When it was tested as an add-on treatment for epilepsy before its FDA approval, only 15% of the people taking immediate release Keppra stopped taking it or lowered their dosage because of side effects. Almost 12% of people taking an inactive placebo did the same, so the difference was quite small. More recent studies have shown similar results and Keppra continues to have an excellent safety profile.

The side effects that were reported more frequently with Keppra than with placebo during the early testing were:

• sleepiness
• loss of strength and energy (asthenia)
• dizziness
• infection

These occurred mostly during the first 4 weeks of treatment. The infections were mainly colds (upper respiratory infections) and infection has not been a problem during recent experience with large numbers of people.

Other side effects mentioned less often or reported more recently have included:

• agitation
• anxiety
• nervousness
• irritability
• other mood changes
• coordination difficulties
• headache
• psychosis (rare)

Some doctors have observed behavioral problems more frequently in children than in adults.

If you notice any of these side effects while you are taking Keppra XR, it's probably a good idea to discuss them with your doctor or nurse. Sometimes the doctor can help by changing the amount of Keppra XR or the way you take it. Don't stop taking Keppra XR or any other seizure medication without your doctor's advice.

It's not too unusual for Keppra XR to make people feel sleepy, dizzy, or uncoordinated. If you have just started taking Keppra XR (or have just started taking a larger amount), be careful during activities that might be dangerous (like driving or operating machinery), until you know whether you are having any of these side effects.

Be sure to read about the serious side effects of Keppra XR. These serious problems are very rare but everyone who takes this medicine should be aware of them.

Allergic reactions
There are no known allergic reactions to Keppra XR.

Long-term side effects
The long-term side effects of Keppra XR are not yet known.