Ketamine for Pain: An Update of Uses in Palliative Care

Adeno-associated virus-mediated gene transfer of arginine decarboxylase to the central nervous system prevents opioid analgesic tolerance

Agmatine, a decarboxylated form of L-arginine, prevents opioid analgesic tolerance, dependence, and self-administration when given by both central and systemic routes of administration. Endogenous agmatine has been previously detected in the central nervous system. The presence of a biochemical pathway for agmatine synthesis offers the opportunity for site-specific overexpression of the presumptive synthetic enzyme for local therapeutic effects. In the present study, we evaluated the development of opioid analgesic tolerance in ICR-CD1 mice pre-treated with either vehicle control or intrathecally delivered adeno-associated viral vectors (AAV) carrying the gene for human arginine decarboxylase (hADC). Vehicle-treated or AAV-hADC-treated mice were each further divided into two groups which received repeated delivery over three days of either saline or systemically-delivered morphine intended to induce opioid analgesic tolerance. Morphine analgesic dose-response curves were constructed in all subjects on day four using the warm water tail flick assay as the dependent measure. We observed that pre-treatment with AAV-hADC prevented the development of analgesic tolerance to morphine. Peripheral and central nervous system tissues were collected and analyzed for presence of hADC mRNA. In a similar experiment, AAV-hADC pre-treatment prevented the development of analgesic tolerance to a high dose of the opioid neuropeptide endomorphin-2. Intrathecal delivery of anti-agmatine IgG (but not normal IgG) reversed the inhibition of endomorphin-2 analgesic tolerance in AAV-hADC-treated mice. To summarize, we report here the effects of AAV-mediated gene transfer of human ADC (hADC) in models of opioid-induced analgesic tolerance. This study suggests that gene therapy may contribute to reducing opioid analgesic tolerance.

Ketamine subcutaneous continuous infusion for non-cancer neuropathic pain at home: a case report

OBJECTIVE

Ketamine is a drug that can effectively treat neuropathic pain by blocking the N-methyl-D-aspartate receptor. It has been studied as a supplement to opioids for cancer pain, but its effectiveness for non-cancer pain is still limited. However, despite its usefulness in managing refractory pain, ketamine is not commonly used for home-based palliative care.

METHODS

A case report of a patient with severe central neuropathic pain who was treated with a subcutaneous continuous infusion of morphine and ketamine at home.

RESULTS

The introduction of ketamine in the patient's treatment plan effectively controlled pain. Only one possible ketamine side effect was observed and easily treated with pharmacological and non-pharmacological measures.

CONCLUSIONS

We have found success in using subcutaneous continuous infusion of morphine and ketamine to alleviate severe neuropathic pain in a home setting. We also observed a positive impact on the patient's family members' personal, emotional and relational well-being after ketamine was introduced.

Ketamine for Super-Refractory Status Epilepticus in Palliative Care. A Case Report and Review of the Literature

We report a case of super refractory status epilepticus uncontrolled by multiple anti-seizure medications in an individual with acute liver failure due to hepatic cirrhosis and an obstructive ileocecal mass plus multiple bilateral lung lesions presumed to be metastatic. A ketamine infusion was initiated late in his hospitalization which eliminated the convulsive seizures in less than an hour. The abatement of convulsive seizures allowed his grieving wife to return to her husband's bedside to witness the withdrawal of life sustaining treatment and be present during the final 24 hours of his life. We review the medical literature on the role of Intravenous (IV) Ketamine in the treatment of super refractory status epilepticus.

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.

Role of the mesolimbic dopamine pathway in the antidepressant effects of ketamine

Depression is a complex and highly heterogeneous disorder which diagnosis is based on an exceedingly variable set of clinical symptoms. Current treatments focus almost exclusively on the manipulation of monoamine neurotransmitter systems, but despite considerable efforts, these remain inadequate for a significant proportion of those afflicted by the disorder. The emergence of racemic (R, S)-ketamine as a fast-acting antidepressant has provided an exciting new path for the study of major depressive disorder (MDD) and the search for better therapeutics for its treatment. Previous work suggested that ketamine's mechanism of action is primarily mediated via blockaded of N-methyl-d-aspartate (NMDA) receptors, however, this is an area of active research and clinical and preclinical evidence now indicate that ketamine acts on multiple systems. The last couple of decades have cemented the mesolimbic dopamine reward pathway's involvement in the pathogenesis of MDD and related mood disorders. Exposure to negative stress dysregulates dopamine neuronal activity disrupting reward and motivational processes resulting in anhedonia (lack of pleasure), a hallmark symptom of depression. Although the mechanism(s) underlying ketamine's antidepressant activity continue to be elucidated, current evidence indicate that its therapeutic effects are mediated, at least in part, via long-lasting synaptic changes and subsequent molecular adaptations in brain regions within the mesolimbic dopamine system. Notwithstanding, ketamine is a drug of abuse, and this liability may pose limitations for long term use as an antidepressant. This review outlines the current knowledge of ketamine's actions within the mesolimbic dopamine system and its abuse potential. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

