List of Excipients in Branded Drug PROPAFENONE

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Prasco Laboratories	PROPAFENONE HYDROCHLORIDE	propafenone hydrochloride	66993-114	FERRIC OXIDE RED
Prasco Laboratories	PROPAFENONE HYDROCHLORIDE	propafenone hydrochloride	66993-114	GELATIN
Prasco Laboratories	PROPAFENONE HYDROCHLORIDE	propafenone hydrochloride	66993-114	HYPROMELLOSE
Prasco Laboratories	PROPAFENONE HYDROCHLORIDE	propafenone hydrochloride	66993-114	LECITHIN, SOYBEAN

Generic Drugs Containing PROPAFENONE

Company	Ingredient	NDC	Excipient
Rebel Distributors Corp	propafenone hydrochloride	21695-814	ALCOHOL
Rebel Distributors Corp	propafenone hydrochloride	21695-814	ANHYDROUS LACTOSE
Rebel Distributors Corp	propafenone hydrochloride	21695-814	BUTYL ALCOHOL
Rebel Distributors Corp	propafenone hydrochloride	21695-814	D&C YELLOW NO. 10

What are the Most Frequently-Used Excipients in PROPAFENONE?

# Of NDCs	Excipient
1	ALCOHOL
1	ANHYDROUS LACTOSE
1	BUTYL ALCOHOL
1	D&C YELLOW NO. 10

Propafenone Excipient Strategy and Commercial Opportunities

Last updated: August 9, 2026

Propafenone is a mature Class IC antiarrhythmic with broad generic availability, limited current patent protection, and differentiated commercial opportunities concentrated in modified release, patient-friendly dosage forms, and excipient-controlled products. The main technical constraint is pharmacokinetic variability caused by extensive first-pass metabolism and CYP2D6 polymorphism. Excipient selection must preserve dissolution performance, dose uniformity, and release control without creating avoidable bioequivalence risk.

What is the FDA regulatory status of propafenone?

Propafenone hydrochloride is approved in the United States as immediate-release tablets and extended-release capsules. The originator products are Rythmol and Rythmol SR, marketed by AbbVie predecessor companies and originally developed by Knoll Pharmaceuticals.

Product	Dosage form	Typical strengths	FDA role
Rythmol	Immediate-release tablet	150, 225, 300 mg	Atrial fibrillation/flutter and ventricular arrhythmia indications
Rythmol SR	Extended-release capsule	225, 325, 425 mg	Extended treatment of symptomatic paroxysmal atrial fibrillation/flutter
Generic propafenone HCl	Immediate-release tablet	150, 225, 300 mg	ANDA-based generic competition
Generic propafenone HCl ER	Extended-release capsule	225, 325, 425 mg	ANDA-based generic competition

The immediate-release product was approved in 1989, while Rythmol SR was approved later as a controlled-release product. The FDA labeling identifies propafenone as a sodium-channel blocker with beta-adrenergic blocking activity. It carries significant cardiovascular warnings, including proarrhythmic risk, worsening heart failure, conduction abnormalities, and clinically important drug interactions.[1][2]

Propafenone is not a biologic. Biosimilar competition is therefore irrelevant. Competitive entry occurs through abbreviated new drug applications, 505(b)(2) applications, authorized generics, pharmacy-compounded products, and potential differentiated delivery systems.

What patents protect propafenone products?

The core active-ingredient patent estate for propafenone is commercially exhausted in the United States. The principal opportunity is not basic molecule protection but formulation, delivery, manufacturing, and use-related intellectual property.

What is the Orange Book status of Rythmol and Rythmol SR?

The FDA Orange Book is the relevant source for listed patents and regulatory exclusivity. Current Orange Book entries should be reviewed by product and NDA because listed patent status can change through delisting, expiration, or administrative updates.[3]

For commercial planning, the important conclusions are:

• Propafenone hydrochloride is a mature generic active ingredient.
• The original Rythmol and Rythmol SR exclusivity periods have expired.
• Generic immediate-release and extended-release products compete in the U.S. market.
• Any new formulation relying on a 505(b)(2) pathway would need a distinct clinical, pharmacokinetic, delivery, or labeling rationale.
• A formulation patent cannot prevent ordinary generic entry unless the generic product falls within the asserted claims and the patent survives validity and infringement challenges.

