Re: MAPS: question: ed50 & LD50

["Nicholas V. Cozzi, Ph.D." <nvcozzi@xxxxxxxxxxxxxxxx>]

At 02:57 PM 3/5/99 -0500, you wrote:

>Someone correct me if i am wrong (again i am not a chemist)  but those two
>numbers are taken together to form a ratio, meaning that if the ED50 of
>something is 5 grams, and the LD50 of something is 50 grams, is 5:50, or
>1:10.

Actually, the *therapeutic index* you are describing is usually taken as
the toxic dose 1 divided by the effective dose 99; TD1/ED99.  If a drug
causes toxicity in one percent of the subjects at 10 grams and is effective
in 99 percent of subjects at 1 gram, the TI is 10.  The higher the TI, the
better.  One of the lowest known TI's is for digitalis compounds, around 2.

Nick

Nicholas V. Cozzi, Ph.D.
Department of Pharmacology
East Carolina University School of Medicine
Greenville, NC  27858

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