Comprehensive medication guide to Zarontin including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$10–$50 copay per month for generic ethosuximide on most commercial plans and Medicare Part D; generic is typically Tier 1–2 without prior authorization. Brand Zarontin may require prior authorization; Medicare Part D does not cover brand Zarontin.
Estimated Cash Pricing
$200–$580 retail for a 30-day supply without insurance; as low as $33.61 with a GoodRx coupon or $35.88 with SingleCare for generic ethosuximide. Brand-name Zarontin oral solution retails for approximately $579.83.
Medfinder Findability Score
55/100
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Zarontin is the brand name for ethosuximide, a succinimide anticonvulsant medication FDA-approved for the treatment of absence (petit mal) epilepsy in patients aged 3 and older. It has been in clinical use since the 1960s and remains the first-line, gold-standard treatment for childhood absence epilepsy.
Absence seizures are brief lapses in consciousness—typically 5 to 30 seconds—characterized by a sudden blank stare and temporary unresponsiveness. They can occur dozens to hundreds of times per day in untreated patients, particularly in children. Zarontin is specifically designed to control this seizure type.
Zarontin is available as 250 mg soft gelatin capsules and as a 250 mg/5 mL raspberry-flavored oral solution (manufactured by Pfizer). Generic ethosuximide capsules are manufactured by several companies. Adults typically take 500 mg to 1,500 mg daily; children aged 3–6 usually start at 250 mg daily.
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Zarontin (ethosuximide) works by blocking T-type voltage-gated calcium channels in thalamocortical neurons—the brain cells in the thalamus that communicate with the cerebral cortex. These T-type channels are responsible for generating the low-threshold calcium currents that produce the characteristic 3 Hz spike-and-wave discharges seen on EEG during absence seizures.
By blocking these channels, ethosuximide suppresses the abnormal thalamic oscillations that trigger absence seizures—preventing the brief lapses in consciousness that define this condition. This targeted mechanism is specific to absence seizures; ethosuximide does not prevent other seizure types such as generalized tonic-clonic or focal seizures.
Ethosuximide is metabolized by the liver's CYP3A4 enzyme system and reaches a therapeutic blood level (40–100 μg/mL) at steady state in approximately 4–7 days. It is notable for causing fewer attentional side effects in children compared to the alternative valproic acid, as confirmed in the landmark NEJM childhood absence epilepsy trial (Glauser et al., 2010).
250 mg — capsule
Soft gelatin capsule; available as generic ethosuximide
250 mg/5 mL — oral solution
Raspberry-flavored liquid; available as brand Zarontin (Pfizer) and some generics; 1 teaspoon (5 mL) = 250 mg
Zarontin scores 55 out of 100 on our findability scale, meaning it can be moderately difficult to locate at retail pharmacies. While there is no active FDA-listed shortage as of 2026, Zarontin is a niche medication that treats a relatively small patient population. Most large chain pharmacies do not keep it on their regular shelves—they must special-order it, which can take 1 to 5 business days.
Only a small number of manufacturers produce generic ethosuximide, making the supply chain more vulnerable to disruptions. Wholesaler allocation during constrained supply periods tends to favor high-volume pharmacy accounts, leaving smaller and rural pharmacies with less reliable access. Intermittent regional stockouts are common.
If your pharmacy doesn't have Zarontin in stock, use medfinder to find pharmacies near you that currently have it available. medfinder calls pharmacies on your behalf and texts you results—no hold music required. Always try both formulations (capsules and oral solution), as one may be in stock when the other is not.
Because Zarontin (ethosuximide) is not a controlled substance, any licensed prescriber with appropriate authority can write a prescription. In practice, the diagnosis of absence epilepsy typically requires a specialized evaluation—usually including an EEG—which is performed by a neurologist. Ongoing prescriptions may then be managed by a variety of provider types.
Telehealth prescriptions for ethosuximide are available in most states for established patients with well-controlled absence epilepsy. New diagnoses typically still require an in-person evaluation and EEG confirmation before prescribing is appropriate.
No. Zarontin (ethosuximide) is not a controlled substance. It is not classified under any DEA schedule (I–V). This means there are no special prescribing restrictions, no mandatory DEA authorization required, no early refill limitations, and no special prescription forms needed beyond a standard prescription.
Any licensed prescriber—including physicians, nurse practitioners, and physician assistants with prescribing authority—can write a prescription for ethosuximide. Telehealth prescriptions are permitted in most states without the special restrictions that apply to controlled substances. This is in contrast to some other medications sometimes used for seizure disorders (such as benzodiazepines like clonazepam or clobazam) which are Schedule IV controlled substances.
Common side effects (often mild and improve over time):
Contact your doctor immediately if you experience:
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Valproic Acid (Depakote)
Equivalent efficacy to ethosuximide for absence seizures (44% vs 45% seizure-free at 12 months). Broader spectrum, useful for mixed seizure types. Higher side effect rate; avoid in women of childbearing age due to teratogenicity.
Lamotrigine (Lamictal)
Second-line option; less effective for absence seizures (21% seizure-free vs 45% for ethosuximide). Better tolerated; preferred for women of childbearing age. Requires slow titration to reduce SJS risk.
Clonazepam (Klonopin)
Benzodiazepine; adjunctive or bridge therapy only. Effective short-term but risk of tolerance and dependence limits long-term use. Schedule IV controlled substance.
Clobazam (Onfi)
Benzodiazepine with some evidence for absence seizures as add-on therapy. Schedule IV. Not recommended as monotherapy for absence epilepsy.
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Valproic Acid (Depakote)
moderateVariable interaction: valproic acid can both increase and decrease ethosuximide levels; monitor drug levels when used together.
Phenytoin (Dilantin)
moderateBidirectional: ethosuximide may elevate phenytoin levels; phenytoin (CYP3A4 inducer) can reduce ethosuximide levels. Monitor both.
Carbamazepine (Tegretol)
moderateStrong CYP3A4 inducer; can significantly reduce ethosuximide blood levels, risking breakthrough seizures.
Phenobarbital
moderateCYP3A4 inducer; reduces ethosuximide levels. Dose adjustment may be needed.
Isoniazid
moderateMay slow ethosuximide metabolism, increasing blood levels and toxicity risk.
Rifampin (Rifampicin)
majorStrong CYP3A4 inducer; significantly increases ethosuximide clearance, potentially causing seizure breakthrough.
Alcohol and CNS Depressants
majorAdditive CNS depression and sedation. Avoid concurrent use.
Strong CYP3A4 Inhibitors (e.g., adagrasib, idelalisib)
majorIncrease ethosuximide blood levels; avoid coadministration.
Zarontin (ethosuximide) is one of the most well-established and effective treatments in all of epilepsy medicine. With decades of clinical use and Class I randomized trial evidence supporting its use as first-line therapy for childhood absence epilepsy, it remains the treatment of choice for this specific seizure type. Its favorable cognitive side effect profile compared to valproic acid makes it especially appropriate for school-age children.
The main challenge with Zarontin in 2026 is not clinical—it's logistical. Because absence epilepsy affects a relatively small patient population, many pharmacies don't routinely stock ethosuximide. Patients need to plan ahead, refill early, and be prepared to try multiple pharmacies. Cost barriers can be substantially reduced with GoodRx or SingleCare coupons, bringing generic ethosuximide to under $35 per month.
If you are having difficulty finding Zarontin at your local pharmacy, medfinder can help you locate a pharmacy near you that has it in stock. And remember: never stop ethosuximide abruptly—always consult your neurologist first.
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