A Phase II, Open-Label Clinical Trial of Intranasal Ketamine for Depression in Patients with Cancer Receiving Palliative Care (INKeD-PC Study)

Antidepressants require several weeks for the onset of action, a lag time that may exceed life expectancy in palliative care. Ketamine has demonstrated rapid antidepressant effects, but has been minimally studied in cancer and palliative care populations. Herein, the objective was to determine the feasibility, safety, tolerability and preliminary efficacy of intranasal racemic ketamine for major depressive disorder (MDD) in patients with advanced cancer. We conducted a single-arm, open-label phase II trial at the Princess Margaret Cancer Centre in Toronto, ON, Canada. Participants with advanced cancer with moderate to severe MDD received three flexible doses of intranasal (IN) ketamine (50−150 mg) over a one-week period. The primary efficacy outcome was an antidepressant response and remission rates as determined by the Montgomery−Åsberg Depression Rating Scale (MADRS) from baseline to the Day 8 primary endpoint. Twenty participants were enrolled in the trial, receiving at least one dose of IN ketamine, with fifteen participants receiving all three doses. The Day 8 antidepressant response (MADRS decreased by >50%) and remission (MADRS < 10 on Day 8) rates were high at 70% and 45%, respectively. Mean MADRS scores decreased significantly from baseline (mean MADRS of 31, standard deviation 7.6) to Day 8 (11 +/− 7.4) with an overall decrease of 20 points (p < 0.001). Antidepressant effects were partially sustained in the second week in the absence of additional ketamine doses, with a Day 14 mean MADRS score of 14 +/− 9.9. Common adverse effects included fatigue, dissociation, nausea, dysgeusia and headaches; almost all adverse effects were mild and transient, resolving within 2 h of each ketamine dose with one dropout related to adverse effects (negative dissociative episode). Given these promising findings, larger, controlled trials are merited.

Augmented Package of Palliative Care for Women With Cervical Cancer: Responding to Refractory Suffering

The essential package of palliative care for cervical cancer (EPPCCC), described elsewhere, is designed to be safe and effective for preventing and relieving most suffering associated with cervical cancer and universally accessible. However, it appears that women with cervical cancer, more frequently than patients with other cancers, experience various types of suffering that are refractory to basic palliative care such as what can be provided with the EPPCCC. In particular, relief of refractory pain, vomiting because of bowel obstruction, bleeding, and psychosocial suffering may require additional expertise, medicines, or equipment. Therefore, we convened a group of experienced experts in all aspects of care for women with cervical cancer, and from countries of all income levels, to create an augmented package of palliative care for cervical cancer with which even suffering refractory to the EPPCCC often can be relieved. The package consists of medicines, radiotherapy, surgical procedures, and psycho-oncologic therapies that require advanced or specialized training. Each item in this package should be made accessible whenever the necessary resources and expertise are available.

Top Ten Tips Palliative Care Clinicians Should Know About Interventional Pain and Procedures

Pain is a common symptom for patients with advanced illness. Palliative care (PC) clinicians are experts in pharmacologic and nonpharmacologic treatment of pain and other symptoms for these patients. True multimodal pain control should include consideration of interventional procedures and pumps to improve difficult-to-manage pain. This article, written by clinicians with expertise in interventional pain and PC, outlines and explains many of the adjunctive and interventional therapies that can be considered for patients with pain in the setting of serious illness. Only by understanding and considering all available options can we ensure that our patients are receiving optimal care.

