Original post · Thu, January 17, 2013 · Ceretropic
Allometric Scaling of Doses Between Species
u/MisterYouAreSoDumb · Ceretropic
I am making this post because I constantly see people making comments that certain substances were given in much higher doses to animals than would be normally ingested by humans. Sometimes that is the case, due to a study's goal of ensuring that certain toxicities can be observed. However, the dosages are NEVER directly related to humans. You cannot take a study that gave 100mg/kg of a substance to rats, then quote it as if we are talking about human equivalents. Rats metabolisms are different, just like mice, dogs, rhesus monkeys, etc. There are also other things to take into consideration, like differences in CYP450 enzymes, or lower hormone/antioxidant levels. Usually those irregularities will be discussed in the study if they are of consequence to the findings. There will always be allometric scaling of dosages between species.
Here are a few general conversions:
D = Animal Dose
H = Human Dose
D*K/37 = H
* Mice- D*3/37 = H
* Rats- D*6/37 = H (K value for rats will range from 6 to 7)
__________________________________________
Given that, a 100mg/kg dose given to a rat would be a 16mg/kg dose given to a human. This changes the dose from 8,100mg dose for my body weight, to a 1,300mg dose. That is a HUGE difference! Other larger animals weights are going to vary a lot, so the guidelines are not as accurate. Usually a study using animals of that size will mention an estimated human equivalent dose. Please think about this when people are saying that a study should be written off because the doses were so high.