List of Excipients in Branded Drug FORTESTA

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Endo Pharmaceuticals Inc	FORTESTA	testosterone	63481-183	ALCOHOL
Endo Pharmaceuticals Inc	FORTESTA	testosterone	63481-183	BUTYLATED HYDROXYTOLUENE
Endo Pharmaceuticals Inc	FORTESTA	testosterone	63481-183	ISOPROPYL ALCOHOL
Endo Pharmaceuticals Inc	FORTESTA	testosterone	63481-183	OLEIC ACID
Endo Pharmaceuticals Inc	FORTESTA	testosterone	63481-183	PROPYLENE GLYCOL
Endo Pharmaceuticals Inc	FORTESTA	testosterone	63481-183	TROLAMINE

FORTESTA Excipient Strategy and Commercial Opportunities in Testosterone Gel

Last updated: August 4, 2026

FORTESTA is a testosterone replacement product formulated as a 2% hydroalcoholic transdermal gel. Its excipient system combines ethanol and propylene glycol as solvents, isopropyl myristate and oleic acid as penetration-enhancing components, carbomer 980 as the gel-forming polymer, sodium hydroxide as a neutralizer, and purified water as the aqueous vehicle.[1] The commercial opportunity is no longer based on basic testosterone delivery. It is based on improving skin tolerability, dose reproducibility, transfer control, packaging, and bioequivalence against an established formulation.

What is FORTESTA and how is it formulated?

FORTESTA is approved for testosterone replacement in adult males with conditions associated with deficient or absent endogenous testosterone.[1] It is administered to the front and inner thighs through a metered pump.

Product attribute	FORTESTA specification
Active ingredient	Testosterone
Dosage form	Transdermal gel
Concentration	2% w/w
Delivered dose	10 mg testosterone per actuation
Pump configuration	0.5 g gel per actuation
Application site	Front and inner thighs
Initial labeled regimen	Two actuations daily, subject to titration
FDA approval	2010
Regulatory category	Prescription drug; testosterone is a controlled substance in the United States
Key delivery challenge	Achieving systemic absorption while limiting transfer to other people

The product is a hydroalcoholic gel. The labeled inactive ingredients are carbomer 980, isopropyl myristate, oleic acid, propylene glycol, purified water, and sodium hydroxide.[1]

What does each FORTESTA excipient do?

Excipient	Technical role	Commercial relevance
Ethanol	Primary volatile solvent and skin-permeation aid	Supports rapid drying but can cause stinging, dryness, odor, and flammability concerns
Propylene glycol	Cosolvent, humectant, and penetration enhancer	Can improve testosterone solubilization but may contribute to irritation in sensitive users
Isopropyl myristate	Lipophilic penetration enhancer and emollient	Improves partitioning into the stratum corneum; may affect skin feel and residue
Oleic acid	Fatty-acid penetration enhancer	Fluidizes skin lipids; may increase irritation or oxidation sensitivity
Carbomer 980	Gelling and viscosity-control polymer	Controls application behavior, dose retention, and pump delivery
Sodium hydroxide	Carbomer neutralizer and pH adjuster	Controls gel viscosity and product stability
Purified water	Aqueous phase	Determines solvent balance, evaporation profile, and skin feel

The formulation is designed around a balance between testosterone solubility, skin permeation, drying time, viscosity, and dose delivery. Changing one excipient can alter all five parameters.

What excipient strategy protects the commercial performance of FORTESTA?

The core strategy is to preserve the product’s pharmacokinetic profile while reducing user friction. The highest-value formulation variables are solvent composition, penetration-enhancer selection, polymer concentration, pH, and pump compatibility.

Solvent and cosolvent optimization

Ethanol enables rapid drying and helps maintain testosterone in solution. Its disadvantages include burning on compromised skin, skin dehydration, odor, and flammability labeling. Propylene glycol increases solvent capacity and can retain moisture, but excessive levels may increase tackiness or irritation.

