ISMO Drug Patent Profile

Which patents cover Ismo, and what generic alternatives are available?

Ismo is a drug marketed by Promius Pharma and Alcon and is included in two NDAs.

The generic ingredient in ISMO is isosorbide. There are two drug master file entries for this compound. Additional details are available on the isosorbide profile page.

Summary for ISMO

US Patents:	0
Applicants:	2
NDAs:	2
Raw Ingredient (Bulk) Api Vendors:	62
Patent Applications:	4,704
DailyMed Link:	ISMO at DailyMed

US Patents and Regulatory Information for ISMO

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Promius Pharma	ISMO	isosorbide mononitrate	TABLET;ORAL	019091-001	Dec 30, 1991		DISCN	No	No
Alcon	ISMOTIC	isosorbide	SOLUTION;ORAL	017063-001	Approved Prior to Jan 1, 1982		DISCN	No	No

ISMO Market Dynamics, Patent Status, and Financial Trajectory

Last updated: September 6, 2026

ISMO is the former U.S. brand for immediate-release isosorbide mononitrate, an organic nitrate used to prevent angina. Its commercial trajectory is mature and largely complete: U.S. brand marketing has ended, generic isosorbide mononitrate remains available in limited channels, and no meaningful branded patent or regulatory exclusivity appears to protect the product today. Public sources do not disclose standalone ISMO revenue, so its financial history must be assessed through product status, generic substitution, clinical demand, and channel economics rather than reported brand sales.

What is ISMO and how is it used?

ISMO contains isosorbide mononitrate, the active metabolite of isosorbide dinitrate. It produces nitric-oxide-mediated vasodilation and is used primarily for the prevention of angina pectoris associated with coronary artery disease. It is not intended to terminate an acute angina attack because its onset and dosing profile are not appropriate for rapid rescue treatment.

ISMO was an immediate-release oral tablet product. The broader isosorbide mononitrate market also includes extended-release products, particularly Imdur and generic extended-release formulations. Those products compete with immediate-release ISMO but are not direct substitutes in every prescribing situation because dosing frequency and release characteristics differ.

Product	Active ingredient	Release profile	Primary use	Commercial status
ISMO	Isosorbide mononitrate	Immediate release	Angina prevention	Former U.S. brand
Imdur	Isosorbide mononitrate	Extended release	Angina prevention	Brand and generic competition
Generic isosorbide mononitrate	Isosorbide mononitrate	Immediate or extended release	Angina prevention	Available from multiple manufacturers
Isosorbide dinitrate products	Isosorbide dinitrate	Immediate or extended release	Angina and heart failure regimens	Separate competitive class

FDA labeling for isosorbide mononitrate identifies headache, dizziness, and hypotension as important adverse effects. Continuous nitrate exposure can cause tolerance, so dosing schedules generally incorporate a nitrate-free interval. These clinical limitations restrict chronic use in some patients and reduce the likelihood of premium pricing for the molecule. (U.S. Food and Drug Administration, n.d.-a)

What is the FDA regulatory status of ISMO?

The FDA-approved ISMO product was an older small-molecule prescription drug, not a biologic. Its regulatory protection was based on an original new drug application rather than a modern specialty-drug framework.

The product’s commercial status is best characterized as discontinued or no longer actively marketed in the U.S. The FDA’s discontinued-drug databases distinguish products withdrawn for commercial reasons from products withdrawn for safety or efficacy reasons. A discontinued listing does not, by itself, indicate a safety withdrawal. (U.S. Food and Drug Administration, n.d.-b)

The regulatory record has several implications:

• ISMO has no current new-molecular-entity exclusivity.
• Any original pediatric, orphan, or other regulatory exclusivity would have expired long ago.
• Generic applicants could use the abbreviated new drug application pathway if the reference product and applicable dosage form were eligible.
• Current prescriptions are generally fulfilled through generic isosorbide mononitrate products rather than a continuing ISMO brand franchise.

What patents protect ISMO?

No commercially relevant, unexpired U.S. patent estate is apparent for the original ISMO immediate-release product. The active ingredient is an old nitrate compound, and the principal market protection associated with branded isosorbide mononitrate products expired decades ago or no longer has practical commercial effect.

