Section 01 · Monograph

Topiramate

Reviewed Nov 2026FDA label

TopamaxMulti-mechanism AED

Indications

Monotherapy for partial-onset or primary generalized tonic-clonic seizures, age 2 years and olderFDA-labeled
Adjunctive therapy for partial-onset seizures, primary generalized tonic-clonic seizures, and seizures associated with Lennox-Gastaut syndrome, age 2 years and olderFDA-labeled
Prophylaxis of migraine headache in adultsFDA-labeled

Multiple proposed mechanisms: blockade of voltage-gated sodium channels, potentiation of GABA-A receptor activity at a non-benzodiazepine site, antagonism of AMPA/kainate glutamate receptors, and weak inhibition of carbonic anhydrase isoenzymes (notably II and IV)

Epilepsy monotherapy (adults/adolescents ≥10 years): initiate at a low dose and titrate weekly per label schedule toward a target around 400mg/day divided twice daily
Epilepsy adjunctive therapy (adults): titrate to 200–400mg/day divided twice daily (400mg/day typically used for primary generalized tonic-clonic seizures)
Migraine prophylaxis (adults): titrate slowly (e.g., 25mg/week increments) to a target of 100mg/day divided twice daily, to improve tolerability
Taper gradually when discontinuing to minimize rebound seizure risk

Reduce dose by approximately half in significant renal impairment; supplemental dose recommended after hemodialysis

No absolute contraindications are identified in FDA labeling; avoid in patients with known hypersensitivity to topiramate

Carbonic anhydrase inhibition can be additive with other CA inhibitors (e.g., zonisamide, acetazolamide), increasing metabolic acidosis and nephrolithiasis risk
Reduces efficacy of estrogen-containing oral contraceptives at doses above 200mg/day — advise alternative or additional contraception
Phenytoin and carbamazepine can reduce topiramate serum concentrations; topiramate can also affect phenytoin levels
Concomitant valproic acid increases risk of hyperammonemia (with or without encephalopathy) and hypothermia
Additive CNS depressant effects with alcohol and other sedating drugs

Cognitive dysfunction — word-finding difficulty, psychomotor slowing, impaired concentration and memory; dose-related and more common with higher doses or rapid titration
Weight loss and decreased appetite
Paresthesias, especially common at treatment initiation
Metabolic (non-anion gap, hyperchloremic) acidosis from renal bicarbonate wasting — may be asymptomatic or cause hyperventilation, fatigue, or arrhythmia
Acute myopia with secondary angle-closure glaucoma, typically within the first month of treatment — presents with acute vision change and eye pain and requires prompt discontinuation
Oligohidrosis and hyperthermia — more common in pediatric patients, especially with heat exposure; can be serious
Nephrolithiasis (kidney stones) from carbonic anhydrase inhibition, reduced urinary citrate, and urine alkalinization
Hyperammonemia with or without encephalopathy, particularly with concomitant valproate
Mood and behavioral changes, including increased risk of suicidal thoughts and behavior (AED class effect)

Serum bicarbonate at baseline and periodically to detect metabolic acidosis
New visual symptoms (acute eye pain or vision change) — evaluate urgently for secondary angle-closure glaucoma
Signs of oligohidrosis or hyperthermia, particularly in children in hot climates
Renal function and hydration status; encourage adequate fluid intake to reduce stone risk
Cognitive and mood changes, including suicidality
Growth parameters in pediatric patients

FDA has warned that first-trimester exposure is associated with an increased risk of oral clefts (cleft lip and/or cleft palate) in the newborn, based on pregnancy registry data
Use during pregnancy only if the potential benefit justifies the risk; discuss effective contraception, noting topiramate itself can reduce oral contraceptive efficacy at higher doses
Present in breast milk; monitor breastfed infants for sedation or poor feeding