CHLOROTHIAZIDE AND RESERPINE Drug Patent Profile

Which patents cover Chlorothiazide And Reserpine, and when can generic versions of Chlorothiazide And Reserpine launch?

Chlorothiazide And Reserpine is a drug marketed by Hikma and is included in two NDAs.

The generic ingredient in CHLOROTHIAZIDE AND RESERPINE is chlorothiazide; reserpine. There are forty-two drug master file entries for this compound. Additional details are available on the chlorothiazide; reserpine profile page.

Summary for CHLOROTHIAZIDE AND RESERPINE

US Patents:	0
Applicants:	1
NDAs:	2

US Patents and Regulatory Information for CHLOROTHIAZIDE AND RESERPINE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Hikma	CHLOROTHIAZIDE AND RESERPINE	chlorothiazide; reserpine	TABLET;ORAL	088557-001	Dec 22, 1983		DISCN	No	No
Hikma	CHLOROTHIAZIDE AND RESERPINE	chlorothiazide; reserpine	TABLET;ORAL	088365-001	Dec 22, 1983		DISCN	No	No

Chlorothiazide and Reserpine Investment Analysis: Market Status, Patent Risk, and Commercial Outlook

Last updated: July 31, 2026

Chlorothiazide and reserpine is a legacy antihypertensive combination with limited commercial value. The product has no meaningful modern patent moat, no biosimilar exposure, weak generic-entry barriers, and no visible growth pathway in current hypertension treatment. Chlorothiazide remains commercially available as a diuretic, and reserpine remains an inexpensive generic drug, but the fixed-dose combination is not a significant current pharmaceutical asset.

What is chlorothiazide and reserpine?

Chlorothiazide is a thiazide diuretic that lowers blood pressure by increasing renal sodium and water excretion. Reserpine is a centrally acting sympatholytic that reduces catecholamine stores. The combination was developed for hypertension before modern therapies such as ACE inhibitors, angiotensin receptor blockers, calcium-channel blockers, and beta blockers became standard.

Historical combination products included reserpine and chlorothiazide tablets in different strengths. The product was marketed under legacy brands including Diupres, although current commercial availability is limited or absent in major markets.

Attribute	Assessment
Active ingredients	Chlorothiazide and reserpine
Therapeutic class	Antihypertensive combination
Dosage form	Immediate-release oral tablet
Current role	Legacy or discontinued combination
Regulatory pathway	Older small-molecule drug approval
Biosimilar relevance	None
Generic competition	High
Patent position	No material current exclusivity identified
Commercial attractiveness	Low
Primary remaining value	Generic ingredient supply, historical IP, or niche institutional use

The product’s clinical limitations include electrolyte abnormalities, orthostatic hypotension, depression and central nervous system effects associated with reserpine, and a less favorable tolerability profile than newer antihypertensive combinations. Current treatment guidelines generally favor other drug classes for initial and combination therapy.

What is the FDA status of chlorothiazide and reserpine?

The fixed-dose chlorothiazide-reserpine combination does not have the regulatory profile of a currently promoted branded product. Current U.S. drug databases separately recognize chlorothiazide and reserpine products, while the historical combination has little visible commercial activity.

Chlorothiazide FDA status

Chlorothiazide remains available in the United States as a prescription thiazide diuretic. Diuril is the principal branded reference product, with generic chlorothiazide products also marketed. The drug is available in oral tablets and oral suspension, and injectable chlorothiazide is used in selected clinical settings. Current labeling covers hypertension and edema indications (DailyMed, n.d.-a).

Reserpine FDA status

Reserpine is an old prescription antihypertensive. It is available primarily as a generic product and has limited use because of adverse-effect concerns and the availability of better tolerated alternatives. Current labeling includes hypertension, but clinical utilization is low relative to contemporary antihypertensive classes (DailyMed, n.d.-b).

Combination-product status

The combination should be treated as a legacy product rather than a current branded growth asset. The FDA Orange Book is the principal source for active approved drug products, patent listings, and exclusivity. A historical product that is no longer marketed does not create a current commercial franchise merely because its original approval remains part of the regulatory record (FDA, 2024a).

When does chlorothiazide and reserpine lose exclusivity?

The combination lost meaningful market exclusivity decades ago. Its underlying active ingredients were discovered and commercialized in the mid-20th century, placing their original composition and formulation patents well outside the ordinary patent term.

For U.S. patents filed before June 8, 1995, the relevant term was generally 17 years from issuance. For later applications, the standard term is generally 20 years from the earliest effective nonprovisional filing date, subject to adjustments and extensions. No plausible active U.S. patent term remains for the original chlorothiazide-reserpine combination based on its historical development period (USPTO, n.d.).

