Klonopin (clonazepam) is a benzodiazepine. Clonazepam affects chemicals in the brain that may be unbalanced. Clonazepam is also a seizure medicine, also called an anti-epileptic drug. Klonopin is used to treat certain seizure disorders (including absence seizures or Lennox-Gastaut syndrome) in adults and children. Klonopin is also used to treat panic disorder (including agoraphobia) in adults. Klonopin may also be used for purposes not listed in this medication guide.