List of Excipients in Branded Drug TOFRANIL

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Generic Drugs Containing TOFRANIL

Company	Ingredient	NDC	Excipient
SpecGx LLC	imipramine hydrochloride	0406-9920	CALCIUM PHOSPHATE
SpecGx LLC	imipramine hydrochloride	0406-9920	CELLULOSE, MICROCRYSTALLINE
SpecGx LLC	imipramine hydrochloride	0406-9920	DOCUSATE SODIUM
SpecGx LLC	imipramine hydrochloride	0406-9920	FERRIC OXIDE RED
SpecGx LLC	imipramine hydrochloride	0406-9920	FERROSOFERRIC OXIDE

What are the Most Frequently-Used Excipients in TOFRANIL?

# Of NDCs	Excipient
2	CALCIUM PHOSPHATE
2	CELLULOSE, MICROCRYSTALLINE
2	DOCUSATE SODIUM
2	FERRIC OXIDE RED
2	FERROSOFERRIC OXIDE

Tofranil Excipient Strategy and Commercial Opportunities for Imipramine Formulations

Last updated: October 20, 2026

Tofranil is the original brand for imipramine, a tricyclic antidepressant approved in the United States in 1959. The commercial opportunity is no longer an originator-patent play. It is a formulation and lifecycle-management opportunity centered on low-cost generic differentiation, pediatric acceptability, adherence, modified release, and controlled delivery.

The most practical targets are oral liquids, orally disintegrating tablets, smaller-dose pediatric products, taste-masked formulations, and modified-release products. Any new product must address imipramine’s bitter taste, dose flexibility, psychiatric-use adherence, anticholinergic tolerability, and the regulatory burden associated with a narrow therapeutic margin and active metabolite exposure.

What is Tofranil and which active ingredient does it contain?

Tofranil contains imipramine hydrochloride. Imipramine is a tricyclic antidepressant indicated primarily for depression and, in certain labeling, childhood enuresis. The drug is metabolized in part to desipramine, a pharmacologically active metabolite. The product is available in tablet and capsule forms, with historical Tofranil and Tofranil-PM products representing different salt and dosage-form approaches.

Attribute	Tofranil
Active ingredient	Imipramine hydrochloride
Therapeutic class	Tricyclic antidepressant
Primary dosage forms	Tablets; pamoate capsules under Tofranil-PM
U.S. approval history	Original imipramine approval in 1959
Main current competition	Generic imipramine hydrochloride tablets and capsules
Regulatory category	Small-molecule drug
Biosimilar exposure	None
Main commercial issue	Generic erosion and limited brand differentiation
Primary formulation opportunity	Palatable, flexible-dose, adherence-oriented oral products

The pharmacology creates a formulation tradeoff. Higher exposure can increase anticholinergic, cardiovascular and central-nervous-system adverse effects, while inconsistent administration can reduce treatment persistence. Excipient selection must therefore support dose uniformity and predictable release rather than merely reduce manufacturing cost. [1]

What excipients are used in Tofranil and generic imipramine products?

Public labeling identifies conventional excipient systems for imipramine tablets and capsules. Exact inactive ingredients can vary by manufacturer, strength, market and product year. Typical systems include lactose or another diluent, starch-based disintegrants, stearates or other lubricants, film-coating materials, pigments and capsule-shell components.

The commercial relevance of these ingredients is limited when the goal is a standard immediate-release generic. Conventional excipients are widely available and generally do not create meaningful differentiation. Their role becomes more important when a company pursues palatability, modified release, low-dose accuracy or a new route of administration.

