US Patent 6,913,768: Scope, Claims, Expiration, and Amphetamine Patent Landscape

US Patent 6,913,768 covers controlled-release formulations containing mixed dextroamphetamine and levoamphetamine, including the four-salt composition used in mixed amphetamine salts products. Its central limitation is pharmacokinetic performance rather than a single proprietary polymer or manufacturing process. The patent claims formulations that release amphetamine continuously and produce specified plasma concentration profiles, slopes, AUC values, and Cmax values in human ADHD patients.

The patent has reached the end of its ordinary US patent term. On the public record, its enforceable term ran from the relevant US nonprovisional filing date in 2001 to approximately January 2021, subject to any recorded patent-term adjustment or extension. It is therefore not a current US patent barrier to generic entry. Its historical importance is substantial because it helped protect the extended-release mixed amphetamine salts platform associated with Adderall XR.

What does US Patent 6,913,768 protect?

The patent protects a pharmaceutical composition with four core elements:

A mixture of dextroamphetamine and levoamphetamine, or their salts.
A sustained-release coating or matrix.
A release-controlling material selected from specified polymers, waxes, fatty materials, alcohols, zein, or related excipients.
A pharmacokinetic or dissolution profile corresponding to an extended-release amphetamine profile.

The patent does not require one specific polymer in every independent claim. It lists multiple alternative release-control materials, including:

Polyvinyl acetate
Cellulose acetate
Cellulose acetate butyrate
Cellulose acetate propionate
Ethyl cellulose
Fatty acids
Fatty acid esters
Alkyl alcohols
Waxes
Zein
Poly(meth)acrylates
Microcrystalline cellulose
Polyethylene oxide

The claims therefore combine composition structure with functional performance. A formulation can fall within the claim scope only if it contains the required amphetamine mixture, includes a qualifying sustained-release system, and achieves the stated pharmacokinetic or release characteristics.

What amphetamine salts are covered?

Dependent claims identify a mixture comprising:

Dextroamphetamine sulfate
Dextroamphetamine saccharate
Amphetamine aspartate
Amphetamine sulfate

Claim 3 specifies equal amounts by weight of the four salts. This is the salt composition historically associated with mixed amphetamine salts products.

The claims are not limited to the four-salt mixture. Claims 1, 7, 9, 11, 12, 14, 15, and 35 use broader language covering mixtures of dextro- and levo-amphetamine or their salts. The four-salt formulation is a narrower species within that broader genus.

How are the claims organized?

The claim set has five principal claim families.

Claim family	Principal limitation	Representative claims
General PK profile	Profile substantially corresponding to dextroamphetamine XR or levoamphetamine XR over 12 hours	1, 6
Initial slope	Plasma concentration slope from two to four hours	7-11
AUC and Cmax	Specified exposure and peak concentration ranges	12-15, 35-37
Dosage form and excipient	Coated cores, matrices, ethyl cellulose, water-insoluble polymers	4, 5, 16-31
Treatment method	Administration to a human ADHD patient	6, 8, 10, 13, 18

The claims are heavily interrelated. Many dependent claims narrow the broad PK claims by adding ethyl cellulose, coated cores, a first-order dissolution profile, pH-independent release, or the four-salt amphetamine mixture.

What are the broadest claims in US 6,913,768?

Claim 1: broad PK-profile composition

Claim 1 is the principal broad composition claim. It requires a mixture of dextro- and levo-amphetamine or salts and a sustained-release coating or matrix containing one of the listed release-control materials. The formulation must produce a mean plasma concentration profile substantially the same as the dextroamphetamine XR and/or levoamphetamine XR profile shown in Figure 1 during the first 12 hours after a 20 mg dose.

For doses other than 20 mg, the claim applies a proportionality requirement.

The key point is that claim 1 is not limited to:

Ethyl cellulose
Bead-based dosage forms
A particular coating thickness
A particular capsule
A particular salt ratio
A particular manufacturing process

The claim is broad in formulation architecture but narrower in pharmacokinetic outcome.

Claims 7 and 9: slope-based protection

Claims 7 and 9 focus on the initial plasma concentration slope between two and four hours.

