Drug elimination depends on a lot of factors, but very importantly is the order of kinetic and half life of the drug in question. There is first order kinetic where a constant fraction or proportion of the drug is eliminated at every half life of the drug e.g if the half life of a drug is 10hr, and 50% is eliminated every half life. No matter the concentration, every 8hr half of the concentration only will be eliminated and half of whatever is leftover in the next 8hr and then like that and like that. While in zero order kinetic a constant amount is eliminated, not fraction in this case. No matter the concentration in blood only that amount can be eliminated every half life. e.g assuming you take 200mg of a drug with 6hr half life and only 20mg can be eliminated every half life. It will take like 600hr to fully eliminate such drug i.e 20mg every 6hrs.
The half life of some drugs is days, weeks or even months.
Thank you so much for explaining it in such a way that a non-medical person like myself can follow and understand it. 🙏
So it is more likely to be (up to) months, rather than years, as the maximum length of time a drug might remain present, depending on the drug. Very good to know. 👍
Yes, usually in trace amount.