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[Reformed-Redan]

I just wanted to bump this thread It seems like a lot of people here are using this allometric scaling calculator these days. I think it's worth noting that "allometric scaling" does not denote a single practice: allometry is the study of the relation of body size to overall shape, and in this context, how to scale dosages between different organisms.

This calculator uses average body mass, absolute dose, and an exponent to compute the human equivalent dose. This article explains the reasoning for the exponent; it strikes me as a kind of unified theory of biological scaling, whose aims are far beyond the scope of clinical application we discuss here.

I'd like to suggest that people start using the method described in this thread, instead. This type of allometric scaling employs body surface area (BSA) in addition to average weight, which research has shown to be more accurate than body weight in scaling lethal dose and maximum tolerated dose, along with basal metabolism, caloric expenditure, oxygen utilization, blood volume, circulating plasma proteins, and renal function. I think this is preferable to using one curve which has been fit to single-celled organisms and elephants, however close it may sometimes be (seems to be better for some animals than for others).

There are still severe limitations to this method: the scaling does not predict plasma concentration of drugs as neatly, and does not take into account differences in first-pass metabolism and drug clearance (probably among other things). So it really only gets us in the ballpark, but I think BSA gives us a better starting point.

It's especially handy since it doesn't involve exponents and average weights, and is very easy. Here's some very quick shortcuts for calculating absolute dose for a 70kg human from the mg/kg dose in common lab animals based on BSA:

• (mouse mg/kg dose) x 5.675 = 70kg human dose
• (rat mg/kg dose) x 11.35 = 70kg human dose
• (rabbit/monkey mg/kg dose) x 22.7 = 70kg human dose
• (dog/baboon mg/kg dose) x 37.83 = 70kg human dose
• (child human mg/kg dose) x 47.3 = 70kg human dose

I'll stress again that these shortcut numbers are used to go from mg/kg to an absolute adult human dose; they increase toward 70, which would be the factor to use for an adult human mg/kg dose.


Here's the handy tables from the paper:

Can a moderator pin this? Thanks. Quoted from chrono's post here.