The Science of Ketamine
The Science of Ketamine
The NMDA Receptor
The dorsal horn of the spinal cord is important for the transmission and modulation of pain signals arising in the periphery. An important receptor in the dorsal horn is the NMDA receptor. Peripheral pain causes the release of glutamate which binds to this receptor. This results in an opening of the NMDA receptor channel allowing the influx of ions which leads to a cascade of neurochemical events ending with pain perception by the brain. With prolonged stimulation of these receptors, a central sensitization occurs. Ketamine blocks the NMDA receptor and stops the transmission of peripheral pain signals to the brain. With prolonged blockage during Ketamine Infusion Therapy, the brain “reboots” and stops interpreting peripheral stimulation as pain.
Ketamine is not a new drug. It has been used for five decades in human and veterinarian medicine. Most commonly it has been used as a general anesthetic agent. In anesthetic doses it results in a complete loss of consciousness while preserving certain protective reflexes. That has made it attractive to anesthesiologists in selective patients. While it does stimulate opiate receptors, much like morphine, its action in subanesthetic doses as an NMDA receptor antagonist is much more important in the treatment of chronic pain. By blocking the receptor and closing the channel to ion transport, pain signal transmission is interrupted giving central pain centers a chance to “reboot”. One or a series of low dose ketamine infusions in awake patients can dramatically alter or even eliminate their chronic pain. Ketamine infusions have been most often used when other treatment modalities have been less effective. Certain types of pain considered to be “neuropathic” in origin have been most studied and are considered to be most responsive to ketamine therapy. However, other types of chronic pain such as chronic temporal mandibular joint (TMJ) pain, some headaches, and musculoskeletal pain may also benefit from ketamine infusions. The list of chronic pain syndromes that benefit from ketamine therapy continues to grow.
Ketamine Side Effects
Ketamine infusions are generally well tolerated, and few patients need to terminate treatment because of side effects. Still, ketamine is a derivative of phencyclidine (PCP) a known psychedelic and if not combined with sedation can cause hallucinations in many patients. You will be given a benzodiazepine to control this dysphoria. Other possible side effects include nausea and rarely a headache. These side effects also can be treated during the infusion. Following treatment patients will be tired for several hours and need to be accompanied home by a responsible adult. There are no long term side effects associated with Ketamine in the relatively low doses used to treat chronic pain. There is no chance of addiction to Ketamine.