Ethosuximide

Trade Names:Zarontin- Capsules 250 mg- Syrup 250 mg/5 mL

Pharmacology

Elevates seizure threshold and suppresses paroxysmal spike and wave activity associated with lapses of consciousness common in absence (petit mal) seizures.

Pharmacokinetics

Absorption

T _max is 3 to 7 h.

Metabolism

Extensively metabolized to inactive metabolites.

Elimination

Approximately 20% is excreted unchanged by the kidneys. The t _1/2 is approximately 60 h (adults), 30 h (children).

Indications and Usage

Control of absence (petit mal) seizures.

Contraindications

Hypersensitivity to succinimides.

Dosage and Administration

PO 500 mg/day. Optimal dose for most children is 20 mg/kg/day. Maintenance therapy: Individualize dose. Increase daily dose slowly by 250 mg every 4 to 7 days until control is achieved with minimal adverse reactions. Administered doses exceeding 1.5 g/day in divided doses under strict medical supervision.

PO 250 mg/day.

General Advice

If GI upset occurs, give with food or milk.

Storage/Stability

Store capsules in tight containers and syrup in light-resistant containers at room temperature. Avoid freezing.

Drug Interactions

May increase serum hydantoin levels.

Lower primidone and phenobarbital levels may occur.

Laboratory Test Interactions

None well documented.

Adverse Reactions

CNS

Drowsiness; headache; dizziness; euphoria; hiccups; irritability; hyperactivity; lethargy; fatigue; ataxia; psychological disturbances such as sleep disorders; night terrors; poor concentration; aggressiveness.

Dermatologic

Urticaria; Stevens-Johnson syndrome; systemic lupus erythematosus; pruritic erythematous rash; hirsutism.

EENT

Myopia.

GI

Anorexia; GI upset; nausea; vomiting; cramps; epigastric and abdominal pain; weight loss; gum hypertrophy; tongue swelling.

Genitourinary

Vaginal bleeding; microscopic hematuria.

Hematologic

Leukopenia; agranulocytosis; pancytopenia; bone marrow suppression; eosinophilia.

Precautions

Pregnancy

Anticonvulsant drugs have been observed to increase the incidence of birth defects.

Renal Function

Use caution and perform periodic function tests.

Hepatic Function

Use caution and perform periodic function tests.

Hematologic effects

Blood dyscrasias, including fatal cases, have occurred. Periodic blood counts should be done.

Lupus

Cases of systemic lupus erythematosus have occurred.

Withdrawal

Do not withdraw drug abruptly as this may precipitate absence (petit mal) status; proceed slowly when increasing or decreasing dose.

Overdosage

Symptoms

Acute overdose: Confusion; sleepiness; unsteadiness; flaccid muscles; coma with slow, shallow respiration; nausea and vomiting. Chronic overdose: Skin rash; confusion; ataxia; dizziness; drowsiness; irritability; poor judgment; periorbital edema; proteinuria; hepatic function impairment; fatal bone marrow aplasia; hematuria; nephrosis.

Patient Information

• Instruct patient to take medication with food to minimize GI upset.
• Advise patient to carry medical identification (eg, card, bracelet), describing disease process and medication regimen, health care provider's name and telephone number.
• Emphasize importance of follow-up exams to monitor progress and adverse reactions.
• Explain that medication may change color of urine to pink, red, or red-brown, and assure that this is not harmful.
• Instruct patient to report these symptoms to health care provider: skin rash, sore throat, fever, unusual bleeding or bruising, swollen glands, pregnancy.
• Tell patient to avoid intake of alcoholic beverages or other CNS depressants.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness.

Copyright © 2009 Wolters Kluwer Health.