Liposomes (LIPO), which are concentric lipid layers alternating with aqueous compartments, have been suggested as a potential carrier for various drugs. In the previous studies, we have demonstrated that anticonvulsant drugs such as valproic acid, phenytoin, and DN-1417 (an analog of thyrotropin-releasing hormone) entrapped into LIPO exert more prominent therapeutic efficacy than parent drugs. In the present study, we examined the comparative effects of Lidocaine (LDCA) which acts as a proconvulsant as well as an anticonvulsant, and LIPO-entrapped LDCA (LDCA-L) on limbic status epilepticus originating in the amygdala (AM) of rats. LDCA (LDCA hydrochloride) was dissolved in distilled water as a vehicle at a concentration of 2.5 mg/ml or 10 mg/ml. LIPO and LDCA-L were prepared from L-alpha-phosphatidylcholine, cholesterol, and stearylamine. Status epilepticus was induced by intra-AM injection of combined dibutyryl (db)-cAMP-200 micrograms/ethylene diaminetetraacetic acid (EDTA)-67.2 micrograms through the implanted cannula. The animals were divided into 4 groups which received vehicle (n = 6), LIPO (n = 5), LDCA (n = 9), and LDCA-L (n = 10). LDCA group was subdivided into 5 mg/kg (n = 4) and 20 mg/kg (n = 5) groups. LDCA-L group was treated with 5mg/kg (n = 4) or 20mg/kg (n = 6). All drugs were intravenously given at a volume of 2ml/kg via teflon tube previously inserted into cervical vein 30 min after db-cAMP/EDTA injection. Vehicle or LIPO alone did not alter the pattern of electroclinical ictal responses produced by intra-AM injection of db-cAMP/EDTA.(ABSTRACT TRUNCATED AT 250 WORDS)