NORPACE CR Drug Patent Profile

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Which patents cover Norpace Cr, and when can generic versions of Norpace Cr launch?

Norpace Cr is a drug marketed by Pfizer and is included in one NDA.

The generic ingredient in NORPACE CR is disopyramide phosphate. There is one drug master file entry for this compound. Four suppliers are listed for this compound. Additional details are available on the disopyramide phosphate profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Norpace Cr

A generic version of NORPACE CR was approved as disopyramide phosphate by TEVA on February 22^nd, 1985.

Summary for NORPACE CR

US Patents:	0
Applicants:	1
NDAs:	1
Raw Ingredient (Bulk) Api Vendors:	47
Clinical Trials:	1
Patent Applications:	1,384
Drug Prices:	Drug price information for NORPACE CR
DailyMed Link:	NORPACE CR at DailyMed

See drug prices for NORPACE CR

Recent Clinical Trials for NORPACE CR

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
Mayo Clinic	Phase 3
Medtronic	Phase 3

See all NORPACE CR clinical trials

US Patents and Regulatory Information for NORPACE CR

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Pfizer	NORPACE CR	disopyramide phosphate	CAPSULE, EXTENDED RELEASE;ORAL	018655-001	Jul 20, 1982		DISCN	Yes	No
Pfizer	NORPACE CR	disopyramide phosphate	CAPSULE, EXTENDED RELEASE;ORAL	018655-002	Jul 20, 1982		DISCN	Yes	No

Norpace CR Market Dynamics, Patent Status, and Financial Trajectory

Last updated: October 6, 2026

Norpace CR is the extended-release formulation of disopyramide phosphate, a Class Ia antiarrhythmic used primarily in selected patients with ventricular arrhythmias and obstructive hypertrophic cardiomyopathy. Its commercial position is niche, generic competition is established, and no material standalone financial disclosure is publicly available. The drug’s value is driven more by clinical scarcity in specialized cardiology than by brand pricing power.

What is Norpace CR and how is it used?

Norpace CR contains disopyramide phosphate in an extended-release oral capsule. Disopyramide blocks fast sodium channels and has anticholinergic effects. The immediate-release and extended-release formulations are pharmacologically related, but Norpace CR reduces dosing frequency compared with conventional capsules.

The U.S. label identifies disopyramide for documented life-threatening ventricular arrhythmias, such as sustained ventricular tachycardia, when less toxic alternatives are ineffective or not tolerated. Disopyramide is also used off-label by specialist physicians for symptomatic obstructive hypertrophic cardiomyopathy because its negative inotropic activity can reduce left ventricular outflow tract obstruction.[1]

Key product characteristics

Attribute	Norpace CR
Active ingredient	Disopyramide phosphate
Drug class	Class Ia antiarrhythmic
Dosage form	Extended-release capsule
U.S. strengths	100 mg and 150 mg
Primary historical sponsor	Searle, later associated with Pfizer
U.S. regulatory status	Approved prescription drug; generic disopyramide ER products are available
Main clinical niches	Ventricular arrhythmias; specialist treatment of obstructive hypertrophic cardiomyopathy
Main safety restrictions	Proarrhythmia, QT prolongation, heart failure, anticholinergic effects, hypoglycemia
Competitive substitutes	Amiodarone, sotalol, mexiletine, quinidine, beta blockers, verapamil, mavacamten, septal reduction procedures

The product carries a boxed warning concerning use in life-threatening arrhythmias and requires careful patient selection. It can worsen heart failure because of negative inotropic effects and can cause urinary retention, glaucoma-related complications, dry mouth, constipation and hypoglycemia.[1]

When does Norpace CR lose exclusivity?

Norpace CR has no meaningful remaining U.S. market exclusivity based on the original brand approval. Disopyramide has been marketed in the United States for decades, and generic versions have entered the market.

The original Norpace approval dates to the 1970s, while the controlled-release formulation was approved later. Any patent protection associated with the original product or early formulation would have expired long ago under modern patent-term rules. The relevant commercial question is therefore not the original patent expiration date, but whether any current formulation, manufacturing or labeling patent creates a barrier to generic competition.

