List of Excipients in Branded Drug NEOSTIGMINE METHYLSULFATE

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Fresenius Kabi USA LLC	NEOSTIGMINE METHYLSULFATE	neostigmine methylsulfate	63323-413	ACETIC ACID
Fresenius Kabi USA LLC	NEOSTIGMINE METHYLSULFATE	neostigmine methylsulfate	63323-413	PHENOL
Fresenius Kabi USA LLC	NEOSTIGMINE METHYLSULFATE	neostigmine methylsulfate	63323-413	SODIUM ACETATE
Fresenius Kabi USA LLC	NEOSTIGMINE METHYLSULFATE	neostigmine methylsulfate	63323-413	SODIUM HYDROXIDE

Generic Drugs Containing NEOSTIGMINE METHYLSULFATE

Company	Ingredient	NDC	Excipient
Henry Schein Inc	neostigmine methylsulfate	0404-9925	ACETIC ACID
Henry Schein Inc	neostigmine methylsulfate	0404-9925	PHENOL
Henry Schein Inc	neostigmine methylsulfate	0404-9925	SODIUM ACETATE
Henry Schein Inc	neostigmine methylsulfate	0404-9925	SODIUM HYDROXIDE

What are the Most Frequently-Used Excipients in NEOSTIGMINE METHYLSULFATE?

# Of NDCs	Excipient
35	ACETIC ACID
34	PHENOL
35	SODIUM ACETATE
35	SODIUM HYDROXIDE

Neostigmine Methylsulfate Excipient Strategy and Commercial Opportunities

Last updated: August 26, 2026

Neostigmine methylsulfate is an established injectable acetylcholinesterase inhibitor used to reverse nondepolarizing neuromuscular blockade after surgery and to treat selected gastrointestinal and urinary conditions. Its active-ingredient and basic injectable formulation patents are long expired. Commercial opportunity now depends on sterile manufacturing, supply reliability, ready-to-use presentation, formulation differentiation, and hospital procurement economics rather than core molecule exclusivity.

The most practical formulation strategy is a low-excipient, preservative-free aqueous injection using water for injection, sodium chloride for tonicity, and controlled pH adjustment. A differentiated product could pursue ready-to-administer syringes, premixed infusion presentations, reduced-waste vial sizes, or a formulation designed to improve storage, handling, and shortage resilience.

What is neostigmine methylsulfate used for?

Neostigmine methylsulfate is a reversible acetylcholinesterase inhibitor. The injectable product is principally used to reverse the effects of nondepolarizing neuromuscular blocking agents after surgery. It is administered with an anticholinergic agent, such as glycopyrrolate or atropine, to reduce muscarinic adverse effects.

Common injectable strengths include:

Presentation	Typical concentration	Primary use
Single-dose vial or ampule	0.5 mg/mL	Neuromuscular blockade reversal
Single-dose vial or ampule	1 mg/mL	Neuromuscular blockade reversal
Diluted hospital preparation	Variable	Institution-specific administration
Ready-to-use syringe	Potentially 0.5 mg/mL or 1 mg/mL	Operating-room and anesthesia workflows

The label-specific dosage, administration route, and concentration vary by product. FDA-approved labeling remains the controlling source for each presentation.[1]

What excipients are used in neostigmine methylsulfate injections?

The commercial formulation generally relies on a small excipient system because neostigmine methylsulfate is highly water soluble and is administered parenterally.

Core excipient strategy

A conventional formulation may contain:

• Water for injection as the vehicle.
• Sodium chloride for isotonicity.
• Hydrochloric acid or sodium hydroxide for pH adjustment.
• In some products, citrate and citric acid as a buffering system.

Product compositions are not uniform across manufacturers. FDA labeling and DailyMed entries should be reviewed product by product before making a regulatory equivalence or freedom-to-operate conclusion.[1,2]

Why a minimal excipient system is commercially attractive

A simple aqueous formulation can reduce:

• Excipient compatibility risks.
• Extractables and leachables burden.
• Analytical method complexity.
• Sterile-filter and filling challenges.
• Labeling and procurement barriers.
• The likelihood of a formulation patent challenge.

