List of Excipients in Branded Drug ISONIAZID

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Generic Drugs Containing ISONIAZID

Company	Ingredient	NDC	Excipient
Liberty Pharmaceuticals Inc	isoniazid	0440-1655	CELLULOSE, MICROCRYSTALLINE
Liberty Pharmaceuticals Inc	isoniazid	0440-1655	CROSPOVIDONE
Liberty Pharmaceuticals Inc	isoniazid	0440-1655	SILICON DIOXIDE

What are the Most Frequently-Used Excipients in ISONIAZID?

# Of NDCs	Excipient
2	ANHYDROUS CITRIC ACID
7	ANHYDROUS LACTOSE
11	CALCIUM STEARATE

Isoniazid Excipient Strategy and Commercial Opportunities

Last updated: October 26, 2026

Isoniazid is an established tuberculosis medicine with low active-ingredient patent risk and limited opportunity for conventional exclusivity. Commercial value lies in differentiated dosage forms, pediatric delivery, fixed-dose combinations, improved stability, taste masking, adherence support, and supply-chain reliability. The strongest product concepts are dispersible tablets, low-dose pediatric presentations, oral liquids with robust stability, and combination products containing rifampicin or other first-line antituberculosis agents.

What is the current FDA and regulatory status of isoniazid?

Isoniazid is an established prescription antibacterial used primarily for treatment and prevention of tuberculosis caused by susceptible Mycobacterium tuberculosis. It is available as an oral tablet, oral solution, and injectable formulation in various markets. FDA labeling identifies isoniazid for active tuberculosis treatment and latent tuberculosis infection, usually as part of a multidrug regimen or preventive regimen.[1]

The drug has no meaningful new-molecule exclusivity remaining. Commercial products are generally supplied through abbreviated new drug applications, legacy applications, institutional procurement contracts, and global-health tenders.

Regulatory attribute	Isoniazid position
Active ingredient	Isoniazid
Primary indication	Treatment and prevention of tuberculosis
FDA regulatory pathway	Generic and legacy prescription products
New chemical entity exclusivity	Expired
Orphan-drug exclusivity	Not applicable to the established active ingredient
Orange Book significance	Product-specific patent and exclusivity listings should be checked for the individual applicant; no broad active-ingredient exclusivity is expected
Common dosage forms	Tablets, oral solution, injection
Common strengths	50 mg, 100 mg, 300 mg tablets; market-dependent liquid and injectable strengths
Main commercial buyers	Public-health programs, hospitals, pharmacies, government tenders, global-health organizations
Principal clinical constraints	Hepatotoxicity, peripheral neuropathy, drug interactions, adherence, pediatric dosing

FDA labeling recommends pyridoxine supplementation for selected patients at increased risk of isoniazid-associated peripheral neuropathy, including people with diabetes, alcoholism, malnutrition, HIV infection, renal disease, pregnancy, or seizure disorders.[1]

What patents protect isoniazid products?

The original composition-of-matter patent estate for isoniazid is no longer commercially relevant. Isoniazid was introduced in the early 1950s, placing any original compound protection far beyond the standard U.S. patent term.[2]

Current patent risk is therefore product-specific rather than molecule-specific. Potentially relevant rights may cover:

• Modified-release tablets
• Taste-masked pediatric formulations
• Stable oral liquid systems
• Fixed-dose combinations
• Nanoparticle or amorphous dispersions
• Coated multiparticulates
• Manufacturing processes
• Packaging systems that extend liquid stability
• Combination regimens or specific treatment schedules

A formulation patent must provide a technical distinction over ordinary tablets or solutions. A claim covering routine excipients, conventional compression, or ordinary flavoring may face substantial validity and obviousness risk under U.S. patent law.

How strong is the patent estate for isoniazid?

The core isoniazid patent estate is weak because the active ingredient is old and widely available. A new formulation estate could be stronger if it demonstrates measurable improvements in one or more of the following areas:

1. Long-term chemical stability in aqueous media.
2. Reduced bitterness without reducing dissolution.
3. Improved dose uniformity for pediatric administration.
4. Reduced tablet size or improved swallowability.
5. Compatibility with rifampicin or other combination-drug actives.
6. Improved resistance to humidity and tropical storage conditions.
7. Clinically meaningful adherence improvement.

