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10 Articles in this Series
Introduction
An AAPM 2019 Preview
APRNs/PAs in Pain Medicine SIG Gets Underway
Cannabis Has Entered Pain Management and Is Here to Stay: What Clinicians Need to Consider
Managing Pain in Marginalized Populations, including Ethnic Minorities, LGBTQ, and the Obese
Neuromodulation: A Roundtable on Current Best Practice & Key Questions
Pro/Con: CGRP Antibodies and Treatment Choice for Chronic Migraine
Pro/Con: Conservative Care is the Best Route for Chronic Pelvic Pain
Pro/Con: CRPS - Use Everything but Stimulation
Pro/Con: Ketamine for Complex Regional Pain Syndrome, Neuropathic Pain, and More
Pro/Con: Radiofrequency Denervation is Effective (The MINT Studies)

Pro/Con: Ketamine for Complex Regional Pain Syndrome, Neuropathic Pain, and More

A Pro-Con Debate* on the following statement, held at the 2019 annual meeting of the American Academy of Pain Medicine (AAPM):  "Ketamine Should Be Used Beyond CRPS "

 

PRO, offered by May L. Chin, MD:

Approved by FDA in 1970, ketamine has evolved from an anesthetic to an analgesic. Due to its mechanism as an NMDA antagonist, there has been rekindled interest in its use across pain management. Ketamine also activates the descending inhibitory pathways and interacts with mu opioid receptors, offering strength in treating neuropathic pain, and as shown more recently, offers antidepressant effects as well.

With complex regional pain syndrome (CRPS) in particular, there are multiple mechanisms at play and the pathophysiology is poorly understood. Both peripheral and neuropathic pain patients suffer severely and often have exhausted other options before seeking ketamine infusion.

Studies have shown ketamine’s benefit in such neuropathic conditions (see Niesters, BJCP, 2013 and Maher, A&A, 2017). Some are observational and retrospective so the level of evidence is not high. But in 2016, a consensus guideline on ketamine for chronic pain did emerge. While we need better science with bigger numbers, especially regarding ketamine’s duration of action and long-term adverse effects, there is a rational role for it in treatment plans for many chronic neuropathic pain conditions, including CRPS. Patients deserve to have it as an option that is not an opioid.

 

CON, offered by Stephen D. Coleman, MD: 

Just like Dr. Chin, we see CRPS patients who have tried numerous approaches, are hard to manage, and are trying to find new, successful modes of therapy. Patients have expressed interest in trying ketamine due to its rising discussion in the media. There is good data for it in depression, post-operative pan, cancer-associated pain, and even some for CRPS, but for non-CRPS neuropathic pain.

What is the evidence supporting its sustained effect after blood levels of ketamine have dissipated, for instance? We cannot run patients on an infusion forever. Most studies conducted on ketamine to date were not designed to look at long-term effects. The consensus guideline Dr. May mentioned was questioned by AAPM Program Co-Chair Steve Cohen, in Pain Medicine, in 2018. In one meta-analysis for chronic neuropathic pain, there was no difference in control and ketamine groups in three of the seven RCTs reviewed. In addition, there are known acute adverse effects (psychomimetic) and chronic exposure is not well studied. Thus, we don’t really know which patients should be considered for ketamine infusion. Those with CRPS, spinal cord injury, PHN, fibromyalgia, those with ischemic pain, migraine, or low back pain? There are varying levels of low to weak evidence.

Due to the uncertainty of which patients to use, the duration and frequency of infusions, and known and unknown side effects, I would use caution in considering ketamine. Its use could delay arriving at an effective treatment that may be more long term. Some patients only get benefit during the actual infusion or immediately after and then end up requesting it more and more. Is ketamine simply, therefore, a psychoactive placebo?

 

-Reported by Angie Drakulich 

*Quotes and comments are paraphrased for clarity and style. Commenters’ disclosures may be found on the AAPM35 speakers’ website.

Next summary: Pro/Con: Radiofrequency Denervation is Effective (The MINT Studies)
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