What types of patents could protect a new propafenone product?

A new propafenone product could pursue claims covering:

1. Extended-release multiparticulate systems.
2. Specific dissolution profiles across acidic and neutral media.
3. Capsule-sprinkle or food-compatible administration.
4. Taste-masked liquid formulations.
5. Low-moisture or moisture-protective compositions.
6. Lactose-free, dye-free, or allergen-controlled formulations.
7. Manufacturing processes that improve content uniformity.
8. Combination products involving rhythm-control or rate-control agents.
9. Patient subgroups defined by CYP2D6 phenotype, renal function, or drug-interaction status.
10. Device-assisted dispensing for liquid or granulated products.

The strongest formulation claims would tie the excipient system to measurable performance, such as a reproducible release profile, improved stability, reduced food effect, or improved bioavailability. Claims limited to replacing one conventional filler with another are more vulnerable to obviousness challenges.

How does propafenone’s pharmacokinetics affect excipient selection?

Propafenone has high and variable first-pass metabolism. CYP2D6, CYP3A4, and CYP1A2 contribute to metabolism, and patients who are poor CYP2D6 metabolizers can have substantially higher exposure. The FDA label reports wide interindividual variability in plasma concentrations and cautions against coadministration with strong CYP2D6 and CYP3A4 inhibitors.[1]

This creates four excipient priorities:

Formulation objective	Excipient strategy	Commercial rationale
Control peak concentration	Hydrophilic matrix, coated pellets, or reservoir beads	May reduce peak-related tolerability issues
Preserve exposure	Rapid and complete release for immediate-release products	Limits bioequivalence failure
Reduce food sensitivity	Multiparticulate or pH-controlled release system	Improves administration flexibility
Maintain stability	Low-moisture excipients, protective coating, tight packaging	Supports longer shelf life

The formulation should not materially alter the exposure profile unless the product is designed for a new regulatory pathway. Even modest changes in dissolution can affect Cmax and AUC, particularly in patients with altered CYP2D6 activity.

What excipients are used in immediate-release propafenone tablets?

Propafenone immediate-release tablets generally use conventional solid-dose excipients. Product-specific inactive ingredients vary by manufacturer and strength. Public labels for propafenone products identify common excipient classes such as microcrystalline cellulose, starch, hypromellose, magnesium stearate, colloidal silicon dioxide, talc, polyethylene glycol, and colorants.[4][5]

The immediate-release platform is technically mature. Commercial differentiation is therefore more likely to come from excipient exclusion and manufacturing reliability than from novel release technology.

Which immediate-release excipient strategies have commercial value?

Lactose-free formulations

A lactose-free tablet can address patients with lactose intolerance, institutional formulary requirements, and procurement preferences. The commercial advantage is modest because many existing tablets already use non-lactose fillers. A lactose-free claim therefore needs supporting market research rather than being treated as a standalone premium proposition.

Dye-free formulations

Colorants can create procurement barriers for hospital systems and patient concerns about inactive ingredients. A dye-free tablet can be positioned for chronic therapy, although propafenone’s relatively specialized patient population limits the total addressable market.

Low-crospovidone or low-swelling systems

Disintegrant selection affects tablet breakup and dissolution. Excessive swelling or compression sensitivity can produce lot-to-lot variability. A controlled disintegrant and lubricant system can improve manufacturing robustness without changing the clinical profile.

Smaller tablets

Propafenone tablets are available at relatively high milligram strengths. A high-density, high-compressibility formulation can reduce tablet size and improve swallowing. This is a practical opportunity for generic or branded-generic manufacturers, especially for older patients taking multiple cardiovascular medicines.

Split-dose flexibility

Scored tablets may support titration, but a score line does not automatically establish dose uniformity after splitting. A formulation with validated splitability could be positioned for dose adjustment, provided the labeling and product design support that use.

What formulations are protected by propafenone extended-release technology?

The extended-release product is the more attractive technical target because controlled release can support once- or twice-daily dosing, reduce peak-to-trough fluctuation, and create a defensible formulation platform.