Patent strength will depend on claim scope, comparative data, stability duration, dissolution performance, and the availability of prior-art formulations.

When does isoniazid lose exclusivity?

Isoniazid has already lost active-ingredient exclusivity. The commercial question is not when the molecule loses exclusivity but whether a sponsor can create defensible protection around a new dosage form, combination, manufacturing process, or delivery technology.

For U.S. products, generic competition is normally possible through an ANDA when the proposed product can demonstrate pharmaceutical equivalence and bioequivalence to a reference product. A Paragraph IV certification may arise only if the reference product has a listed patent that the applicant seeks to challenge. If no relevant patent is listed, a Paragraph IV challenge may not be necessary.

What is the Orange Book status of isoniazid?

The Orange Book is product-specific. It lists approved drug products and, where applicable, patents and regulatory exclusivity. A company evaluating an isoniazid product must review the current Orange Book by dosage form, strength, applicant, and reference-listed drug.[3]

For a conventional generic isoniazid tablet, the absence of active ingredient protection generally reduces patent litigation exposure. A sponsor developing a novel formulation should expect a separate Orange Book and patent strategy if the product is approved under an NDA rather than an ANDA.

Which excipients are suitable for isoniazid tablets?

The excipient strategy should address manufacturability, chemical compatibility, dissolution, taste, and global regulatory acceptability. Isoniazid is water-soluble and generally does not require a solubility-enhancing excipient for immediate-release tablets. The principal formulation problem is usually dose delivery and stability rather than dissolution.

Recommended immediate-release tablet architecture

Formulation function	Candidate excipients	Strategic rationale
Diluent	Microcrystalline cellulose, mannitol, dibasic calcium phosphate	Supports tablet mass, flow, and compression
Binder	Povidone, copovidone, pregelatinized starch	Improves granule and tablet strength
Disintegrant	Crospovidone, croscarmellose sodium, sodium starch glycolate	Supports rapid breakup and dissolution
Lubricant	Magnesium stearate, sodium stearyl fumarate	Reduces sticking and ejection force
Glidant	Colloidal silicon dioxide	Improves powder flow
Sweetener	Sucralose, acesulfame potassium, sodium saccharin	Relevant to chewable and dispersible products
Flavor	Fruit or mint systems selected for stability	Masks bitterness in pediatric products
Film coat	Hypromellose-based coating, titanium dioxide where permitted, pigments	Improves handling, identification, and taste masking

Mannitol is often attractive for chewable or orally disintegrating systems because it has a relatively clean mouthfeel and low hygroscopicity. Microcrystalline cellulose supports robust compression but may produce a less favorable texture in dispersible or chewable products.

Lactose should be evaluated carefully. Isoniazid contains hydrazine functionality and may participate in reactions with reducing sugars under stress or storage conditions. A lactose-containing formulation is not automatically unsuitable, but it should be supported by impurity profiling, accelerated stability, and long-term data. Mannitol, selected grades of starch, and nonreducing diluent systems may offer a more conservative compatibility strategy.

What formulations are protected by isoniazid patents?

The most commercially defensible formulation categories are pediatric and combination products rather than standard adult tablets.

Pediatric dispersible tablets

Pediatric tuberculosis treatment requires weight-based dosing, and young children may have difficulty swallowing conventional tablets. A dispersible tablet can improve dose administration without the manufacturing and stability burden of a liquid.

Key design targets include:

• Rapid dispersion in a small volume of water
• Low sedimentation after dispersion
• Acceptable bitterness
• Dose strengths that support weight-band dosing
• Low friability
• Resistance to humidity
• Compatibility with coadministered rifampicin

A dispersible product can use mannitol, microcrystalline cellulose, crospovidone, low-substituted hydroxypropyl cellulose, sweeteners, and flavor systems. Taste masking may require polymer coating, ion-exchange technology, lipid barriers, or multiparticulate encapsulation.

Oral liquids

Liquid isoniazid products can support infants, young children, dysphagic patients, and patients requiring flexible dosing. The principal development risks are chemical stability, preservative performance, precipitation, microbial control, and palatability.

A commercial liquid should be designed around:

• A validated pH range
• Low oxygen exposure
• Light-protective packaging where justified
• A preservative system that remains effective over shelf life
• Compatible bottle, cap, liner, and dosing syringe
• Clear impurity limits, including hydrazine-related degradants
• Stability under high-temperature and high-humidity conditions

Single-dose sachets or unit-dose cups may offer an advantage in public-health programs by reducing dosing errors and contamination risk.

