Re:An Experience with Modafinil
by actually_a_dog on Tuesday January 25, 2022 @08:34AM
(#30071591)
While it’s true that if the LD50 is 200mg/kg, you’d expect roughly 50% of humans weighing about 100kg to die from it, I kind of suspect it doesn’t quite work that way. Dose/response relationships are frequently logarithmic, which means that after a certain point, you have to increase the dose by a lot to get just a little more effect.
Also, LD50 values are always extrapolated from single dose tests on lab animals, typically rats or mice. Not only is that not how a human would end up ingesting 10+ grams of caffeine, the LD50 varies considerably from one animal to the next.
For instance:
> [S]ome LD50s for dichlorvos, an insecticide commonly used in household pesticide strips, are listed below:[0]
> Oral LD50 (rat): 56 mg/kg
> Oral LD50 (rabbit) 10 mg/kg
> Oral LD50 (pigeon:): 23.7 mg/kg
> Oral LD50 (rat): 56 mg/kg
> Oral (mouse): 61 mg/kg
> Oral (dog): 100 mg/kg
> Oral (pig): 157 mg/kg
As you can see, these numbers don’t seem to scale up in any intuitive way when you start crossing animal species.
Also, LD50 values are always extrapolated from single dose tests on lab animals, typically rats or mice. Not only is that not how a human would end up ingesting 10+ grams of caffeine, the LD50 varies considerably from one animal to the next.
For instance:
> [S]ome LD50s for dichlorvos, an insecticide commonly used in household pesticide strips, are listed below:[0]
> Oral LD50 (rat): 56 mg/kg
> Oral LD50 (rabbit) 10 mg/kg
> Oral LD50 (pigeon:): 23.7 mg/kg
> Oral LD50 (rat): 56 mg/kg
> Oral (mouse): 61 mg/kg
> Oral (dog): 100 mg/kg
> Oral (pig): 157 mg/kg
As you can see, these numbers don’t seem to scale up in any intuitive way when you start crossing animal species.
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[0]: https://www.ccohs.ca/oshanswers/chemicals/ld50.html