Do painkillers really stop the pain or does it produce more adrenaline?

okay im trying to find some science fair projects i really want to win this comming january i want to do someting medical related or something that beneficial to science so do pain killers sto the pain or produce more adrenaline so we wont feel it? btw can you also give me some WINNING science fair project topics or ideas? PLZ and THANK YHU it would mean the world to me ^-^