Clonazepam, sold under the brand Klonopin among others, is a medication used to prevent and treat seizures, panic disorder, anxiety, and the movement disorder known as akathisia. It is a tranquilizer of the benzodiazepine class. It is taken by mouth. Effects begin within one hour and last between six and twelve hours.Common side effects include sleepiness, poor coordination, and agitation. Long-term use may result in tolerance, dependence, and withdrawal symptoms if stopped abruptly. Dependence occurs in one-third of people who take clonazepam for longer than four weeks. There is an increased risk of suicide, particularly in people who are already depressed. If used during pregnancy it may result in harm to the fetus. Clonazepam binds to GABAA receptors, thus increasing the effect of the chief inhibitory neurotransmitter γ-aminobutyric acid (GABA).Clonazepam was patented in 1960 and went on sale in 1975 in the United States from Roche. It is available as a generic medication.