Rythmol SR is an extended-release capsule containing controlled-release drug material. Generic products may use coated pellets, matrix granules, or other multiparticulate systems if they satisfy FDA quality and bioequivalence requirements.[2][6]

Which excipients are most relevant to extended-release propafenone?

Ethylcellulose

Ethylcellulose is widely used as a water-insoluble membrane former for coated pellets. Its level, particle size, plasticizer system, coating weight, and pore-former content directly affect release.

Hypromellose

Hypromellose can be used as a hydrophilic matrix former, binder, or coating component. Higher-viscosity grades generally slow hydration and drug diffusion.

Povidone

Povidone can improve binding and coating adhesion. It may also influence drug layering and granule strength.

Triethyl citrate

Triethyl citrate is a plasticizer used in polymeric coatings. It can improve film flexibility and reduce cracking, but its level can alter permeability and release kinetics.

Talc and colloidal silicon dioxide

These materials can improve processing, reduce tack during coating, and support powder flow. Excessive use can affect coating integrity or dissolution.

Sugar spheres or microcrystalline cellulose cores

Multiparticulate systems may use inert cores for drug layering. Core size distribution and surface properties can influence dose uniformity and release consistency.

The best commercial formulation is not necessarily the one with the most novel excipient. It is the one that produces robust in vitro release, predictable in vivo performance, low manufacturing variability, and a manageable regulatory package.

When does propafenone lose exclusivity?

Propafenone has already lost U.S. small-molecule exclusivity. Generic entry is established for immediate-release and extended-release products.

Exclusivity category	Commercial status
Active-ingredient patent	Expired
Original NDA exclusivity	Expired
Immediate-release generic entry	Established
Extended-release generic entry	Established
Biosimilar pathway	Not applicable
New formulation exclusivity	Potentially available only for a qualifying new product

A new propafenone product could potentially obtain five-year new chemical entity exclusivity only if it contained a qualifying new active moiety, which a conventional propafenone reformulation would not. A 505(b)(2) product may qualify for three years of exclusivity for certain new clinical investigations supporting a change in dosage form, formulation, route, or indication. The exclusivity would be limited to the protected change and would not block all generic propafenone products.[7]

Are Paragraph IV challenges relevant to propafenone?

Paragraph IV litigation is most relevant when an ANDA applicant challenges an Orange Book-listed patent for a branded product. Because the original propafenone products are mature and generic competition is already established, the near-term litigation risk is more likely to concern a new formulation than the legacy active ingredient.

For a new propafenone extended-release product, potential Paragraph IV issues would include:

• Whether the applicant has listed a formulation patent.
• Whether the generic uses the same or a non-infringing release mechanism.
• Whether the patent claims cover dissolution characteristics or only composition.
• Whether the applicant certifies that a listed patent is invalid, unenforceable, or not infringed.
• Whether the NDA holder obtains a 30-month stay through timely patent litigation.

A formulation sponsor should expect design-around activity. Coated pellets, matrix tablets, osmotic systems, and multiparticulate capsules can often be engineered around narrowly drafted excipient claims.

What commercial opportunities exist for propafenone excipients?

Which propafenone products offer the best commercial opportunity?

Opportunity	Technical difficulty	Market attractiveness	IP potential
Standard immediate-release tablet	Low	Low to moderate	Low
Lactose-free or dye-free tablet	Low	Moderate in selected channels	Low
Smaller high-strength tablet	Moderate	Moderate	Moderate
Improved extended-release capsule	High	Moderate to high	High
Sprinkle capsule	High	Moderate	High
Ready-to-use oral suspension	High	Niche	Moderate to high
Taste-masked liquid	High	Niche	Moderate
Patient-specific compounded formulation	Moderate	Limited and fragmented	Low
Combination or precision-dosing product	High	Potentially high	High, but clinically complex

The strongest near-term opportunity is an extended-release product with a demonstrable administration or tolerability advantage. A sprinkle capsule could be useful for patients who cannot swallow capsules, although the product must maintain pellet integrity and release performance when administered over soft food.

Can propafenone support a pediatric or geriatric formulation?

