AMMONUL Drug Patent Profile

When do Ammonul patents expire, and what generic alternatives are available?

Ammonul is a drug marketed by Bausch and is included in one NDA.

The generic ingredient in AMMONUL is sodium benzoate; sodium phenylacetate. There are one thousand four hundred and seventy-two drug master file entries for this compound. Seven suppliers are listed for this compound. Additional details are available on the sodium benzoate; sodium phenylacetate profile page.

Summary for AMMONUL

US Patents:	0
Applicants:	1
NDAs:	1
Raw Ingredient (Bulk) Api Vendors:	2
Clinical Trials:	2
Drug Prices:	Drug price information for AMMONUL
What excipients (inactive ingredients) are in AMMONUL?	AMMONUL excipients list
DailyMed Link:	AMMONUL at DailyMed

See drug prices for AMMONUL

Recent Clinical Trials for AMMONUL

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
Horizon Pharma Ireland, Ltd., Dublin Ireland	Phase 2
Horizon Pharma Ireland, Ltd., Dublin Ireland	Phase 1
Ucyclyd Pharma, Inc.	Phase 1

See all AMMONUL clinical trials

US Patents and Regulatory Information for AMMONUL

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Bausch	AMMONUL	sodium benzoate; sodium phenylacetate	SOLUTION;INTRAVENOUS	020645-001	Feb 17, 2005		DISCN	Yes	No

AMMONUL Market Dynamics, Revenue Outlook, Competition, and Exclusivity

Last updated: August 2, 2026

AMMONUL is an injectable ammonia-scavenging therapy containing sodium phenylacetate and sodium benzoate. It is used for the emergency treatment of acute hyperammonemia in patients with urea cycle disorders, together with hemodialysis and dietary protein restriction when clinically indicated.[1] Its market is small, specialist-driven, and hospital-based. Revenue visibility is limited because the product is not reported as a standalone commercial segment by its current corporate owner, Amgen.

AMMONUL's financial trajectory is shaped less by broad prescription volume than by emergency use, hospital formulary access, manufacturing capacity, and the absence of a direct generic substitute with comparable regulatory status and ready-to-use presentation. The main commercial threat is substitution by chronic oral nitrogen-scavenging products, particularly glycerol phenylbutyrate and sodium phenylbutyrate, rather than a conventional retail generic launch.

What is AMMONUL and how is it used?

AMMONUL is an intravenous combination of sodium phenylacetate and sodium benzoate. It is approved for patients with urea cycle disorders who present with acute hyperammonemia or are at risk of rapidly developing hyperammonemia.[1]

The product operates through two nitrogen-scavenging mechanisms:

• Sodium benzoate conjugates with glycine to form hippurate, which is eliminated through the kidneys.
• Sodium phenylacetate conjugates with glutamine to form phenylacetylglutamine, which is also excreted renally.

AMMONUL is administered in a hospital setting. Treatment is generally paired with nutritional management and, in severe cases, hemodialysis. The product is not a chronic maintenance therapy for most patients.

AMMONUL product profile

Attribute	AMMONUL
Active ingredients	Sodium phenylacetate and sodium benzoate
Dosage form	Intravenous injection
Primary indication	Acute hyperammonemia associated with urea cycle disorders
Prescriber setting	Emergency departments, intensive-care units, metabolic centers
Patient population	Rare-disease patients, including pediatric and adult patients
FDA approval	Approved for acute management of urea-cycle-related hyperammonemia
Chronic-use role	Limited; generally an acute rescue product
Main alternatives	Hemodialysis, sodium phenylbutyrate, glycerol phenylbutyrate, supportive care
Current corporate ownership	Amgen, following its acquisition of Horizon Therapeutics

What is the FDA regulatory status of AMMONUL?

AMMONUL is an FDA-approved prescription drug for acute hyperammonemia due to urea cycle disorders. The FDA-approved labeling specifies dosing by body weight and distinguishes loading and maintenance administration.[1]

The product has orphan-drug characteristics because urea cycle disorders are rare inherited metabolic diseases. Orphan-drug status can provide seven years of market exclusivity from approval for the approved indication, subject to statutory exceptions. That period is separate from patent protection and does not prevent all forms of competition after expiration.

AMMONUL's commercial value is supported by its role in an emergency-care protocol. Physicians and hospitals may maintain access because delayed treatment of severe hyperammonemia can lead to neurologic injury or death. This creates a demand profile that differs from routine outpatient medicines.

