Abstract *Hideji Hattori, *∥Tsunekazu Yamano, †∥Kitami Hayashi, †∥Makiko Osawa, ‡∥Shinichiro Hamano, and §∥Kenichiro Kaneko *Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka ; †Department of Pediatrics, Tokyo Woman's Medical University, School of Medicine, Tokyo ; ‡Division of Neurology, Saitama Children's Medical Center, Saitama ; §Department of Pediatrics, Juntendo University Urayasu Hospital, Japan ; and ∥Research Committee on Clinical Evidence of Medical Treatment for Status Epileptics in Childhood . Purpose: To evaluate the efficacy of intravenous lidocaine therapy in the management of status epilepticus (SE) in childhood. Subjects and Methods: This was a multiinstitutional, retrospective study. Questionnaires were sent to 30 hospitals with pediatric departments. Patients admitted for SE and managed with lidocaine were included. We collected background information of the patients (underlying diseases, seizure type, etc.), treatment, and efficacy. Results: Case cards (279) were collected. Patients older than 15 years and younger than 1 month were excluded. The data set analyzed included 257 cases. The mean age was 3.8 years, and 66% were younger than 3 years. Epilepsy was the diagnosis in 145 cases. The remaining 112 had nonepileptic diseases. The etiology of epilepsy was determined in 103 cases; of which 79 were from prenatal factors, eight from perinatal factors, and 16 from postnatal factors. Epilepsy type was diagnosed as localization related in 94 cases, generalized in 27 cases, and unclassified in 24 cases. Nonepileptic acute illness included 30 cases of benign infantile convulsion, 30 cases of acute encephalopathy/encephalitis, 13 cases of meningitis, and 39 other causes. Seizure type was diagnosed as generalized in 102 cases, secondarily generalized in 94 cases, and partial in 61 cases. We categorized SE into three groups: continuous (type I); cluster (type II); and frequently repeated (type III). Type III patients regained consciousness between seizures; therefore, type III did not meet the common definition of SE. The numbers of type I, type II, and type III cases were 73, 73, and 111, respectively. The mean dosage of lidocaine in initial loading therapy was 1.65 ± 1.12 mg/kg (206 cases), and the mean starting dosage of maintenance therapy was 2.11 ± 1.19 mg/kg/h (211 cases). The maximum maintenance dosage was 2.60 ± 1.69 mg/kg/h. Lidocaine was infused for a mean of 105 h. Lidocaine was selected as the first drug in 57 cases, the second in 83 cases, the third in 75 cases, and after the fourth in 42 cases. We defined effective as complete seizure control or seizure reduction by >50%, with no or mild adverse side effects. Overall, lidocaine was effective in 57% of cases. The treatment lag time and the order of medication used did not influence the efficacy of lidocaine. No difference in the efficacy rate was found between epileptic and nonepileptic disorders. Patients with benign infantile convulsions showed good responses to lidocaine, whereas SE patients with CNS infection showed poor responses. Efficacy was better in patients with types II and III SE compared with type I. Patients who showed good response to initial loading therapy of lidocaine were well controlled with maintenance therapy, whereas poor responders to initial infusion therapy showed almost no response to maintenance therapy. Therefore if the patients do not respond to the initial therapy, maintenance therapy will be unsuccessful. Adverse side effects were seen in 35 (13.6%) cases, and the risk of side effects was high with maintenance doses >4 mg/kg/h. Conclusions: Lidocaine is useful for the management of SE in childhood. It may be used as a first- or second-line medication for benign infantile convulsions, and patients with types II and III SE are good candidates for lidocaine use. However, lidocaine may be useful in every stage of SE when SE is not controlled by other medications. Patients who do not respond to an initial loading infusion will not achieve control by maintenance infusion.