Potentially serious or life-threatening reactions to clonazepam are rare. Symptoms that patients should report immediately to their doctor include:

Most patients who take clonazepam have no side effects or mild, transient side effects. Rarely, patients may develop any of the following serious side effects:

• An allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, face, or tongue; or hives)
• Sores in the mouth or throat (could mean a blood problem)
• Yellowing of the skin or eyes
• Rash
• Hallucinations, severe confusion, or changes in vision

Clonazepam, like other benzodiazepines, may cause psychological dependence. Withdrawal symptoms may occur if a dose is missed or reduced, including:

• anxiety
• increased heart rate
• tremor
• general unwell feeling

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.