Multimodal imaging reveals transient liver metabolic disturbance and sinusoidal circulation obstruction after a single administration of ketamine/xylazine mixture

A ketamine/xylazine (K/X) mixture is widely used before and during experiments in rodents. However, the impact of short-term use of K/X mixture and its influences on data interpretation have rarely been discussed. In this study, we administered one shot of a K/X mixture and examined acute hepatic responses using biochemical analysis, histopathological examination, and non-invasive imaging to determine the delay required prior to further assessment of the liver to avoid confounding effects triggered by anaesthesia. After the K/X injection, aspartate aminotransferase (AST) in serum was significantly elevated from 3 to 48 h. Obstructed sinusoidal circulation lasting for 24 or 36 h was revealed by DCE-MRI and drug distribution analysis, respectively. Metabolic alterations were detected at 3 h by NMR analysis and FDG-PET. Moreover, ultrasonography showed that lipid droplet accumulation increased from 1 to 16 h and declined thereafter. Taken together, our findings show that the K/X mixture induces acute hepatotoxicity and metabolic disturbance, and these disturbances cause hemodynamical disorders in the liver. The required time interval for recovery from K/X impact was dependent on the chosen assay. It took at least 16 h for metabolic recovery and 36 h for recovery of sinusoidal circulation. However, the liver was not fully recovered from the injury within 48 h.

Midazolam: an essential palliative care drug

Midazolam is a commonly used benzodiazepine in palliative care and is considered one of the four essential drugs needed for the promotion of quality care in dying patients. Acting on the benzodiazepine receptor, it promotes the action of gamma-aminobutyric acid. Gamma-aminobutyric acid action promotes sedative, anxiolytic, and anticonvulsant properties. Midazolam has a faster onset and shorter duration of action than other benzodiazepines such as diazepam and lorazepam lending itself to greater flexibility in dosing than other benzodiazepines. The kidneys excrete midazolam and its active metabolite. Metabolism occurs in the liver by the P450 system. This article examines the pharmacology, pharmacodynamics, and clinical uses of midazolam in palliative care.

Low-dose ketamine adjuvant treatment for refractory pain in children, adolescents and young adults with cancer: a pilot study

OBJECTIVES

Ketamine, an N-methyl-D-aspartate receptor antagonist, is effective at relieving adult cancer pain, although there have been very few reports to date regarding its use in children and in adolescents and young adults (AYA). This study assessed the efficacy, safety and opioid-sparing effects of low doses of ketamine added to opioid analgesics to alleviate persistent cancer pain.

METHODS

This prospective, multicentre, observational trial collected data regarding demographics, pain characteristics, pain score assessment within the first 48 hours of ketamine administration, tolerance and satisfaction from 38 patients aged 2-24 years prescribed with ketamine as an adjuvant antalgic for refractory cancer pain in 10 French paediatric oncology centres.

RESULTS

The mean visual analogue scale pain score decreased from 6.7 to 4.3 out of 10 (n=39, p<0.001) from day 1 to day 3 and by at least 2 points in 56% of the patients (n=22) 48 hours after initiation of ketamine. Nine patients experienced poor tolerance (≥2 side effects), all with infusion rates lower than 0.05 mg/kg/hour. None had limiting toxicities. An opioid-sparing effect was highlighted in four patients. Fifty-four per cent of the prescribers and 47% of the patients found the addition of ketamine 'very helpful'.

CONCLUSIONS

Low doses of ketamine as an adjuvant to opioids significantly reduced the intensity of pain in half of the study population. A tendency towards better pain control is shown, although a lack of statistical power somewhat limits our conclusions, especially in children. Nevertheless, ketamine may be a useful option for improving the treatment of refractory pain in children and AYA with cancer.

The Efficacy of Ketamine in the Palliative Care Setting: A Comprehensive Review of the Literature

Background: Previous literature suggests that ketamine may be an effective drug in the palliative care population as this drug has been shown to treat multiple conditions that are common in these patients. Objective: This review examines the efficacy of ketamine for the treatment of depression and physical pain in palliative care patients. Methods: Eleven studies were included on the topic of ketamine as an antidepressant in the palliative care population. Additionally, 5 RCT studies were included on the topic of physical pain in this population. Results: All 11 studies, including one RCT, found antidepressant effects of ketamine in this patient population. Ketamine's effect on treating physical pain was mixed with the largest and most recent RCTs suggesting no significant analgesic effect. Discussion: This review suggests that starting qualified patients on intravenous (IV) ketamine and switching to oral or intranasal administration may be the most effective and convenient for treating depression, especially for patients who wish to receive treatment at home. Significant analgesia was found in patients who received epidural or intrathecal ketamine as well as in one study using intravenous administration. More research is necessary to determine which palliative care patients may benefit from ketamine treatment.

