Limited efficacy of zonisamide in the treatment of refractory infantile spasms.

A series of relatively small studies collectively suggest that zonisamide may be effective in the treatment of infantile spasms. Using a large single-center cohort of children with infantile spasms, we set out to evaluate the efficacy and safety of zonisamide. We retrospectively identified all patients with infantile spasms who were treated with zonisamide at our center. For each patient, we recorded dates of birth, infantile spasms onset, response (if any), and most recent follow-up. To quantify zonisamide exposure, we recorded daily dosage and patient weight at each sequential encounter so as to allow calculation of peak and weighted-average weight-based dosage. We identified 87 children who were treated with zonisamide, of whom 78 had previously been treated with hormonal therapy or vigabatrin. Peak and weighted-average zonisamide dosage were 7.1 (interquartile range 3.6, 10.2) and 5.4 (interquartile range 3.0, 8.9) mg/kg/day, respectively. Whereas five (6%) patients exhibited resolution of epileptic spasms, only two (2%) patients exhibited video-EEG confirmed resolution of both epileptic spasms and hypsarrhythmia (electroclinical response). Importantly, both electroclinical responders had not previously been treated with hormonal therapy or vigabatrin; in contrast, none of the 78 children with prior failure of hormonal therapy or vigabatrin subsequently responded to zonisamide. Zonisamide was well tolerated, and there were no deaths. This study suggests that zonisamide exhibits favorable tolerability but very limited efficacy among patients who do not respond to first-line therapy.
Competing Interests: Dr Hussain has received research support from the Epilepsy Therapy Project, the Milken Family Foundation, the Hughes Family Foundation, the Elsie and Isaac Fogelman Endowment, Eisai, Lundbeck, Insys, GW Pharma, UCB Biopharma, Zogenix, and the NIH (R34MH089299). He has received honoraria for service on the scientific advisory boards of Mallinckrodt, Upsher‐Smith Laboratories, Insys, UCB Biopharma, and Zogenix; as a consultant to UCB, Mallinckrodt, Insys, GW Pharma, West Therapeutic Development, Aquestive Therapeutics, Shennox, and Amzell; and on the speaker's bureau for Mallinckrodt and GW Pharmaceuticals. Dr Rajaraman has received research support from Marinus and the International CDKL5 Research Foundation. Dr Sankar serves on scientific advisory boards or serves on the speaker's bureau for and has received honoraria and funding for travel from Eisai, UCB Pharma, Sunovion, Supernus, Greenwich Biosciences, LivaNova, and on the advisory boards for Aquestive Therapeutics, West Therapeutic Development, Insys Development Company, and Zogenix; receives royalties from the publication of Pellock's Pediatric Neurology, 4th ed. (Demos Publishing, 20172008) and Epilepsy: Mechanisms, Models, and Translational Perspectives (CRC Press, 2011); serves on speakers’ bureaus for and has received speaker honoraria from Eisai, UCB, GlaxoSmithKline, LivaNova, Supernus, and BioMarin. He has received research support from SK Life Sciences and Insys Development Company, Inc The remaining authors report no conflicts of interest. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.
(© 2020 The Authors. Epilepsia Open published by Wiley Periodicals Inc. on behalf of International League Against Epilepsy.)