Lamotrigine

Usage

  • Lamotrigine is most commonly used in generalised epilepsies.
  • It has also been shown to be efficacious in focal seizure disorders.
  • PBS indication is for treatment of seizures not controlled by other antiepileptic drugs.
  • Care must be taken when combined with valproate (see later section).
  • Lamotrigine was found to be less efficacious than sodium valproate and ethosuximide in Childhood Absence Epilepsy. 1

 Resources

  • 1. Tracy A. Glauser et al. Ethosuximide, Valproic Acid, and Lamotrigine in Childhood Absence Epilepsy. N Engl J Med 2010; 362:790-799

Side effects

Notable side effects

  • Rash is the most serious side effect to monitor. Steven Johnson Syndrome has a higher risk of occurring in children than adults on lamotrigine. Co-treatment with sodium valproate is a significant risk factor (see section: lamotrigine and valproate combination). Previous skin reaction to another anticonvulsant also increases the risk. Starting at low dose and increasing very slowly decreases risk. Development of rash while on lamotrigine warrants urgent medical review. Red flags are new onset conjunctivitis, mucosal peeling, and systemic signs.
  • It is thought to be safer in pregnancy compared to sodium valproate; however there is still risk of teratogenicity. Pregnancy must be carefully monitored by a neurologist as drug levels change (see section: AED Prescribing - Pregnancy).
  • Patients often feel better on lamotrigine as it is a mood stabiliser.
  • Insomnia may occur and it is sometimes helpful to give the dosage early in the day.
  • Uncommon side effects include liver and haematological abnormalities.
  • Rarely ataxia or drowsiness are noted.

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.

 
Commonly used regime (Not for patients on sodium valproate)

  • 4-5mg/kg/day is a low target dose.  In some cases, up to 8mg/kg/day monotherapy can be used. It is usually given in two divided doses. In higher doses, consultation with a Paediatric Neurologist may be helpful.
  • Start at 0.5mg/kg/day (eg one dose at night, then increase to bd).  
  • Increase by 0.5mg/kg/day every 2 weeks until target.   
  • 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.

***If patient is on sodium valproate, see section: Lamotrigine and sodium valproate combination.

Preparation

  • Tablets 5mg, 25mg, 50mg, 100mg, 200mg.
  • No syrup form.

Monitoring

  • No drug level monitoring is currently available and no routine blood tests are required.

Interactions | Precautions

Care must be taken when lamotrigine is combined with sodium valproate.