Question about a half life amount of time for withdrawal from a medication....?

Question

What does it mean when someone tells you it takes seven half lives to withdraw from a medication... such as cymbalta... having stopped it two weeks ago.

thanks!

Answer 1

Half life in this case is the amount of time it takes for half the medication you have ingested to be excreted or otherwise metabolised to an inactive form.  So 7 of these is when you have 1/128 of the original drug left in your body.  Time wise it is just 7 x the half life, but the half life changes for different drugs.

Answer 2

I just looked it up... cymbalta has a half life of 12 hours

this means that... say you just took a capsule

you will have 100% of that drug in your body

after 1 half life you will have half that drug in your body .... or 50% and it takes 12 hours for this to occur

after 2 half lifes... you will have 25% of the drug left and 24 hours has gone by

if you keep diving the percentage by 2 (or halfing) and keep adding 12 hours to the half life you will eventually get that...

In order to withdraw from this medicine... if indeed it takes 7 half lifes, then that means:

After 7 half lifes ... 0.78125% of the drug will be left in your body and it will take 84 hours (or 3.5 days) for this to occur

hope this helps