List of Excipients in Branded Drug REGADENOSON

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Generic Drugs Containing REGADENOSON

Company	Ingredient	NDC	Excipient
GE Healthcare	regadenoson anhydrous	0407-5034	EDETATE DISODIUM
GE Healthcare	regadenoson anhydrous	0407-5034	PROPYLENE GLYCOL
GE Healthcare	regadenoson anhydrous	0407-5034	SODIUM PHOSPHATE, DIBASIC, ANHYDROUS
GE Healthcare	regadenoson anhydrous	0407-5034	SODIUM PHOSPHATE, MONOBASIC
GE Healthcare	regadenoson anhydrous	0407-5034	WATER
Hospira Inc	regadenoson	0409-1401	EDETATE DISODIUM
Hospira Inc	regadenoson	0409-1401	PROPYLENE GLYCOL

What are the Most Frequently-Used Excipients in REGADENOSON?

# Of NDCs	Excipient
16	EDETATE DISODIUM
16	PROPYLENE GLYCOL
1	SODIUM PHOSPHATE
2	SODIUM PHOSPHATE DIBASIC DIHYDRATE
1	SODIUM PHOSPHATE, DIBASIC
4	SODIUM PHOSPHATE, DIBASIC, ANHYDROUS
11	SODIUM PHOSPHATE, DIBASIC, DIHYDRATE

Regadenoson Excipient Strategy and Commercial Opportunities

Last updated: September 5, 2026

Regadenoson is a mature, single-dose injectable diagnostic agent used to induce pharmacologic stress during radionuclide myocardial perfusion imaging. Its commercial value is concentrated in reliable administration, hospital workflow, supply continuity, and compatibility with imaging protocols rather than in new active-ingredient claims. The reference product, Lexiscan, is a ready-to-use 0.4 mg/5 mL intravenous solution containing phosphate buffers, propylene glycol, and water for injection.[1]

The strongest commercial opportunities are differentiated presentations, supply-chain reliability, and hospital-use products that reduce preparation steps. New excipient claims could support a product strategy, but a basic reformulation would face a high burden of clinical bridging, injectables manufacturing validation, and pricing pressure from approved generics.

What is the current regadenoson formulation?

Lexiscan is supplied as a sterile, preservative-free intravenous solution.

Attribute	Reference-product profile
Active ingredient	Regadenoson
Strength	0.4 mg in 5 mL
Concentration	0.08 mg/mL
Route	Intravenous bolus
Dosage form	Sterile aqueous injection
Buffer system	Dibasic sodium phosphate and monobasic sodium phosphate
Cosolvent	Propylene glycol
Vehicle	Water for injection
Target pH	Approximately 6.3 to 7.3
Administration	Rapid IV injection followed by saline flush
Primary use	Pharmacologic stress during radionuclide myocardial perfusion imaging
Reference product	Lexiscan, Astellas Pharma US

The formulation contains 0.084 mg/mL regadenoson, equivalent to 0.42 mg in a 5 mL vial, according to the U.S. prescribing information. The marketed dose is 0.4 mg, or 5 mL, administered as an intravenous bolus.[1]

The formulation is intentionally simple. Regadenoson is a small-molecule injectable with no requirement for a complex delivery system, lipid carrier, depot vehicle, or lyophilized reconstitution step.

Which excipients are used in Lexiscan?

The principal excipients are phosphate salts, propylene glycol, and water for injection.

Phosphate buffer

Dibasic sodium phosphate and monobasic sodium phosphate control pH and help maintain solution stability. The buffer also supports compatibility with a rapid intravenous bolus. Any substitute buffer would need to preserve:

• Regadenoson chemical stability
• Acceptable osmolality
• Injectable pH
• Low particulate formation
• Container compatibility
• Compatibility with the post-dose saline flush
• Tolerability during rapid administration

Potential alternatives include citrate or acetate buffers, but replacing phosphate would require comparative stability, toxicology, extractables, and clinical compatibility data. Phosphate is commercially available, familiar to injectable manufacturers, and unlikely to create a meaningful cost barrier.

Propylene glycol

Propylene glycol functions as a cosolvent and may support solubility and formulation robustness. Its use creates a potential differentiation point because injectable propylene glycol can raise concerns about tolerability, exposure, and use in patients with compromised renal or hepatic function. The total amount in a single Lexiscan dose is limited, but hospitals may still prefer a formulation with a lower cosolvent burden if equivalent stability and solubility can be demonstrated.

A lower-propylene-glycol formulation could support product positioning, but it would not automatically provide a clinical advantage. Regadenoson is administered as a single diagnostic dose, so cumulative solvent exposure is materially lower than with chronic injectable products.

