International reference: 1 US FDA recall for this ingredient
Lack of CGMP: This recall is being carried out due to potential for carry over of Senna Syrup. (ethosuximide)
US-market enforcement records (OpenFDA), shown for reference - not specific to this product in Malawi.
ZARONTIN 250MG SYRUP
ETHOSUXIMIDE
What it does
Ethosuximide is a medication used to control seizures, particularly absence seizures.
Commonly used for: absence seizures, petit mal seizures
Read more in plain English ↓Plain-language summary for general understanding - not medical advice. Always follow your pharmacist/doctor.
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Answers come only from this medicine's registration record, BNF monograph and interaction data - not medical advice.
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Sourcing - Kenya onlyRegistration & product details
Source: Pharmacy and Medicines Regulatory Authority · fetched 2026-04-21 17:37:44 · updated 2026-09-29 04:33:06
Drug Interactions
65Severe (7)
Antiepileptics - decreases absorption
Iron chelators (dexrazoxane) might decrease the absorption of antiepileptics (fosphenytoin, phenytoin). Avoid.
Antiepileptics - decreases exposure
Lumacaftor is predicted to decrease the exposure to antiepileptics (carbamazepine, fosphenytoin, phenobarbital, phenytoin, primidone). Avoid.
Antiepileptics - decreases concentration
St John’s wort is predicted to decrease the concentration of antiepileptics (fosphenytoin, phenobarbital, phenytoin, primidone). Avoid.
Antiepileptics - increases risk of overheating and dehydration
Hydroxyzine potentially increases the risk of overheating and dehydration when given with antiepileptics (zonisamide). Avoid in children.
Antiepileptics - increases risk of overheating and dehydration
Haloperidol potentially increases the risk of overheating and dehydration when given with antiepileptics (zonisamide). Avoid in children.
Antiepileptics - decreases absorption
Dexrazoxane might decrease the absorption of antiepileptics (fosphenytoin, phenytoin). Avoid.
Antiepileptics - increases risk of overheating and dehydration
Oxybutynin potentially increases the risk of overheating and dehydration when given with antiepileptics (zonisamide). Avoid in children.
Moderate (25)
Antiepileptics - increases concentration
Intravenous chloramphenicol increases the concentration of antiepileptics (fosphenytoin, phenytoin) and antiepileptics (fosphenytoin, phenytoin) affect the concentration of intravenous chloramphenicol
Antiepileptics - decreases concentration
Diazoxide decreases the concentration of antiepileptics (fosphenytoin, phenytoin) and antiepileptics (fosphenytoin, phenytoin) are predicted to decrease the effects of diazoxide. Monitor concentration
Antiepileptics - increases concentration
Disulfiramincreasestheconcentrationofantiepileptics (fosphenytoin,phenytoin).Monitorconcentrationandadjust dose.rStudy →AlsoseeTABLE12p.1520
Antiepileptics - increases concentration
Fluorouracilincreasestheconcentrationofantiepileptics (fosphenytoin,phenytoin).Monitorconcentrationandadjust dose.rAnecdotal 1xidneppA|snoitcaretnI A1 https://www.facebook.c (Books-Courses-Medic
Antiepileptics - decreases concentration
Folates are predicted to decrease the concentration of antiepileptics (fosphenytoin, phenobarbital, phenytoin, primidone). Monitor concentration and adjust dose.
Unknown (33)
Antiepileptics - increases risk of overheating and dehydration
Acetazolamide potentially increases the risk of overheating and dehydration when given with antiepileptics (zonisamide). Avoid in children.
Antiepileptics - increases risk of visual disturbances
Alcohol potentially increases the risk of visual disturbances when given with antiepileptics (retigabine).
Antiepileptics - decreases exposure
Enzalutamide is predicted to slightly decrease the exposure to antiepileptics (brivaracetam).
Antiepileptics - decreases exposure
Apalutamidepotentiallydecreasestheexposureto antiepileptics(valproate).nTheoretical
Antiepileptics - increases concentration
Capecitabine increases the concentration of antiepileptics (fosphenytoin, phenytoin).
Data from BNF 85 (British National Formulary). This is not a substitute for professional medical advice. Matched via: class
About this medicine
Ethosuximide is a medication used to control seizures, particularly absence seizures.
What it treats
- absence seizures
- petit mal seizures
How it works
It helps to stabilize electrical activity in the brain to prevent seizures.
Who it's for
This medication is for people who experience absence seizures.
Drug class
Antiepileptics
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: Ethosuximide
BNF-referencedEthosuximide is an antiepileptic medication primarily used to treat absence seizures, also referred to as petit mal seizures. It is particularly effective in patients who experience frequent episodes of these seizures. The drug functions by modulating calcium ion influx in excitable cells, which plays a critical role in neuronal excitability and neurotransmitter release. Ethosuximide is often selected for its favorable side effect profile compared to other seizure medications.
Indications
- Absence seizures
- Atypical absence seizures (adjunct)
- Myoclonic seizures
Dosage
Children: For children aged 1 month to 5 years, the initial dose is 5 mg/kg twice daily (maximum per dose 125 mg), with the dose
Adults: Initially 500 mg daily in 2 divided doses, increased in steps of 250 mg every 5–7 days; usual dose 1–1.5 g daily in 2 divided doses, increased if necessary up to 2 g daily.
Mechanism of action
Ethosuximide binds to T-type voltage-sensitive calcium channels, inhibiting calcium ion entry. This action is crucial for reducing the paroxysmal three-cycle-per-second spike-and-wave activity characteristic of absence seizures. By blocking T-type calcium currents, ethosuximide raises the seizure threshold and decreases the frequency of seizures. The drug may also alter neurotransmission and directly modify membrane function in excitable cells.