The commercial trade-off is that a simple formulation is difficult to distinguish from established generic products. Value must come from presentation, supply reliability, device integration, or a clinically meaningful handling benefit.

Which excipients are technically relevant?

Sodium chloride

Sodium chloride is the most direct isotonicity agent. It is familiar to regulators and hospitals, has a long injectable-use history, and generally creates limited formulation complexity.

A formulation using approximately physiological sodium chloride levels can support a near-isotonic product, but the final osmolality must be measured rather than inferred from nominal concentration. Neostigmine methylsulfate itself contributes materially to osmolality.

Citrate buffer

Citrate can provide pH control and may improve batch-to-batch pH consistency. Its inclusion requires assessment of:

• Buffer capacity.
• Neostigmine stability over the proposed shelf life.
• Compatibility with container closure components.
• Local tolerability and injection-site considerations.
• Interaction with other agents if the product is intended for dilution or co-packaging.

A citrate-buffered product may have a stronger formulation rationale than a sodium-chloride-only product, but it also creates a more complex composition that may affect ANDA sameness and patent strategy.

Hydrochloric acid and sodium hydroxide

These agents are commonly used for pH adjustment and may not be present at a meaningful concentration in the finished product. Their use does not ordinarily create a strong commercial differentiator. The critical variables are final pH, buffer capacity, degradation profile, and container compatibility.

Preservatives

A preservative-free, single-dose presentation is generally the strongest commercial baseline for an operating-room injectable. Preservatives can introduce:

• Toxicity and tolerability concerns.
• Restrictions on intended patient populations.
• Additional extractables and leachables questions.
• More complicated labeling.
• Lower acceptance for products used in acute-care settings.

A multi-dose strategy could use a preservative, but the market case would need to justify the trade-off through lower cost, reduced waste, or a specific institutional use case. A preservative-free multi-dose product would require a robust multidose contamination-control strategy and would face a higher technical burden.

What formulation patents protect neostigmine methylsulfate?

The active ingredient is old, and basic aqueous injectable formulations are unlikely to support meaningful composition-of-matter exclusivity. The principal protection opportunities would involve:

• A specific concentration and buffer system.
• A defined stability profile.
• A ready-to-use syringe or cartridge.
• A dual-drug presentation with glycopyrrolate or atropine.
• A controlled administration device.
• A novel lyophilized or concentrated presentation.
• A manufacturing process that produces a defined impurity profile.

Patent value would depend on whether the claims capture a real technical advantage. Broad claims covering neostigmine methylsulfate in water, saline, or a conventional pH-adjusted injection would face substantial validity and prior-art risk.

Orange Book status

Bloxiverz, an injectable neostigmine methylsulfate product, was approved by FDA in 2013 under NDA 204078.[3] Its regulatory exclusivity was more important than patent exclusivity. The product received three-year exclusivity associated with approval of a new drug application under the 505(b)(2) framework. That exclusivity period has expired.

Public FDA Orange Book records should be checked for the current patent listing status of each NDA. For an old injectable active ingredient, the principal practical conclusion is that generic entry is not generally blocked by a live molecule patent. Any relevant barriers are more likely to arise from facility readiness, drug-shortage dynamics, procurement contracts, or product-specific formulation and device claims than from an active Orange Book patent estate.[4]

When did neostigmine methylsulfate lose exclusivity?

Neostigmine methylsulfate lost effective molecule-level exclusivity decades ago. The later branded injectable product obtained regulatory exclusivity based on its NDA approval, not a new chemical entity patent.

