List of Excipients in Branded Drug ENALAPRIL MALEATE ORAL SOLUTION

Generic Drugs Containing ENALAPRIL MALEATE ORAL SOLUTION

Company	Ingredient	NDC	Excipient
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	ANHYDROUS CITRIC ACID
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	HYDROCHLORIC ACID
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	PROPYLENE GLYCOL
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	SODIUM BENZOATE
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	SODIUM HYDROXIDE
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	SODIUM PHOSPHATE, DIBASIC, ANHYDROUS
Camber Pharmaceuticals Inc	enalapril maleate	31722-020	SUCRALOSE

What are the Most Frequently-Used Excipients in ENALAPRIL MALEATE ORAL SOLUTION?

# Of NDCs	Excipient
2	ANHYDROUS CITRIC ACID
1	BERRY
1	CITRIC ACID MONOHYDRATE
4	HYDROCHLORIC ACID
2	METHYLPARABEN
3	PROPYLENE GLYCOL
2	PROPYLPARABEN

Enalapril Maleate Oral Solution: Excipient Strategy, Patent Position, and Commercial Opportunities

Last updated: September 24, 2026

Enalapril maleate oral solution is a specialized liquid dosage form for pediatric patients, adults with dysphagia, patients receiving enteral nutrition, and institutions that need a standardized alternative to extemporaneous compounding. The commercial opportunity is concentrated in formulation quality, dosing accuracy, palatability, preservative systems, packaging, and regulatory differentiation rather than in new chemical-entity exclusivity.

The reference product, Epaned, contains enalapril maleate at 1 mg/mL and uses a citrate-buffered aqueous system with sodium benzoate as preservative. The active ingredient, enalapril maleate, is off-patent as a molecule and is widely available in tablet form. Product-level barriers arise from the liquid formulation, stability profile, manufacturing process, device configuration, and approved labeling. (U.S. Food and Drug Administration [FDA], 2013)

What is the FDA regulatory status of enalapril maleate oral solution?

Epaned is an FDA-approved oral solution of enalapril maleate marketed under NDA 204708. The product is indicated for the treatment of hypertension in adults and pediatric patients. The labeled strength is 1 mg/mL. (FDA, 2013)

Regulatory attribute	Publicly reported position
Active ingredient	Enalapril maleate
Dosage form	Oral solution
Strength	1 mg/mL
Reference product	Epaned
NDA	204708
Applicant at original approval	Silvergate Pharmaceuticals
Current commercial platform	Azurity Pharmaceuticals
FDA pathway	Full NDA approval for a liquid dosage form
Primary patient segments	Pediatric hypertension, dysphagia, enteral administration
NCE exclusivity	Not applicable to the established enalapril active moiety
Three-year product exclusivity	Any original period associated with the oral-solution approval has expired
Biosimilar pathway	Not applicable

Epaned was developed to provide a standardized oral liquid where enalapril tablets are difficult to administer. The approval does not create exclusivity for enalapril generally. It protects the approved product through the applicable formulation, method, process, and regulatory frameworks.

What excipients are used in enalapril maleate oral solution?

The Epaned formulation uses a relatively simple aqueous excipient system:

• Purified water as the vehicle
• Citric acid and sodium citrate as the buffer system
• Sodium benzoate as the preservative
• Flavoring components for palatability

The formulation objective is to maintain chemical stability of enalapril maleate and limit degradation in an aqueous environment. The excipient system also must support acceptable taste, microbial control, dose uniformity, and compatibility with oral syringes and enteral tubes.

Why is citrate buffering commercially important?

Enalapril maleate is susceptible to hydrolytic degradation in aqueous formulations. A controlled acidic environment can improve stability by reducing the rate of degradation of the ester-containing molecule. The citrate system also provides a commercially familiar buffer with established pharmaceutical use.

The buffer is not a minor formulation choice. A competing product that changes pH, buffer capacity, or ionic strength may alter:

• Chemical stability
• Degradation-product formation
• Preservative performance
• Taste
• Container compatibility
• In-use shelf life
• Nasogastric-tube compatibility

A formulation developer should optimize target pH and buffer capacity together rather than treat pH as an isolated specification.

What is the role of sodium benzoate?

Sodium benzoate provides antimicrobial preservation in the multidose bottle. Its performance depends on pH because the unionized benzoic-acid fraction is more microbiologically active than the ionized form. A formulation with insufficiently acidic pH may require a higher preservative concentration or a different preservative system.

The main commercial trade-off is between preservative efficacy and patient acceptability. Sodium benzoate can create labeling and perception issues for pediatric products, even when used within accepted limits. A preservative-free unit-dose product could command a premium in neonatal, pediatric, hospital, and specialty-pharmacy channels, but it would require a packaging system that limits microbial exposure after opening.

