OBJECT DRUGS

• Lamotrigine (Lamictal, etc.)

PRECIPITANT DRUGS

• Valproic Acid (Depakene, etc.)

Comment:

Valproic acid may substantially increase lamotrigine serum concentrations, probably through inhibition of lamotrigine metabolism. It has also been proposed that the combination of lamotrigine and valproic acid may increase the risk of serious skin eruptions such as Stevens-Johnson syndrome or toxic epidermal necrolysis, but a causal relationship has not been established. Isolated cases of hyperammonemic encephalopathy have been reported in patients receiving lamotrigine and valproic acid concurrently, but more study is needed to establish the clinical importance.

Class 3: Assess Risk & Take Action if Necessary

• Monitor: Monitor for altered lamotrigine effect if valproic acid is initiated, discontinued, or changed in dosage. Adjustments in lamotrigine dosage may be necessary. Monitor also for evidence of encephalopathy (lethargy, tremor, asterixis, and elevated ammonia levels).