- Use of the following medication, as of interaction with lamotrigine: phenytoin, carbamazepine, phenobarbital, primidon, rifampicin, atazanavir/ritonavir, lopinavir/ritonavir, oxcarbazepine, topiramate, oral contraceptive pill including stop-week (estrogen and progesterone) and valproic acid during 3 months before inclusion.