Lamitor 50/Lamitor-100 Drug Interactions

There are complex interactions between antiepileptics and toxicity may be enhanced without a corresponding increase in antiepileptic activity. Such interactions are very variable and unpredictable and plasma monitoring is often advisable with combination therapy.
The metabolism of lamotrigine is enhanced by the enzyme inducers carbamazepine, phenytoin, phenobarbital, primidone, and inhibited by valproate. Use with rifampicin significantly increased the clearance of lamotrigine.
Protease inhibitors lopinavir/ritonavir and atazanavir/lopinavir decrease lamotrigine exposure by approximately 50% and 32%, respectively.
Lamotrigine is an inhibitor of renal tubular secretion via organic cationic transporter 2 (OCT2) proteins. This may result in increased plasma levels of certain drugs that are substantially excreted via this route. Coadministration of lamotrigine with OCT2 substrates with narrow therapeutic index (e.g., dofetilide) is not recommended.
Some estrogen-containing oral contraceptives have been shown to decrease serum concentrations of lamotrigine.