Topiramate — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Topiramate?
Topiramate is an anticonvulsant used for epilepsy and migraine prevention. This medication is funded by Pharmac for epilepsy; not funded for migraine prevention.
What is Topiramate Used For?
Used as monotherapy or adjunct for focal seizures and generalised tonic-clonic seizures, and for migraine prophylaxis.
How Does Topiramate Work?
Blocks voltage-gated sodium channels, enhances GABA-A activity, antagonises AMPA/kainate glutamate receptors, and weakly inhibits carbonic anhydrase — reducing neuronal excitability.
How to Take Topiramate
Start at 25–50 mg/night and titrate slowly. Migraine prophylaxis: 50–100 mg/day in two divided doses. Epilepsy: up to 400 mg/day. Drink at least 2L water daily to reduce kidney stone risk.
Common Side Effects of Topiramate
- Cognitive slowing and word-finding difficulty (“brain fog” — dose-dependent)
- Paraesthesia (tingling in hands and feet — very common)
- Fatigue
- Anorexia and weight loss
- Mood changes
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Kidney stones (increase fluid intake)
- Acute angle-closure glaucoma (sudden eye pain/vision change — stop and seek urgent care)
- Metabolic acidosis
- Oligohidrosis and hyperthermia (especially in children)
- Teratogenicity (cleft palate, IUGR)
Drug Interactions
Topiramate may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Sodium valproate (increased hyperammonaemia risk)
- Combined oral contraceptive pill (topiramate reduces oestrogen — use additional contraception)
- Carbonic anhydrase inhibitors (increased kidney stone risk)
New Zealand Prescribing Information
Topiramate (25 mg, 50 mg, 100 mg tablets — Topamax® and generics) is funded for epilepsy only. Not funded for migraine prevention — requires private purchase. Women of childbearing age must use effective contraception (note: topiramate reduces COC efficacy).
Frequently Asked Questions
Will topiramate affect my memory?
Cognitive side effects (“brain fog”, word-finding difficulty) are dose-dependent and common. Slow titration minimises this. If severe, discuss a dose reduction with your neurologist.
How do I reduce kidney stone risk on topiramate?
Drink at least 2 litres of water daily, stay hydrated, and avoid dehydration. Topiramate increases urinary calcium phosphate stone formation risk.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: