>  The phrase "...throw in another for good measure" is a fundamental
>concept that turns scientifically based recommendations into advice.

Ooh, good point, Nikki, thank you for catching that.

>    Now, another question. I have used the  five half-lives rule because I
>have learned it from physicians. Does anyone know where the evidence for it
>comes from?

As I understand it, after 1 half-life, 50% of the drug remains.  After 2,
25%.  After 3, 12.5%, after 4, 6.25%.  And after 5, only 3.125% remains, so
the blood (and milk) should be 97% drug-free.  But why do we choose that
instead of 93.75% drug-free at 4 half-lives?  Or 87.5% drug-free at 3?
We're talking about a continuum of extremely low amounts anyway.  We
probably should be tailoring the number of half-lives we wait to the level
of concern we have about the drug; barring that kind of expertise, "5
half-lives" is probably amply cautious for them all.

But people tend to be especially squeamish about chemo meds, so when I argue
on behalf of continuing to nurse through chemo, I've tended to offer an
*extra extra caution* option.  Wait 6 half-lives and you're 98.4% drug-free.
 Wait 7 and you're 99.2% drug-free and how could *anyone* object?  So my
unscientific point was, be cautious, be extra-extra cautious if you like,
and you *still* won't have to suspend nursing for very long.

Frank Nice or others, any comments?

Diane Wiessinger, MS, IBCLC  Ithaca, NY
www.wiessinger.baka.com

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