US Patent 8,722,738: Scope, Claims, Expiration, Litigation, and Acetylcysteine Patent Landscape

US Patent No. 8,722,738 protects a specific intravenous two-bag acetylcysteine regimen for acetaminophen overdose. The core regimen delivers 200 mg/kg during the first four hours and 100 mg/kg during the following 16 hours, for a total of 300 mg/kg over approximately 20 hours. The patent also covers continuation treatment based on liver-function results, additional acetylcysteine dosing, selected diluents, and low-EDTA or low-chelating-agent compositions.

The patent was assigned to Cumberland Pharmaceuticals Inc. and is listed in the FDA Orange Book for Acetadote, the reference product identified in NDA 021539. The listed patent term expired on December 22, 2025, absent a patent-term extension or other enforceable continuation right. The claims are method-of-treatment claims, not broad composition-of-matter claims. [1, 2]

What drug does US Patent 8,722,738 protect?

US 8,722,738 protects use of intravenous acetylcysteine for acetaminophen overdose and overdose-related liver injury.

Patent attribute	Detail
Patent number	US 8,722,738 B2
Title	Methods for treating acetaminophen overdose
Patent holder/assignee	Cumberland Pharmaceuticals Inc.
Active ingredient	Acetylcysteine
Reference product	Acetadote
FDA application	NDA 021539
Administration route	Intravenous
Primary dosage form	Acetylcysteine injection or diluted infusion
Core regimen	200 mg/kg over 4 hours, followed by 100 mg/kg over 16 hours
Total initial dose	300 mg/kg
Patent issue date	May 13, 2014
Listed expiration date	December 22, 2025
Claim category	Method of treatment
Orange Book status	Listed for Acetadote, subject to the relevant FDA listing and use code

The claims do not cover every use of acetylcysteine, every acetaminophen-overdose regimen, or every acetylcysteine formulation. They require the claimed two-bag sequence or a dependent variation of that sequence.

What are the independent claims in US 8,722,738?

Claims 1 and 12 are the two independent claims.

Claim 1 covers treating acetaminophen-overdose-induced liver injury. Claim 12 covers treating acetaminophen overdose more generally. Both require:

Intravenous administration;
An acetylcysteine composition;
A first dosage of 50 mg/kg per hour for four hours; and
A second dosage of 100 mg/kg over 16 hours.

The first step equals 200 mg/kg in aggregate:

50 mg/kg/hour x 4 hours = 200 mg/kg.

The second step adds 100 mg/kg. The claimed initial course therefore totals 300 mg/kg.

Claim 1: liver-injury treatment

Claim 1 is narrower than claim 12 because it requires treatment of liver injury induced by acetaminophen overdose. It also requires a patient "in need thereof," which is a conventional patient-selection limitation but still forms part of the claim.

The claim does not require that the patient already be in fulminant hepatic failure. Claim 11 adds that condition as a dependent limitation, indicating that claim 1 reaches patients with acetaminophen-induced liver injury more broadly.

Claim 12: acetaminophen-overdose treatment

Claim 12 covers treatment of acetaminophen overdose without expressly requiring established liver injury. It is therefore the broader independent claim by patient condition, while both independent claims have the same dosing and route requirements.

How does the patented two-bag regimen compare with the traditional three-bag regimen?

The patent distinguishes the claimed two-bag protocol from the traditional three-bag acetylcysteine protocol.

Protocol	First infusion	Second infusion	Third infusion	Total dose
Traditional three-bag regimen	150 mg/kg over 1 hour	50 mg/kg over 4 hours	100 mg/kg over 16 hours	300 mg/kg
Claimed two-bag regimen	200 mg/kg over 4 hours	100 mg/kg over 16 hours	Not required	300 mg/kg
Claim 17 continuation	Initial two-bag regimen	100 mg/kg over 16 hours	200 mg/kg over 4 hours, then 100 mg/kg over 16 hours	Extended treatment

The patent does not generally cover the traditional three-bag regimen because its independent claims require the specific two-bag sequence. A product label that provides only the conventional one-hour, four-hour, and 16-hour sequence would present a different claim analysis.

The principal commercial value of the patent is therefore tied to use of the 200 mg/kg over four hours plus 100 mg/kg over 16 hours regimen, rather than to acetylcysteine itself.

What additional dosing methods are protected?

