Concomitant use w/ antiepileptics (eg, primidone, phenytoin, barbiturates, carbamazepine, oxcarbazepine, topiramate, felbamate), anti-TB (eg, rifampicin, rifabutin), anti-HIV infections (eg, ritonavir, nevirapine), antibiotics (eg, penicillins, tetracyclines, griseofulvin), St. John's wort. Inhibited metabolism w/ ketoconazole, erythromycin, cyclosporine. Increased plasma & tissue conc w/ cyclosporine. Decreased plasma conc w/ lamotrigine. Increased serum K levels w/ AIIA & diuretics.