List of Excipients in Branded Drug CHLORTHALIDONE

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Generic Drugs Containing CHLORTHALIDONE

Company	Ingredient	NDC	Excipient
Mylan Pharmaceuticals Inc	chlorthalidone	0378-0222	CELLULOSE, MICROCRYSTALLINE
Mylan Pharmaceuticals Inc	chlorthalidone	0378-0222	D&C YELLOW NO. 10
Mylan Pharmaceuticals Inc	chlorthalidone	0378-0222	SILICON DIOXIDE
Mylan Pharmaceuticals Inc	chlorthalidone	0378-0222	SODIUM STARCH GLYCOLATE TYPE A POTATO

What are the Most Frequently-Used Excipients in CHLORTHALIDONE?

# Of NDCs	Excipient
1	ACID YELLOW 3
1	BLUE 1
7	CALCIUM STEARATE
110	CELLULOSE, MICROCRYSTALLINE

Chlorthalidone Excipient Strategy and Commercial Opportunities

Last updated: October 1, 2026

Chlorthalidone is an established, low-cost thiazide-like diuretic with long pharmacologic duration, broad generic availability, and limited conventional patent protection. The commercial opportunity is not a new-molecule franchise. It is a formulation and product-positioning opportunity centered on dose uniformity, swallowability, liquid or orally disintegrating delivery, fixed-dose combinations, supply reliability, and improved regulatory execution.

The strongest near-term formulation strategy is an immediate-release tablet using a robust direct-compression or wet-granulation platform. Commercial differentiation is more likely in low-dose uniformity, pediatric or geriatric delivery, combination products, and international markets than in a standard 25-mg tablet.

What is chlorthalidone and why does its formulation matter?

Chlorthalidone is a long-acting thiazide-like diuretic used primarily for hypertension and edema. It inhibits sodium and chloride reabsorption in the distal convoluted tubule. The drug has a substantially longer effective duration than hydrochlorothiazide, with an apparent terminal half-life commonly reported in the range of approximately 40 to 60 hours, although published values vary by study and assay method (DailyMed, 2023; Carter et al., 2004).

Attribute	Commercial relevance
Active ingredient	Chlorthalidone
Common strengths	25 mg and 50 mg; 12.5-mg dosing often requires a scored tablet or half-tablet
Typical dosage form	Immediate-release oral tablet
Therapeutic areas	Hypertension and edema
Drug class	Thiazide-like diuretic
Solubility profile	Very slightly soluble to practically insoluble in water, depending on compendial description
Pharmacologic duration	Long acting, with prolonged exposure relative to hydrochlorothiazide
Main formulation risk	Low-dose content uniformity and dissolution consistency
Main commercial issue	Generic price competition and limited product differentiation

The drug’s low aqueous solubility does not prevent conventional oral-tablet development because the administered dose is small and the therapeutic product is an immediate-release solid. It does, however, make particle-size control, wetting, disintegration, and dissolution relevant to bioequivalence and manufacturing consistency.

What excipients are suitable for chlorthalidone tablets?

A conventional chlorthalidone tablet can use standard excipients already accepted in oral solid-dose products. The best composition depends on the manufacturing process, target tablet weight, hardness, dissolution profile, and need for scoreability.

Direct-compression platform

A direct-compression formulation can contain:

• Microcrystalline cellulose as a filler and dry binder
• Lactose monohydrate or anhydrous lactose as a diluent
• Crospovidone or croscarmellose sodium as a superdisintegrant
• Colloidal silicon dioxide as a glidant
• Magnesium stearate or sodium stearyl fumarate as a lubricant

Direct compression has the lowest process complexity and can be attractive for a low-cost generic. Its principal risks are poor content uniformity, segregation, electrostatic behavior, and insufficient flow when the drug load is low.

Wet-granulation platform

Wet granulation can improve blend uniformity and reduce segregation. A typical platform may use:

• Lactose or microcrystalline cellulose as filler
• Povidone or hydroxypropyl cellulose as binder
• Sodium starch glycolate, crospovidone, or croscarmellose sodium as disintegrant
• Colloidal silicon dioxide as glidant
• Magnesium stearate as lubricant

Wet granulation is more expensive and introduces additional variables, including granule size, residual moisture, drying endpoint, and potential changes in dissolution. It is more suitable when direct compression cannot deliver reliable content uniformity or tablet mechanical strength.