Excipient functions in imipramine products

Formulation function	Common excipient strategy	Commercial purpose
Dilution	Lactose, microcrystalline cellulose, calcium phosphate	Provides tablet mass and dose uniformity
Disintegration	Pregelatinized starch, sodium starch glycolate, crospovidone	Supports rapid tablet breakup
Lubrication	Magnesium stearate, stearic acid	Controls sticking and ejection
Flow improvement	Colloidal silicon dioxide	Improves powder handling
Film coating	Hypromellose, polyethylene glycol, pigments	Improves appearance, swallowing and handling
Taste masking	Polymer film, ion-exchange resin, lipid or multiparticulate coating	Reduces bitterness in liquid and orally disintegrating products
Suspension stabilization	Cellulose derivatives, xanthan gum or other suspending agents	Maintains dose uniformity in oral liquids
Palatability	Sweeteners, flavors and acidulants	Improves pediatric and geriatric acceptability
Modified release	Hydrophilic polymers, insoluble polymers, multiparticulate coatings	Reduces peak-to-trough exposure and dosing frequency

Excipient compatibility requires particular attention to moisture, pH, oxidation and adsorption. Imipramine is a weakly basic compound, so pH-dependent solubility and salt selection can affect dissolution, precipitation and taste. A liquid formulation also requires control of microbial growth, preservative compatibility and container adsorption.

What formulation patents protect imipramine and Tofranil?

The core composition-of-matter and basic oral-product protection for imipramine expired decades ago. Tofranil does not have the type of active patent estate associated with a recently launched branded drug.

The remaining intellectual-property opportunity lies in narrow formulation claims, including:

• Specific polymeric taste-masking systems
• Controlled-release matrices
• Coated pellets or multiparticulates
• Oral liquid compositions with defined pH and preservative systems
• Low-dose pediatric formulations
• Combination products
• Manufacturing processes that improve content uniformity or dissolution
• Device-related claims for dosing oral liquids

A formulation patent must provide more than a conventional excipient substitution. A claim directed only to combining imipramine with a routine diluent, lubricant or sweetener would face substantial obviousness risk. Stronger claims would link a defined excipient system to a measurable result, such as reduced bitterness, a specified dissolution profile, improved stability or reduced dose variability.

Patent strength assessment

Patent area	Expected strength	Reason
Imipramine molecule	None for new entry	Long-expired foundational protection
Conventional tablets	Low	Mature technology and extensive prior art
Standard oral liquid	Low to moderate	Routine excipient options are well known
Taste-masked pediatric liquid	Moderate	Strength depends on sensory and stability data
Multiparticulate modified release	Moderate	More technical differentiation is possible
Novel delivery device	Moderate	Device claims may create separate protection
Combination therapy	Variable	Clinical and obviousness risks are high
Manufacturing process	Moderate	Stronger if the process produces a reproducible technical effect

When does Tofranil lose exclusivity?

Tofranil’s U.S. market exclusivity expired long ago. Imipramine has been commercially available as a generic for many years, and no current orphan exclusivity or new chemical entity exclusivity protects the molecule.

The relevant exclusivity position is therefore:

Exclusivity category	Current position
New chemical entity exclusivity	Expired
Basic compound patent	Expired
Traditional formulation protection	Expired or commercially irrelevant
Pediatric exclusivity	No current meaningful barrier identified
Orphan exclusivity	Not applicable to the core product
Biosimilar exclusivity	Not applicable
Generic entry barrier	Primarily regulatory, manufacturing and commercial

What is the Orange Book status of Tofranil?

The FDA Orange Book is relevant to approved imipramine products, but a commercial review should distinguish historical brand listings from currently marketed products. Tofranil and Tofranil-PM have longstanding approval histories, while generic imipramine products are approved through abbreviated new drug applications.

