Purpose: To investigate the association between reduced prophylactic diazepam usage and short-term recurrence of febrile seizures (FSs) after the FS practice guideline was updated in Japan.

Method: In this single-center, retrospective study, children (6-60 months of age) with FS who were transported to our center by ambulance from January 2011 through December 2018 were included. Rectal administration of diazepam (0.3-0.5 mg/kg) after the first seizure and seizure recurrence within 24 h were compared between 2011-2015 (pre-guideline revision) and 2016-2018 (post-guideline revision).

Results: Among the total of 509 children, 297 were transported to our hospital in 2011-2015 and 212 in 2016-2018. Rectal diazepam administration was decreased in 2016-2018 (17 %) compared to 2011-2015 (53 %, P < 0.0001), while seizure recurrence was increased in 2016-2018 (20 %) compared to 2011-2015 (12 %, P = 0.0087). Similarly, hospital revisits (23 %) and hospital admissions (26 %) were increased in 2016-2018 compared to 2011-2015 (15 %, P = 0.031 and 18 %, P = 0.026, respectively). Multiple logistic regression analyses showed that prophylactic diazepam administration was the only factor related to preventing seizure recurrence. FS recurrence after the initial seizure was significantly less frequent with diazepam use (6 %) than without diazepam use (21 %, P < 0.0001; relative risk reduction, 70 %; number needed to treat, 6.8 children).

Conclusion: The FS practice guideline revision was associated with reduced prophylactic diazepam usage and increased FS recurrence within 24 h in Japan. Prophylactic diazepam use should be determined based on clinical safety, local health infrastructure, and parental anxiety.