Concomitant use w/ primidone, phenytoin, barbiturates, carbamazepine, oxcarbazepine, topiramate, felbamate; rifampicin, rifabutin; ritonavir, nevirapine; penicillins, tetracyclines, griseofulvin & St. John's wort. Metabolism may be inhibited by ketoconazole, erythromycin & cyclosporine. Increase plasma & tissue conc of cyclosporine. Decrease plasma & tissue conc of lamotrigine. AIIA, diuretics, aldosterone antagonists; ACE inhibitors or indomethacin.