Effects of anticonvulsants on local anaesthetic-induced neurotoxicity in rats.

The effects of various anticonvulsants on local anaesthetics procaine- and lidocaine-induced convulsions were investigated in rats. Pretreatment with diazepam (2.5-5 mg/kg, intraperitoneally) and clonazepam (5-10 mg/kg, intraperitoneally) completely protected the rats against both local anaesthetic-induced convulsions. Phenobarbital (12.5-50 mg/kg, subcutaneously) also significantly decreased the incidence of both convulsions and prolonged their latencies. Carbabazepine (10-40 mg/kg, intraperitoneally) did not completely repress both convulsions, but it prolonged their latencies. Phenytoin (5-20 mg/kg, intraperitoneally) and primidone (30-60 mg/kg, intraperitoneally) markedly enhanced both local anaesthetic-induced convulsions, as shown by shortening of latency and increase in mortality. Valproate (100-200 mg/kg, intraperitoneally) produced a protective effect against procaine-induced convulsions, while it strongly enhanced lidocaine-induced convulsions. These results suggest that the benzodiazepines are effective drugs to prevent neurotoxicity induced by local anaesthetics, while phenytoin and primidone potentiate them.