Zonisamide

Evidence Level: L5

Predicted Indications: 9

Zonisamide

Pharmacist Assessment Report

Zonisamide: From Epilepsy to Tourette Syndrome

One-Sentence Summary

Zonisamide is an antiseizure medicine marketed in Australia as an oral capsule (the approved indication text was not available in the data compiled for this report). The TxGNN model predicts it may be effective for Tourette syndrome, but no clinical trials and no publications currently support this prediction. The prediction is model-based only and should be treated as a hypothesis.

Quick Overview

Item	Content
Original Indication	Not stated in the Australian registration data (zonisamide is generally used as an antiseizure medicine)
Predicted New Indication	Tourette syndrome
TxGNN Prediction Score	0.9985
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. Based on general pharmacology, zonisamide acts on voltage-gated sodium and T-type calcium channels and may modulate dopaminergic and serotonergic transmission. These pathways could plausibly relate to the neural circuits involved in tics, but this link is speculative.

Its efficacy in epilepsy is established, and mechanistically it may be applicable to other neurological and neuropsychiatric conditions. However, no direct data link zonisamide to Tourette syndrome.

There is also a possible safety signal. A pragmatic review (PMID 36005856) reports antiseizure medication-induced tic disorder, which raises concern rather than offering support.

Clinical Trial Evidence

Currently no related clinical trials registered for Tourette syndrome.

Literature Evidence

Currently no related literature available for Tourette syndrome. The only relevant item identified, 36005856 (2022, Review, Expert Rev Neurother), discusses antiseizure medication-induced obsessive-compulsive disorder and tic disorder, which is a safety signal rather than evidence of benefit.

Australia Market Information

ARTG Number	Product Name	Dosage Form	Approved Indication
ARTG 13853D	Zonegran	Capsule 25 mg	Not stated in the data compiled

Safety Considerations

Drug Interactions (100 interactions were identified; examples below):
- Major: anticholinergic agents (methscopolamine, hyoscyamine, atropine, scopolamine, glycopyrronium, clidinium, dicyclomine, trospium, mepenzolate, propantheline) and metformin.
- Moderate: aprepitant, morphine, dexamethasone, cimetidine, clarithromycin, dronabinol, nabilone, metoclopramide, miconazole.
Knowledge-graph contraindication signals (from the TxGNN knowledge graph, not label text): kidney disease and nephrolithiasis, liver disease, gallbladder disease, metabolic acidosis, neutropenia and agranulocytosis, and psychiatric disorders (anxiety, psychotic, schizoaffective and other mental disorders).

Please refer to the TGA-approved Product Information (PI) for warnings and contraindications, as label text was not available.

Conclusion and Next Steps

Decision: Hold

Rationale: The Tourette syndrome prediction rests on the model score alone, with no trials or literature, and a related review flags possible tic induction by antiseizure medicines.

To proceed, the following is needed:

Retrieve the TGA Product Information, including the approved indication, warnings and contraindications
Obtain detailed mechanism of action data (for example from DrugBank)
A systematic literature search and trial registry search (including ANZCTR) specific to Tourette syndrome
Preclinical or small exploratory clinical evidence, with attention to tic-exacerbation risk

Other Predicted Indications (Context)

Other predictions were also reviewed, but none is stronger than L4 evidence:

Predicted Indication	Score	Evidence Level	Comment
Manic bipolar affective disorder	0.9935	L5	One open-label report in bipolar depression (17163811) and a case report of zonisamide-induced mania (2109869).
Fibromyalgia	0.9920	L5	One Phase 4 trial (NCT00259636) was withdrawn with 0 enrolled.
Trichotillomania, Prinzmetal angina, conjunctivitis	99.16–0.9978	L5	Prediction only.
Methemoglobinemia (three entries)	0.9953–0.9964	L5	No credible mechanism. The scores come from the TxGNN model (deep learning) and may reflect similarities the model learned between related diseases, not biological evidence. Zonisamide is a sulfonamide, so safety concerns outweigh any benefit signal.

Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.