Pharmacodynamics
Ethosuximide effectively suppresses the spike-and-wave discharges seen in absence seizures, thereby reducing the frequency of epileptiform attacks. This suppression occurs through a combination of decreased motor cortex excitability and an increased threshold for convulsive stimuli within the central nervous system. Its specific action on T-type calcium channels is pivotal in managing absence seizures.
Pharmacokinetics
Ethosuximide is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately 3 to 7 hours after oral administration. It has a half-life of about 30 hours, allowing for once or twice daily dosing. Ethosuximide is primarily metabolized by the liver, with a significant portion of the drug being excreted unchanged in the urine. Renal function may affect its clearance, and careful monitoring is advised in patients with impaired kidney function.
Contra-indications
- Hypersensitivity to ethosuximide or any of its components
- Severe hepatic impairment
Adverse effects
- Angioedema
- Leucopenia
- Psychotic disorders
- Abnormal speech sensation
- Tinnitus
- Toothache
- Weight decreased
- Pancreatitis
- Severe cutaneous adverse reactions (SCARs)
- Thrombocytopenia
- Suicidal behaviours
Interactions
- May interact with other antiepileptic drugs
- Potentially increases the risk of suicidal thoughts and behaviours when combined with other medications
Precautions
- Caution in patients with a history of psychiatric disorders
- Monitor for signs of suicidal thoughts or behaviours
- Screen for HLA-B*1502 allele in individuals of specific Asian descent due to potential hypersensitivity reactions
Pregnancy
Caution is advised due to reproductive toxicity observed in animal studies. The risks and benefits should be carefully weighed.
Breast-feeding
Manufacturer advises avoiding use, as ethosuximide is present in breast milk in animal studies.
Storage
Store in a cool, dry place away from direct sunlight. Keep out of reach of children.
Formulations
- Ethosuximide 250 mg capsules
- Ethosuximide oral solution 250 mg/5 mL
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.
Molecular reference: Ethosuximide
PubChem CID 3291Molecular formula: C7H11NO2
Mechanism of action
Binds to T-type voltage sensitive calcium channels. Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. The isoform alpha-1G gives rise to T-type calcium currents. T-type calcium channels belong to the "low-voltage activated (LVA)" group and are strongly blocked by mibefradil. A particularity of this type of channels is an opening at quite negative potentials and a voltage-dependent inactivation. T-type channels serve pacemaking functions in both central neurons and cardiac nodal cells and support calcium signaling in secretory cells and vascular smooth muscle. They may also be involved in the modulation of firing patterns of neurons which is important for information processing as well as in cell growth processes. Succinimide anticonvulsants are thought to increase the seizure threshold and suppress the paroxysmal three-cycle-per-second spike-and-wave pattern seen with absence (petit mal) seizures. The frequency of attacks is reduced by depression of nerve transmission in the motor cortex. These effects may be due to direct modification of membrane function in excitable cells and/or alteration of chemically mediated neurotransmission. The specific effect of ethosuximide against absence seizures appears to be due to its ability to block T-type calcium channels at concentrations that do not affect other ion channels. /Succinimide Anticonvulsants/ Ethosuximide reduces low threshold Ca(2+) currents (T currents) in thalamic neurons. The thalamus plays an important role in generation of 3 Hz spike-wave rhythms typical of absence seizures. Neurons in the thalamus exhibit a large amplitude T current spike that underlies bursts of action potentials and likely plays an important role in thalamic oscillatory activity such as 3 Hz spike-wave activity. At clinically relevant concentrations, ethosuximide inhibits the T current, as evident in voltage-clamp recordings in acutely isolated, ventrobasal thalamic neurons from rats and guinea pigs. Ethosuximide reduces this current without modifying the voltage dependence of steady-state inactivation or the time course of recovery from inactivation. By contrast, succinimide derivatives with convulsant properties do not inhibit this current. Ethosuximide does not inhibit sustained repetitive firing or enhance GABA responses at clinically relevant concentrations. Current data are consistent with the idea that inhibition of T currents is the mechanism by which ethosuximide inhibits absence seizures. Ethosuximide is an alternative medicament that is used for coupling of petit mal, especially in childhood. Some clinical observations show that it has secondary effects on the gastro intestinal tract (GIT). The present research tries to define the characteristics of Ethosuximide--the inducted secondary effects on the GIT, and to explain some of the possible mechanisms that cause them. The changes that occur in the GIT of patients cured with Ethosuximide are registered roentgenologically. The main change is the atony of the stomach and intestines and the reduced peristaltic activity. The influence of Ethosuximide is examined on smooth muscular samples of human stomach, taken in vitro using stomach resection. The medicament authoritatively reduce the spontaneous bioelectrical activity of the smooth muscular tissue, influences mainly it's components that have Ca+ nature. Together with that is indicated relaxation of the smooth muscular samples. In that research is expressed the thesis that this Ethosuximide reduction of the Ca(+)-influx in the smooth muscular cells and the related relaxation probably are one of the main reasons of the secondary effects on the GIT. Ethosuximide is one of the means of treatment of minor epilepsy but hardly any data on its mechanism of acti
Pharmacodynamics
Used in the treatment of epilepsy. Ethosuximide suppresses the paroxysmal three cycle per second spike and wave activity associated with lapses of consciousness which is common in absence (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.
Source: PubChem (NCBI) · pathways from PathBank, Reactome, WikiPathways & PharmGKB.
This drug in other countries
The same active ingredient registered across other registries we cover - including different brands.