Ketamine for the Treatment of Chronic Pain: A Comprehensive Review

Arketamine: a scoping review of its use in humans

Arketamine (R-ketamine), an enantiomer of ketamine, has historically been less studied than esketamine (S-ketamine) and the racemic mixture. Recent preclinical studies suggest that arketamine may offer prolonged antidepressant effects and a superior safety profile. This scoping review aims to assess and synthesise existing literature on the clinical use of arketamine in humans. This review follows the PRISMA for Scoping Reviews guidelines, with a comprehensive search conducted in PubMed, Embase, ClinicalTrials.gov, and the WHO International Clinical Trials Registry. Eligible studies included those reporting the administration of arketamine to humans. Data were extracted and synthesised descriptively. A total of 20 studies involving 410 subjects were included. Arketamine was primarily investigated for pain management and depression. While early evidence suggests arketamine may be effective in reducing pain, most studies were small and conducted in non-clinical settings. In psychiatry, trials indicate potential antidepressant effects, but results are inconsistent, and some studies remain unpublished. A consistent observation across most studies is arketamine's favourable safety profile, showing lower incidences of dissociative and psychotomimetic effects compared to esketamine and racemic ketamine. Arketamine may have a role in pain management and psychiatry, with a favourable safety profile compared to other forms of ketamine. However, the small scale of many studies limits the generalizability of findings, and results in depression trials are mixed. Larger, well-designed studies, possibly with higher doses, are needed to determine its therapeutic potential and establish its place in clinical practice.

Lumbar Sympathetic Block to Treat CRPS in an 18-Month-Old Girl: A Breaking Barriers Case Report and Review of Literature

BACKGROUND

Children under the age of 3 years have been diagnosed with complex regional pain syndrome (CRPS). They were found to be functionally disadvantaged and psychologically distressed in relation to children with other painful conditions.

CASE PRESENTATION

An 18-month-old baby girl was referred to the pain clinic with a history of severe right lower limb pain that had begun 2 months earlier. The parents were unable to recall any trauma before the painful situation. Pain and allodynia were severe and extended from the toes to the gluteus area. She was low weight for her age (6700 g). The patient was on the maximum doses of gabapentin and amitriptyline accepted for her body weight and did not have the possibility to start rehabilitation due to severe pain and allodynia. After discussing the risks and potential benefits of a planned lumbar sympathetic block (LSB), the parents approved the interventional procedure. This is the first case report describing the LSB technique at such a young age.

METHOD

A lumbar sympathetic block was carried on at the third lumbar vertebral level, fluoroscopy-guided, and under general anesthesia (GA) initiated with ketamine iv. A 4-cm needle was introduced using a tunneled vision approach in an oblique view at the L3 level until adequate depth was confirmed in the lateral position. Safety considerations were taken in relation to the radiation dose and all drugs injected with dose adjustment to her body weight. The block was successful (the skin temperature increased by 2.8 °C) and was uneventful. Pain and allodynia were completely alleviated in the recovery room. At the follow-up after 3 and 8 weeks, the parents reported an 80% improvement in pain and allodynia, a 70% improvement in sleep, a weight gain of 900 g, and that she had started rehabilitation.

CONCLUSIONS

Lumbar sympathetic blocks can be considered at a very young age to treat CRPS if other non-invasive measures fail.

Effects of a synergic interaction between magnesium sulphate and ketamine on the perioperative nociception in dogs undergoing tibial plateau leveling osteotomy: a pilot study

Introduction

Magnesium Sulphate (MgSO4) is commonly used in human medicine for the management of perioperative pain in different types of procedures. However, in veterinary medicine, the use of MgSO4 has not been evaluated for its analgesic efficacy in dogs, which has generated conflicts of opinion in this area of veterinary anesthesiology. The aim of this study was to evaluate the perioperative analgesic efficacy of MgSO4 in combination with Ketamine in dogs undergoing Tibial Plateau Leveling Osteotomy (TPLO). Our hypothesis is that MgSO4 plus ketamine have a synergistic action in the management of intra-and postoperative pain.

