Drug Index


Mechanism :

The precise mechanisms by which topiramate exerts its anticonvulsant and migraine prophylaxis effects are unknown; however, preclinical studies have revealed four properties that may contribute to topiramate's efficacy for epilepsy and migraine prophylaxis. Electrophysiological and biochemical evidence suggests that topiramate, at pharmacologically relevant concentrations, 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

Indication :

  • Partial seizures
  • Generalised tonic-clonic seizures
  • Absence-Atonic seizures
  • Lennox-Gastaut syndrome
  • Migraine

Contraindications :

Contraindicated in patients with a history of hypersensitivity to any component of this product. Ensure adequate hydration to avoid nephrolithiasis. Acute myopia and glaucoma may occur rarely.

Dosing :

2 to <10 years:
25 mg (1-3 mg/kg/day) at bedtime for a week, orally. Increase dose by 1-3 mg/kg/day at 1-2 week intervals, divided 12 hourly to 5-9 mg/kg/day (Max: 250 mg/day in children weighing <11 kg, 300 mg/day in children between 12-22 kg, 350 mg/day in children weighing >23 kg).
>10 years:
200 mg/dose PO 12 hourly. Start with 25 mg PO BD and then increase weekly.

Adverse Effect :

Anorexia, somnolence, decrease in serum bicarbonate, nervousness, paresthesia, psychomotor slowing, abnormal vision, confusion, decreased memory, speech disorder, nausea, fatigue, ataxia. Chronic adverse effects include reduced appetite, anorexia and behavioural changes.

Interaction :

Phenytoin: May increase plasma phenytoin levels.
Digoxin: May decrease digoxin levels.
Oral Contraceptives: May decrease the effectiveness of oral contraceptives, advise patients to use other measures.
Carbamazepine and Phenytoin: may decrease topiramate levels.

Renal Dose :

Dose in Renal Impairment GFR (mL/min)
20-50Migraine/epilepsy: Dose as in normal renal function
10-20Migraine: Dose as in normal renal function Epilepsy: 50% of normal dose and increase according to response
<10Migraine: Dose as in normal renal function Epilepsy: 25–50% of normal dose and increase according to response

Dose in Patients undergoing Renal Replacement Therapies
CAPDUnknown dialysability. Dose as for GFR<10 mL/min
HDDialysed. Dose as for GFR<10 mL/min
HDF/High fluxDialysed. Dose as for GFR<10 mL/min
CAV/VVHDUnknown dialysability. Dose as for GFR=10–20 mL/min

Hepatic Dose :

Dose reduction may be needed as drug is metabolised by liver. Plasma levels can be increased due to reduced clearance.
01/24/2024 18:42:32 Topiramate
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