How Effective is Ketamine in the Management of Chronic Neuropathic Pain?

Abstract

Ketamine is a promising treatment for chronic neuropathic pain. "

Low-dose ketamine infusions for chronic pain management: Does this qualify as evidence-based practice?

“…21 Chronic neuropathic pain syndromes that have been studied with subanaesthetic-dose ketamine infusions (SDKIs) include phantom limb pain, postherpetic neuralgia, spinal cord injury, and oncological neuropathic pain. 14,31,32 In comparison, nociceptive pain, the most common type of chronic pain, results from neural pathway stimulation secondary to either physical stimuli or a disease process affecting somatic structures, such as arthritis and most spinal pain syndromes. 21 In other words, nociceptive pain is caused by tissue damage or the potential of damage stimulated by a disease process, and may be described as throbbing, aching, or a pressure sensation.…”

“…Recent systematic reviews, meta-analyses, and primary studies have reported modest improvements in chronic pain outcomes from SDKIs. 4,7,11,12,[31][32][33]46 Although there is no formal consensus, a significant effect that may translate to clinical utility is typically determined by most researchers as a ≥2 reduction in pain scores (1-10), or a ≥30% reduction in pain intensity as suggested by US guidelines. 37 A meta-analysis of randomised controlled trials (RCTs) by Michelet and colleagues (2017) concluded that a single dose of ketamine was effective in reducing chronic noncancer pain at 1, 2, 8, and 12 weeks but not 4 weeks; however, they included non-IV formulations which may have skewed their results.…”

“…9 Notwithstanding, this report is just one example of the high drop-out rates seen in primary studies examining SDKIs in chronic pain; hence, most original studies are small RCTs with methodological limitations which reduces the robustness of subsequent meta-analyses. 1,2,32 In addition to the limited power from small sample sizes, significant study heterogeneity concerning study populations and infusion protocols, along with short and varying follow-up durations, are major sources of bias that complicate conclusions on the effectiveness of SDKIs. 2,11 Moreover, blinding has been shown to be challenging in some RCTs due to the experience or anticipation of psychomimetic effects, 1 with one trial reporting that 75% of participants guessed their treatment correctly, 50 and 93% in another small trial of 30 participants.…”

“…11,32,59 Moreover, since the goal of chronic pain management is to reduce pain to an acceptable level to promote functional recovery, 2,26 it is unclear how the observed improvement in pain scores from SDKIs translates clinically to an improvement in functional capacity. 32 Identifying further outcome measures beyond numerical pain scales should be considered to help further elucidate the risk-benefit profile of SDKIs, such as longitudinal measurements of functional capacity and independence. 12 Regarding treatment duration, the consequences of prolonged clinical (non-recreational) administration are not sufficiently evidenced to make recommendations as to when a refractory chronic pain patient can safely terminate treatment with SDKIs while avoiding long-term complications or dependence.…”

Impact of Ketamine in the Management of Painful Sickle Cell Disease Vaso-Occlusive Crisis

“…[8][9][10] Ketamine has demonstrated positive effects in opioid resistant or refractory cancer pain syndromes, surgical pain management as an adjuvant to opioids, and is increasingly used in the treatment of chronic neuropathic and non-cancer pain. [11][12][13] New guidelines from the American Society of Hematology recommend the use of subanesthetic doses of ketamine as an adjunctive therapy in refractory pain in SCD. Although the data is limited, the recommended dose of ketamine is 0.1 to 0.3 mg/kg/hour with a maximum of 1 mg/kg/hour; however, this is a conditional recommendation as there has been limited experience utilizing ketamine infusion for the management of SCD-VOC pain.…”