Prescription medicine
Ethosuximide Brand names: Zarontin
Ethosuximide (Zarontin) is a prescription medicine with an FDA approval on record since 1960. FDA's NDC Directory lists it from 9 generic labelers, and pharmacies paid $0.243 per ethosuximide 250 mg capsule in the October 7, 2026 NADAC survey.
- Generic listed
Check it at the source: the ethosuximide FDA label on DailyMed (effective June 11, 2026, Chartwell Governmental & Specialty RX, LLC.); the NDA 12380 record on Drugs@FDA; every ethosuximide label on DailyMed.
Highlights of the record
FDA label of June 11, 2026; NDC Directory, Drugs@FDA and Orange Book, October 8, 2026; NADAC October 7, 2026
Used for
From the label: indications and usageEthosuximide is indicated for the control of absence (petit mal) epilepsy.
Forms and strengths
- 250 mg
- 250 mg/5ml
Solution; capsule; liquid-filled capsule.
On the market
- Earliest approval on file
- November 2, 1960 Zarontin, Parke Davis; Drugs@FDA’s file, where older or withdrawn approvals can be missing
- Generic approvals
- 9 first February 13, 1974; 7 with a marketed status in Drugs@FDA
- Labelers listed (NDC)
- 9 of which 9 under generic applications, 1 under brand applications, repackagers included
Supply and safety
- Pharmacy cost (NADAC)
- $0.243 per capsule Ethosuximide 250 mg capsule
- Shortage (FDA)
- No current entry
- Recalls by its makers (FDA)
- 4 since 2018 0 Class I among all firms' recalls; latest July 29, 2021
- FAERS reports
- 2,489 through July 30, 2026
What is ethosuximide used for?
From the label: indications and usageEthosuximide is indicated for the control of absence (petit mal) epilepsy.
Conditions named in the indications of ethosuximide's FDA labels, with every medicine labeled for each:
From other ethosuximide labelsSeizures and epilepsy: INDICATIONS AND USAGE Ethosuximide is indicated for the control of absence (petit mal) epilepsy.
FDA pharmacologic class: Anti-epileptic Agent.
Source: FDA drug label (Ethosuximide), Chartwell Governmental & Specialty RX, LLC., effective June 11, 2026 (SPL set a825265d-ace9-4463-a16d-f6d5e1e31188), via openFDA; the full label on DailyMed
What does the patient leaflet for ethosuximide say first?
The FDA-approved Medication Guide or Patient Information that comes with the medicine, in its own words.
From the patient leaflet: What is the most important information I should know about ethosuximide oral solution?Do not stop taking ethosuximide oral solution without first talking to your healthcare provider. Stopping ethosuximide oral solution suddenly can cause serious problems. Ethosuximide oral solution can cause serious side effects, including: Rare but serious blood problems that may be life-threatening. Call your healthcare provider right away if you have: fever, swollen glands, or sore throat that come and go or do not go away frequent infections or an infection that does not go away easy bruising red or purple spots on your body bleeding gums or nose bleeds severe fatigue or weakness Drug reactions that may affect different parts of the body such as your liver, kidneys, heart, or blood cells. You may or may not have a rash with these types of reactions. These reactions can be very serious and can cause death. Call your healthcare provider right away if you have any of these symptoms: joint pain and swelling muscle pain fatigue, weakness low-grade fever pain in the chest that is worse with breathing skin rash swollen lymph glands swelling of your face yellowing of your skin or the white part of your eyes Like other antiepileptic drugs, ethosuximide oral solution may cause suicidal thoughts or actions in a very small number of people, about 1 in 500. […]
From the patient leaflet: What should I avoid while taking ethosuximide oral solution?Do not drink alcohol or take other medicines that make you sleepy or dizzy while taking ethosuximide oral solution without first talking to your healthcare provider. Ethosuximide oral solution taken with alcohol or medicines that cause sleepiness or dizziness may make your sleepiness or dizziness worse. Do not drive, operate heavy machinery, or do other dangerous activities until you know how ethosuximide oral solution affects you. Ethosuximide oral solution can slow your thinking and motor skills.
From the patient leaflet: How should I store ethosuximide oral solution?Store ethosuximide oral solution at 20º to 25ºC (68º to 77ºF). Preserve in tight containers. Protect from freezing and light. Keep ethosuximide oral solution and all medicines out of the reach of children.
Source: FDA drug label (Ethosuximide), Chartwell Governmental & Specialty RX, LLC., effective June 11, 2026 (SPL set a825265d-ace9-4463-a16d-f6d5e1e31188), via openFDA; the full label on DailyMed
Is there a generic for ethosuximide (Zarontin)?
The FDA approved the first generic ethosuximide on February 13, 1974. 9 generic applications are approved; 7 of them carry a current (not discontinued) marketing status in Drugs@FDA; that status is not evidence that the generic is on sale.
FDA's NDC Directory lists ethosuximide from 9 labelers under a generic (ANDA) application and from 1 brand labeler. A listing means the company has registered the product for sale; it does not show that every pharmacy stocks it.
- 1960 earliest approval on file
- 1974 first generic approved
- red ticks recalls
Source: Drugs@FDA, FDA NDC Directory and the Orange Book (openFDA bulk files, October 8, 2026)
What do pharmacies pay for ethosuximide (Zarontin)?
In CMS's NADAC survey of October 7, 2026, pharmacies paid $0.243 per Ethosuximide 250 mg capsule, up 10% from $0.221 on October 8, 2025. The chart's scale runs from the lowest to the highest price shown, not from zero. NADAC is what retail pharmacies paid their wholesalers, per unit, in CMS's monthly survey; what a patient pays depends on insurance and the pharmacy.
