[user104658]

Originally Posted by ThomasC

No.

If the half life is 5 then it takes 5 hours for half of that remaining drug to be left in your body.

So after 10 hours that drug will no longer be in your system....

No, a halflife with meds is just the same principle as radiation halflife - it's the time it takes to half.

If the halflife is 5 hours, then after 5 hours there is 50% left, after 10 hours there is 25% left, after 15 hours there is 12.5% left, 20 hours 6.25%. ... etc.

It will take about 36 hours a drug with a 5 hour halflife probably won't be having any noticable effect on the body - it'll still be detectable in the bloodstream for over a week.

Interestingly this is why people on heroin are so ****ed up by it... it has a halflife of 5 minutes. So after 5 minutes the effect has dropped a lot, by half an hour after shooting up, the effect of the opiates is all but gone, and only shows in drug testing at all for 24-48h.

'tis also why most heroin addicts "supplement" with heavy Valium use. can have up to a 48hr half life so basically stays active for days, and detectable for weeks.