Excipient selection matrix

Excipient function	Candidate excipients	Strategic rationale	Key risk
Diluent	Microcrystalline cellulose, lactose, mannitol, dibasic calcium phosphate	Controls tablet weight and compressibility	Flow, moisture, or compatibility differences
Binder	Povidone, hydroxypropyl cellulose	Supports granule strength	Slower disintegration if overused
Disintegrant	Crospovidone, croscarmellose sodium, sodium starch glycolate	Promotes tablet breakup and drug release	Swelling, sensitivity to compression force
Glidant	Colloidal silicon dioxide	Improves flow and reduces segregation	Overuse can impair compactability
Lubricant	Magnesium stearate, sodium stearyl fumarate	Reduces sticking and ejection force	Hydrophobic film and slower dissolution
Taste modifier	Sucralose, mannitol, flavor system	Relevant to liquid or orally disintegrating products	Stability and regulatory burden
Suspension aid	Xanthan gum, sodium carboxymethylcellulose, hydroxypropyl cellulose	Supports oral suspension uniformity	Viscosity and redispersibility
Preservative	Product-specific preservative system	May be required for multidose liquids	Microbial and compatibility testing

The formulation should avoid excessive lubricant concentration or extended lubrication time. Chlorthalidone’s low dose increases the importance of achieving a uniform drug distribution before lubrication, because lubricant overprocessing can further slow wetting and dissolution.

How should low-dose chlorthalidone content uniformity be controlled?

Content uniformity is the central technical issue for a 12.5-mg or lower-dose product. A 25-mg tablet contains a relatively small amount of active ingredient compared with the total excipient mass, creating a risk of segregation during blending, transfer, hopper discharge, and compression.

A commercial development program should prioritize:

1. Drug particle-size characterization and, where appropriate, micronization.
2. Geometric dilution or preblending of chlorthalidone with a portion of the diluent.
3. Controlled blend order and mixing time.
4. Low-segregation excipient grades.
5. In-process sampling from multiple blender and compression locations.
6. Blend uniformity and finished-product content-uniformity testing under USP <905>.
7. Tablet weight control and tablet-scoring validation.
8. Dissolution testing using a discriminating method rather than only a routine release method.

The manufacturer should establish a particle-size and morphology specification that links active-material attributes to dissolution and content uniformity. A narrow particle-size distribution can improve blend homogeneity, but excessive fines may worsen flow and increase adhesion to processing equipment.

What formulation patents could protect a chlorthalidone product?

The original chlorthalidone compound and basic tablet concepts are long past ordinary United States patent life. New protection would need to focus on a specific product or manufacturing feature rather than the active ingredient itself.

Potential claim categories include:

Claim category	Commercial value	Patentability outlook
Immediate-release tablet composition	Moderate if it solves a defined manufacturing or dissolution problem	Limited unless supported by unexpected results
Low-dose content-uniformity process	Moderate to high for a difficult product	Depends on technical specificity and non-obvious process controls
Orally disintegrating tablet	Moderate	Possible if taste, disintegration, and stability are credibly improved
Oral solution or suspension	High for pediatric, geriatric, or swallowing-impaired patients	Formulation and stability claims may be available
Extended-release formulation	Moderate	Requires clinical and pharmacokinetic justification
Fixed-dose combination	High if clinically useful and not already crowded	Combination and method-of-use claims may be available
Manufacturing process	Moderate	Stronger where the process produces measurable quality advantages
New indication	Potentially high	Requires clinical evidence and regulatory support

A formulation patent must be drafted around measurable technical features, such as dissolution ranges, particle-size limits, excipient ratios, suspension stability, dose uniformity, or pharmacokinetic performance. A broad claim covering “chlorthalidone with pharmaceutically acceptable excipients” would face substantial prior-art and obviousness exposure.

What is the Orange Book status of chlorthalidone?

Chlorthalidone is a long-established generic drug. FDA-approved products are listed in the Approved Drug Products with Therapeutic Equivalence Evaluations, commonly called the Orange Book, but the market is primarily multisource generic rather than protected by a current new-drug exclusivity period (U.S. Food and Drug Administration, 2024a).

