Side effects of ethosuximide? Is much nausea one of the side effects?

It can be. Side effects of Ethosuximide can include dizziness, headache, sleepiness, decreased appetite, diarrhea, GI upset, nausea, vomiting, balance problems, confusion, altered sleep, itch, enlarged gums, hiccups, tongue swelling, change in blood count, allergic reaction, vision changes, & even psychosis, seizure, lupus, suicidal thoughts and behavior, or severe rash.