Exclusivity category	Current assessment
Original composition patents	Expired
Original combination patents	Expired or commercially irrelevant
Regulatory exclusivity	Expired
Orphan-drug exclusivity	Not applicable
Pediatric exclusivity	Not applicable
New chemical entity exclusivity	Expired
Biosimilar exclusivity	Not applicable
Current Orange Book patent moat	None of commercial significance

A company launching a modern generic version would not face the patent barriers associated with a recently approved branded drug. The principal requirements would be formulation development, bioequivalence or applicable approval evidence, manufacturing compliance, and commercial distribution.

What patents protect chlorothiazide and reserpine?

No active patent estate of material investment significance is associated with the historical combination. The relevant early patents covering chlorothiazide, reserpine, and their formulations are long expired.

Composition and active-ingredient patents

Chlorothiazide is an established small molecule. Reserpine is also an established active ingredient with a long history of pharmaceutical use. The original compound patents cannot support current exclusivity.

Combination patents

Historical combination patents may have covered the use of reserpine with a thiazide diuretic or a particular tablet formulation. Their age makes current enforceability commercially immaterial. A patent covering the same active ingredients would need a live term and a non-obvious claim scope to block a modern entrant. The historical combination does not meet that profile.

Formulation patents

The product is an immediate-release tablet. Standard tablet manufacturing, blending, granulation, compression, and coating processes generally do not create a durable barrier for a legacy product. A new formulation patent could theoretically be pursued for a specific controlled-release system, but it would protect the redesigned formulation, not the historical combination itself.

Method-of-use patents

The historical hypertension indication is too old to support a current method-of-use monopoly. A new patent would require a genuinely novel, non-obvious use supported by clinical evidence. No established commercial method-of-use franchise is associated with the combination.

How many patents cover chlorothiazide and reserpine?

The commercially relevant number is effectively zero for active U.S. exclusivity covering the historical combination. Historical patent records may contain multiple documents relating to the ingredients, manufacturing processes, formulations, or therapeutic uses, but expired patents do not provide a current investment moat.

Patent-count analysis should separate:

1. Historical patents that have expired.
2. Active patents listed in the Orange Book.
3. Pending applications with commercially meaningful claim scope.
4. Patents covering only a different formulation or use.

For chlorothiazide and reserpine, the first category dominates. The second and third categories do not appear to create a material barrier to generic competition. A raw count of historical patents would overstate the strength of the estate.

What is the Orange Book status of chlorothiazide and reserpine?

The Orange Book may contain current listings for approved chlorothiazide products, particularly branded or generic products associated with chlorothiazide as a single active ingredient. That status should not be confused with an active patent position for the old reserpine combination.

Orange Book issue	Commercial implication
Single-ingredient chlorothiazide listings	Support continued generic competition
Historical combination product	Limited current commercial relevance
Listed patents	Any active listing must be reviewed product by product
Pediatric exclusivity	Not expected to affect the legacy combination
Reference listed drug status	Relevant only if a sponsor seeks current approval
Patent certification	Potentially relevant to any new ANDA, but no known major barrier

The FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations remains the controlling reference for active U.S. listings and therapeutic-equivalence designations (FDA, 2024a). Product status can change through approval, discontinuation, or manufacturer withdrawal.

Which companies are challenging chlorothiazide and reserpine?

Generic competition has already displaced the branded value of the combination. The competitive field is not centered on a specific Paragraph IV challenger against a valuable reference product. It consists primarily of generic manufacturers and distributors supplying the individual ingredients or legacy equivalents.

Paragraph IV risk

A Paragraph IV certification would be commercially relevant only if an applicant were seeking approval against an active reference product with unexpired Orange Book patents. The historical combination does not present the typical high-value Paragraph IV profile seen with newer branded therapies.

Potential entrant risks include:

• No meaningful composition-of-matter patent barrier.
• No credible long-duration formulation exclusivity.
• Limited switching costs for prescribers and pharmacies.
• Potentially low market size that discourages multiple applicants.
• Manufacturing and supply economics that may matter more than litigation.

Generic manufacturer profile

Potential competition would come from established generic manufacturers, contract manufacturers, and specialty suppliers rather than from innovative pharmaceutical companies. The principal differentiators would be product availability, manufacturing cost, quality systems, wholesaler access, and regulatory compliance.

What patent litigation affects chlorothiazide and reserpine?

No major current patent litigation is associated with the historical chlorothiazide-reserpine combination. The product does not have the revenue scale or remaining patent life that typically supports high-value Hatch-Waxman litigation.

Settlement agreements

No commercially significant current settlement framework is associated with the combination. In a modern branded-drug case, a settlement could delay generic entry through a negotiated launch date, license, or supply agreement. That structure is not central to this legacy product.

