A reasonable dosage regime for 2-12 year-olds is the commencement of lamotrigine 0.15mg/kg/second-daily (for a week), then 0.15mg/kg/daily (for 2 weeks). 

One can continue with an escalation of 0.15mg/kg/day each two weeks to the target dose. If the patient is tolerating the combination therapy, the lamotrigine titration dosage could be increased with careful monitoring (particularly looking for rash - see precautions) to 0.3mg/kg/day during the latter part of the escalation phase. 

The maintenance dose is 1-4mg/kg/day.  

Maximum dose is 5mg/kg/day given as a single dose or two equally divided doses. The maximum dose of lamotrigine with valproate in this age group is generally not above 200mg/day. Dosages per kilogram can only be used up to weights of 30-40kgs.

• Adding lamotrigine to valproate does not appear to affect valproate levels.
• On lamotrigine, a recommended maximum dose of valproate is approximately 30mg/kg.
• All anti-seizure medications are potentially teratogenic and this is often dose related.
• For a complete list of adverse effects, appropriate formularies should be consulted.

Oral contraceptives and the other anti-seizure medications that induce hepatic glucuronidation will also decrease the level of lamotrigine.

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 a serious rash significantly (Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis). Lower doses of lamotrigine and slow escalation are required.