Posted by omegon on October 4, 2003, at 6:01:48
In reply to Re: Half-life, posted by krybrahaha on October 4, 2003, at 0:57:51
No, 20 hours for _half_ the dose to leave your system. Then a further 20 hours for half the remainder, leaving you with a quarter of the original dose; and so on. Obviously it's a gradual, smooth curve, and it decreases more slowly as the level remaining gets lower. It results from continuous breakdown and excretion of the drug - it doesn't drop in steps every 20 hours!
What this means is that drugs with a short half-life need to be taken more frequently, or in slow-release formulations, in order to get a reasonably smooth, continuous effect; you want to avoid a dramatic drop in levels by the time you take the next dose. An exception to this might be if you actually want the levels to be lower at some time of day; for example, if it causes insomnia, it might be helpful to take it in the morning and let the level fall a bit by bedtime.
Since a drug with a short half-life will leave your system completely only a few days after you stop taking it, it may be more likely to cause withdrawal problems if you stop abruptly.
> Half Life is the amount of time it takes for just half the drug to leave your system. You say that Wellbutrin has a 20 hr half life, it will take 10 hrs just for half of whatever dose your on to leave your system.
poster:omegon
thread:265408
URL: http://www.dr-bob.org/babble/20031004/msgs/265457.html