United States Patent 4,451,458: Scope, Claims, Expiration, and Patent Landscape for Dihydroergotamine-Heparin Thrombosis Prophylaxis

U.S. Patent No. 4,451,458 covers a narrow combination of dihydroergotamine and heparin for preventing post-operative thrombosis. Its claims require specific active ingredients, dose ranges, parenteral administration for the method claim, and repeated administration two to four times daily. The patent issued in 1984 under the pre-Uruguay Round patent-term regime and is therefore expired. It does not create a current U.S. barrier to generic dihydroergotamine, heparin, or other thrombosis-prophylaxis products.

What does U.S. Patent 4,451,458 protect?

The patent protects two related subject matters:

A treatment method using dihydroergotamine and heparin together.
A unit-dose pharmaceutical composition containing both agents.

The disclosed combination is materially narrower than a general claim to either dihydroergotamine or heparin. It does not cover:

Dihydroergotamine alone.
Heparin alone.
Any dose of dihydroergotamine outside the claimed approximate 0.5 mg unit dose.
Any heparin dose below 2,500 IU or above 5,000 IU under claim 2.
Oral or transdermal administration under claim 1, because the method requires parenteral administration.
Use for migraine, cluster headache, peripheral vascular disease, or indications other than post-operative thrombosis prophylaxis, unless the use also satisfies every limitation of the claim.

The claims are reproduced in substance below.

Claim	Claim type	Required dihydroergotamine	Required heparin	Other limitations
1	Method of treatment	About 0.5 mg per unit dose	About 2,500-5,000 IU per unit dose	Mammals; prophylaxis of post-operative thrombosis; parenteral administration; two to four doses daily
2	Pharmaceutical composition	About 0.5 mg per unit dose	About 2,500-5,000 IU per unit dose	Unit dosage form; useful for post-operative thrombosis prophylaxis
3	Pharmaceutical composition	About 0.5 mg per unit dose	About 5,000 IU per unit dose	Unit dosage form; useful for post-operative thrombosis prophylaxis

How should claim 1 be construed?

Claim 1 is a combination-treatment claim with multiple cumulative limitations. A potentially infringing practice would need to satisfy all of the following elements:

Administration to a mammal.
A prophylactic purpose.
Prevention of post-operative thrombosis.
Parenteral administration.
Dihydroergotamine and heparin administered in conjunction.
Approximately 0.5 mg of dihydroergotamine per unit dose.
Approximately 2,500-5,000 IU of heparin per unit dose.
Administration two to four times each day.

The word "comprising" makes the claim open-ended. A product or regimen containing the claimed combination could include additional excipients, active agents, or treatment steps without automatically falling outside the claim. The presence of an additional anticoagulant would not, by itself, avoid the claim.

The phrase "in conjunction with" is broader than an express requirement that the two drugs be mixed in the same syringe or container. The claim does not expressly require a single combined injection. Separate injections administered as part of the same prophylactic regimen could potentially satisfy the conjunction requirement if the timing and treatment protocol establish coordinated administration.

The claim does not specify:

A particular heparin salt.
A particular injection route.
A syringe, vial, infusion bag, or other delivery device.
A particular post-operative procedure.
A defined interval between the dihydroergotamine and heparin doses.
A particular patient population beyond mammals undergoing post-operative thrombosis prophylaxis.

Those omissions broaden the claim in some respects. The dose and frequency limitations narrow it substantially.

What does "about 0.5 mg" mean?

"About" introduces a range of tolerance rather than an absolute mathematical requirement. The exact scope would depend on the specification, prosecution history, technical practice at the filing date, and any litigation construction. A formulation containing materially more or less than 0.5 mg would present a stronger non-infringement position than one using a small manufacturing deviation.

The claim also refers to a "unit dose." A package containing multiple doses would not avoid the claim if each administered dose contains the specified quantities. Conversely, a continuous infusion would raise a claim-construction issue because the claim is drafted around repeated unit doses administered two to four times daily.

What do composition claims 2 and 3 cover?

Claims 2 and 3 are composition claims, not treatment-method claims. They focus on the physical pharmaceutical product and do not expressly require proof that a patient was actually treated.

Claim 2 covers a unit dosage form containing:

About 0.5 mg of dihydroergotamine; and
About 2,500-5,000 IU of heparin.

Claim 3 covers the same dihydroergotamine amount with approximately 5,000 IU of heparin.

Claim 3 is nested within claim 2 because 5,000 IU falls at the upper boundary of the range in claim 2. Its practical role is as a separate, more specific claim directed to the 5,000 IU embodiment. If claim 2 were successfully challenged on a range-related basis, claim 3 could remain as a more particular fallback, subject to the same validity and enforceability requirements.

The phrase "useful in the prophylactic treatment" is primarily functional language describing the intended pharmaceutical use. It does not convert the claims into a general monopoly over all pharmaceutical products that contain either ingredient. The product must still contain the claimed quantities in unit dosage form.

What technical subject matter is outside the claims?