Public FDA records do not indicate a current patent estate that provides Norpace CR with meaningful exclusivity against approved generic disopyramide extended-release capsules.[2]

Exclusivity timeline

Period	Event	Commercial effect
1970s	Initial U.S. approval of disopyramide products	Established the active ingredient market
1980s	Approval of controlled-release Norpace CR formulation	Added extended-release dosing option
1990s-2000s	Generic development and market entry	Reduced brand pricing power
Current market	Generic disopyramide products available	Brand competes in a mature, low-growth market

What patents protect Norpace CR?

Norpace CR is not protected by a commercially significant active patent estate in the United States. The key intellectual-property protection historically related to the product’s extended-release dosage form, but those protections are no longer capable of supporting branded exclusivity.

Patent categories relevant to Norpace CR

Patent category	Current strategic relevance
Active-ingredient patents	None expected; disopyramide is an old small molecule
Original formulation patents	Expired
Extended-release capsule patents	Expired or commercially ineffective
Method-of-use patents	No material current Orange Book barrier identified
Manufacturing patents	Potentially confidential and process-specific, but not a practical branded barrier
Regulatory exclusivity	None of commercial significance for the legacy product

Norpace CR’s competitive position therefore depends on manufacturing reliability, wholesaler supply, prescriber familiarity and reimbursement rather than enforceable exclusivity.

What is the Orange Book status of Norpace CR?

The FDA Orange Book historically listed Norpace and Norpace CR as reference products for disopyramide formulations. The presence of an approved reference listed drug does not mean the brand retains market exclusivity. Generic applicants can rely on an abbreviated new drug application if they demonstrate bioequivalence and meet the applicable formulation and labeling requirements.[2][3]

The commercial status of the branded product should be separated from the regulatory status of the active ingredient:

• Norpace CR can remain a reference product even when patent protection has expired.
• Generic disopyramide extended-release capsules may be approved without infringing an unexpired Orange Book-listed patent.
• A brand product may have limited or intermittent distribution even while the FDA reference listing remains relevant.
• FDA discontinuation records do not necessarily establish withdrawal for safety or efficacy reasons. They can reflect commercial discontinuation.[2]

How many patents cover Norpace CR?

No material number of unexpired U.S. Orange Book patents is publicly associated with Norpace CR based on the legacy nature of the product and the availability of generic extended-release disopyramide.

The practical answer for market analysis is zero currently meaningful brand-blocking patents. That conclusion differs from saying that no historical patents ever covered the product. Historical formulation or delivery patents may have existed, but their terms have ended.

Which companies compete with Norpace CR?

Competition comes from both generic disopyramide manufacturers and clinically substitutable therapies.

Direct generic competition

Generic disopyramide products may be supplied by manufacturers including established generic companies, depending on current FDA approval and commercial distribution. Product availability can vary because the market is small, manufacturing capacity is limited and demand is concentrated among specialists.

The relevant generic risks are:

1. Lower pricing than the branded product.
2. Pharmacy substitution under state substitution rules.
3. Contracting pressure from wholesalers and group purchasing organizations.
4. Periodic shortages if only a small number of suppliers remain active.
5. Lower physician attachment to the brand where the generic has acceptable supply.

Therapeutic competition

Therapy	Competitive role
Amiodarone	Broad antiarrhythmic efficacy, but substantial long-term toxicity
Sotalol	Rhythm-control alternative with QT and renal limitations
Mexiletine	Oral sodium-channel blocker used in selected ventricular arrhythmia cases
Quinidine	Alternative Class Ia therapy with limited routine use
Beta blockers	Common treatment for hypertrophic cardiomyopathy and arrhythmia control
Verapamil	Selected obstructive hypertrophic cardiomyopathy patients
Mavacamten	Disease-directed option for symptomatic obstructive hypertrophic cardiomyopathy
Septal myectomy or alcohol septal ablation	Procedural treatment for selected obstructive hypertrophic cardiomyopathy patients

Disopyramide remains differentiated in obstructive hypertrophic cardiomyopathy because its negative inotropic effect can reduce obstruction. That niche is narrower than the overall antiarrhythmic market.

