When it was tested as an add-on treatment for epilepsy before its FDA approval, only 15% of the people taking 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 has now been used by at least 100,000 people. It 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, 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 or the way you take it. Don't stop taking Keppra or any other seizure medication without your doctor's advice.

Some people have reported beneficial effects from Keppra, such as improved thinking or concentration and increased alertness. There is no definite evidence that Keppra improves these functions, however. Some people notice improvements of this kind if their seizures are substantially decreased in frequency or severity, whether by Keppra or some other seizure medicine.

It's not too unusual for Keppra to make people feel sleepy, dizzy, or uncoordinated. If you have just started taking Keppra (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. 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. Long-term side effects The long-term side effects of Keppra are not yet known.