Patent categories relevant to ISMO

Patent category	Relevance to ISMO	Current commercial impact
Active-ingredient patent	Isosorbide mononitrate is an established small molecule	No meaningful current protection
Original formulation patent	May have covered tablet composition or dosage form	Expired or commercially obsolete
Method-of-use patent	Angina prevention and related cardiovascular uses are longstanding indications	No meaningful exclusivity
Manufacturing patent	Could cover process conditions or intermediates	Unlikely to block routine generic supply
Device patent	Not relevant to conventional ISMO tablets	None
Biologic patent	Not applicable	None

The principal patent risk is therefore not infringement of a live ISMO patent. It is ordinary generic competition, including price erosion, product discontinuation by low-volume manufacturers, and pharmacy-level substitution.

The Orange Book remains the relevant FDA source for listed patents and exclusivity associated with approved drug products. For a discontinued legacy brand, the absence of an active listing or the expiration of listed patents removes the principal U.S. barrier to generic entry. (U.S. Food and Drug Administration, n.d.-c)

When did ISMO lose exclusivity?

ISMO lost practical exclusivity after the emergence of generic isosorbide mononitrate products and the expiration of any original patent or regulatory protection. The exact timing of the first generic launch is less important to current economics than the fact that the product has been exposed to generic competition for many years.

ISMO exclusivity timeline

Period	Market event	Financial effect
Initial launch period	Branded ISMO supplied immediate-release isosorbide mononitrate	Brand pricing and physician recognition
Early maturity	Generic immediate-release products entered the market	Prescription substitution and price pressure
Late maturity	Branded ISMO marketing declined or ended	Loss of brand revenue
Current market	Generic products supply the remaining demand	Low unit prices and limited manufacturer margins

There is no current basis for treating ISMO as a protected product with a future patent cliff. The relevant commercial event already occurred: the market transitioned from branded supply to generic supply.

How many patents cover ISMO today?

The practical answer is zero commercially meaningful active U.S. patents for the original ISMO product.

That assessment does not mean that no patent anywhere in the world has ever mentioned isosorbide mononitrate. A patent search could identify patents covering later formulations, manufacturing processes, combinations, or unrelated delivery technologies. Those documents do not automatically protect ISMO or block ordinary generic immediate-release tablets.

The product’s low patent strength results from four factors:

1. The active ingredient is old and well characterized.
2. Angina prevention is an established use.
3. The product is a conventional oral tablet.
4. Generic manufacturers can rely on established pharmaceutical manufacturing processes.

What is the Orange Book status of ISMO?

ISMO’s Orange Book relevance is historical rather than defensive. The Orange Book records approved drug products, therapeutic equivalence information, patents, and exclusivity. If the original ISMO product is discontinued, the active commercial reference product may no longer provide a current branded platform for market growth, even though generic products remain approved or have historically relied on the reference product.

The economic importance of Orange Book status is limited in this case:

• There is no current branded launch protected by a paragraph IV settlement.
• No major patent litigation campaign is associated with ISMO.
• Generic competition is not waiting for a future Orange Book patent expiration.
• Any remaining legal disputes would likely involve product approval, manufacturing, labeling, or supply issues rather than core composition-of-matter protection.

Are there Paragraph IV challenges to ISMO?

Paragraph IV litigation is not a material current issue for ISMO. Paragraph IV certifications challenge listed patents as invalid, unenforceable, or not infringed. That mechanism is most commercially relevant when a branded product has meaningful remaining sales and active listed patents.

For a discontinued, legacy nitrate brand, the commercial incentive to pursue a high-value Paragraph IV launch is minimal. Generic isosorbide mononitrate products entered a market where the core patent barriers had already ceased to protect premium revenue. No notable current Paragraph IV campaign or settlement agreement is associated with the former ISMO brand in the public regulatory record.

What formulation patents protect isosorbide mononitrate products?

Formulation protection is more relevant to extended-release products than to immediate-release ISMO.

Immediate-release tablets

Immediate-release isosorbide mononitrate tablets are technically straightforward. Potential formulation claims could address excipients, compression parameters, stability, dissolution, or manufacturing methods. These claims generally have limited blocking power when multiple generic formulations can achieve the same release profile.

Extended-release tablets

Extended-release products have greater formulation complexity. Potential patent areas include:

• Matrix systems controlling dissolution.
• Coatings that regulate drug release.
• Once-daily dosing profiles.
• Bioavailability and pharmacokinetic performance.
• Manufacturing methods that produce consistent release.

