Chlorthalidone; clonidine hydrochloride - Generic Drug Details

What are the generic sources for chlorthalidone; clonidine hydrochloride and what is the scope of patent protection?

Chlorthalidone; clonidine hydrochloride is the generic ingredient in three branded drugs marketed by Par Pharm, Natco Pharma, and Boehringer Ingelheim, and is included in five NDAs. Additional information is available in the individual branded drug profile pages.

Summary for chlorthalidone; clonidine hydrochloride

US Patents:	0
Tradenames:	3
Applicants:	3
NDAs:	5
Clinical Trials:	2
DailyMed Link:	chlorthalidone; clonidine hydrochloride at DailyMed

Recent Clinical Trials for chlorthalidone; clonidine hydrochloride

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
Instituto do Coracao	Phase 4
Conselho Nacional de Desenvolvimento Científico e Tecnológico	Phase 4
US Department of Veterans Affairs

See all chlorthalidone; clonidine hydrochloride clinical trials

Anatomical Therapeutic Chemical (ATC) Classes for chlorthalidone; clonidine hydrochloride

C02AC	Imidazoline receptor agonists
C02A	ANTIADRENERGIC AGENTS, CENTRALLY ACTING
C02	ANTIHYPERTENSIVES
C	Cardiovascular system

N02CX	Other antimigraine preparations
N02C	ANTIMIGRAINE PREPARATIONS
N02	ANALGESICS
N	Nervous system

S01EA	Sympathomimetics in glaucoma therapy
S01E	ANTIGLAUCOMA PREPARATIONS AND MIOTICS
S01	OPHTHALMOLOGICALS
S	Sensory organs

US Patents and Regulatory Information for chlorthalidone; clonidine hydrochloride

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Boehringer Ingelheim	COMBIPRES	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	017503-002	Approved Prior to Jan 1, 1982		DISCN	Yes	No
Par Pharm	CLONIDINE HYDROCHLORIDE AND CHLORTHALIDONE	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	071178-001	Dec 16, 1987		DISCN	No	No
Natco Pharma	CLORPRES	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	071325-003	Feb 9, 1987		DISCN	No	No
Par Pharm	CLONIDINE HYDROCHLORIDE AND CHLORTHALIDONE	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	071142-001	Dec 16, 1987		DISCN	No	No

Expired US Patents for chlorthalidone; clonidine hydrochloride

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Boehringer Ingelheim	COMBIPRES	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	017503-001	Approved Prior to Jan 1, 1982
Boehringer Ingelheim	COMBIPRES	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	017503-003	Apr 10, 1984
Boehringer Ingelheim	COMBIPRES	chlorthalidone; clonidine hydrochloride	TABLET;ORAL	017503-002	Approved Prior to Jan 1, 1982

Chlorthalidone and Clonidine Hydrochloride Market Dynamics and Financial Trajectory

Last updated: September 5, 2026

Chlorthalidone and clonidine hydrochloride are mature, low-cost generic medicines with long-expired primary patent protection, broad therapeutic substitution, and limited manufacturer-level revenue disclosure. Chlorthalidone has a relatively stable market supported by hypertension guidelines and chronic use. Clonidine hydrochloride has a more fragmented trajectory: oral clonidine remains a low-value generic, while transdermal clonidine and extended-release products create narrower, formulation-specific commercial niches.

Neither drug has a conventional branded-growth profile. Future value depends on supply reliability, contract pricing, dosage-form differentiation, institutional demand, and niche indications rather than patent exclusivity.

What are the current market positions of chlorthalidone and clonidine hydrochloride?

Attribute	Chlorthalidone	Clonidine hydrochloride
Primary therapeutic role	Thiazide-like diuretic for hypertension	Central alpha-2 adrenergic agonist
Common forms	25 mg and 50 mg tablets	Immediate-release tablets, transdermal patches, extended-release tablets
Main branded history	Hygroton	Catapres, Catapres-TTS, Kapvay
Market structure	Generic tablet market	Generic oral market plus dosage-form niches
Patent status	Primary patents expired	Primary patents expired; formulation-specific rights historically more relevant
Typical payer position	Low-cost generic	Low-cost generic, with higher prices for patches and extended-release products
Main commercial drivers	Guideline use, low acquisition cost, supply continuity	Hypertension, withdrawal-related use, ADHD, patch adherence, shortage management
Main commercial risk	Substitution by hydrochlorothiazide and other antihypertensives	Substitution by other antihypertensives, ADHD drugs, and alternative withdrawal therapies

Chlorthalidone is usually positioned as a longer-acting alternative to hydrochlorothiazide. Its clinical profile supports continued use in hypertension, but its market share remains constrained by entrenched prescribing patterns and low generic prices.

