Several rhizome components and lactones have been isolated in the kava root. All kavalactones are physiologically active, though it is the fat-soluble kavalactones derived from kava resin that have the greatest effect on the central nervous system. Kava also has a direct effect on muscle tension similar to tranquilizers. The activity of the kava rhizome is related to several arylethylene pyrones similar in structure to myristicin, which is found in nutmeg. Kava is mildly narcotic and produces mild euphoric changes characterized by elevated mood, fluent and lively speech and increased sense of sound.
Higher doses can lead to muscle weakness, visual impairment, dizziness and drying of the skin.
Long term use of the herb can contribute to hypertension, reduced protein levels, blood cell abnormalities, or liver damage. Alcohol consumption increases the toxicity of the pharmacological constituents. It is not recommended for those who intend on driving or where quick reaction time is required. Kava is the most relaxing botanical herb with exception of the opium poppy. Pharmacological studies show kava kava's active ingredients, kavalactones, produce physical and mental relaxation and a feeling of well being.