[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/) › Topiramate

[Pharmacology](https://durgical.com/en/pharmacology/) · [Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/)

# Topiramate

An antiseizure and migraine-prevention medicine with several targets. It causes weight loss, tingling, slowed thinking and kidney stones.

Updated 2026-11-01

- Class: [Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/)
- Enzyme: Several targets; the figure shows carbonic anhydrase II
- ATC code: N03AX11

✂**Several targets; the figure shows carbonic anhydrase II**Topiramate

ⓘ The figure shows topiramate bound to human carbonic anhydrase II, one of its targets. Inhibiting this enzyme explains metabolic acidosis and kidney stones; the antiseizure effect also involves sodium channels, GABA-A and AMPA/kainate receptors.

**Target in 3D:** Several targets; the figure shows carbonic anhydrase II. PDB structure 3HKU (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3HKU) · Drag to rotate · pinch to zoom

## Mechanism of action

Topiramate blocks voltage-gated sodium channels, strengthens GABA at some GABA-A receptor subtypes and blocks the AMPA/kainate type of glutamate receptor. It also inhibits carbonic anhydrase, which causes metabolic acidosis, kidney stones and less sweating.

- Blocks voltage-gated sodium channels
- Strengthens GABA at some GABA-A receptors
- Blocks AMPA/kainate glutamate receptors
- Also inhibits carbonic anhydrase (acidosis, stones)

## Pharmacokinetics

**Absorption**
Absorbed by mouth

**Metabolism**
Not extensively metabolized

**Elimination**
About 70% unchanged in the urine; the dose is adjusted in kidney disease

**Half-life**
About 21 hours

## Indications

- Focal and generalized tonic-clonic seizures, and seizures of Lennox-Gastaut syndrome [Epilepsy and seizures →](https://durgical.com/en/conditions/epilepsy-and-seizures/)
- Migraine prevention (not for an attack already under way) [Migraine →](https://durgical.com/en/conditions/migraine/)

## Adverse effects

### Common

- Tingling (paraesthesia)
- Loss of appetite and weight loss
- Slowed thinking, word-finding and memory problems
- Altered taste
- Dizziness, fatigue and drowsiness

### Serious (rare, important)

- Acute myopia with secondary angle-closure glaucoma
- Metabolic acidosis and kidney stones
- Reduced sweating with high body temperature, especially in children
- Oral clefts in babies exposed in pregnancy
- Hyperammonaemia, mostly with valproate

## Contraindications

- None listed in the label; it is avoided with other carbonic anhydrase inhibitors and the ketogenic diet because of kidney stones

## Key interactions

**Hormonal contraceptives**
Less contraceptive effect and breakthrough bleeding

**Valproate**
Hyperammonaemia, encephalopathy and hypothermia

**Other carbonic anhydrase inhibitors (acetazolamide, zonisamide)**
More metabolic acidosis and kidney stones

**Anticholinergic drugs**
More risk of heat-related illness

## What is monitored

- Serum bicarbonate at baseline and periodically
- Eye symptoms: sudden blurred vision or eye pain
- Sweating and body temperature in children
- Weight, mood and cognition

## Administration and safety

- Given by mouth; immediate- and extended-release forms are not swapped without care
- Good fluid intake helps prevent kidney stones
- Withdrawn gradually: stopping suddenly can trigger seizures

## Nursing care

- Teach to report sudden blurred vision or eye pain at once
- Encourage plenty of fluids, and watch for flank pain or blood in the urine
- Watch children for reduced sweating and fever in hot weather
- Warn about slowed thinking before driving
- Remind that hormonal contraception may be less effective

## Pregnancy and breastfeeding

Exposure in pregnancy raises the risk of cleft lip or palate and of a baby small for gestational age.

## Memory aid

Topiramate «STONES»: Slow thinking, Tingling, ON a diet (weight loss), Nephrolithiasis, Eyes (angle-closure glaucoma), Sweating less.

## Test yourself

Think of the answer, then tap the question to see it.

## Which eye emergency is linked to topiramate?

Acute myopia with secondary angle-closure glaucoma, usually in the first weeks; vision can be lost permanently if the drug is not stopped.

## Why does topiramate cause kidney stones and metabolic acidosis?

It inhibits carbonic anhydrase, which lowers bicarbonate reabsorption and favours stone formation.

## Besides epilepsy, what is topiramate used for?

Migraine prevention; it does not treat an attack that has already started.

## Which birth defect is linked to topiramate in pregnancy?

Oral clefts (cleft lip and/or palate).

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/topiramate/)

## Related drugs

- [Zonisamide](https://durgical.com/en/pharmacology/zonisamide/)
- [Valproic acid](https://durgical.com/en/pharmacology/valproic-acid/)

## Related conditions

- [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/)
- [Migraine](https://durgical.com/en/conditions/migraine/)

[← Back to the class: Antiseizure medicines](https://durgical.com/en/pharmacology/classes/antiseizure-medicines/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Topiramate: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a697012.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - TOPIRAMATE tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e5bc696e-040d-4d3e-b38c-9548a38fa936) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N03AX11) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/topiramate/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/topiramate/