Clonidine is less commercially concentrated around one indication. Immediate-release tablets are used in hypertension and several off-label settings. Extended-release clonidine is associated with attention-deficit/hyperactivity disorder, while transdermal clonidine is used when adherence, gastrointestinal absorption, or dosing convenience matters.

How large are the markets for chlorthalidone and clonidine hydrochloride?

Publicly available sources do not provide reliable, current global revenue totals for the active ingredients as standalone products. Generic manufacturers generally report revenue by business segment, geography, or portfolio rather than by mature molecule. IQVIA and similar commercial datasets may contain prescription and sales estimates, but those figures are not consistently public.

The economic profile can be assessed from product structure:

Market factor	Chlorthalidone	Clonidine hydrochloride
Prescription volume potential	High because hypertension is prevalent	Moderate across hypertension, ADHD, and specialty uses
Revenue per prescription	Low	Low for tablets; higher for patches and extended-release products
Price competition	Severe	Severe for oral immediate-release products
Product differentiation	Limited	Greater in patches and extended-release tablets
Reimbursement leverage	Weak	Weak for tablets, stronger for differentiated delivery systems
Manufacturing complexity	Low to moderate	Low for tablets; higher for patches
Likely margin profile	Thin	Thin to moderate, depending on formulation

The largest commercial opportunity is not a new chemical entity launch. It is dependable supply in a market where shortages, contract changes, and manufacturer exits can shift share rapidly.

What is the FDA regulatory status of chlorthalidone and clonidine hydrochloride?

Both active ingredients are established FDA-approved drugs available through abbreviated new drug applications and legacy branded approvals.

Chlorthalidone FDA status

Chlorthalidone tablets are approved for hypertension and edema-related indications. The drug is administered orally and is generally marketed as a conventional tablet. FDA-approved labeling identifies 25 mg and 50 mg strengths among standard products, although available strengths vary by manufacturer and market channel (FDA, 2024a).

Chlorthalidone is a small-molecule generic product. It does not face biosimilar competition because biologic interchangeability rules do not apply.

Clonidine hydrochloride FDA status

Clonidine hydrochloride is marketed in several FDA-regulated dosage forms:

• Immediate-release oral tablets for hypertension.
• Transdermal therapeutic systems historically marketed as Catapres-TTS and generic equivalents.
• Extended-release tablets approved as Kapvay and generic equivalents for ADHD.

The extended-release product has a distinct regulatory and commercial position from immediate-release clonidine. The label carries specific dosing and discontinuation instructions because abrupt withdrawal can produce clinically significant rebound hypertension (FDA, 2023).

What is the Orange Book status of these drugs?

Chlorthalidone and immediate-release clonidine tablets are mature generic products. Their core active-ingredient patents and original formulation protections expired many years ago. Current Orange Book relevance is concentrated in listed reference products, approved generic equivalents, and any remaining product-specific patents or exclusivity entries rather than basic compound protection (FDA, 2024b).

For clonidine, dosage form matters:

• Immediate-release tablets have limited patent-based differentiation.
• Transdermal systems historically relied more heavily on delivery-system and formulation protection.
• Extended-release clonidine had product-specific regulatory exclusivity and formulation protection associated with the branded ADHD product, but those protections do not restore exclusivity to immediate-release clonidine.

A definitive current Orange Book patent table would require a product-by-product review of each reference-listed drug and its supplements. The active ingredients themselves do not have meaningful remaining primary patent barriers.

What patents protect chlorthalidone and clonidine hydrochloride?

Chlorthalidone patent estate

The commercially relevant chlorthalidone estate is effectively expired at the compound level. Current manufacturers generally compete through abbreviated approval, manufacturing efficiency, procurement contracts, and supply execution.

Potentially relevant intellectual property may still include:

• Manufacturing processes.
• Crystalline or particle forms.
• Tablet composition claims.
• Packaging and stability claims.
• Combination products.
• Method-of-use claims tied to a specific regimen or patient population.

