Ethosuximide
| Evidence Level: L5 | Predicted Indications: 1 |
Table of Contents
Ethosuximide: Nephrogenic syndrome of inappropriate antidiuresis
One-Sentence Summary
Ethosuximide is an anti-seizure medicine originally used to treat absence epilepsy. The TxGNN model predicts it may be effective for nephrogenic syndrome of inappropriate antidiuresis (NSIAD), but this is a model prediction only, with 0 clinical trials and 0 publications supporting this specific indication.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not recorded in the local data |
| Predicted New Indication | Nephrogenic syndrome of inappropriate antidiuresis |
| TxGNN Prediction Score | 0.9991 |
| Evidence Level | L5 |
| Australia Market Status | Listed on the PBS Schedule (1 of 1 items) – TGA (ARTG) registration status is not included in this data |
| Number of PBS Items | 1 (valid: 1) |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Detailed mechanism of action data is not available in the data compiled for this report. Ethosuximide is generally understood to be a T-type calcium channel blocker that acts on thalamic neurons, and this underlies its efficacy in absence epilepsy.
NSIAD is caused by gain-of-function mutations in the vasopressin V2 receptor (AVPR2), which leads to water retention and low blood sodium. No known pathway connects T-type calcium channel blockade to this receptor or to renal water handling. The prediction therefore rests on the TxGNN model (deep learning) score alone and is not supported by a plausible mechanistic link.
Other top-ranked predictions show a similar pattern:
- Insomnia (97.8%): a weak rationale exists, as thalamic T-type channels are involved in sleep spindles. However, there is no clinical evidence, and ethosuximide is not an established hypnotic.
- Familial mesial temporal lobe epilepsy with febrile seizures (97.1%): biologically plausible as an epilepsy, but ethosuximide is generally not effective for focal or temporal lobe seizures.
- Childhood absence epilepsy susceptibility (95.7%): this matches the drug’s original indication, so it is not a true repurposing case.
Clinical Trial Evidence
Currently no related clinical trials registered for nephrogenic syndrome of inappropriate antidiuresis.
Literature Evidence
Currently no related literature available for nephrogenic syndrome of inappropriate antidiuresis.
For context, the literature retrieved for other predicted indications is limited. For childhood absence epilepsy, 17 papers were retrieved, made up of reviews and preclinical or animal-model studies. No randomised trials were among them. Examples include:
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 24530152 | 2014 | Review | Pediatric Neurology | Review of recent advances in childhood absence epilepsy |
| 19632158 | 2009 | Review | Epilepsy & Behavior | Review of absence seizures with new concepts |
| 17947380 | 2007 | Preclinical | PNAS | Mouse model of familial childhood absence epilepsy; spike-wave discharges were blocked by ethosuximide |
| 40339636 | 2025 | Preclinical | Progress in Neurobiology | Thalamocortical neuron control of absence seizures in GAERS rats, with ethosuximide-sensitive seizures |
This is a safety signal, not evidence of benefit.
Australia Market Information
| ARTG Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| ARTG 11703Y | ZARONTIN | Capsule 250 mg (oral) | Not stated in the data compiled for this report |
Safety Considerations
- Contraindications (from the knowledge graph, not label text): anxiety disorder, neurotic disorder, dysthymic disorder, kidney disease, pyoureter, haematologic disease, liver disease, gallbladder disease, systemic lupus erythematosus (including paediatric), neutropenia, agranulocytosis, acute intermittent porphyria.
- Drug Interactions: 92 interactions were identified, and the 20 listed in the data compiled for this report are all rated Moderate. Main ones include:
- CNS depressants and sedatives: morphine (including liposomal), opium, ethanol, promethazine, chlorpheniramine, dronabinol, nabilone
- Antimalarials: chloroquine, hydroxychloroquine, mefloquine
- Others: aprepitant, metoclopramide, sibutramine, cobicistat, deferasirox, fostamatinib, folic acid, leucovorin, levoleucovorin
Several knowledge-graph contraindications (kidney disease, haematologic disease, neutropenia, agranulocytosis) are relevant to any renal or haematological repurposing target. Please refer to the TGA-approved Product Information (PI) for label warnings and contraindications.
Conclusion and Next Steps
Decision: Hold
Rationale: The prediction is supported only by a model score. There are no registered trials or relevant literature, and no plausible mechanistic link between T-type calcium channel blockade and NSIAD, which is driven by AVPR2 gain-of-function. The knowledge-graph contraindications for kidney disease add further caution.
To proceed, the following is needed:
- Mechanism of action data confirmed from DrugBank
- Evidence of a biological pathway linking ethosuximide to vasopressin signalling or renal water handling
- Preclinical data in an NSIAD or AVPR2 model
- The TGA Product Information for ethosuximide warnings and contraindications
- Independent verification of the clinical evidence for the original absence epilepsy indication from primary sources, as the retrieved literature contains no randomised trials
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.