual formulation, analytical tolerances, pH range, and package configuration.

Claims 6 and 7: Concentrated and dose-specific compositions

Claim 6 covers a composition containing approximately:

4,000 mg piperacillin sodium;
500 mg tazobactam sodium;
200 mg sodium citrate; and
1 mg EDTA.

Claim 7 covers a sealed-container dose concentrate containing approximately:

2,000 mg piperacillin sodium;
250 mg tazobactam sodium;
100 mg sodium citrate; and
0.5 mg EDTA.

These claims are commercially relevant to concentrate presentations that are diluted before administration. Claim 7 is not limited to a final diluted IV bag. Its sealed-container and dose-concentrate limitations create a separate infringement pathway for concentrated products.

Claim 8: Lyophilized composition

Claim 8 covers a lyophilized composition containing approximately:

40.5 g piperacillin sodium;
4.5 g tazobactam sodium;
1.8 g sodium citrate; and
9 mg EDTA.

This is a batch-scale or container-scale claim rather than a conventional patient-dose claim. The amounts correspond to a piperacillin-to-tazobactam ratio of 9:1 and an EDTA-to-piperacillin ratio of approximately 0.222 mg/g.

A lyophilized generic product can avoid literal infringement only if its composition, amounts, or relevant claim elements fall outside the claimed ranges or the product does not satisfy the required dosage-form limitations.

What formulations are protected by claims 9, 13 and 16?

Claims 9, 13 and 16 provide broader concentration-range coverage than claims 4, 6, 7 and 8.

Claim 9: Solution concentration ranges

Claim 9 covers a solution containing:

Component	Claimed range
Piperacillin sodium	About 12 to 300 mg/mL
Tazobactam sodium	About 1.5 to 75 mg/mL
Sodium citrate buffer	About 0.6 to 15 mg/mL
EDTA	About 0.003 to 1.0 mg/mL

This claim is potentially broad enough to reach multiple commercial presentations, including dilute ready-to-use solutions and more concentrated products. Unlike claim 1, claim 9 expressly requires EDTA rather than the broader category of aminocarboxylic acid chelating agents.

Claims 13 to 15: IV-bag or IV-bottle solutions

Claim 13 requires a unit-dose solution in an IV bag or IV bottle containing piperacillin sodium and tazobactam sodium within the following ranges:

Piperacillin sodium: about 8.0 to 90 mg/mL;
Tazobactam sodium: about 0.1 to 25 mg/mL.

The solution must also contain an aminocarboxylic acid chelating agent.

Claims 14 and 15 progressively narrow the concentration ranges:

Claim	Piperacillin sodium	Tazobactam sodium
13	8.0-90 mg/mL	0.1-25 mg/mL
14	25-80 mg/mL	1.0-22 mg/mL
15	30-80 mg/mL	3.0-20 mg/mL

A product at 40 mg/mL piperacillin and 5 mg/mL tazobactam falls within all three concentration sets, assuming the product also has the required chelator and IV-container characteristics.

Claims 16 to 18: pH and total concentration

Claim 16 requires:

Piperacillin;
Tazobactam;
An aminocarboxylic acid chelating agent;
A buffer adapted to maintain pH at about 6.0 to 7.5; and
Total concentration of piperacillin sodium, tazobactam sodium, particulate inhibitor, and citrate of about 9 to 125 mg/mL.

Claims 17 and 18 narrow total concentration:

Claim	Total concentration
16	About 9-125 mg/mL
17	About 14-115 mg/mL
18	About 20-105 mg/mL

These claims are important because they do not depend on the specific 40 mg/mL/5 mg/mL formulation. They can reach alternative concentrations that remain within the pH and total-solids boundaries.

How does the particulate-testing claim operate?

Claim 10 covers a unit-dose IV-bag or IV-bottle solution that produces no more than three particles per milliliter in the 25-micrometer category under a light-obscuration test performed 24 hours after solution creation using a method according to USP <788>.

Claim 11 limits the inhibitor to EDTA. Claim 12 adds an aminoglycoside.

This is a performance-based claim. Infringement analysis would require testing the accused product under materially comparable conditions, including:

Solution preparation;
Time elapsed before testing;
Container and storage conditions;
Sampling method;
Instrument settings;
USP <788> procedure; and
Particle-size category.

USP <788> addresses particulate matter in injections and establishes methods for determining subvisible particles.[2] The claim does not merely require that EDTA be present. It also requires the specified particulate-count result.

An accused manufacturer could challenge the claim by disputing test reproducibility, protocol conformity, the 24-hour timing, or whether the tested product is the claimed unit-dose solution.

How strong is the patent estate for piperacillin-tazobactam?

