List of Excipients in Branded Drug AZITHROMYCIN MONOHYDRATE

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Generic Drugs Containing AZITHROMYCIN MONOHYDRATE

Company	Ingredient	NDC	Excipient
Major Pharmaceuticals	azithromycin monohydrate	0904-6708	ANHYDROUS DIBASIC CALCIUM PHOSPHATE
Major Pharmaceuticals	azithromycin monohydrate	0904-6708	CROSCARMELLOSE SODIUM
Major Pharmaceuticals	azithromycin monohydrate	0904-6708	D&C RED NO. 30
Major Pharmaceuticals	azithromycin monohydrate	0904-6708	HYPROMELLOSE 2910
Major Pharmaceuticals	azithromycin monohydrate	0904-6708	LACTOSE MONOHYDRATE

What are the Most Frequently-Used Excipients in AZITHROMYCIN MONOHYDRATE?

# Of NDCs	Excipient
9	ANHYDROUS DIBASIC CALCIUM PHOSPHATE
19	CALCIUM PHOSPHATE, DIBASIC, ANHYDROUS
2	CELLULOSE, MICROCRYSTALLINE
2	CITRIC ACID MONOHYDRATE
29	CROSCARMELLOSE SODIUM

Last updated: September 27, 2026

ecutive summary: Azithromycin monohydrate offers commercial value primarily as a differentiated API solid form and as a platform for immediate-release oral products, pediatric suspensions, dispersible tablets, and combination products. The core opportunity is not originator-style patent exclusivity. Azithromycin is a mature, genericized small molecule with extensive regulatory precedent. Value depends on API quality, hydrate control, taste masking, powder-for-reconstitution stability, supply reliability, and access to regulated markets.

Azithromycin Monohydrate Excipient Strategy and Commercial Opportunities

What is azithromycin monohydrate and how does it compare with azithromycin dihydrate?

Azithromycin monohydrate is a crystalline hydrate of azithromycin, a 15-membered azalide macrolide antibiotic. The marketed reference product, Zithromax, and many generic products have historically used azithromycin dihydrate or azithromycin-based material described by the applicable pharmacopoeia and regulatory filing. A monohydrate product therefore requires clear control of solid form, water content, polymorphism, particle size, and conversion during processing and storage.

Attribute	Azithromycin monohydrate	Azithromycin dihydrate
Product role	API solid form or formulation-specific material	Common reference and generic API form
Primary commercial advantage	Potential control of water activity, density, flow, and stability	Extensive market and regulatory precedent
Main technical risk	Hydrate conversion and form reproducibility	Moisture uptake and batch-to-batch water variation
Regulatory requirement	Solid-form characterization and equivalence evidence	Established precedent, subject to supplier and product controls
Best commercial use	Differentiated generic, pediatric product, formulation platform	Conventional tablets, capsules, suspensions, and bulk generic supply

The commercial case for monohydrate depends on whether the form provides measurable advantages in dissolution, manufacturability, chemical stability, powder flow, taste masking, or storage. A hydrate designation alone is unlikely to support meaningful premium pricing.

What solid-state controls are required?

A commercial monohydrate API program should establish:

• Water content by Karl Fischer titration.
• XRPD pattern and crystallinity.
• Thermal behavior by DSC and thermogravimetric analysis.
• Particle-size distribution and morphology.
• Bulk and tapped density.
• Residual solvents.
• Related substances and degradation products.
• Hygroscopicity under controlled relative humidity.
• Conversion risk to anhydrous or higher-hydrate forms.
• Dissolution behavior after storage and formulation.

The critical control is not only the initial hydrate state. It is the form delivered in the finished dosage form after wet granulation, aqueous coating, suspension manufacture, drying, packaging, and distribution.

What excipients are suitable for azithromycin monohydrate tablets and capsules?

Immediate-release tablets and capsules are the largest formulation opportunity. The excipient system should support rapid dissolution while limiting moisture exposure and avoiding chemical degradation.

Tablet excipient strategy

A conventional direct-compression or dry-granulation system may include:

Function	Candidate excipients	Commercial rationale
Diluent	Microcrystalline cellulose, anhydrous lactose, dibasic calcium phosphate	Supports tablet weight, compression, and flow
Disintegrant	Crospovidone, croscarmellose sodium, sodium starch glycolate	Promotes rapid tablet breakup
Binder	Povidone, copovidone, low-substituted hydroxypropyl cellulose	Improves mechanical strength
Glidant	Colloidal silicon dioxide	Improves flow and die filling
Lubricant	Magnesium stearate, sodium stearyl fumarate	Controls ejection and sticking
Film coating	Hypromellose, polyvinyl alcohol, polyethylene glycol, titanium dioxide or permitted colorants	Improves handling, identification, and taste masking

Direct compression is attractive when the API has acceptable flow and compressibility. Dry granulation can improve content uniformity and handling without exposing the API to water. Aqueous wet granulation carries greater risk because hydrate conversion and local pH changes can affect the API.