- Ethosuximide 250 mg capsule (generic)
- Zarontin 250 mg capsule (brand)
| Strength and form | Brand or generic | Pharmacy cost | 30 tablets, or one pen or vial | 12-month change |
|---|---|---|---|---|
| Ethosuximide 250 mg capsule | Generic | $0.243 per capsule | $7.30 | +10% |
| Ethosuximide 250 mg/5 mL solution | Generic | $0.100 per mL | n/a | +4% |
| Zarontin 250 mg capsule | Brand | $1.31 per capsule | $39.26 | +3% |
Source: CMS National Average Drug Acquisition Cost (NADAC) survey, October 7, 2026: what retail pharmacies paid per unit; not a counter price
Has ethosuximide been recalled?
The FDA's Enforcement Report lists 4 recalls naming ethosuximide since 2018: 0 Class I (the most serious), 2 Class II, 2 Class III; 0 still ongoing. A recall names products and lots, not every product of the medicine.
| Started | Class | Company | Reason |
|---|---|---|---|
| July 29, 2021 | Class II | PAI Holdings, LLC. dba Pharmaceutical Associates Inc | Lack of CGMP: This recall is being carried out due to potential for carry over of Senna Syrup. |
| September 12, 2019 | Class III | Pfizer Inc. | Labeling: Incorrect or Missing Lot and/or Exp Date. The expiry date on the product label is incorrect. … |
| August 24, 2018 | Class II | Akorn, Inc. | Failed Impurities/Degradation Specifications: Out of specification (OOS) results for unspecified impurity. |
Source: FDA Enforcement Report (drug recalls) via openFDA, through October 8, 2026
What does the ethosuximide label say about other medicines?
The ethosuximide label names 4 other medicines in its interaction, contraindication or warning sections. The labels of 12 other medicines name ethosuximide. The sentences are the labels' own; a label lists what its studies and reports found, not every interaction.
| Medicine named | Section | What the label says |
|---|---|---|
| Divalproex | drug interactions | Drug Interactions: Since Zarontin (ethosuximide) may interact with concurrently administered antiepileptic drugs, periodic serum level determinations of these drugs may be necessary (e.g., ethosuximide may elevate phenytoin serum levels and valproic acid has been reported to both increase and decrease ethosuximide … |
| Phenobarbital | warnings | Data are more extensive with respect to phenytoin and phenobarbital, but these are also the most commonly prescribed anticonvulsants; less systematic or anecdotal reports suggest a possible similar association with the use of all known anticonvulsant drugs. |
| Phenytoin | warnings | Data are more extensive with respect to phenytoin and phenobarbital, but these are also the most commonly prescribed anticonvulsants; less systematic or anecdotal reports suggest a possible similar association with the use of all known anticonvulsant drugs. |
| Valproic acid | drug interactions | Drug Interactions: Since Zarontin (ethosuximide) may interact with concurrently administered antiepileptic drugs, periodic serum level determinations of these drugs may be necessary (e.g., ethosuximide may elevate phenytoin serum levels and valproic acid has been reported to both increase and decrease ethosuximide … |
Other labels that name ethosuximide
Source: FDA drug label (Ethosuximide), Chartwell Governmental & Specialty RX, LLC., effective June 11, 2026 (SPL set a825265d-ace9-4463-a16d-f6d5e1e31188), via openFDA; the full label on DailyMed
What do FAERS reports show for ethosuximide?
The FDA Adverse Event Reporting System holds 2,489 reports that list ethosuximide among the medicines taken, through July 30, 2026, each a report of something that happened, not proof the medicine caused it; 63 are coded as a death and 581 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is.
Reports received each year
The most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026
What else is labeled for the same conditions as ethosuximide?
20 other medicines are given the same way (oral) and in the same FDA class as ethosuximide or labeled mainly for the same use (seizures and epilepsy), the same class first. Seizures and epilepsy lists all 27 medicines labeled for it, by any route. The first 8 are below. They are listed as records, not as substitutes: whether one can replace another is a prescriber's decision.
| Medicine | Shared indication | Generic labelers (oral) | Pharmacy cost | Shortage |
|---|---|---|---|---|
| Gabapentin | Seizures and epilepsy | 87 labelers | $0.0218 per capsule 100 mg capsule | No current entry |
| Lamotrigine | Seizures and epilepsy | 50 labelers | $0.0268 per tablet 25 mg tablet | A presentation being discontinued |
| Divalproex | Seizures and epilepsy | 44 labelers | $0.194 per tablet 500 mg tablet | No current entry |
| Oxcarbazepine | Seizures and epilepsy | 43 labelers | $0.167 per tablet 300 mg tablet | No current entry |
| Zonisamide | Seizures and epilepsy | 20 labelers | $0.106 per capsule 100 mg capsule | No current entry |
| Valproic acid | Seizures and epilepsy | 19 labelers | $0.243 per capsule 250 mg capsule | Listed; available |
| Phenytoin | Seizures and epilepsy | 23 labelers | $0.145 per capsule 100 mg capsule | No current entry |
| Primidone | Seizures and epilepsy | 21 labelers | $0.0914 per tablet 50 mg tablet | No current entry |
Every medicine labeled for the same conditions as ethosuximide
Source: FDA drug labels (indications), NDC Directory, NADAC of October 7, 2026, FDA shortages (October 8, 2026)
What next?
- Alternatives to ethosuximide
- 20 medicines for the same use
- Other anti-seizure medicines
- the pharmacologic class, with prices and generics
- Ethosuximide side effects
- the label's list beside FAERS reports
- Check an interaction
- what two or more labels say about each other