List of Excipients in Branded Drug PROBENECID

Generic Drugs Containing PROBENECID

Company	Ingredient	NDC	Excipient
Mylan Pharmaceuticals Inc	probenecid	0378-0156	CELLULOSE, MICROCRYSTALLINE
Mylan Pharmaceuticals Inc	probenecid	0378-0156	D&C YELLOW NO. 10
Mylan Pharmaceuticals Inc	probenecid	0378-0156	FD&C BLUE NO. 2
Mylan Pharmaceuticals Inc	probenecid	0378-0156	FD&C YELLOW NO. 6
Mylan Pharmaceuticals Inc	probenecid	0378-0156	HYPROMELLOSE
Mylan Pharmaceuticals Inc	probenecid	0378-0156	MAGNESIUM STEARATE
Mylan Pharmaceuticals Inc	probenecid	0378-0156	POLYDEXTROSE

What are the Most Frequently-Used Excipients in PROBENECID?

# Of NDCs	Excipient
7	ALUMINUM OXIDE
15	CELLULOSE, MICROCRYSTALLINE
17	D&C YELLOW NO. 10
1	D&C YELLOW NO. 10 ALUMINUM LAKE
4	FD&C BLUE NO. 1
1	FD&C BLUE NO. 1 ALUMINUM LAKE
13	FD&C BLUE NO. 2

Probenecid Excipient Strategy and Commercial Opportunities

Last updated: August 29, 2026

Probenecid is an established, low-cost oral uricosuric drug with no meaningful new-molecule exclusivity in the United States. The strongest commercial opportunities are formulation improvements, particularly pH-controlled dissolution, lower pill burden, liquid or dispersible dosage forms, and differentiated products for patients with swallowing or adherence problems. Commodity excipients alone are unlikely to support premium pricing; value depends on a measurable clinical, manufacturing, or regulatory advantage.

What is the current FDA status of probenecid?

Probenecid is an FDA-approved oral drug used to reduce serum uric acid in gout and gouty arthritis and to increase plasma concentrations of certain beta-lactam antibiotics by reducing renal tubular secretion (FDA, 2023a).

Attribute	Current position
Active ingredient	Probenecid
Primary use	Chronic gout and hyperuricemia; adjunctive use with selected penicillins and cephalosporins
Common dosage form	Immediate-release oral tablet
Common strength	500 mg
Typical adult maintenance dosing	500 mg twice daily, titrated according to response and tolerability
Regulatory pathway for new products	ANDA for equivalent generic products; 505(b)(2) for differentiated formulations or new clinical uses
Biologic status	Not applicable
Biosimilar exposure	None
New-molecule exclusivity	Expired
Brand position	Probenecid is primarily a generic market
Orange Book significance	Any listed patents or exclusivities must be verified against the current FDA Orange Book

The FDA label identifies important safety and formulation constraints, including uric-acid stone risk, interaction with salicylates, renal function considerations, and the need for adequate hydration (FDA, 2023a). These factors limit the commercial value of a formulation that improves absorption without addressing tolerability or adherence.

What excipients are used in probenecid tablets?

Public product information for probenecid tablets shows conventional immediate-release excipient systems. Depending on the manufacturer, tablets may contain lactose, starch, povidone, talc, magnesium stearate, colloidal silicon dioxide, sodium starch glycolate, or related conventional materials. The exact composition varies by ANDA holder and product presentation.

The FDA Inactive Ingredient Database should be used to confirm route-specific precedent, maximum daily exposure, and dosage-form use before selecting an excipient for a new product (FDA, 2024a). Prior use in another oral tablet does not automatically establish acceptability for a new strength, pediatric formulation, liquid, or modified-release product.

What technical properties drive excipient selection?

Probenecid has limited aqueous solubility and pH-dependent ionization. Its weak-acid behavior creates a formulation risk: dissolution may be adequate in one gastrointestinal environment but slower in another. Drug properties reported in public chemical databases include low water solubility and an acidic carboxyl group, making pH control and particle engineering relevant to product design (National Center for Biotechnology Information, 2024).

The key excipient objectives are:

1. Improve dissolution without increasing systemic exposure beyond the approved clinical range.
2. Preserve tablet hardness and disintegration after compression.
3. Control hygroscopicity and physical stability.
4. Reduce variability caused by particle size and polymorphic form.
5. Avoid excipient-related gastrointestinal effects in a drug already associated with gastrointestinal intolerance.

