Kavalactones

The styryl lactones of Piper methysticum — kavain, dihydrokavain, methysticin, yangonin, desmethoxyyangonin — and the root preparation containing them. The mechanism is plural and incompletely characterised: sodium and calcium channel blockade, GABA-A modulation at a site other than the benzodiazepine one, and monoamine oxidase B inhibition for some of the lactones. The sedation lacks the amnesia typical of the benzodiazepines, but it is still sedation and still adds to the rest of this subject.

What varies is the preparation. A traditional water extract of the root, a solvent extract, and a product standardised to a single lactone are three different exposures from one plant. Reports of liver injury are what led several countries to restrict kava, and the cause is still argued — extraction solvent, use of stems and leaves rather than root, existing liver disease, interacting medicines. Kava also inhibits CYP enzymes, raising blood levels of other drugs taken with it.