ethosuximide

Absorption: Rapidly and completely absorbed from the GI tract following oral administration.

Distribution: Freely distributed throughout body water.

Metabolism/Excretion: Mostly metabolized by the liver. 10% excreted unchanged by the kidneys.

Half-Life: 50–60 hr (adults); 30 hr (children).

Time/Action Profile ⬆ ⬇

(anticonvulsant activity)

ROUTE	ONSET	PEAK	DURATION
PO	hr–days	days	days

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
History of ethosuximide-induced immune thrombocytopenia;

Use Cautiously in:

All patients (may ↑ risk of suicidal thoughts/behaviors);
Hepatic or renal disease;
Mixed seizure disorders (may ↑ risk of grand mal seizures);
Bone marrow suppression;
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant.
Pedi: Children 3 yr (safety and effectiveness not established).

Adv. Reactions/Side Effects ⬆ ⬇

Derm: STEVENS-JOHNSON SYNDROME, DRUG REACTION WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS (DRESS), hirsutism, rash, urticaria

EENT: myopia

GI: abdominal pain, anorexia, cramping, diarrhea, hiccups, nausea, vomiting, weight loss

GU: pink/brown discoloration of urine, vaginal bleeding

Hemat: agranulocytosis, eosinophilia, immune thrombocytopenia, leukopenia, pancytopenia

Neuro: ↑FREQUENCY OF TONIC-CLONIC (GRAND MAL) SEIZURES, SUICIDAL THOUGHTS, ataxia, dizziness, drowsiness, euphoria, fatigue, headache, hyperactivity, irritability, psychiatric disturbances

Misc: ALLERGIC REACTION, systemic lupus erythematosus

Interactions ⬆ ⬇

Drug-drug:

Seizure threshold may be lowered by phenothiazines, antidepressants, or MAO inhibitors.
Additive CNS depression with other CNS depressants, including alcohol, antihistamines, antidepressants, opioid analgesics, and sedative/hypnotics.
May ↑ phenytoin levels.
May ↓ phenobarbital or primidone levels.
Blood levels may be ↑ or ↓ by valproic acid.

Drug-Natural Products:

See sedative interactions.
St. John's wort may affect ethosuximide levels and effectiveness; avoid use.
Concomitant use of kava, valerian, skullcap, chamomile, or hops can ↑ CNS depression.

Route/Dosage ⬆ ⬇

PO (Adults and Children >6 yr): 250 mg bid initially; may ↑ by 250 mg/day every 4–7 days until control achieved (usual maintenance dose 20–40 mg/kg/day in 2 divided doses).
PO (Children 3–6 yr): 250 mg once daily initially; may ↑ by 250 mg/day every 4–7 days until control achieved (optimal dose for most children is 20 mg/kg/day in 2 divided doses).

Availability ⬆ ⬇

(Generic available)

Capsules: 250 mg
Oral solutionraspberry flavor: 250 mg/5 mL

Assessment ⬆ ⬇

Assess location, duration, frequency, and characteristics of seizure activity.
Assess patient’s mood, behavioral patterns, and facial expressions. Patients with a history of psychiatric disorders have an increased risk of developing behavioral changes. These symptoms may necessitate withdrawal of the medication.
Monitor closely for changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression.
Assess for rash periodically during therapy. May cause Stevens-Johnson syndrome. Discontinue therapy if severe or if accompanied with fever, general malaise, fatigue, muscle or joint aches, blisters, oral lesions, conjunctivitis, hepatitis and/or eosinophilia.
Monitor for signs and symptoms of DRESS (fever, rash, lymphadenopathy, and/or facial swelling, associated with involvement of other organ systems (hepatitis, nephritis, hematologic abnormalities, myocarditis, myositis) during therapy. May resemble an acute viral infection. Eosinophilia is often present. Discontinue therapy if signs occur.

Lab Test Considerations:

Monitor CBC, hepatic function tests, and urinalysis routinely during prolonged therapy.

Toxicity and Overdose:

Therapeutic serum ethosuximide levels range from 40–100 mcg/mL.

Implementation ⬆ ⬇

PO: Measure liquid preparations with calibrated measuring device.
- Administer with food or milk to minimize GI irritation.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed. If a dose is missed, take as soon as remembered within 4 hr, then continue on dose schedule. Do not double doses. Do not discontinue medication without advice of health care professional. Sudden withdrawal may precipitate seizures. Instruct patient to read the Medication Guide before starting and with each Rx refill, changes may occur.
Medication may cause dizziness, drowsiness, or blurred vision. Caution patient to avoid driving or other activities requiring alertness until response to medication is known. Do not resume driving until physician gives clearance based on control of seizure disorder.
Advise patient to avoid alcohol while taking this medication.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
Instruct patient to notify health care professional if skin rash, joint pain, sore throat, fever, unusual bleeding or bruising, swollen glands, or pink/brown urine, or signs and symptoms of DRESS occur. Advise patient and family to notify health care professional if thoughts about suicide or dying, attempts to commit suicide; new or worse depression; new or worse anxiety; feeling very agitated or restless; panic attacks; trouble sleeping; new or worse irritability; acting aggressive; being angry or violent; acting on dangerous impulses; an extreme increase in activity and talking, other unusual changes in behavior or mood occur.
Rep: Instruct patient to notify health care professional if pregnancy is planned or suspected. Encourage patient to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry if they become pregnant. This registry is collecting information about the safety of antiepileptic drugs during pregnancy. To enroll, patients can call the toll free number 1-888-233-2334.
Advise patient to carry identification describing disease process and medication regimen at all times.
Emphasize the importance of follow-up exams to monitor progress and side effects.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