why the time that drugs like caffeine affect you are measured with “half life” regardless of the amount ingested rather than a constant rate

Question

Does the body not clear drugs like caffeine at a constant rate? If you drink less caffeine does the body clear it less quickly? Or am I not understanding it? Caffeine half life is about 5 hours (via Google), so regardless of if I drink 100mg or 900mg of caffeine, half (50mg or 450mg) will be left in my body 5 hours later? That seems like a pretty drastic difference in the rate of clearance.

In: 509

Answer 1

Imagine your job is to pick out rice from wheat, or something similar. When there is a lot of rice, it is easy to remove a lot of it. But less rice there is in the wheat, slower you would remove it

First you can pick out 10 grains per minute, but you might spend half an hour searching for the last grain