Animal THC Lethality Findings Depended on Route and Preparation
An animal lethality value belongs to the species, preparation and administration route tested. A historical cannabis chapter described markedly different acute-toxicity findings across routes, which prevents treating one number as a universal human toxicity threshold.
The chapter compared different experiments
Nahas discussed crude cannabis extracts and purified THC administered to animals by oral, injected and other routes. The reported amounts and timing of toxic effects differed.
These were experimental animal observations. They did not establish a measured lethal concentration for humans or a conversion from a smoked product to an injected laboratory dose.
Route changes exposure before the endpoint is measured
An administered amount is not identical to the amount reaching circulation. Absorption and its timing can differ across routes, and an extract contains more than a single cannabinoid.
An LD50 is also a group endpoint: the dose associated with death in half of an experimentally defined group. It is not a boundary below which every subject is safe or a direct measure of nonfatal functional effects.
Avoid numerical transfers the evidence cannot support
Scaling an animal value by a person’s body weight does not reproduce the original experiment. A clinical inference would require appropriate information about species differences, exposure and the outcome being considered.
The historical findings can illustrate route-dependent toxicology without establishing a modern human safety margin. Low lethality in one experiment also cannot answer separate questions about impairment, injury or chronic exposure.
Related: Different endpoints in animal cannabis toxicology.
Research cited
Gabriel G. Nahas. Marihuana: Toxicity and Tolerance. Historical book chapter, pp. 16–36.