US 7,915,229 is a focused formulation patent rather than a broad compound patent. Its practical strength varies by product type.

Product type	Exposure under US 7,915,229
Conventional piperacillin-tazobactam powder without EDTA	Lower literal exposure
EDTA-containing lyophilized product	High if amounts track claim 8
Ready-to-use IV bag with EDTA	High if concentration and pH fall within claims 4, 9, 13-18
Dose concentrate with EDTA and citrate	High under claim 7
Product with a different chelator	Potential exposure under claims 1, 13 or 16
Product without citrate buffer	Reduced exposure to claims requiring citrate, but not necessarily claims 1, 10 or 13
Product outside the claimed particle-count result	Potential defense to claim 10, but not necessarily other claims

The estate has meaningful overlap among claims. A design-around must generally address more than one dimension: chelator identity, chelator concentration, citrate level, pH, total concentration, dosage form, packaging, and particulate performance.

What is the FDA regulatory and Orange Book status?

Piperacillin and tazobactam are small-molecule antibacterial agents. Products are regulated through new drug applications and abbreviated new drug applications, not through the biosimilar pathway.

Zosyn, the reference product historically marketed by Wyeth and later Pfizer, was approved under NDA 050684. The FDA-approved labeling identifies piperacillin sodium and tazobactam sodium for injection for parenteral treatment of susceptible bacterial infections.[3]

The regulatory exclusivity period for the original product expired long before the projected end of the formulation patent term. Current market protection therefore depends primarily on patent listings, patent-term calculations, Paragraph IV certifications, litigation, and settlement terms rather than new-drug exclusivity.

The Orange Book must be checked by NDA, product presentation, and patent number because listing status can change through delisting, expiration, correction, or FDA administrative action.[4] US 7,915,229 is a formulation patent and does not create exclusivity over all piperacillin-tazobactam products.

When does US 7,915,229 lose exclusivity?

The basic projected expiration date is March 29, 2026, based on the March 29, 2005 priority date and a 20-year patent term framework.[1] The operative date can be affected by patent-term adjustment, terminal disclaimer, disclaimer filing, or other USPTO-record events.

Patent expiration does not automatically eliminate all market barriers. A competing product may still face:

Other unexpired formulation patents;
Manufacturing-process patents;
Regulatory review requirements;
Injunction or settlement restrictions;
Product-specific Orange Book listings; and
Approval timing under an ANDA.

Conversely, a patent expiration does not preserve a claim that was cancelled, disclaimed, or invalidated before expiration.

Which companies are challenging piperacillin-tazobactam patents?

Generic piperacillin-tazobactam products have been developed and approved by multiple manufacturers, including companies operating through ANDA pathways. The relevant competitive group has included Sandoz, Apotex, Wockhardt, Aurobindo, Dr. Reddy’s, and other injectable-generic manufacturers, depending on product presentation and approval status.

A company filing an ANDA that references a listed patent may submit a Paragraph IV certification alleging that the patent is invalid, unenforceable, or not infringed. The patent owner can bring an infringement action within the statutory period, triggering the potential 30-month stay under the Hatch-Waxman framework.[5]

A complete Paragraph IV analysis requires the specific ANDA number, certification date, product presentation, and Orange Book listing status. The claim set alone does not establish which manufacturer has made a live challenge or whether a settlement exists.

What litigation and settlement issues matter?

For this patent, litigation risk is product-specific. The strongest potential claims would likely be claims 4, 7, 9, 13-15 and 16-18 against an EDTA-containing injectable formulation that closely follows the reference-product concentration and packaging profile.

Typical defenses include:

Noninfringement because the product lacks EDTA or another qualifying aminocarboxylic acid chelator.
Noninfringement because the product is not a unit dose in an IV bag or IV bottle.
Concentration values outside the claim range.
pH outside the claimed range.
Failure to meet the particulate-count limitation in claim 10.
Invalidity based on anticipation or obviousness over earlier piperacillin-tazobactam stabilization formulations.
Indefiniteness or lack of written description for particular range or performance limitations.
Prosecution-history estoppel based on amendments or arguments made during examination.

Settlement agreements may permit an earlier launch without conceding validity. Their commercial effect depends on the agreed launch date, authorized-generic terms, supply obligations, and treatment of future formulations. A patent number by itself does not reveal those terms.

What generic launch scenarios exist?