Top Ten Tips Palliative Care Clinicians Should Know About Psychopharmacology

Palliative care (PC) providers often prescribe psychotropic medications to address psychological and physical suffering of patients with serious medical illness. Consideration must be given to the significant medical comorbidities of the patient when selecting a medication. This article seeks to provide guidance on how to safely and effectively select a psychotropic agent for depression, anxiety, and other distressing symptoms for patients with serious illness. To do so, we draw upon a team of physicians and a pharmacist with training in psychiatry and PC to highlight the "Top 10" tips for selecting a psychotropic medication to provide relief for patients with serious medical illness.

Donor Hepatectomy Surgery using Ketamine to Compliment Analgesia and Reduce Morbidity - a Retrospective Chart Review Investigation

Objective

Inferior and limited analgesic options/techniques during living donor hepatectomy surgery can result in pain and risks of morbidity, opioid-related adverse events (AEs), predisposition to the development of chronic pain and concerns of potential narcotic abuse. Traditional analgesia uses unimodal intravenous opioids that can cause significant side effects. Ketamine provides analgesia and may be opioid sparing, but use in living-donor hepatectomy has not been studied.

Methods

Following human investigation committee approval and informed written consent, 47 liver donor patients over a 5-year period scheduled for surgery were categorized into one of three groups: 24 patients received no ketamine (Group 1), 9 received only intraoperative ketamine (Group 2) and 14 patients received intraoperative plus postoperative ketamine (Group 3). Subjects had access to opioid patient-controlled analgesia (PCA). Chart reviews (including operating room and intensive care unit) were collected and analysed for morphine consumption, pain-intensity scores, opioid-sparing effects, AEs of analgesics and for evidence of ketamine side effects on donor hepatectomy patients.

Results

There were no differences in patient demographics. Living donor hepatectomy patients receiving intraoperative ketamine that was continued postoperatively consumed fewer morphine-equivalents and had lower median pain scores than subjects from the other two groups. Ileus occurred in those not receiving ketamine, pruritus was lowest in Group 3, and there was no evidence or reports of ketamine-associated AEs.

Conclusion

Perioperative ketamine for donor hepatectomy patients could safely provide improved analgesia and be opioid sparing when compared to PCA opioids alone, and there is no evidence of ketamine-related AEs at the dose and delivery methods described here during partial liver donation surgery.

Palliative care in gynecologic oncology

PURPOSE OF REVIEW

Patients with gynecologic malignancies face many difficult issues in the course of their diseases, ranging from physical symptoms to advance care planning in light of a poor prognosis. This review examines the evidence supporting integration of palliative care early in the course of disease and symptom management, and provides a framework for difficult conversations.

RECENT FINDINGS

Palliative care has been demonstrated to improve quality of life and promote survival if integrated early in the course of disease. An evidence-based approach should guide symptom management, such as pain and nausea. Advance care planning and goals of care discussions are enhanced by a framework guiding discussion and the incorporation of empathetic responses.

SUMMARY

Palliative care is a diverse multidisciplinary field that can provide significant benefit for patients with gynecologic malignancies.

Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Chronic Pain From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists

BACKGROUND

Over the past 2 decades, the use of intravenous ketamine infusions as a treatment for chronic pain has increased dramatically, with wide variation in patient selection, dosing, and monitoring. This has led to a chorus of calls from various sources for the development of consensus guidelines.

METHODS

In November 2016, the charge for developing consensus guidelines was approved by the boards of directors of the American Society of Regional Anesthesia and Pain Medicine and, shortly thereafter, the American Academy of Pain Medicine. In late 2017, the completed document was sent to the American Society of Anesthesiologists' Committees on Pain Medicine and Standards and Practice Parameters, after which additional modifications were made. Panel members were selected by the committee chair and both boards of directors based on their expertise in evaluating clinical trials, past research experience, and clinical experience in developing protocols and treating patients with ketamine. Questions were developed and refined by the committee, and the groups responsible for addressing each question consisted of modules composed of 3 to 5 panel members in addition to the committee chair. Once a preliminary consensus was achieved, sections were sent to the entire panel, and further revisions were made. In addition to consensus guidelines, a comprehensive narrative review was performed, which formed part of the basis for guidelines.