These rights would have limited market impact unless they cover a commercially important formulation and are listed or enforceable against the relevant generic product.

Clonidine hydrochloride patent estate

Clonidine's original compound protection is expired. The more meaningful historical rights involved:

• Transdermal delivery systems.
• Adhesive and reservoir designs.
• Controlled-release oral formulations.
• Pediatric ADHD formulations.
• Combination products.
• Manufacturing and device components.

The remaining competitive significance of such rights depends on whether a patent covers a substitute product that physicians and payers treat as interchangeable with immediate-release tablets. In most cases, a patch or extended-release tablet occupies a narrower market and cannot prevent generic entry into the standard tablet segment.

When did chlorthalidone and clonidine lose exclusivity?

Both drugs lost meaningful small-molecule exclusivity decades ago.

Product	Core exclusivity position	Current implication
Chlorthalidone tablets	Compound and early product protection expired	Open generic competition
Immediate-release clonidine tablets	Compound and core product protection expired	Open generic competition
Transdermal clonidine	Historical delivery-system protection expired or narrowed over time	Generic and alternative patch competition
Extended-release clonidine	Product-specific protection was relevant to the ADHD formulation	Formulation-specific competition, separate from immediate-release tablets

The important distinction is between chemical exclusivity and formulation protection. A company may retain a commercial position for a patch, controlled-release tablet, or combination product even when the active ingredient is fully genericized.

Are there Paragraph IV challenges or generic launch risks?

Paragraph IV litigation risk is low for the basic tablet markets because the principal patents have expired. New Paragraph IV activity would be more likely around:

• A newly developed extended-release product.
• A transdermal delivery system.
• A combination product.
• A method-of-use patent with meaningful commercial scope.
• A reformulated product seeking differentiated reimbursement.

For chlorthalidone tablets, generic launch risk is primarily commercial rather than legal. New entrants can increase price erosion without confronting a significant patent barrier.

For clonidine, launch risk varies by dosage form:

Dosage form	Paragraph IV risk	Generic launch risk	Commercial barrier
Immediate-release tablet	Low	High	Low
Transdermal patch	Low to moderate	Moderate	Device, adhesive, and manufacturing validation
Extended-release tablet	Moderate when active patents exist	Moderate	Formulation development and bioequivalence
Combination product	Product-specific	Product-specific	Clinical and regulatory requirements

What formulations are protected by clonidine patents?

The strongest historical differentiation in clonidine has been associated with delivery technology rather than the active molecule.

Transdermal clonidine

Transdermal products require control of:

• Drug release over multiple days.
• Adhesion during wear.
• Skin tolerability.
• Dose uniformity.
• Patch application and removal.
• Manufacturing consistency.

These requirements create a higher entry barrier than conventional tablets. They do not necessarily create durable pricing power if multiple approved patches or therapeutic substitutes are available.

Extended-release clonidine

Extended-release tablets use formulation controls to modify exposure and dosing frequency. Commercial value depends on:

• Demonstrated clinical use in ADHD.
• Prescriber familiarity.
• Pediatric tolerability.
• Generic substitution rules.
• Reimbursement relative to stimulant and nonstimulant alternatives.

The formulation can support a higher price than immediate-release clonidine, but the addressable market is smaller.

Which companies compete in these markets?

Competition is distributed across generic manufacturers, contract suppliers, branded-generic platforms, and specialty dosage-form companies. Relevant participants may include large generic manufacturers such as Teva, Viatris, Sandoz, Hikma, and Amneal, as well as smaller suppliers and contract manufacturers. Market participation varies by country, strength, dosage form, and procurement contract.

The competitive field changes frequently because mature products are subject to:

• Manufacturer discontinuations.
• FDA shortage conditions.
• National purchasing contracts.
• Authorized generic arrangements.
• API sourcing constraints.
• Portfolio rationalization.
• Wholesaler inventory decisions.

A company with a small number of approved competitors can achieve temporary pricing improvement even when long-term patent protection is absent.

How does chlorthalidone compare with hydrochlorothiazide?

Chlorthalidone has a longer duration of action and is often viewed as a more potent thiazide-like diuretic. Hydrochlorothiazide has broader historical prescribing penetration and greater generic availability.

