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Topiramate (Topamax)

Anticonvulsantprescriptionoral · inferred

Sulfamate-substituted monosaccharide anticonvulsant with multiple mechanisms: sodium channel blockade, GABA-A potentiation, AMPA/kainate glutamate antagonism, and carbonic anhydrase inhibition. Used for epilepsy, migraine prophylaxis, and weight loss (as component of Qsymia). Notable cognitive side effects (Dopamax) including word-finding difficulty. Reduces appetite through unclear mechanisms; 70% renally eliminated unchanged.

Projected serum levels — 50 mg, twice daily

Topiramate (Topamax)
Topiramate (Topamax) modeled serum levels, 50 mg twice daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 50 100 150 200 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Topiramate (Topamax) modeled serum levels with a loading dose of 150 mg, then 50 mg twice daily The first dose is larger so levels approach steady state faster. 0 50 100 150 200 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 50 mg twice daily (oral).

Loading schedule: 150 mg on day 1, then 50 mg twice daily — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 113 mg, trough ≈ 80.0 mg body load. Population-based estimate over 15 days for a 50 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Anticonvulsant
Route modeled
Oral
Model confidence
inferred
Half-life
21 h
Common dose
50 mg
Suggested maximum
400 mg/day
Reference dose range
25–400 mg (single dose)
Suggested cadence
twice daily
Validated against
200 mg oral — Cmax 3 mg/L at 2 h

Documented interactions

  • contraindicated
    Carbamazepine (Tegretol) + Topiramate (Topamax) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Topiramate (Topamax) AUC by ~0.20x

  • contraindicated
    Clarithromycin (Biaxin) + Topiramate (Topamax) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Topiramate (Topamax) AUC by ~10.00x

  • contraindicated
    Dasatinib (Sprycel) + Topiramate (Topamax) CYP inhibition

    Dasatinib (Sprycel) time_dependent_inhibitor of CYP3A4 predicted to change Topiramate (Topamax) AUC by ~5.00x

  • contraindicated
    Diltiazem + Topiramate (Topamax) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Topiramate (Topamax) AUC by ~10.00x

  • contraindicated
    Efavirenz (Sustiva) + Topiramate (Topamax) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Topiramate (Topamax) AUC by ~0.12x

  • contraindicated
    Grapefruit (whole fruit) + Topiramate (Topamax) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Topiramate (Topamax) AUC by ~10.00x

Serum checks 212 modeled interaction pairings for topiramate (topamax) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Topiramate in migraine prevention: results of a large controlled trial Brandes JL et al. · Neurology, 2004 DOI

    Pivotal RCT demonstrating topiramate 100 mg/day reduced migraine frequency by 50% in 54% of patients versus 23% with placebo, establishing it as a first-line migraine preventive.

  2. Efficacy and safety of topiramate in the treatment of obese subjects Bray GA et al. · Obesity Research, 2003 DOI

    Dose-ranging RCT showing topiramate 96-256 mg/day produced dose-dependent weight loss of 5-7% body weight versus 1.5% with placebo over 6 months, with sustained effect.

  3. Clinical pharmacokinetics of topiramate: a review Perucca E · Clinical Pharmacokinetics, 2006 DOI

    Comprehensive PK review establishing topiramate half-life of 19-25 hours, rapid absorption (tmax 1-4h), 80% bioavailability, primarily renal elimination, and modest hepatic metabolism inducible by…

3 published studies referenced in the app, each with a plain-language summary.