RESULTS

Guidelines were prepared for the following areas: indications; contraindications; whether there was evidence for a dose-response relationship, or a minimum or therapeutic dose range; whether oral ketamine or another N-methyl-D-aspartate receptor antagonist was a reasonable treatment option as a follow-up to infusions; preinfusion testing requirements; settings and personnel necessary to administer and monitor treatment; the use of preemptive and rescue medications to address adverse effects; and what constitutes a positive treatment response. The group was able to reach consensus on all questions.

CONCLUSIONS

Evidence supports the use of ketamine for chronic pain, but the level of evidence varies by condition and dose range. Most studies evaluating the efficacy of ketamine were small and uncontrolled and were either unblinded or ineffectively blinded. Adverse effects were few and the rate of serious adverse effects was similar to placebo in most studies, with higher dosages and more frequent infusions associated with greater risks. Larger studies, evaluating a wider variety of conditions, are needed to better quantify efficacy, improve patient selection, refine the therapeutic dose range, determine the effectiveness of nonintravenous ketamine alternatives, and develop a greater understanding of the long-term risks of repeated treatments.

Intravenous Low-Dose Ketamine Provides Greater Pain Control Compared to Fentanyl in a Civilian Prehospital Trauma System: A Propensity Matched Analysis

Objective: A few studies report comparable analgesic efficacy between low-dose ketamine and opioids such as morphine or fentanyl; however, limited research has explored the safety and effectiveness of intravenous low-dose ketamine as a primary analgesic in a civilian prehospital setting. The objective of this study is to compare pain control between low-dose ketamine and fentanyl when administered intravenously (IV) for the indication of severe pain. Methods: This was a retrospective, observational review of prehospital adult patients (≥18 years) who presented with severe pain (numeric rating scale, 7-10) and were treated solely with either low-dose ketamine IV or fentanyl IV between January 1, 2014 and December 31, 2016. Propensity matched analysis was performed adjusting for all baseline variables with p ≤ 0.10 and for baseline pain score to match ketamine and fentanyl patients on a one-to-one ratio. The primary outcome was change in pain score from baseline to after treatment and evaluated with a paired t-test. Secondary outcomes were changes in vital signs and Glasgow coma scale (GCS) from baseline to after treatment, as well as incidence of clinically significant adverse events (AEs); AEs were followed from scene arrival through emergency department discharge. Results: Propensity matched analysis produced 79 matched pairs. Ketamine IV patients, receiving a mean (SD) dose of 0.3 (0.1) mg/kg, showed a significantly larger mean decrease in pain after treatment, compared to the fentanyl IV patients (-5.5 (3.1) vs. -2.5 (2.4), p < 0.001). A significantly greater proportion of patients receiving ketamine IV achieved at least a 50% reduction in pain compared to those receiving fentanyl IV (67% vs. 19%, p < 0.001), marking 52 ketamine IV patients as responders to treatment. Vital signs demonstrated a nonsignificant decrease in blood pressure, respiratory rate, heart rate, and GCS. No clinically significant AEs were reported for patients receiving ketamine IV. Conclusion: The significant reduction in pain, significantly high proportion of ketamine responders, and the lack of clinically significant AEs characterizing patients receiving low-dose ketamine IV compared to fentanyl IV, all provide further support for its use as an effective prehospital analgesic. Level of Evidence: Level III, therapeutic.

Use of ketamine for acute suicidal ideation in a patient with chronic pain on prescribed cannabinoids

Ketamine is a standard anaesthetic drug that has been studied as a possible treatment for acute suicidal ideation. Aside to the potential psychotropic effects of ketamine, a Cochrane review reported that available studies suggest a modest effect of ketamine for chronic pain months to years after surgical intervention. We present a patient with acute suicidal ideation who required immediate inpatient psychiatric admission in the setting of concurrent chronic pain on cannabinoids which could not be prescribed within our inpatient hospital setting. This presented a clinical dilemma to rapidly reverse the patient’s suicidality while substituting the patient’s prescribed cannabinoid products with an alternative pain regimen. Since there is emerging support in the use of ketamine in suicidality and chronic pain, we administered ketamine while withholding cannabinoid products and found evidence to support its use in rapid reversal of suicidal ideation and temporary chronic pain relief.

