Brachalgia what we call it Its pain after brachial plexuses injury what your father is taking is right may have to increase the dose if he tolerates There few pain procedures like sympathetic ganglion ablation which may help him to certain extent and reduce the dose of medicine Advance treatments like spinal cord stimulators have been tried with limited effect its basically the central pain But pain procedures which are minimally invasive procedures which we do in pain clinics help many patients this is basically CRPS 2 ie complex regional pain syndrome due to nerve injury

Yes these medications have no life threatening complications nor they can lead to any end organ damage..

It is usually safe to continue these medicines. Since neuropathic pain is severe, we need such medicines for relieving the pain over the long run.