Claim 9 specifies approximate ranges at a 20 mg total dose:

Analyte	Initial slope range
Dextroamphetamine	About 3.7 to 11.4 ng/mL/hr
Levoamphetamine	About 1.4 to 3.0 ng/mL/hr

Claim 11 narrows those ranges:

Analyte	Narrower slope range
Dextroamphetamine	About 4 to 8 ng/mL/hr
Levoamphetamine	About 1.5 to 2.2 ng/mL/hr

These claims create a performance-based boundary. A competing formulation would need to be evaluated using the claimed dose normalization and sampling interval. Small changes in formulation or release rate could move a product outside the literal numerical ranges.

Claims 12-15 and 35: AUC and Cmax protection

The AUC and Cmax claims require the following approximate values for a 20 mg total dose:

Analyte	AUC	Cmax
Dextroamphetamine	556.6 mg·hr/mL, ±20%	28.0 ng/mL, ±20%
Levoamphetamine	205.1 mg·hr/mL, ±20%	8.7 ng/mL, ±20%

The unit presentation in the supplied claim text appears inconsistent. The patent’s intended pharmacokinetic units should be confirmed against the issued patent and prosecution record before litigation or freedom-to-operate use. The same applies to typographical errors in claims 11, 14, 15, and 16.

Claims 35-37 are commercially important because they combine the PK limitations with ethyl cellulose. Claim 37 further requires amphetamine-coated cores coated with ethyl cellulose. Those claims are narrower than claim 1 but potentially stronger against a product using a similar coated-bead architecture.

What formulations are protected by US 6,913,768?

The patent protects two principal dosage-form designs.

Coated-core formulations

Claims 4, 21-24, 29, 30, 35, and 37 cover a core containing amphetamine that is surrounded by a sustained-release coating. The coating can include ethyl cellulose or another water-insoluble polymer.

A typical covered architecture would include:

An inert or active core.
An amphetamine-containing layer.
A sustained-release outer coating.
Optional dissolution-regulating agents.

This structure is consistent with multiparticulate extended-release capsules, including bead-based products.

Matrix formulations

Claims 16-18 and related claims cover sustained-release matrices. Claim 17 identifies ethyl cellulose as a matrix component.

A matrix product may distribute the active ingredient through a polymeric or waxy carrier rather than placing the drug in a separately coated pellet. The matrix must still achieve the claimed release and PK properties.

First-order and pH-independent release

Claims 25 and 26 address a first-order dissolution profile. Claim 31 addresses pH-independent dissolution release.

These limitations matter because they shift the analysis from the identity of the excipient to the measured release behavior. A formulation using a different polymer could face infringement risk if it satisfies the broader material alternatives and the specified performance conditions.

How strong is the patent estate for mixed amphetamine salts?

The patent estate was technically broad but legally vulnerable in several ways.

Strengths

The patent had several commercially relevant strengths:

It covered the racemic dextroamphetamine/levoamphetamine combination.
It identified the four-salt mixed amphetamine formulation.
It claimed both coated-core and matrix systems.
It used multiple independent pharmacokinetic definitions.
It included broad excipient alternatives.
It covered both composition and method-of-treatment claims.
It included narrow ethyl-cellulose claims that mapped closely to commercial extended-release bead technologies.

The multiple claim formats created several potential infringement theories. A generic could avoid one PK limitation while still encountering another claim based on slope, AUC/Cmax, dosage-form structure, or dissolution behavior.

Weaknesses

The principal weaknesses were equally significant:

The claims depend heavily on human PK testing.
“Substantially the same” and “directly proportional” introduce construction questions.
The claims incorporate Figure 1 as a performance reference.
The broad excipient list may create enablement and written-description pressure at the outer boundaries.
Several claims, as reproduced, contain apparent typographical or dependency errors.
The patent does not claim a single indispensable chemical structure.
A competitor could pursue a different release mechanism and target a different PK profile.
The ordinary patent term has expired.

The PK limitations also create infringement-proof complications. A plaintiff would generally need reliable comparative data from the accused product, with attention to dose, patient population, sampling schedule, assay methodology, and statistical treatment.