What excipient strategies could improve probenecid performance?

pH-modified immediate-release tablets

A pH-modified formulation is the most defensible first-line strategy. Alkalinizing agents or buffering systems could improve dissolution of the weak-acid drug in aqueous media. Candidate classes include carbonate or bicarbonate buffers, citrate systems, and other pharmaceutically acceptable pH modifiers.

The main development risks are:

• Excessive local alkalinity in the stomach.
• Faster dissolution that increases peak concentration or adverse effects.
• Buffer capacity that changes tablet stability.
• Interaction with acid-sensitive excipients.
• Inconsistent performance after meals or with gastric-acid-reducing medicines.

A pH-modified tablet would need comparative dissolution across physiologically relevant pH conditions, food-effect assessment, and pharmacokinetic comparison with a reference product.

Particle-size reduction and wetting systems

Micronized or narrowly distributed probenecid particles could reduce dissolution variability. Surfactants and wetting agents may improve media penetration, while superdisintegrants can shorten tablet breakup time.

This approach is technically simple but commercially weak unless it produces a clear benefit. A generic tablet that dissolves faster in vitro may not qualify for a premium product without evidence of improved exposure consistency, adherence, or clinical performance.

Amorphous solid dispersion

An amorphous solid dispersion using polymers such as povidone, copovidone, or hydroxypropyl cellulose could increase apparent solubility. The principal risk is recrystallization during storage. A successful program would require:

• Solid-state characterization.
• Moisture-sorption studies.
• Long-term and accelerated stability.
• Supersaturation and precipitation testing.
• Packaging assessment.
• Demonstration that the formulation remains manufacturable at a 500 mg drug load.

Because probenecid is an old, relatively inexpensive active, the cost and complexity of an amorphous dispersion may exceed the value of the product unless the formulation targets a specific unmet need.

Lipid-based or self-emulsifying systems

Lipid-based systems are less attractive for a routine probenecid tablet. They may improve apparent solubilization but can create manufacturing, capsule-fill, food-effect, and stability problems. The approach is more relevant if a development program demonstrates substantial absorption variability that cannot be managed with conventional pH or particle engineering.

Taste-masked granules and dispersible products

A taste-masked granule, oral powder, or dispersible tablet could address swallowing difficulty and administration through selected enteral feeding systems. Taste masking may require polymer coating, ion-exchange resin complexes, or a multiparticulate approach.

This opportunity is commercially relevant because the approved label permits use in children older than two years in certain circumstances, but pediatric development would require age-appropriate dosing, palatability data, dosing-device validation, and a clinical rationale for the new presentation (FDA, 2023a).

A liquid suspension may be more practical than a solution because probenecid’s solubility limits a high-concentration aqueous product. Suspending agents, wetting agents, buffers, preservatives, and container-closure selection would become central development issues.

What formulations are protected by probenecid patents?

Probenecid’s original compound protection and early pharmaceutical patents expired long ago. The commercial market is dominated by generic products, and there is no established market position comparable to a branded drug with active compound, formulation, and method-of-use patents.

Patent category	Commercial assessment
Original compound patent	Expired
Basic tablet formulation	Generally vulnerable to generic competition and prior-art challenges
New excipient combination	Potentially patentable, but obviousness risk is high
pH-modified formulation	Possible composition or use claims if supported by unexpected results
Amorphous or crystalline form	Potential protection if a distinct, stable form is demonstrated
Pediatric liquid or dispersible product	Potential formulation and method-of-use protection
Modified release	Possible, but clinical and technical justification is difficult
Manufacturing process	Trade-secret protection may be more practical than patent protection
Method of use for transporter inhibition	Potentially protectable only with credible new clinical evidence

A new patent estate would need to protect more than the use of a familiar excipient in a conventional tablet. Stronger claim positions could include a defined solid form, a quantified dissolution profile tied to pharmacokinetic performance, a specific excipient ratio, a stability advantage, or a clinically meaningful reduction in dosing burden.

When does probenecid lose exclusivity?

Probenecid has already lost new-molecule exclusivity and is commercially generic. The relevant protection question is not loss of the original exclusivity period but whether a developer can obtain new, enforceable protection for a differentiated product.

The regulatory pathway determines the practical timing:

• An ANDA product competes on pharmaceutical equivalence and bioequivalence.
• A 505(b)(2) product can rely partly on existing findings while seeking approval for a new dosage form, formulation, dosing regimen, or other modification.
• A new clinical use may require additional clinical evidence and a method-of-use strategy.
• A new product patent does not automatically block all generic probenecid tablets.

FDA approval of a 505(b)(2) formulation could create three-year clinical investigation exclusivity for certain changes supported by new investigations, but this protection is narrower than new chemical entity exclusivity and does not prevent all forms of competition (FDA, 2019).

