Ketamine for refractory chronic pain: a one-year follow-up study

Illusory finger stretching and somatosensory responses in participants with chronic hand-based pain

Current pharmaceutical interventions for chronic pain are reported to be minimally effective, leading researchers to investigate non-pharmaceutical avenues for chronic pain treatment. One such avenue is resizing illusions delivered using augmented reality. These illusions resize the affected body part through stretching or shrinking manipulations and have been shown to give analgesic effects; however, the neural underpinnings of these illusions remain undefined. Steady-state evoked potentials (SSEPs) have been studied within populations without chronic pain undergoing hand-based resizing illusions, finding no convincing differences in SSEP amplitudes during illusory stretching. Here, we present comparable findings from a sample with chronic pain, who are thought to have blurred cortical representations of painful body parts, but again find no clear differences in SSEP amplitude during illusory stretching. However, no significant decreases in pain ratings were found following illusory resizing, and changes in SSEP amplitudes are thought to possibly reflect experiences of illusory analgesia. Despite a lack of illusory analgesia across the sample, several participants experienced clinically meaningful levels of pain reduction following illusory resizing, highlighting the potential of resizing illusions as an analgesia treatment avenue. Subjective illusory experience data showed significantly greater experiences of the illusion in the multisensory (visuotactile) condition compared to non-illusion conditions and a unimodal visual condition, replicating findings from participants without chronic hand-based pain. Exploratory analyses using subjective disownership data show that the multisensory condition did not elicit significant disownership experiences, demonstrating that the pain reductions seen in the multisensory condition do not arise from disownership of the limb, but more likely as a direct result of the illusory resizing manipulations.

Effects of Diathermy on Pain in Women with Fibromyalgia: A Randomized Controlled Trial

(1) Background: The main characteristic of fibromyalgia (FM) is generalized musculoskeletal pain. This may be accompanied by muscle and joint stiffness, sleep and mood disorders, anxiety and depression, cognitive dysfunction, and chronic fatigue. It is endemic in developed countries, with a higher prevalence among women than men, and its etiology is still unknown. Diagnosis is made based on chronic generalized pain and through the presence of tender points. The objective of this study was to analyze the efficacy of diathermy on pain in patients with fibromyalgia. (2) Methods: A single, blind, randomized experimental study was developed with a sample of 31 participants. Measurements were taken and recorded at three different intervals using the following measurement tools: the pressure pain threshold (PPT) at the tender points (TP) of the right and left trochanteric prominence with an algometer, the pain measurement scale, the Fibromyalgia Impact Questionnaire, the sleep quality index (PSQI, Pittsburgh), the Multidimensional Fatigue Inventory (MFI-S), and the scale for anxiety and depression (Hospital Anxiety and Depression Scale). Sociodemographic data were collected through Google Forms (age, height, weight, Body Mass Index). The intervention took place twice weekly across four weeks of sessions. (3) Results: Statistically significant results were obtained in the right and left trochanter PPT, as well as for anxiety and fatigue in the experimental group. The results obtained show that this treatment has managed to improve the quality of sleep, the impact of disease, chronic fatigue, and anxiety in patients with FM. (4) Conclusions: Diathermy is a tool that can help reduce pain. It can also improve the baseline levels of chronic fatigue, anxiety, the impact of the disease, and sleep quality in patients with fibromyalgia.

Low-dose ketamine infusion to facilitate opioid tapering in chronic non-cancer pain with opioid-use disorder: a historical cohort study

BACKGROUND

Long-term opioid use is associated with pharmacological tolerance, a risk of misuse and hyperalgesia in patients with chronic pain (CP). Tapering is challenging in this context, particularly with comorbid opioid-use disorder (OUD). The antihyperalgesic effect of ketamine, through N-methyl-D-aspartate (NMDA) antagonism, could be useful. We aimed to describe the changes in the dose of opioids consumed over 1 year after a 5-day hospitalisation with ketamine infusion for CP patients with OUD.

METHODS

We performed a historical cohort study using a medical chart from 1 January 2014 to 31 December 2019. Patients were long-term opioid users with OUD and CP, followed by the Pain Center of the University Hospital of Toulouse, for which outpatient progressive tapering failed. Ketamine was administered at a low dose to initiate tapering during a 5-day hospitalisation.

RESULTS

59 patients were included, with 64% of them female and a mean age of 48±10 years old. The most frequent CP aetiologies were back pain (53%) and fibromyalgia (17%). The baseline opioid daily dose was 207 mg (±128) morphine milligram equivalent (MME). It was lowered to 92±72 mg MME at discharge (p<0.001), 99±77 mg at 3 months (p<0.001) and 103±106 mg at 12 months. More than 50% tapering was achieved immediately for 40 patients (68%), with immediate cessation for seven patients (12%). 17 patients were lost to follow-up.

