Tim Fitzmaurice tjf11 at cus.cam.ac.uk
Wed Mar 25 06:31:05 EST 1998

On 24 Mar 1998, Harmon wrote:

> Actually, there are ways to predict how people will react to drug doses.
> They are:
> ED50 - effective dose in 50% of test population
> LD50 - lethal dose in 50% of test population
> TD50 - toxic dose in 50% of test population
> TI - therapeutic index - measures drug safety, measured by LD50/ED50 or
> TD50/ED50.
But, these provide only an informed guess as to what will happen in an

ED50 shows this literally in its name, a single given dose is effective in
half the test subjects.....variability is required to get only 50%
responding at a given dose. This is an index not a prediction. 

That's how I saw the original point....the drug will work differently in
different people and so unexpected things certainly could happen. Not a
necessarily a nice conclusion, but an all too real one, IMHO, of course.

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