List of Excipients in Branded Drug ACYCLOVIR SUSPENSION

Generic Drugs Containing ACYCLOVIR SUSPENSION

Company	Ingredient	NDC	Excipient
Atlantic Biologicals Corp	acyclovir	17856-2170	CARBOXYMETHYLCELLULOSE SODIUM
Atlantic Biologicals Corp	acyclovir	17856-2170	CELLULOSE, MICROCRYSTALLINE
Atlantic Biologicals Corp	acyclovir	17856-2170	GLYCERIN
Atlantic Biologicals Corp	acyclovir	17856-2170	METHYLPARABEN
Atlantic Biologicals Corp	acyclovir	17856-2170	PROPYLPARABEN

What are the Most Frequently-Used Excipients in ACYCLOVIR SUSPENSION?

# Of NDCs	Excipient
2	CARBOXYMETHYLCELLULOSE SODIUM
2	CELLULOSE, MICROCRYSTALLINE
2	GLYCERIN
2	METHYLPARABEN
2	PROPYLPARABEN

Acyclovir Suspension Excipient Strategy and Commercial Opportunities

Last updated: September 24, 2026

Acyclovir oral suspension is an established generic dosage form with limited active-ingredient patent risk and meaningful formulation opportunities. The commercial case depends on improving taste, dose accuracy, physical stability, preservative strategy, and access for pediatric and dysphagic patients. A 200 mg/5 mL suspension delivers 40 mg/mL, a concentration that generally requires a well-designed suspension rather than a simple aqueous solution because acyclovir has limited water solubility at near-neutral pH.[1][2]

What is the commercial opportunity for acyclovir oral suspension?

Acyclovir suspension addresses patients who cannot reliably swallow tablets or capsules. The principal demand segments are children, older adults, patients with neurologic or oncologic conditions, and patients requiring liquid administration through feeding tubes.

Acyclovir is indicated for herpes simplex virus infections, varicella-zoster virus infections, and related prophylactic uses. Oral bioavailability is limited, generally reported at approximately 10% to 20%, so dose uniformity and administration accuracy are important commercial attributes.[1]

Commercial factor	Implication
Active ingredient	Acyclovir, an established antiviral
Common liquid strength	200 mg/5 mL
Primary users	Pediatric, geriatric, dysphagic and tube-fed patients
Dosage-form challenge	Poor aqueous solubility and sedimentation control
Main differentiation levers	Taste, redispersibility, dosing device, sugar-free design and preservative system
Patent risk	Low for the active ingredient; formulation-specific risk depends on the product
Regulatory route	Abbreviated New Drug Application for a therapeutically equivalent generic, where applicable
Commercial competitors	Generic oral suspensions, tablets, capsules and extemporaneously compounded liquids

The largest opportunity is not a new acyclovir molecule. It is a better liquid product with lower administration friction and lower pharmacy-compounding burden.

What excipients are used in acyclovir suspension?

Commercial acyclovir suspensions commonly use a combination of a sweetener, suspending polymer, wetting or dispersion aid, preservative, flavor and purified water. The exact composition depends on the manufacturer and approved product label.

Typical excipient classes include:

Excipient class	Examples	Function
Vehicle	Purified water	Continuous phase
Sweetener	Sucrose, sorbitol, sucralose or other approved sweetener	Taste masking and mouthfeel
Suspending agent	Sodium carboxymethylcellulose, microcrystalline cellulose blends, xanthan gum or similar polymers	Controls sedimentation and supports redispersion
Wetting agent	Polysorbate or other pharmaceutically acceptable surfactant	Improves particle wetting
Preservative	Methylparaben, propylparaben, sodium benzoate or another suitable system	Controls microbial growth
Flavor	Fruit, berry or other pediatric flavor	Reduces bitterness
Buffer or pH adjuster	Citrate, phosphate or other approved system	Controls pH and preservative performance
Antifoam or processing aid	Product-specific	Limits foam and manufacturing variability

Acyclovir suspension labels should be treated as product-specific documents. Excipients, strengths, storage instructions and beyond-use conditions can differ between marketed products and pharmacy-prepared formulations.[2][3]

Why acyclovir requires a suspension design

Acyclovir has limited solubility in water. At a 40 mg/mL target concentration, the formulation generally depends on dispersed drug particles. This creates several quality risks:

• sediment formation during storage;
• hard cake formation that prevents redispersion;
• dose nonuniformity between the first and last doses;
• poor wetting and floating particles;
• mouthfeel from undissolved drug;
• viscosity that is too high for oral syringes or feeding tubes;
• microbial growth in a water-based product.

The formulation target is not maximum viscosity. It is controlled sedimentation with rapid, reproducible redispersion and acceptable syringeability.

