Lamotrigine and Valproic acid interaction

…addition to age, factors that may increase the risk of occurrence or the severity of rash caused by lamotrigine include (1) coadministration of lamotrigine with valproate (includes valproic acid and divalproex sodium), (2) exceeding the recommended initial dose of lamotrigine, (3) exceeding the recommended dose escalation for lamotrigine, or (4) the presence of…

Patients with History of Allergy or Rash to Other Antiepileptic Drugs The risk of rash may be increased in patients with a history of allergy or rash to other AEDs.

Children under the age of two years are at a considerably increased risk of developing fatal hepatotoxicity, especially those on multiple anticonvulsants, those with congenital metabolic disorders, those with severe seizure disorders accompanied by mental retardation, and those with organic brain disease.

In patients over two years of age who are clinically suspected of having a hereditary mitochondrial disease, valproic acid oral solution should only be used after other anticonvulsants have failed.

Lamotrigine In a steady-state study involving 10 healthy volunteers, the elimination half-life of lamotrigine increased from 26 to 70 hours with valproate co-administration (a 165% increase).

The dose of lamotrigine should be reduced when co-administered with valproate.

Patients on multiple anticonvulsants, children, those with congenital metabolic disorders, those with severe seizure disorders accompanied by mental retardation, and those with organic brain disease may be at particular risk.