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.