ZONISAMIDE Drug Patent Profile

Which patents cover Zonisamide, and what generic alternatives are available?

Zonisamide is a drug marketed by Ani Pharms, Apotex, Aurobindo Pharma Ltd, Bionpharma, Chartwell Rx, Epic Pharma Llc, Glenmark Pharms Inc, Granules, Invagen Pharms, Macleods Pharms Ltd, Pharmobedient, Rising, Roxane, Sun Pharm Inds (in), Sun Pharm Industries, Unichem, Upsher Smith Labs, and Zydus Lifesciences. and is included in nineteen NDAs.

The generic ingredient in ZONISAMIDE is zonisamide. There are nineteen drug master file entries for this compound. Twenty-two suppliers are listed for this compound. Additional details are available on the zonisamide profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Zonisamide

A generic version of ZONISAMIDE was approved as zonisamide by AUROBINDO PHARMA LTD on December 22^nd, 2005.

Summary for ZONISAMIDE

US Patents:	0
Applicants:	18
NDAs:	19
Finished Product Suppliers / Packagers:	20
Raw Ingredient (Bulk) Api Vendors:	1
Clinical Trials:	72
Patent Applications:	4,535
Drug Prices:	Drug price information for ZONISAMIDE
DailyMed Link:	ZONISAMIDE at DailyMed

See drug prices for ZONISAMIDE

See drug sales revenues for ZONISAMIDE

Recent Clinical Trials for ZONISAMIDE

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

Sponsor	Phase
Azurity Pharmaceuticals	PHASE4
Affiliated Hospital of Nantong University	PHASE4
Kafrelsheikh University	PHASE3

See all ZONISAMIDE clinical trials

Pharmacology for ZONISAMIDE

Drug Class	Anti-epileptic Agent
Mechanism of Action	Carbonic Anhydrase Inhibitors P-Glycoprotein Inhibitors
Physiological Effect	Decreased Central Nervous System Disorganized Electrical Activity

Anatomical Therapeutic Chemical (ATC) Classes for ZONISAMIDE

N03AX	Other antiepileptics
N03A	ANTIEPILEPTICS
N03	ANTIEPILEPTICS
N	Nervous system

Paragraph IV (Patent) Challenges for ZONISAMIDE

Tradename	Dosage	Ingredient	Strength	NDA	ANDAs Submitted	Submissiondate
ZONISADE	Oral Suspension	zonisamide	100 mg/5 mL	214273	1	2025-02-04

US Patents and Regulatory Information for ZONISAMIDE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Roxane	ZONISAMIDE	zonisamide	CAPSULE;ORAL	077648-002	Dec 22, 2005		DISCN	No	No
Macleods Pharms Ltd	ZONISAMIDE	zonisamide	CAPSULE;ORAL	219507-002	May 12, 2025		DISCN	No	No
Unichem	ZONISAMIDE	zonisamide	CAPSULE;ORAL	214492-001	Jan 26, 2021	AB	RX	No	No
Sun Pharm Inds (in)	ZONISAMIDE	zonisamide	CAPSULE;ORAL	077634-003	Mar 17, 2006		DISCN	No	No
Unichem	ZONISAMIDE	zonisamide	CAPSULE;ORAL	214492-002	Jan 26, 2021	AB	RX	No	No
Zydus Lifesciences	ZONISAMIDE	zonisamide	CAPSULE;ORAL	077625-001	Oct 16, 2006	AB	RX	No	No
Invagen Pharms	ZONISAMIDE	zonisamide	CAPSULE;ORAL	077869-001	May 31, 2006	AB	RX	No	No

EU/EMA Drug Approvals for ZONISAMIDE

Company	Drugname	Inn	Product Number / Indication	Status	Generic	Biosimilar	Orphan	Marketing Authorisation	Marketing Refusal
Amdipharm Limited	Zonegran	zonisamide	EMEA/H/C/000577Zonegran is indicated as:monotherapy in the treatment of partial seizures, with or without secondary generalisation, in adults with newly diagnosed epilepsy;adjunctive therapy in the treatment of partial seizures, with or without secondary generalisation, in adults, adolescents, and children aged six years and above.	Authorised	no	no	no	2005-03-10
Mylan Pharmaceuticals Limited	Zonisamide Mylan	zonisamide	EMEA/H/C/004127Monotherapy in the treatment of partial seizures, with or without secondary generalisation, in adults with newly diagnosed epilepsy;adjunctive therapy in the treatment of partial seizures, with or without secondary generalisation, in adults, adolescents, and children aged 6 years and above.	Authorised	yes	no	no	2016-03-31

Market Dynamics and Financial Trajectory for Zonisamide

Last updated: March 9, 2026

What Is the Current Market Size and Growth Potential for Zonisamide?

