Abstract
The efficacy of the N-methyl-D-aspartate receptor antagonist ketamine as an analgesic agent is still under debate, especially for indications such as chronic pain. To understand the efficacy of ketamine for relief of pain, we performed a literature search for relevant narrative and systematic reviews and meta-analyses. We retrieved 189 unique articles, of which 29 were deemed appropriate for use in this review. Ketamine treatment is most effective for relief of postoperative pain, causing reduced opioid consumption. In contrast, for most other indications (that is, acute pain in the emergency department, prevention of persistent postoperative pain, cancer pain, and chronic non-cancer pain), the efficacy of ketamine is limited. Ketamine’s lack of analgesic effect was associated with an increase in side effects, including schizotypical effects.
Highlights
The efficacy of the N-methyl-D-aspartate receptor antagonist ketamine as an analgesic agent is still under debate, especially for indications such as chronic pain
We recently showed in rodents that activation of the innate repair receptor (IRR) by ketamine is a prerequisite for relief of neuropathic pain symptoms[4]
As it is our experience that ketamine’s efficacy differs among the different pain phenotypes, we present the results of our search separated by type of pain: acute non-postoperative pain, acute postoperative pain, prevention of chronic pain following surgery, chronic non-cancer pain, and cancer pain
Summary
Our appraisal of narrative and systematic reviews and metaanalyses gives a rather inconsistent picture of the efficacy of ketamine for the treatment of pain. Numerous case reports, case series, and open-label studies show ketamine efficacy in the amelioration of acute and chronic pain[5,48,49]. Often ketamine exposure is limited because of dose reduction in fear of side effects This will cause analgesic responses no greater than those of placebo in the treatment of acute and chronic pain. (v) Scoring pain by using numerical or visual scales that require defining a lower (no pain) and upper (most intense pain imaginable) boundary is a complex process It requires the activation of specific mental tasks that may be difficult in patients with chronic pain or patients who are cognitively impaired[50,51]. Patients represented in case series may have more extensive disease progression with more severe pain symptoms than patients in RCTs. (viii) publication bias may have resulted in the appearance of many positive open-label studies in the literature, possibly unintentionally balancing against the many negative RCTs
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