Why antipyretics do not bring the body-temperature below normal?

Question

Antipyretics like paracetamol are used to decrease the body-temperature in fever patients. \nBut some of them are also used as pain-killers in sprain or other injuries (where there's no fever). In that case they changes the body temperature very little (if any). \nWhy? Is there any molecular mechanism responsible for this?

Answer 1

When your immune system is killing bacteria they often release pyrogens - chemicals that cause the fever. The drugs block these from working. Your normal body temperature does not use or require pyrogens to maintain itself. It a case of taking them for pain, there is no effect on temperature because what they fix bout a fever isn't happening.