CONCLUSIONS

A 5-day hospitalisation with a low-dose ketamine infusion appeared useful to facilitate opioid tapering in long-term opioid users with CP and OUD. Ketamine was well tolerated, and patients did not present significant withdrawal symptoms. Prospective and comparative studies are needed to confirm our findings.

Ketamine in neuropsychiatric disorders: an update

The discovery of ketamine as a rapid-acting antidepressant led to a new era in the development of neuropsychiatric therapeutics, one characterized by an antidepressant response that occurred within hours or days rather than weeks or months. Considerable clinical research supports the use of-or further research with-subanesthetic-dose ketamine and its (S)-enantiomer esketamine in multiple neuropsychiatric disorders including depression, bipolar disorder, anxiety spectrum disorders, substance use disorders, and eating disorders, as well as for the management of chronic pain. In addition, ketamine often effectively targets symptom domains associated with multiple disorders, such as anxiety, anhedonia, and suicidal ideation. This manuscript: 1) reviews the literature on the pharmacology and hypothesized mechanisms of subanesthetic-dose ketamine in clinical research; 2) describes similarities and differences in the mechanism of action and antidepressant efficacy between racemic ketamine, its (S) and (R) enantiomers, and its hydroxynorketamine (HNK) metabolite; 3) discusses the day-to-day use of ketamine in the clinical setting; 4) provides an overview of ketamine use in other psychiatric disorders and depression-related comorbidities (e.g., suicidal ideation); and 5) provides insights into the mechanisms of ketamine and therapeutic response gleaned from the study of other novel therapeutics and neuroimaging modalities.

[Ketamine in chronic pain]

Ketamine is now frequently used in the management of chronic pain refractory to conventional treatments. However, its efficacy and adverse effects appear variable in the literature in line with heterogeneous methodologies and modes of administration, leading to controversy regarding the actual interest of ketamine for chronic pain treatment. A need for clinical trials on larger cohorts of well selected patients but also real-life studies to more accurately quantify its efficacy, refine its prescription dosages and better understand its long-term adverse effects is highlighted in the literature. Progress in this direction has been achieved in recent years with improved recommendations for use, taking into account different trajectories of analgesia with ketamine, depending on the etiology of the pain, and the psycho-affective profile of patients. A holistic approach is clearly needed with consideration of pain and depression comorbidities to optimize pain management.

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

Chronic pain is becoming increasingly prevalent and burdensome both worldwide and in the United Kingdom. Due to the complexity of chronic pain and the therapeutic challenge associated, management is often difficult and requires multidisciplinary care encompassing a combination of pharmacological and non-pharmacological strategies. Conventional analgesic treatments, such as opioids and anticonvulsants, are effective in less than half of chronic pain sufferers and are typically limited to short-term use to prevent complications associated with long-term use such as tolerance and dependence. Consequently, research and clinical interest in alternative management options for chronic pain have increased in recent years, with ketamine being one example under investigation. However, since ketamine has been licensed as an anaesthetic for decades, it has bypassed the traditional scrutinous drug development sequence that is typically seen for therapeutics marketed for pain. As such, data supporting the unlicensed administration of ketamine for chronic pain management is lacking and is being outpaced by the rates of off-label use in pain clinics. Recent limited evidence suggests that ketamine, when given as an intravenous infusion in subanaesthetic doses for refractory pain patients, may provide modest analgesic effects in nearly all aetiologies of chronic pain, with side effects common but typically mild. However, there are concerns over the safety of this practice due to the paucity of robust supportive evidence and the accompanying lack of clinical guidelines or standardised protocols. This review shall summarise the literature examining the use of subanaesthetic-dose ketamine infusions for chronic pain to comment on the current level of evidence, with limitations of existing research and future recommendations discussed.

Ketamine for Chronic Pain and Mental Health: Regulations, Legalities, and the Growth of Infusion Clinics

PURPOSE OF REVIEW

In this article, we will review evidence for ketamine's role in chronic pain and mental health conditions, its current legal status and abuse potential, and the regulations related to its administration in stand-alone infusion clinics, as well as future considerations.

RECENT FINDINGS

In the management of chronic pain, ketamine has shown potential to manage neuropathic pain and complex regional pain syndrome and has been used as a treatment for chronic pain management by clinics across the USA. Analogous to the historic rise of lidocaine clinics, ketamine clinics are demonstrating a similar pattern of unregulated growth. Ketamine is an anesthetic and analgesic agent commonly used in the perioperative setting and emergency department for sedation and pain management (Mo et al in West J Emerg Med 21(2):272-281, 2020). It was approved for use by the Federal Drug Administration in the USA in the 1970s as the sole anesthetic agent for short diagnostic and surgical procedures (Coppel et al. in Anaesthesia 28(3):293-296, 1973; Schwenk et al. in Reg Anesth Pain Med 43(5):456-466, 2018). Regarding its rising popularity as a treatment option in mental health, ketamine holds promise as a rapidly acting treatment for suicidal ideation and refractory depression.

