Some of the common side effects :
Trouble w/ concentration
moods or mental changes
Shakiness in Walking Balance
Tiredness
Lose of interest or pleasure
Trouble sleeping
Irritable
Lack of appetite
Feeling sad or empty
Discouraged
Abnormal stomach pain
Anxiety
Dizziness
Memory
Double vision

Uncommon side effects :
Rash
Agitation
Bruising
Delusional
Hallucination

Im on zonisamide and so is my husband and we both struggle with memory loss but it definitely helps with our seizures, i have severe osteoporosis of the spine and have broken numerous vertebraes in my spine and due to zonisamide ive gone 6 months without a tonic clonic seizure so for me its a miracle x

There is a whole Wikipedia article on the drug, i know they aren't always the most detailed site but has a lot of info there

I take Zonisamide. Keeps My weight down too! As far as memory loss, it could be from the Vimpat I take.

I take this drug too, and i have to have a certain dose because as i was getting increasing it was bringing on many bad side effects. I was depressed, tired, no sleep, pain etc. So i had to go back down but that wasnt working because it was bringing on more seizures. I was stuck in the middle for a while.