Successful treatment of refractory cancer pain with morphine and ropivacaine: A case report

RATIONALE

Pain is one of the most common and distressing symptoms experienced by cancer patients. Cancer pain is a complex phenomenon with physical, psychological, social, and cognitive domains. Although opioids remain a cornerstone of cancer pain management, they are not effective in all patients. This case highlights the successful treatment of an opioid-refractory severe cancer pain crisis with ropivacaine infusion and subsequent rapid tapering of opioid dose.

PATIENT CONCERNS

This report illustrates the use of ropivacaine for cancer pain. A 62-year-old man with metastatic lung cancer was admitted to the hospital with uncontrolled chest-back and abdominal pain.

DIAGNOSES

The patient was diagnosed as refractory cancer pain.

INTERVENTIONS

Successful treatment with morphine and ropivacaine was performed to obtain longer opioid refractory severe cancer pain.

OUTCOMES

At 1, 3, and 6 months postoperative review, 70-75% relief of pain was achieved with overall activity was improved. The analgesic effect was stable during the 6-month follow-up period. No complications were reported during the follow-up period.

LESSONS

Our report demonstrates that ropivacaine is successful treatment for cancer pain in this case. It will supply us a novel navigation in cancer pain treatments. Meanwhile, this finding still needs additional study for confirmation.

Dose-response characteristics of intravenous ketamine on dissociative stereotypy, locomotion, sensorimotor gating, and nociception in male Sprague-Dawley rats

Clinicians administer subanesthetic intravenous (IV) ketamine infusions for treatment of refractory depression, chronic pain, and post-traumatic stress disorder in humans. However, ketamine is administered via the subcutaneous (SC) or intraperitoneal (IP) routes to rodents in most pre-clinical research, which may limit translational application. The present study characterized the dose-response of a subanesthetic IV ketamine bolus (2 and 5mg/kg) and 1-h infusion (5, 10, and 20mg/kg/h) on dissociative stereotypy, locomotion, sensorimotor gating, and thermal nociception in male Sprague-Dawley rats. The secondary aim was to measure ketamine and norketamine plasma concentrations following IV ketamine bolus at 1, 20, and 50min and at the conclusion of the 1-h infusion using liquid chromatography/mass spectrometry. The results showed that ketamine bolus and infusions produced dose-dependent dissociative stereotypy. Bolus (2 and 5mg/kg) and 20mg/kg/h infusion increased locomotor activity while 5mg/kg/h infusion decreased locomotor activity. Both 10 and 20mg/kg/h infusions reduced the acoustic startle reflex, while 5mg/kg bolus and 20mg/kg/h infusion impaired pre-pulse inhibition. Ketamine 5mg/kg bolus and the 10 and 20mg/kg/h infusions induced significant and prolonged antinociception to the hotplate test. Plasma concentrations of ketamine decreased quickly after bolus while norketamine levels increased from 1 to 20min and plateaued from 20 to 50min. The peak ketamine plasma concentrations [ng/ml] were similar between 5mg/kg bolus [4100] vs. 20mg/kg/h infusion [3900], and 2mg/kg bolus [1700] vs. 10mg/kg/h infusion [1500]. These results support the findings from previous ketamine injection studies and further validate the feasibility of administering subanesthetic doses of IV ketamine infusion to rats for neuropharmacological studies.

Successful Treatment of Opioid-Refractory Cancer Pain with Short-Course, Low-Dose Ketamine

Opioids remain the mainstay of treatment for severe cancer pain, but up to 20% of patients have persistent or refractory pain despite rapid and aggressive opioid titration, or develop refractory pain after long-term opioid use. In these scenarios, alternative agents and mechanisms for analgesia should be considered. This case report describes a 28-year-old man with metastatic pancreatic neuroendocrine cancer with severe, intractable pain despite high-dose opioids including methadone and a hydromorphone patient-controlled analgesia (PCA). After treatment with short-course, low-dose ketamine, his opioid requirements decreased by 99% and pain ratings by 50%, with the majority of this decrease occurring in the first 48 hours. As this patient's pain and opioid regimen escalated, he likely experienced some component of central sensitization and hyperalgesia. Administration of ketamine reduced opioid consumption by 99% and potentially "reset" neuronal hyperexcitability and reduced pain signaling, allowing for improved pain control.

