US Patent 4,536,386: Claim Scope, Expiration, Orange Book Status, and Metoclopramide Patent Landscape

US Patent 4,536,386 protected a high-dose metoclopramide regimen for preventing or alleviating cisplatin-induced emesis in human cancer patients. The patent covered treatment timing, cumulative dose, intermittent dosing, continuous infusion, intravenous administration, cisplatin dose stratification, and the metoclopramide monohydrochloride monohydrate salt. It was issued on August 20, 1985, and its pre-Uruguay Round patent term expired on August 20, 2002, absent a term adjustment or other extension. The patent therefore has no current blocking effect in the United States.[1]

The patent was a method-of-treatment patent. It did not claim metoclopramide as a chemical compound, a general antiemetic composition, a manufacturing process, or a device.

What does US Patent 4,536,386 claim?

The independent claim covers a defined antiemetic protocol for cisplatin chemotherapy:

Claim element	Required limitation
Patient	Human cancer patient
Cause of emesis	Cisplatin chemotherapy
Active ingredient	Metoclopramide or a pharmaceutically acceptable salt
Dose	About 5 to 18 mg/kg of patient body weight
Timing	Begins about 30 minutes before cisplatin administration and continues through the post-administration period
Administration pattern	Continuous administration or 4 to 7 individually spaced doses
Dose interval	About 1.5 to 3 hours apart

A party practicing the claimed method would need to satisfy all material limitations of claim 1. A metoclopramide regimen outside the dose, timing, patient, cisplatin, or administration-pattern limitations would fall outside the literal scope of claim 1, subject to claim construction and the doctrine of equivalents.

The patent uses approximate terms such as “about,” which create a fact-dependent infringement analysis. Courts generally interpret those terms in light of the specification, disclosed examples, technical meaning, and whether a skilled person could identify the claim boundary with reasonable certainty. The patent’s claim scope is therefore broader than a mathematically exact 5-to-18 mg/kg range but does not necessarily cover every regimen close to that range.

How do claims 2 through 7 narrow the patent?

Claims 2 through 7 add specific administration or dosing limitations.

Claim 2: intravenous administration

Claim 2 requires metoclopramide to be administered intravenously in the presence of a liquid carrier. It narrows claim 1 to IV delivery and excludes oral-only administration.

The liquid-carrier limitation is technically modest. Standard injectable metoclopramide products ordinarily contain the active ingredient in an aqueous or other liquid formulation. The claim is directed primarily to the treatment method rather than to a novel injectable composition.

Claim 3: intermittent dosing

Claim 3 requires the 4-to-7-dose embodiment, with doses administered approximately 1.5 to 3 hours apart. It excludes continuous infusion.

This claim is narrower than claim 1 because claim 1 alternatively permits either continuous administration or spaced individual doses.

Claim 4: lower cisplatin exposure

Claim 4 addresses cisplatin doses of about 100 mg/m² or less. Each individually spaced metoclopramide dose contains about 1 mg/kg.

The claim therefore describes a repeated-dose protocol in which the patient receives approximately 4 to 7 mg/kg across the individual doses. Because claim 1 requires a total dose of about 5 to 18 mg/kg, the four-dose, 1 mg/kg-per-dose endpoint creates a potential internal boundary issue. A four-dose regimen totals 4 mg/kg, while claim 1 nominally begins at 5 mg/kg. The term “about” may resolve some overlap, but the dependent claim should not be assumed to cover every mathematical combination of its stated sublimitations.

Claim 5: higher cisplatin exposure

Claim 5 applies when cisplatin is administered at or above approximately 120 mg/m². Each metoclopramide dose contains about 2 to 3 mg/kg.

The claim is directed to more intensive cisplatin treatment and a higher antiemetic dose. A seven-dose regimen at 3 mg/kg per dose would total 21 mg/kg, above the nominal 18 mg/kg upper limit in claim 1. The dependent-claim language again creates an “about” and claim-dependency issue at the outer edges.

Claims 4 and 5 leave a nominal cisplatin-dose interval between approximately 100 and 120 mg/m². That gap does not remove potential coverage under claim 1, which does not impose a cisplatin-dose threshold, but it prevents claims 4 and 5 from covering every cisplatin dose.

Claim 6: metoclopramide monohydrochloride monohydrate

Claim 6 requires the monohydrochloride monohydrate salt of metoclopramide. This is a species limitation within the broader claim 1 genus covering metoclopramide and pharmaceutically acceptable salts.

