A small percentage of people who take ethosuximide experience serious reactions. Alert patients to call immediately if they notice any of the following symptoms:

• Rash
• Sore throat, fever, sores in the mouth, or easy bruising (blood dyscrasias)
• Fever, rash, arthritis, swelling in the lymph nodes (systemic lupus erythematosus or lupuslike syndrome)
• Depression, anxiety, or aggressiveness
• Hallucinations, hearing "voices" or losing contact with reality (psychosis)

As with many seizure medicines, skin rashes (including the very rare Stevens-Johnson syndrome, which can be fatal) have been a problem for a small number of patients. Most rashes are much less serious and will disappear if ethosuximide is withdrawn.

Similarly, Zarontin carries a very small risk of blood abnormalities. Checking the blood cell count within 2 to 12 weeks after the Zarontin is started and every 4 to 12 months after that is often recommended, but reminding patients to report symptoms promptly is probably more effective in early recognition of blood disorders.

One effect that has been studied extensively is an allergic reaction to Zarontin that might bring about some of the symptoms and blood test results found in systemic lupus erythematosus (SLE). Sometimes patients with these symptoms have a lupuslike syndrome from which they fully recover when ethosuximide is stopped, though recovery may take some time.

Behavioral changes occasionally occur shortly after patients start taking Zarontin. Hallucinations, paranoia, and other signs of psychosis have been reported in a few patients, mostly adolescents or young adults with a history of previous emotional problems or psychiatric disease. These problems may be more likely if high doses are given.

Tests of liver and kidney function are also recommended. Zarontin should be given to patients with liver or kidney disease only with extreme caution.

A complete list of all reactions to Zarontin can be found in the package insert.

On July 10, 2008, an advisory panel was convened by the Food and Drug Administration (FDA) to review data that the FDA had previously collected from drug studies showing an association between many of the antiepileptic drugs (AEDs) and suicidal ideation and behavior, which together are called suicidality. According to the FDA’s Alert, among the patients with epilepsy in these drug studies, 1 out of 1000 people taking the placebo (inactive substance) showed suicidality compared to approximately 3.5 out of 1000 people who took an AED. The FDA advisory panel voted to accept the FDA's data at its meeting on July 10. The FDA has provided the following information for patients, family members, and caregivers at www.fda.gov/cder/drug/InfoSheets/HCP/antiepilepticsHCP.htm.

• Taking antiepileptic medicines may increase the risk of having suicidal thoughts or actions;
• Do not make any changes to the medication regimen without first talking with the responsible healthcare professional;
• Pay close attention to any day-to-day changes in mood, behavior and actions. These changes can happen very quickly so it is important to be mindful of any sudden differences.
• Be aware of common warning signs that might be a signal for risk of suicide. Some of these are:
  • Talking or thinking about wanting to hurt yourself or end your life
  • Withdrawing from friends and family
  • Becoming depressed or having your depression get worse
  • Becoming preoccupied with death and dying
  • Giving away prized possessions

We again urge patients and families to contact their doctor before stopping an epilepsy medication because this may possibly lead to seizures and worsening of mood.

Reviewed July 2008 by Steven C. Schachter, MD, epilepsy.com Editorial Board.