For a new immediate-release generic, the central pathway is an ANDA requiring pharmaceutical equivalence and bioequivalence to the reference listed drug. For a differentiated formulation, an ANDA may not be sufficient if the dosage form, route, release characteristics or inactive ingredients materially depart from the reference product. A 505(b)(2) application may be more suitable where the sponsor relies partly on published literature or an approved product but seeks approval for a new formulation or clinical use. [2]

Paragraph IV challenge considerations

Paragraph IV litigation is unlikely to create meaningful value around the old Tofranil molecule itself because the primary protection has expired. It could become relevant if a new formulation patent is listed for a later-approved product. The business case would then depend on:

1. Whether the patent is eligible for Orange Book listing.
2. Whether the claims cover the proposed generic product.
3. Whether the reference product has commercial sales sufficient to justify litigation.
4. Whether a first-filer advantage exists.
5. Whether the patented formulation has meaningful market share.

A sponsor developing a new imipramine formulation should not assume that an FDA-approved product automatically creates broad patent protection. Orange Book listing is governed by specific FDA rules and generally does not extend to every manufacturing, packaging or general-use claim. [2,3]

Which excipient strategies offer the strongest commercial opportunity?

1. Pediatric oral liquid

A palatable oral liquid is the clearest unmet formulation opportunity. Pediatric enuresis use creates a logical target population, although current prescribing must follow the applicable labeling and clinical practice.

A commercial liquid would need:

• Accurate dosing at low concentrations
• A stable imipramine salt or compatible pH system
• Taste masking that survives storage
• A preservative system compatible with the active ingredient
• A child-resistant, calibrated dosing device
• Low sedimentation and easy redispersion if formulated as a suspension
• Packaging that limits light, moisture and adsorption

A solution may provide better dose uniformity than a suspension but can impose greater taste and solubility challenges. A suspension can improve taste masking by reducing dissolved drug, but it requires tighter control of particle size, redispersibility and dose uniformity.

2. Orally disintegrating tablet

An orally disintegrating tablet could target patients who have difficulty swallowing conventional tablets. The principal technical problem is bitterness. The excipient strategy would likely combine a rapidly disintegrating matrix with coated drug particles, ion-exchange resin complexes or a polymer barrier.

A successful product would need to balance:

• Fast disintegration
• Low tablet friability
• Acceptable mouthfeel
• Adequate drug loading
• Low residual bitterness
• Moisture protection
• Dose strengths suitable for titration

Simple direct compression is unlikely to provide sufficient differentiation unless supported by superior sensory data or manufacturing economics.

3. Taste-masked multiparticulates

Coated pellets or granules could be packaged in capsules, sachets or sprinkle products. Multiparticulates allow separation of drug loading, taste masking and release control. They also create a platform for multiple strengths.

This approach may be attractive for:

• Pediatric administration
• Patients unable to swallow tablets
• Flexible dose titration
• Modified-release products
• Combination of immediate- and extended-release fractions

The principal risks are coating variability, dose dumping, content uniformity and higher manufacturing cost.

4. Modified-release formulation

A once-daily or less frequent imipramine product could improve adherence and reduce peak-related adverse effects. The opportunity is technically credible but clinically demanding. Imipramine’s active metabolite and pharmacodynamic effects mean that a new release profile would require pharmacokinetic and, depending on the product, clinical justification.

A modified-release program would need to establish:

• Bioequivalence or an acceptable exposure relationship
• Consistent imipramine and desipramine exposure
• Food-effect behavior
• Alcohol-induced dose dumping risk
• Stability through the proposed shelf life
• Lack of clinically important accumulation

This is a higher-investment strategy than a standard generic and is more likely to use a 505(b)(2) pathway than a conventional ANDA.

5. Low-dose and precision-dosing products

Imipramine therapy may require titration. Low-dose tablets, scored tablets or unit-dose liquid presentations can improve dose adjustment. The technical value lies in content uniformity at low drug loads and reproducible splitting or measurement.

Excipient selection should prioritize:

• Uniform drug distribution
• Low segregation during blending
• Robust tablet hardness at small size
• Reliable breakability
• Minimal weight variation
• Dosing-device accuracy for liquids

This strategy has lower patent strength but may support pharmacy, pediatric and specialty-channel differentiation.

How does Tofranil compare with competing tricyclic antidepressants?