Event	Approximate timing	Commercial effect
Original neostigmine development	Mid-20th century	Core molecule protection expired long ago
Bloxiverz FDA approval	June 2013	New-product regulatory exclusivity began
Three-year approval exclusivity	Through approximately June 2016	Delayed certain competing 505(b)(2) approvals
Generic injectable competition	Following expiration of applicable exclusivity	Price and contract competition increased
Current market	Mature generic injectable market	Differentiation depends on supply and presentation

FDA’s Drugs@FDA database and Orange Book provide the controlling approval and exclusivity records.[3,4]

Are there Paragraph IV challenges for neostigmine methylsulfate?

Paragraph IV risk is limited for the core product because the active ingredient and conventional injectable formulation are old. A Paragraph IV filing would be relevant only if an applicant sought approval against a listed patent associated with a specific branded product or formulation.

The practical risk assessment is:

Risk area	Assessment
Active-ingredient patent	Low; historical protection expired
Conventional saline injection	Low patent barrier
Branded formulation patent	Product-specific; requires current Orange Book review
Ready-to-use syringe	Potential device and formulation claims
Combination with glycopyrrolate	Potential method, dosage-form, or device claims
Manufacturing process	Possible non-Orange Book protection
Trade secrets and know-how	More relevant than core patent claims

A generic applicant should still conduct a full patent search covering U.S. patents, foreign counterparts, continuation applications, device claims, and litigation records. Orange Book review alone will not identify every potentially relevant manufacturing or device patent.

Which companies compete in neostigmine methylsulfate injections?

The market has included branded and generic manufacturers such as Avadel, Hikma, Fresenius Kabi, Pfizer or Hospira-affiliated supply channels, and other approved injectable manufacturers depending on the product and market period. Manufacturer participation changes with acquisitions, discontinuations, contract manufacturing, and shortage conditions.

The competitive structure is fragmented compared with high-value specialty drugs. Hospitals generally evaluate:

• Unit price.
• National contract status.
• Back-order history.
• Concentration and vial size.
• Availability of preservative-free product.
• Packaging integrity.
• Shelf life.
• Ability to support operating-room demand.
• Supplier performance during shortages.

No reliable standalone revenue figure should be assigned to neostigmine methylsulfate without product-level sales data. Public companies typically report broader injectable, hospital, or generic portfolios rather than this product separately.

What commercial opportunities exist for neostigmine methylsulfate?

Ready-to-use prefilled syringes

The strongest formulation-adjacent opportunity is a prefilled syringe for operating-room use. Potential benefits include:

• Lower dose-preparation time.
• Reduced vial-to-syringe transfer.
• Lower medication-error risk.
• Less product waste.
• Better inventory standardization.

The product would need to address syringe compatibility, adsorption, extractables and leachables, silicone-oil interaction, particulate control, terminal sterilization or aseptic processing, and stability throughout the labeled shelf life.

The syringe itself could create device-related patent opportunities, but the commercial value would depend on measurable workflow savings and hospital conversion economics.

Co-packaged anticholinergic products

Neostigmine is commonly administered with glycopyrrolate or atropine. A co-packaged product could reduce preparation steps and improve protocol compliance.

Regulatory and commercial complications include:

• Separate dosing requirements.
• Different stability profiles.
• Potentially different storage conditions.
• Combination-product classification questions.
• Need to demonstrate that co-packaging does not create confusion.
• Procurement preferences for separate components.

A fixed-dose combination is more difficult than a co-package because patient dosing must be flexible and clinically appropriate.

Hospital shortage-resilient supply

Injectable neostigmine can create commercial value through dependable supply rather than formulation novelty. A manufacturer with redundant API sourcing, domestic fill-finish capacity, and high service levels could win contracts even without a differentiated patent estate.

Relevant manufacturing investments include:

• Dual-source active pharmaceutical ingredient qualification.
• Multiple sterile filling sites.
• Small-volume parenteral capacity.
• Automated visual inspection.
• Extended dating supported by stability data.
• Standardized vial and syringe components.

