List of Excipients in Branded Drug ALDACTAZIDE

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	CALCIUM SULFATE
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	FERRIC OXIDE RED
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	HYDROXYPROPYL CELLULOSE
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	HYPROMELLOSE
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	MAGNESIUM STEARATE
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	POLYETHYLENE GLYCOL
Pfizer Laboratories Div Pfizer Inc	ALDACTAZIDE	spironolactone and hydrochlorothiazide	0025-1011	POVIDONE

Aldactazide Excipient Strategy and Commercial Opportunities

Last updated: September 24, 2026

Aldactazide is the fixed-dose combination of spironolactone and hydrochlorothiazide. Its commercial opportunity is primarily generic and lifecycle-oriented rather than based on active patent exclusivity. The product combines a potassium-sparing aldosterone antagonist with a thiazide diuretic, creating formulation challenges involving content uniformity, dissolution, moisture control, taste, tablet size, and chronic-use tolerability. The strongest opportunities are optimized generic tablets, authorized-generic supply, lower-dose presentations, pharmacy-channel products, and differentiated solid oral formulations.

What is Aldactazide and what strengths are marketed?

Aldactazide contains spironolactone and hydrochlorothiazide in a fixed-dose tablet. Historical U.S. strengths include:

Product	Spironolactone	Hydrochlorothiazide	Dosage form
Aldactazide 25	25 mg	25 mg	Oral tablet
Aldactazide 50	50 mg	50 mg	Oral tablet

The combination is used when diuresis is required while reducing the potassium loss associated with hydrochlorothiazide monotherapy. The product label identifies indications including edema associated with congestive heart failure, hepatic cirrhosis with ascites and edema, nephrotic syndrome, and hypertension in selected patients. The combination is not interchangeable on a milligram-for-milligram basis with either component alone because spironolactone and hydrochlorothiazide have different pharmacologic and dose-response profiles (U.S. Food and Drug Administration [FDA], 2018).

Spironolactone is poorly water soluble and has variable bioavailability. Hydrochlorothiazide is more water soluble but is administered at a much lower mass in some combination products. These differences make powder blending and dissolution control central to product development.

What excipients are used in Aldactazide tablets?

Historical Aldactazide labeling identifies conventional tablet excipients, including lactose, corn starch, magnesium stearate, polyvinylpyrrolidone, calcium sulfate, talc, and colorants, although the exact composition can vary by strength, manufacturing site, and label version. The active ingredients and inactive ingredients should be confirmed against the applicable current product label and regulatory database before a filing or litigation position is taken.

Functional role of the main excipient classes

Excipient class	Likely function	Relevance to Aldactazide
Lactose or another soluble diluent	Tablet mass and compression	Supports manufacturability but creates lactose-intolerance and supply-chain considerations
Corn starch	Diluent and disintegrant	Helps tablet breakup and can improve wet granulation
Povidone	Binder	Supports granule strength and content uniformity
Calcium sulfate	Diluent and compressibility aid	Can improve tablet robustness in low-dose combinations
Magnesium stearate	Lubricant	Required for ejection but can slow wetting and dissolution if overused
Talc or colloidal silica	Glidant or antiadherent	Improves powder flow and reduces sticking
Colorants	Product identification	Useful for strength differentiation and brand recognition
Film-coating polymers	Protection and swallowability	Could improve moisture protection, taste, and visual differentiation

The most important excipient issue is not the identity of one inactive ingredient. It is the interaction between excipient level, granulation method, lubricant exposure, and the dispersion of two active ingredients with different physicochemical properties.

What excipient strategy is best for a generic Aldactazide tablet?

A robust generic strategy should prioritize content uniformity, dissolution similarity, stability, and scalable compression. A direct-compression formulation may reduce processing steps, but wet granulation can provide better control where spironolactone segregation or poor flow affects dose uniformity.

Direct-compression strategy

Direct compression can use a co-processed filler-disintegrant system with a small quantity of glidant and lubricant. It offers:

• Lower equipment and processing costs
• Reduced exposure to heat and water
• Shorter manufacturing cycle times
• Easier scale-up for high-volume generic production

The principal risk is segregation. The two active ingredients differ in particle density, particle size, and dose fraction. Spironolactone represents a larger share of tablet mass than hydrochlorothiazide, but hydrochlorothiazide may still segregate if its particle-size distribution differs materially from the excipient blend.

Particle engineering, deagglomeration, ordered mixing, and controlled transfer are more important than simply increasing mixing time. Excessive mixing can worsen lubricant coating and reduce tablet wetting.

