ZARONTIN

What it is

ZARONTIN contains the active component ethosuximide. ZARONTIN capsules contain 250 mg ethosuximide. ZARONTIN syrup contains ethosuximide 250 mg/5mL. ZARONTIN capsules are clear oval soft gelatin capsules. ZARONTIN syrup is a clear slightly yellowish to slightly pinkish liquid.

Approved indications

— Control of petit mal epilepsy.

Dosing overview

The 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). 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.

Key safety warnings

Ethosuximide, when used alone in mixed types of epilepsy, may increase the frequency of grand mal seizures in some patients. Abrupt withdrawal of anticonvulsant medication may precipitate petit mal status. 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. Cases of systemic lupus erythematosus have been reported with the use of ethosuximide. Serious dermatologic reactions, including Stevens–Johnson syndrome (SJS), have been reported with ethosuximide treatment. SJS can be fatal. The onset of symptoms is usually within 28 days, but can occur later. Drug reaction with eosinophilia and systemic symptoms (DRESS) has been reported with ethosuximide exposure. DRESS consists of a combination of three or more of the following: cutaneous reaction (such as rash or exfoliative dermatitis), eosinophilia, fever, lymphadenopathy; and one or more systemic complications such as hepatitis, nephritis, pneumonitis, myocarditis, and pericarditis. DRESS is sometimes fatal. Antiepileptic drugs (AEDs), including ethosuximide, increase the risk of suicidal thoughts or behaviour in patients taking these drugs for any indication. Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behaviour, and/or any unusual changes in mood or behaviour. 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.

Contraindications

Ethosuximide is contraindicated in patients with hypersensitivity to succinimides, ethosuximide or any components of this medication.

PBS listing

The oral solution 250 mg per 5 mL (200 mL) is listed on the PBS with 2 items under restricted restriction, with an ex-manufacturer price of A$56.35. The capsule 250 mg is listed on the PBS with 1 item under restricted restriction, with an ex-manufacturer price of A$127.49.

Regulatory history

ZARONTIN syrup was first approved on 27 June 2002. ZARONTIN capsules were first approved on 29 April 2003. ARTG registration records show ZARONTIN syrup (ARTG 79031) was first listed 2002-06-27 and ZARONTIN capsules (ARTG 461005) were first listed 2025-01-02.