What formulation patents protect enalapril maleate oral solution?

The relevant patent estate is directed primarily to liquid enalapril formulations and their use, not to the enalapril molecule itself. Public patent records have associated Silvergate Pharmaceuticals with patents covering liquid pharmaceutical compositions containing enalapril maleate, including U.S. Patent No. 8,617,610.

Patent category	Commercial relevance
Liquid enalapril composition	May cover specific excipient combinations, pH ranges, concentrations, and stability profiles
Preserved multidose solution	May cover preservative systems and storage performance
Oral administration method	May cover administration to pediatric or dysphagic patients
Container and dosing system	May provide protection if claimed in continuation or device filings
Manufacturing process	May protect mixing order, pH adjustment, filtration, filling, or stability control

The operative scope depends on the issued claims, terminal disclaimers, maintenance status, reexamination history, continuations, and current Orange Book listing. Patent expiration dates can differ by patent because of priority claims and patent-term adjustment.

What is the Orange Book status of Epaned?

Epaned's Orange Book position should be assessed using the current FDA Orange Book entry for NDA 204708. The commercial questions are:

1. Which patents remain listed?
2. Which claims cover the approved 1 mg/mL solution?
3. Are the patents composition claims, method-of-use claims, or both?
4. Does the proposed product require a Paragraph IV certification?
5. Are any listed patents expired, delisted, or subject to an unexpired pediatric extension?

Because enalapril tablets are generic, a generic applicant seeking approval for an oral solution would not automatically avoid listed liquid-formulation patents. An ANDA applicant would need to address each listed patent through a Paragraph III certification, Paragraph IV certification, or other permitted certification route.

When does enalapril oral solution lose exclusivity?

Molecular exclusivity for enalapril has already expired. The commercially relevant exclusivity is formulation-specific.

The original oral-solution approval did not receive five-year new chemical entity exclusivity because enalapril was previously approved. Any three-year exclusivity associated with new clinical investigations supporting the liquid dosage form has expired. Current barriers therefore depend on patent claims, FDA listing status, product quality, and commercial execution.

Exclusivity layer	Current commercial significance
Enalapril active moiety	Expired
Enalapril tablet patents	Expired or commercially immaterial to a new liquid product
Oral-solution regulatory exclusivity	Expired
Formulation patents	Potentially material if claims remain enforceable
Method-of-use patents	Potentially material, subject to labeling and claim scope
Trade secrets	Relevant to manufacturing and stability control
Trademark and brand	Relevant to market access but not generic exclusion
Pediatric exclusivity	Must be checked in current FDA records; it does not generally restore broad molecule exclusivity

What generic entry risks exist for enalapril maleate oral solution?

The most likely generic entry route is an ANDA for a pharmaceutically equivalent oral solution. The applicant would need to address the reference product's active ingredient, strength, dosage form, route of administration, inactive ingredients, labeling, and listed patents.

A competing liquid could also pursue a 505(b)(2) NDA if it differs materially from Epaned in excipients, concentration, preservative system, packaging, or clinical use. This pathway may be attractive for:

• Preservative-free formulations
• Alternative concentrations
• Improved taste systems
• Unit-dose packaging
• Extended in-use stability
• Products intended for enteral-tube delivery
• Formulations with reduced excipient exposure

How could a Paragraph IV challenge affect the market?

A Paragraph IV filing could trigger patent litigation and a 30-month stay of approval under the Hatch-Waxman framework, subject to the statutory requirements and litigation posture. The commercial impact would depend on:

• The number of listed patents
• Whether claims cover the proposed formulation
• Whether the applicant uses the same excipient system
• The strength of infringement and validity positions
• The availability of a non-infringing formulation
• The willingness of the brand company to settle

A design-around product using a different buffer, preservative, or packaging system may avoid some composition claims but could lose the reference product's stability profile or ease of regulatory bridging.

What excipient strategies create commercial opportunities?

1. Preservative-free unit-dose solution

A preservative-free product packaged in single-use oral syringes or unit-dose ampoules could target neonatal and pediatric hospital use. The value proposition is reduced preservative exposure and lower contamination risk after opening.

The principal development burden is packaging cost, fill accuracy, oxygen control, microbial assurance, and supply-chain complexity. Unit-dose packaging also supports institutional medication-safety programs.