Anhydrous lactose should be assessed separately from monohydrate lactose. Lactose hydrate can alter water activity and may affect the solid-state balance of the API. Compatibility studies should include accelerated humidity and temperature conditions rather than relying only on short-term binary mixtures.

Capsule formulation

Hard gelatin or hypromellose capsules can reduce formulation complexity. A typical fill may use microcrystalline cellulose, crospovidone, colloidal silicon dioxide, and a low-level lubricant. Capsule products are commercially useful where a low-cost manufacturing process is more important than tablet branding or pediatric flexibility.

Capsules also create a route for multiparticulate products. Coated pellets or mini-tablets can improve dose flexibility and taste masking, but they add manufacturing cost and may create new dissolution and coating-process risks.

What excipients are suitable for azithromycin oral suspension?

Pediatric powder-for-reconstitution is one of the strongest formulation opportunities because azithromycin has a pronounced bitter taste and pediatric dosing is weight-based.

A commercial suspension typically requires:

• Suspending agents such as xanthan gum, sodium carboxymethylcellulose, hypromellose, or microcrystalline cellulose-carboxymethylcellulose combinations.
• Wetting agents such as polysorbate 80 where justified by compatibility and safety.
• Sweeteners such as sucrose, sucralose, saccharin sodium, or equivalent market-appropriate systems.
• Flavors, often fruit-based.
• Buffers or pH adjusters.
• Preservatives where required by the multidose container and in-use stability data.
• Antifoaming or processing aids when needed.
• Bulking agents to maintain powder volume and dose uniformity.

The formulation must preserve uniformity after reconstitution, limit sedimentation and caking, remain pourable, and maintain potency through the labeled in-use period. The powder should be engineered for rapid wetting and low dust generation.

Taste masking is a significant differentiator. Options include polymer coating, lipid-based barriers, ion-exchange resins, complexation, and optimized sweetener-flavor systems. Excessive coating can delay dissolution, while high levels of sweetener can increase viscosity and packaging volume.

A dry powder for reconstitution can provide stronger commercial differentiation than another conventional tablet, particularly in markets with high pediatric antibiotic demand and limited refrigeration infrastructure.

What formulation patents can protect azithromycin products?

The basic azithromycin compound is no longer the primary exclusivity asset. Commercial protection may instead focus on:

• Specific monohydrate or polymorphic forms.
• Particle-size distributions.
• Stabilized suspensions.
• Taste-masked particles.
• Controlled-release or modified-release systems.
• Dispersible or orally disintegrating tablets.
• Fixed-dose combinations.
• Manufacturing processes that produce a reproducible hydrate.
• Packaging systems that control moisture ingress.
• Specific excipient ratios linked to dissolution or stability.
• New therapeutic uses, where legally and medically supportable.

A patent directed only to a conventional tablet containing azithromycin and standard excipients is vulnerable to novelty and obviousness challenges. Stronger claims usually require a defined solid form, measurable physical property, process limitation, or clinically relevant performance result.

What is the FDA regulatory status of azithromycin?

Azithromycin is an FDA-approved small-molecule antibacterial. FDA-approved dosage forms include tablets, capsules, oral suspension, and intravenous products. The reference product Zithromax was approved under the new drug application pathway, while later products have entered primarily through abbreviated new drug applications.

The principal regulatory routes are:

Product	Likely FDA pathway
Conventional immediate-release tablet or capsule	ANDA, subject to reference-product requirements
Powder for oral suspension	ANDA or, in some cases, a separate NDA strategy
New solid form with bioequivalence	ANDA if the product meets statutory requirements
New indication or clinically differentiated delivery system	NDA or supplemental NDA strategy
Combination product	ANDA, NDA, or combination-specific route depending on the reference product

The sponsor must demonstrate pharmaceutical equivalence and bioequivalence where an ANDA is used. For suspension products, comparative performance can include potency, particle size, rheology, reconstitution, microbial quality, and dissolution.

FDA labeling for azithromycin products includes boxed-warning and safety information concerning hepatotoxicity, QT prolongation, hypersensitivity, and other risks. A new excipient system does not remove the need to address the reference product’s established safety profile. FDA labeling and Orange Book records remain the controlling sources for product-specific regulatory status.[1][2]

What is the Orange Book status of azithromycin products?

The Orange Book identifies approved drug products, therapeutic-equivalence evaluations, patent information submitted by NDA holders, and exclusivity data. Azithromycin generic products are generally associated with abbreviated approval pathways and therapeutic-equivalence listings where applicable.

The commercial significance is straightforward:

1. Conventional azithromycin products face established generic competition.
2. Orange Book-listed patents, if any remain relevant to a particular reference product or presentation, must be reviewed product by product.
3. A new formulation may have a separate patent position even where the active ingredient is generic.
4. Patent listing does not guarantee enforceability or prevent an ANDA launch.