Potential development programs include:

1. Lower-ethanol formulations using alternative cosolvents.
2. Ethanol-free gels based on propylene glycol, polyethylene glycol derivatives, glycols, or carefully selected lipid vehicles.
3. Volatile solvent blends that shorten drying time without increasing skin irritation.
4. Solvent systems that reduce crystallization after application.

An ethanol-free or low-ethanol formulation could support a differentiated product, but it would require new comparative pharmacokinetic work. Testosterone’s low aqueous solubility makes complete replacement of ethanol technically difficult.

Penetration-enhancer selection

FORTESTA uses both isopropyl myristate and oleic acid. This combination increases testosterone transport through the stratum corneum but also creates opportunities for reformulation.

Potential alternatives include fatty acid esters, medium-chain glycerides, selected terpenes, alkyl glycols, and other dermatologically accepted permeation enhancers. The commercial objective should not be maximum penetration. Excessive permeation can increase peak exposure, interpatient variability, and transfer risk.

A stronger formulation program would measure:

• Testosterone flux across human skin.
• Lag time to absorption.
• Residual testosterone on the skin surface.
• Drying time.
• Skin irritation and sensitization.
• Interpatient pharmacokinetic variability.
• Transfer after contact with clothing or another person.

Polymer and rheology design

Carbomer 980 controls viscosity and gel structure. A lower-viscosity system may dry faster and spread more easily, but it can increase runoff and dosing loss. A higher-viscosity system may improve retention but leave residue and create pump-delivery problems.

Commercially useful alternatives include modified carbomers, acrylate crosspolymers, cellulose derivatives, poloxamers, and associative thickeners. A formulation patent could claim a defined polymer concentration, neutralization level, viscosity range, or rheological profile rather than the active ingredient alone.

The strongest claims would connect rheology to a measurable product benefit, such as:

• Consistent testosterone delivery per pump actuation.
• Reduced crystallization.
• Shorter drying time.
• Lower residual transfer.
• Improved dose uniformity over the product shelf life.

pH and skin compatibility

Sodium hydroxide neutralizes the carbomer and sets the gel’s pH. The pH must balance carbomer viscosity, testosterone stability, preservative performance, and skin tolerance. A reformulation that changes pH without controlling polymer neutralization can produce a materially different product.

A differentiated product could target lower stinging, reduced erythema, or improved use on dry skin. These claims would need clinical or dermatologic support and would be difficult to establish through excipient selection alone.

What formulation patents could protect a FORTESTA follow-on product?

A follow-on formulation should avoid relying on a narrow composition claim that can be designed around. The strongest intellectual-property package would combine composition, performance, packaging, and use claims.

Composition claims

Potential claim elements include:

• Testosterone concentration.
• Ethanol-to-cosolvent ratio.
• Specific penetration-enhancer combinations.
• Carbomer or polymer concentration.
• pH range.
• Viscosity range.
• Water activity.
• Solubility or crystallization limits.

Performance claims

Performance-based claims can be commercially important where the formulation is difficult to distinguish by ingredients alone. Examples include:

• A specified testosterone flux range through human cadaver skin.
• A defined drying time.
• Reduced residual testosterone after application.
• Dose uniformity across pump actuations.
• Reduced transfer following contact with fabric or skin.
• Stable testosterone content after accelerated storage.

Packaging claims

The metered pump is part of the product’s dose-control system. Patentable opportunities may include:

• Pump mechanisms that deliver 0.5 g per actuation.
• Container designs that limit evaporation.
• Materials that reduce testosterone adsorption.
• Closure systems that reduce leakage.
• Child-resistant or tamper-evident packaging.
• Applicators that minimize hand contact.

Packaging claims can remain commercially relevant after composition claims expire if they protect a dispensing system required for reliable dosing.

Method-of-use claims

Potential method claims include application to the thighs, dosing titration based on serum testosterone, and use of a specific formulation to reduce transfer. Method-of-use protection is generally weaker against a generic that uses the same active ingredient for the same approved indication, particularly where the use is already disclosed in the reference label.

What is the FDA and Orange Book status of FORTESTA?

