Clonazepam, sold under the brand name Klonopin among others, is a medication used to prevent and treat seizures, panic disorder, and for the movement disorder known as akathisia. It is a tranquilizer of the benzodiazepine class. It is taken by mouth. It begins having an effect within an hour and lasts between 6 and 12 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. It may increase risk of suicide in people who are depressed. If used during pregnancy it may result in harm to the baby. Clonazepam binds to GABAA receptors and increases the effect of the chief inhibitory neurotransmitter gamma-aminobutyric acid (GABA).
Clonazepam was initially patented in 1964 and went on sale in 1975 in the United States from Roche. It is available as a generic medication. The wholesale cost in the developing world is between US$0.01 and US$0.07 per pill. In the United States, the pills are about US$0.40 each. In 2016 it was the 42nd most prescribed medication in the United States with more than 18 million prescriptions. In many areas of the world it is commonly used as a recreational drug.