Ketamine is an old medicine that has been finding new uses recently in the treatment of pain. No one is quite sure how exactly it works, although purported mechanisms include its action on opposing the NMDA receptor which is a receptor that mediates the pain signal. Other targets include the AMPA receptor, the nicotinic and muscarinic receptors as well as opioid receptors. Rather than a being a “smart bomb”, ketamine is like a cluster bomb that affects many different things at once. It has also been used on the battlefield for anaesthesia so that surgeries like amputations can be performed there and then.
Instead of functioning like a painkiller like paracetamol or morphine, ketamine seems to work by opposing changes in the central nervous system that may cause chronic pain. It also seems to work to the body more sensitive to opioids again, thus avoiding the dose escalation that is often seen in opioid therapy.
Ketamine does have side effects such as mood changes and hallucinations, although these are short lived and will disappear after some time after the treatment is stopped.
Whether ketamine treatment will work in helping you out of your chronic pain issue is not certain, but if you have tried other treatments and are already on opioids which seem to be less effective than before, then ketamine treatment is certainly worth a try.