Topiramate (Topamax)

Class

Anticonvulsant / Mood stabilizer adjunct

Mechanism

Blocks voltage-dependent sodium channels, enhances GABA activity, antagonizes AMPA/kainate glutamate receptors, and inhibits carbonic anhydrase isoenzymes, contributing to anticonvulsant and mood-stabilizing effects.

FDA-Approved Use

Epilepsy, migraine prophylaxis

Off-Label Use

Augmentation in mood disorders, management of anger and aggression in post-traumatic stress disorder (PTSD) and traumatic brain injury (TBI), binge eating disorder, weight loss in patients with obesity

Formulation

Tablets, extended-release tablets

Titration

Start at 25 mg p.o. nightly, titrate slowly (typically increasing by 25–50 mg/week) to target dose of 25–200 mg/day depending on indication and tolerability

Dose Range

25–200 mg/day (psychiatric augmentation)

Kinetics

Half-life approximately 21 hours; primarily renally excreted; dose adjustments needed in renal impairment

Common AEs

Cognitive slowing (including word-finding difficulty), paresthesias, fatigue, appetite suppression, weight loss, dizziness

Serious/Rare AEs

Angle-closure glaucoma, metabolic acidosis, oligohidrosis, nephrolithiasis (kidney stones)

Monitoring

Periodic monitoring of serum bicarbonate, weight, hydration status, and renal function (especially in patients with history of nephrolithiasis or renal impairment)

Black Box Warning

None

Considerations

Particularly useful in patients with comorbid obesity, binge eating disorder, or impulsivity. Use cautiously in elderly or cognitively vulnerable individuals due to risk of executive dysfunction and cognitive side effects. Careful monitoring and slower titration recommended in patients with renal impairment or history of kidney stones to minimize adverse effects.