Posted by Larry Hoover on July 5, 2003, at 10:15:29
In reply to Accumulation of drugs., posted by Mats on July 5, 2003, at 2:37:54
> Hi!
>
> Something that has been in my mind for sometime now is the accumulation of the med in our systems.
> We all get a rough estimate of halflife of our med. But halflife almost always reach over 24h!
> That must meen that accumulation is in stake?
> Someone with a more sober explanation?Accumulate can mean different things. If you mean that you're wondering if your body has the capacity to permanently store the drugs, no, they don't accumulate like that.
Without getting into calculus, it's generally accepted that there is an upper limit to the concentration of the drug in the body, which is called the steady state. In this steady state condition, the sum of all the processes which reduce the concentration (generally, metabolism and excretion) equal the dose, or intake. It takes roughly six half-lives to reach steady state. The only real variable is that your half-life will not be identical to mine. For some drugs, there is a vast range of half-lives across the population. Usually, you'll only see the average half-life reported.
> If accumulation do indeed occur, what do our bodies do with it?
That depends on the drug. Many drugs are metabolized by liver enzymes, and those metabolites may or may not be active themselves. Diazepam (valium) for example, has all kinds of active metabolites. Other drugs are simply gathered up by the kidneys and excreted, or sometimes they end up in bile.
One of the functions of liver enzymes is to "label" strange or foreign molecules with specific changes to their structure. This enhances the excretion of the labelled molecules, because the kidneys (especially) are set up to recognize those labels.
>And what does it meen to receptor bindning?
At steady state, you should have a stable influence on receptors. That's the whole idea behind dosing.....the intake level is set with the steady state concentration in mind.
Lar
poster:Larry Hoover
thread:239430
URL: http://www.dr-bob.org/babble/20030701/msgs/239467.html