What is the best excipient strategy for acyclovir suspension?

The strongest formulation strategy is a low-sugar or sugar-free, well-redispersible suspension with validated dosing performance and a flavor system designed for children.

Suspending system

A structured vehicle based on sodium carboxymethylcellulose, xanthan gum, microcrystalline cellulose or a combination can reduce sedimentation. A polymer blend is often more useful than a single polymer because it can balance yield stress, pourability and syringe delivery.

Key development targets include:

• no irreversible caking;
• uniform dose after the labeled shaking instruction;
• acceptable viscosity across the intended storage range;
• consistent delivery through oral syringes;
• compatibility with enteral feeding tubes;
• no significant change in particle size during storage.

Excessive viscosity creates a commercial disadvantage. Caregivers may underdose a product that is difficult to pour or withdraw, while tube-fed patients may face clogging risk.

Wetting and dispersion

Acyclovir particles must be wetted consistently during manufacturing. Poor wetting can cause floating material, agglomeration and variable dose delivery. A surfactant can help, but its level should remain low enough to avoid foaming, unpleasant mouthfeel and gastrointestinal intolerance.

Particle engineering may provide a better solution than higher surfactant loading. Controlled milling, narrow particle-size distribution and appropriate wetting procedures can improve physical stability without adding a complex excipient system.

Taste masking

Acyclovir can produce a bitter or unpleasant taste. Flavor alone may not adequately address the problem because the drug is present as dispersed solid particles and may remain in the mouth after swallowing.

Taste-masking options include:

1. high-intensity sweeteners combined with bulk sweeteners;
2. polymeric coating of drug particles;
3. ion-pairing or complexation approaches;
4. flavor layering;
5. pH adjustment where compatible with stability and tolerability.

For pediatric use, a fruit flavor with moderate sweetness and low lingering aftertaste is usually more practical than a highly concentrated flavor system. Taste panels should assess the formulation after shaking and after realistic oral residence times.

Sugar-free design

A sugar-free formulation expands use among patients with diabetes, dental disease or long treatment courses. Sorbitol, glycerin and selected high-intensity sweeteners can replace sucrose, but each creates tradeoffs.

Sorbitol can increase osmolality and cause gastrointestinal effects at higher exposure. Glycerin can alter mouthfeel and viscosity. Sucralose or similar sweeteners can improve sweetness at low concentration but may not provide enough body without a separate vehicle modifier.

A sugar-free product can have stronger commercial positioning than a conventional sucrose suspension, provided it maintains acceptable taste and does not create tube-administration problems.

What formulations are protected by acyclovir suspension patents?

Acyclovir’s original compound and core antiviral use patents are long expired in the United States. The main intellectual-property opportunity lies in formulation, manufacturing and delivery claims rather than the active ingredient.

Potentially protectable subject matter includes:

• particle-size-controlled acyclovir;
• taste-masked acyclovir particles;
• high-concentration aqueous suspensions;
• sugar-free formulations;
• preservative-free multidose systems;
• improved redispersibility;
• oral-syringe or feeding-tube compatibility;
• extended physical stability;
• specific polymer combinations;
• manufacturing processes that reduce agglomeration;
• low-foam filling and packaging systems.

A formulation patent must provide more than a routine substitution of one excipient for another. Commercially useful claims are more likely to require measurable performance, such as a defined sedimentation profile, redispersion time, dissolution behavior, particle-size range or stability result.

Patent searches should cover the exact combination of acyclovir, concentration, excipients and dosage form. A broad search for “acyclovir suspension” may identify expired patents, abandoned applications, formulation patents with narrow claims and unrelated veterinary or topical products.

When does acyclovir lose exclusivity?

Acyclovir has already lost small-molecule market exclusivity in major markets. Generic tablets, capsules and liquid products have been available for many years. The relevant commercial question is therefore not loss of basic acyclovir exclusivity, but whether a specific suspension product has remaining regulatory or formulation protection.

Exclusivity category	Current commercial relevance
Original compound patent	Expired
Original oral antiviral indications	No meaningful exclusivity barrier
Generic tablet and capsule entry	Established
Generic oral suspension entry	Established or product-specific depending on jurisdiction
New formulation patent	Possible if claims are narrow and valid
Orphan exclusivity	Generally not the basis for standard acyclovir suspension
Pediatric exclusivity	Historical or product-specific, not a current barrier to the established molecule

The FDA Orange Book should be checked for the relevant reference-listed drug, approved strengths and any listed patents or exclusivity codes.[4] A product-level conclusion requires review of the exact National Drug Code, application number and jurisdiction.

What is the FDA regulatory status of acyclovir suspension?