Claims 2 through 6 and claims 13 through 18 extend the core two-bag regimen.

Claim	Additional limitation
2	Assess clinically significant liver-function improvement and continue treatment beyond 21 hours if improvement has not occurred
3	Administer another 100 mg/kg over 16 hours
4	Continue at 6.25 mg/kg/hour after the second dose
5	Use ALT to assess liver-function improvement
6	Repeat the two-bag regimen after the second dose
13	Same continuation rule as claim 2, tied to claim 12
14	Add 100 mg/kg over 16 hours
15	Continue at 6.25 mg/kg/hour
16	Use ALT to assess improvement
17	Add 200 mg/kg over four hours followed by 100 mg/kg over 16 hours
18	Repeat the two-bag regimen

Claims 5 and 10, and their corresponding claim 16, identify ALT or AST as the clinical measure. Those claims do not require a particular numeric ALT or AST threshold. The absence of a defined threshold may create claim-construction and infringement issues where a protocol uses liver-function testing but applies an internally defined clinical endpoint.

The reference to treatment beyond 21 hours is notable because the two claimed infusion periods total 20 hours. That language creates a post-regimen decision point rather than a fixed third infusion in every patient. A protocol that routinely continues treatment after the initial regimen may implicate the dependent claims, depending on the remaining limitations.

What formulation limitations are protected?

Claims 7 through 9 and claims 19 through 21 add formulation and dilution limitations.

Low-EDTA and low-chelating-agent claims

Claims 7 and 19 require less than 0.05% EDTA. Claims 8 and 20 require less than 0.05% chelating agents.

These limitations apply only to the dependent claims. They do not narrow the independent claims unless a product or method is being assessed under those dependent claims. An acetylcysteine product containing no EDTA would generally satisfy the "less than 0.05%" limitation, assuming the other claim elements are met.

The broader "chelating agents" language may raise construction questions concerning:

Whether the percentage is measured by weight, volume, or another basis;
Whether the limitation applies to each chelating agent individually or all chelating agents in aggregate;
Whether trace excipients qualify as chelating agents; and
Whether the concentration is measured before or after dilution.

Diluent claims

Claims 9 and 21 cover preparation in an aqueous solution containing at least one of:

5% dextrose;
0.45% sodium chloride;
0.90% sodium chloride; or
Water for injection.

These claims track common hospital dilution media. They are not composition claims covering the premixed product in the abstract. The claimed method requires preparation before administration and the specified aqueous vehicle.

What is the Orange Book status of US 8,722,738?

The FDA Orange Book identifies US 8,722,738 in connection with Acetadote. The listing relates to the patented method of using acetylcysteine for acetaminophen overdose, rather than to ownership of acetylcysteine as an active ingredient. [1]

The Orange Book consequences were significant while the patent remained unexpired:

An ANDA applicant seeking approval for a product with a label that included the patented two-bag regimen could face a Paragraph IV certification or a section viii carve-out issue.
A Paragraph IV notice could trigger patent litigation under the Hatch-Waxman Act.
A valid listed patent could impose a 30-month stay if the statutory requirements were met.
A generic label omitting the patented method could reduce, but not necessarily eliminate, induced-infringement risk.

The patent's listed expiration date was December 22, 2025. Once that date passed, the patent no longer provided a forward-looking patent barrier to the claimed method, unless a separate enforceable term extension or related patent applied. No such extension should be assumed without a specific Orange Book or USPTO record.

When did US Patent 8,722,738 lose exclusivity?

The patent term ended on December 22, 2025, based on the listed expiration date. The patent was not a composition-of-matter patent with exclusivity extending for the life of acetylcysteine. Its exclusivity was tied to the patented treatment method.

The commercial exclusivity timeline was therefore:

Date	Event
December 22, 2005	Earliest priority date reflected in the patent family
May 13, 2014	US 8,722,738 issued
2014-2025	Method patent could support Orange Book litigation
December 22, 2025	Listed patent expiration
After December 22, 2025	No continuing US 8,722,738 method exclusivity, subject to any separate rights

FDA regulatory exclusivity is separate from patent protection. Acetadote's approval, generic approvals, and any pediatric or orphan-drug exclusivity must be assessed from FDA records rather than inferred from the patent term. The patent itself did not create a new chemical-entity exclusivity period.

Which companies challenged or competed against the Acetadote patent estate?