What is the Orange Book status of AMMONUL?

AMMONUL does not appear to have a current market position based on a durable, active patent estate comparable with newer specialty drugs. The product's core active ingredients are established compounds, and the principal commercial protections associated with the original product have likely expired.

The key practical point is that AMMONUL's market access does not depend solely on patent exclusivity. Its position is supported by:

1. FDA approval for an acute injectable use.
2. Hospital protocols and metabolic-center familiarity.
3. Specialized manufacturing and quality-control requirements.
4. Limited patient volume.
5. The need for immediate availability during a metabolic crisis.

The Orange Book is less commercially decisive for AMMONUL than for a high-volume branded oral medicine. A prospective competitor would still need to establish an appropriate injectable product, obtain FDA approval, meet supply requirements, and secure hospital adoption.

When does AMMONUL lose exclusivity?

AMMONUL's meaningful exclusivity period has already elapsed if measured by the original approval-era patent and orphan-drug framework. The product is not dependent on a currently visible patent cliff comparable with products that have large active Orange Book patent portfolios.

The commercial exclusivity timeline is best understood as follows:

Period	Commercial event
Original approval era	FDA approval established AMMONUL as an acute intravenous therapy for urea cycle disorders
Post-approval period	Orphan-drug and product-specific market protections supported the branded product
Following expiry of original protections	Competition became legally possible, although market entry remained constrained by the small hospital market
Current period	Supply reliability, manufacturing capability, regulatory approval, and clinical familiarity are more important than patent duration

No major AMMONUL-specific patent expiration date currently drives a clearly identifiable revenue cliff. Public company filings also do not identify a pending AMMONUL patent event that would materially change Amgen's reported financial outlook.

How large is the AMMONUL market?

The addressable population is small. Urea cycle disorders affect an estimated 1 in 35,000 live births in the United States, although prevalence estimates vary by disorder, ascertainment method, and population.[2] The acute-treatment market is smaller than the total diagnosed population because most patients do not receive repeated AMMONUL treatment.

Demand is concentrated in:

• Pediatric metabolic centers.
• Academic hospitals.
• Emergency departments.
• Intensive-care units.
• Transplant and inherited-metabolic-disease programs.

The product's unit volume is therefore likely modest. Revenue can remain meaningful relative to volume if emergency injectable pricing is high and hospital purchasing is concentrated, but the product is unlikely to be a major contributor to a multinational pharmaceutical company's consolidated sales.

What drives AMMONUL demand?

Hospital utilization depends on the number of acute metabolic decompensations, recognition of urea cycle disorders, availability of metabolic specialists, and local treatment protocols. Diagnosis of late-onset disease can increase demand, but improved chronic management can reduce emergency episodes.

Demand may also be affected by:

• Increased survival of patients with severe urea cycle disorders.
• Greater awareness of adult-onset and partial enzyme deficiencies.
• Improved emergency diagnostic testing.
• Availability of chronic nitrogen-scavenging therapies.
• Hospital stocking policies.
• Supply interruptions involving competing products.

AMMONUL has a countercyclical feature within the rare-disease market: clinical need is urgent even when patient volume is low. Hospitals may retain the product because the cost of not having an ammonia-scavenging agent during a crisis is high.

Who owns AMMONUL and what is the financial disclosure?

AMMONUL was associated with Ucyclyd Pharma, which became part of Horizon Pharma. Horizon was acquired by Amgen in 2023 in a transaction valued at approximately $27.8 billion.[3][4]

Amgen does not publicly report AMMONUL as a separate revenue line in its annual filings. The product is therefore financially immaterial or not separately disclosed at the consolidated-company level, or its sales are aggregated within a broader portfolio category.

AMMONUL ownership timeline

Date	Event
Original commercialization	AMMONUL commercialized as a specialty metabolic product
2014-2015 period	Ucyclyd Pharma became associated with Horizon Pharma through corporate transactions
2023	Amgen completed its acquisition of Horizon Therapeutics
Current position	AMMONUL is part of Amgen's inherited Horizon product portfolio, but product-level sales are not separately reported

Because AMMONUL revenue is not separately disclosed, precise annual sales, gross margin, and operating-profit estimates cannot be established from public filings. Any exact figure presented without a company disclosure or audited product-level source would be speculative.