The commercial implications are:

• No meaningful new chemical entity exclusivity remains.
• Any current product-specific protection would depend on an identified patent, regulatory exclusivity, or proprietary formulation.
• A standard immediate-release generic tablet generally has limited ability to support premium pricing.
• Orange Book patent listings must be reviewed product by product because listed patents attach to specific approved applications, not automatically to the active ingredient as a whole.
• A new 505(b)(2) product could obtain approval based partly on existing literature or an approved reference product, but its exclusivity would depend on the clinical and formulation changes supporting the application.

For a new chlorthalidone product, the Orange Book strategy would be more relevant if the sponsor develops a novel dosage form, a combination product, or a differentiated indication.

When does chlorthalidone lose exclusivity?

Chlorthalidone lost practical market exclusivity decades ago. The molecule was introduced in the 1960s, and the current U.S. market is generic. Standard patent terms for the original active ingredient and early formulations have expired.

Exclusivity timeline

Milestone	Approximate status
Original clinical and commercial introduction	1960s
Original compound and early product patents	Expired
U.S. generic availability	Established
New chemical entity exclusivity	Expired
Current standard tablet market	Multisource generic
Remaining protection opportunities	New formulations, combinations, manufacturing processes, or clinical uses

The absence of basic compound protection does not prevent later patents. A sponsor can still seek protection for a new oral liquid, orally disintegrating tablet, modified-release system, or combination therapy. Those rights would be narrow and vulnerable to design-around unless supported by a clear technical advantage.

Are there Paragraph IV challenges involving chlorthalidone?

The Paragraph IV framework is most relevant when an approved product has a listed patent in the Orange Book. Because conventional chlorthalidone tablets are old generic products, there is no broad, commercially important Paragraph IV barrier comparable to newer branded drugs.

Potential Paragraph IV activity could arise if a sponsor launches a newly patented formulation or combination product. A generic challenger could then certify that the listed patent is invalid, unenforceable, or not infringed. For a conventional chlorthalidone tablet, the principal regulatory pathway is ordinary abbreviated new drug application approval with demonstration of pharmaceutical equivalence and bioequivalence, rather than litigation against an active branded patent estate.

There is no recognized current patent thicket around basic chlorthalidone immediate-release tablets. Any litigation assessment should focus on the specific reference-listed drug, formulation, dosage form, and Orange Book listing at the time of filing.

What manufacturing and intellectual-property barriers affect chlorthalidone?

Manufacturing barriers are more significant than molecule-level intellectual-property barriers.

Technical barriers

The main manufacturing challenges are:

• Low-dose active distribution
• Powder segregation
• Variable flow into the tablet press
• Lubrication-related dissolution changes
• Tablet splitting performance
• Stability under humidity and elevated temperature
• Scale-up reproducibility
• Cleaning validation for low-dose potent material

Chlorthalidone is not generally treated as a highly potent oncology or hormonal compound, but low-dose handling still creates sampling and cross-contamination considerations. The manufacturing process should use validated containment, cleaning limits, and analytical methods appropriate to the facility.

Intellectual-property barriers

A sponsor may encounter:

• Process patents covering low-dose blending or granulation
• Formulation patents covering liquid or modified-release products
• Combination-product patents
• Method-of-use patents tied to a defined patient population
• Device or packaging claims for unit-dose liquids or adherence systems

These rights are likely to be narrow. Freedom-to-operate analysis should distinguish expired chlorthalidone patents from live patents directed to excipient systems, dosing regimens, combination products, or manufacturing methods.

What commercial opportunities exist for chlorthalidone?

1. Reliable low-cost generic tablets

The largest established opportunity is a dependable generic supply of 25-mg and 50-mg tablets, with a scored 25-mg tablet supporting 12.5-mg dosing. Buyers include retail pharmacies, hospital systems, government purchasers, and managed-care formularies.

The product is commercially difficult because price competition is intense and the active ingredient is inexpensive. The differentiators are manufacturing reliability, shortage avoidance, quality history, and contract supply.

2. Pediatric and geriatric oral liquid

An oral suspension or solution could address patients who cannot swallow tablets. A liquid product would need evidence for:

• Chemical and physical stability
• Dose uniformity throughout shelf life
• Redispersibility if suspended
• Device accuracy
• Preservative effectiveness where applicable
• Palatability
• In-use stability after opening

A liquid formulation has greater product differentiation than a standard tablet and may support a 505(b)(2) strategy if the dosage form and clinical use are sufficiently differentiated.