Advances in topical analgesics

PURPOSE OF REVIEW

The recent increase in opioid consumption in the modern world prompted pain physicians to find new and improved solutions to tackle chronic, refractory pain syndromes. Topical analgesics are emerging as a valued multimodal analgesic arm in the fight against chronic pain.

RECENT FINDINGS

New and improved topical formulations have emerged as effective tools to treat chronic refractory pain. In addition to formulations manufactured by the pharmaceutical industry, there has been a recent interest in mixed topical products by local, regional and national compounding pharmacies. This review will focus on advances in topical analgesics, especially their role as an effective analgesic in nociceptive and neuropathic refractory pain states. We will explore topical analgesics' mechanisms of action and their efficacy as opioid-sparing formulations.

SUMMARY

This review will allow physicians to understand the role of topical agents in the treatment of intractable pain syndromes. Increasing medical providers' familiarity with these agents will allow their incorporation as part of a complex analgesic regimen for an improved pain management plan benefiting the patient population at large.

An assessment of the anti-fatigue effects of ketamine from a double-blind, placebo-controlled, crossover study in bipolar disorder

BACKGROUND

Fatigue is a multidimensional condition that is difficult to treat with standard monoaminergic antidepressants. Ketamine, an N-methyl-D-aspartate receptor (NMDAR) antagonist produces rapid and robust improvements in depressive symptoms in treatment-resistant depression. However, there is a dearth of literature examining the anti-fatigue effects of ketamine. We hypothesize that ketamine will rapidly improve fatigue symptoms in treatment-resistant depressed patients.

METHODS

This is an exploratory analysis of data obtained from two double-blind, randomized, placebo-controlled, crossover trials. A total of 36 participants with treatment-resistant bipolar I or II disorder in a depressive episode (maintained on therapeutic levels of lithium or valproate) received a single infusion of ketamine hydrochloride intravenously (0.5 mg/kg over 40 min) or placebo. A post-hoc analysis compared fatigue scores on ketamine vs. placebo at 10 time points from baseline through 14 days post-treatment using the National Institute of Health-Brief Fatigue Inventory.

RESULTS

A linear mixed model showed that ketamine significantly lowered fatigue scores compared to placebo from 40 min post-treatment to Day 14 with the exception of Day 7. The largest difference in anti-fatigue effects between placebo and ketamine was at day 2 (d=0.58, p<0.05). The effect remained significant after controlling for changes in non-fatigue depressive symptoms.

LIMITATION

The retrospective nature and a small sample size are study limitations.

CONCLUSIONS

Ketamine rapidly improved fatigue relative to placebo in a group of individuals with treatment-resistant bipolar depression. NMDAR is a glutamate receptor; hence, glutamate may represent a valuable target to study the clinical efficacy of new anti-fatigue approaches in multiple disorders.

Treatment of Neuropathic Pain

OPINION STATEMENT

Neuropathic pain is notoriously variable in its severity and impact on patients, as well as in its response to treatment. Certain therapies for neuropathic pain have better evidence for their use; however, it is apparent that although some therapies provide relief for only a minority of patients, the relief may be significant. Without a trial of therapy, there is no way to know if that relief is achievable. Our treatment experiences have shown that occasionally unexpected benefit is obtained through a thorough investigation of all options, even in the setting of failure of those with the most compelling evidence or indication. Chronic neuropathic pain is generally best treated with regularly dosed medications, balancing efficacy and tolerability. Evidence supports first-line trials of anticonvulsants, tricyclic antidepressants, and serotonin-norepinephrine reuptake inhibitors, alone or in certain combinations. While opioid medications, particularly methadone, can be effective in treating neuropathic pain, they are best used only in refractory cases and by experienced clinicians, due to concerns for both short- and long-term safety. Some therapies have a long history of successful use for certain syndromes (e.g., carbamazepine for trigeminal neuralgia pain), but these should not be considered to the exclusion of other more recent, less-supported therapies (e.g., botulinum toxin A for the same), particularly in refractory cases. We find the principles of palliative care highly applicable in the treatment of chronic neuropathic pain, including managing expectations, mutually agreed-upon meaningful outcomes, and a carefully cultivated therapeutic relationship.

