||This question was answered in relationship to the research by the Griffiths group at Johns Hopkins administering psilocybin to humans. See Psilocybin, Science, and Sacrament.|
Psilocybin is converted after ingestion into psilocin, the chemical active in
the brain. Most Psilocybe mushrooms contain a mix of psilocybin, psilocin, and
baeocystin. While published data about the psilocybin/psilocin content of mushroom
species is somewhat sparse, estimates are that normally potency Psilocybe cubensis
(the most common psychoactive mushroom available in the United States) contain
around 0.5–1.0% total psilocybin + psilocin, by dry weight.
The Griffiths study administered oral psilocybin at 30 mg per 70 kg body weight.
This is 0.43 mg/kg or 0.20 mg/lb. For someone weighing 70 kg (154 lbs), this is the
approximate equivalent of 4–6 dry grams of Psilocybe cubensis mushrooms.
Potency in wild species can vary by up to 1000%, but in commonly available
dried mushrooms this variation is likely closer to ±50%. Very strong P. cubensis
may contain 30 mg psilocybin in 2.5 dry grams and weak mushrooms may only
contain 30 mg in 8 grams.
- Trout K. Some Simple Tryptamines. Mydriatic Productions. 2002. pg 73–74.
- Gartz J. “Extraction and analysis of indole derivatives from fungal biomass.” Journal
of Basic Microbiology. 1994;34 :17–22