Posted by Meri-Tuuli on May 13, 2006, at 7:21:53
In reply to What does half-life really mean?, posted by flip_flop on May 13, 2006, at 1:51:10
Hi!
> Let's say I take 100 mg of some drug that has a half-life of 6 hours. Does this mean that after 6 hours, 50 mg of the drug is still active?
Yes. Half the drug would have been converted/metabolised by your body, and the other half still there.
>This drug would need to be taken at least 2 times/day, but why couldn't I just take twice the dosage only once/day?
With drugs that have a short half life, then they will enter your bloodstream (and therefore be used) quickly. Then the level will fall as your body is using up the med. Thing is, you need the twice (or whatever) daily dosing to try and keep the levels stable-ish in your bloodstream, so you don't get big peaks (too much medication) and big troughs (too little). This might cause unwanted side effects, and make you not feel very well for instance. So you need to spead the dosage out during the day.
If the med has a long half life (like prozac for instance) then once daily dosing is fine.
poster:Meri-Tuuli
thread:643354
URL: http://www.dr-bob.org/babble/20060510/msgs/643384.html