Water for injection

Water for injection is the principal vehicle. The product does not require a complex isotonicity system or antimicrobial preservative. A preservative-free presentation is appropriate because the commercial product is used as a single-dose injectable.

What excipient strategies could create commercial differentiation?

The most credible strategy is to preserve the clinical dose and simplify hospital handling.

Strategy	Commercial value	Development burden	Patent potential
Lower-cosolvent formulation	Moderate	Moderate to high	Moderate
Phosphate-free formulation	Low to moderate	Moderate	Low to moderate
Prefilled syringe	High workflow value	Moderate	Moderate
Ready-to-administer 5 mL device	High	Moderate to high	Moderate
Extended in-use stability	Moderate	Moderate	Moderate
Improved low-temperature stability	Moderate	Moderate	Moderate
Multi-dose vial	Low	High due to preservative and sterility issues	Low
Lyophilized product	Low	High	Low
Alternative concentration	Moderate	High clinical and labeling burden	Moderate
Co-packaged saline flush	Moderate	Moderate	Moderate
Imaging-center bulk presentation	Moderate	Moderate	Low to moderate

Prefilled syringe

A prefilled syringe is the clearest product opportunity. Lexiscan is already a low-volume, fixed-dose product, making it suitable for a ready-to-use device. A prefilled presentation could reduce vial handling, syringe preparation, dose measurement, and medication errors.

Commercial advantages could include:

• Faster nuclear medicine workflow
• Lower preparation labor
• Reduced vial and syringe manipulation
• Improved dose standardization
• Lower risk of wrong-volume administration
• Better use in high-throughput imaging centers

The principal barriers are device compatibility, extractables and leachables, silicone oil, tungsten, stopper interaction, plunger force, break-loose force, and long-term stability. Regadenoson exposure to the syringe barrel and closure would need evaluation under ICH stability conditions.

A prefilled syringe could support a 505(b)(2) strategy if the product contains a meaningful formulation or device difference from the reference product. An ANDA strategy may be possible where the presentation and inactive ingredients remain within the permitted generic framework.

Lower-solvent formulation

Reducing or eliminating propylene glycol could produce a cleaner excipient profile. The opportunity depends on whether regadenoson remains soluble and chemically stable at the target concentration without the current cosolvent level.

A development program would likely evaluate:

• Solubility across pH ranges
• Chemical degradation products
• Adsorption to container surfaces
• Freeze-thaw stability
• Agitation and transport stress
• Particulate formation
• Compatibility with polypropylene and cyclic olefin polymer syringes
• Short-term stability after puncture or device activation

The commercial case is stronger if the reformulation can also improve container compatibility or enable a prefilled syringe.

Extended stability

A product with improved stability under temperature excursions could reduce wastage at imaging centers and simplify distribution. This is more valuable for a product that moves through decentralized hospitals, outpatient imaging networks, and international markets with variable cold-chain control.

The commercial claim should focus on validated storage performance, such as improved stability at controlled room temperature, rather than a broad claim of "better stability." Stability must cover potency, impurities, pH, appearance, osmolality, sterility, endotoxin, and visible and subvisible particles.

Co-packaged flush

Regadenoson is followed by a saline flush in clinical practice. A product containing a matched saline flush could reduce preparation time. The commercial and regulatory value would depend on whether the flush is packaged as a convenience component or supplied as an integrated delivery system.

A co-pack could be attractive for nuclear cardiology departments, but it would increase packaging, labeling, reimbursement, and inventory complexity. It also may compete with inexpensive hospital saline supplies.

What patents protect regadenoson and its formulations?

The original regadenoson composition and use patents have largely lost commercial exclusivity in the United States. Lexiscan received FDA approval in 2008, and the active-ingredient exclusivity period expired years before the current generic market.[1,2]

The relevant intellectual-property categories are:

1. Regadenoson chemical composition patents.
2. A2A adenosine receptor agonist patents.
3. Use patents covering pharmacologic stress imaging.
4. Injectable formulation patents.
5. Device and prefilled-syringe patents.
6. Manufacturing and purification patents.
7. Combination or co-packaging patents.

Core composition and method-of-use rights are less likely to block entry than device, formulation, or manufacturing claims. A new formulation could create a narrower secondary patent estate, but its enforceability would depend on unexpected stability, reduced impurity formation, improved tolerability, or a specific device interaction.

How strong is the formulation patent estate?

The formulation patent opportunity is moderate but narrow.

