NMDA receptor antagonists
A specific receptor called the N-methyl-D-aspartate (NMDA) receptor is very important in the development of neurogenic pain. A number of drugs block this receptor, notably ketamine, a drug which has been used in Anaesthesia for many years.
We use ketamine in Palliative Care by subcutaneous infusion for some nerve pains associated with cancer. Ketamine is, however, not as predictably effective taken by mouth. Some other drugs also act at the NMDA receptor, including dextromethorphan, amantadine and memantine. These drugs have been used occasionally to treat neuropathic (nerve) pain.
We do not normally use ketamine long-term or in pain caused by conditions other than cancer. It is a drug which is potentially addictive and can cause drowsiness and unpleasant hallucinations, and on chronic use at higher doses it can cause significant damage to the bladder.
Further reading:
Pain Service Website, Gloucestershire Hospitals NHS Foundation Trust
Webmaster Dr J G de Courcy, Consultant in Pain Medicine and Anaesthesia
email: pain.webmaster[at]glos.nhs.uk