Publicly reported Hatch-Waxman activity involving acetylcysteine injection has included challenges by generic manufacturers seeking approval for acetylcysteine products. Cumberland's patent enforcement strategy focused on the two-bag dosing method and related Acetadote claims, rather than on ownership of acetylcysteine.

The competitive field includes generic injectable manufacturers and suppliers of acetylcysteine injection approved under ANDAs. The key regulatory distinction is whether a competitor's labeling:

Includes the patented two-bag method;
Uses only the traditional three-bag protocol;
Omits the patented method through a section viii statement; or
Relies on patent expiration.

Because generic acetylcysteine injection products may have different labels, concentrations, manufacturers, and approved indications, the existence of a generic approval does not alone establish freedom to practice every claim of US 8,722,738.

What patent litigation affected US 8,722,738?

The relevant litigation risk arose under the Hatch-Waxman framework. Cumberland could sue an ANDA applicant after receiving a Paragraph IV notice alleging that the patent was invalid, unenforceable, or not infringed.

The principal litigation issues for this patent would include:

Whether the proposed label instructs the patented two-bag regimen;
Whether the dosing language is anticipated by earlier acetylcysteine protocols;
Whether the two-bag sequence would have been obvious to a skilled clinician;
Whether the claims adequately describe the liver-function continuation criteria;
Whether the patent properly claims a treatment method rather than an impermissible result;
Whether the patent has an enforceability issue based on prosecution conduct; and
Whether the patent was properly listed for the relevant approved method.

A settlement could authorize a generic launch before patent expiration, but the existence and terms of a settlement must be established from the specific court docket or company filing. Patent expiration on December 22, 2025 materially reduced the economic value of any remaining litigation.

How strong is the patent estate for acetylcysteine injection?

The estate was commercially focused but technically narrow.

Strengths

The patent had several practical strengths:

It claimed a defined dosing sequence used in the Acetadote product context.
It covered both overdose treatment and overdose-induced liver injury.
It included continuation-treatment claims responsive to ALT, AST, or clinical status.
It was listed in the Orange Book, enabling Hatch-Waxman enforcement.
The regimen was sufficiently specific to distinguish it from the traditional three-bag protocol.

Weaknesses

The estate also had material limitations:

It did not cover acetylcysteine generally.
It did not cover all intravenous acetylcysteine dosing.
The independent claims depended on a precise regimen that a competitor could potentially omit from its label.
The dependent claims introduced concentration and formulation issues.
Method claims generally require proof that the claimed steps were performed or induced.
The patent expired in 2025, eliminating its remaining US term-based barrier.

The estate's commercial strength was highest before generic applicants could obtain approval without using the patented method. Its strength declined as competitors developed label strategies around the two-bag regimen and became substantially lower after expiration.

What generic launch risks existed?

Before expiration, a generic launch could occur through several routes.

Launch pathway	Patent exposure
Full label including two-bag regimen	High Paragraph IV and induced-infringement risk
Section viii label omitting patented method	Lower method-patent risk, subject to actual labeling
Traditional three-bag-only label	Lower risk under the literal two-bag claims
Launch after patent expiration	US 8,722,738 no longer blocks the method
Product with different diluent or excipient profile	May avoid dependent formulation claims but not independent claims
Product with same regimen but different concentration	May still infringe independent claims if all limitations are met

A label carve-out is not automatically dispositive. Promotional materials, clinical-support documents, electronic order sets, and other instructions may be relevant to induced infringement. Conversely, a generic manufacturer does not necessarily infringe merely because physicians independently use the product in the patented manner if the manufacturer does not promote or instruct that use.

What manufacturing and intellectual-property barriers remain?

US 8,722,738 does not create a manufacturing monopoly over acetylcysteine. It does not claim:

The acetylcysteine molecule;
A general sterile-injection manufacturing process;
A broad stability platform;
All preservative-free formulations;
All ready-to-use containers; or
All hospital dilution practices.

Manufacturers may still face separate barriers involving sterile manufacturing capacity, FDA facility compliance, container-closure systems, stability data, injectable-product quality, supply reliability, trademarks, and other patent families. Those issues are distinct from the expired two-bag method patent.

How does Acetadote compare with generic acetylcysteine injection?

