Adult: Initially, 500 mg daily, may increase in increments of 250 mg every 4-7 days until seizure control is achieved. Usual dose: 1,000-1,500 mg daily in 2 divided doses; increased if necessary up to 2,000 mg daily. Treatment recommendations may vary among countries and individual products (refer to specific product guidelines). Child: Up to 6 years Initially, 250 mg daily, may increase gradually in small increments every few days until seizure control is achieved. Optimal dose: 20 mg/kg daily. Max: 1,000 mg daily; >6 years Same as adult dose. Treatment recommendations may vary among countries and individual products (refer to specific product guidelines).
Administration
May be taken with or without food.
Contraindications
Porphyria.
Special Precautions
Patient with history of psychiatric disorder. Avoid abrupt withdrawal. Avoid use in patients with history of ethosuximide-induced immune thrombocytopenia. Renal and hepatic impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: Suicidal ideation and behaviour; increased frequency of generalised tonic-clonic (grand mal) seizures (when used alone in mixed types of epilepsy); changes in liver and renal functions; SLE, dyskinesia, drug-induced immune thrombocytopenia. Eye disorders: Myopia. Gastrointestinal disorders: Nausea, vomiting, epigastric pain, abdominal pain, discomfort, and cramps, vague gastric upset, diarrhoea, swollen tongue, gingival hypertrophy. General disorders and administration site conditions: Fatigue, irritability. Investigations: Weight loss. Metabolism and nutrition disorders: Decreased appetite. Nervous system disorders: Headache, dizziness, somnolence, ataxia, lethargy, psychomotor hyperactivity, disturbance in attention. Psychiatric disorders: Aggression, sleep disturbance, night terrors, depression, psychotic disorder, euphoria. Renal and urinary disorders: Microscopic haematuria. Reproductive system and breast disorders: Vaginal haemorrhage. Respiratory, thoracic and mediastinal disorders: Hiccups. Skin and subcutaneous tissue disorders: Rash erythematous, urticaria, hirsutism. Potentially Fatal: Drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), blood dyscrasias (e.g. leucopenia, pancytopenia with or without bone marrow depression, eosinophilia, agranulocytosis, aplastic anaemia).
PO: Z (Insufficient data to conclude its safety and risk during pregnancy. Use only when benefits outweigh risks. If used, monitor drug levels and adjust dose accordingly.)
Patient Counseling Information
This drug may cause CNS depression, which may impair physical or mental abilities, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor CBC (monthly for a year and every 6 months thereafter); LFTs and urinalysis (periodically); serum concentrations. Monitor for signs of suicidality (e.g. suicidal thoughts, behavioural changes, depression) and skin reactions. In patients with suspected drug-induced immune thrombocytopenia, monitor serial platelet counts and, if possible, assess the presence of drug-dependent antiplatelet antibodies.
Overdosage
Symptoms: Nausea, vomiting, CNS depression including coma with respiratory depression. Management: Symptomatic and supportive treatment. May induce emesis (unless patient is or may rapidly become comatose, obtunded, or convulsing), perform gastric lavage, or administer activated charcoal and cathartics. Monitor CV and respiratory functions. May consider haemodialysis.
Drug Interactions
May decrease plasma concentration with carbamazepine, phenobarbital, primidone, and lamotrigine. May increase plasma concentration with isoniazid and valproic acid. May increase the plasma concentration of phenytoin.
Action
Description: Mechanism of Action: Ethosuximide, a succinimide derivative, is suspected to reduce the frequency of seizures by depressing nerve transmission in the motor cortex and increasing the seizure threshold. It suppresses the paroxysmal spike-and-wave pattern common in absence (petit mal) seizures. Pharmacokinetics: Absorption: Completely and readily absorbed from the gastrointestinal tract. Time to peak plasma concentration: 1-7 hours. Distribution: Widely distributed throughout the body. Crosses the placenta and enters breast milk. Volume of distribution: 0.7 L/kg. Metabolism: Extensively metabolised in the liver via oxidation to inactive metabolites. Excretion: Via urine (mainly as metabolites; 10-20% as unchanged drug). Elimination half-life: 40-60 hours.
Chemical Structure
Ethosuximide Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 3291, Ethosuximide. https://pubchem.ncbi.nlm.nih.gov/compound/Ethosuximide. Accessed Sept. 26, 2022.
Storage
Cap: Store between 15-30°C. Oral solution or syrup: Store between 20-25°C. Do not freeze. Protect from light.
N03AD01 - ethosuximide ; Belongs to the class of succinimide derivatives antiepileptics.
References
Anon. Ethosuximide. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 01/08/2022.Anon. Ethosuximide. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 01/08/2022.Buckingham R (ed). Ethosuximide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/08/2022.Clinect NZ Pty Limited. Zarontin 250 mg Capsules; Zarontin Syrup 250 mg/5 mL data sheet 1 February 2022. Medsafe. http://www.medsafe.govt.nz. Accessed 01/08/2022.Emeside 250 mg/5 mL Syrup; Ethosuximide Essential Generics 250 mg/5 mL Syrup. MHRA. https://products.mhra.gov.uk. Accessed 13/09/2022.Emeside Capsules (Chemidex Pharma Ltd.). MHRA. https://products.mhra.gov.uk. Accessed 01/08/2022.Ethosuximide Capsule (Akorn). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 01/08/2022.Ethosuximide Roma 250 mg/5 mL Oral Solution (Roma Pharmaceuticals Ltd). MHRA. https://products.mhra.gov.uk. Accessed 01/08/2022.Joint Formulary Committee. Ethosuximide. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/08/2022.Zarontin Solution (Parke-Davis Div of Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 01/08/2022.
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