A sponsor should review current Orange Book entries, discontinued-product records, reference-listed drugs, and any listed patents before finalizing a product strategy. The relevant analysis must distinguish the active ingredient from formulation-specific and method-of-use claims.

When did azithromycin lose core exclusivity?

Azithromycin’s original compound and core commercial exclusivity expired years ago. The product is now a mature generic market. Originator rights originated with Pliva, with Pfizer commercializing Zithromax in major markets under licensing and commercial arrangements. Pfizer launched Zithromax in the early 1990s, and generic competition subsequently expanded across tablets, capsules, suspension, and injectable presentations.[3]

The current opportunity is therefore based on product differentiation rather than restoration of compound-level exclusivity.

Which companies are challenging azithromycin patents?

Azithromycin has been subject to extensive generic competition from major and regional manufacturers, including companies that commercialize oral solid doses, oral suspensions, and injectable products. The relevant competitive set varies by jurisdiction and product presentation.

Because the core product is genericized, the more important competitive question is whether a new monohydrate product has claims that can withstand:

• Paragraph IV invalidity challenges.
• Non-infringement positions based on a different hydrate or process.
• Bioequivalence-based ANDA substitution.
• Freedom-to-operate review of formulation and manufacturing patents.
• Regulatory challenges to therapeutic equivalence or labeling carve-outs.

A Paragraph IV filing is commercially material only when a listed patent remains enforceable and relevant to the proposed product. For an ordinary azithromycin monohydrate tablet, the primary risk is usually competitive launch from an alternative API form or conventional generic, rather than an originator patent injunction.

What generic entry risks exist for azithromycin monohydrate?

The generic entry risk is high for standard immediate-release products. A monohydrate formulation can face competition from:

• Azithromycin dihydrate tablets.
• Alternative hydrate or anhydrous API products.
• Licensed contract-manufacturing products.
• Regional branded generics.
• Low-cost suspension suppliers.
• Government and hospital tenders.
• Private-label products using the same API source.

A differentiated monohydrate product may still be vulnerable if the finished product shows comparable dissolution and bioequivalence without infringing a valid formulation claim. The strongest defensive position usually combines a reliable supply chain, a difficult-to-copy manufacturing process, a stable and palatable suspension, and regulatory approvals in multiple markets.

How strong is the patent estate for azithromycin monohydrate?

The patent estate is likely weak for the basic active ingredient and stronger only where the product uses a genuinely differentiated form or delivery system.

Asset	Expected protection strength
Azithromycin molecule	Low; mature generic compound
Conventional tablet	Low unless tied to a novel process or performance result
Monohydrate solid form	Moderate if reproducible, novel, and technically superior
Taste-masked pediatric suspension	Moderate to strong if claims cover composition and performance
Controlled-release product	Moderate, with substantial development and clinical risk
Manufacturing process	Moderate if difficult to design around
Packaging and moisture-control system	Low to moderate, usually supplemental protection
New indication	Variable and dependent on claim scope and clinical evidence

A form patent should include analytical definitions, not only a chemical name. Claims may need to specify XRPD peaks, water content, thermal behavior, particle-size limits, or process conditions. The sponsor should also assess whether the monohydrate converts during compression, coating, suspension manufacture, or storage. A patent that protects an unstable form has limited commercial value.

What manufacturing and IP barriers matter most?

The main manufacturing barriers are:

• Consistent hydrate formation.
• Control of residual solvents and water.
• Prevention of agglomeration.
• Reproducible particle size.
• Content uniformity at low dose.
• Taste-masking without dissolution failure.
• Suspension redispersibility.
• Packaging protection from humidity.
• Reliable global API supply.

The most valuable know-how may remain outside the patent system. Crystallization seeding, drying endpoint, milling conditions, granulation moisture, coating parameters, and container-closure selection can create practical barriers even when competitors can legally design around patent claims.

What commercial opportunities exist for azithromycin monohydrate?

The strongest opportunities are in regulated generic markets and differentiated pediatric products.

Pediatric oral suspension

A stable, palatable, low-viscosity suspension with a long in-use period can compete on pharmacy convenience and adherence. This segment supports brand differentiation more effectively than an ordinary tablet.

Dispersible and orally disintegrating tablets

These products can target patients with swallowing difficulty and markets with limited access to water. The formulation must maintain rapid dispersion, acceptable taste, and dose uniformity.

Hospital and institutional supply

Hospitals may value ready-to-use presentations, reduced preparation steps, robust room-temperature stability, and dependable tender supply. Injectable azithromycin requires a separate sterile manufacturing strategy and should not be treated as a direct extension of an oral monohydrate program.

