Actually there is very credible research.  Tramadol which is marketed as Ultram for humans was researched very thoroughly on dogs first.  I already put some of the research on a couple of sites.  Almost all drugs are tested on dogs first.  Not sled dogs, usually Beagles, but half life time would not change from breed of dog....Although classed as an opiate, it is not an opiate although a decent pain killer.  It works similar to Cox 2 inhibitors such as Celebrex.  In fact, because it reduces pain so well, it would be a very good drug to reduce the pain of a sore wrist or shoulder.  It acts seems to act as a euphoric in dogs, certainly not a sedative...