Imipramine competes with generic amitriptyline, nortriptyline, desipramine, doxepin and clomipramine, along with newer antidepressant classes. Most competing tricyclics also face long-expired core patents and generic pricing pressure.

Drug	Main formulation opportunity	Competitive position
Imipramine	Pediatric liquid, ODT, modified release	Established generic; differentiated delivery may create value
Amitriptyline	Liquid, low-dose tablets, combination products	Larger generic market and stronger physician familiarity
Nortriptyline	Oral liquid and precision dosing	Useful for titration and tolerability management
Desipramine	Low-dose and liquid formats	Smaller market, potentially lower competition
Clomipramine	Modified release and tolerability-oriented delivery	More specialized psychiatric demand
Doxepin	Low-dose liquid or sleep-related delivery	Different commercial and regulatory positioning

Imipramine has an advantage in historical pediatric enuresis positioning. Amitriptyline has broader recognition and a larger off-label market. A new imipramine product would need a clear use-case rather than rely on molecule familiarity.

What FDA regulatory status applies to new imipramine products?

A conventional generic tablet normally follows the ANDA pathway. A new dosage form, new route, new strength outside the reference-product framework or clinically differentiated release profile may require a 505(b)(2) application.

Regulatory pathway comparison

Product concept	Likely pathway	Main evidence burden
Same-strength immediate-release tablet	ANDA	Pharmaceutical equivalence and bioequivalence
Same tablet with different inactive ingredients	ANDA, if requirements are met	Inactive-ingredient justification and bioequivalence
Oral solution or suspension	ANDA or 505(b)(2), depending on reference framework	Dose uniformity, stability, bioequivalence, safety
ODT	ANDA or 505(b)(2)	Dissolution, sensory performance, bioequivalence
Modified release	Usually 505(b)(2) or applicable ANDA route	Comparative pharmacokinetics, food effect and release characterization
New combination	505(b)(2) or NDA	Clinical and interaction evidence
New pediatric indication	505(b)(2) or supplemental application	Indication-specific evidence

FDA’s inactive-ingredient database can support selection of excipients with prior oral-use history, but prior use does not eliminate the need to assess dose, route, population and formulation-specific safety. [4]

What manufacturing and intellectual-property barriers exist?

The lowest-risk product is a conventional immediate-release tablet, but its commercial value is also limited. The main barriers are price erosion, manufacturing scale and supply reliability.

Higher-value products face different barriers:

• Taste masking can increase process steps and analytical testing.
• Multiparticulate coating requires tight control of coating weight and particle-size distribution.
• Oral liquids require preservative efficacy, microbial control and packaging validation.
• Low-dose products require blend uniformity and segregation controls.
• Modified-release products require discriminatory dissolution methods and dose-dumping studies.
• Pediatric products require human sensory evaluation and age-appropriate administration data.
• New excipient use may require additional toxicology or FDA review.

Manufacturing know-how can be more defensible than a broad excipient patent. A process that consistently produces low bitterness, narrow dissolution variability or stable low-dose content may support trade-secret protection, process patents and customer contracts even when composition claims are narrow.

What revenue exposure and market opportunity exist?

The branded Tofranil franchise is unlikely to provide a large protected-revenue opportunity because generic imipramine has been available for decades. Publicly available information does not establish a current, separately reported Tofranil revenue base that would support a reliable brand valuation.

Commercial opportunities are more likely to come from:

• Higher-margin pediatric products
• Hospital and institutional supply
• Specialty pharmacy distribution
• Difficult-to-manufacture oral liquids
• Unit-dose and adherence packaging
• Licensed 505(b)(2) products
• Contract manufacturing of low-volume psychiatric liquids
• Regional products in markets where generic availability is limited

A product developer should assess market size by dosage form, not by total imipramine prescriptions. A standard tablet may have volume but little margin. A palatable liquid or precision-dose product may have lower unit volume but stronger pricing and lower direct competition.

