We all know that every effective antidepressant has at least one worrisome side effect, so I do not particularly see why painkillers cannot be prescribed for the purpose of helping with depression. As an example, the pain medication I am currently taking does not even effectively handle the pain, but what it does do is take away the impulse to go and buy a gun and shoot myself in a head. In essence, in my case, the painkiller isn't killing pain, but making life worth living while I am experiencing severe pain.
So, really, why not? Even if only for short term depression (Sorry, sir, your mom just died, have some Vicodin) since tolerance is an issue.