Emerging-market branded generics

Azithromycin remains commercially relevant in markets where respiratory and sexually transmitted infections generate antibiotic demand. Registration, pharmacovigilance, antimicrobial-stewardship requirements, and tender pricing will influence margins more than compound patent status.

Contract development and manufacturing

A validated monohydrate platform can support licensing or contract-manufacturing deals covering API supply, pediatric suspension technology, taste masking, or region-specific registrations. The asset is more attractive when it includes regulatory dossiers, stability data, and reproducible manufacturing controls.

Is there biosimilar risk for azithromycin?

No. Azithromycin is a small-molecule drug, not a biologic. The relevant competitive risk is generic substitution, not biosimilar interchangeability. Regulatory and commercial analysis should focus on ANDA approvals, therapeutic equivalence, formulation patents, API suppliers, and local generic-registration pathways.

How does azithromycin compare with competing antibiotics?

Azithromycin competes with amoxicillin, amoxicillin-clavulanate, doxycycline, clarithromycin, and other agents depending on indication and local treatment guidelines.

Product	Formulation opportunity	Commercial constraint
Azithromycin	Pediatric suspension, tablets, capsules, dispersible forms	Antibiotic stewardship and resistance concerns
Amoxicillin	High-volume suspension and chewables	Heavy generic competition
Doxycycline	Tablets and capsules	Pediatric and tolerability limitations in some uses
Clarithromycin	Tablets and suspension	Drug interactions and dosing burden
Amoxicillin-clavulanate	Suspension and tablets	Stability, taste, and dosing complexity

Azithromycin’s long tissue persistence and short-course dosing can support demand, but regulatory agencies and clinical guidelines increasingly emphasize appropriate antibiotic use. A commercial strategy should target approved indications and product usability rather than broad empiric positioning.

What are the key launch scenarios?

Scenario	Product	Commercial outlook
Low-risk generic	Conventional tablet or capsule	Fastest route, lowest differentiation
Moderate differentiation	Monohydrate tablet with improved stability or flow	Potential manufacturing and supply advantage
High-value pediatric	Taste-masked powder for suspension	Strongest formulation differentiation
Specialty delivery	Dispersible or orally disintegrating tablet	Higher development and patent potential
Regional licensing	Dossier plus API and finished-product supply	Attractive where registration capability is limited
Premium branded generic	Pediatric or adherence-focused product	Depends on evidence, branding, and distribution

Key Takeaways

• Azithromycin monohydrate is a formulation and API differentiation opportunity, not a compound-exclusivity opportunity.
• Standard tablets and capsules face high generic-entry risk.
• Pediatric powder-for-reconstitution offers the clearest commercial differentiation.
• Hydrate conversion, moisture control, taste masking, and dissolution are the central technical issues.
• Formulation patents should include measurable solid-state or performance limitations.
• Azithromycin is subject to generic competition, not biosimilar competition.
• Orange Book, FDA labeling, and current ANDA records must be reviewed for each targeted presentation.
• The strongest commercial package combines a validated monohydrate process, regulatory-ready stability data, pediatric usability, and dependable supply.

FAQs

Can azithromycin monohydrate be used in a generic tablet?

Yes, if the API and finished product meet applicable quality, pharmaceutical-equivalence, bioequivalence, and regulatory requirements. The sponsor must control hydrate state throughout manufacturing and storage.

Is azithromycin monohydrate more stable than azithromycin dihydrate?

Not categorically. Relative stability depends on humidity, temperature, excipients, particle size, packaging, and processing conditions. The advantage must be demonstrated through comparative solid-state and stability studies.

What is the best excipient for masking azithromycin taste?

No single excipient is universally optimal. Polymer coating, ion-exchange systems, lipid barriers, and sweetener-flavor combinations should be screened against dissolution, stability, viscosity, and pediatric acceptability.

Can a monohydrate form support a new patent?

Potentially. Patentability depends on novelty, non-obviousness, enablement, claim scope, and evidence of a technical advantage. A hydrate name alone is unlikely to provide strong protection.

Is a pediatric azithromycin suspension commercially attractive?

Yes, particularly where the product improves taste, reconstitution, redispersibility, storage stability, or dosing convenience. Commercial success remains dependent on antibiotic stewardship, tender pricing, local registration, and supply reliability.

References

1. U.S. Food and Drug Administration. (n.d.). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/
2. U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/
3. Pfizer Inc. (n.d.). Zithromax product information and company history. https://www.pfizer.com/
4. U.S. Pharmacopeia. (2024). United States Pharmacopeia and National Formulary. United States Pharmacopeial Convention.
5. International Council for Harmonisation. (2003). Q1A(R2): Stability testing of new drug substances and products. https://www.ich.org/
6. World Health Organization. (2023). WHO AWaRe antibiotic book. World Health Organization. https://www.who.int/ools/awaRe/aware-antibiotic-book