2. Improved pediatric taste profile

Taste is a direct adherence issue for chronic antihypertensive therapy. A competitor could differentiate through:

• Lower bitterness
• Reduced acid perception
• Fruit flavors with stronger masking
• Lower sweetener load
• Dye-free presentation
• Allergen-controlled flavor systems

Flavor changes must be evaluated against active stability, preservative performance, and pediatric acceptability. A highly palatable product may gain formulary preference even without a broad patent barrier.

3. Sugar-free and alcohol-free formulation

A sugar-free formulation supports patients with diabetes and reduces dental-health concerns. An alcohol-free formulation is commercially important in pediatric and institutional settings. Epaned's formulation profile already supports a water-based product, but a differentiated excipient system could strengthen positioning if it provides equivalent stability and taste.

4. Alternative buffer systems

Phosphate, acetate, or other buffer systems could provide a design-around opportunity, but they create technical risks. Buffer choice can affect:

• Enalapril degradation
• Precipitation
• Preservative activity
• Osmolality
• Taste
• Compatibility with enteral feeding tubes

A non-citrate formulation would need a strong stability package to justify the added development and regulatory work.

5. Extended in-use stability

A bottle that remains stable for longer after opening would reduce pharmacy waste and improve adherence. This opportunity is particularly relevant for low-dose pediatric therapy, where a 150 mL bottle may be used over an extended period.

Extended in-use claims require evidence covering chemical stability, microbial control, repeated opening, dosing-device use, temperature excursions, and container closure integrity.

6. Tube-compatible formulation and packaging

A solution optimized for nasogastric and gastrostomy administration could address a defined institutional need. Commercial claims may include:

• Reduced tube adsorption
• Lower clogging risk
• Simple flushing requirements
• Accurate delivery through oral and enteral syringes
• Compatibility with common feeding-tube materials

The formulation should be evaluated with the actual devices used in hospitals. Device compatibility can become a practical differentiator even when it does not produce strong composition patent protection.

How strong is the patent estate for enalapril oral solution?

The patent estate is likely moderate rather than molecule-level strong.

Strength factor	Assessment
Active ingredient protection	Weak or expired
Dosage-form differentiation	Meaningful
Liquid-composition claims	Potentially meaningful
Formulation design-around risk	Moderate to high
Manufacturing know-how	Potentially meaningful
Regulatory barrier to a second solution	Moderate
Biosimilar barrier	None
Brand loyalty	Limited but relevant in pediatrics
Litigation leverage	Dependent on current Orange Book listings and claim breadth

A narrow patent covering a specific citrate, benzoate, pH, or concentration combination may not block a well-designed alternative formulation. Broad claims that capture aqueous enalapril solutions across a meaningful pH and excipient range would create a stronger barrier, but their validity and infringement exposure would require claim-by-claim analysis.

Which companies are positioned to challenge or compete?

The competitive field includes four groups:

1. The branded oral-solution company, currently associated with the Epaned commercial platform.
2. Generic manufacturers with enalapril tablet infrastructure and liquid-development capabilities.
3. Specialty pharmaceutical companies focused on pediatric and complex oral dosage forms.
4. Compounding pharmacies that prepare extemporaneous enalapril liquids.

Generic manufacturers are the most credible long-term price competitors. Specialty companies may compete more effectively through preservative-free packaging, pediatric taste, or hospital distribution. Compounding pharmacies remain relevant where the commercial product is unavailable, expensive, or not stocked.

What licensing and partnering opportunities exist?

Licensing value is highest in the following assets:

• A stable preservative-free formulation
• A formulation with long in-use shelf life
• A pediatric taste-masking platform
• Tube-compatible packaging
• A validated low-cost manufacturing process
• A formulation with a clearly non-infringing excipient profile
• Regional rights in markets where an approved liquid is unavailable

Potential partners include pediatric specialty companies, generic manufacturers, hospital-focused pharmaceutical suppliers, and companies with oral-liquid manufacturing capacity.

A formulation owner should protect the asset through composition claims, pH and stability claims where supportable, process claims, packaging claims, and use claims. Trade-secret protection is particularly important for mixing order, pH adjustment, filtration, deaeration, and preservative incorporation.

What revenue exposure does generic entry create?

Epaned's exposure is concentrated in a narrow market rather than the entire enalapril market. Generic entry into tablets does not eliminate the value of the oral solution because many patients cannot reliably use tablets.

Market segment	Generic-entry sensitivity
Adult patients able to swallow tablets	High
Pediatric patients requiring liquid dosing	Moderate
Patients with dysphagia	Moderate
Enteral-tube users	Moderate
Hospital and specialty pharmacy accounts	Moderate to high
Preservative-sensitive or formulation-sensitive patients	Lower
Compounding-dependent patients	Depends on local availability and price

A lower-cost generic solution could pressure price and formulary access. A differentiated product with superior taste, packaging, or stability could retain premium pricing.