FDA drug-shortage records and ASHP shortage information can help identify supply gaps and contracting opportunities.[5,6]

Alternative vial sizes

Hospitals may value packaging that reduces waste. Potential presentations include:

• Low-dose vials for routine reversal.
• Higher-concentration vials for selected adult dosing.
• Unit-dose syringes.
• Anesthesia-cart packs.
• Institutional bulk packaging where permitted.

Vial-size differentiation is commercially useful only if the resulting price per administered dose is competitive. Smaller units may increase manufacturing cost but reduce partial-vial waste and preparation labor.

Stability-enhanced formulations

A formulation with improved stability could support:

• Longer shelf life.
• Greater temperature tolerance during distribution.
• Reduced degradation after opening or dilution.
• More reliable use in emergency and ambulatory settings.

Any stability claim must be linked to controlled degradation, impurity, particulate, container-closure, and sterility data. Stability alone does not create a defensible patent position unless the formulation produces an unexpected or technically distinctive result.

What FDA pathways apply to new neostigmine formulations?

ANDA under Section 505(j)

An ANDA is the most direct route for a product that matches a reference listed drug in active ingredient, dosage form, strength, route, and other required characteristics. Excipients may differ in some circumstances, but injectable products face tighter expectations for inactive-ingredient safety and pharmaceutical equivalence.

A materially different buffer system, device, concentration, or presentation can create obstacles to a straightforward ANDA strategy.

505(b)(2) application

A 505(b)(2) application may be suitable for:

• A new delivery system.
• A new concentration.
• A new combination or co-packaged product.
• A different route or dosage form.
• A formulation relying partly on published literature or FDA findings for the active ingredient.

A qualifying 505(b)(2) product may receive three-year marketing exclusivity for certain new clinical investigations essential to approval. The exclusivity would not recreate broad molecule-level protection.

Drug-device combination considerations

A prefilled syringe, cartridge, or autoinjector could trigger combination-product requirements. The sponsor would need to address:

• Device constituent performance.
• Human factors.
• Dose-delivery accuracy.
• Sterility assurance.
• Container-closure integrity.
• Compatibility between drug and device materials.

How strong is the patent estate for neostigmine methylsulfate?

The patent estate is weak for the active ingredient and conventional injectable formulation. It can be moderate for a narrowly defined product platform if the sponsor develops:

1. A clinically or operationally meaningful presentation.
2. A formulation with demonstrated stability or compatibility advantages.
3. A device configuration that reduces preparation errors.
4. Claims supported by comparative data.
5. Manufacturing claims that are difficult to design around.

Asset type	Expected patent strength	Commercial relevance
Neostigmine methylsulfate molecule	Very low	Historical only
Basic aqueous injection	Low	Limited exclusivity
Specific buffer and concentration	Low to moderate	Depends on unexpected results
Prefilled syringe	Moderate	Device and formulation claims
Dual-drug co-package	Moderate	Regulatory and procurement differentiation
Sterile manufacturing process	Moderate	Often confidential rather than Orange Book-listed
Supply-chain and quality system	Not patent-based	High practical value

Patent strategy should focus on a layered portfolio rather than one broad formulation claim. Useful layers may include composition, concentration, pH range, container closure, syringe materials, method of preparation, and use in a defined workflow.

What generic launch risks exist?

The principal generic launch risks are operational:

• Low unit prices.
• Limited market size.
• Established hospital contracts.
• API supply interruptions.
• Sterile manufacturing failures.
• Recall exposure.
• Low tolerance for particulate or container-closure defects.
• Difficulty securing profitable distribution.
• Competition from multiple approved suppliers.

A conventional vial product can launch relatively quickly if an approved reference product, suitable manufacturing site, and compliant formulation are available. A ready-to-use syringe may require more development time but can command a higher price if hospitals value labor reduction and medication safety.

How does neostigmine methylsulfate compare with sugammadex?

