Took 11 grams standardized Kavalactones, it is most definitely effective
Mind you, I know it is only from the root, and not the stems or leaves, which are what actually cause the liver damage that has been documented! Important little detail, that.
Further dosage info on Kava Kava(Piper Methysticum G. Forster):
1 tsp cup/night ; 1.5–3 g dry root/day ; 100–300 mg root several/day; 2–4 g powdered root 1–3/day; 2–4 ml liquid root extract;
3–6 ml fluid extract (1:2)/day; 1–3 ml tincture/day; 60–600 mg kavalactones/day
250 ml kavalactones/day (24–70 mg 3/day) ; 180–210 kavalactones 1 hour
before bedtime; 1 (525 mg) capsule (StX with 250 mg certified potency kava-kava root
extract with at least 75 mg kavalactone) 3/day.
Toxicity info:
LD50 dihydrokavain = 920 mg/kg orl mouse, LD50 dihydromethysticin = 1050 mg/kg orl mouse, LD50 StX (70% kavalactones) = 16,000
mg/kg orl rat, 1800 mg/kg orl mouse, 370 mg/kg ipr rat, 380 mg/kg ipr mouse.