OBJECTIVEOver half of children with infantile epileptic spasms syndrome (IESS) do not respond to standard treatments. Nitrazepam has shown efficacy similar to adrenocorticotrophic hormone. This study evaluated response rates, adverse effects of nitrazepam, and factors associated with responders in children with IESS who failed standard treatment.METHODSWe conducted a retrospective observational study of children with IESS who failed standard treatments and subsequently received nitrazepam between January 1, 2013, and December 31, 2021. Responders were defined as those achieving sustained clinical resolution of epileptic spasms without relapse at the 3-month follow-up. Etiologies were classified according to the 2017 International League Against Epilepsy classification.RESULTSThe study included 85 children, with 26 (30.5 %) children showing a response to nitrazepam. Adverse effects occurred in 52 (61.2 %) children, with hypersalivation (47.1 %) being the most common. At the 12-month follow-up visit, 20 (23.5 %) children had sustained clinical resolution of epileptic spasms, with no recorded deaths. Etiology was known in 73.3 % (structural 52 %; infectious 10.7 %; genetic 8 %; metabolic 2.7 %) and unknown in 26.7 %. Known etiology increased the likelihood of responding to nitrazepam (adjusted OR 5.78, 95 % CI 1.17, 28.72, p = 0.032), while a longer duration from epileptic spasms onset to nitrazepam decreased the odds of response (adjusted OR 0.85, 95 % CI 0.74, 0.98, p = 0.021).CONCLUSIONApproximately, 31% of children responded to nitrazepam. Early initiation of treatment with nitrazepam may be beneficial for children with IESS, particularly those with a known etiology, after failure of standard treatments.