Wet-granulation strategy

Wet granulation is preferable when the development batch shows:

• Poor flow
• High tablet-weight variability
• Low hydrochlorothiazide content uniformity
• Capping or lamination
• Inadequate mechanical strength
• Unacceptable dissolution after lubrication

Povidone or a comparable binder can improve granule strength. The process must control water addition and drying temperature because spironolactone is sensitive to formulation and process conditions that can affect dissolution and stability.

A split-granulation approach may be appropriate when the two active ingredients have incompatible particle characteristics. Separate granulation of one active with selected excipients, followed by final blending, can improve distribution but adds process complexity and validation burden.

Which excipients create the largest technical risks?

Lubricant overuse

Magnesium stearate is necessary for tablet ejection, but excessive concentration or excessive blending can form a hydrophobic film around particles. This can delay disintegration and reduce spironolactone dissolution. Development should establish a defined lubrication endpoint rather than rely only on fixed mixing time.

Lactose selection

Lactose monohydrate and anhydrous lactose differ in moisture content, compactability, and dissolution behavior. A lactose-based formula can be commercially attractive because of cost and availability, but the formulation should address:

• Residual moisture
• Maillard-type compatibility concerns with amine-containing materials
• Tablet hardness drift
• Storage-related dissolution changes

A lactose-free version using microcrystalline cellulose, mannitol, dibasic calcium phosphate, or a co-processed filler may support a differentiated product, although it may require new bioequivalence and stability work.

Disintegrant selection

Corn starch is a conventional choice, but crospovidone, croscarmellose sodium, or sodium starch glycolate can provide faster and more reproducible disintegration. The best choice depends on whether the product is made by direct compression or granulation.

High disintegrant levels can reduce tablet strength or increase friability. A dual-location strategy, with part of the disintegrant intragranular and part extragranular, may improve both robustness and breakup.

Colorants and coating systems

Color can differentiate 25/25 and 50/50 strengths and reduce dispensing errors. A film coat can also reduce chalkiness and improve swallowability. However, colorants and coating polymers add regulatory complexity, especially in markets with restrictions on specific dyes.

A thin, low-moisture film coat is more suitable than an aqueous coating process that creates unnecessary water exposure. The coating should not materially delay disintegration or alter dissolution relative to the reference product.

What formulation patents protect Aldactazide?

Aldactazide was introduced decades ago, and its original product protection has expired. The commercial opportunity is therefore unlikely to depend on an active composition-of-matter patent covering the spironolactone/hydrochlorothiazide combination.

The relevant IP categories are:

IP category	Commercial relevance
Original combination patent	Historical importance; generally expired because of product age
Formulation patent	Potentially relevant only if a later, separately claimed formulation was developed
Method-of-use patent	Limited value for a mature combination unless tied to a narrow new indication
Manufacturing patent	May protect a specific process but usually does not block conventional generic manufacture
Trademark rights	Aldactazide name and branding may remain controlled even when generic entry is available
Trade secrets	Process parameters, blend order, granulation endpoint, and coating conditions may retain value

A sponsor should distinguish between patents covering Aldactazide as a branded product and patents covering a later formulation or manufacturing process. A formulation patent would need to claim a specific excipient system, dissolution profile, particle-engineering approach, or process condition. Broad claims to the combination itself would face substantial validity and expiration issues given the product’s age.

What is the FDA regulatory status of Aldactazide?

Aldactazide is an approved prescription combination product in the United States. Regulatory work for a new generic version would generally proceed through an Abbreviated New Drug Application if an applicable reference-listed drug and product-specific requirements are satisfied.

Key regulatory considerations include:

• Pharmaceutical equivalence to the reference product
• Bioequivalence under the applicable FDA product-specific guidance
• Demonstration of assay and content uniformity for both active ingredients
• Comparative dissolution
• Stability under ICH conditions
• Evaluation of degradation products
• Labeling consistency
• Compliance with current good manufacturing practice
• Assessment of spironolactone-related impurities and hydrochlorothiazide degradation

A product may face additional scrutiny if it uses a substantially different excipient system, a novel release profile, a nontraditional manufacturing process, or a dosage form that changes the reference product’s performance.

What is the Orange Book status of Aldactazide?

The Orange Book is the principal U.S. source for approved drug products, reference-listed-drug designations, therapeutic equivalence codes, patent listings, and exclusivity data. For a mature product such as Aldactazide, the central commercial issue is usually whether an active patent or regulatory exclusivity period remains, not whether the original combination has continuing market protection.

The expected patent profile is:

Question	Assessment
Active composition-of-matter protection	Not expected for this mature combination
New chemical entity exclusivity	Expired
Pediatric exclusivity	No material current barrier expected
Listed formulation patents	Must be checked against the current Orange Book entry
Paragraph IV exposure	Relevant only if a listed patent remains and is certified
Generic approval pathway	Potentially available through an ANDA, subject to reference-product requirements

An Orange Book review should be performed using the current FDA listing because patent listings, discontinued-product status, and reference-product designations can change. The regulatory record should be reconciled with FDA’s Drugs@FDA database and the current product label (FDA, n.d.-a; FDA, n.d.-b).

