Last updated: October 24, 2026

Diuril is the branded form of chlorothiazide, an older thiazide diuretic used for hypertension and edema. Its commercial profile is mature: core patent protection has expired, generic chlorothiazide is available, and no meaningful product-level revenue is publicly reported by the current brand owner. Economic value is concentrated in hospital use of injectable chlorothiazide and in supply reliability rather than in brand pricing power.

What is Diuril and how is chlorothiazide used?

Diuril contains chlorothiazide, a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule. The drug is indicated for hypertension and edema associated with congestive heart failure, hepatic cirrhosis, corticosteroid therapy, and estrogen therapy.[1]

Diuril is marketed in multiple dosage forms:

Product	Active ingredient	Typical strength	Primary setting
Diuril tablets	Chlorothiazide	250 mg, 500 mg	Outpatient hypertension and edema
Diuril oral suspension	Chlorothiazide	250 mg/5 mL	Pediatric and adult use where tablets are unsuitable
Diuril Sodium injection	Chlorothiazide sodium	500 mg vial	Hospital treatment of edema and diuretic resistance

The injectable product is clinically differentiated from oral thiazides because it can be administered when oral absorption is unreliable or when patients with acute heart failure require intensified diuresis. Intravenous chlorothiazide is often used with loop diuretics, although guidelines and hospital protocols vary.

What is the FDA regulatory status of Diuril?

Diuril is an FDA-approved small-molecule drug with a long commercial history. The product is associated with legacy New Drug Application approvals dating to the early thiazide era. FDA labeling identifies chlorothiazide tablets, oral suspension, and injectable chlorothiazide sodium as prescription products.[1]

Is Diuril a biologic or biosimilar product?

No. Diuril is a conventional small-molecule drug and is regulated through the abbreviated new drug application pathway for generic versions. Biosimilar competition is not relevant.

Generic manufacturers do not file biosimilar applications for chlorothiazide. They generally rely on ANDAs demonstrating pharmaceutical equivalence and bioequivalence to the reference product.

What is the Orange Book status of Diuril?

Diuril’s commercial protection is not based on active Orange Book patent exclusivity. The original composition and product patents for chlorothiazide expired many years ago. Current generic entry is therefore governed mainly by FDA approval, manufacturing capacity, supply economics, and distributor access.

The FDA Orange Book should be used to verify the current listing status of each Diuril dosage form and any listed patents because listings can change through product transfers, discontinued-product determinations, or sponsor updates.[2]

Regulatory factor	Diuril status
Small-molecule drug	Yes
Reference-listed drug status	Yes, subject to current FDA listing
Biologic exclusivity	Not applicable
Biosimilar pathway	Not applicable
Original patent protection	Expired
Current branded patent moat	Minimal to none
Paragraph IV relevance	Limited and largely historical
Pediatric exclusivity	No commercially meaningful current exclusivity identified
Orphan exclusivity	No

What patents protect Diuril?

No active patent estate is the primary commercial barrier for Diuril. Chlorothiazide entered the market in the 1950s, and its original compound protection expired decades ago.

Are there formulation patents for Diuril?

No material, enforceable formulation moat is associated with the ordinary Diuril tablet, oral suspension, or injectable product based on the drug’s mature regulatory history. A manufacturer could theoretically obtain patents for a genuinely novel formulation or delivery system, but conventional chlorothiazide dosage forms do not have the exclusivity profile of modern modified-release products or complex injectables.

The principal barriers are operational:

validated sterile manufacturing for injectable chlorothiazide;
compliance with current good manufacturing practices;
availability of chlorothiazide API;
container-closure and stability requirements;
hospital contracting and distribution access;
FDA approval of the relevant strength and dosage form.

Are there method-of-use patents for Diuril?

Method-of-use patent risk is low. The principal indications for chlorothiazide, including hypertension and edema, are longstanding and clinically established. Broad use claims covering those indications would generally face substantial validity and prior-art challenges.

A later patent could cover a narrow dosing protocol or combination regimen, but such a patent would not recreate broad exclusivity for Diuril across the market.

When does Diuril lose exclusivity?

Diuril lost practical market exclusivity long ago. The drug’s commercial exclusivity ended when generic chlorothiazide manufacturers entered the market after expiry of the original patents and regulatory exclusivity.

Event	Approximate timing	Commercial effect
Original chlorothiazide development and launch	1950s	Established the reference product
Original patent and regulatory exclusivity period	Expired decades ago	Opened the market to generic entry
Generic tablet competition	Mature market	Reduced brand pricing power
Generic oral suspension competition	Mature but narrower market	Less crowded than tablets
Injectable competition	More constrained	Sterile manufacturing and shortages support pricing
Current market position	2020s	Mature, genericized product

An exact historic patent-expiration date is not commercially determinative because the relevant exclusivity period ended many decades ago and no current broad patent barrier controls generic entry.

Which companies are challenging Diuril through Paragraph IV filings?

