Posted by fachad on April 5, 2002, at 15:51:45
In reply to FACHAD: you forgot my second question, here it is: » fachad, posted by Janelle on April 5, 2002, at 14:56:44
Janelle,
Your second question turns on your definition of "gone".
Take another look at my earlier post
http://www.dr-bob.org/babble/20020402/msgs/101982.html
In your question, you are assuming that less than 1 mg/l is "gone".
But remember that gone is a *relative* term, meaning that there is no longer a significant amount in the system, not an *absolute* term, meaning that there is absolutely none of it present at all.
For example, 1mg/l, what you were assuming meant "gone" could also be written as 1,000 mcg/l (micrograms per liter). You could watch it go from 1000 mcg/l to 500 mcg/l, and then from 250 mcg/l to 125 etc. At 1 mcg/l you are now at 1000 ng/l (nanograms per liter) and so on forever. If you have sensitive enough equipment, you could continue to measure decreasing concentrations long beyond when the drug was exerting any effects or causing any problems.
So, no matter what your starting concentration is, after 5 half-lives you are at 1/32 of where you started, which is *effectively* gone, no matter what the actual number is.
Hope this doesn’t' confuse you more.
poster:fachad
thread:101843
URL: http://www.dr-bob.org/babble/20020402/msgs/102016.html