Acyclovir oral suspension is regulated as a prescription drug in the United States. An abbreviated generic product generally must demonstrate pharmaceutical equivalence and bioequivalence or satisfy an FDA-accepted alternative standard, depending on the dosage form and reference product.

The principal regulatory risks are formulation-specific:

• inadequate dose uniformity;
• poor redispersion after storage;
• dissolution differences caused by particle size;
• preservative failure;
• microbial contamination;
• unacceptable impurities or degradation;
• excipient differences that affect safety or performance;
• failure of the proposed measuring device to deliver accurate doses.

For a suspension, physical characterization is central. Development packages generally require sedimentation, redispersion, particle-size, viscosity, pH, assay, content uniformity, dissolution and microbial quality data. Packaging studies should test the marketed bottle, closure, oral syringe and dosing adapter as a complete system.

How strong is the patent estate for acyclovir suspension?

The patent estate for conventional acyclovir suspension is generally weak because the active ingredient is old and the core dosage form is familiar. A new entrant may still obtain protection for a differentiated formulation, but the scope is likely to be narrow.

Patent-strength assessment

Asset type	Likely strength	Commercial value
Acyclovir compound patent	None as current barrier	Low
Conventional 200 mg/5 mL suspension	Low	Low to moderate
Specific polymer combination	Low to moderate	Moderate
Sugar-free and taste-masked formulation	Moderate if supported by data	Moderate to high
Preservative-free multidose system	Moderate to high if technically validated	High
Tube-compatible formulation	Moderate	Moderate
Novel particle engineering	Moderate to high	High if difficult to design around
Packaging-only claims	Low to moderate	Selective

Patent strength depends on claim breadth, prosecution history, enablement, unexpected results and the availability of non-infringing excipient substitutions. A competitor can often design around a narrow excipient claim by changing the polymer, sweetener, preservative or particle-size range.

Which companies are challenging acyclovir suspension products?

Acyclovir is a mature generic market, so competition typically comes from generic manufacturers, contract development and manufacturing organizations, pharmacy compounders and alternative dosage forms rather than named patent challengers.

Paragraph IV litigation is most relevant when a company files an ANDA against a product with listed formulation or method-of-use patents. For an established acyclovir suspension, the practical challenge is more likely to involve ordinary generic registration, manufacturing scale-up and commercial contracting than high-value patent litigation.

The competitive set includes:

• manufacturers of acyclovir oral suspension;
• tablet and capsule suppliers;
• compounding pharmacies;
• hospital pharmacies;
• specialty pharmacies serving pediatric patients;
• manufacturers of related antiviral liquids, including valacyclovir alternatives where clinically appropriate.

No reliable conclusion about current challengers, settlements or active litigation should be drawn without a current PACER, FDA Orange Book and regulatory-label review. Historical acyclovir product litigation does not automatically apply to a current suspension product.

What generic launch risks exist for acyclovir suspension?

A generic launch can occur without an active compound patent barrier, but operational risks remain.

Manufacturing and IP barriers

The key technical barriers are:

• uniform suspension manufacturing at commercial scale;
• control of acyclovir particle size;
• acceptable taste without excessive sweetener;
• preservative efficacy throughout shelf life;
• stable redispersion after temperature cycling;
• compatibility with bottle, cap and dosing syringe;
• prevention of tube clogging;
• supply of pharmaceutically acceptable excipients;
• avoidance of a competitor’s valid formulation claims.

The most defensible product may combine a formulation patent with manufacturing know-how. Trade secrets can protect order of addition, shear conditions, milling parameters, deaeration and filling controls even when the public patent estate is limited.

Launch scenarios

Scenario	Likely outcome
Conventional sugar-containing suspension	Fastest development, heavy price competition
Sugar-free suspension	Better differentiation, higher formulation burden
Taste-masked pediatric product	Potential premium positioning if clinical acceptability is demonstrated
Preservative-free unit-dose product	Higher packaging cost, potential institutional value
Tube-optimized suspension	Niche opportunity in hospitals and long-term care
Dual-strength portfolio	Better fit for pediatric and adult dosing, more regulatory work
Compounding-focused product	Opportunity to replace pharmacy preparation with standardized quality

How does acyclovir suspension compare with acyclovir tablets and valacyclovir?

Attribute	Acyclovir suspension	Acyclovir tablets	Valacyclovir tablets
Administration	Useful for patients unable to swallow	Simple for most adults	Simple for most adults
Bioavailability	Low to moderate	Low to moderate	Higher than acyclovir
Dosing frequency	Often frequent	Often frequent	Generally less frequent in many indications
Formulation complexity	High	Lower	Lower for solid dosage forms
Pediatric flexibility	High	Limited by swallowing and dose strength	Product- and indication-dependent
Cost position	Generic, but liquid manufacturing costs more	Usually low	Often higher than acyclovir
Commercial differentiation	Taste, device and stability	Price and availability	Convenience and dosing frequency

Suspension demand persists because pharmacokinetic advantages do not eliminate the need for a swallowable liquid. A liquid product can compete on access and administration rather than on lower dosing frequency.

