system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do painkillers 'seek out' the source of pain?

Title pretty much says it, how do painkillers know where the pain is?
gpt
generally they dont. Many pain killers are actually just anti-inflammatory drugs as any part in you body that is in pain will also be inflammed, so reducing this will also reduce pain.

EDIT: so in ELI5 mode: drugs go all over your body (bloodstream) but only affect places in pain.