Re: Half Life??????
Actually, that is not quite correct. The half-life is the time that it takes for the blood level of a drug to drop by one half (hence the name.) Now, there does come a point where this no longer holds true; ie, if the half-life of a drug is 16 hours, the blood level will be 1/2 of its initial level after 16 hours; after 32 hours it will be 1/4, etc. BUT if this continued indefinately, the drug would never clear completely from the body, so sooner or later the blood level is such that in another "half-life" the drug will have cleared completely.
Also, though you can get a lot of information about what the half-life of a given drug is, keep in mind that this is an average; clearance rates depend a lot on the body's ability to metabolize said drug. If your ability to clear drugs from your system is not in some way compromised (eg, liver or kidney damage), the longer you have been using a given drug, the faster your body will metabolize it. Hope this helps.