I So Am Taking One Tablet Zerodol Sp Daily I

I so am taking one tablet zerodol sp daily I had rods in my back three years ago very successful but lately really bad back pains exray clear just wear and tear I take Telma h blood pressure oxybutin 2.5mg three a day for head sweats the zerodol sp is amazing no back pain and I am able to walk half an hour excercise every morning with no pain. How long can I take this medication for

Willy