Litigation risk assessment

Litigation category	Risk level
Composition patent litigation	Negligible
Formulation patent litigation	Low
Method-of-use litigation	Low
Paragraph IV challenge	Low-value, technically possible
Trademark litigation	Low
Manufacturing trade-secret disputes	Low to moderate in a specific supplier relationship
Product-liability exposure	More relevant than patent litigation

The absence of patent litigation does not guarantee commercial success. It reflects the product’s age, low market value, and limited strategic importance.

What formulation patents protect chlorothiazide and reserpine?

No current formulation moat is evident for the standard immediate-release tablet. The combination uses conventional small-molecule dosage technology, and generic manufacturers can generally reproduce the dosage form without infringing expired historical claims.

A company could attempt to create a differentiated product based on:

• Modified-release reserpine delivery.
• A lower-dose combination intended to reduce adverse effects.
• A fixed-dose tablet with improved dose uniformity.
• A combination designed for adherence in resistant hypertension.
• A specialty formulation for patients unable to use first-line therapies.

These approaches would require clinical, regulatory, and commercial validation. A new patent would not automatically create a valuable asset. Reserpine’s limited modern use would constrain the commercial return on formulation investment.

How does chlorothiazide and reserpine compare with modern antihypertensive drugs?

The combination is disadvantaged by efficacy, tolerability, guideline positioning, and commercial support.

Product class	Current clinical position	Patent or exclusivity profile	Commercial outlook
Chlorothiazide-reserpine	Legacy therapy	Expired	Very limited
Hydrochlorothiazide combinations	Widely used generics	Expired	Stable, low margin
ACE inhibitor combinations	Common first-line or add-on therapy	Mostly generic	Large generic market
ARB combinations	Widely used	Mostly generic	Stronger demand
Calcium-channel blocker combinations	Common hypertension therapy	Mostly generic	High prescription relevance
Fixed-dose triple combinations	Growing adherence focus	Some newer products	Selective commercial opportunity
Mineralocorticoid receptor antagonists	Used in resistant hypertension	Mostly generic or specialty	Niche growth
Novel hypertension agents	Targeted populations	Potential active IP	Higher development value

Chlorothiazide itself retains clinical utility as a thiazide diuretic. Reserpine is the limiting component. Its adverse-effect profile and reduced guideline relevance weaken the combination’s prospects.

What is the revenue exposure for chlorothiazide and reserpine?

There is no clear public product-level revenue stream for the historical fixed-dose combination. Any investment model should therefore avoid assigning branded-drug revenue multiples to the product.

Revenue drivers

Potential revenue would depend on:

• Whether an approved combination product remains actively marketed.
• The number of manufacturers.
• Prescription volume.
• Reimbursement status.
• Wholesale acquisition price.
• Manufacturing cost for a low-volume tablet.
• Hospital or institutional demand.
• Availability of cheaper alternative therapies.

Revenue scenario

Scenario	Commercial result
Legacy product remains available through a small supplier	Low, stable niche revenue
New generic entrant launches	Price erosion and limited share
Reformulated product gains approval	High development risk and uncertain uptake
Product obtains institutional or international demand	Possible niche opportunity
Branded relaunch for general hypertension	Low probability of economic success

The combination lacks the market characteristics that support substantial revenue growth. A relaunch would face low pricing, weak physician demand, limited reimbursement differentiation, and competition from numerous generic antihypertensives.

What manufacturing and intellectual-property barriers exist?

Manufacturing barriers are more relevant than patent barriers. Chlorothiazide and reserpine are established small molecules, but reserpine may present practical challenges involving sourcing, process control, stability, assay sensitivity, and dose uniformity at low concentrations.

Manufacturing considerations

A prospective manufacturer would need to address:

• Qualified API suppliers.
• Impurity and degradation-product controls.
• Content uniformity for low-dose reserpine.
• Stability under humidity and temperature stress.
• Validated analytical methods.
• GMP compliance.
• Bioequivalence or applicable regulatory evidence.
• Reliable packaging and distribution.

These requirements can restrict the number of suppliers even when the product is legally open to competition. They do not amount to a durable IP barrier.

Geographic coverage

The commercial position varies by jurisdiction:

Region	Likely position
United States	Legacy combination; individual ingredients have generic availability
European Union	Limited relevance and fragmented national status
India	Greater availability of legacy antihypertensive combinations possible
Latin America	Country-specific generic and legacy-brand presence
Africa and other emerging markets	Possible institutional or low-cost use, subject to local registration

Patent expiration is broadly global for the historical products, but regulatory approval, local registration, procurement policy, and API supply determine practical market access.

How strong is the patent estate for chlorothiazide and reserpine?

The patent estate is weak.

Patent-strength factor	Assessment
Composition-of-matter protection	Absent due to age
Remaining patent term	None of material value
Formulation differentiation	Limited
Method-of-use protection	Weak
Manufacturing know-how	Potentially useful but non-exclusive
Freedom to operate	Generally favorable for generic entry
Litigation leverage	Minimal
Licensing value	Low

The only potentially defensible value would come from a new formulation, a specialized indication, proprietary manufacturing process, or a regulated market with limited supplier competition. None is inherent in the historical combination.