When did US Patent 6,913,768 lose exclusivity?

The patent’s ordinary US term was approximately 20 years from its relevant nonprovisional filing date. Public patent records identify a 2001 US filing and a 2005 grant. On that basis, the patent expired around January 2021, before the current generic market matured.

The patent should not be treated as an active US exclusion right without checking the USPTO Patent Center record for any patent-term adjustment, terminal disclaimer, or other recorded event. The expiration analysis must also be separated from FDA regulatory exclusivity. Patent expiration and FDA exclusivity are independent legal mechanisms.

The patent is no longer a normal basis for blocking a new ANDA or generic launch. Historical settlements or commercial agreements cannot revive an expired patent.

What was the Orange Book status of Adderall XR?

Adderall XR is the principal branded product associated with this patent landscape. The product contains mixed amphetamine salts in an extended-release capsule and was approved by FDA under NDA 21-303.

FDA Orange Book analysis should distinguish:

Listed patents for the reference product.
Patent certifications submitted by ANDA applicants.
Regulatory exclusivity.
Actual patent enforceability.
Litigation or settlement restrictions.

US 6,913,768 was historically relevant to the Orange Book and ANDA challenge environment for extended-release mixed amphetamine salts. The Orange Book status must be checked by product and edition because listings, delistings, and expiration dates change over time. FDA’s Orange Book does not itself decide infringement or validity. It records patent information supplied under the Hatch-Waxman framework.[1]

Which companies challenged the Adderall XR patent estate?

The extended-release mixed amphetamine salts market attracted ANDA activity from multiple generic manufacturers, including Teva, Actavis, Barr, Impax, Sandoz, and other applicants over time. Litigation and settlement terms varied by applicant, patent, dosage strength, and launch date.

A Paragraph IV certification against an Orange Book patent can trigger a 30-month stay if the NDA holder or patent owner files suit within the statutory period. That stay delays FDA approval but does not necessarily extend the patent term. A first-filer may also receive 180-day generic exclusivity, subject to statutory forfeiture rules.

The existence of an ANDA challenge does not establish that the patent was invalid. It establishes that the applicant alleged invalidity, unenforceability, or noninfringement. The disposition depends on the court record, settlement documents, and FDA approval history.

What generic entry risks existed?

Before expiration, a generic applicant faced several possible risks.

Literal infringement risk

A product could face literal infringement if it:

Used mixed dextro-/levo-amphetamine salts.
Used one of the listed sustained-release materials.
Used a coated-core or matrix architecture.
Produced the claimed plasma profile or numerical PK ranges.

Doctrine-of-equivalents risk

A non-listed polymer or functionally similar coating could still raise an equivalents issue. That risk would depend on prosecution-history estoppel, claim amendments, the disclosed alternatives, and whether the proposed substitute performs substantially the same function in substantially the same way.

Regulatory litigation risk

Even if a patent was weak on validity, litigation could delay approval through the Hatch-Waxman stay. This created launch-timing exposure separate from ultimate infringement liability.

Commercial launch risk

A generic company might choose:

A paragraph IV launch before final judgment.
A launch after settlement.
A non-infringing formulation with a different release profile.
A product launch after patent expiration.

The commercial decision depended on litigation cost, expected damages, market share, tentative approval status, and the probability of a preliminary injunction.

How does US 6,913,768 compare with related amphetamine patents?

Patent category	Primary protection	Risk profile
Mixed amphetamine salt composition patents	Salt identity and combination	Strongest where claims map to the four-salt product
Controlled-release formulation patents	Coatings, matrices, polymers, release behavior	Central relevance of US 6,913,768
PK-profile patents	AUC, Cmax, slope, 12-hour profile	Testing-intensive and fact-dependent
Method-of-use patents	ADHD treatment using the formulation	Often secondary to composition claims
Manufacturing patents	Layering, coating, pellet formation, capsule filling	Can create process-specific risk
Later formulation patents	Alternative release technologies or dosing schedules	May create post-expiration commercial differentiation

US 6,913,768 is primarily a formulation and pharmacokinetic patent. It is not a patent on amphetamine as a molecule. It also does not make every extended-release amphetamine product infringing. The accused product must satisfy the required active-ingredient, release-system, and performance limitations.