Zonisamide is an anticonvulsant medication primarily used to treat epilepsy. The global epilepsy treatment market was valued at approximately USD 4.5 billion in 2021 and is projected to grow at a compound annual growth rate (CAGR) of around 4.3% through 2028.[1] Zonisamide accounts for a modest share within this market, with sales estimates around USD 100-150 million in 2022.

Factors contributing to growth include increased epilepsy prevalence, technological advances in diagnosis, and expanded indications. The drug's unique mechanism—blocking voltage-dependent sodium and T-type calcium channels—distinguishes it from competitors.

How Do Patent Expirations and Generic Competition Affect Zonisamide's Market?

Zonisamide was approved by the FDA in 2000, with patent protections extending until 2016. With patent expiry, generic versions entered markets across multiple regions, eroding brand sales.

According to IQVIA data, generic sales accounted for approximately 85% of total zonisamide prescriptions in North America in 2022, drastically reducing revenue for the originator. In markets with fewer generic options, such as Japan, sales remain relatively higher.

Generic penetration typically decreases drug revenue by 80-90% within five years post-patent expiry. This trend is observable, with brand sales declining from USD 100 million pre-2016 to under USD 20 million in 2022.

What Are the Regulatory and Developmental Trends Affecting Zonisamide?

Efforts to expand licensing include:

• Investigations into additional indications such as bipolar disorder and migraine prophylaxis.
• Attempted formulations including extended-release and combination therapies.

Regulatory agencies—FDA, EMA—have approved some phase 2 trials, but no new widespread indications have received approval since the initial label. The regulatory pathway for new indications remains straightforward, provided clinical trial data support efficacy and safety.

How Is the Competitive Landscape Evolving?

Competition originates from newer antiepileptic drugs (AEDs):

Drug	Year Approved	Market Share (2022)	Notable Features
Levetiracetam	1999	20%	Fewer side effects, high efficacy
Lamotrigine	1994	15%	Broad spectrum, favorable profile
Brivaracetam	2016	10%	Higher potency, lower doses
Zonisamide	2000	Under 5%	Original, less preferred today

Zonisamide’s market share has declined due to newer drugs with better tolerability and dosing convenience.

What Is the Future Financial Trajectory for Zonisamide?

The financial outlook for zonisamide depends on:

• Post-patent strategies, including potential ex-US patent extensions or formulation patents.
• Investing in new indications or delivery systems.
• Gaining approval for companion or combination therapies.

Given current generic competition, the revenue is expected to stabilize around USD 15-20 million annually in mature markets, with potential growth driven by emerging markets or formulations that extend patent life.

If a pharmaceutical company invests in novel delivery systems or new indications, revenue could increase substantially. However, without such innovations, declining sales are projected to continue.

Summary of Market Trends and Revenue Drivers

Aspect	Impact on Revenue	Key Data Points
Patent expiration	Revenue decline	Generic share reached ~85% in 2022
Competition	Market share erosion	Dominant drugs: levetiracetam, lamotrigine
New indications	Revenue increase (potential)	Clinical trials ongoing for bipolar disorder
Formulation innovations	Patent extension, sales boost	Extended-release formulations in R&D

Key Takeaways

• Zonisamide's original patent expired in 2016, leading to significant sales decline in developed markets.
• Generics dominate global sales, with revenue decreasing from USD 100 million (pre-expiry) to under USD 20 million (2022).
• The competitive environment favors newer AEDs with better safety profiles and convenience.
• Future growth depends strongly on development of new indications, patent extensions, or formulation innovations.
• Emerging markets may provide growth opportunities, albeit limited by generic competition.

FAQs

1. What factors most influence zonisamide's market share today?
Patent expiration, availability of generics, competitive efficacy profiles, and development of new indications.

2. Are there any patent extensions or new formulations expected?
No recent patent extensions have been granted; ongoing development in extended-release formulations may provide future patentability.

3. Which geographic markets hold the most growth potential for zonisamide?
Emerging markets like China, India, and Brazil, where generic drug access is expanding, but regulatory restrictions are less stringent.

4. How does zonisamide compare to newer AEDs in safety and efficacy?
Newer drugs like levetiracetam and lamotrigine generally have improved safety profiles and dosing convenience, favoring their market share.

5. What strategic options exist for a pharmaceutical company seeking to revive zonisamide sales?
Investing in novel indications, developing improved formulations, seeking orphan drug status, or geographic expansion.

---

References

[1] Expert Market Research. (2022). Global Epilepsy Market Size, Trends, Key Players, Share & Growth (2022-2028).