Has the doctor determined the cause of the pain? If it is purely muscular, the best things to do are stretches to loosen up the muscles and ice.
I woke up in Jan. 2006 and could not move without excruciating pain in my lower back, couldn't walk, get up, sit down, lay down, etc. I took 800 mg of ibuprofen, to no avail. Luckily, it was a week day and I was able to get in to see a chiropractor who also told me the importance of doing stretches to alleviate the muscle tension that was causing me so much pain. It was the first time that I had been to a chiropractor where I was told there were things I could do, other than returning to the chiropractor every day, to get better.
I still have lower back problems, particularly when sitting for a long time...bleachers are the worst. Thankfully, I am armed with stretching techniques that I can do at home to reduce the pain. That an icing (not heat) are great ways to alleviate pain without the need for the meds you are talking about.
If you know any athletes, they would be able to tell you some good excercises that stretch, leg, gluts and lower back muscles.