Methods

Twenty adult mixed breed dogs with average age 5.9 ± 2.6 years and weight 27.8 ± 9.2 kg were included in this prospective, clinical, randomized study. Dogs were randomly assigned to two groups. The MK group received ketamine (0.5 mg/kg as starting bolus followed by continuous infusion rate at 1 mg/kg/h). At the end of the ketamine bolus, MgSO4 (50 mg/kg over 15 min) was administered by the same route, followed by a constant rate infusion (CRI) at 15 mg/kg/h, IV. K group received a bolus of ketamine followed by a CRI at the same dosage described in MK group. Main cardiorespiratory parameters were recorded 10 min before the start of surgery (BASE), after the ketamine bolus (T1) and the MgSO4 bolus (T2), during the skin incision (SKIN), the osteotomy (OSTEOTOMY) and skin suturing (SUTURE). In the postoperative period, the short form of Glasgow Composite Pain scale (SF-CMPS) was used to assess pain at 30, 60, 120, and 180 min after extubation (Post30, Post60, Post120, and Post180, respectively). The main blood electrolytes (Mg2+, Ca2+, Na+, K+) were analyzed at BASE, T2, OSTEOTOMY, SUTURE and T3 (one hour after stopping MgSO4 infusion). Number of rescue analgesia and administration times were recorded both in the intra-and postoperative period.

Results

In K group 7 out of 10 dogs required intraoperatory rescue analgesia compared to MK group (3/10). Furthermore, mean arterial pressure (MAP) and heart rate (HR) were significantly higher at OSTEOTOMY compared to BASE time in both groups. In the postoperative period, at T120, ICMPS-SF score was higher in K group than MK group.

Conclusion

The administration of MgSO4 could guarantee better analgesia in the perioperative period in dogs undergoing TPLO, performing a synergistic action with ketamine.

Psychedelic Therapy: A Primer for Primary Care Clinicians-Ketamine

BACKGROUND

Ketamine, an arylcyclohexylamine dissociative anesthetic agent, has evolved into a versatile therapeutic. It has a rapid-onset, well-understood cardiovascular effects and a favorable safety profile in clinical use. Its enantiomeric compound, esketamine, was approved by the Food and Drug Administration in 2019 for both treatment-resistant depression and major depressive disorder with suicidal ideation.

AREAS OF UNCERTAINTY

Research indicates dose-dependent impacts on cognition, particularly affecting episodic and working memory following both acute administration and chronic use, albeit temporarily for the former and potentially persistent for the latter. Alongside acute risks to cardiovascular stability, ketamine use poses potential liver toxicity concerns, especially with prolonged or repeated exposure within short time frames. The drug's association with "ketamine cystitis," characterized by bladder inflammation, adds to its profile of physiological risks.

THERAPEUTIC ADVANCES

Data demonstrate a single intravenous infusion of ketamine exhibits antidepressant effects within hours (weighted effect size averages of depression scores (N = 518) following a single 0.5 mg/kg infusion of ketamine is d = 0.96 at 24 hours). Ketamine is also effective at reducing posttraumatic stress disorder (PTSD) symptom severity following repeated infusions (Clinician-Administered PTSD Scale scores: -11.88 points compared with midazolam control). Ketamine also decreased suicidal ideation in emergency settings (Scale for Suicidal Ideation scores: -4.96 compared with midazolam control). Through its opioid-sparing effect, ketamine has revolutionized postoperative pain management by reducing analgesic consumption and enhancing recovery.

LIMITATIONS

Many studies indicate that ketamine's therapeutic effects may subside within weeks. Repeated administrations, given multiple times per week, are often required to sustain decreases in suicidality and depressive symptoms.

CONCLUSIONS

Ketamine's comprehensive clinical profile, combined with its robust effects on depression, suicidal ideation, PTSD, chronic pain, and other psychiatric conditions, positions it as a substantial contender for transformative therapeutic application.

Association between niacin intake and knee osteoarthritis pain and function: a longitudinal cohort study

BACKGROUND

This research investigates the relationship between niacin intake and knee osteoarthritis (OA) severity, focusing on pain and functional ability due to niacin's role as a NAD(P)+ precursor, promoting cellular energy, and offering anti-inflammatory, analgesic, and antioxidant effects.

