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Lamotrigine and Valproate Combination


There is a significant synergistic drug interaction with valproate (valproate is an enzyme inhibitor, lamotrigine clearance is reduced and thus lamotrigine levels are higher).  This can increase risk of rash significantly.  Lower doses of lamotrigine and slow escalation are required.

A reasonable dosage regime is commencement of lamotrigine 0.15mg/kg/second daily (for a week), then same dose daily (for 2 weeks), then increase every 2 weeks by 0.15mg/kg/day to target 1-3mg/kg/day.  Maximal dose 4-5mg/kg/day.  Adding lamotrigine to valproate does not appear to affect valproate levels. On lamotrigine, a recommended maximum dose of valproate is approximately 30mg/kg.


  • 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. 
  • 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.


Oral contraceptives and the other anticonvulsants that induce hepatic glucuronidation will also decrease the level of lamotrigine.












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