These issues may affect generic substitution between immediate-release and extended-release products, but they do not restore exclusivity to the former ISMO brand. Generic extended-release competition is relevant mainly to branded products such as Imdur and to the overall nitrate market.

What generic entry risks exist for ISMO?

Generic entry risk is no longer a future event. It is the central condition of the market.

Price erosion

Generic isosorbide mononitrate is a low-cost, multisource product. Once several suppliers are approved, pharmacy benefit managers and wholesalers can shift volume toward the lowest-cost manufacturers. Unit prices tend to fall, although shortage conditions can temporarily produce price increases.

Supply concentration

Low demand can cause manufacturers to exit. That produces a counterintuitive risk: a market with weak pricing may still experience supply disruption if only a small number of manufacturers remain willing to produce the product.

Limited differentiation

ISMO has little defensible differentiation from generic immediate-release isosorbide mononitrate. Tablet strength, supplier reliability, packaging, and reimbursement access matter more than clinical brand equity.

Therapeutic substitution

Prescribers can choose other nitrate products or non-nitrate antianginal therapies depending on the patient’s cardiovascular profile. Long-term treatment patterns also reflect the wider use of revascularization, beta blockers, calcium-channel blockers, ranolazine, and guideline-directed coronary disease management.

What is the competitive landscape for ISMO?

ISMO competes in a mature cardiovascular market with multiple therapeutic alternatives. Its direct competitors are generic immediate-release isosorbide mononitrate products. Its broader competitors include extended-release isosorbide mononitrate, isosorbide dinitrate, and non-nitrate antianginal medicines.

Competitive segment	Competitive strength against ISMO	Reason
Generic immediate-release isosorbide mononitrate	High	Same active ingredient and dosage form
Generic extended-release isosorbide mononitrate	Moderate	Different dosing profile
Imdur brand	Moderate	Brand recognition and extended-release positioning
Isosorbide dinitrate	Moderate	Related nitrate with distinct dosing and uses
Beta blockers	High in selected patients	Broad cardiovascular indications
Calcium-channel blockers	High in selected patients	Alternative antianginal mechanism
Ranolazine	Moderate	Non-nitrate option for chronic angina

The product has no meaningful competitive moat based on clinical novelty, delivery technology, or intellectual property.

What is the financial trajectory of ISMO?

ISMO’s standalone revenue is not publicly reported by its former commercial sponsor. The financial trajectory can nevertheless be inferred with reasonable confidence:

1. Revenue rose during the branded launch and adoption phase.
2. Sales declined after generic immediate-release products entered.
3. Brand revenue approached immaterial levels as formularies substituted generic products.
4. U.S. brand marketing ended or became commercially inactive.
5. Remaining economic activity shifted to generic manufacturers, wholesalers, and pharmacies.

The former brand’s financial profile is therefore a declining tail rather than a growth asset. Any residual revenue would likely come from isolated legacy prescriptions, non-U.S. markets, inventory liquidation, or niche distribution arrangements. Those sources do not support a durable premium franchise.

Revenue exposure by stakeholder

Stakeholder	Current ISMO exposure
Former brand owner	Minimal or none from active U.S. brand sales
Generic manufacturers	Low-value volume opportunity
Wholesalers	Commodity distribution revenue
Pharmacies	Low reimbursement spread, subject to payer contracts
Payers	Low per-prescription drug cost
Investors	No clear standalone branded revenue catalyst

Public company filings from the former sponsor do not provide a separately reported ISMO revenue line. As a result, the product should not be modeled as a material contributor to corporate sales without transaction-specific evidence.

Does ISMO have biosimilar risk?

No. ISMO is a chemically synthesized small molecule, not a biologic. Biosimilar regulation does not apply. The relevant competitive pathway is generic substitution through abbreviated new drug applications, not biosimilar development under the Public Health Service Act.

This distinction matters because biosimilar products often face manufacturing complexity, interchangeability standards, and substantial development costs. ISMO does not face those barriers. Generic manufacturers can compete through conventional pharmaceutical development and manufacturing.

What manufacturing and intellectual-property barriers remain?

Manufacturing barriers are low but not zero. Producers must maintain control over assay, impurities, content uniformity, dissolution, stability, and tablet production. Isosorbide mononitrate is moisture-sensitive enough that packaging and stability management can matter operationally, but these requirements do not create a durable patent barrier.

