Dosage Forms. Capsule, Sprinkle: 15 mg, 25 mg; Tablet: 25 mg, 50 mg, 100 mg, 200 mg
Common FDA Label Indication, Dosing, and Titration.
1. Partial or tonic-clonic seizure, monotherapy or adjunct: Children 2-16 y of age, 1-3 mg/kg/d (max 25 mg) po daily × 1 wk, may titrate to usual dose of 5-9 mg/kg/d; Children 17 y of age and older and Adults, 25 mg po bid × 1 wk, may titrate to max of 200 mg po bid
2. Migraine prophylaxis: Initially 25 mg po daily × 1 wk, may titrate to max of 50 mg po bid
1. Bipolar disorder: 25 mg po bid × 1 wk, may titrate to max of 1200 mg/d po
MOA. The exact mechanisms by which topiramate exerts its anticonvulsant and migraine prophylaxis effects are unknown. Electrophysiological and biochemical evidence suggests that topiramate blocks voltage-dependent sodium channels, augments the activity of the neurotransmitter gamma-aminobutyrate at some subtypes of the GABA-A receptor, antagonizes the AMPA/kainate subtype of the glutamate receptor, and inhibits the carbonic anhydrase enzyme, particularly isozymes II and IV.
Drug Characteristics: Topiramate
Medication Safety Issues: Topiramate
Drug Interactions: Topiramate
Adverse Reactions: Topiramate
Efficacy Monitoring Parameters. Decreased seizure frequency or frequency of migraine headaches.
Toxicity Monitoring Parameters. Monitor electrolytes, hydration, and occurrence of suicidal thoughts.
Key Patient Counseling Points. Avoid activities requiring mental alertness and coordination until drug effects are realized, as drug may cause dizziness and somnolence, especially if taken with alcohol or other CNS depressants. May cause nausea, diplopia, nervousness, confusion, and many other CNS effects. Do not discontinue drug abruptly, as this may cause increased seizure activity. Seek medical attention for new eye problems or high body temperature. May decrease sweating; avoid hot temperatures (including hot tubs and saunas).
Clinical Pearls. When adjusting dose, make small changes slowly (“start low and go slow”) to avoid acute adverse effects.