Melatonin is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae.[1] The use of melatonin as a drug can entrain (synchronize) the circadian clock to environmental cycles and can have beneficial effects for treatment of certain insomnias. Its therapeutic potential may be limited by its short biological half-life, poor bioavailability, and the fact that it has numerous non-specific actions.[6] In recent studies though, prolonged release melatonin has shown good results in treating insomnia.[7]