Children's epilepsy resource for Clinicians

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Topiramate

 

Usage:

  • Topiramate has a broad range of seizure efficacy and on the Australian PBS can be considered in treatment for partial epileptic seizures, primary generalised tonic-clonic seizures and seizure of Lennox Gastaut Syndrome not controlled satisfactorily by other antiepileptic drugs.
  • Side effects (irritability, anorexia, sedation) should be considered before prescribing. 
  • It has been used in neonates and infants.

 

NOTABLE Side Effects:

  • Marked loss of appetite/loss of weight may require cessation of drug. 
  • Metabolic acidosis (topiramate is a carbonic anhydrase inhibitor) is a common finding in young infants. Blood bicarbonate levels around 16-18mmol/L are to be expected and usually cause no significant problems. Lower levels may require treatment. 
  • Nephrocalcinosis can occur and patients on long term treatment or who have other risk factors can be monitored with urine studies and renal ultrasound.
  • Reduced sweating may cause heat intolerance which is manageable with simple measures. Care must be taken in warm climates. In the very young heat intolerance can be a more serious side effect and overheating must be avoided.
  • Word finding difficulty and language impairment may be pronounced and are more of a risk with higher doses. 
  • Sedation can occur but is more common with higher doses. 
  • Mood disturbance (irritability, crankiness, depression) can occur. 
  • Glaucoma is a contraindication. Advise urgent review if painful eyes develop.
  • Rarely, visual field defect is described.
  • Paraesthesia’s and hand tingling can occur but are uncommon.
  • All anticonvulsants are potentially teratogenic and this is often dose related (see section: Pregnancy and AEDs)
  • For a complete list of adverse effects, appropriate formularies should be consulted.

 

Dosing:

  • The initiation and escalation dose depends upon age, weight, syndrome, seizure frequency and intensity, and side effect profile.
  • Unfortunately, a one dose regime does not fit all. A Paediatric Neurologist should be consulted if there is uncertainty.

 

A commonly used regime is below:

  • Typical dosage is approximately 5mg/kg/day in two divided doses.  Some patients may respond to 2mg/kg/day.  Dose can be increased to 8-9mg/kg/day in refractory cases (a patient is probably failing the drug if there is no significant effect on seizures above 7mg/kg/day). Advice from a Paediatric Neurologist may be helpful.
  • Starting dose 0.5-1mg/kg/day in two divided doses increasing either weekly or fortnightly by 0.5mg/kg/day to target.  In certain acute situations such as an epileptic encephalopathy or status, initiating dose can be higher (e.g. 2mg/kg/day) and rate of escalation faster. Consultation with Paediatric Neurology may be helpful.
  • Dosages per kilogram can only be used in children of weight approximately up to 30-40kgs. Consult appropriate formularies for higher weights and in the adult range.
  • These dosages are only a guideline and appropriate formularies should be consulted as needed. 

 

Preparations:

  • Tablets 25mg, 50mg, 100mg, 200mg;  Topamax Sprinkle Capsule 15mg, 25mg, 50mg.  Tablets or capsule contents can be dissolved to make a liquid form.  It can be given rectally if a patient is fasting.

 

Monitoring and Levels:

  • Drug level monitoring is not routinely utilized or readily available. 
  • Blood bicarbonate should be checked within a month as a guide and then at intervals with escalation. This is particularly important in the infant.
  • Renal ultrasound and urine testing are considered as necessary, particularly if back pain or haematuria

 

Drug InteractionS:

  • Topiramate may decrease serum concentrations of oestrogens.
  • Topiramate may increase toxicity of sodium valproate.
  • Topiramate concentration may be decreased by carbamazepine.

 

 

MIMS

PBS

 

Parent Handout

 

 

This website was created in March 2012. This page was last modified in December 2017.