Seizure Disorders: Clonazepam is useful alone or as an adjunct in the treatment of the Lennox-Gastaut syndrome , akinetic and myoclonic seizures. In patients with absence seizures who have failed to respond to succinimides, clonazepam may be useful. In some studies, up to 30% of patients have shown a loss of anticonvulsant activity, often within 3 months of administration. In some cases, dosage adjustment may re-establish efficacy. Panic Disorder: Clonazepam is indicated for the treatment of panic disorder, with or without agoraphobia, as defined in DSM-V. Panic disorder is characterized by the occurrence of unexpected panic attacks and associated concern about having additional attacks, worry about the implications or consequences of the attacks, and/or a significant change in behavior related to the attacks. The efficacy of clonazepam was established in two 6- to 9-week trials in panic disorder patients whose diagnoses corresponded to the DSM-IIIR category of panic disorder. Panic disorder is characterized by recurrent unexpected panic attacks, i.e., a discrete period of intense fear or discomfort in which four of the following symptoms develop abruptly and reach a peak within 10 minutes: palpitations, pounding heart or accelerated heart rate; sweating; trembling or shaking; sensations of shortness of breath or smothering; feeling of choking; chest pain or discomfort; nausea or abdominal distress; feeling dizzy, unsteady, lightheaded or faint; derealization or depersonalization ; fear of losing control; fear of dying; paresthesias ; chills or hot flushes. The effectiveness of clonazepam in long-term use, that is, for more than 9 weeks, has not been systematically studied in controlled clinical trials. The physician who elects to use clonazepam for extended periods should periodically re-evaluate the long-term usefulness of the drug for the individual patient.