Topiramate (Topamax)

Clinical Information:

HALF-LIFE: 19-25 hours
STARTING DOSE: 12.5mg-25mg per day
TARGET DOSING RANGE: 50mg-200mg per day
> Initial 12.5mg-25mg per day
> Increase dose by 25mg per week
> For weight loss/prevent weight gain: 50mg-150mg/day
> For Mood effects: Usually 100mg-200mg per day in divided doses
> Max dose usually 400mg/day
PREGNANCY: Minimal data on safety.
BREASTFEEDING: Minimal date on safety.


1) Epilepsy
2) Prophylaxis of Migraine headaches


Topiramate has also been used off label for:

  • Antipsychotic-induced weight gain (usually 50mg-150mg daily)
  • Neuropathic pain
  • Borderline personality disorder
  • Alcohol use disorders
  • Cocaine use disorders


Mechanism(s) of Action:

  • Blocks voltage sensitive sodium channels
  • Inhibits glutamate release
  • Potentiates activity of GABA
  • Blocks calcium channels
  • Topiramate inhibits carbonic anhydrase (increased risk of metabolic acidosis and kidney stones)
  • Topiramate may have prophylactic properties, but appears to exert little benefit during acute bipolar depression or mania.


Side Effects:

  • Psychomotor slowing
  • Decreased concentration
  • Somnolence
  • Fatigue
  • Anorexia
  • Kidney stone formation
  • Cognitive side effects (“Dope-a-max” or topamax “fog”) most common reason for discontinuing


Additional Information:

  • Used in children with Lennox-Gastaut Syndrome
  • Carbamazepine increases elimination of topiramate
  • Topiramate may increase plasma levels of phenytoin
  • Topiramate is a weak inhibitor of CYP219
  • Topiramate is weak inducer of CYP3A4
  • Alcohol enhances sedation and may increase risk of seizures


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