METHODS

The population-based Osteoarthritis Initiative (OAI) cohort with radiographically confirmed knee OA was analyzed through a Food Frequency Questionnaire determining niacin intake and scores from the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), using generalized additive mixed models.

RESULTS

A significant correlation was pinpointed in 2375 OA patients (1001 men and 1374 women; 55.96% aged between 45 and 65 and 44.04% aged ≥65) between niacin intake and reduced knee pain and functional degrees after a 48-month follow-up, evident in improved KOOS and WOMAC scores (P < 0.05). The fully adjusted models estimated a decrease of 0.26 points for every additional 1 unit of Ln-niacin intake of daily niacin intake on the WOMAC pain subscale, 0.83 points on the WOMAC function subscale, and an increase of 1.71 and 1.58 on the KOOS pain and quality of life score. Strikingly, subgroups including middle-aged individuals, women, white race, obese individuals, and those with specific dietary habits showed a more substantial improvement with increased niacin.

CONCLUSION

The association between increased niacin intake and reduced pain and function scores, as well improved quality of life in knee OA patients, is significant. Certain cohorts, according to a stratified analysis, could see more considerable benefits with increased niacin consumption.

HIGHLIGHTS

• Increased niacin intake is linked to reduced knee pain and better function in OA patients. • Specific subgroups, such as middle-aged individuals, women, and those with certain dietary habits, benefit more from increased niacin consumption. • Niacin shows promise for enhancing the quality of life in knee OA patients by reducing pain and improving function.

Ketamine in Chronic Pain: A Review

Ketamine has been used in the treatment of several pain syndromes, particularly those with a relevant neuropathic component. Sub-anesthetic doses of ketamine produce a potent analgesic effect, due to its inhibition of N-methyl-D-aspartate receptors and enhancement of descending inhibitory pathways. Its short-term analgesic effect is well-documented perioperatively, with an associated reduction in postoperative chronic pain and opioid consumption. Despite some evidence regarding its long-term benefits, the number of clinical studies is still limited. In addition to its analgesic effects, ketamine also possesses an anti-depressive action, which might be useful in the treatment of chronic pain patients. Several side effects have been described, the psychomimetic ones being the most relevant due to their impact on treatment adhesion. At present, co-administration of ketamine and benzodiazepines or α2-agonists facilitates its clinical application. Despite current evidence and increasing use, further investigation is still needed regarding its long-term safety profile and clearer risk-benefit analysis.

How to treat chronic pain in rheumatic and musculoskeletal diseases (RMDs) - A pharmacological review

INTRODUCTION

Chronic pain is a common symptom of rheumatic diseases that impacts patients' quality of life. While non-pharmacological approaches are often recommended as first-line treatments, pharmacological interventions are important for pain management. However, the effectiveness and safety of different pharmacological treatments for chronic pain in rheumatic diseases are unclear.

METHODS

This review critically synthesizes the current evidence base to guide clinicians in selecting appropriate pharmacological treatments for their patients, considering the expected benefits and potential risks and side effects.

RESULTS

For osteoarthritis, nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, opioids, and antidepressants are commonly used, with NSAIDs being the most recommended. In addition, topical agents, such as topical NSAIDs, are recommended for localized pain relief. For fibromyalgia, amitriptyline, serotonin and noradrenaline reuptake inhibitors (SNRIs), and gabapentinoids are commonly used, with SNRIs being the most recommended. For back pain, nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, opioids are used only for acute of flare-up pain, whereas neuropathic pain drugs are only used for chronic radicular pain. For inflammatory rheumatic diseases, disease-modifying antirheumatic drugs (DMARDs) and biological agents are recommended to slow disease progression and manage symptoms.

CONCLUSION

While DMARDs and biological agents are recommended for inflammatory rheumatic diseases, pharmacological treatments for other rheumatic diseases only alleviate symptoms and do not provide a cure for the underlying condition. The use of pharmacological treatments should be based on the expected benefits and evaluation of side effects, with non-pharmacological modalities also being considered, especially for fibromyalgia.

