system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do pills (like back pills) target a specific area of the body?
gpt
They *don't* target a specific area of the body. They are dissolved, and absorbed into our bloodstream, and then go to every part of our body (except for potentially our brain, which is protected by the "blood/brain barrier" that only some chemicals can pass through).

Pills that relieve pain do so everywhere in the body, and not just on one place.