Sugammadex is the principal competitive alternative for reversal of certain neuromuscular blocking agents, especially rocuronium and vecuronium. Neostigmine remains relevant because it is inexpensive, familiar, and widely integrated into anesthesia protocols.

Attribute	Neostigmine methylsulfate	Sugammadex
Mechanism	Acetylcholinesterase inhibition	Encapsulation of selected steroidal neuromuscular blockers
Cost position	Generally lower	Generally higher
Anticholinergic coadministration	Usually required	Not routinely required
Reversal profile	Slower and dependent on blockade depth	More rapid and predictable for labeled agents
Formulation opportunity	Syringes, co-packaging, shortage supply	Concentration, vial, and ready-to-use formats
Patent position	Mature generic market	More significant historical product and formulation protection

This competition limits pricing power but supports a durable low-cost market for appropriate patients and institutional protocols.[7]

Key Takeaways

• Neostigmine methylsulfate is a mature injectable generic with no meaningful active-ingredient exclusivity.
• The best baseline formulation is usually a preservative-free aqueous injection using water for injection, sodium chloride, and controlled pH adjustment.
• Citrate buffering may improve pH control but increases formulation and sameness considerations.
• The strongest commercial opportunities are prefilled syringes, co-packaged anticholinergics, optimized vial sizes, and shortage-resilient supply.
• Conventional formulation patents are likely weak unless supported by unexpected stability, compatibility, or handling data.
• A 505(j) pathway is appropriate for a pharmaceutically equivalent generic; a 505(b)(2) pathway may support a materially differentiated delivery system.
• The main business risks are sterile manufacturing, hospital contracting, low pricing, supply continuity, and competition from sugammadex.
• Revenue exposure is difficult to isolate because neostigmine sales are generally reported within broader injectable or hospital portfolios.

FAQs

Can neostigmine methylsulfate be formulated without sodium chloride?

Yes. Sodium chloride is commonly used for tonicity, but alternative tonicity agents may be evaluated. The sponsor must demonstrate acceptable osmolality, stability, injection tolerability, and regulatory suitability.

Is neostigmine methylsulfate suitable for a lyophilized product?

A lyophilized presentation is technically possible but commercially difficult to justify for a highly water-soluble, established injectable. Reconstitution time, packaging cost, dose-preparation burden, and added manufacturing complexity would need to produce a measurable advantage.

Could a neostigmine and glycopyrrolate product receive patent protection?

Potentially, but protection would likely require a specific composition, ratio, packaging configuration, stability profile, or administration system. Broad claims covering the clinical coadministration of the two drugs would face substantial prior-art exposure.

What excipient issues are most important for a prefilled neostigmine syringe?

The main issues are syringe-material compatibility, adsorption, silicone oil, extractables and leachables, particulate formation, container-closure integrity, dose accuracy, and long-term stability in the selected device.

Is neostigmine methylsulfate vulnerable to biosimilar competition?

No. Neostigmine methylsulfate is a chemically synthesized small molecule, not a biologic. Competition comes from conventional generic injectables and alternative reversal agents, not biosimilars.

References

1. U.S. Food and Drug Administration. (2013). Bloxiverz (neostigmine methylsulfate) injection prescribing information. https://www.accessdata.fda.gov
2. National Library of Medicine. (n.d.). DailyMed: Neostigmine methylsulfate injection. https://dailymed.nlm.nih.gov
3. U.S. Food and Drug Administration. (n.d.). Drugs@FDA: Bloxiverz, NDA 204078. https://www.accessdata.fda.gov/scripts/cder/daf/
4. U.S. Food and Drug Administration. (n.d.). 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
5. U.S. Food and Drug Administration. (n.d.). FDA drug shortages. https://www.accessdata.fda.gov/scripts/drugshortages/
6. American Society of Health-System Pharmacists. (n.d.). Drug shortages. https://www.ashp.org/drug-shortages
7. U.S. Food and Drug Administration. (2015). Bridion (sugammadex) prescribing information. https://www.accessdata.fda.gov