What licensing deals and partnerships are relevant?

The most realistic partnership models are formulation licensing, contract manufacturing, private-label supply and hospital-channel distribution. A licensee with a differentiated suspension may seek a partner that already has:

• an approved generic filing platform;
• pediatric commercial relationships;
• a validated oral-liquid manufacturing site;
• access to hospital and long-term-care purchasing groups;
• established pharmacovigilance and quality systems.

Acyclovir suspension does not generally support the economics of a large upfront licensing transaction unless the formulation has a defensible technical advantage, a regulated-market approval or a broader platform applicable to other poorly soluble drugs.

What revenue exposure can an acyclovir suspension generate?

Revenue depends on country, reimbursement, competition, strength, packaging, channel mix and supply reliability. Public financial reports generally do not isolate acyclovir suspension revenue from broader generic or antiviral portfolios.

The principal revenue pools are:

• retail prescriptions;
• pediatric and family-practice prescribing;
• hospital discharge prescriptions;
• long-term-care facilities;
• specialty and mail-order pharmacies;
• institutional unit-dose supply;
• international markets with limited access to reliable oral liquids.

A conventional product is likely to face rapid price erosion. A differentiated sugar-free, taste-masked or tube-compatible product can support better retention and potentially higher gross margin, but the addressable market is narrower.

What is the commercial strategy for a new acyclovir suspension?

The strongest development sequence is:

1. Build a conventional reference-compatible formulation.
2. Establish particle-size and redispersion targets.
3. Develop a sugar-free option in parallel.
4. Conduct taste and dosing-device testing with pediatric-use considerations.
5. Test feeding-tube administration.
6. Evaluate preservative-free or unit-dose packaging only if the channel supports the added cost.
7. Protect measurable formulation and manufacturing advantages.
8. Position the product around reliable dosing, not only price.

A product with the best commercial prospects is likely to combine sugar-free taste masking, rapid redispersion, an oral syringe, a bottle adapter and validated tube compatibility. A conventional sucrose suspension remains the lowest-risk entry but has limited differentiation.

Key Takeaways

• Acyclovir suspension is a mature generic opportunity with low active-ingredient patent risk.
• The main technical problem is a stable, palatable and accurately dosed suspension at approximately 40 mg/mL.
• Excipients should be selected around redispersion, taste, viscosity, preservative performance and device compatibility.
• Sugar-free, taste-masked and tube-compatible products offer the clearest differentiation.
• Formulation patents are possible but are likely to be narrow and vulnerable to design-around strategies.
• A conventional product will face strong price competition and limited revenue visibility.
• Commercial value is highest where the formulation replaces pharmacy compounding or solves pediatric and enteral-administration problems.
• FDA Orange Book, product labeling, patent records and current litigation databases must be reviewed for any product-specific launch decision.[2][4]

FAQs

Is acyclovir suspension a solution or a suspension?

It is generally a suspension because the target concentration can exceed the drug’s practical aqueous solubility under common formulation conditions. Undissolved acyclovir particles are dispersed through the vehicle.

Can acyclovir suspension be made sugar-free?

Yes. Sugar-free systems can use combinations of high-intensity sweeteners, polyols and viscosity modifiers. The formulation must be evaluated for taste, osmolality, microbial control and redispersion.

Which excipient is most important for acyclovir suspension stability?

No single excipient determines performance. The suspending-agent system, particle-size distribution, wetting process and vehicle viscosity work together to control sedimentation and dose uniformity.

Is acyclovir suspension suitable for feeding tubes?

It may be suitable, but tube compatibility must be demonstrated for the specific formulation, tube material and administration method. Viscosity, particle size and residue can affect performance.

Can a new acyclovir suspension receive patent protection?

Yes, but protection would generally need to cover a novel formulation, particle-engineering method, delivery system or measurable stability and performance advantage. The basic acyclovir molecule and conventional suspension concept are not strong current barriers.

References

1. U.S. Food and Drug Administration. (2023). Acyclovir prescribing information. FDA.
2. DailyMed. (2024). Acyclovir oral suspension: Product labeling and inactive ingredients. National Library of Medicine.
3. United States Pharmacopeia. (2024). General chapter <795>: Pharmaceutical compounding, nonsterile preparations. United States Pharmacopeial Convention.
4. U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations, Orange Book. FDA.