How many patents cover probenecid?

The number of historically issued probenecid patents is less important than the number of unexpired, enforceable claims covering the specific product. For the conventional active ingredient and immediate-release tablet, the commercial patent barrier is low.

A current Orange Book review is required for product-specific listed patents, pediatric exclusivity, and any approved reference-listed drug claims. The Orange Book identifies patents submitted by approved applicants for approved drug products, but it does not function as a complete worldwide patent database (FDA, 2024b).

Are Paragraph IV challenges relevant?

Paragraph IV litigation is unlikely to be a major barrier for ordinary probenecid tablets because the active ingredient is old and generic competition is established. A Paragraph IV strategy could become relevant if a new branded probenecid formulation obtains Orange Book-listed patents, such as:

• A controlled-release tablet.
• A protected liquid or multiparticulate dosage form.
• A defined solid-state form.
• A clinically supported combination product.
• A formulation with a specific dissolution or pharmacokinetic profile.

No broad, commercially significant Paragraph IV dispute should be assumed without reviewing current ANDA certifications, FDA listing data, and federal court dockets.

What generic entry risks exist for a new probenecid formulation?

Generic entry risk is high for products that rely on conventional excipients and low for products with technically difficult, clinically differentiated delivery systems, although no formulation is immune to competition.

Product concept	Generic entry risk	Main barrier
Conventional 500 mg tablet	Very high	Established generic manufacturing
Improved-disintegration tablet	Very high	Common excipient technology
pH-modified tablet	High	Straightforward formulation replication
Micronized tablet	High to medium	Particle specification and process control
Amorphous dispersion	Medium	Solid-state stability and manufacturing know-how
Pediatric suspension	Medium	Palatability, stability, dosing device, and clinical validation
Modified-release tablet	Medium to low	Complex dissolution and bioequivalence requirements
Combination product	Medium	Clinical, patent, and regulatory complexity
Novel transporter-inhibitor use	Variable	Dependence on clinical evidence and method-of-use claims

Manufacturing barriers are more credible when they involve a narrow particle-size distribution, controlled polymorphism, validated dispersion process, specialized coating, or a formulation-dependent dissolution profile. A patent that claims only a broad list of standard excipients is vulnerable to invalidity and design-around arguments.

Which commercial opportunities are strongest?

1. Pediatric and swallowing-friendly products

An oral suspension, powder for reconstitution, dispersible tablet, or coated granule could reach patients who cannot reliably use a conventional tablet. The commercial opportunity depends on whether the market supports a higher price for convenience and whether the product can demonstrate acceptable palatability and dose accuracy.

2. Lower-pill-burden products

The standard 500 mg tablet can require twice-daily dosing and, during titration, multiple tablets. A higher-strength or modified-release product could reduce pill burden. The dose range and safety profile constrain this opportunity, and a larger tablet may create new swallowing problems.

3. Stable liquid formulations

A shelf-stable suspension would have potential in pediatric, geriatric, and institutional markets. The key technical requirements are uniformity after shaking, sedimentation control, microbial protection, acceptable taste, and a suitable measuring device.

4. Transporter-inhibition applications

Probenecid inhibits renal organic anion transport and has historically been used to alter the pharmacokinetics of beta-lactam antibiotics. A modern coadministration strategy could have value where extending antibiotic exposure reduces dosing frequency or improves outpatient administration. The opportunity carries substantial interaction, antimicrobial stewardship, clinical-trial, and regulatory risk. It should not be treated as a simple excipient-led lifecycle extension.

5. Contract development and manufacturing

Because probenecid is an established generic active, a contract manufacturer could create value through formulation platforms rather than proprietary excipients. Services could include:

• pH-dependent dissolution optimization.
• Tablet compression and scale-up.
• Pediatric liquid development.
• Multiparticulate coating.
• Solid-state screening.
• Bioequivalence-enabling formulation work.
• Stability and packaging optimization.

The buyer would usually value speed, reproducibility, and regulatory execution more than exclusivity in the excipient itself.

How does probenecid compare with competing gout medicines?

Probenecid competes with xanthine oxidase inhibitors such as allopurinol and febuxostat. These drugs reduce uric-acid production, while probenecid increases renal uric-acid excretion. Allopurinol has broad generic availability and a larger prescribing base. Febuxostat has a branded and generic history, with differentiated cardiovascular safety considerations.