Fixed-dose combinations

Fixed-dose combinations are commercially important in tuberculosis because they simplify regimens and support adherence. Isoniazid is commonly combined with rifampicin, pyrazinamide, and ethambutol in various treatment products. It is also used in combinations with rifapentine or rifampicin for preventive-treatment regimens, depending on the jurisdiction and clinical protocol.[4]

Combination products create substantial formulation complexity. Rifampicin can have different stability and dissolution requirements from isoniazid. Moisture, pH, compression force, and coating materials can affect both actives. Bilayer tablets, separate granules within one tablet, coated particles, or capsule-based systems may be preferable to a simple homogeneous blend.

How should manufacturers manage isoniazid excipient compatibility?

Isoniazid development should include compatibility studies before final excipient selection. The program should test binary mixtures and prototype blends under temperature and humidity stress.

High-priority compatibility tests

• Assay and degradation products by stability-indicating HPLC
• Hydrazine and related impurity monitoring
• Water activity and moisture uptake
• Differential scanning calorimetry
• Powder X-ray diffraction where solid-state changes are relevant
• Dissolution after accelerated storage
• Tablet hardness, friability, and disintegration
• Packaging interaction studies
• Microbial and preservative effectiveness testing for liquids

Excipient selection should avoid unnecessary reducing sugars where compatibility data are weak. The sponsor should also evaluate the impact of alkaline or acidic microenvironments, because pH can influence both degradation and taste.

Packaging is part of the excipient and formulation strategy. High-density polyethylene bottles with desiccants, foil blisters, and unit-dose packs may provide different stability profiles. For tropical markets, the packaging system should be tested under International Council for Harmonisation climatic conditions and relevant WHO stability expectations.[5]

What generic entry risks exist for isoniazid?

Generic entry risk is high for conventional tablets because:

• The active ingredient is old.
• The dosage form is technically routine.
• Multiple suppliers exist.
• Bioequivalence requirements are generally manageable for immediate-release products.
• Public-health procurement favors low-cost, interchangeable products.
• Manufacturing capacity is available in several low-cost regions.

The principal barriers are commercial rather than patent-based. These include demand volatility, government tender concentration, quality audits, shortages of active pharmaceutical ingredient, low margins, and the need to maintain multiple country registrations.

A differentiated pediatric product can reduce direct price competition, but it may face slower uptake because public-health agencies often require WHO prequalification, local registration, procurement approval, or inclusion in national treatment guidelines.

Which companies are challenging isoniazid products?

The relevant competitive field is fragmented. Generic manufacturers, contract development and manufacturing organizations, regional pharmaceutical companies, and public-sector suppliers compete in the market. Competition is usually based on price, regulatory status, tender eligibility, manufacturing reliability, and access to active pharmaceutical ingredient rather than on patent litigation.

For conventional isoniazid products, a Paragraph IV litigation wave is unlikely unless a new reference product carries formulation or method-of-use patents. A sponsor launching a novel product should conduct a current Orange Book, Patent Center, and international patent-family review before filing.

What licensing deals are available for isoniazid products?

Licensing opportunities are more likely to involve formulation technology, manufacturing capacity, or public-health distribution than the active ingredient itself.

Potential transaction structures include:

Opportunity	Likely counterparty	Commercial rationale
Pediatric dispersible technology	Specialty formulation company	Adds differentiation and tender value
Fixed-dose combination platform	Tuberculosis-focused manufacturer	Expands regimen coverage
WHO-prequalified manufacturing	Regional generic company	Accelerates global procurement access
Oral-liquid technology	Pediatric drug developer	Supports flexible dosing and adherence
Contract manufacturing	API or finished-dose producer	Reduces capital expenditure
Public-health distribution	Government or nonprofit buyer	Improves volume visibility
Packaging and dosing device	Device or packaging company	Reduces dosing errors and contamination

A license should define ownership of formulation patents, regulatory data, process improvements, stability data, improvements to excipient systems, and rights by country. For public-health products, the agreement should also address tender pricing, minimum volumes, quality failures, pharmacovigilance, and supply continuity.

How does isoniazid compare with rifampicin and rifapentine?