FORTESTA was approved under NDA 022219 in 2010.[1] Testosterone products are prescription therapies, and testosterone is regulated as a Schedule III controlled substance in the United States.[2]

The FDA Orange Book is the relevant source for listed patents, exclusivity, therapeutic-equivalence codes, and approved reference products.[3] FORTESTA’s regulatory value is constrained by the availability of other testosterone gels, including 1%, 1.62%, and 2% products. The principal generic-entry pathway is an abbreviated new drug application, not a biosimilar application, because testosterone is a chemically synthesized small molecule.

A company evaluating a FORTESTA generic must review:

• Current Orange Book patent listings.
• The reference listed drug and dosage-form designation.
• Paragraph IV certifications.
• FDA approval status of testosterone gel 2% ANDAs.
• Label carve-outs for any method-of-use patents.
• Controlled-substance manufacturing and distribution requirements.

Patent expiration dates should be taken from the current Orange Book and patent records rather than inferred from the original approval date. Patent term adjustment, patent term extension, terminal disclaimers, and pediatric exclusivity can change the effective date.

When does FORTESTA lose exclusivity and what generic-entry risks exist?

FORTESTA’s commercial protection is exposed to three forms of competition:

1. Generic testosterone gel 2% products.
2. Substitutable testosterone gels at different concentrations.
3. Alternative delivery systems, including injections, patches, buccal systems, and oral testosterone products.

Paragraph IV risk

An ANDA applicant may file a Paragraph IV certification alleging that an Orange Book-listed patent is invalid, unenforceable, or not infringed. The reference sponsor can file infringement litigation within the statutory period, triggering a potential 30-month stay of approval under the Hatch-Waxman framework.[4]

The practical risk depends on whether the listed patents cover:

• The active ingredient, which is generally vulnerable once basic compound protection has expired.
• A specific gel composition.
• A pump or container.
• A method of treating testosterone deficiency.
• A manufacturing process.

Composition and device patents often create more meaningful barriers than broad method-of-use patents when the generic product can omit or carve out protected uses.

Generic launch scenarios

Scenario	Market effect
First approved 2% generic	Steep price pressure and rapid payer substitution
Multiple 2% generics	Commodity pricing and limited differentiation
Authorized generic	Lower disruption to the brand owner but reduced generic upside
Formulation-improved follow-on	Potential premium pricing if tolerability or transfer is measurably better
Device-led reformulation	Opportunity for controlled dosing and lifecycle extension

How strong is the FORTESTA patent estate?

The estate is strongest where it protects the integrated product rather than testosterone alone. A formulation claim covering a defined solvent and enhancer system can create an entry barrier if the generic requires the same composition to meet bioequivalence. Its practical strength falls when alternative vehicles can deliver comparable exposure.

The main weaknesses are:

• Multiple established testosterone delivery technologies.
• Availability of other approved testosterone gels.
• The possibility of designing around individual excipients.
• Difficulty proving infringement of functional performance claims.
• Limited protection from method-of-use claims where the indication is central to the product label.

A follow-on developer should pursue a layered estate covering formulation composition, pump performance, packaging, skin-transfer reduction, and manufacturing controls. One broad formulation patent is unlikely to provide durable protection.

What commercial opportunities exist for FORTESTA excipients?

Lower-irritation testosterone gel

A low-ethanol or ethanol-free gel could target patients who discontinue therapy because of burning, dryness, odor, or residue. The opportunity depends on proving comparable testosterone exposure and better dermatologic outcomes.

Reduced-transfer formulation

Transfer to women and children is a central safety concern for topical testosterone products.[1] A gel that dries faster, leaves less surface residue, or uses a film-forming barrier could support a differentiated product and premium positioning.

Improved pump and dose uniformity

Dose delivery is an underdeveloped commercial opportunity. Excipient viscosity, pump geometry, priming behavior, and container compatibility should be developed together. A stable 0.5 g actuation across the bottle’s life can reduce underdosing and improve regulatory defensibility.