The following products and regimens generally fall outside the literal wording unless an additional doctrine or claim-construction issue applies:

Product or regimen	Reason it is outside the literal claim set
Dihydroergotamine injection without heparin	Missing heparin
Heparin injection without dihydroergotamine	Missing dihydroergotamine
0.5 mg dihydroergotamine with 1,000 IU heparin	Below claim 2's stated heparin range
0.5 mg dihydroergotamine with 7,500 IU heparin	Above claim 2's stated heparin range
Oral dihydroergotamine-heparin product	Claim 1 requires parenteral administration; composition claims may raise separate product questions
Dihydroergotamine nasal spray	Does not match the claimed unit-dose combination
Migraine treatment using dihydroergotamine alone	Missing the heparin and thrombosis-prophylaxis limitations
Continuous low-dose infusion	Does not naturally match the claimed unit-dose and frequency structure
Post-operative thrombosis treatment after thrombosis has occurred	Claim 1 is directed to prophylaxis, not treatment of established thrombosis

When did U.S. Patent 4,451,458 expire?

U.S. Patent 4,451,458 issued in 1984. Patents issued before the modern patent-term transition generally received a term of 17 years from issuance under the law then in effect. On that basis, the patent expired in approximately 2001, subject to any patent-specific terminal disclaimer, reexamination certificate, or other adjustment shown in the official patent record.

Because the patent is more than two decades beyond that term, it is not an enforceable U.S. patent today. The claims cannot support a current infringement action or block a generic launch.

Milestone	Date or status
U.S. patent number	4,451,458
Issue year	1984
Governing historical term	Generally 17 years from issue for this patent class
Estimated expiration	2001
Current U.S. enforceability	Expired
Current Paragraph IV exposure	None based on this patent
Current patent-term-extension relevance	None apparent from the patent's age

The definitive legal status should be confirmed in the USPTO Patent Center and the official patent file. The commercial conclusion remains unchanged: a 1984 patent of this type is no longer an active U.S. exclusivity right.

What is the Orange Book status of Patent 4,451,458?

Patent 4,451,458 should not be treated as a current Orange Book barrier.

The Orange Book lists patents submitted by sponsors for approved drug products under the Hatch-Waxman framework. A patent directed to a historical dihydroergotamine-heparin combination would need to be associated with a specific approved drug product to have Orange Book relevance. The existence of the patent number alone does not establish an Orange Book listing.

The key regulatory distinction is:

Patent 4,451,458: an expired combination patent.
Dihydroergotamine products: separately approved products, including injectable and nasal formulations.
Heparin products: separately approved anticoagulant products.
Current generic approval: governed by the active patents and exclusivities associated with the reference-listed drug, not by an expired combination patent.

FDA-approved dihydroergotamine products have historically been used primarily for acute migraine treatment. That approved-use history is distinct from the post-operative thrombosis-prophylaxis combination claimed in Patent 4,451,458. FDA product labeling and the current Orange Book must be reviewed at the product level rather than by active ingredient alone. [1, 2]

Are there Paragraph IV challenges to this patent?

No current Paragraph IV challenge can have operative commercial significance against Patent 4,451,458 because the patent has expired.

A Paragraph IV certification is relevant when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or will not be infringed. Once the patent term ends, an applicant does not need to defeat the patent through Paragraph IV litigation to launch on account of that patent. Any historical ANDA dispute involving the patent would therefore be closed as a practical matter by expiration.

The more relevant current questions concern:

Active patents listed against a specific dihydroergotamine reference product.
Any unexpired formulation or device patents.
Regulatory exclusivity periods.
State or federal product-liability exposure.
Manufacturing and supply requirements for injectable products.

Does the patent create biosimilar risk?

No. Patent 4,451,458 does not create a biosimilar issue.

Dihydroergotamine is a small-molecule ergot derivative, and heparin is a complex biologic-derived polysaccharide anticoagulant. A product containing these ingredients would not ordinarily be analyzed as a biosimilar to dihydroergotamine. Dihydroergotamine products are generally addressed through the small-molecule drug approval framework, including ANDAs where an appropriate reference product and dosage form exist.

Heparin has its own regulatory and manufacturing complexity. Unfractionated heparin is subject to source-material controls, characterization, impurity controls, potency testing, and supply-chain requirements. Those issues can create entry barriers, but they do not revive or extend Patent 4,451,458.

What formulation patents are relevant to dihydroergotamine?

Patent 4,451,458 is a combination-composition patent. It is not a broad dihydroergotamine formulation patent.

Potentially relevant patent categories for dihydroergotamine products include:

Injectable solutions.
Nasal sprays.
Metered-dose delivery systems.
Stabilized ergot alkaloid formulations.
Transdermal or buccal delivery systems.
Salts and solvates.
Container-closure systems.
Device and dose-metering technology.
Manufacturing processes that improve purity or stability.

Those categories are technically separate from the claimed dihydroergotamine-heparin unit dose. An active patent in one category would require separate claim analysis. A nasal-spray patent, for example, would generally not cover an injectable combination composition unless its claims expressly reached that dosage form or formulation.

What manufacturing and intellectual-property barriers remain?

The expired patent does not remove all commercial barriers.

