Does Long Term Use Of Codeine, Morphine And Gabapentin Cause Side Effects?

Hi, I am 46 yo male, history of back pain from 11 yrs. Multiple injuries to lower back. instrumented fusion 7 years ago L 4, L 5, S 1. During surgery vertebrae split while placing screws. Good relief from referred and localised pain for two or three years. For the past 4 years I have been suffering from increased pain and disability, bone scans and MRI scans have shown some scar tissue around nerve roots. was scheduled for CT guided injection but technician could not find a way past metalwork. Last epidural ( 12 months ago ) agrivated my condition. Have been using codeine daily and morphine and have been prescribed gabapentin. I am scared of side effects and have an instinctual fear of this drug. I am about to ask my Doctor for Pentaoxiphylline and vitamin E to try to control scar tissue in a physiological sense but I need to know a time frame. I have heard of trials but can find no info regarding these and would like to know more, can anyone help me, my life is a constant re agrivation and I am becoming more and more disabled. I think Arachnioditus is my problem.