Most people who take zonisamide don't report any side effects. The others most often complain of:

• sleepiness or fatigue
• dizziness
• loss of appetite (it's not unusual to lose several pounds)
• upset stomach
• headache
• agitation or irritability

Most of these problems are mild to moderate.

During scientific studies in which some people took zonisamide in addition to their regular seizure medicine, and some people took an inactive substitute (a placebo) instead of zonisamide only 17% of the patients taking zonisamide reported a problem with sleepiness (as did 7% of those taking the placebo). The other side effects were even less common. So you can see that side effects are not a problem for most people. You should be careful when you first start taking zonisamide, though, and make sure you don't have a problem with sleepiness when driving or doing anything else that might be dangerous.

Some other side effects mentioned even less often were:

• poor coordination or tremor
• speech problems
• poor concentration
• itching
• vision problems

If you notice problems like any of these while you are taking zonisamide, it's probably a good idea to discuss them with your doctor or nurse. Sometimes the doctor can help with these side effects by changing the prescription:

• reducing the overall dose
• changing the amount taken at certain times, such as taking a greater proportion at bedtime to reduce daytime sleepiness
• prescribing smaller doses, to be taken more often You shouldn't stop taking zonisamide or any other seizure medication without your doctor's advice.

Be sure to read about the serious side effects so you will be aware of symptoms that might indicate the beginning of a dangerous reaction to zonisamide. These serious problems are very rare but everyone who takes this medicine should at least be aware of them.

People who have just started taking zonisamide (or who have just started taking a larger amount) should be careful during activities that might be dangerous, until they know whether they are having any side effects.

Allergic reactions
Approximately 1 in 20 people who take zonisamide have a red rash within the first few weeks of taking it. If this happens, tell the doctor or nurse right away, to be sure that it's not the beginning of a serious problem. It's rare for the rash to be serious, but don't ignore it. It's often necessary to switch to a different seizure medicine.