How does enalapril oral solution compare with other liquid ACE inhibitors?

Product attribute	Enalapril maleate oral solution	Lisinopril oral solution	Captopril liquid
ACE inhibitor	Enalapril	Lisinopril	Captopril
Pediatric liquid availability	Established branded product	Market availability varies by jurisdiction	Often compounded
Stability challenge	Aqueous degradation and preservative control	Formulation and taste control	High sensitivity to stability and taste
Commercial differentiation	Flavor, preservative, packaging, tube use	Availability and dosing convenience	Stability and compounding replacement
Patent opportunity	Liquid formulation and process	Product-specific	Formulation and packaging
Main clinical barrier	Accurate chronic liquid dosing	Product availability	Shorter stability and poor palatability in some formulations

Enalapril oral solution has a stronger commercial position when the buyer values an FDA-approved product over compounding. Its main advantage is standardized quality and labeling, not molecule exclusivity.

What manufacturing and intellectual-property barriers matter?

The most important manufacturing barriers are reproducible pH control, low degradation, preservative uniformity, microbial control, flavor consistency, and fill accuracy. Liquid products also create higher risk of extractables and leachables, container-closure failures, and dosing-device variability than tablets.

A competitive manufacturer should validate:

• Raw-material variability in enalapril maleate
• Order of excipient addition
• Mixing and deaeration
• pH adjustment and hold time
• Filtration or microbial-control strategy
• Bottle and closure compatibility
• Oral-syringe accuracy
• In-use stability
• Temperature-excursion performance
• Shipping and light exposure

Geographic protection depends on national patent filings, regulatory approvals, trademarks, and manufacturing rights. U.S. formulation patents do not automatically block sales in Europe, Japan, Canada, or emerging markets. Local patent families and country-specific regulatory pathways require separate review.

Key Takeaways

• Enalapril maleate oral solution is an established FDA-approved liquid product, with Epaned as the principal U.S. reference.
• The active ingredient is off-patent; commercial protection depends on formulation, process, packaging, trademarks, and regulatory execution.
• Citrate buffering and sodium benzoate preservation are central formulation elements.
• The strongest commercial opportunities are preservative-free unit doses, improved pediatric taste, sugar-free and alcohol-free systems, longer in-use stability, and enteral-tube compatibility.
• Generic entry is possible through an ANDA or, for materially differentiated products, a 505(b)(2) NDA.
• A Paragraph IV strategy must address current Orange Book listings and the precise scope of liquid-formulation claims.
• Biosimilar competition is irrelevant because enalapril is a small molecule.
• The best licensing assets combine formulation stability, pediatric usability, packaging differentiation, and a defensible non-infringing patent position.

FAQs

Is enalapril maleate oral solution available as a generic?

Generic enalapril tablets are widely available, but a generic oral solution requires separate regulatory approval and patent certification. Availability depends on current FDA approvals and commercial launches.

Can enalapril oral solution be made without sodium benzoate?

Yes, a preservative-free product can be developed if the packaging and manufacturing system provide adequate microbial control. Unit-dose packaging is the most practical commercial approach.

What is the most valuable excipient innovation for pediatric enalapril?

Taste masking combined with stable buffering is likely the highest-value innovation because it directly affects adherence without requiring a new active ingredient.

Can an enalapril oral solution be administered through a feeding tube?

A solution may be suitable for enteral administration, but tube compatibility, dosing accuracy, flushing requirements, and adsorption must be validated for the intended device and concentration.

Does enalapril oral solution have biosimilar risk?

No. Enalapril is a small-molecule drug. Competitive risk comes from generic oral solutions, 505(b)(2) products, compounding pharmacies, and alternative ACE-inhibitor liquids.

References

1. U.S. Food and Drug Administration. (2013). Epaned (enalapril maleate) oral solution prescribing information. Silvergate Pharmaceuticals.

2. U.S. Food and Drug Administration. (n.d.). Drugs@FDA: Epaned, NDA 204708. https://www.accessdata.fda.gov/scripts/cder/daf/

3. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book

4. U.S. Patent No. 8,617,610. (2013). Liquid pharmaceutical compositions of enalapril maleate. U.S. Patent and Trademark Office.

5. U.S. Food and Drug Administration. (2019). Abbreviated new drug application regulations and patent certification requirements. https://www.fda.gov/drugs

6. U.S. Food and Drug Administration. (2022). Inactive ingredient database. https://www.accessdata.fda.gov/scripts/sda/sdNavigation.cfm?sd=inactiveIngredientDatabase