What licensing deals and settlement agreements affect Tofranil?

No major current licensing deal or settlement agreement is required to explain the commercial position of legacy Tofranil. The molecule’s long commercial history and generic availability mean that value is more likely to arise from a new formulation owner, contract manufacturer, excipient supplier or delivery-platform licensor.

Potential transaction structures include:

• Exclusive regional rights to a pediatric liquid
• Co-development of a modified-release product
• Supply agreements for coated drug particles
• Royalty-bearing licenses to taste-masking technology
• Contract manufacturing with minimum annual volumes
• Asset acquisition of an approved 505(b)(2) product

A license should be evaluated against the scope of formulation claims, Orange Book listing potential, manufacturing transferability, FDA approval status and the number of directly substitutable generic products.

What generic launch scenarios exist for new imipramine products?

Immediate-release generic tablet

This is the fastest and least differentiated scenario. Entry is technically straightforward, but pricing pressure is severe. The product is suitable for a low-capital generic portfolio, not a premium lifecycle strategy.

Pediatric liquid launch

This scenario offers better differentiation. The main launch risks are taste acceptance, pharmacy substitution rules, preservative stability, device usability and payer willingness to reimburse a premium.

Modified-release launch

This scenario offers the highest potential differentiation but requires the greatest regulatory and clinical investment. The value depends on demonstrating a meaningful adherence or tolerability advantage.

ODT or sprinkle product

This can occupy a middle position. The product may reach swallowing-impaired and pediatric populations, but the commercial case depends on sensory performance and whether the dosage form is covered by existing generic substitution practices.

Key Takeaways

• Tofranil is the historical brand for imipramine, and its core patent and exclusivity position has expired.
• No biosimilar issue exists because imipramine is a small-molecule drug.
• Conventional tablet excipients offer little defensible differentiation.
• The strongest formulation opportunities are pediatric oral liquid, taste-masked multiparticulates, ODT and modified release.
• A standard immediate-release product generally fits the ANDA pathway; a materially different delivery system may require 505(b)(2).
• New patent value would need to come from a defined formulation, measurable technical effect or manufacturing process.
• The primary commercial risk is generic price erosion, not patent litigation.
• The most attractive opportunity is a clinically usable, palatable and dose-flexible product supported by manufacturing know-how and targeted distribution.

FAQs About Tofranil Excipient and Formulation Opportunities

Can imipramine be developed as a pediatric oral liquid?

Yes. A pediatric oral liquid is technically feasible, but taste masking, dose uniformity, preservative efficacy, stability and dosing-device accuracy are central development requirements.

Is Tofranil protected by active U.S. patents?

The foundational imipramine and Tofranil protections expired long ago. Any meaningful current protection would likely depend on a later, narrowly drafted formulation, manufacturing or device patent.

Would a new imipramine liquid qualify as an ANDA?

It may qualify if it can demonstrate the required equivalence to an appropriate reference product. A materially different formulation, indication or clinical use may require a 505(b)(2) application.

What is the best excipient platform for taste-masked imipramine?

Polymer-coated drug particles, ion-exchange resin complexes and multiparticulate systems are the leading technical options. The best platform depends on the target dose, desired dosage form, pH, release profile and sensory results.

Can a modified-release imipramine product command premium pricing?

Potentially, but premium pricing would require evidence of a meaningful benefit, such as fewer daily doses, improved adherence or reduced peak-related adverse effects. Manufacturing complexity alone is unlikely to support durable pricing.

References

1. DailyMed. (n.d.). Imipramine hydrochloride tablet prescribing information. U.S. National Library of Medicine.
2. U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application (ANDA): Generics. FDA.
3. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
4. U.S. Food and Drug Administration. (n.d.). Inactive ingredient database. FDA.
5. U.S. Food and Drug Administration. (n.d.). Tofranil and imipramine drug labeling and approval history. Drugs@FDA.