US Patent 4,673,563: Scope, Claims, Expiration, and Adenosine Patent Landscape

US Patent 4,673,563 covers the intravenous use of adenosine to treat and diagnose supraventricular tachycardia caused by re-entry in the atrioventricular node. Its claims are method-of-treatment and method-of-diagnosis claims, not composition, formulation, manufacturing, or device claims. The patent issued on June 16, 1987, and its pre-URAA 17-year term expired on June 16, 2004. It no longer creates a US barrier to generic adenosine injection, branded adenosine products, or current FDA-approved dosing practices. [1, 2]

What does US Patent 4,673,563 cover?

The patent covers administering adenosine intravenously to a human patient with a specified type of supraventricular tachycardia and using the resulting restoration of sinus rhythm as a therapeutic or diagnostic endpoint.

Item	Patent scope
Patent	US 4,673,563
Subject	Intravenous adenosine for supraventricular tachycardia
Core mechanism	Re-entry in the AV node
Patient	Human
Route	Intravenous
Claimed dose range	0.01-0.25 mg/kg
Specific dose	1-8 mg
Preferred dose	About 0.06 mg/kg
Claimed conditions	Wolff-Parkinson-White syndrome and reciprocating junctional tachycardia
Claim categories	Treatment and diagnosis
Issue date	June 16, 1987
Patent term	17 years from issue under pre-URAA rules
Expiration	June 16, 2004
Current enforceability	Expired

The patent does not claim adenosine as a new chemical compound. It does not claim an adenosine salt, injectable formulation, vial, syringe, manufacturing process, dosing device, or broad treatment of all arrhythmias.

How should the ten claims be classified?

The claims divide into two groups: claims 1-5 cover treatment, while claims 6-10 cover diagnosis.

Claims 1-5: Therapeutic use

Claim 1 is the broadest independent treatment claim. It requires all of the following:

A human patient.
Supraventricular tachycardia.
A tachycardia caused by re-entry in the AV node.
Intravenous administration.
Adenosine.
A dose of 0.01-0.25 mg/kg.
A dose sufficient to restore normal rhythm.

Claims 2 and 3 narrow claim 1 by identifying particular tachycardias:

Claim 2: Wolff-Parkinson-White syndrome.
Claim 3: Reciprocating junctional tachycardia.

Claims 4 and 5 narrow the dose limitation:

Claim 4: 1-8 mg.
Claim 5: approximately 0.06 mg/kg.

Because these are dependent claims, they retain every limitation of claim 1. Claim 4 is therefore not a standalone claim to any 1-8 mg intravenous adenosine use. It applies only when the patient also has AV-node re-entry supraventricular tachycardia and the dose is sufficient to restore normal rhythm.

Claims 6-10: Diagnostic use

Claim 6 is an independent diagnostic method claim. It requires:

A human patient with suspected or actual supraventricular tachycardia caused by AV-node re-entry.
Intravenous administration of adenosine.
A dose of 0.01-0.25 mg/kg.
Monitoring the heartbeat.
Observing restoration of normal sinus rhythm.
Determining the existence of the tachycardia.

Claims 7 and 8 narrow claim 6 to Wolff-Parkinson-White syndrome and reciprocating junctional tachycardia. Claims 9 and 10 add the 1-8 mg and approximately 0.06 mg/kg dose limitations.

The diagnostic claims are narrower in operational terms than the treatment claims because they require monitoring and a diagnostic determination. A commercial product would not infringe merely because it contains adenosine. The relevant conduct would be the claimed intravenous administration and clinical use.

What is the strongest claim in US Patent 4,673,563?

Claim 1 is the principal enforcement claim because it covers the therapeutic method without limiting the disease to one named syndrome or the dose to one narrower amount. Its limitations still materially narrow the scope:

It is limited to AV-node re-entry.
It requires intravenous administration.
It applies only to humans.
It requires the specified weight-based dose range.
The dose must be sufficient to restore normal rhythm.

Claim 6 is the principal diagnostic claim. It adds the monitoring and determination steps, making it narrower than claim 1 in practical use.

The most commercially relevant dependent claims are claims 4 and 5. Claim 4 corresponds to a fixed-dose range, while claim 5 identifies approximately 0.06 mg/kg as a preferred weight-based dose. Current clinical adenosine practice commonly uses fixed rapid intravenous boluses, including an initial 6 mg dose followed by 12 mg if necessary, subject to product labeling and clinical circumstances. [3]

What limitations materially restrict infringement?

The patent does not cover every use of adenosine in cardiology. The following limitations are important.

AV-node re-entry

The claims require supraventricular tachycardia caused by re-entry in the AV node. Uses directed to other arrhythmias, such as atrial fibrillation, atrial flutter, ventricular tachycardia, or non-reentrant tachycardias, fall outside the express claim language.

