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

Question

Antipyretics like paracetamol are used to decrease the body-temperature in fever patients. But 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). Why? Is there any molecular mechanism responsible for this?

Answer 1

Fever is the result of a prostaglandin response that increases body temperature. The consumption of antipyretics (NSAIDs, APAP) cause - by an unknown mechanism - a hypothalamus override of this prostaglandin response, thus lowering an elevated temperature. If an antipyretic is taken for a non-fever symptom, for instance pain/inflammation, there is no prostaglandin-mediated elevation in temperature, therefore the body's temperature remains normal.