The commercial case is stronger for geriatric usability than for pediatric expansion. Propafenone is used in adults, and pediatric safety and efficacy are not established in the U.S. label.[1] A pediatric liquid would require a meaningful clinical and regulatory strategy rather than an excipient change alone.

A geriatric-oriented product could focus on:

• Smaller tablets.
• Clear dose titration.
• Reduced swallowing burden.
• Lower excipient burden.
• Easy-to-open packaging.
• Taste-masked oral liquid for supervised use.
• Consistent administration with or without food.

The label warns that propafenone dosage must be individualized and titrated. A dosage form that improves titration accuracy could have practical value, but the clinical label would remain the primary commercial constraint.

What manufacturing and intellectual-property barriers exist?

Propafenone hydrochloride itself is a conventional small-molecule API, so API manufacturing is not the primary barrier. The main barriers are formulation reproducibility and bioequivalence.

Key manufacturing risks

• Content uniformity in high-dose multiparticulate capsules.
• Drug layering consistency on inert cores.
• Coating thickness and membrane permeability.
• Moisture uptake during storage.
• Capsule fill-weight control.
• Scale-up changes in spray rate, atomization, and drying.
• Dissolution shifts after accelerated stability testing.
• Food-effect differences between development batches.
• Extractables and leachables from packaging.
• Nitrosamine and elemental impurity assessment where relevant to the manufacturing process.

An extended-release propafenone product should have a dissolution method capable of distinguishing meaningful formulation changes. Single-point dissolution specifications are unlikely to provide adequate control for a complex release system.

Which geographic markets are commercially attractive?

The United States offers the clearest abbreviated regulatory pathway through ANDA or 505(b)(2). Europe and other regulated markets offer opportunities for generic extended-release products, but national pricing and reimbursement can reduce returns. Emerging markets may support immediate-release volume but often have lower margins and weaker enforcement of formulation patents.

Geographic strategy should distinguish:

• U.S. extended-release substitution.
• European generic and hybrid applications.
• Latin American branded-generic markets.
• Asian markets with lower-cost local manufacturing.
• Hospital procurement channels requiring excipient exclusions.
• Specialty pharmacy channels requiring patient-friendly administration.

How does propafenone compare with competing antiarrhythmic products?

Propafenone competes with flecainide in the Class IC category and with other rhythm-control products such as sotalol, amiodarone, and dofetilide. The competitive positioning is clinically constrained because propafenone and flecainide are generally used in patients without substantial structural heart disease, while amiodarone has broader use but a different safety profile.[1][8]

Product	Formulation opportunity	Excipient opportunity	Competitive issue
Propafenone	ER capsule, sprinkle, liquid	Release control, swallowability	Generic pricing and pharmacokinetic variability
Flecainide	IR and ER tablet	Tablet size, dose flexibility	Direct Class IC alternative
Sotalol	Tablet and oral solution	Pediatric or renal-dose administration	QT prolongation and renal dosing
Amiodarone	Tablet and liquid	Taste masking, solubilization	Toxicity and complex monitoring
Dofetilide	Capsule	Dose precision	Restricted initiation and monitoring

Propafenone’s commercial advantage is the possibility of improving administration and release control without competing against a heavily differentiated branded product. Its disadvantage is limited pricing power in ordinary generic tablets.

What is the revenue exposure for a new propafenone formulation?

Revenue exposure is likely to be moderate rather than blockbuster-scale. Propafenone is a chronic cardiovascular medicine with an established generic base, but the treated population is narrower than the population for hypertension, anticoagulation, or common lipid disorders.

The main revenue scenarios are:

1. High-volume, low-margin immediate-release generic supply.
2. Moderate-volume extended-release generic with stable reimbursement.
3. Premium branded-generic ER product supported by a patient-use advantage.
4. Niche 505(b)(2) product with new dosing, administration, or patient subgroup.
5. Contract manufacturing or licensing of controlled-release technology.

A commercial model should prioritize net price, substitution rate, pharmacy benefit manager access, and manufacturing cost. A premium excipient strategy will not create value if the product remains therapeutically interchangeable and lacks regulatory exclusivity.

How strong is the propafenone patent estate?