The FDA label for adenosine injection states that adenosine is indicated for conversion of paroxysmal supraventricular tachycardia to sinus rhythm, including PSVT associated with Wolff-Parkinson-White syndrome. It is not intended to convert atrial fibrillation, atrial flutter, or ventricular tachycardia to sinus rhythm. [3]

Intravenous administration

Oral, intramuscular, subcutaneous, transdermal, inhaled, or other nonintravenous administration is outside the literal route limitation. The claim does not expressly require a particular intravenous device, infusion speed, catheter location, or flush technique.

Adenosine

The claims require adenosine itself. A different pharmacologic agent, including regadenoson, does not satisfy this limitation solely because it acts on adenosine receptors. Regadenoson is a distinct active ingredient and has a different primary clinical indication and regulatory history.

Dose

Claim 1 requires 0.01-0.25 mg/kg. A dose outside that range would not literally satisfy the express dose limitation, although infringement analysis could involve equivalents in a live patent dispute. That issue has no current commercial significance because the patent expired in 2004.

Restoration of rhythm

The treatment claims require administration of a dose sufficient to restore normal rhythm. The diagnostic claims require monitoring for restoration of normal sinus rhythm and determining the existence of the tachycardia. A failed administration that does not restore rhythm raises a claim-scope issue under the literal language, although method claims can present fact-specific questions concerning intended results and performance of the claimed steps.

When did US Patent 4,673,563 lose exclusivity?

The patent expired on June 16, 2004, 17 years after issuance. It was issued before the Uruguay Round Agreements Act changed the US patent term to 20 years from the earliest effective filing date. The patent therefore falls under the pre-URAA term rule applicable to patents issued before June 8, 1995. [1, 4]

Milestone	Date
Patent issued	June 16, 1987
Statutory term	17 years from issue
Expiration	June 16, 2004
Post-expiration status	Public domain method

No patent-term extension or patent-term adjustment is relevant to the expired patent term. The patent cannot support an injunction, damages claim, Paragraph IV litigation, or a current regulatory stay.

What is the Orange Book status of US Patent 4,673,563?

The Orange Book identifies patents and exclusivity associated with approved drug products. A patent listing does not extend the patent term and does not convert an expired method patent into an active right. [5]

For adenosine injection, the relevant regulatory issue is whether any listed patent remains unexpired for the applicable reference product. US Patent 4,673,563 expired in 2004. It therefore cannot currently block approval of an abbreviated new drug application or support a 30-month stay under the Hatch-Waxman framework.

A current generic applicant would not need to delay approval because of this patent. Any historical Orange Book listing would now have no blocking effect.

Are there current Paragraph IV challenges involving this patent?

No current Paragraph IV strategy can be directed to US Patent 4,673,563 because the patent is expired. Paragraph IV certifications concern patents listed for an approved drug that the applicant asserts are invalid, unenforceable, or not infringed. A Paragraph IV notice is commercially meaningful only while the relevant patent remains capable of delaying approval or supporting litigation. [5, 6]

The practical status is:

Issue	Current position
Paragraph IV challenge needed against this patent	No
30-month stay based on this patent	No
Current infringement action based on this patent	No viable action
Generic launch blocked by this patent	No
Declaratory judgment value	Limited to historical issues

A generic applicant could still face other regulatory or patent issues involving a specific reference product, but those issues would not arise from the expired term of US 4,673,563.

What formulations are protected by this patent?

None are protected as formulations. The patent claims the use of adenosine, not the composition of an injectable product.

The claims do not specify:

Concentration in mg/mL.
pH.
Buffer system.
Preservative.
Container closure.
Syringe or vial configuration.
Sterilization method.
Stability profile.
Excipient.
Manufacturing process.
Packaging system.
Delivery catheter.

A commercial adenosine product may contain formulation and manufacturing information protected by separate patents, trade secrets, regulatory exclusivity, or know-how. Those rights would need to be analyzed independently. US Patent 4,673,563 itself does not create such protection.

Does the patent create biosimilar risk?

No. Adenosine is a small-molecule drug, not a biological product. The relevant competitive pathway is the ANDA generic pathway, not the biosimilar pathway under the Public Health Service Act.

The principal competitive risks are:

ANDA approval for adenosine injection.
Label-compliant generic substitution.
Contract manufacturing.
Hospital purchasing and group purchasing organization pricing.
Supply continuity and shortage exposure.
Formulation or packaging differentiation.

Regadenoson products, including Lexiscan, are not biosimilars or generic versions of adenosine. They are separate small-molecule products with distinct active ingredients and indications.

How does adenosine compare with competing products?

Product or therapy	Active ingredient	Primary role	Relationship to US 4,673,563
Adenosine injection	Adenosine	Rapid conversion of PSVT	Direct subject of the patent
Regadenoson	Regadenoson	Pharmacologic stress imaging	Separate molecule and indication
Verapamil	Verapamil	Alternative AV nodal blockade	Not covered
Diltiazem	Diltiazem	Alternative rate-control therapy	Not covered
Beta blockers	Various	Rate control and arrhythmia management	Not covered
Catheter ablation	Procedure	Definitive treatment for selected re-entry circuits	Not covered

Adenosine has a short plasma half-life and is administered as a rapid intravenous bolus. Its commercial value comes from acute emergency and diagnostic use rather than chronic therapy. The patent’s expiration removed any method-of-use exclusivity associated with that clinical application.