Lower-VOC and sustainability positioning

Reducing ethanol may lower volatile organic compound emissions and improve shipping and storage characteristics. This opportunity is secondary to pharmacokinetic performance, but it can support hospital, specialty-pharmacy, and international-market positioning.

International adaptation

Excipient restrictions, labeling requirements, and packaging standards vary by jurisdiction. A platform using widely accepted pharmaceutical excipients can reduce regulatory friction. The United States, European Union, Canada, Australia, and selected Asian markets should be evaluated separately for excipient acceptability and testosterone-control requirements.

How does FORTESTA compare with other testosterone delivery systems?

Delivery system	Main advantage	Main limitation	Excipient opportunity
FORTESTA 2% gel	Flexible daily dosing and thigh application	Transfer, drying, and skin irritation	Solvent, enhancer, polymer, and pump reformulation
Testosterone gel 1.62%	Established dosing platform	Larger application volume or different dose calibration	Improved drying and transfer control
Testosterone patches	Continuous delivery	Skin adhesion and irritation	Adhesive and permeation-layer design
Injectable testosterone	Infrequent dosing	Peaks, troughs, injection burden	Limited excipient differentiation
Oral testosterone undecanoate	Oral administration	Food dependence and systemic safety considerations	Lipid vehicle and absorption enhancement
Buccal testosterone	Avoids skin transfer	Local mouth irritation and adherence	Mucoadhesive polymer systems

FORTESTA’s most defensible commercial niche is a low-transfer, low-irritation transdermal product with reliable pump dosing. Competing on testosterone concentration alone is unlikely to provide durable differentiation.

Key Takeaways

• FORTESTA uses a hydroalcoholic testosterone gel containing carbomer 980, isopropyl myristate, oleic acid, propylene glycol, sodium hydroxide, water, and volatile solvent components.[1]
• The most valuable excipient opportunities involve ethanol reduction, skin tolerability, drying time, transfer control, and dose uniformity.
• Testosterone is a small molecule, so generic competition proceeds through ANDAs and Paragraph IV certifications rather than biosimilar applications.
• The strongest follow-on patent strategy combines formulation, performance, pump, packaging, and manufacturing claims.
• A differentiated product should target reduced transfer and improved tolerability rather than simply changing the testosterone concentration.
• Orange Book listings, current patent term data, and ANDA litigation must be verified against the current FDA and USPTO records before investment or litigation decisions.[3]

FAQs

Can an ethanol-free FORTESTA formulation be commercially viable?

Yes, but it must maintain testosterone solubility, skin permeation, drying performance, and pharmacokinetic comparability. Ethanol-free systems may require higher cosolvent or enhancer levels, which can affect irritation and residue.

Which FORTESTA excipient is most important for transdermal absorption?

The penetration-enhancer system is the most important absorption lever. In FORTESTA, isopropyl myristate, oleic acid, ethanol, and propylene glycol operate as an integrated system rather than as independent ingredients.

Can a generic copy FORTESTA’s excipients?

A generic may use the same excipients if the relevant patents have expired and the product meets FDA requirements. Active patents covering composition, performance, packaging, or device features can require design-around strategies.

Is FORTESTA eligible for biosimilar competition?

No. Testosterone is a chemically synthesized small molecule. The relevant pathway is an ANDA under the Hatch-Waxman framework, subject to pharmaceutical-equivalence, bioequivalence, labeling, and patent-certification requirements.

What is the best lifecycle-management strategy for FORTESTA?

The strongest strategy is a reformulated product with lower transfer, faster drying, reduced irritation, and a controlled-dose pump, supported by patents covering the composition, dispensing system, and measurable performance characteristics.

References

1. U.S. Food and Drug Administration. (2018). FORTESTA (testosterone) gel, for topical use: Prescribing information. Endo Pharmaceuticals Inc.

2. U.S. Drug Enforcement Administration. (2024). Controlled substances schedules. U.S. Department of Justice.

3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. U.S. Department of Health and Human Services.

4. U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions: Patent certifications and the 30-month stay. U.S. Department of Health and Human Services.