No current, commercially important Paragraph IV campaign is associated with Diuril. Paragraph IV litigation is most valuable when a branded drug has remaining patent life and substantial sales. Diuril does not fit that profile.

Generic chlorothiazide entrants generally compete through ANDA approval after patent expiry or through products with no meaningful patent dispute. The absence of a current Paragraph IV contest is consistent with the drug’s age, low price, and fragmented generic market.

How large is the Diuril and chlorothiazide market?

The market is small relative to major cardiovascular and heart-failure drugs. Public company filings generally do not report Diuril revenue as a standalone line item. Companies group mature products into broader portfolios, hospital products, or generic pharmaceutical segments.

The market has three economic layers:

Oral generic chlorothiazide, which is price-sensitive and substitution-prone.
Branded Diuril tablets and suspension, which retain limited value where prescribers or pharmacies specify the branded product.
Injectable chlorothiazide, where hospital demand, supply continuity, and sterile manufacturing capacity influence pricing.

Prescription volume is structurally limited by competition from hydrochlorothiazide and chlorthalidone in hypertension. For edema and acute heart failure, chlorothiazide competes with metolazone and other adjunctive diuretics, as well as with intravenous loop diuretics such as furosemide and bumetanide.

What is the financial trajectory for Diuril?

Diuril’s likely financial trajectory is stable to declining in oral products and more volatile in the injectable segment.

Oral products

Oral chlorothiazide faces persistent price pressure because:

the active ingredient is old and available from multiple sources;
generic substitution is routine;
hypertension treatment has shifted toward lower-cost hydrochlorothiazide, chlorthalidone, ACE inhibitors, ARBs, and calcium-channel blockers;
prescribers often reserve chlorothiazide for specific edema or combination-diuretic use;
pharmacies and wholesalers prioritize acquisition cost and availability.

The branded oral franchise is therefore unlikely to generate significant growth without a supply disruption affecting generic competitors.

Injectable product

Injectable chlorothiazide has a stronger commercial position than tablets because sterile injectables have fewer qualified manufacturers and are more exposed to manufacturing interruptions. Hospitals may accept higher prices for a reliable product when alternatives are clinically imperfect or unavailable.

Revenue can rise during:

injectable diuretic shortages;
increased hospital admissions for acute decompensated heart failure;
expanded use of sequential nephron blockade;
competitor manufacturing disruptions;
distributor inventory constraints.

Revenue can fall when generic injectable supply improves or hospitals substitute oral metolazone and other diuretics.

Revenue exposure

Because product-level sales are not separately disclosed, Diuril’s financial exposure should be assessed through indirect indicators:

Indicator	Expected effect on Diuril economics
Generic chlorothiazide price erosion	Negative
Hospital injectable shortages	Positive
Oral tablet substitution by HCTZ or chlorthalidone	Negative
Heart-failure hospitalization volume	Positive for injection
New sterile injectable entrants	Negative
API or vial supply disruption	Can create short-term price upside
Brand-specific formulary preference	Limited positive effect
Patent expiry	No new impact because exclusivity is already expired

How does Diuril compare with competing diuretics?

Drug	Main commercial use	Competitive position versus Diuril
Hydrochlorothiazide	Hypertension	Lower-cost and more commonly prescribed oral thiazide
Chlorthalidone	Hypertension	Longer duration and strong guideline presence
Metolazone	Edema and diuretic resistance	Important oral adjunct in heart failure
Furosemide	Edema and acute heart failure	Dominant loop-diuretic competitor
Bumetanide	Edema and acute heart failure	Potent loop-diuretic alternative
Torsemide	Chronic heart failure and edema	Increasing clinical interest in heart failure
Chlorothiazide injection	Hospital adjunctive diuresis	Niche value when intravenous thiazide therapy is preferred

Chlorthalidone and hydrochlorothiazide are the main threats to oral Diuril in hypertension. Metolazone is a more direct alternative in refractory edema. Intravenous chlorothiazide retains a distinct hospital role because metolazone is administered orally and may be less practical in critically ill patients.

What generic launch scenarios exist for Diuril?

The market already supports generic entry, so future competition is more likely to involve supplier changes than a classic first-generic launch.

Scenario 1: Stable generic supply

Prices remain low, oral market share stays fragmented, and Diuril remains a low-growth branded product. Injectable demand remains tied to hospital formularies.

Scenario 2: Injectable shortage

A manufacturing disruption at one or more suppliers increases demand for remaining products. The injectable product gains temporary pricing power and may receive accelerated attention from hospital buyers.

Scenario 3: New low-cost entrant

A new ANDA holder enters tablets, suspension, or injection. Oral prices decline further. Injectable pricing is affected only if the entrant can maintain reliable sterile supply.

Scenario 4: Brand withdrawal

If branded economics weaken, the sponsor could reduce promotion, transfer the product, or discontinue selected dosage forms. Generic products would continue serving most demand.

What patent litigation and settlement agreements affect Diuril?