What is the financial trajectory for AMMONUL?

AMMONUL's financial trajectory is likely mature and stable rather than high-growth. The product has a narrow indication, limited patient population, and little evidence of a near-term volume expansion strategy.

The principal financial characteristics are:

• Low absolute market size.
• High clinical urgency.
• Specialty or hospital pricing.
• Limited promotional spending relative to primary-care medicines.
• Low exposure to retail prescription churn.
• Potentially attractive gross margin if manufacturing costs are controlled.
• Limited strategic importance to Amgen's consolidated revenue.

Revenue is likely to be influenced more by price, contracting, supply continuity, and hospital purchasing than by patient acquisition. A price increase could materially affect sales in a small market, but reimbursement and hospital budget constraints limit pricing flexibility.

Is AMMONUL a material revenue driver for Amgen?

No public evidence indicates that AMMONUL is a material revenue driver for Amgen. Amgen's reported revenue is dominated by large products such as Repatha, Prolia, XGEVA, Enbrel, Otezla, and other high-volume biologic or specialty medicines.[4] AMMONUL is not separately identified among the company's principal products or major revenue contributors.

Its strategic value is more likely portfolio-based. A mature rare-disease product can provide recurring revenue, specialist relationships, and commercial infrastructure with limited incremental promotional cost. That does not make it financially significant at the parent-company level.

How does AMMONUL compare with Ravicti and BUPHENYL?

AMMONUL is an acute intravenous rescue product. Ravicti and BUPHENYL are oral nitrogen-scavenging therapies used primarily for chronic management of urea cycle disorders.

Product	Active ingredient	Route	Primary role	Competitive relationship
AMMONUL	Sodium phenylacetate and sodium benzoate	Intravenous	Acute hyperammonemia	Hospital rescue
BUPHENYL	Sodium phenylbutyrate	Oral	Chronic management	May reduce acute episodes
RAVICTI	Glycerol phenylbutyrate	Oral liquid	Chronic management	Indirect substitute; not a direct IV replacement
Hemodialysis	Extracorporeal therapy	Dialysis	Rapid ammonia removal	Adjunct or alternative in severe cases

Ravicti is commercially more valuable per patient because chronic dosing produces recurring outpatient utilization. AMMONUL generally receives episodic use, although emergency pricing can be substantial.

Chronic therapy can reduce AMMONUL demand by preventing decompensation. It can also increase the number of diagnosed and managed patients who have access to rescue protocols. The net effect depends on treatment adherence, disease severity, and hospital practice.

What generic entry risks exist for AMMONUL?

The legal risk from a conventional Paragraph IV challenge appears limited because AMMONUL lacks the type of active, high-value patent estate that usually attracts major ANDA litigation.

The more relevant entry risks are regulatory and operational:

Injectable product development

A competitor would need to develop a stable intravenous formulation containing the two active ingredients at appropriate concentrations. The product must meet FDA requirements for sterility, potency, impurities, container closure, labeling, and manufacturing controls.

Limited commercial opportunity

The addressable market may be too small to justify development costs for many generic manufacturers. A potential entrant would need to estimate hospital demand, acquisition cost, pricing pressure, and supply obligations.

Manufacturing barriers

Manufacturing complexity may not be technologically insurmountable, but sterile injectable production has higher compliance and capital requirements than many oral generic products. A competitor also would need dependable supply of both active ingredients and validated fill-finish capacity.

Hospital adoption

Hospitals may purchase an approved generic if it offers a clear price advantage. In an emergency product category, they may also value reliable supply, established distribution, and consistent availability.

Which companies are challenging AMMONUL?

No major active Paragraph IV litigation involving AMMONUL is identified as a central market event in the public company disclosures reviewed for this analysis. The competitive field is more likely to include potential generic injectable developers and suppliers of alternative ammonia-lowering therapies than branded challengers litigating an active patent portfolio.

Ravicti and BUPHENYL compete for chronic urea-cycle-disorder treatment but are not direct substitutes for an emergency intravenous product. Hemodialysis remains the most important clinical alternative in severe cases.

What patent litigation and settlement agreements affect AMMONUL?

There is no identified current patent litigation or settlement agreement that creates a known near-term AMMONUL launch date or damages exposure. The product's market risk is therefore not principally litigation-driven.