Dihydroergotamine manufacturing

Dihydroergotamine products may require controls over:

Ergot alkaloid impurity profiles.
Stereochemical composition.
Salt formation.
Sterility for injectable products.
Oxidation and light sensitivity.
Container compatibility.
Dose uniformity.

Heparin manufacturing

Heparin presents additional challenges involving:

Animal-source material.
Traceability.
Contamination control.
Molecular-weight distribution.
Potency and anti-factor Xa activity.
Oversulfated or other non-heparin contaminants.
Supplier qualification and batch consistency.

These are regulatory and operational barriers, not surviving patent claims under Patent 4,451,458. A competitor may avoid the patent entirely yet still face substantial development, validation, and FDA-compliance costs.

How strong is the patent estate for this combination?

The patent estate represented by U.S. Patent 4,451,458 is commercially weak today because the patent is expired. Historically, the claims were stronger against an exact-match product than against a modified regimen.

Risk scenario	Historical risk under the claims	Current risk
0.5 mg dihydroergotamine plus 5,000 IU heparin, parenterally, two to four times daily	High literal-overlap potential	None because the patent expired
Same ingredients but heparin outside 2,500-5,000 IU	Lower literal-overlap potential	None under this patent
Dihydroergotamine alone	No literal overlap	None
Heparin alone	No literal overlap	None
Oral combination	Generally outside claim 1	None
Injectable combination for migraine	Missing the claimed thrombosis-prophylaxis purpose under claim 1; composition-claim issues would depend on product structure and claim construction	None
Nasal dihydroergotamine	Outside the claimed combination dosage form	None

The patent's historical value was concentrated in a narrow product concept: a preconfigured unit dose containing both active agents. It did not establish broad exclusivity over thrombosis prophylaxis, heparin, dihydroergotamine, injectable delivery, or post-operative care.

What litigation or settlement agreements affect the patent?

No current litigation or settlement can preserve exclusivity after expiration. A settlement agreement could have imposed private obligations during the patent term, but it could not extend the patent's statutory exclusionary period against unrelated parties.

For present commercial diligence, the relevant records are:

USPTO Patent Center for prosecution, maintenance, reexamination, and terminal-disclaimer history.
PACER and district-court docket records for infringement actions.
FDA Orange Book records for any listed product patents.
FDA approval letters and labeling for dihydroergotamine and heparin products.

An expired patent may remain relevant as prior art, but it does not support a current patent-enforcement strategy. [2, 3]

What generic launch scenarios exist?

A generic or follow-on sponsor could pursue several routes:

A standalone dihydroergotamine product for an approved indication.
A heparin product under the applicable abbreviated or full approval pathway.
A combination product containing both ingredients, if clinically and regulatorily justified.
A modified formulation using a different dose, route, or delivery device.
A hospital-use product assembled from separately approved components.

Patent 4,451,458 would not block any of these routes today. A sponsor would still need to evaluate current Orange Book patents, formulation patents, device rights, regulatory requirements, clinical support, and manufacturing controls.

Key Takeaways

U.S. Patent 4,451,458 claims a dihydroergotamine-heparin combination for post-operative thrombosis prophylaxis.
Claim 1 requires parenteral administration, approximately 0.5 mg of dihydroergotamine, 2,500-5,000 IU of heparin, and two to four administrations daily.
Claims 2 and 3 cover unit-dose compositions; claim 3 specifically targets approximately 5,000 IU of heparin.
The patent does not broadly cover dihydroergotamine, heparin, migraine treatment, or all thrombosis-prophylaxis products.
The patent issued in 1984 and expired approximately in 2001 under the historical 17-year-from-issuance term.
It presents no current Paragraph IV, Orange Book, biosimilar, or patent-enforcement barrier.
Remaining market barriers arise from FDA approval, sterile manufacturing, heparin quality controls, formulation stability, supply qualification, and any separate active patents.

FAQs

Can a company market dihydroergotamine and heparin together today?

Yes, Patent 4,451,458 is expired. The company would still need to satisfy FDA approval, labeling, manufacturing, and clinical requirements applicable to the proposed combination.

Does the patent cover a 0.5 mg dihydroergotamine injection by itself?

No. The claims require heparin as part of the claimed combination.

Does 5,000 IU of heparin fall within claim 2?

Yes. Claim 2 recites approximately 2,500-5,000 IU, and claim 3 separately recites approximately 5,000 IU.

Is a dihydroergotamine nasal spray covered by Patent 4,451,458?

Not on the face of the supplied claims. The claims are directed to a dihydroergotamine-heparin unit dose, and claim 1 also requires parenteral administration.

Can an expired patent be cited in a new patent application?

Yes. The patent can operate as prior art if legally available against a later application. Its expiration does not remove its potential prior-art relevance.

References

U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.
U.S. Food and Drug Administration. (2024). D.H.E. 45 (dihydroergotamine mesylate) injection prescribing information. FDA.
United States Patent and Trademark Office. (2024). Patent Center: U.S. Patent No. 4,451,458. USPTO.
Patent Act, 35 U.S.C. § 154.
U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions and patent certifications. FDA.

Details for Patent: 4,451,458

Summary for Patent: 4,451,458