The limitation is unlikely to create a meaningful present-day commercial barrier because metoclopramide salt forms and the claimed therapeutic use are no longer protected by an enforceable US patent.

Claim 7: continuous infusion

Claim 7 requires continuous infusion. It is the alternative to the spaced-dose embodiment in claim 3.

A continuous infusion protocol that satisfies the dose and timing requirements of claim 1 would have fallen within claim 7. A continuous infusion outside the 5-to-18 mg/kg total-dose range would not necessarily satisfy claim 7 because it depends from claim 1.

What is the patent expiration date for US 4,536,386?

US Patent 4,536,386 issued on August 20, 1985.[1] For a US utility patent filed before June 8, 1995, the applicable term was generally the longer of 17 years from grant or 20 years from the earliest effective US nonprovisional filing date, subject to transitional rules and any patent-term adjustment or extension.[2]

Because this patent issued under the pre-Uruguay Round regime, its ordinary term ran 17 years from issuance:

Event	Date
Patent issued	August 20, 1985
Ordinary 17-year expiration	August 20, 2002
Current enforceability	Expired

No current infringement claim can be brought based on the expired patent. Patent expiration also eliminates any present US exclusivity attributable to this patent, regardless of whether the underlying metoclopramide product remains approved or commercially sold.

What was the commercial and technical significance of the patent?

The patent’s commercial value came from converting a known antiemetic into a high-dose cisplatin-support regimen. Its technical distinction was not the discovery of metoclopramide itself. The claimed subject matter was the treatment protocol:

High cumulative metoclopramide dosing.
Administration beginning before cisplatin.
Continued treatment during the post-cisplatin period.
Repeated dosing at defined intervals or continuous infusion.
Adjustment of dose based on cisplatin intensity.

The claims were therefore vulnerable to prior-art analysis involving earlier disclosures of:

Metoclopramide’s antiemetic activity.
Cisplatin-induced nausea and vomiting.
Antiemetic use in oncology.
Repeated or continuous metoclopramide administration.
High-dose metoclopramide protocols.
Combination antiemetic treatment during chemotherapy.

The strongest patentable distinction was likely the specific dosing schedule and cisplatin-related regimen, rather than the active ingredient, salt, IV carrier, or general antiemetic indication.

How strong was the patent estate for metoclopramide and cisplatin emesis?

The estate was narrow in structure. The identified patent had seven claims, with claim 1 as the central protection. The claims were method claims with multiple cumulative limitations.

Estate characteristic	Assessment
Compound protection	Not provided by US 4,536,386
Composition protection	Not provided
Formulation protection	Minimal; claim 2 requires a liquid carrier but does not claim a novel formulation
Manufacturing protection	None
Method-of-use protection	Yes
Dose-regimen protection	Yes
IV administration protection	Yes, under claim 2
Continuous-infusion protection	Yes, under claim 7
Salt-form protection	Yes, under claim 6
Geographic scope	United States only
Current enforceability	None because the patent expired

The estate would have been easier to design around than a compound or formulation patent. Potential design-around strategies included oral administration, different dosing intervals, fewer or more administrations, total doses below or above the claimed range, use in a non-cisplatin chemotherapy setting, and administration that did not begin approximately 30 minutes before cisplatin.

A design-around analysis would still have required attention to the doctrine of equivalents and to whether the alternative regimen retained the same treatment purpose, timing, and dose function. That issue is now historical because the patent has expired.

What formulations are protected by US 4,536,386?

The patent does not claim a proprietary formulation in the conventional pharmaceutical sense.

Claim 2 covers IV administration in a liquid carrier. That limitation may encompass an injectable metoclopramide solution, but it does not require a particular excipient, concentration, pH, container, stabilizer, preservative, or release profile. Claim 6 identifies the monohydrochloride monohydrate salt but does not claim a specific dosage form or manufacturing process for that salt.

The patent therefore did not create a durable formulation barrier comparable to:

A controlled-release tablet patent.
A specific injectable composition patent.
A stability or excipient patent.
A device-assisted infusion patent.
A combination product patent.

Generic manufacturers could pursue standard metoclopramide tablets, oral solutions, or injectable products without facing a live patent claim from US 4,536,386.

What was the Orange Book status of US 4,536,386?

