why do drugs stay in one’s system for much longer than their effect? For example, diazepam stays in a person’s system 8-10 days, but it’s effects last 4-5 hours? Why the difference?
In: Chemistry
Taking medicine and your body using that medicine isn’t a linear process. It’s much more like radioactive decay with a half life. So for example, say the half life is 6 hours, after 6 hours, half of it is metabolized by the body, then after another 6 hours half of that half, so 3/4 of it is gone. Then after another 6 hours, another half goes away, so how 7/8 is gone. Most medicine will be detectable for 4 to 5 half lives, meaning that only about 3-6% is left.
However that doesn’t mean the medicine is effective at treating symptoms that whole time. Theres typically going to be some minimum threshold needed for it to be effective. But that amount is much much more than the amount needed to be detectable.
I just checked, diazepam has a half life of 48 hours. So using the 4-5 half lives then yeah, that lines up with what you were saying that it should stay detectable for 8-10 days. So in diazepam’s case, you need a lot of it in your system for it to be effective, which is why its effects are short.
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