Hi,
As Anthony has already said, their is some discussion as to the efficacy of Imipramine (tricyclic antidepressant) when used as an analgesic (pain relief). that said, however, it has been used with a good result, for neuropathic pain (pain that results from the damage of neural tissue).
this is an exerpt from www.bnf.org:
Neuropathic pain is generally managed with a tricyclic antidepressant and certain antiepileptic drugs. Neuropathic pain may respond only partially to opioid analgesics. Of the opioids, methadone, tramadol, and oxycodone are probably the most effective for neuropathic pain and they may be considered when other measures fail. Nerve blocks, transcutaneous electrical nerve stimulation (TENS) and, in selected cases, central electrical stimulation may help. Many patients with chronic neuropathic pain require multidisciplinary management, including physiotherapy and psychological support.
sidenote:
If you are suffering from back pain, and medications are not helping very much, try talking to a hypnotherapist. you will need to get a letter of permission from your doctor in order for the hypnotherapist to begin treatment. they will not be able to remove the pain, but they may be able to greatly reduce the pain and/or its effects on your daily life. they will also be able to teach you some techniques to help combat any breakthrough pain.
hope that this helps.
Be Well.