Why do pharmaceuticals have half lives, while most other things we interact with don’t?

Question

EDIT: …Well I messed this thread up. I wasn’t referring to biological half life, but sitting-on-your-shelf half life. (i.e. expiry)

In: 0

Answer 1

The half life of a pharmaceutical is how long it takes the body to eliminate half the drug from the body.

This is important because you want to keep the amount of drug at a therapeutic level, but not have it reach a toxic level.

After 1 half life of the drug has elapsed, there is only half the amount remaining in the body. After 2 half lives, a quarter remains, and so on.

Knowing this, and the therapeutic and toxic levels of the drug, it is possible to calculate an effective dosing regimen.