LD50
LD50 of smoked and inhaled Cannabis or Marijuana: Unknown. At present it is estimated that marijuana's therapeutic index is around 1:20,000 or 1:40,000 (the "1" in the prior estimate is based on an "effective dose" of the .9 grams contained in NIDA-supplied marijuana cigarettes, although the potency of Cannabis changes based on the genetics of the source plant) placing its LD50 around at least 18,000g.