What generic launch risks exist?

A generic launch would face low legal risk but uncertain commercial returns.

Legal and regulatory risks

The main risks would involve:

• Product-specific Orange Book status.
• Reference-product selection.
• Bioequivalence requirements.
• Labeling differences.
• Manufacturing inspection findings.
• API qualification.
• Market withdrawal or shortage-related regulatory action.

Patent risk is secondary. A sponsor would still need to confirm current FDA records before submitting an ANDA or other application because regulatory status can differ between historical products and active reference listings (FDA, 2024a; FDA, 2024b).

Commercial risks

The market could be unattractive even with a successful approval. A small number of prescriptions may not support regulatory, manufacturing, pharmacovigilance, and distribution costs. If several generic suppliers enter, rapid price erosion would be likely.

What licensing deals could create value?

A conventional licensing deal for the historical combination is unlikely to attract significant upfront payments. Potentially viable structures would be narrower:

• Regional rights in markets where the combination remains registered.
• Supply agreements for institutional procurement.
• Licensing of a reformulated low-dose product.
• Contract manufacturing and private-label distribution.
• Combination rights for a broader resistant-hypertension platform.
• Rights to a proprietary analytical or manufacturing process.

The commercial value would depend on the partner’s distribution network and on evidence that the product has continuing demand. The expired historical IP alone would not justify a premium license.

What is the investment outlook for chlorothiazide and reserpine?

The base-case investment view is negative for branded development and neutral-to-low for generic manufacturing.

Base case

The combination remains a low-volume legacy product. Chlorothiazide retains value as an individual diuretic, but reserpine limits the attractiveness of the fixed-dose product.

Bull case

A niche opportunity could emerge if a sponsor secures a low-cost manufacturing position, obtains registration in an underserved market, or develops a clinically differentiated formulation. This would be a specialty-generic or regional play, not a conventional pharmaceutical growth investment.

Bear case

The product becomes commercially irrelevant as prescribers favor newer antihypertensive combinations, suppliers discontinue low-volume manufacturing, and reimbursement systems favor cheaper or guideline-preferred alternatives.

Investment factor	Rating
Market growth	Poor
Pricing power	Very poor
Patent protection	None of significance
Regulatory complexity	Moderate
Generic competition	High
Clinical differentiation	Poor
Manufacturing opportunity	Possible but narrow
Licensing potential	Low
Litigation upside	Minimal
Overall investment quality	Low

Key Takeaways

• Chlorothiazide and reserpine is a legacy antihypertensive combination with limited current commercial relevance.
• Chlorothiazide remains clinically and commercially useful as an individual drug; reserpine is the weaker component.
• Original composition, combination, and formulation patents are expired or commercially immaterial.
• No meaningful current patent moat, biosimilar risk, or high-value Paragraph IV litigation profile exists.
• Generic entry would face regulatory and manufacturing requirements but little patent resistance.
• Product-level revenue is not publicly established as a significant current commercial stream.
• The most plausible opportunity is a low-cost regional generic, institutional supply arrangement, or differentiated reformulation.
• A branded relaunch for broad hypertension treatment has poor risk-adjusted economics.

FAQs

Is chlorothiazide and reserpine still marketed in the United States?

The historical fixed-dose combination has limited current visibility and should be treated as a legacy product. Chlorothiazide and reserpine remain separately recognized generic medicines.

Does chlorothiazide and reserpine have Orange Book exclusivity?

No meaningful current exclusivity is associated with the historical combination. Any active Orange Book status must be assessed against the specific product and application number.

Can a generic company still launch chlorothiazide and reserpine?

Potentially, subject to an appropriate FDA application, reference-product requirements, manufacturing compliance, and applicable bioequivalence standards. The primary challenge would be commercial viability rather than patent clearance.

Is reserpine protected by any active pharmaceutical patent?

The original reserpine patents are historical and expired. A new patent would require a novel formulation, manufacturing process, or therapeutic use with sufficient technical and clinical support.

Would a reformulated chlorothiazide-reserpine product be investable?

Only in a narrow specialty or regional strategy. A reformulation could create new IP, but clinical demand, safety concerns, reimbursement, and competition from modern antihypertensive therapies would remain substantial constraints.

References

1. DailyMed. (n.d.-a). Diuril: Chlorothiazide sodium tablet and suspension prescribing information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/

2. DailyMed. (n.d.-b). Reserpine tablet prescribing information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/

3. U.S. Food and Drug Administration. (2024a). 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. (2024b). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/

5. U.S. Patent and Trademark Office. (n.d.). Patent term adjustment and patent term calculation. https://www.uspto.gov/patents/laws/patent-term-calculator