When did Aldactazide lose exclusivity?

Aldactazide’s original regulatory and patent exclusivity expired long before the current generic market. The product’s age means that market entry is generally constrained by:

• Reference-product availability
• Commercial demand
• Manufacturing economics
• Bioequivalence execution
• Distribution access
• Supply reliability

The absence of meaningful current exclusivity does not eliminate commercial risk. A generic developer can still encounter a low-volume market, limited wholesaler interest, or competition from separate spironolactone and hydrochlorothiazide tablets.

How many patents cover Aldactazide?

The answer depends on whether the analysis includes expired historical patents, currently listed Orange Book patents, process patents, foreign rights, and patents covering separate active ingredients. For commercial freedom-to-operate purposes, the relevant question is whether any unexpired patent claims the marketed combination, a required formulation, or a manufacturing process that the applicant must use.

For a mature Aldactazide generic, the practical IP exposure is likely to be low compared with newer fixed-dose combinations. A complete patent count cannot be stated without a current patent-family search and Orange Book reconciliation. The strategic conclusion remains clear: the principal barrier is regulatory and commercial execution rather than basic compound exclusivity.

What Paragraph IV challenges affect Aldactazide?

Paragraph IV certification applies when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or not infringed. It is meaningful only if an unexpired patent is listed for the reference product.

Because Aldactazide is an old combination, a new applicant would more likely face:

• No patent challenge because no relevant patent remains listed
• A Paragraph III certification if a later patent remains valid but has a defined expiration date
• A Paragraph IV certification against a narrow formulation or method patent
• Administrative issues involving reference-product and discontinued-product status

The first applicant to file a substantially complete ANDA with a qualifying Paragraph IV certification could receive 180-day generic exclusivity if the statutory requirements are met. That opportunity is product-specific and cannot be assumed without reviewing FDA’s current regulatory record and litigation docket.

What generic entry risks exist for Aldactazide?

The largest generic-entry risks are operational rather than patent-based.

Bioequivalence risk

Spironolactone has relatively low and variable aqueous solubility. A formulation that passes routine assay testing may still fail comparative dissolution or pharmacokinetic bioequivalence. The developer should control:

• Active particle size
• Polymorphic or solid-state characteristics
• Granule porosity
• Lubrication time
• Tablet hardness
• Disintegration
• Dissolution across pH conditions

Commercial substitution risk

Physicians and pharmacists may substitute separate spironolactone and hydrochlorothiazide products. This creates a ceiling on demand for a fixed-dose product. Aldactazide can still compete where pill burden, adherence, or established prescribing habits favor the combination.

Safety-related prescribing constraints

Spironolactone is associated with hyperkalemia and renal-function concerns. Hydrochlorothiazide can produce electrolyte abnormalities and metabolic effects. These safety considerations may limit broad switching and reduce demand for chronic fixed-dose use in some patient populations.

What commercial opportunities exist for Aldactazide excipients?

Low-cost generic tablet

The lowest-risk opportunity is a conventional immediate-release tablet using established excipients, standard compression equipment, and a formulation close to the reference product. The value proposition is supply reliability and low cost rather than technical differentiation.

Lactose-free product

A lactose-free tablet can target patients and institutions seeking broader excipient compatibility. Suitable fillers include microcrystalline cellulose, mannitol, and dibasic calcium phosphate. The product would need to demonstrate acceptable dissolution and bioequivalence.

Smaller tablet or lower-dose presentation

A smaller tablet could improve swallowability and reduce inactive-ingredient burden. This is commercially relevant for older patients taking multiple cardiovascular medicines. The main challenge is maintaining content uniformity when the total active mass is relatively high compared with tablet weight.

Taste-masked or film-coated tablet

A film coat can improve patient acceptability, reduce powdering, and provide strength differentiation. It is unlikely to create strong patent protection by itself, but it may support a branded-generic position.

Unit-dose and institutional packaging

Blister packaging, calendar packs, and unit-dose formats can support nursing facilities, hospital formularies, and adherence programs. Moisture-barrier packaging may be useful if stability data show sensitivity to humidity.

Combination-product supply agreements

A manufacturer could pursue private-label, authorized-generic, or contract-manufacturing agreements with regional pharmacies, wholesalers, and institutional suppliers. The product’s mature status makes manufacturing cost, fill rate, and regulatory reliability more important than premium pricing.

How does Aldactazide compare with separate spironolactone and hydrochlorothiazide?