Scenario	Commercial result
Patent expires without successful enforcement	Broadest opportunity for EDTA-containing products after expiry
ANDA applicant wins noninfringement	Launch may occur before patent expiry, subject to other patents
Patent is invalidated	Formulation-specific barrier is removed
Settlement permits delayed entry	Launch date depends on contractual terms
Design-around excludes chelator	Lower risk under claims requiring the inhibitor, but other claims must be screened
Product uses a different presentation	Packaging and dosage-form limitations may reduce exposure
Product launches after March 2026	US 7,915,229 generally ceases to block new manufacture and sale, subject to the operative term record

How does this patent compare with compound and method-of-use protection?

US 7,915,229 is narrower than a compound patent and different from a method-of-use patent.

Protection category	What it protects	Relevance here
Compound patent	Piperacillin, tazobactam, or a new chemical entity	Not the focus of US 7,915,229
Combination patent	Piperacillin plus tazobactam generally	Broader than the claimed formulation only if valid and unexpired
Formulation patent	Excipients, concentration, pH, container, stability or particulate control	Core protection of US 7,915,229
Method-of-use patent	Treatment of a disease or organism	Not the principal claim type here
Manufacturing patent	Preparation, sterilization, lyophilization or filling process	Separate freedom-to-operate issue
Device or packaging patent	IV bag, container, delivery system	May overlap with the IV-container claims

Because the patent claims compositions rather than treatment steps, a generic manufacturer cannot avoid the claims merely by changing the prescribing language. The physical formulation remains the central infringement issue.

What is the revenue exposure?

Piperacillin-tazobactam is a mature hospital injectable market. Revenue exposure from this patent is concentrated in products that use stabilized, ready-to-administer presentations rather than all piperacillin-tazobactam sales.

The most exposed commercial attributes are:

EDTA-containing formulations;
Ready-to-use IV bags;
Citrate-buffered solutions;
40 mg/mL piperacillin and 5 mg/mL tazobactam presentations;
Dose concentrates;
Lyophilized products using the claimed bulk composition.

The patent does not support a claim to all global piperacillin-tazobactam revenue. Geographic exposure is principally United States-specific because patent rights, Orange Book listings, ANDA certifications and enforcement are jurisdictional.

Key Takeaways

US 7,915,229 is a formulation patent covering particulate-controlled parenteral piperacillin-tazobactam compositions.
EDTA is the central practical embodiment, although several claims cover the broader class of aminocarboxylic acid chelating agents.
Claims 4, 9, 13-15 and 16-18 create substantial overlap for EDTA-containing IV solutions.
Claims 6, 7 and 8 target specific concentrated and lyophilized compositions.
Claim 10 adds a USP <788>-based particulate-performance limitation.
The basic projected patent expiration is March 29, 2026, subject to the USPTO term record.
The patent does not broadly protect piperacillin, tazobactam, or every combination product.
Biosimilar analysis is not applicable because piperacillin-tazobactam is a small-molecule product.
A freedom-to-operate opinion must assess the actual formulation, chelator, pH, concentrations, packaging, dosage form, particulate test results and all other live patents in the product family.

FAQs

Does US 7,915,229 cover Zosyn itself?

It can cover particular Zosyn presentations if they contain the claimed chelator, citrate, concentration, pH, packaging and particulate-control characteristics. It does not cover every piperacillin-tazobactam product solely because the product contains the two antibiotics.

Can a generic avoid this patent by removing EDTA?

Removing EDTA can avoid claims expressly requiring EDTA, including claim 9 and claim 11. It may not avoid claims that cover the broader category of aminocarboxylic acid chelating agents or claims directed to a qualifying alternative inhibitor.

Is a piperacillin-tazobactam biosimilar required to challenge this patent?

No. Piperacillin-tazobactam is regulated as a small-molecule drug. The relevant pathway is generally an ANDA with applicable Paragraph IV certification, not a biosimilar application under the Public Health Service Act.

Does a different IV bag avoid infringement?

Not automatically. Claims 1, 9 and 16 do not all require the same container limitations. Changing from an IV bag to another container may avoid claims requiring a bag or bottle but leave broader composition claims in play.

Can a product outside the claim concentrations still infringe?

Yes, potentially. The patent includes multiple claims with different concentration ranges and functional limitations. A product outside one range may fall within another claim or raise a doctrine-of-equivalents issue, depending on the formulation and prosecution history.

References

United States Patent and Trademark Office. (2011). US Patent No. 7,915,229 B2, Piperacillin/tazobactam compositions.
United States Pharmacopeia. (2023). General chapter <788>: Particulate matter in injections. United States Pharmacopeial Convention.
U.S. Food and Drug Administration. (2024). Zosyn (piperacillin and tazobactam) prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j), Hatch-Waxman abbreviated new drug application provisions.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	043863	⤷ Start Trial
Austria	381947	⤷ Start Trial
Australia	2004229407	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,915,229

Summary for Patent: 7,915,229