The patent was a method-of-use patent and could have been relevant to a New Drug Application patent listing during its term if the listed use corresponded to an approved labeling indication. Orange Book listing, however, is an FDA regulatory record and does not itself determine patent validity, enforceability, or ultimate claim scope.[3]

The relevant present-day conclusions are:

The patent is expired.
It cannot support a current 30-month stay under Hatch-Waxman.
It cannot create current regulatory exclusivity.
Any historical Orange Book listing would have no continuing exclusionary effect after expiration.
A generic applicant cannot be forced to defer launch because of this expired patent.

FDA approval of metoclopramide products does not revive the patent. FDA labeling and patent rights operate under separate statutory systems.

Are there Paragraph IV challenges or generic entry risks?

There is no current Paragraph IV risk from US 4,536,386 because the patent expired in 2002. A Paragraph IV certification is relevant to an unexpired listed patent. It has no practical role in blocking a present-day generic launch based on this patent.

During the patent term, a generic applicant seeking approval for a product or indication potentially covered by the listed method could have used:

A Paragraph III certification, accepting delayed approval until patent expiration.
A Paragraph IV certification, asserting that the patent was invalid, unenforceable, or not infringed.
A section viii statement, where the applicant carved out a patented method from labeling, if the FDA-approved labeling and patent listing permitted that approach.

The core generic-entry risks during the term would have been:

Risk	Relevance
Literal method infringement	Required all claim limitations, including dose and timing
Induced infringement	Could arise from labeling, instructions, or promotion encouraging the regimen
Divided infringement	Potential issue where multiple actors performed separate treatment steps
Claim construction	Important because of “about,” “post administration period,” and “continuous”
Obviousness	Central validity issue for a dose-regimen patent
Enablement and written description	Relevant to the breadth of 5-to-18 mg/kg and multiple dosing formats
Regulatory patent listing	Could have delayed approval during the patent term

Today, the principal commercial risk is regulatory and clinical rather than patent-based. Metoclopramide carries significant safety restrictions, including the FDA boxed warning concerning tardive dyskinesia and limits on prolonged treatment.[4]

Which companies challenged or licensed the patent?

The patent’s front-page ownership history identifies A. H. Robins Company as the historical assignee.[1] A. H. Robins marketed Reglan, the principal US metoclopramide brand.

No reliable current basis exists to identify a live license, settlement, or active litigation proceeding involving US 4,536,386. Any historical licensing or litigation would not affect present US freedom to operate because the patent is expired.

The patent’s expiration also makes a current patent settlement commercially irrelevant unless a separate contract, trademark right, confidential know-how obligation, or successor patent remains enforceable. Patent settlements cannot extend an expired patent’s statutory term.

How does this patent compare with competing antiemetic patent estates?

US 4,536,386 should be compared with later antiemetic drugs that relied on compound, composition, formulation, and method-of-use patents.

Drug or class	Principal patent strategy	Relationship to US 4,536,386
Metoclopramide	Early compound protection followed by regimen and product patents	Same active ingredient; patent 4,536,386 focused on cisplatin dosing
Ondansetron	5-HT3 antagonist compound and therapeutic-use protection	Competing antiemetic mechanism and later-generation therapy
Granisetron	Compound, formulation, and use patents	Competing 5-HT3 antagonist estate
Aprepitant	NK1 antagonist compound and use patents	Later antiemetic class with stronger compound-based protection
Palonosetron	Long-acting 5-HT3 antagonist and formulation/use protection	Competing long-duration antiemetic platform
Dexamethasone combinations	Method and combination-use protection	Potentially overlapping clinical treatment but not the same active ingredient

The older metoclopramide regimen patent had a weaker long-term exclusion profile than a patent estate built around a novel chemical entity. Once compound protection expired, competitors could use the same active ingredient, subject to any remaining formulation, combination, or method claims.

Does biosimilar risk apply to metoclopramide?

No. Metoclopramide is a conventional small-molecule drug, not a biologic. Biosimilar pathways under the Biologics Price Competition and Innovation Act do not apply.[5]

Competitive entry occurs through abbreviated new drug applications for generic products, not biosimilar applications. The relevant patent issues are small-molecule patent certifications, labeling carve-outs, formulation claims, and method-of-use claims.

What geographic coverage does the patent provide?

US 4,536,386 provides US patent rights only. It does not directly restrict:

Treatment performed outside the United States.
Manufacture outside the United States, unless a separate US process or importation claim applies.
Foreign sales.
Foreign clinical use.
Foreign formulation or manufacturing activity.