The main residual barriers are commercial:

• FDA compliance and manufacturing-site qualification.
• Reliable active pharmaceutical ingredient supply.
• Low margins at generic prices.
• Small or declining prescription volume.
• Wholesaler and pharmacy contracting.
• Potential shortages if suppliers withdraw.

These factors may limit the number of active suppliers, but they do not support premium pricing comparable with patented cardiovascular products.

What geographic markets still use ISMO?

The ISMO name has had greater historical recognition in certain international markets, but regulatory status and commercial availability differ by country. A U.S. discontinuation does not establish worldwide withdrawal. Some jurisdictions may continue to market isosorbide mononitrate under local brands or generic names, including immediate-release and modified-release products.

Geographic value is constrained by the age of the molecule and the availability of local generic suppliers. International rights, if any remain, would be country-specific and would require confirmation through national registers and local commercial records. The U.S. patent and regulatory position does not create a global exclusivity right.

What litigation and settlement agreements affect ISMO?

No major current patent litigation or settlement agreement materially affects the former ISMO brand. The absence of litigation is consistent with the product’s low commercial value, expired protection, and genericized market structure.

Potential legal exposure would be more likely to arise from:

• Product liability claims.
• Manufacturing-quality enforcement.
• Labeling disputes.
• Generic approval or therapeutic-equivalence issues.
• Supply or distribution contracts.

Those issues are distinct from a branded patent dispute and do not create a credible near-term revenue catalyst.

How strong is the ISMO patent estate compared with newer cardiovascular drugs?

ISMO has a weak patent estate compared with newer cardiovascular products. A modern cardiovascular drug may have composition-of-matter protection, polymorph patents, formulation claims, method-of-use claims, and pediatric or regulatory exclusivity. ISMO has none of those protections with meaningful remaining commercial duration.

Factor	ISMO	Newer protected cardiovascular drug
Active ingredient protection	None of practical value	Often substantial
Formulation protection	Limited or expired	May be active
Method-of-use protection	Expired or weak	May be active
Regulatory exclusivity	Expired	Possible
Generic entry risk	Already realized	Future risk
Pricing power	Very low	Potentially high
Litigation value	Low	Potentially high

Key Takeaways

• ISMO is the former U.S. brand for immediate-release isosorbide mononitrate.
• The U.S. brand is commercially inactive or discontinued, while generic isosorbide mononitrate remains available.
• No commercially meaningful active patent estate protects the original ISMO product.
• Paragraph IV litigation and patent settlements are not material current issues.
• ISMO has no biosimilar exposure because it is a small-molecule drug.
• Revenue is not separately disclosed and should be modeled as immaterial brand revenue.
• The remaining market is a low-price generic business exposed to supplier consolidation and intermittent availability risks.
• Extended-release formulations have greater technical complexity, but their patent position does not revive the former ISMO franchise.
• The product has no evident commercial catalyst other than temporary supply disruption or localized demand.

FAQs About ISMO Market and Exclusivity

Is ISMO still sold in the United States?

The former branded ISMO product is not a meaningful active U.S. commercial franchise. Patients may receive generic immediate-release isosorbide mononitrate instead.

Is ISMO the same as Imdur?

Both contain isosorbide mononitrate, but ISMO was an immediate-release product and Imdur is associated with extended-release delivery. They are not automatically interchangeable on a dose-for-dose or schedule-for-schedule basis.

Can a generic manufacturer launch ISMO today?

A manufacturer can develop and market an approved generic isosorbide mononitrate product if it satisfies FDA requirements. It cannot market the product using the ISMO trademark without the relevant trademark rights.

Does ISMO have a patent expiration date investors should monitor?

No single future patent expiration appears to create a material ISMO market event. The key patent expirations and generic entry events occurred historically.

Could ISMO revenue recover if generic suppliers exit?

A supply shortage could raise short-term prices for available generic inventory, but it would not recreate durable brand exclusivity. Any recovery would likely be temporary and dependent on manufacturing availability.

References

1. U.S. Food and Drug Administration. (n.d.-a). Isosorbide mononitrate prescribing information. FDA.
2. U.S. Food and Drug Administration. (n.d.-b). FDA-approved drug products and discontinued drug products databases. FDA.
3. U.S. Food and Drug Administration. (n.d.-c). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. FDA.
4. DailyMed. (n.d.). Isosorbide mononitrate tablet labeling. National Library of Medicine.
5. U.S. Food and Drug Administration. (n.d.-d). Abbreviated new drug application process for generic drugs. FDA.