Narrative Review: Low-Dose Ketamine for Pain Management

Pain is the leading cause of medical consultations and occurs in 50-70% of emergency department visits. To date, several drugs have been used to manage pain. The clinical use of ketamine began in the 1960s and it immediately emerged as a manageable and safe drug for sedation and anesthesia. The analgesic properties of this drug were first reported shortly after its use; however, its psychomimetic effects have limited its use in emergency departments. Owing to the misuse and abuse of opioids in some countries worldwide, ketamine has become a versatile tool for sedation and analgesia. In this narrative review, ketamine's role as an analgesic is discussed, with both known and new applications in various contexts (acute, chronic, and neuropathic pain), along with its strengths and weaknesses, especially in terms of psychomimetic, cardiovascular, and hepatic effects. Moreover, new scientific evidence has been reviewed on the use of additional drugs with ketamine, such as magnesium infusion for improving analgesia and clonidine for treating psychomimetic symptoms. Finally, this narrative review was refined by the experience of the Pain Group of the Italian Society of Emergency Medicine (SIMEU) in treating acute and chronic pain with acute manifestations in Italian Emergency Departments.

Efficacy of ketamine for comorbid depression and acute or chronic pain: A systematic review

Pain and depression frequently co-occur. Due to its antidepressant and analgesic properties, ketamine has been used for the management of treatment-resistant depression and pain. This systematic review examined the literature on the efficacy of sub-anesthetic doses of ketamine in individuals experiencing comorbid depression and chronic pain (CDCP), as well as comorbid depression and acute pain (CDAP). A secondary objective was to provide an assessment of dosage, route, and adverse effects of ketamine treatment for CDCP and CDAP. A literature search was conducted on MEDLINE, PsycINFO, and Embase databases, coupled with a manual screening of the bibliography sections of included articles. In addition, registered ongoing and planned trials were searched on Clinicaltrials.gov. The end date of the search was April 9th, 2022. Included studies assessed changes in depression and pain in patients receiving at least one sub-anesthetic dose of ketamine. Assessment of quality was conducted using the GRADE checklist. Of the 7 CDCP clinical trials, 3 reported a reduction in depression and pain, 3 reported a reduction in depression or pain only, and 1 reported no improvement in either comorbidity. Among the 7 CDAP clinical trials, 4 studies found improvements in depression and pain while the remaining 3 reported improvements in only one parameter. Ten of the 12 case studies and 2 of the 3 observational studies assessing CDCP and CDAP found improvements in pain and depression scores post-treatment with effects of variable duration. The planned methodologies of the registered clinical trials are in line with those of the published research. Preliminary evidence supports the efficacy of ketamine in treating CDCP and CDAP. However, the current review identified a small number of heterogeneous studies with mixed results, preventing comprehensive conclusions. More longitudinal placebo-controlled studies are needed to identify the effects of ketamine for patients with CDCP and CDAP.

Pre-treatment Pain Symptoms Influence Antidepressant Response to Ketamine in Depressive Patients

BACKGROUND

Pain strongly coexists with depression. Ketamine has great analgesic and antidepressant effects, acting as a promising role in treating depression with pain. Few studies have evaluated impact of pain symptoms on antidepressant effect of ketamine infusions. Thus, present study investigated whether pain symptoms in individuals with depression moderate response to ketamine.

METHODS

One hundred and four individuals with major depressive disorder and bipolar depression received six intravenous infusions of ketamine. The Montgomery-Åsberg Depression Rating Scale (MADRS) was administered at baseline, the next morning after each infusion and 2 weeks (Day 26) after the last infusion. Pain symptoms were collected at baseline using the short-form McGill Pain Questionnaire (SF-MPQ).

RESULTS

The prevalence of pain in patients with depression was 48.8%. Mix model analyses showed that pre-treatment pain symptoms assessed by each domain of SF-MPQ significantly moderated antidepressant response to six infusions of ketamine from baseline to day 26 (all p < 0.05). Then follow-up simple slopes analyses suggested that all patients across groups showed a significant symptomatic improvement after ketamine infusions (all p < 0.05), and patients with severe pain (across all domains of SF-MPQ) had greater improvement in depressive symptoms than those with mild pain or non-pain (all p < 0.05).

CONCLUSION

A significant and rapid improvement in depressive symptoms was observed in patients with depression and pain after ketamine treatment. Ketamine may be a novel and promising antidepressant preferentially for the therapy of depression with severe pain.