I'm not sure if you have any biomedical background so I will start from the beginning. Looking for details on "how a medicine works" the key phrase is "mechani

I'm not sure if you have any biomedical background so I will start from the beginning. Looking for details on "how a medicine works" the key phrase is "mechanism of action". This is a description of known interactions of a medicine with protein molecules in the body. DNA is code for proteins and proteins are the interactors in the body (a rough analogy is DNA is the source code, proteins are the binary). So, the mechanisms of action are the key to both major effects and side-effects. If a medicine works well, it mediates a single pathway of protein interactions and produces no degradation products or side-effects in other pathways. Here are wikipedia descriptions of mechanisms of action for different medicines: https://en.wikipedia.org/wiki/Paracetamol#Mechanism_of_action https://en.wikipedia.org/wiki/Paracetamol#Mechanism_of_actio... https://en.wikipedia.org/wiki/Mechanism_of_action_of_aspirin https://en.wikipedia.org/wiki/Mechanism_of_action_of_aspirin https://en.wikipedia.org/wiki/Ibuprofen#Mechanism_of_action https://en.wikipedia.org/wiki/Ibuprofen#Mechanism_of_action They do have COX inhibition in common. COX is a protein enzyme that mediates pain and inflammation response: https://en.wikipedia.org/wiki/Cyclooxygenase https://en.wikipedia.org/wiki/Cyclooxygenase However, they have slightly different side effects (secondary interactions) and some may have additional primary interactions (those that mediate pain). For instance there is evidence that tylenol has direct interaction with receptors in the spinal cord to mediate nerve signaling (separate from inflammatory and pain response sources via COX). So, the indication of a side-effect with acetaminophen does not imply there is a definite side-effect with all painkillers (or even all COX inhibiting painkillers). Although it is a good indication that other painkillers should be evaluated for the effect and if it is common to all COX inhibiting painkillers then it may be that specific path. Living animals are a beautiful and complex interaction of proteins and small molecules. It is exciting when we determine how one piece of the puzzle might work. The complexity involved makes it difficult to broadly apply results until the broader context has been evaluated.