Foreign equivalents, if any existed, would need separate country-by-country review. Their terms and status would not be inferred from the US patent. The US patent itself provides no current geographic barrier because it expired nationwide.

What is the current commercial exposure?

The direct revenue exposure from US 4,536,386 is zero as a patent matter. The patent cannot prevent generic metoclopramide supply or use of the cisplatin antiemetic regimen.

Commercial exposure instead depends on:

Generic metoclopramide pricing.
Availability of injectable products.
Hospital chemotherapy protocols.
FDA safety restrictions.
Use of newer antiemetics such as 5-HT3 antagonists, NK1 antagonists, and corticosteroid combinations.
Reimbursement and formulary placement.
Clinical preference for multidrug antiemetic prophylaxis.

The patent did not create a continuing royalty stream after expiration unless separate contractual rights exist.

What generic launch scenarios exist?

A current generic manufacturer could generally pursue the following scenarios without infringing US 4,536,386:

Oral metoclopramide for an approved indication.
Injectable metoclopramide in a liquid carrier.
A cisplatin antiemetic regimen outside the claimed dose or timing parameters.
A regimen using a different antiemetic class.
A combination regimen containing metoclopramide and another antiemetic.
A product with a label that omits any separately patented method, if such a patent existed.

Because this patent is expired, even a generic regimen that exactly reproduced the claimed protocol would not infringe a live US patent.

What manufacturing and intellectual-property barriers remain?

US 4,536,386 imposes no current manufacturing barrier. It does not claim:

Synthesis of metoclopramide.
Preparation of the monohydrochloride monohydrate salt.
Sterile manufacturing.
A particular liquid carrier.
A specific vial, syringe, infusion bag, or pump.
A controlled-release technology.
A combination product.

Potential non-patent barriers remain. These include FDA manufacturing requirements, sterile-processing controls, drug-shortage conditions, supplier qualification, pharmacovigilance, and the safety profile of high-dose or prolonged metoclopramide use.

Key Takeaways

US Patent 4,536,386 covered a high-dose metoclopramide regimen for cisplatin-induced emesis.
Claim 1 required approximately 5 to 18 mg/kg, beginning about 30 minutes before cisplatin and continuing through the post-treatment period.
The patent covered either continuous administration or 4 to 7 doses spaced approximately 1.5 to 3 hours apart.
Claims 2 through 7 narrowed the invention to IV administration, intermittent dosing, cisplatin-dose-specific regimens, the monohydrochloride monohydrate salt, and continuous infusion.
The patent issued August 20, 1985, and ordinarily expired August 20, 2002.
It is not a current Orange Book, Paragraph IV, generic-entry, or biosimilar barrier.
The patent claimed a treatment protocol, not the metoclopramide molecule, a novel formulation, or a manufacturing method.
Current competition is driven by generic metoclopramide and newer antiemetic classes rather than by this patent.

FAQs

Could a hospital use the exact patented metoclopramide regimen today?

Yes. The patent expired in 2002, so US Patent 4,536,386 does not prohibit use of the claimed regimen today.

Did US 4,536,386 cover cisplatin itself?

No. The patent used cisplatin as part of the treatment context and dose limitation. It did not claim cisplatin as a compound or protect cisplatin manufacturing.

Could claim 6 block generic metoclopramide hydrochloride products?

No. Claim 6 was limited to the monohydrochloride monohydrate salt and expired with the patent. It also did not create current compound or formulation exclusivity.

Is high-dose metoclopramide use for chemotherapy-induced emesis currently FDA-approved?

The FDA-approved status depends on the specific product, labeling, dosage, and indication. The historical patent does not establish FDA approval. Current metoclopramide labeling includes major safety restrictions, including the boxed warning for tardive dyskinesia.[4]

Could a foreign company be liable under this US patent for treating patients overseas?

No, not based solely on US Patent 4,536,386. US patent rights generally do not extend to conduct occurring entirely outside the United States, and this patent is expired in any event.

References

United States Patent and Trademark Office. (1985). US Patent No. 4,536,386, Method for alleviating emesis in human cancer patients caused by cisplatin chemotherapy.
United States Code, 35 U.S.C. §§ 154, 156, and 271.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2024). Reglan (metoclopramide hydrochloride) prescribing information.
United States Code, Public Law 111-148, § 7002, 124 Stat. 119, 804-821 (2010).

Details for Patent: 4,536,386

Summary for Patent: 4,536,386