Maintenance IV Ketamine Therapy in the Fibromyalgia Patient: A Case Report

Introduction

Fibromyalgia is a complex disorder characterized by distributed and persistent pain often associated with fatigue and depression. The underlying causal agents of this dysfunction are not clear. Ketamine has been used to treat chronic pain in a variety of pain syndromes, including fibromyalgia, but the dosing protocols used are neither standardized nor consistent across cases. The current case presents an opportunity to contribute to a progression towards a consensus on ketamine dosing for fibromyalgia.

Case Presentation

A 60-year-old female presented with indications of fibromyalgia and was administered a 9-session IV ketamine treatment for pain. The initial dosing was 50 mg, with a concentration of 1.0 mg/ml at an infusion rate of 0.8 mg/kg/hr. This was increased to 200 mg and eventually to 240 mg, maintaining a ketamine concentration 4.0-4.8 mg/ml at an infusion rate of 1.5 mg/kg/hr.

Management and Outcomes

Following the first 9-session therapy, the patient reported >50% pain relief from pre-infusion levels and was placed on a maintenance regimen in perpetuity. This regimen involves two monthly IV ketamine infusions, one day apart for two hours at a maintenance rate of 4.8 mg/kg/hr.

Conclusion

Ketamine by IV is an effective option for pain management in patients with fibromyalgia. Compared to previous case studies, it is recommended that increased total dose, frequent administration, and longer duration of infusions all may be necessary for ketamine to maximize its beneficial effects.

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.

Outpatient Ketamine Infusions for the Treatment of Fibromyalgia and Chronic Pain Syndrome: A Case Report

Intravenous (IV) ketamine has demonstrable efficacy for chronic pain management. Its use in an outpatient setting has provided relief from myriad pain syndromes and additionally may reduce dependence on opioids. Nevertheless, its long-term ability to provide these benefits is understudied. Here, we present the case of a 68-year-old female who presented to our clinic with persistent fibromyalgia, accompanied by other pain symptoms that had been recalcitrant to traditional pain management therapy including nerve blocks, ablations, spinal cord stimulation, and morphine medication. We administered seven increasing IV ketamine doses over two weeks. The patient reported significant, widespread pain relief. The patient continued to receive IV ketamine twice weekly for over a year and remains on this schedule. Pain relief has persisted under this regimen, along with a demonstrable improvement in quality of life, a reduced use of morphine, and the cessation of anti-depressant medication. This case indicates that long-term ketamine infusions show promise for chronic pain management and that more longitudinal studies on this treatment are warranted.

Novel Drug Targets and Emerging Pharmacotherapies in Neuropathic Pain

Neuropathic pain is a debilitating condition characterized by abnormal signaling within the nervous system, resulting in persistent and often intense sensations of pain. It can arise from various causes, including traumatic nerve injury, neuropathy, and certain diseases. We present an overview of current and emerging pharmacotherapies for neuropathic pain, focusing on novel drug targets and potential therapeutic agents. Current pharmacotherapies, including tricyclic antidepressants, gabapentinoids, and serotonin norepinephrine re-uptake inhibitors, are discussed, as are emerging treatments, such as ambroxol, cannabidiol, and N-acetyl-L-cysteine. Additionally, the article highlights the need for further research in this field to identify new targets and develop more effective and targeted therapies for neuropathic pain management.

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.

Emerging roles of GPR109A in regulation of neuroinflammation in neurological diseases and pain

Neuroinflammation plays a critical role in the pathological process of multiple neurological disorders and pathological pain conditions. GPR109A, a Gi protein-coupled receptor, has emerged as an important therapeutic target for controlling inflammation in various tissues and organs. In this review, we summarized current data about the role of GPR109A in neuroinflammation. Specifically, we focused on the pharmacological features of GPR109A and signaling pathways used by GPR109A to ameliorate neuroinflammation and symptoms in Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, and pathological pain conditions.

