Ethosuximide causing stomach sickness

I have a daughter, she is 7 years old, she has epilepsy, ( I have to wait on Feb 8 they will do to her an MRI & EEG
she is taking ETHOSUXIMIDE at the moment. but she’s always sick i have to pick her up fron school because she has a stomach upset, vomiting. for how long this side effects will dissapear. she is taking this medicine since Dec 29.

please answer me ASAP

THANKS

MARYURI PUERTA