Watch the body weight atleast 2-3 times a week!! I was on Z and Dilantin (with Kepp and TegXR) Zonegran did a number on me. I lost 25% body weight and Dilantin levels shot through the roof in less than 10 weeks. I couldn't even walk without a cane due to high dilantin levels caused by weight loss.
Z is KNOWN for weight loss.
First we thought it was the Zonegran being it was the new drug, so we halted ramping it for one week. That didn't work. Then dropped the dose; no help. So my Epileptologist did a rapid stop on the med (3 day total removal from Z). Effects remained longer than 5 days after stopping, so that was odd. That was when I went in for blood work and found out my Dilantin levels where sky high and discovered the weight loss problem in my case.
After dropping Dilantin 50mg for me that fixed the toxicity problem I was having with vision and balance. I regained my weight. Three months later we started Topa (cross removal of Dilantin to avoid problems) and it took a couple years to get it up to the dose I am now at (slight tinkering at the end with my suggestion) but I am currently satisfied with Topa.