A credible patent claim could cover:

• A defined regadenoson concentration range
• A specific phosphate-to-regadenoson ratio
• Reduced propylene glycol content
• A defined pH and osmolality window
• A prefilled syringe using a specified polymer
• Improved stability under defined storage conditions
• Reduced particulate formation
• A container-closure system that limits adsorption or leachables

A patent claiming only "regadenoson in water with a pharmaceutically acceptable excipient" would face substantial obviousness and written-description risks. The strongest applications would connect the excipient selection to measured technical performance.

When did regadenoson lose exclusivity?

Regadenoson’s new chemical entity exclusivity followed its 2008 approval and did not provide current market protection. Generic regadenoson injection products are now available in the United States, confirming that the reference product no longer has effective exclusivity over the basic injectable presentation.[1,3]

Milestone	Date or status
Lexiscan FDA approval	2008
U.S. NCE exclusivity	Expired
Core composition exclusivity	Expired or no longer commercially blocking
Generic regadenoson availability	Established
Current market structure	Brand plus approved generic injections
Main remaining differentiation	Device, workflow, supply, formulation, and service

What is the Orange Book status of regadenoson?

The Orange Book remains the primary source for current listed patents, exclusivity, and reference-listed-drug information. The relevant reference product is Lexiscan injection, NDA 021244.[2]

For a new entrant, the practical Orange Book analysis should distinguish between:

• Active listed patents
• Expired patents
• Delisted patents
• Product-specific patents
• Method-of-use claims
• Device or formulation claims
• Patent certifications required for an ANDA

Because generic regadenoson products are already marketed, the active-ingredient barrier has been overcome. A later entrant should expect the central regulatory question to be whether its formulation qualifies for an ANDA or requires a 505(b)(2) application.

Are there Paragraph IV challenges involving regadenoson?

Paragraph IV challenges were relevant to the historical generic-entry process for Lexiscan. The current commercial environment is different because multiple generic products have entered the market and the principal Lexiscan exclusivity periods have expired.

For a new formulation, Paragraph IV exposure depends on whether the applicant seeks approval as an ANDA and whether any unexpired patents are listed against the reference product. A 505(b)(2) applicant may face patent certifications or litigation based on listed patents, depending on the proposed labeling and reliance on the reference product.

A formulation developer should expect litigation risk to concentrate on:

• A listed formulation patent
• A listed method-of-use patent
• A device patent tied to a prefilled syringe
• Labeling differences that create induced-infringement arguments
• Manufacturing claims that are difficult to design around

What regulatory pathway is best for a new regadenoson formulation?

ANDA pathway

An ANDA is the lowest-cost route for a conventional generic injection that matches the reference product in active ingredient, strength, dosage form, route, and key performance attributes. The applicant would typically need to demonstrate pharmaceutical equivalence and bioequivalence or rely on the injectable-product framework applicable to the product.

An ANDA is commercially attractive where the objective is low-cost volume and hospital formulary access. It is less attractive for a differentiated prefilled device or a clinically meaningful excipient change that does not fit the generic equivalence framework.

505(b)(2) pathway

A 505(b)(2) application is more suitable for:

• A new delivery device
• A materially different formulation
• A new concentration
• A new container-closure system
• A co-packaged product
• A product with a labeling change supported by additional data

The pathway can support three commercial advantages: differentiated pricing, patentable product attributes, and reduced dependence on direct price competition. The development program would still require robust quality, stability, device, and clinical-bridging data.

FDA regulatory status

Regadenoson is FDA-approved for use as a pharmacologic stress agent in myocardial perfusion imaging. It is not a biologic, so biosimilar regulation does not apply. Competitive products are regulated as small-molecule injectable drugs through NDA and ANDA pathways.[1,3]

What manufacturing and IP barriers affect regadenoson?

The active ingredient is not the principal barrier. The main technical barriers are sterile manufacturing and injectable quality control.

Key manufacturing requirements include:

• Sterile compounding and aseptic filling
• Low particulate control
• Endotoxin control
• Container-closure integrity
• Accurate low-dose assay
• Control of degradation products
• Propylene glycol and phosphate raw-material quality
• Device assembly, where applicable
• Stability in the final container

A 0.4 mg dose creates an analytical challenge because the drug load is small relative to the fill volume. Assay precision, content uniformity, and adsorption studies become important, particularly in prefilled syringes and low-binding containers.

Manufacturing access may provide a stronger commercial advantage than a conventional excipient patent. Hospitals and distributors value dependable supply because imaging schedules are difficult to reschedule and diagnostic delays can create operational costs.

Which companies are competing in regadenoson?