Drug	Pharmacologic approach	Formulation opportunity	Commercial implication
Probenecid	Uricosuric; increases renal uric-acid excretion	Pediatric, liquid, dispersible, modified release	Niche product opportunity
Allopurinol	Xanthine oxidase inhibition	Broad generic competition	Low formulation premium
Febuxostat	Selective xanthine oxidase inhibition	Brand and generic lifecycle activity	Greater commercial value but higher competition
Lesinurad	Uricosuric adjunct	Limited market opportunity after commercial withdrawal in several markets	Weak comparator for new investment

Probenecid’s main competitive weakness is that renal function, nephrolithiasis risk, hydration requirements, and drug interactions can limit use. A formulation program that only improves tablet dissolution will not resolve these clinical constraints.

What is the revenue exposure for probenecid products?

Revenue exposure is generally modest relative to major gout therapies because probenecid is an old generic drug with multiple suppliers. Public company disclosures rarely report probenecid revenue as a separate material line item. Market value is concentrated in:

• Institutional and generic supply contracts.
• Shortages or discontinuations among competing manufacturers.
• Specialized pediatric or liquid products.
• Hospital use where transporter-mediated drug exposure has operational value.
• Regional markets with limited generic competition.

A differentiated formulation could support a higher net price, but the addressable patient population is smaller than for allopurinol. Commercial diligence should prioritize prescription volume, reimbursement, competitor availability, and manufacturer concentration rather than assuming branded-gout economics.

What is the recommended excipient development strategy?

The most practical sequence is:

1. Start with a conventional immediate-release platform and map dissolution across pH 1.2, 4.5, and 6.8 media.
2. Screen particle size, superdisintegrants, wetting agents, and pH modifiers.
3. Select an amorphous dispersion only if conventional approaches fail.
4. Evaluate suspension or dispersible formats as separate products rather than forcing a liquid formulation from the tablet design.
5. Use FDA Inactive Ingredient Database precedent to control regulatory risk.
6. Build claims around measurable performance, not an undifferentiated excipient list.
7. Consider 505(b)(2) only when the product has a clinical or administration advantage that an ANDA cannot efficiently capture.
8. Protect process parameters, solid-state controls, and critical material attributes as trade secrets where patent enforceability is weak.

Key Takeaways

• Probenecid is a mature generic drug with minimal original patent or exclusivity value remaining.
• The strongest excipient opportunity is a pH-controlled, dissolution-optimized immediate-release formulation.
• Pediatric suspension, dispersible, and taste-masked products offer the clearest patient-centered differentiation.
• Conventional excipient substitutions will face high generic entry risk and weak pricing power.
• Amorphous dispersions and modified-release systems may create stronger IP but carry higher development cost and regulatory risk.
• A new probenecid patent estate must rely on defined formulation performance, solid-state control, clinical benefit, or a specific method of use.
• Biosimilar risk is irrelevant because probenecid is a small-molecule drug.
• Commercial returns are more likely to come from niche delivery products, supply reliability, and contract development than from a premium branded tablet.

FAQs

Can probenecid be formulated as an oral solution?

A true oral solution is technically challenging because probenecid has limited water solubility. A suspension, reconstituted powder, or coated multiparticulate product is more practical unless a solubilization system can meet stability, tolerability, and regulatory requirements.

Which excipient is most likely to improve probenecid dissolution?

A combination of controlled particle size, a superdisintegrant, and a suitable pH modifier is the most rational starting point. No single excipient can be selected without compatibility, dissolution, stability, and exposure data.

Is a probenecid extended-release tablet commercially attractive?

It could reduce dosing frequency, but the opportunity is limited by the drug’s generic pricing, dose requirements, and the need to establish a clinically meaningful pharmacokinetic or adherence benefit.

Can a probenecid formulation receive new patents?

Yes. Potentially protectable subject matter includes a novel solid form, a stable amorphous dispersion, a specific excipient ratio, a pediatric dosage form, a controlled-release system, or a clinically supported new use. Patent strength will depend heavily on unexpected results and claim specificity.

Does probenecid have biosimilar competition?

No. Biosimilar provisions apply to biological products. Probenecid is a chemically synthesized small molecule and competes through generic-drug pathways.

References

1. Food and Drug Administration. (2019). Applications covered by section 505(b)(2): Guidance for industry. U.S. Department of Health and Human Services.

2. Food and Drug Administration. (2023a). Probenecid tablet prescribing information. U.S. Department of Health and Human Services.

3. Food and Drug Administration. (2024a). Inactive Ingredient Database. U.S. Department of Health and Human Services.

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

5. National Center for Biotechnology Information. (2024). PubChem compound summary for probenecid. National Library of Medicine.