What is the current competitive landscape?

The US market includes branded Adderall XR and multiple generic mixed amphetamine salts extended-release products. The commercial barriers now arise mainly from:

Controlled-substance manufacturing quotas.
DEA registration and supply controls.
API sourcing.
Manufacturing capacity for coated multiparticulates.
Bioequivalence requirements.
Product shortages.
Retail and payer substitution.
State and federal controlled-substance compliance.

The expired patent no longer supplies the principal barrier. Manufacturing know-how can still matter commercially, especially for consistent release profiles and acceptable fed/fasted performance, but it is not equivalent to an active composition patent.

What patent litigation affects US 6,913,768 today?

Because the patent has expired, new infringement litigation based solely on US 6,913,768 would generally be limited to historical conduct occurring before expiration. The practical issues are:

Whether a prior product infringed during the enforceable term.
Whether damages are time-barred.
Whether a settlement released historical claims.
Whether related patents remained active.
Whether the accused conduct occurred during a valid Orange Book stay.

Any current litigation assessment must rely on PACER, USPTO Patent Center, FDA Orange Book history, and the relevant settlement agreements. The patent number alone does not establish an active litigation threat.

Key Takeaways

US 6,913,768 covers sustained-release mixed dextroamphetamine/levoamphetamine formulations.
The central limitations are PK performance, dissolution behavior, and release-system structure.
The patent specifically reaches the four-salt mixed amphetamine formulation in narrower claims.
Ethyl cellulose, coated cores, matrices, first-order release, and pH-independent dissolution are important narrowing features.
Claims 1, 7, 9, 12, 14, 15, and 35 are the main independent or quasi-independent protection centers.
The patent’s ordinary US term expired around January 2021.
It is no longer a current US patent barrier to generic entry.
Historical Paragraph IV challenges and Orange Book litigation were commercially important but do not extend the expired patent.
Current competitive barriers are regulatory, manufacturing, supply-related, and commercial rather than based on this patent.
The supplied claim text contains apparent transcription errors that should not be used as the controlling legal text.

FAQs

Does US 6,913,768 cover all Adderall XR-like products?

No. It covers products that satisfy the specific active-ingredient, sustained-release, and PK or dissolution limitations. A product with a different release mechanism or profile may avoid the claims.

Does using ethyl cellulose automatically create infringement?

No. Ethyl cellulose is only one claim element. The product must also satisfy the applicable amphetamine, dosage-form, and performance limitations.

Are the AUC and Cmax values in the supplied claims reliable?

The numerical values should be checked against the issued patent and prosecution record. The supplied text contains apparent unit and typographical errors, including inconsistent units for AUC and Cmax.

Can a generic manufacturer rely on patent expiration without an Orange Book review?

No. Expiration of this patent does not establish that all related patents have expired. A complete launch analysis must review the full Orange Book patent set and any later formulation or manufacturing patents.

Is the four-salt amphetamine mixture itself still patented?

The amphetamine salts are not protected by US 6,913,768 today because the patent term has expired. Other patents, regulatory controls, or manufacturing rights could have different status.

References

U.S. Food and Drug Administration. (2025). 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
United States Patent and Trademark Office. (2005). U.S. Patent No. 6,913,768, Controlled release amphetamine formulations. https://patents.google.com/patent/US6913768B2/en
U.S. Food and Drug Administration. (2007). Adderall XR prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/
United States Patent and Trademark Office. (2025). Patent Center. https://patentcenter.uspto.gov/
21 U.S.C. § 355. (2025). New drugs. https://www.law.cornell.edu/uscode/text/21/355
35 U.S.C. §§ 154, 156. (2025). Patent term and extension. https://www.law.cornell.edu/uscode/text/35/154

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
African Regional IP Organization (ARIPO)	2030	⤷ Start Trial
Austria	495731	⤷ Start Trial
Australia	2003272619	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,913,768

Summary for Patent: 6,913,768