Issue	Acetadote	Generic acetylcysteine injection
Regulatory status	Reference NDA product	ANDA products
Active ingredient	Acetylcysteine	Acetylcysteine
Core patented regimen	Two-bag method historically protected	May include, omit, or differ in labeling
Composition protection	Not granted by US 8,722,738 broadly	Product-specific formulation rights may differ
Patent barrier after Dec. 22, 2025	US 8,722,738 expired	No barrier from this patent
Commercial differentiation	Branded product, dosing protocol, supply, labeling	Price, availability, concentration, and contracting
Biosimilar risk	None in the biologic sense	Acetylcysteine is a small-molecule drug, so generic rather than biosimilar competition applies

Biosimilar risk is not the relevant framework because acetylcysteine is a small-molecule active pharmaceutical ingredient. Competition proceeds through ANDAs and generic-drug approval, not through the abbreviated biologics license application pathway.

Key Takeaways

US 8,722,738 is a method patent covering a two-bag intravenous acetylcysteine regimen.
The core regimen is 200 mg/kg over four hours followed by 100 mg/kg over 16 hours.
Claims 1 and 12 are the independent claims.
Dependent claims cover continued treatment, repeat dosing, ALT or AST monitoring, 6.25 mg/kg/hour maintenance dosing, additional 100 or 200 mg/kg doses, low-EDTA formulations, low-chelating-agent formulations, and specified diluents.
The patent does not broadly cover acetylcysteine, acetylcysteine injection, or the traditional three-bag protocol.
The patent was listed in the Orange Book for Acetadote.
The listed patent expiration date was December 22, 2025.
Generic competition is governed primarily by ANDA labeling, Paragraph IV certifications, section viii carve-outs, and patent expiration.
Biosimilar analysis is not applicable because acetylcysteine is a small-molecule drug.
After expiration, the patent no longer provides a US method-of-treatment barrier, subject to any separate patent, regulatory exclusivity, or enforceable settlement right.

FAQs About US Patent 8,722,738

Does US 8,722,738 cover the standard three-bag acetylcysteine regimen?

No. The independent claims require the two-bag sequence of 200 mg/kg over four hours followed by 100 mg/kg over 16 hours. The conventional 150/50/100 mg/kg three-bag regimen does not literally satisfy that sequence.

Does the patent cover oral acetylcysteine?

No. The claims require intravenous administration. Oral acetylcysteine products and oral treatment methods fall outside the literal scope of these claims.

Does a generic acetylcysteine product infringe because it contains no EDTA?

Not necessarily. The low-EDTA limitation appears only in dependent claims 7 and 19. The independent claims do not require an EDTA limitation.

Is claim 17 limited to patients with liver failure?

No. Claim 17 depends on claim 12, which covers treatment of acetaminophen overdose. The express liver-failure limitation appears in claim 11, which depends on claim 1.

Can a manufacturer avoid the patent by using a different diluent?

A different diluent may avoid claims 9 and 21, but it would not avoid the independent claims if the manufacturer or user still performs the claimed two-bag dosing method.

Is there a biosimilar pathway for Acetadote?

No. Acetylcysteine is a small-molecule drug. Competitive products are generally approved through the ANDA pathway rather than through biosimilar procedures.

References

U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations: Orange Book, Acetadote, NDA 021539. https://www.accessdata.fda.gov/scripts/cder/ob/
United States Patent and Trademark Office. (2014). U.S. Patent No. 8,722,738: Methods for treating acetaminophen overdose. https://patents.google.com/patent/US8722738B2/en
Cumberland Pharmaceuticals, Inc. (2024). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. U.S. Securities and Exchange Commission. https://www.sec.gov/
U.S. Food and Drug Administration. (2024). Acetadote prescribing information. https://www.accessdata.fda.gov/
U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs database. https://www.accessdata.fda.gov/scripts/cder/daf/

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Apotex	ACETADOTE	acetylcysteine	INJECTABLE;INTRAVENOUS	021539-001	Jan 23, 2004	AP	RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				METHOD OF TREATING ACETAMINOPHEN OVERDOSE WITH ACETYLCYSTEINE SOLUTIONS	⤷ 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	2011281035	⤷ Start Trial
China	103038356	⤷ Start Trial
European Patent Office	2596112	⤷ Start Trial
Malaysia	173215	⤷ Start Trial
World Intellectual Property Organization (WIPO)	2012012640	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,722,738

Which drugs does patent 8,722,738 protect, and when does it expire?

Summary for Patent: 8,722,738