Prednisone
"Suffering from severe lower back pain for more than a month I finally went to the doctor convinced I would be told there was nothing to be done but to soldier through it.  Instead I was prescribed a week-long course of prednisone.  Results started within hours.  I was almost pain-free the next day.  By day three other ailments I had just been living with, such as stiff knees and shoulder pain, were also gone.  It's a wonder drug.  But for the long term side effects I'd stay on it indefinitely if I could."