Topiramate
| Evidence Level: L5 | Predicted Indications: 1 |
Table of Contents
Topiramate: Trigeminal nerve neoplasm
One-Sentence Summary
Topiramate is an antiseizure medication originally used for generalised tonic-clonic seizures, partial epilepsy and Lennox-Gastaut syndrome. The top-ranked prediction of the TxGNN model (deep learning) is trigeminal nerve neoplasm (score 0.9970). This score comes from the TxGNN model (deep learning) and may reflect similarities the model learned between related diseases, not biological evidence. That prediction is currently supported by 0 registered clinical trials and 20 publications, including a small randomised crossover pilot study and a meta-analysis.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not recorded in the local data |
| Predicted New Indication | Trigeminal nerve neoplasm |
| TxGNN Prediction Score | 0.9970 |
| Evidence Level | L5 (trigeminal neuralgia) |
| 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 | Proceed with Guardrails (trigeminal neuralgia) |
Note on the ranking: The highest-scoring prediction, trigeminal nerve neoplasm, has no trials or literature and no plausible antineoplastic mechanism, so it is rated L5 and Hold. Most other top predictions are rare reflex epilepsies (visual, startle, orgasm-induced, eating, audiogenic, thinking, micturition-induced and reading seizures), which fall within topiramate’s existing antiseizure spectrum. Their evidence is indirect (L4/L5), so none is recommended for progression beyond a research question or Hold.
Why is This Prediction Reasonable?
Detailed mechanism of action data is not available in the data compiled for this report. From published pharmacology, topiramate is a broad-spectrum antiseizure drug that blocks voltage-gated sodium channels, enhances GABA-A activity, antagonises AMPA/kainate glutamate receptors and weakly inhibits carbonic anhydrase.
Carbamazepine, a sodium channel blocker, is first-line therapy. Topiramate’s sodium channel blockade and dampening of excitatory transmission parallel carbamazepine’s action. The TxGNN model (deep learning) score for this drug may reflect similarities the model learned between related diseases, not biological evidence.
Clinical Trial Evidence
No ANZCTR identifiers were available either.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 11307048 | 2001 | RCT (pilot, placebo-controlled crossover) | Clin Neuropharmacol | Three patients; topiramate reduced pain by 31%, 42% and 64% (p = 0.04) |
| 21936587 | 2011 | Meta-analysis | CNS Drugs | Topiramate compared with carbamazepine in classical trigeminal neuralgia |
| 19471799 | 2004 | Systematic review/Meta-analysis | Rev Bras Anestesiol | Efficacy, safety and tolerability of pharmacological treatments for trigeminal neuralgia |
| 41718164 | 2026 | Systematic review | Medicines (Basel) | Anticonvulsants in trigeminal neuralgia, stratified by mechanism of action |
| 25864062 | 2015 | Review | Neurosciences (Riyadh) | Update on pharmacological and surgical options for trigeminal neuralgia |
| 17952282 | 2007 | Case series | Arq Neuropsiquiatr | Eight patients on 50-100 mg/day: 3 complete remissions, 3 moderate improvements, 2 non-responders; dizziness, somnolence and weight loss were common |
| 11398791 | 2001 | Clinical report | J Pain Symptom Manage | Topiramate relieved idiopathic and symptomatic trigeminal neuralgia |
| 11903537 | 2001 | Review | Headache | Antiepileptic drugs in cluster headache and trigeminal neuralgia |
| 29114270 | 2017 | Review | Asian J Neurosurg | General review of trigeminal neuralgia |
| 19445753 | 2009 | Review | BMJ Clin Evid | General review of trigeminal neuralgia |
The RCT is very small (three patients), so it provides only preliminary support.
Australia Market Information
| ARTG Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| ARTG 13878K | Topamax Sprinkle | Capsule 50 mg (oral) | Not stated in the data compiled for this report |
Safety Considerations
- Contraindications (from knowledge graph drug-disease edges, not label text): anxiety disorder, neurotic disorder, dysthymic disorder, kidney disease, pyoureter, liver disease, gallbladder disease, diarrhoeal disease, ocular hypertension, nephrolithiasis (including SLC26A1-related susceptibility), acute urate nephropathy, acidosis disorder, metabolic acidosis, amnestic disorder, retrograde amnesia.
- Drug interactions: The interaction screen returned 100 interactions. The main ones listed are:
- Major: metformin, and the anticholinergic agents hyoscyamine, atropine, scopolamine, glycopyrronium, clidinium, dicyclomine, mepenzolate, methscopolamine, propantheline and trospium.
- Moderate: pioglitazone, glyburide, morphine, dronabinol, nabilone, phentermine, metoclopramide, phenylbutyric acid and glycerol phenylbutyrate.
- Reported adverse effects in the literature: dizziness, somnolence, weight loss, cognitive impairment, metabolic acidosis, renal stones, and psychiatric effects (case reports of psychotic exacerbation and mania).
Please refer to the TGA-approved Product Information (PI) for official warnings and contraindications.
Conclusion and Next Steps
Rationale:
- This supports topiramate as an alternative or add-on for patients who are intolerant of, or refractory to, carbamazepine or oxcarbazepine. The evidence base is small and no registered Phase 3 trial exists.
- Trigeminal nerve neoplasm should be placed on Hold. It is likely a model artefact with no supporting evidence.
- The reflex epilepsy predictions are Hold or Research Question only. Their evidence is general epilepsy or preclinical data, with nothing specific to the conditions.
To proceed, the following is needed:
- Review of the TGA-approved PI for warnings and contraindications, which was not available in the data compiled for this report
- Detailed mechanism of action data from DrugBank
- Monitoring plan for cognitive and other CNS adverse effects, metabolic acidosis, renal stones, and the major interactions (notably metformin and anticholinergics)
- Confirmation of the approved indications and available formulations for the ARTG entry
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.