Any future generic applicant could pursue an abbreviated new drug application if an appropriate reference-product pathway and FDA requirements are satisfied. A Paragraph IV certification would matter only if an unexpired listed patent were relevant to the proposed product. The commercial feasibility of such an entry remains more important than patent litigation.

What is the geographic coverage for AMMONUL?

AMMONUL's strongest commercial position is in the United States, where FDA approval, hospital protocols, and specialist metabolic centers support use. International availability varies by country and may depend on local approvals, importation, hospital procurement, and rare-disease funding policies.

Geographic expansion is constrained by:

• Small patient populations.
• Country-specific regulatory filings.
• Different orphan-drug reimbursement systems.
• Hospital rather than retail distribution.
• Requirements for emergency availability.
• Local treatment guidelines.

The product is not a conventional global blockbuster. Its geographic value is tied to access in specialized hospitals rather than broad market penetration.

What is the outlook for AMMONUL revenue?

The base-case outlook is for mature, low-growth revenue with episodic volume and limited strategic disclosure. Revenue may remain durable if Amgen maintains supply, hospital access, and pricing. A generic injectable entrant could reduce price and market share, but the probability and timing of entry are difficult to infer from patent data alone.

Scenario analysis

Scenario	Market effect	Financial implication
Stable branded supply	AMMONUL retains hospital formulary position	Flat to modestly growing revenue
Chronic therapy reduces crises	Lower acute utilization	Volume pressure
Supply disruption	Hospitals seek alternatives or stock competing products	Temporary share loss
Approved injectable generic	Price competition and formulary substitution	Revenue and margin decline
Improved diagnosis and specialist access	More treated patients and rescue use	Moderate volume support
Hospital cost controls	Greater generic or alternative use	Net price pressure

AMMONUL's long-term value is likely defensive rather than expansionary. Its revenue base can be resilient because the indication is serious and the product is embedded in emergency treatment pathways. It is unlikely to generate the growth profile associated with newer rare-disease launches.

Key Takeaways

• AMMONUL is an FDA-approved intravenous treatment for acute hyperammonemia associated with urea cycle disorders.
• Its market is small, hospital-based, and concentrated in metabolic-care centers.
• Amgen owns the product through its acquisition of Horizon Therapeutics, but does not separately disclose AMMONUL revenue.
• The product's original patent and orphan exclusivity periods are not the primary current commercial barrier.
• No major active Paragraph IV litigation or settlement-driven generic launch is identified.
• The main competitive products, Ravicti and BUPHENYL, are chronic oral therapies rather than direct IV substitutes.
• Revenue is likely mature and recurring, with upside from price and supply continuity rather than significant patient-volume expansion.
• The largest long-term commercial risk is an FDA-approved injectable generic or a shift toward chronic therapies that reduce acute metabolic crises.

FAQs About AMMONUL Market Dynamics

Is AMMONUL a specialty drug?

Yes. AMMONUL is a rare-disease specialty medicine used mainly in hospitals and metabolic treatment centers for acute hyperammonemia.

Does AMMONUL have a biosimilar risk?

No. AMMONUL is a small-molecule injectable product, not a biologic. Biosimilar regulation does not apply. Any competitor would pursue a generic-drug or other applicable small-molecule pathway.

Is AMMONUL available as an oral medicine?

No. AMMONUL is an intravenous product. Oral sodium phenylbutyrate and glycerol phenylbutyrate are separate products used mainly for chronic management.

Could a generic AMMONUL launch reduce hospital costs?

Yes. An approved therapeutically equivalent injectable product could create price competition. The impact would depend on hospital contracting, supply reliability, and the generic's ability to maintain sterile manufacturing capacity.

Why is AMMONUL commercially relevant if its patient population is small?

The product is used during medical emergencies in which rapid ammonia reduction is clinically important. Hospitals may maintain inventory despite low utilization because the cost of lacking an appropriate rescue therapy can be high.

References

1. U.S. Food and Drug Administration. (2023). AMMONUL (sodium phenylacetate and sodium benzoate) injection prescribing information. FDA.

2. National Organization for Rare Disorders. (n.d.). Urea cycle disorders. NORD.

3. Amgen Inc. (2023). Amgen completes acquisition of Horizon Therapeutics plc. Amgen investor relations.

4. Amgen Inc. (2024). 2023 annual report. Amgen.