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ethosuximide 250 mg capsule generic zarontin

Out of Stock Manufacturer HERITAGE PHARMA 23155053201
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Ethosuximide, alone or in conjunction with other anticonvulsants (e.g., valproic acid), is generally considered as first-line therapy in the prophylactic management of absence (petit mal) seizures. The drug is usually ineffective in the management of partial seizures with complex symptomatology (psychomotor seizures) or tonic-clonic (grand mal) seizures, although some clinicians have reported good results with ethosuximide in controlling partial seizures with complex symptomatology and myoclonic seizures. When used alone in mixed seizures, ethosuximide may increase the frequency of tonic-clonic seizures and when patients with absence seizures also have tonic-clonic seizures, other anticonvulsants such as phenytoin, phenobarbital, or valproate should be used in combination with ethosuximide.

Dosage and Administration

Ethosuximide is administered orally as a capsule or oral solution.

Patients who are currently receiving or beginning therapy with ethosuximide and/or any other anticonvulsant should be closely monitored for notable changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression.

Dosage must be carefully and slowly adjusted according to individual requirements and response. Ethosuximide should be withdrawn or dosage reduced slowly to avoid precipitating seizures or absence status.

The usual initial dosage of ethosuximide for patients 3-6 years of age is 250 mg daily in a single dose; for patients 6 years of age or older, 500 mg may be given daily in a single dose or in divided doses. One method of establishing the maintenance dosage is to increase the daily dosage by 250 mg every 4-7 days until seizure control is achieved with minimal adverse effects. The usual maintenance dosage is 20 mg/kg or 1.2 g/m daily. Dosage should not usually exceed 1.5 g daily, given in divided doses. When the dosage exceeds 1.5 g daily, the patient must be closely supervised by the clinician. Some studies indicate that when the patient is well stabilized, the total daily dosage may be given as one dose; however, clinical efficacy of this once-daily regimen has not been established.

Patients undergoing hemodialysis may require a supplemental dose of ethosuximide following each dialysis session or may require dosage adjustment.(See Cautions: Precautions and Contraindications and also see Pharmacokinetics: Elimination.)


Adverse Effects

The most common adverse effects of ethosuximide are GI symptoms including anorexia and weight loss, vague gastric upset, cramps, abdominal pain, diarrhea, nausea, vomiting, and epigastric distress.

Adverse nervous system effects including drowsiness, headache, fatigue, dizziness, ataxia, irritability, euphoria, hyperactivity, lethargy, and hiccups may occur. Adverse psychiatric or psychologic effects have also occurred, particularly in patients who had previously manifested psychologic abnormalities, and have included sleep disturbances, night terrors, aggressiveness, and inability to concentrate. Rarely, paranoid psychosis, increased libido, and increased state of mental depression with overt suicidal intentions have been reported. (See Dosage and Administration and also see Cautions: Precautions and Contraindications.)

The use of ethosuximide has also been associated with blood dyscrasias including leukopenia, eosinophilia, agranulocytosis, pancytopenia (with or without bone marrow depression), and aplastic anemia which have sometimes resulted in fatalities. Ethosuximide has also been implicated in the production of positive direct Coombs' test results and systemic lupus erythematosus. Rarely, administration of the drug has been associated with Stevens-Johnson syndrome. Urticaria and pruritic erythematous rashes have also occurred. Other adverse reactions reported following ethosuximide therapy include myopia, vaginal bleeding, microscopic hematuria, gum hypertrophy, hirsutism, and swelling of the tongue.

Precautions and Contraindications

Ethosuximide shares the toxic potentials of the succinimide-derivative anticonvulsants, and the usual precautions of anticonvulsant administration should be observed.

Clinicians should inform patients, their families, and caregivers about the potential for an increased risk of suicidal thinking and behavior (suicidality) associated with anticonvulsant therapy. For a complete discussion, and

Patients should be warned that ethosuximide may impair their ability to perform activities requiring mental alertness or physical coordination (e.g., operating machinery, driving a motor vehicle).

Ethosuximide should be used with extreme caution in patients with hepatic impairment, abnormal liver function test values, and/or renal impairment.(See Dosage and Administration.) Complete blood cell counts, liver function tests, and urinalyses should be performed periodically in patients receiving the drug.

Ethosuximide is contraindicated in patients with known hypersensitivity to ethosuximide or other succinimides (e.g., methsuximide, phensuximide [no longer commercially available in the US]).

Pregnancy and Lactation


Safe use of ethosuximide during pregnancy has not been established.


Ethosuximide distributes into human milk. The drug should be used with caution in nursing women, and women should be advised to notify their clinician if they plan to breast-feed.



Ethosuximide is readily absorbed from the GI tract. Following oral administration of a single dose, peak blood concentrations are reached within 4 hours; however, about 4-7 days of therapy at the usual dosage are required to achieve steady-state plasma concentrations. The plasma concentration required for therapeutic effect is generally considered to range from 40-100 mcg/mL; plasma concentrations less than 40 mcg/mL are rarely effective. The relationship between plasma ethosuximide concentrations and toxic effects of the drug has not been clearly established; however, plasma concentrations as high as 150 mcg/mL have not been associated with signs of toxicity.


In vitro data suggest that there is no substantial degree of protein binding for ethosuximide. In one study in children, peak CSF concentrations of 25-50 mcg/mL were achieved within 1-2 hours following a single 250-mg dose of ethosuximide. These concentrations were maintained for 12-24 hours, and the drug was still detectable in the CSF 65 hours after the drug was given.

Ethosuximide crosses the placenta. The drug also is distributed into milk.


The plasma half-life of ethosuximide is about 60 hours in adults and about 30 hours in children.

Ethosuximide is excreted slowly in urine. Approximately 20% of a dose is excreted unchanged and up to 50% may be excreted in urine as the hydroxylated metabolite and/or its glucuronide. Small amounts of unchanged drug are also excreted in bile and feces.

Ethosuximide is removed by hemodialysis.(See Dosage and Administration and see Cautions: Precautions and Contraindications.)

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