When I crushed 3 fingers on my left hand in a goods lift door at work I ended up at hospital emergency where they gave me a painkiller by injection. 8 hours later once they X-rayed, set and sprinted the fingers they sent me home with 12 oxycodone tabs with instructions to start taking them once I could feel my damaged fingers. About 4 hours later I took one tab and besides thinking I was being attacked by monsters, I found I could hardly stand up and almost toppled over a balcony balustrade.
I treated the pain with cold packs and flannel pouches filled with ice - this went on for 3 days and by then the pain was just a dull ache. Obviously not a long or even short term remedy for a bung back or chronic pain but I was still amazed how well the ice worked.