IUBio

determination of LD50 with rats

Tom McCloud McCloud at dtpax2.ncifcrf.gov
Mon Sep 8 16:38:25 EST 1997


DUFRASNE FRANCOIS wrote:
> 
> I'm a student in pharmacy and I need this information:
> WHAT'S THE PROTOCOL TO DETERMINE THE LD50 WITH RATS (100 rats for example)?
> Please, if somebody has a precise answer, send me it on my E-mail:
> DUFRASNE at RESULB.ULB.AC.BE.
> I need a an answer for tuesday 9th september later!!!!!


The definition for Lethal Dose at a 50% response level would be the
amount of compound required to kill 50% of the test organisms.  So if
you have 100 rats, and you inject
x milligrams into all 100 of them and 50 of them die, then x mg is the
ED50.   Now lets think about this:   if I inject a high dose into all
100 and all 100 die, then I don't know the ED50.  And if I inject a very
small dose into all 100 and none die, then I don't know the ED50.    So
what sort of an experimental protocol could I propose that
would allow me to calculate an ED50????           Tom McCloud



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