Factor	Chlorthalidone	Hydrochlorothiazide
Duration of action	Longer	Shorter
Historical prescribing base	Smaller	Larger
Generic availability	Broad but less uniform	Very broad
Pricing	Low	Very low
Guideline relevance	Strong in selected hypertension strategies	Established and widely used
Commercial opportunity	Share capture from clinical preference	Scale and procurement efficiency

Chlorthalidone can gain share when clinicians prioritize sustained blood-pressure control. It remains vulnerable to low-cost substitution and combination products containing hydrochlorothiazide.

How does clonidine compare with newer ADHD and antihypertensive drugs?

Clonidine competes with multiple therapeutic classes:

• Guanfacine, particularly extended-release guanfacine, in ADHD.
• Stimulants in ADHD.
• ACE inhibitors, angiotensin receptor blockers, calcium-channel blockers, and diuretics in hypertension.
• Other agents used in withdrawal management and symptom control.

Clonidine's advantages include low cost, long clinical experience, and multiple delivery routes. Its disadvantages include sedation, hypotension, rebound hypertension after abrupt discontinuation, and a less favorable tolerability profile than many first-line alternatives.

The oral immediate-release market has weak pricing power. The patch and extended-release segments have stronger differentiation but face substitution from both branded and generic alternatives.

What manufacturing and intellectual-property barriers affect supply?

Chlorthalidone

Manufacturing barriers are modest but not trivial. Key requirements include:

• Reliable active pharmaceutical ingredient supply.
• Consistent tablet potency.
• Impurity control.
• Stability across the labeled shelf life.
• Compliance with current good manufacturing practices.
• Adequate validation for low-volume strengths.

Because margins are low, a single manufacturing disruption can make the product commercially unattractive. This creates a recurring risk of supplier exits and regional shortages.

Clonidine hydrochloride

Tablet manufacturing is relatively straightforward. Transdermal systems have more significant technical requirements involving drug-in-adhesive systems, membranes, liners, release rates, and packaging. Extended-release tablets require reproducible dissolution and pharmacokinetic performance.

The practical barrier is therefore highest for patches, moderate for extended-release tablets, and lowest for immediate-release tablets.

What licensing deals and settlement agreements affect these drugs?

No major current licensing transaction or settlement is central to the commercial outlook for generic chlorthalidone or immediate-release clonidine hydrochloride. The original branded products and historical formulation technologies may have involved licensing, but mature generic markets generally operate through abbreviated applications, supply agreements, and distribution contracts rather than high-value molecule licenses.

Any settlement involving a newer clonidine formulation would be product-specific and would not materially alter the competitive structure of immediate-release tablets. The same applies to a chlorthalidone combination or modified-release product.

What is the financial trajectory for each drug?

Chlorthalidone

Chlorthalidone is likely to remain a stable, low-revenue generic with limited upside. Its financial trajectory has four characteristics:

1. Volume is supported by chronic hypertension treatment.
2. Unit pricing remains under pressure.
3. Revenue depends on supply continuity and contracting.
4. Margin expansion requires manufacturing or distribution efficiency rather than exclusivity.

Potential upside could come from greater adoption in guideline-driven hypertension treatment, but any volume increase would occur from a low-price base.

Clonidine hydrochloride

Clonidine has a more segmented financial trajectory:

• Immediate-release tablets: low price, high substitution, limited margin.
• Transdermal patches: higher value per prescription, but smaller patient population and greater manufacturing complexity.
• Extended-release tablets: differentiated ADHD positioning, but competition from guanfacine and stimulants.
• Hospital and specialty use: episodic demand that can benefit suppliers during shortages.

The commercial profile is more attractive for companies that can maintain approved patch or extended-release supply than for suppliers selling standard tablets alone.

What generic launch scenarios exist?

Chlorthalidone scenarios

Scenario	Market effect	Financial effect
New tablet entrant	Price erosion and share fragmentation	Lower unit revenue
Competitor exit	Temporary volume and price improvement	Higher utilization for remaining suppliers
Guideline-driven adoption	Prescription growth	Limited revenue uplift because prices remain low
Supply disruption	Short-term shortage	Potential price increase with regulatory and reputational risk
Combination-product launch	Segment migration	Reduced standalone tablet demand

Clonidine scenarios

Scenario	Market effect	Financial effect
New immediate-release tablet entrant	Rapid price competition	Lower margins
Generic patch entry	Increased substitution	Pressure on branded or incumbent patch pricing
Extended-release generic entry	Share transfer from branded product	Lower price, higher access
ADHD prescribing shift to guanfacine	Reduced clonidine demand	Structural volume decline
Shortage in another therapy	Temporary clonidine demand increase	Short-term volume benefit

What is the geographic coverage of these products?

