There are many different kinds of anti-epileptic medicines on the market. These drugs work best only after they reach what experts call a desired level in the body. It might take months to identify the right drug to control the disorder because each one may cause side effects. These include weight gain or loss, eye or stomach problems, sleepiness and loss of balance. Some people may suffer depression, or have problems thinking or talking after taking some drugs. And the WHO says anti-epileptic drugs work only 70 percent of the time.