💊 Topiramate (Topiramate)

🏷️ Brand names & manufacturers

Topamax🏭 Janssen Pharmaceuticals, Inc.DailyMed

Trokendi Xr🏭 Supernus Pharmaceuticals, Inc.DailyMed

Qudexy Xr🏭 Upsher-Smith Laboratories, LLCDailyMed

Topiramate🏭 Ascend Laboratories, LLCDailyMed

Topiramate🏭 Par Health USA, LLCDailyMed

Topiramate🏭 CDailyMed

✅ What it is used for

• Initial monotherapy for partial-onset or primary generalized tonic-clonic seizures in patients 2 years and older
• Adjunctive therapy for partial-onset seizures, primary generalized tonic-clonic seizures, and seizures associated with Lennox-Gastaut syndrome in patients 2 years and older
• Preventive treatment of migraine in patients 12 years and older

🧪 Active ingredient

The active substance is topiramate, a sulfamate-substituted monosaccharide. Its precise mechanism is unknown, but studies suggest it blocks voltage-dependent sodium channels, augments GABA activity at some GABA-A receptor subtypes, antagonizes the AMPA/kainate glutamate receptor, and inhibits the carbonic anhydrase enzyme.

🌿 Benefits

• Reduces partial-onset and primary generalized tonic-clonic seizures
• Helps control seizures associated with Lennox-Gastaut syndrome
• Prevents migraine attacks

📝 How to use

• Taken by mouth; the dose and gradual titration schedule are set by the doctor according to the condition and age.
• The dose is usually divided into two doses daily and increased gradually over weeks.
• Sprinkle capsules may be swallowed whole or opened and sprinkled onto soft food.
• Do not stop suddenly; the drug should be withdrawn gradually under medical supervision.
• Do not change the dose yourself; the dose is determined by the doctor or pharmacist.

💊 Dosage forms

• Tablets: 25 mg, 50 mg, 100 mg, 200 mg
• Sprinkle capsules: 15 mg, 25 mg, 50 mg

🔄 Drug interactions

• Phenytoin or carbamazepine: decrease topiramate plasma concentrations; dose adjustment may be needed
• Valproic acid: associated with hypothermia and hyperammonemia with or without encephalopathy
• Other carbonic anhydrase inhibitors (e.g., zonisamide, acetazolamide): may increase metabolic acidosis and kidney stone risk
• Alcohol and other CNS depressants: use with extreme caution
• Contraceptives: efficacy may decrease and breakthrough bleeding may increase, especially at doses above 200 mg/day
• Lithium: monitor levels when used with high-dose topiramate

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👨‍⚕️ For healthcare professionals

Mechanism of action

Precise mechanism unknown; blocks voltage-dependent sodium channels, augments GABA activity at some GABA-A receptor subtypes, antagonizes the AMPA/kainate glutamate receptor, and inhibits carbonic anhydrase (particularly isozymes II and IV).

Labeled dosing

Monotherapy epilepsy (adults and pediatric patients 10 years and older): recommended dose 400 mg/day in two divided doses, titrated from 25 mg morning and evening in Week 1 to 200 mg morning and evening in Week 6. Adjunctive therapy in adults: 200–400 mg/day in two divided doses (partial-onset seizures or Lennox-Gastaut) and 400 mg/day (primary generalized tonic-clonic seizures), starting at 25–50 mg/day and increasing by 25–50 mg/day weekly. Pediatric 2–16 years (adjunctive): approximately 5–9 mg/kg/day in two divided doses. The final dose is determined by the prescriber, with adjustments for renal impairment, elderly patients and hemodialysis.

• Baseline and periodic serum bicarbonate measurement is recommended
• Consider dose reduction or discontinuation for metabolic acidosis if clinically appropriate
• Measure ammonia if encephalopathic symptoms occur
• Withdraw gradually
• Discontinue for DRESS, serious skin reactions, or anaphylaxis if an alternative etiology cannot be established
• Ask patients on contraceptives to report any change in bleeding pattern

🎓 Key points for students

• Class: antiepileptic and migraine preventive; carbonic anhydrase inhibitor, CYP3A4 inducer, CYP2C19 inhibitor.
• Four proposed mechanisms: Na+ channel block, GABA-A potentiation, AMPA/kainate antagonism, carbonic anhydrase inhibition.
• Key adverse effects: paresthesia, anorexia, weight loss, speech problems, somnolence, memory difficulty.
• Major warnings: acute angle closure glaucoma, metabolic acidosis, oligohidrosis, kidney stones, hyperammonemia.
• Fetal toxicity: oral clefts and small for gestational age.
• Interactions: phenytoin and carbamazepine (lower its levels), valproic acid (hyperammonemia/hypothermia), contraceptives, other carbonic anhydrase inhibitors.
• Overdose: hemodialysis effectively removes topiramate.