Isoniazid has lower formulation complexity and lower patent risk than rifampicin or rifapentine. It is also less commercially differentiated as a standalone product.

Attribute	Isoniazid	Rifampicin	Rifapentine
Core patent risk	Low	Low to moderate, product-dependent	Higher for some modern formulations and regimens
Solubility challenge	Generally limited	More significant	Formulation-dependent
Taste issue	Significant in pediatric use	Significant	Significant
Fixed-dose importance	High	High	Increasing in preventive regimens
Standalone commercial differentiation	Limited	Moderate	Higher in selected regimens
Main formulation opportunity	Dispersible and liquid products	Stable combinations and pediatric delivery	Long-acting or regimen-supporting products
Price competition	High	High	More variable

Isoniazid is best positioned as part of a combination or pediatric platform rather than as a premium standalone adult tablet.

What commercial opportunities exist for isoniazid?

The most credible opportunities are:

1. Pediatric dispersible tablets with improved taste and weight-band dosing.
2. Stable, ready-to-use oral liquids.
3. Low-dose presentations for preventive therapy.
4. Fixed-dose combinations with rifampicin, pyrazinamide, or ethambutol.
5. Unit-dose packaging for public-health and institutional use.
6. Products designed for high-temperature and high-humidity markets.
7. WHO-prequalified products for global tenders.
8. Contract manufacturing for regional tuberculosis programs.
9. Co-packaged isoniazid and pyridoxine products where clinically and regulatorily appropriate.
10. Digital or device-enabled dosing systems paired with pediatric formulations.

Revenue exposure is usually volume-driven. Adult generic tablets carry limited pricing power, while differentiated pediatric and combination products can improve margin and procurement access. The largest opportunity is likely to come from securing reliable institutional demand rather than relying on retail prescriptions.

Key Takeaways

• Isoniazid has no meaningful remaining active-ingredient exclusivity.
• Conventional tablets face high generic-entry risk and limited patent protection.
• The strongest formulation opportunities are pediatric dispersible tablets, oral liquids, and fixed-dose combinations.
• Lactose and other reducing-sugar excipients require compatibility evaluation because of potential chemical interaction risks.
• Mannitol, microcrystalline cellulose, crospovidone, selected binders, and robust moisture protection are practical starting points for development.
• Commercial success depends on taste, stability, dosing accuracy, WHO or local regulatory status, and tender access.
• Patent value is more likely to arise from formulation, packaging, manufacturing, or combination technology than from isoniazid itself.
• Rifampicin and rifapentine combinations offer greater differentiation but also increase formulation and regulatory complexity.

FAQs

Is isoniazid suitable for an orally disintegrating tablet?

Yes. Isoniazid’s high aqueous solubility supports rapid release, but bitterness, dose size, tablet strength, and moisture sensitivity require careful design. Mannitol-based systems with taste-masking technology are potential candidates.

Can lactose be used in isoniazid tablets?

Yes, but the formulation should be supported by compatibility and stability data. Alternative diluents such as mannitol or microcrystalline cellulose may reduce concern over reactions involving reducing sugars.

Does isoniazid have a viable patent extension strategy?

Only through a new product architecture. Potential strategies include pediatric delivery, fixed-dose combinations, stable liquids, modified release, packaging systems, or manufacturing processes with measurable technical advantages.

What is the best commercial dosage form for pediatric tuberculosis?

A dispersible tablet is often more attractive than a conventional liquid because it can reduce shipping volume, improve stability, and support weight-band dosing. A liquid remains useful for infants and patients who cannot disperse tablets.

Is an isoniazid-pyridoxine combination commercially attractive?

It can be attractive where supplementation is routinely recommended or adherence is improved by combining products. The product must address dose flexibility, regulatory labeling, tablet size, and whether pyridoxine is appropriate for the full target population.

References

1. U.S. Food and Drug Administration. (n.d.). Isoniazid prescribing information. FDA.

2. World Health Organization. (2023). WHO consolidated guidelines on tuberculosis: Module 4, treatment: Drug-susceptible tuberculosis treatment. World Health Organization.

3. U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

4. World Health Organization. (2022). WHO consolidated guidelines on tuberculosis: Module 5, management of tuberculosis in children and adolescents. World Health Organization.

5. International Council for Harmonisation. (2003). ICH Q1A(R2): Stability testing of new drug substances and products. ICH.