The legacy patent estate is weak because molecule and original-product exclusivity have expired. A newly developed formulation could have a moderate patent position if it demonstrates a technically specific release system and obtains claims covering composition, process, and use.

Patent strength would improve with:

• Multiple independent claim categories.
• Defined dissolution ranges linked to clinical performance.
• Stability data under meaningful humidity and temperature conditions.
• Claims covering pellet architecture and coating layers.
• Manufacturing-process claims that are difficult to avoid.
• Clinical data supporting reduced peak exposure or improved administration.
• Patent term extending well beyond product launch.

Patent strength would decline with:

• Broad claims based only on routine excipient substitution.
• No unexpected performance data.
• Narrow claims covering a single excipient percentage.
• Easy substitution of polymer, plasticizer, or capsule shell.
• Lack of evidence that the formulation changes clinical outcomes.

Key Takeaways

• Propafenone is a mature generic Class IC antiarrhythmic with no meaningful biosimilar issue.
• Immediate-release tablet opportunities are primarily operational and patient-use driven.
• Extended-release multiparticulate products offer the strongest formulation and IP opportunity.
• Excipient selection must account for variable CYP2D6 metabolism and the risk that dissolution changes alter exposure.
• Lactose-free, dye-free, smaller-tablet, sprinkle, and liquid products are possible niche opportunities.
• A 505(b)(2) strategy could obtain limited three-year exclusivity for a qualifying formulation or clinical change, but not new chemical entity exclusivity.
• The most defensible patent estate would combine composition, dissolution, manufacturing, and administration claims.
• Commercial returns will depend more on reimbursement, supply reliability, and clinical usability than on the propafenone molecule itself.

FAQs About Propafenone Excipient and Commercial Strategy

Can propafenone be formulated as an oral suspension?

Yes. An oral suspension is technically feasible, but development would require control of dose uniformity, sedimentation, redispersibility, chemical stability, preservative compatibility, and taste. A 505(b)(2) pathway could be considered if the formulation supports a regulatory change beyond ordinary compounding.

Is lactose-free propafenone a strong product opportunity?

It is a feasible differentiated generic strategy, but the opportunity is likely niche because many solid oral products can use non-lactose fillers. Its value would be greater in institutional procurement or patient segments with documented excipient preferences.

Can propafenone extended-release capsules be opened?

Product-specific labeling controls this issue. A capsule should not be opened, sprinkled, or crushed unless the approved label expressly permits that administration method. A new sprinkle product would need validated pellet performance and supporting regulatory data.

What is the most important quality attribute for propafenone ER capsules?

The critical quality attributes are release profile, assay, content uniformity, capsule fill weight, pellet coating integrity, moisture level, and stability. Dissolution is particularly important because it can directly affect systemic exposure.

Is a new propafenone formulation eligible for orphan-drug exclusivity?

A conventional propafenone reformulation would not ordinarily qualify. Orphan designation depends on the disease or patient population and the statutory criteria, not on excipient novelty alone. A narrow rare-disease indication would require a separate clinical and regulatory basis.

References

1. U.S. Food and Drug Administration. (2023). Rythmol (propafenone hydrochloride) tablets prescribing information. FDA.

2. U.S. Food and Drug Administration. (2023). Rythmol SR (propafenone hydrochloride) extended-release capsules prescribing information. FDA.

3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

4. DailyMed. (2024). Propafenone hydrochloride tablet: Inactive ingredients and labeling. National Library of Medicine.

5. DailyMed. (2024). Propafenone hydrochloride extended-release capsule: Inactive ingredients and labeling. National Library of Medicine.

6. U.S. Food and Drug Administration. (2018). Guidance for industry: Extended release solid oral dosage forms: Development, evaluation, and application of in vitro/in vivo correlations. FDA.

7. U.S. Food and Drug Administration. (2023). Regulatory exclusivity and patent provisions in the Hatch-Waxman Amendments. FDA.

8. Joglar, J. A., Chung, M. K., Armbrust, T., et al. (2024). 2023 ACC/AHA/ACCP/HRS guideline for the diagnosis and management of atrial fibrillation. Circulation, 149(1), e1-e156.