Zarontin/ethosuximide

Hello, my sister was recently diagnosed with absence seizures, absence epilepsy. And she is currently on zarontin/ethosuximide. Now the medication does work now that she's on her full dosage. She's had only two episodes. But the side effects I'm not sure if it's caused by the meds or if there is something else going on. I have done tons of research on this medication because my sister has been having tons of side effects. Now it is supposed to cause drowsiness that is the only thing her neurologist told us about. She shouldn't feel anything else. But I've read that it causes nausea, hiccups, sleepiness, dizziness, and the more severe include rashes, joint pain, swelling, pain when breathing. And my sister has had those side effects, I've brought them to her neurologist attention and she tells me she has no clue as to what could be causing it. BeCause the medication should not be. That there's probably something else going on. And I've told the doctor that, that's what I read. Swelling, rashes, joint pain. It has to be the medication. But they insist they have no idea. And I'm not sure what to do because the medicine is working, but the rashes are slowly becoming worse. At first we thought they were heat rashes because it was extremely hot. But it's almost winter. I need advice...