The market includes Astellas as the Lexiscan reference-product supplier and generic manufacturers with approved regadenoson injection products. Generic competition is primarily price-driven, with differentiation based on supply reliability, distributor relationships, packaging, and contracting.

The main competitive alternatives are:

Competitive category	Product or approach	Commercial effect
Reference brand	Lexiscan	Brand recognition and established clinical use
Generic injection	Regadenoson injection	Lower acquisition cost
Alternative stress agent	Adenosine injection	Established but less convenient infusion profile
Alternative stress agent	Dipyridamole	Different pharmacologic and workflow profile
Device-enhanced product	Prefilled syringe	Potential labor and safety savings
Service-based supplier	Contracted hospital supply	Inventory and continuity advantage

Regadenoson competes clinically with adenosine and dipyridamole. Its single-bolus administration is a significant workflow advantage, while its unit price remains exposed to generic competition.

What revenue exposure and commercial opportunities exist?

Regadenoson revenue is linked to the volume of myocardial perfusion imaging, the share of pharmacologic stress studies, and the proportion of studies using regadenoson rather than adenosine or dipyridamole.

The most attractive commercial segments are:

1. High-volume outpatient imaging centers.
2. Hospital nuclear cardiology departments.
3. Integrated delivery networks seeking standardization.
4. International markets with limited generic supply.
5. Contract manufacturing and private-label supply.
6. Prefilled or ready-to-administer presentations.
7. Hospital tenders where supply continuity carries weight.

A generic vial strategy is likely to produce low margins unless supported by manufacturing scale. A differentiated device or formulation can command a higher price, but the premium must be justified through workflow savings, lower wastage, or improved supply performance.

How does regadenoson compare with adenosine?

Factor	Regadenoson	Adenosine
Administration	Single rapid IV bolus	Continuous infusion
Preparation	Low	Higher
Dosing	Fixed dose	Weight-based or protocol-dependent
Workflow	Simple	More equipment and monitoring steps
Formulation opportunity	Prefilled syringe and stability	Infusion bags, premixed products, line compatibility
Generic pressure	High	High
Clinical differentiation	A2A-selective pharmacologic stress agent	Nonselective adenosine activity

Regadenoson’s commercial advantage is operational simplicity. An excipient or device strategy should preserve that advantage rather than introduce reconstitution, infusion, or additional handling.

Key Takeaways

• Lexiscan is a preservative-free, ready-to-use regadenoson injection containing phosphate buffers, propylene glycol, and water for injection.
• Core regadenoson exclusivity has expired, and generic competition is established.
• The strongest product opportunity is a prefilled syringe or ready-to-administer device.
• Lower propylene glycol and improved container compatibility could support a differentiated formulation.
• A basic excipient substitution is unlikely to justify a durable premium without measurable technical or clinical benefits.
• A conventional generic is suited to an ANDA strategy; a differentiated device or formulation may require a 505(b)(2) application.
• Biosimilar risk does not apply because regadenoson is a small-molecule drug.
• Manufacturing reliability, sterile capacity, and hospital contracting may provide greater commercial value than broad formulation patents.
• The relevant competitive alternatives are Lexiscan, generic regadenoson, adenosine, and dipyridamole.
• The commercial market is mature, so returns depend on cost control, supply continuity, and workflow differentiation.

FAQs

Can propylene glycol be removed from regadenoson injection?

Possibly, but removal would require proof that regadenoson remains soluble, stable, compatible with the container, and suitable for intravenous administration at the marketed concentration.

Is a prefilled regadenoson syringe patentable?

Yes, if the application claims a specific device, container material, formulation, stability profile, or technical interaction that is novel and non-obvious. A generic claim to a syringe containing regadenoson would be vulnerable to prior-art challenges.

Does regadenoson require a biosimilar development program?

No. Regadenoson is a small-molecule drug and is regulated through generic-drug or 505(b)(2) pathways rather than the biosimilar pathway.

Would a regadenoson multi-dose vial be commercially attractive?

Usually not. A multi-dose vial would introduce preservative, sterility, in-use stability, labeling, and contamination-control requirements that conflict with the product’s single-dose workflow.

What is the best international opportunity for regadenoson formulation technology?

The strongest opportunities are markets with limited generic supply, high nuclear imaging volumes, and hospital demand for ready-to-use injectable products. A stable prefilled presentation may have more value internationally than a minor excipient change.

References

1. U.S. Food and Drug Administration. (2021). Lexiscan (regadenoson) injection prescribing information. Astellas Pharma US, Inc.

2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

3. U.S. Food and Drug Administration. (2024). Drugs@FDA: Regadenoson injection and Lexiscan NDA 021244. FDA.