What is the financial trajectory for Norpace CR?

Standalone Norpace CR revenue is not publicly reported in Pfizer’s financial statements or in other widely available issuer-level disclosures. Pfizer reports revenue by broader product, business unit or geographic category rather than by every mature legacy medicine.[4]

The financial trajectory is best characterized as:

1. Historical decline after generic entry.
2. Low current revenue contribution relative to Pfizer’s major brands.
3. Limited opportunity for premium pricing.
4. Potential episodic revenue support during generic shortages.
5. Continued erosion from generic substitution and therapeutic alternatives.

Financial profile

Financial factor	Assessment
Revenue growth	Low or negative under normal generic-market conditions
Price power	Weak
Gross-margin potential	Constrained by generic competition and small volume
Market size	Niche
Brand contribution to Pfizer	Immaterial relative to major Pfizer products
Shortage upside	Possible but temporary
Litigation value	Low
Licensing value	Limited unless tied to a specialty-cardiology portfolio
Commercial durability	Dependent on supply and specialist demand

Norpace CR is unlikely to be a meaningful driver of Pfizer’s consolidated financial results. A private-label or generic supplier could obtain better economics if it controls one of few reliable sources, but that would reflect supply concentration rather than patent protection.

What generic entry risks exist for Norpace CR?

Generic entry risk is already realized rather than prospective. The main risk is ongoing substitution by approved generic disopyramide products.

Generic launch scenarios

Scenario	Market impact
Multiple generic suppliers	Sustained price erosion and low brand share
One or two active suppliers	Brand and generic prices may remain elevated; shortage risk increases
Generic discontinuation	Temporary brand demand recovery or supply gap
New generic entrant	Further price compression and reduced distributor leverage
Formulation supply problem	Clinical disruption because switching antiarrhythmics requires physician oversight

The most important barrier is not patent law. It is pharmaceutical quality and supply continuity. Disopyramide is a low-volume product, so manufacturers may have limited incentives to maintain redundant production.

What formulation and manufacturing barriers affect Norpace CR?

Extended-release disopyramide requires control of release kinetics and bioequivalence. Generic manufacturers must demonstrate that the formulation produces an acceptable pharmacokinetic profile relative to the reference product.

Potential technical barriers include:

• Extended-release matrix or coating performance.
• Dose proportionality across 100 mg and 150 mg strengths.
• Dissolution testing under multiple conditions.
• Stability over the labeled shelf life.
• Control of dose dumping.
• Consistent active pharmaceutical ingredient supply.
• Manufacturing economics at low annual volume.

These barriers can slow entry or create supply interruptions, but they do not create durable exclusivity after approval.

What is the FDA regulatory status of Norpace CR?

Norpace CR is an FDA-approved prescription drug. Its regulatory risk profile is higher than that of many mature oral medicines because disopyramide can cause life-threatening arrhythmias and worsen heart failure.

FDA labeling requires attention to:

• QT prolongation and torsades de pointes.
• Renal impairment and dose adjustment.
• Heart failure or reduced ventricular function.
• Anticholinergic contraindications.
• Hypoglycemia.
• Drug interactions that increase arrhythmia risk.
• Monitoring during initiation or dose changes in higher-risk patients.[1]

The regulatory environment does not currently create a clear path to major label expansion. The product’s clinical role is constrained by safety, specialist prescribing and the availability of alternative treatments.

Which companies are challenging Norpace CR?

Generic manufacturers have already challenged the commercial position of Norpace CR through abbreviated approval pathways rather than high-profile patent litigation. No major active Paragraph IV litigation involving a blocking Norpace CR patent is broadly evident in the public record.

