Toxicity of Cannabis
There has never been a documented human fatality from overdosing on tetrahydrocannabinol or cannabis in its natural form. However, the synthetic THC pill Marinol was cited by the FDA as being
responsible for 4 of the 11,687 deaths from 17 different FDA approved
drugs between January 1, 1997 to June 30, 2005.Information about THC's toxicity
is derived from animal studies. The toxicity depends on the route of
administration and the laboratory animal. Absorption is limited by serum lipids, which can become saturated with THC, mitigating toxicity. According to the Merck Index, 12th edition, THC has an LD50 (dose killing half of the research subjects) value of 1270 mg/kg (male rats) and 730 mg/kg (female rats) administered orally dissolved in sesame oil The LD50 value for rats by inhalation of THC is 42 mg/kg of body weight. One estimate of THC's LD50 for humans indicates that about 1,500 pounds (680 kg) of cannabis would have to be smoked within 14 minutes.
This estimate is supported by studies which indicate that the effective
dose of THC is at least 1000 times lower than the estimated lethal dose
(a "therapeutic ratio" of 1000:1). This is much higher than alcohol (therapeutic ratio 10:1), cocaine (15:1), or heroin (6:1)