3. Orally disintegrating tablets

An orally disintegrating tablet could target older adults, patients with dysphagia, and adherence-sensitive populations. The main development risks are taste, friability, moisture sensitivity, and dose uniformity. Mannitol, crospovidone, and taste-masking technologies may be useful, but each increases formulation and stability complexity.

4. Fixed-dose combinations

Chlorthalidone could be evaluated in combinations with antihypertensive agents such as:

• An angiotensin-converting enzyme inhibitor
• An angiotensin receptor blocker
• A calcium-channel blocker
• A potassium-sparing diuretic

Combination products may improve adherence and create a more defensible regulatory and commercial position. The main constraints are dose flexibility, electrolyte management, clinical labeling, and competition from established hydrochlorothiazide combinations.

5. International supply and institutional markets

Chlorthalidone has a long clinical history and can be commercially relevant in markets where hypertension treatment guidelines favor long-acting thiazide-like diuretics. Opportunities may exist in:

• Public-sector tenders
• Emerging-market hypertension programs
• Hospital formulary supply
• Regional contract manufacturing
• Private-label generic portfolios

Geographic value depends on local registration requirements, reference-product rules, pricing controls, and whether the market accepts literature-based or abridged applications.

How does chlorthalidone compare with hydrochlorothiazide?

Chlorthalidone is often positioned against hydrochlorothiazide because both are thiazide or thiazide-like diuretics used for hypertension. Chlorthalidone’s longer duration can support once-daily dosing and sustained blood-pressure control, while hydrochlorothiazide has deeper generic penetration and a larger fixed-dose-combination market.

Factor	Chlorthalidone	Hydrochlorothiazide
Duration	Longer	Shorter
Standard generic availability	High	Very high
Combination-product penetration	More limited	Extensive
Formulation complexity	Low to moderate	Low
Differentiation potential	Long-acting profile and new dosage forms	Combination breadth and established prescribing
Commercial pricing	Generic and price-sensitive	Generic and highly price-sensitive
Main clinical concern	Electrolyte abnormalities, especially hypokalemia and hyponatremia	Similar electrolyte risks

Clinical comparative evidence has not produced a universal commercial replacement of hydrochlorothiazide by chlorthalidone. Chlorthalidone’s long duration can be clinically attractive, but its adverse-effect profile and dosing flexibility must be addressed in labeling and market access materials (Dhalla et al., 2013; Wright et al., 2020).

What FDA regulatory pathway is appropriate for a new chlorthalidone product?

Abbreviated new drug application

An ANDA is appropriate for a conventional immediate-release generic tablet that matches the reference product in dosage form, strength, route, and active ingredient. The sponsor must establish pharmaceutical equivalence and bioequivalence and satisfy chemistry, manufacturing, and controls requirements.

505(b)(2) application

A 505(b)(2) application may be more suitable for:

• An oral solution or suspension
• An orally disintegrating tablet
• A modified-release product
• A new combination
• A product with a new dosing regimen or population

The sponsor would need to define the reliance pathway and generate evidence supporting the proposed differences. The regulatory value of a 505(b)(2) product depends on whether the new dosage form produces a clinically meaningful benefit or solves a recognized administration problem.

What patent strength does a new chlorthalidone product have?

A conventional tablet has weak patent strength because the active ingredient, route, and basic dosage form are old. A differentiated product can have moderate patent strength if claims are narrow, technically supported, and difficult to design around.

The strongest potential claim sets are likely to involve:

1. A stable, dose-uniform oral liquid.
2. A low-dose orally disintegrating tablet with defined performance.
3. A clinically justified fixed-dose combination.
4. A manufacturing process that reliably controls content uniformity.
5. A modified-release dosage form with a demonstrated pharmacokinetic or adherence benefit.

The weakest strategy is a broad formulation patent that relies only on routine excipient substitution without a demonstrated performance improvement.

What generic launch scenarios exist for chlorthalidone?