Paragraph IV and litigation assessment

Issue	Current assessment
Paragraph IV challenge	Historically possible and commercially relevant during generic entry
Active patent litigation	No material current dispute identified
Settlement agreements	No major publicly reported settlement central to current market access
Litigation exposure	Low
Regulatory challenge	More relevant through approval, labeling and supply compliance than patent litigation

The absence of active litigation is consistent with the product’s age and lack of commercially significant unexpired patent claims.

How strong is the Norpace CR patent estate?

The patent estate is weak from a present-day commercial perspective. The product lacks the characteristics that support a high-value branded patent position:

• The molecule is old.
• Generic products are available.
• The extended-release concept is mature.
• The principal clinical use is narrow.
• No current patent barrier is known to delay generic competition.
• No major new formulation or delivery platform is associated with the product.

Norpace CR could still have operational value in a specialty portfolio if a supplier can guarantee availability. That value would come from distribution and supply execution, not intellectual-property protection.

How does Norpace CR compare with newer hypertrophic cardiomyopathy therapies?

Mavacamten has a stronger growth profile and a more differentiated regulatory position in obstructive hypertrophic cardiomyopathy. It targets cardiac myosin and is approved for adults with symptomatic New York Heart Association class II-III obstructive disease to improve functional capacity and symptoms.[5]

Factor	Norpace CR	Mavacamten
Age of product	Legacy	Newer
Patent position	Weak or expired	Active patent and regulatory exclusivity framework
Pricing	Generic or low branded pricing	Specialty branded pricing
Clinical use	Narrow specialist use	Disease-directed treatment
Monitoring	Arrhythmia, renal and anticholinergic risks	Echocardiographic monitoring and drug-interaction controls
Revenue outlook	Mature or declining	Growth-oriented, subject to access and safety controls

Norpace CR retains a role where clinicians need negative inotropy and where cost or access favors an older oral therapy. Mavacamten limits long-term growth in the same disease segment.

Key Takeaways

• Norpace CR is an extended-release disopyramide product for a narrow antiarrhythmic and obstructive hypertrophic cardiomyopathy market.
• Generic competition is established, and the original patent estate no longer provides meaningful commercial exclusivity.
• The current U.S. market is driven by supply reliability, specialist prescribing and pharmacy distribution.
• Pfizer does not publicly disclose standalone Norpace CR revenue.
• The product is unlikely to have material impact on Pfizer’s consolidated financial performance.
• Generic entry risk is already realized; future risk comes from additional suppliers and price erosion.
• Supply interruption is a more important commercial risk than patent litigation.
• Mavacamten and procedural treatment reduce the long-term growth potential of disopyramide in obstructive hypertrophic cardiomyopathy.
• Norpace CR’s remaining economic value is primarily operational and clinical, not patent-based.

FAQs

Is Norpace CR still available in the United States?

Norpace CR and generic extended-release disopyramide availability can vary by manufacturer, pharmacy and wholesaler inventory. FDA reference-product status and commercial distribution are separate issues.

Is disopyramide ER the same as Norpace CR?

Disopyramide extended-release capsules are intended to provide the same active ingredient and extended-release dosage form as Norpace CR, subject to FDA approval and bioequivalence requirements.

Does Norpace CR have orphan-drug exclusivity?

Norpace CR is a legacy product and is not generally associated with current orphan-drug exclusivity that would block generic competition.

Can Norpace CR be substituted automatically with immediate-release disopyramide?

Not necessarily. The extended-release and immediate-release products have different dosing schedules and pharmacokinetic profiles. Substitution should follow the applicable prescription, state pharmacy rules and clinician direction.

Is Norpace CR commercially attractive for a generic manufacturer?

It can be attractive when supply is concentrated and manufacturing is reliable, but the market is small. The opportunity depends on volume, reimbursement, shortage conditions and production economics rather than patent exclusivity.

References

1. U.S. Food and Drug Administration. (2023). Norpace CR (disopyramide phosphate) extended-release capsules: Prescribing information.
2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, 44th edition.
3. U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs database.
4. Pfizer Inc. (2024). 2023 annual report.
5. U.S. Food and Drug Administration. (2022). Camzyos (mavacamten) prescribing information.