The Effectiveness of Ketamine Versus Opioids in Patients With Acute Pain in the Emergency Department: A Systematic Review and Meta-Analysis

Opioids are the mainstay of treatment for acute pain in the emergency department. However, its misuse led to the investigation of alternative effective analgesic options for acute pain complaints such as ketamine. Therefore, this systematic review and meta-analysis aimed to determine the effectiveness of ketamine in comparison to opioids in the management of acute pain. This was a systematic review and meta-analysis of randomized controlled trials comparing ketamine to opioids for the relief of acute pain in the ED. Eligible studies were identified by searching the following electronic databases: Medline, Embase, and Central. Studies utilizing either the visual analog scale (VAS) or the numeric rating scale (NRS) for pain scoring in ketamine vs opioids were included. The revised Cochrane risk-of-bias tool for randomized trials was utilized. A random-effects model was performed, and all outcomes were pooled by the inverse variance weighting method. The total number of studies that met the criteria of systematic reviews was nine of which seven of them were included in the meta-analysis with 789 participants. The overall effect of NRS trials was the standardized mean difference (SMD) = -0.07, 95% confidence interval (CI) -0.31 to 0.17, P-value = 0.56, I² =85%. While VAS trials showed an overall effect of SMD = -0.02, 95% CI -0.22 to 0.18, P = 0.84, I² = 59%). Moreover, higher adverse events were reported in opioids; however, this was not statistically significant (SMD = 1.23, 95% CI 0.93-1.64, P = 0.15, I2 =38%). Ketamine for immediate pain relief at 15 minutes could be an effective alternative to opioids, but its overall effect in comparison to opioids for improving the pain has not shown a statistically significant difference. There was high heterogeneity in the included studies; thus, a sub-group analysis was performed.

Pharmacological Management of Neuropathic Pain after Radiotherapy in Head and Neck Cancer Patients: A Systematic Review

Background: Neuropathic pain (NP) in head and neck cancer (HNC) patients represents a treatment challenge. Most studies investigating drugs against NP are conducted in patients suffering with diabetic neuropathy or postherpetic neuralgia, while data are limited in cancer pain management. Additionally, regarding cancer therapy-related NP, most of the studies do not focus on HNC patients. The aim of this review is to identify the studies on systematically administered medication for NP management that included HNC patients under radiotherapy. Methods: A systematic literature search was performed, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, in PubMed, Cochrane Library, Web of Science and ClinicalTrials.gov on 30 October 2021. The medical subject heading (MeSH) terms were (“head and neck cancer” OR “tumor”) AND “neuropathic pain” AND “medication” AND “radiotherapy.” The Cochrane Collaboration tool was used for quality assessment. Results: The search identified 432 articles. Three more articles were identified after searching the reference lists of the retrieved articles. A total of 10 articles met the eligibility inclusion criteria and were included in this review; 6 on gabapentin, 1 on pregabalin, 1 on nortriptyline, 1 on methadone, and 1 on ketamine. Statistically significant results in pain reduction compared to placebo or standard pain medication were found in the studies on pregabalin (p = 0.003), methadone (p = 0.03), ketamine (p = 0.012), and in two out of six gabapentin studies (p < 0.004). Two of the studies (both concerning gabapentin) had no comparison arm. Conclusions: Treatments including pregabalin, methadone, ketamine, and gabapentin were found to provide pain relief against HNC NP. While there is a plethora of pharmacological treatments available for the management of NP, only a few studies have been conducted regarding the pharmacological management of therapy-related NP in HNC patients. More studies should be conducted regarding the pharmacological approaches in HNC therapy-related NP so that specific treatment algorithms can be developed.

Post-thoracotomy Pain Syndrome

PURPOSE OF REVIEW

This article reviews PTPS demographics, diagnosis, pathophysiology, surgical and anesthetic techniques, and their role in preventing PTPS along with updated treatment options.

RECENT FINDINGS

Post-thoracotomy pain syndrome (PTPS) can be incapacitating. The neuropathic type pain of PTPS is along the incision site and persists at least 2 months postoperatively. There is a wide reported range of prevalence of PTPS. There are several risk factors that have been identified including surgical technique and younger age. Several surgical and anesthetic techniques have been trialed to reduce pain after thoracotomy. Multimodal pain control is the suggested long-term treatment plan for patients with PTPS. There are several factors that can be modified to reduce pain and incidence of PTPS during the perioperative period and the use of multimodal analgesia is suggested for the treatment of PTPS.