Scenario	Likely market effect	Commercial assessment
Standard 25-mg or 50-mg tablet	Immediate multisource price pressure	Low differentiation
Scored 25-mg tablet with strong splitability data	Improved dosing usability	Moderate
Pediatric oral suspension	New patient segment	Moderate to high
Orally disintegrating tablet	Differentiated administration	Moderate
Fixed-dose combination	Greater adherence proposition	High but clinically and regulatorily complex
Modified-release product	Potential dosing differentiation	High development risk
Shortage-resistant contract supply	Institutional and payer value	Moderate, dependent on execution

Key Takeaways

• Chlorthalidone is an old, genericized active ingredient with no meaningful basic compound exclusivity remaining.
• The core formulation challenge is low-dose content uniformity, not conventional tablet manufacture.
• Microcrystalline cellulose, lactose, crospovidone, croscarmellose sodium, colloidal silicon dioxide, and magnesium stearate are practical excipient candidates.
• Wet granulation may improve uniformity but adds cost and process risk.
• The strongest commercial opportunities are oral liquids, orally disintegrating tablets, fixed-dose combinations, scored tablets, and reliable institutional supply.
• Standard immediate-release tablets have weak patent prospects and severe price competition.
• A 505(b)(2) pathway may be appropriate for a differentiated dosage form or combination product.
• Paragraph IV risk is limited for basic chlorthalidone tablets because the molecule and conventional products are long genericized.
• Formulation and manufacturing patents must claim measurable technical advantages rather than routine excipient combinations.
• Compared with hydrochlorothiazide, chlorthalidone has a longer duration but a smaller combination-product footprint and greater need for differentiated commercialization.

FAQs

Can chlorthalidone be formulated as an oral solution?

Yes. An oral solution or suspension is technically possible, but development must address poor aqueous solubility, dose uniformity, chemical stability, microbial control, palatability, and device accuracy. A suspension may be more practical than a true solution if solubility limits prevent the required concentration.

Is chlorthalidone suitable for an orally disintegrating tablet?

Yes. An orally disintegrating tablet could target patients with dysphagia and improve administration convenience. The principal development issues are taste masking, tablet friability, moisture sensitivity, and uniform distribution of the low-dose active ingredient.

Does chlorthalidone have biosimilar risk?

No. Chlorthalidone is a small-molecule drug, not a biologic. The relevant competitive risks are generic entry, authorized generic supply, formulation substitution, and fixed-dose combination competition.

What is the most defensible commercial product concept for chlorthalidone?

A stable, dose-uniform pediatric or geriatric oral suspension has greater differentiation potential than another conventional 25-mg tablet. A scored immediate-release tablet remains the lowest-risk product but has limited pricing power.

Can excipients create patent protection for chlorthalidone?

Excipients alone rarely create strong protection. Patentability is more credible when a defined excipient system produces an unexpected result, such as improved low-dose content uniformity, faster dissolution, superior suspension stability, reduced variability, or improved patient administration.

References

1. Carter, B. L., Ernst, M. E., & Cohen, J. D. (2004). Hydrochlorothiazide versus chlorthalidone in hypertension: Clinical and economic considerations. Hypertension, 43(1), 4-9.

2. DailyMed. (2023). Chlorthalidone tablet: U.S. prescribing information. National Library of Medicine. https://dailymed.nlm.nih.gov/

3. Dhalla, I. A., Gomes, T., Yao, Z., Nagge, J., Persaud, N., Hellings, C., Mamdani, M. M., & Juurlink, D. N. (2013). Chlorthalidone versus hydrochlorothiazide for the treatment of hypertension in older adults: A population-based cohort study. Annals of Internal Medicine, 158(6), 447-455.

4. U.S. Food and Drug Administration. (2024a). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/

5. U.S. Food and Drug Administration. (2024b). Inactive ingredient database. https://www.accessdata.fda.gov/scripts/cder/iig/

6. United States Pharmacopeia. (2024). USP-NF general chapters <905> uniformity of dosage units and <711> dissolution. United States Pharmacopeial Convention.

7. Wright, J. T., Jr., Williamson, J. D., Whelton, P. K., Snyder, J. K., Sink, K. M., Rocco, M. V., Reboussin, D. M., Rahman, M., Oparil, S., Lewis, C. E., Kimmel, P. L., Johnson, K. C., Goff, D. C., Jr., Fine, L. J., Davis, B. R., & the SPRINT Research Group. (2015). A randomized trial of intensive versus standard blood-pressure control. New England Journal of Medicine, 373(22), 2103-2116.