Uses

Actions

Ethosuximide suppresses the paroxysmal spike and wave pattern which is common in petit mal seizures. The frequency of epileptiform attacks is reduced, apparently by depression of the motor cortex and elevation of the threshold of the central nervous system to convulsive stimuli.

Indications

Zarontin is indicated for the control of petit mal epilepsy.

Contraindications

Ethosuximide should not be used in patients with a history of hypersensitivity to succinimides or components of these products.

Precautions

Blood dyscrasias, including some with fatal outcome, have been reported to be associated with the use of ethosuximide, therefore, periodic blood counts should be performed. Should signs and/or symptoms of infection (e.g., sore throat, fever) develop, blood count determinations should be considered at that point.

Ethosuximide is capable of producing morphological and functional changes in the animal liver. In humans, abnormal liver and renal function studies have been reported. Ethosuximide should be administered with extreme caution to patients with known liver of renal disease. Periodic urinalysis and liver function studies are advised for all patients receiving the drug.

Cases of systemic lupus erythematosus have been reported with the use of ethosuximide. The physician should be alert to this possibility.

Hazardous Activities

Ethosuximide may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks, such as driving a motor vehicle or other such activity requiring alertness; therefore, the patient should be cautioned accordingly.

Patients taking ethosuximide should be advised of the importance of adhering strictly to the prescribed dosage regimen. Patients should be instructed to promptly contact their physician if they develop signs and/or symptoms (e.g., sore throat, fever) suggesting an infection.

Ethosuximide, when used alone in mixed types of epilepsy, may increase the frequency of grand mal seizures in some patients. As with other anticonvulsants, it is important to proceed slowly when increasing or decreasing dosage, as well as when adding or eliminating other medication. Abrupt withdrawal of anticonvulsant medication may precipitate petit mal status.

Use in Pregnancy - Category D

The risk of a mother with epilepsy giving birth to a baby with an abnormality is about three times that of the general population. Some of this risk is due to the anticonvulsant drugs taken. Mothers taking more than one anticonvulsant drug might have a higher risk of having a baby with a malformation than mothers taking one drug.

Overall, the risk of having an abnormal child as a result of medication is far outweighed by the dangers to the mother and foetus of uncontrolled epilepsy. It is not known whether women taking ethosuximide have a different risk.

Interactions With Other Drugs

Since 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 levels).

Adverse Reactions

Gastrointestinal System

Gastrointestinal symptoms occur frequently and include anorexia, vague gastric upset, nausea and vomiting, cramps, epigastric and abdominal pain, weight loss, and diarrhoea. There have been reports of gum hypertrophy and swelling of the tongue.

Haemopoietic System

Haemopoietic complications associated with the administration of ethosuximide have included leucopoenia, agranlocytosis, pancytopenia, with or without bone marrow suppression, aplastic anaemia and eosinophilia.

Nervous System

Neurological and sensory reactions reported during therapy with ethosuximide have included drowsiness, headache, dizziness, euphoria, hiccoughs, irritability, hyperactivity, lethargy, fatigue and ataxia. Psychiatric or psychological aberrations associated with ethosuximide administration have included disturbance of sleep, night terrors, inability to concentrate and aggressiveness. These effects may be noted particularly in patients who have previously exhibited psychological abnormalities. There have been rare reports of paranoid psychosis, increased libido and increased state of depression with overt suicidal intentions.

Integumentary System

Dermatological manifestations which have occurred with the administration of ethosuximide have included urticaria, Stevens-Johnson syndrome, systemic lupus erythematosus and pruritic erythematous rashes

Miscellaneous

Other reactions have included myopia, vaginal bleeding, swelling of the tongue, gum hypertrophy and hirsutism.

Overdosage

Treatment

Gastric lavage and support respiration if necessary.

Dosage and Administration

Zarontin is administered orally.

Recommended initial daily dose for children and adults is approximately 20-30 mg/kg administered in two divided doses. This regimen will frequently achieve plasma levels in the therapeutic range of 40-100 mg/L. (Optimum 75 mg/L). As the dose serum level relationship may be curvilinear in individual patients dosage should be increased by small increments.

One useful method is to increase the daily dose by 250 mg every four to seven days until control is achieved with minimal side effects. Dosages exceeding 1.5 g daily, in divided doses should be administered only under the strictest supervision of the physician. Plasma level monitoring is recommended. Zarontin may be administered in combination with other anticonvulsants when other forms of epilepsy coexist with petit mal.

Presentation

Syrup, 250 mg/5mL (raspberry). Syrup contains sodium benzoate 5 mg/mL as preservative. Contains sucrose 60% w/v, glycerol 12.5% w/v).

Capsules, 250 mg (clear, brown orange).

Medicine Classification

Prescription Medicine.

Package Quantities

Capsules, 250 mg (clear, brown orange): 200s.

Syrup, 250 mg/5 mL (raspberry): 250 mL.