Factor	Aldactazide	Separate tablets
Pill burden	Lower	Higher
Dose flexibility	Limited to fixed ratios	High
Manufacturing complexity	Higher than a single active	Distributed across products
Pharmacologic tailoring	Less flexible	More flexible
Adherence potential	Better where ratio is appropriate	Depends on regimen
Generic competition	Mature combination market	Broad competition for each component
Patent exposure	Low for old combination	Low for old individual drugs
Commercial differentiation	Formulation, packaging, supply	Price and availability

The fixed-dose product has a narrower clinical fit because the prescriber cannot independently adjust the two components. Its commercial advantage is convenience, not therapeutic flexibility.

How strong is the Aldactazide patent estate?

The Aldactazide patent estate is likely weak as a barrier to conventional generic entry because the product is old and its principal active ingredients are long-established. Any remaining value would likely reside in:

• A later formulation claim
• A process claim
• A packaging or delivery claim
• Brand recognition
• Manufacturing know-how
• Regulatory positioning

These rights are generally narrower than composition-of-matter patents and may be avoidable through alternative excipients, processing conditions, or packaging.

What patent litigation and settlements affect Aldactazide?

No major contemporary litigation or settlement should be presumed to control a new Aldactazide generic without a current docket review. For this product, litigation risk is most likely to arise from a later-listed formulation or process patent rather than from the original combination.

A settlement could affect launch timing if a listed patent remained enforceable. The relevant diligence would include FDA patent listings, ANDA litigation under the Hatch-Waxman Act, district-court complaints, claim-construction rulings, consent judgments, and settlement terms. A historical absence of visible litigation does not substitute for a current case search.

What is the revenue exposure and market opportunity?

Aldactazide is unlikely to represent a large branded revenue opportunity in the United States. The market is mature, genericized, and exposed to substitution by separate-component therapy. Revenue potential is more credible in targeted channels:

• Institutional and long-term-care supply
• Regional generic portfolios
• Private-label pharmacy products
• Markets with limited fixed-dose combination competition
• Contract manufacturing
• Export markets where the combination remains routinely prescribed

The best business case is a low-cost, reliable product with multiple strengths, efficient packaging, and a controlled excipient bill of materials. A high-cost novel delivery system would have difficulty recovering development expense unless it solves a defined problem such as swallowing, stability, adherence, or supply continuity.

Key Takeaways

• Aldactazide combines spironolactone and hydrochlorothiazide in fixed-ratio immediate-release tablets.
• Its original exclusivity is expired, and current market barriers are more likely to be regulatory, manufacturing, and commercial than patent-based.
• The central formulation risks are spironolactone dissolution, hydrochlorothiazide content uniformity, segregation, lubrication, and moisture control.
• Conventional lactose/starch/povidone systems offer the lowest-cost generic path.
• Lactose-free, film-coated, smaller, and unit-dose products provide modest differentiation.
• A current Orange Book and patent-family review is required before relying on any specific patent count, listing, or Paragraph IV strategy.
• The strongest commercial model is a cost-efficient generic or contract-supply product, not a premium reformulation.

FAQs

Is Aldactazide still commercially available?

Availability varies by country, manufacturer, strength, and distribution channel. Generic spironolactone/hydrochlorothiazide products may be available even where the branded Aldactazide product is discontinued or difficult to source.

Can spironolactone and hydrochlorothiazide be substituted for Aldactazide?

Separate tablets can provide the same active ingredients, but substitution requires matching the prescribed doses and accounting for the fixed ratio in the combination product. Pharmacists and prescribers must follow applicable substitution rules.

Does Aldactazide require a novel excipient for generic approval?

No. A generic developer can generally use established pharmaceutical excipients, provided the formulation meets applicable quality, labeling, stability, and bioequivalence requirements.

Which excipient is most important for Aldactazide dissolution?

Magnesium stearate level and lubrication time can materially affect wetting and dissolution. Binder selection, disintegrant placement, active particle size, and granule structure are also important.

Is an Aldactazide formulation patent likely to block generic entry?

A broad blocking patent is unlikely for the original mature combination. A later formulation or process patent could create a narrower issue, but its scope, validity, expiration, and listing status must be assessed separately.

References

1. U.S. Food and Drug Administration. (2018). Aldactazide (spironolactone and hydrochlorothiazide) tablets: Prescribing information.
2. U.S. Food and Drug Administration. (n.d.-a). Approved drug products with therapeutic equivalence evaluations.
3. U.S. Food and Drug Administration. (n.d.-b). Drugs@FDA: FDA-approved drugs database.
4. U.S. Food and Drug Administration. (n.d.-c). ANDA submissions: Content and format.
5. International Council for Harmonisation. (2003). Q1A(R2): Stability testing of new drug substances and products.