Lowered plasma conc of immunosuppressants (eg, ciclosporin, tacrolimus), OCs & some other antiepileptics (eg, carbamazepine). Decreased mean AUC values of ethinylestradiol & levonorgestrel. Decreased mean AUC & C
min of carbamazepine. Increased mean AUC & C
min of phenobarbitone & phenytoin. Decreased mean AUC & C
min w/ carbamazepine, phenobarbitone, phenytoin & valproic acid. Increased risk of nausea, somnolence, dizziness & headache w/ lamotrigine. Possible interaction w/ MAOIs. May cause enhanced neurotoxicity w/ lithium.