No active patent litigation or commercially significant settlement agreement is central to the current Diuril market. The drug’s patent disputes, if any, are historical and do not define current entry risk.

The relevant legal risks are more likely to involve:

FDA manufacturing enforcement;
product-quality investigations;
sterile injectable supply interruptions;
contract manufacturing disputes;
antitrust scrutiny in generic pricing;
product liability claims concerning electrolyte abnormalities or renal effects.

How strong is the Diuril patent estate?

The patent estate is weak as a source of current exclusivity but irrelevant to supply-side defensibility.

Dimension	Assessment
Composition-of-matter protection	Expired
Formulation protection	Limited
Method-of-use protection	Limited
Orange Book leverage	Minimal
Paragraph IV litigation risk	Low
Manufacturing complexity	Moderate for injection
Switching barriers	Low for oral products; higher in hospital protocols
Brand pricing power	Low
Supply-chain value	Moderate, particularly for injection

The strongest commercial asset is not patent exclusivity. It is the ability to manufacture and distribute an approved sterile injectable product consistently.

What geographic coverage does Diuril have?

Diuril and chlorothiazide products have broad international therapeutic relevance, but brand availability varies by country. Generic chlorothiazide products may be sold under local brand names or only as nonproprietary medicines.

The United States is the most relevant market for Orange Book, ANDA, hospital shortage, and branded Diuril analysis. European and other markets are generally more exposed to national reimbursement controls, tender purchasing, and local generic substitution. Global revenue cannot be inferred from U.S. product positioning.

Key Takeaways

Diuril is the branded chlorothiazide product and has been commercially available since the 1950s.
Original patent and regulatory exclusivity expired decades ago.
No active patent estate materially protects current Diuril sales.
Biosimilar competition is not relevant because chlorothiazide is a small molecule.
Oral Diuril faces strong competition from hydrochlorothiazide, chlorthalidone, and metolazone.
Injectable chlorothiazide has greater commercial resilience because sterile manufacturing and hospital supply are more constrained.
Product-level Diuril revenue is not separately disclosed in standard public company reporting.
The financial trajectory is likely flat to declining for oral products, with episodic upside for injection during shortages.
Current generic-entry risk is operational rather than patent-driven.
FDA manufacturing status, supply continuity, and hospital contracting matter more than patent litigation.

Frequently Asked Questions

Is Diuril still patented?

No active broad patent protection is the principal commercial barrier for Diuril. The original chlorothiazide patents expired decades ago.

Is chlorothiazide the same as hydrochlorothiazide?

No. Both are thiazide diuretics, but chlorothiazide and hydrochlorothiazide are different active ingredients with different dosing, potency, and prescribing patterns.

Can generic manufacturers substitute chlorothiazide for Diuril?

Pharmacists may substitute an FDA-approved therapeutically equivalent generic product when permitted by state law, payer rules, and the prescription. Substitution depends on the exact dosage form and strength.

Why is injectable Diuril more commercially valuable than tablets?

Injectable chlorothiazide has fewer qualified suppliers and is used in hospitals where oral administration may be impractical. Sterile manufacturing requirements create a higher supply barrier than tablet production.

Does Diuril have exclusivity for heart-failure treatment?

No current broad exclusivity protects Diuril for heart failure. Its use in edema and heart failure is based on established labeling and clinical practice, not modern method-of-use exclusivity.

References

U.S. Food and Drug Administration. (n.d.). Diuril (chlorothiazide) prescribing information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/
Heidenreich, P. A., Bozkurt, B., Aguilar, D., et al. (2022). 2022 AHA/ACC/HFSA guideline for the management of heart failure. Circulation, 145(18), e895-e1032. https://doi.org/10.1161/CIR.0000000000001063
U.S. Food and Drug Administration. (n.d.). Approved drug product list and patent information. https://www.fda.gov/drugs/development-resources/drug-approvals-and-databases

US Patents:	0
Applicants:	2
NDAs:	2
Finished Product Suppliers / Packagers:	1
Raw Ingredient (Bulk) Api Vendors:	90
Clinical Trials:	2
Patent Applications:	4,329
Drug Prices:	Drug price information for DIURIL
What excipients (inactive ingredients) are in DIURIL?	DIURIL excipients list
DailyMed Link:	DIURIL at DailyMed

Sponsor	Phase
University of Virginia	Phase 4
Vanderbilt University	Phase 4

Drug Class	Thiazide Diuretic
Physiological Effect	Increased Diuresis

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Rising	DIURIL	chlorothiazide sodium	INJECTABLE;INJECTION	011145-005	Approved Prior to Jan 1, 1982		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
Rising	DIURIL	chlorothiazide	TABLET;ORAL	011145-002	Approved Prior to Jan 1, 1982		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
Salix Pharms	DIURIL	chlorothiazide	SUSPENSION;ORAL	011870-001	Approved Prior to Jan 1, 1982		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
Rising	DIURIL	chlorothiazide	TABLET;ORAL	011145-004	Approved Prior to Jan 1, 1982		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Exclusivity Expiration

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