Comparisons of the psychoactive effect of Kava to alcohol intoxication fall short for a couple of reasons. The subjective effects from Kava are more pacifying and introspective than ethanol. It's well known that people intoxicated by alcohol can become hostile, or even violent due to lowered inhibitions. This is unheard of with Kava. In fact, as more Kava is consumed over time, any possible feeling of hostility or anger that may have been present before consumption will disappear almost entirely.
The botanical name of the Kava Kava shrub is piper methysticum, piper = Latin "pepper", and methysticum = Latinized Greek for "intoxicating." Thus Kava Kava belongs to the genus of plants that include the common black pepper plant, piper nigrum.
In areas of the Pacific the drinking of Kava Kava is a highly ritualized and social affair. Story telling is common, as some of the initial effects of Kava intoxication include an increase in loquaciousness. In some Islands of the South Pacific, such as Fiji, many ceremonies or functions, both private and public, cannot be properly consummated without the ritualized drinking of Kava Kava.
Over a period of hours, depending upon how much is consumed, this initial loquaciousness transforms into a more somnolent state, sometimes resulting in an almost irresistible urge to sleep. The sleep is known to be deep and rejuvenating, often replete with very vidid dream imagery.
The psychoactive constituents of Kava Kava are a family of phytochemicals known collectively as kavalactones. Although there are many kavalactones in Kava, there are six principal kavalactones that are thought to be behind most of the effects. Unlike many other psychoactive compounds, kavalactones are not alkaloids, that is, the kavalactone molecules don't contain a nitrogen atom. Rather, they are classified as lactones.
Desmethoxyyangonin (in the image below) is thought to boost dopamine levels in the brain, resulting in the more euphoric effects. It's also a muscle relaxant. Kava also has local anesthetic effects, thought to be a result of Kavain. Dihydrokavain is thought to be responsible for the anti anxiety, or anxiolytic effects.
There are many different chemotypes of Kava Kava. The relative proportions of kavalactones in different rootstock from different geographical areas can result in perceptibly different effect profiles. Thus, certain Kavas can result in deep muscle relaxation without overmuch euphoric effects, and others, primarily those with a higher Kavain content, can result in a more euphoric, initially stimulating effect.