Most people who take Mysoline (primidone) have no side effects or mild side effects that go away with no lasting harm, but a very small number of people have serious reactions. Here's a list of symptoms that may be the start of one of these problems. If you notice any of these symptoms, call your doctor right away:

• An allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives)
• Fever, swollen glands, sore throat, or sores in the mouth (could mean a blood problem)
• Red or purple point-like rash or blistering or peeling skin lesions
• Easy bruising, paleness, weakness, or fatigue
• Worsening of seizures

It's not unusual for Mysoline to make people feel sleepy or uncoordinated. If you've just started taking Mysoline or have just increased your dosage (especially if you tend to be sensitive to medications), be careful when doing things that could be dangerous until you know how it will affect you.

People who are taking Mysoline should avoid drinking alcohol because this combination can cause deep sedation or sleepiness.

A complete list of all reactions to Mysoline can be found in the package insert, but it is important to remember that most people who take it have none of these serious problems.

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.