Which companies are challenging the patent?

There is no current challenger required because the patent expired nearly two decades ago. Generic adenosine manufacturers may compete commercially, but current market participation is not a patent challenge to US 4,673,563.

The relevant distinction is:

A historical ANDA filing may have addressed the patent while it was listed or potentially enforceable.
A current generic manufacturer can rely on the expired status of the patent.
Current competition is primarily regulatory, manufacturing, supply-chain, and pricing-based.

A reliable assessment of historical Paragraph IV notices or patent litigation would require a case-by-case review of FDA records, district court dockets, and the patent’s prosecution and litigation history. No current legal barrier follows from the patent itself.

What is the geographic coverage?

US Patent 4,673,563 provides only US rights. It has no direct legal effect in Canada, Europe, Japan, China, or other jurisdictions.

Foreign protection, if any, would have depended on separately filed national or regional applications. Any corresponding foreign patent would have had an independent filing date, term, claim set, and expiration date. The expiration of the US patent did not automatically determine foreign status.

For a global launch analysis, the relevant questions are:

Whether foreign counterparts were filed.
Whether those counterparts issued.
Whether they covered treatment, formulation, or manufacturing.
Whether any supplementary protection certificate or pediatric extension applied.
Whether local regulatory exclusivity survived patent expiration.

How strong is the patent estate for adenosine today?

The estate associated with this patent is commercially weak because the central US patent expired in 2004 and covers only a clinical method. It has no remaining blocking power against generic adenosine injection.

Estate dimension	Assessment
Active US composition patent	No protection from this patent
Active US treatment patent	No protection from this patent
Formulation coverage	None in the claims provided
Manufacturing coverage	None in the claims provided
Device coverage	None in the claims provided
Biosimilar barrier	Not applicable
Generic entry risk	High
Current injunction risk	None from this patent
US revenue protection	None from this patent
Strategic value	Historical, not blocking

The remaining commercial barriers are operational rather than patent-based. These may include sterile injectable manufacturing capacity, quality-system compliance, procurement contracts, shortage management, and FDA approval requirements.

What patent litigation or settlement agreements affect the patent?

An expired patent cannot support new infringement litigation that seeks prospective exclusivity. Historical litigation or settlement agreements could still be relevant for understanding generic entry timing, licensing economics, or prior regulatory strategy, but they do not revive the patent or restrict present-day use.

There is no current settlement value inherent in the patent. Any prior license would need to be examined for surviving contractual terms, but a private agreement cannot extend the patent’s statutory exclusion against nonparties.

Key Takeaways

US Patent 4,673,563 covers intravenous adenosine for AV-node re-entry supraventricular tachycardia.
Claims 1-5 are treatment claims; claims 6-10 are diagnostic claims.
The patent covers humans, intravenous administration, adenosine, and specified dose ranges.
Claims 2, 3, 7, and 8 narrow the disease to Wolff-Parkinson-White syndrome or reciprocating junctional tachycardia.
Claims 4, 5, 9, and 10 narrow the dosage.
The patent does not claim adenosine composition, formulation, manufacturing, packaging, or delivery devices.
The patent expired on June 16, 2004.
It cannot currently block generic adenosine injection or support a Paragraph IV litigation strategy.
Adenosine is a small-molecule drug, so biosimilar analysis does not apply.
Current commercial risk is generic competition, not patent enforcement.
Any foreign or formulation protection must be analyzed separately from US Patent 4,673,563.

FAQs

Can a generic adenosine manufacturer practice the claims of US Patent 4,673,563?

Yes. The patent expired in 2004, so its claimed methods are no longer enforceable in the United States.

Does US Patent 4,673,563 cover the 6 mg adenosine dose?

A 6 mg dose can fall within claim 4's 1-8 mg range, but only when the other claim limitations are satisfied. The patent is expired.

Does the patent cover adenosine for atrial fibrillation?

No express claim covers atrial fibrillation. The claims are directed to supraventricular tachycardia caused by AV-node re-entry.

Is Wolff-Parkinson-White syndrome itself patented by this patent?

No. The patent claims a method of administering intravenous adenosine to treat or diagnose specified tachycardia associated with the syndrome. It does not claim the syndrome.

Could a new formulation of adenosine receive patent protection?

Potentially, but any protection would require a separate patent with patentable subject matter, such as a novel formulation, stability profile, delivery system, manufacturing process, or other qualifying feature. US Patent 4,673,563 does not provide that protection.

References

United States Patent and Trademark Office. (1987). U.S. Patent No. 4,673,563: Treatment of supraventricular tachycardia with adenosine.
United States Code, 35 U.S.C. § 154. (2024). Patent term and patent rights.
U.S. Food and Drug Administration. (2023). Adenosine injection prescribing information.
United States Patent and Trademark Office. (2024). Patent term calculator and patent term guidance.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
United States Code, 21 U.S.C. § 355(j). (2024). Abbreviated applications and patent certifications.

Details for Patent: 4,673,563

Summary for Patent: 4,673,563