This is based on my own experience:
I've been on dilantin since 1979, I had a few itching spells and even tingling of the limbs. I thought it might be a reaction to the dilantin or low blood sugar or low blood pressure and circulation but my Doctor said it was DEHIDRATION. I increased my fluid intake and I was surprised ~ it went away. But everybody's body chemistry is different. (worked for me)
Diagnosed with epilepsy and ulcerative colitis in 1979,
Been on meds ever since.