Both drugs are available across major regulated markets, but product availability differs by country. The United States has a broad generic supply base and strong pharmacy-benefit substitution. European markets are more dependent on national reimbursement rules, tendering, and country-specific marketing authorizations. Emerging markets may have wider variation in quality standards, brand penetration, and distribution.

Geographic commercial value is highest where:

• Hypertension prevalence is high.
• Generic reimbursement is established.
• Chronic therapy adherence is supported.
• Procurement is fragmented enough to reward reliable supply.
• Regulatory approval can be obtained without extensive new clinical development.

Global revenue is difficult to attribute because manufacturers frequently combine these products with broader generic portfolios.

How strong are the patent estates for chlorthalidone and clonidine?

Dimension	Chlorthalidone	Clonidine hydrochloride
Core molecule protection	Expired	Expired
Tablet formulation protection	Weak	Weak for immediate-release; stronger historically for extended-release
Delivery-system protection	Minimal	More relevant for transdermal products
Method-of-use protection	Limited commercial impact	Product-specific, especially ADHD formulations
Biosimilar protection	Not applicable	Not applicable
Generic entry barrier	Low	Low for tablets; moderate for patches and extended-release products
Litigation exposure	Low	Low to moderate by dosage form

Overall, both estates are weak for the core oral products. Clonidine retains more formulation-driven defensibility than chlorthalidone because of its patch and extended-release formats.

Key Takeaways

• Chlorthalidone is a mature, low-price antihypertensive with stable chronic demand and limited patent-based value.
• Clonidine hydrochloride has a fragmented market spanning immediate-release tablets, transdermal patches, and extended-release ADHD products.
• Core compound patents for both drugs have expired.
• The principal commercial barriers are manufacturing reliability, formulation complexity, contracting, and regulatory compliance.
• Chlorthalidone faces strong substitution from hydrochlorothiazide and other antihypertensive classes.
• Immediate-release clonidine has weak pricing power; patches and extended-release tablets have greater differentiation.
• Public companies generally do not disclose standalone revenue for either active ingredient.
• Generic launch risk is high for standard tablets and more moderate for clonidine delivery systems.
• The best commercial opportunities are supply-constrained niches, differentiated dosage forms, and reliable low-cost manufacturing.

FAQs

Is chlorthalidone more commercially attractive than hydrochlorothiazide?

Usually not on a unit-price basis. Chlorthalidone may gain prescription share because of its longer duration of action, but hydrochlorothiazide has greater market penetration and broader generic supply.

Does clonidine still have branded revenue potential?

Limited potential remains in differentiated delivery systems and extended-release products. Immediate-release clonidine tablets have little branded pricing power because generic substitution is established.

Are chlorthalidone and clonidine subject to biosimilar competition?

No. Both are small-molecule drugs. They compete through generic drug approval pathways rather than biosimilar regulation.

Which clonidine product has the highest manufacturing barrier?

Transdermal clonidine generally has the highest barrier because the manufacturer must control adhesive performance, drug release, skin tolerability, and patch uniformity.

Can shortages materially improve revenue for these drugs?

Yes, temporarily. A shortage can shift volume and raise contract prices for remaining suppliers, but the effect is unstable and does not create durable exclusivity.

References

1. U.S. Food and Drug Administration. (2023). Kapvay (clonidine hydrochloride) extended-release tablets prescribing information. https://www.accessdata.fda.gov
2. U.S. Food and Drug Administration. (2024a). Chlorthalidone prescribing information. https://www.accessdata.fda.gov
3. U.S. Food and Drug Administration. (2024b). 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. Food and Drug Administration. (2024c). Drugs@FDA: FDA-approved drugs database. https://www.accessdata.fda.gov/scripts/cder/daf/
5. Whelton, P. K., Carey, R. M., Aronow, W. S., et al. (2018). 2017 ACC/AHA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. Hypertension, 71(6), e13-e115. https://doi.org/10.1161/HYP.0000000000000065