Vanessa,
I used to use 3 lidoderm patches to cover my entire left foot. I left them on 24 hours a day( not what they recommend). My doctors told me that they would not cause any damage and they didn't.
They didn't help to the root cause of my problem but they did help the pain topically(on the skin level) not the deep internal pains.

If you have a dog, be careful that your dog doesn't find them in the trash and eat them. My yellow lab was very fond of them!

Peace,
Lisa