Kathy says,


> The half-life rule of 5 comes from the fact that only about 3% of a
> substance will be left after 5 half-lives.  A half-life refers to the time
> it takes for 50% of the original to disappear.  So if you start with 100%,
> then after one half-life you have 50%, after two half-lives you have 25%,
> after three you have 12.5%, after four you have 6.25% and after five you
> have 3.125%.  If you wait one more half-life (for good measure) then you
> have less than 2% of the original amount.  That amount is assumed to be
> insignificant in terms of causing problems for the baby.
>
I think this was done primarily in reference to radiopharmaceuticals, though
obviously it works for other drugs as well.

Jan in Wheaton -- the barbeque is finally on the grill!

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