Ketamine blocks 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.

A reboot for pain relief

Ketamine is not a new drug. It has been used safely for five decades in human and veterinarian medicine, most commonly as a general anesthetic. In large anesthetic doses, it results in a complete loss of consciousness while preserving certain protective reflexes, which has made it attractive to anesthesiologists and led to its inclusion on the World Health Organization’s list of most essential medications.

While it does stimulate opiate receptors, its action in sub-anesthetic 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.” A series of low dose ketamine infusions in awake patients can dramatically alter — or even eliminate — chronic pain.

The Ketamine Experience during pain treatment

Ketamine infusions for pain are generally well tolerated, but it’s best to be fully informed about what you may experience during chronic pain treatment. Because ketamine is a derivative of phencyclidine or PCP (a psychedelic compound), it can cause hallucinations in some patients if not combined with sedation. You will be given a benzodiazepine which controls this potential side effect.

Other possible side effects include nausea and, infrequently, headaches. These issues can also be treated during the infusion. Following treatment, you will likely be tired for several hours, and will need to be accompanied home by a friend, family member or other caregiver. In general, side effects are infrequent and relatively mild. Unlike other pain treatments and medications, ketamine is non- addictive and there are no long-term side effects when administered in the controlled, relatively low doses used to treat chronic pain.

What can I expect?

We develop individualized protocols depending on the nature of your pain and your response to the initial treatment. In some cases, a series of treatments will be recommended, often daily for a period of a week or more. While we can’t predict the duration of pain relief, our goal is to achieve weeks or months of lasting relief following these treatments. Most patients who enjoy prolonged pain relief will need to return on occasion for booster infusions or take  a controlled amount of oral ketamine at home.

In order to safely gauge your response, the first two ketamine infusions will be at lower doses and of shorter duration. Starting with the third dose and thereafter, the duration of the infusions will average about four hours. The ketamine dosage will be determined individually according to your response. While our success rates are high, there is no guarantee…approximately 20% of patients will unfortunately not experience relief. After the first two infusions, we will decide together whether the continuation of ketamine therapy is right for you. If you are one of the 80%, however, ketamine therapy can once again open the doors to full, active life with sustained pain relief you may have thought was out of reach.

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