Low-Dose Ketamine in Chronic Critical Illness

We report a case series on the observed effects of low-dose ketamine infusions in 4 critically ill patients with varying complications related to prolonged critical illness. Doses of ketamine infusion ranged from 0.5 to 4 μg/kg/min. A low-dose ketamine infusion was used to reduce agitation in a patient requiring high doses of sedatives and analgesics. In a second patient, ketamine improved depression and anxiety symptoms. In a third patient, ketamine may have facilitated liberation from mechanical ventilation. In a fourth patient, ketamine was used for palliation to avoid lethargy. Ketamine may be considered to help decrease agitation, manage pain, facilitate opioid and benzodiazepine withdrawal, prevent respiratory depression, and potentially manage depression and anxiety in chronically critically ill patients.

Understanding the cancer pain experience

Cancer pain management is a major element of successful cancer survivorship. Regardless of where someone is along the cancer experience, from a newly diagnosed patient to long-term survivor, pain is a potential treatment-related effect that can have a significant impact on a survivor's life. Quality pain management for cancer survivors is complicated by the fact that cancer-related pain can be due to the tumor, surgery, radiation, and/or chemotherapy. Additionally, the pain experience is related to many psychosocial/spiritual factors. Despite almost 40 years of attention devoted to improving cancer pain management, many cancer survivors are less than optimally treated, often owing to survivor and healthcare provider knowledge barriers. This article reviews some of the latest research related to cancer pain management treatment options, measurement/assessment, and interventions. Progress has been made in understanding new aspects of the pain experience, but more work is yet to be done.

Recent insights into the mode of action of memantine and ketamine

The clinical benefits of the glutamate receptor antagonists memantine and ketamine have helped sustain optimism that glutamate receptors represent viable targets for development of therapeutic drugs. Both memantine and ketamine antagonize N-methyl-D-aspartate receptors (NMDARs), a glutamate receptor subfamily, by blocking the receptor-associated ion channel. Although many of the basic characteristics of NMDAR inhibition by memantine and ketamine appear similar, their effects on humans and to a lesser extent on rodents are strongly divergent. Some recent research suggests that preferential inhibition by memantine and ketamine of distinct NMDAR subpopulations may contribute to the drugs' differential clinical effects. Here we review studies that shed light on possible explanations for differences between the effects of memantine and ketamine.

Ketamine PCA for treatment of end-of-life neuropathic pain in pediatrics

Control of neuropathic pain (NP) for children at end of life is challenging. Ketamine improves control of NP, but its use in children is not well described. We describe a retrospective case review of 14 children with terminal prognoses treated with ketamine patient-controlled analgesia (PCA) for management of opioid-refractory NP at the end of life. Median ketamine dose was 0.06 mg/kg/h (range 0.014-0.308 mg/kg/h) with a 0.05 mg/kg (range 0.03-0.5mg/kg) demand dose available every 15 minutes (range 10-60 minutes). All patients noted subjective pain relief with ketamine, and 79% had no adverse effects. Benzodiazepines limited neuropsychiatric side effects. Ketamine treatment arrested dose escalation of opioids in 64% of patients, and 79% were discharged to home hospice. Ketamine PCA is an effective, well-tolerated therapy for opioid-refractory NP in pediatric end-of-life care.

Brief review: Neuraxial analgesia in refractory malignant pain

PURPOSE

This narrative review aims to inform health care practitioners of the current literature surrounding the use of intrathecal (IT) and epidural analgesia in cancer patients with refractory pain at end of life. Topics discussed and reviewed include: patient selection, treatment planning, procedure, equipment, medications, complications, policies and procedures, as well as directions for future research.

PRINCIPAL FINDINGS

Cancer pain is inadequately treated in an estimated 10% of patients with malignant pain despite the implementation of the World Health Organization three-step analgesic ladder. This has prompted some to advocate for the addition of a fourth step that would include neuraxial interventions. There is moderate evidence supporting the safety and efficacy of IT drug therapy in cancer patients with refractory pain. A detailed assessment and interdisciplinary team approach is necessary to develop and implement care plans for patients requiring neuraxial analgesia. Neuraxial analgesia can significantly improve pain and reduce side effects, but this must be balanced against the increased complexity of care and the risk of uncommon but serious complications.

CONCLUSION

Neuraxial drug delivery gives clinicians more options to manage refractory pain at end of life and should be offered to patients with intractable cancer pain. Teams should be interprofessional with clear delineation of roles and responsibilities. They should discuss advanced discharge planning with the patient prior to implantation as well as provide on-call support.

Whole-cell patch-clamp analysis of recombinant NMDA receptor pharmacology using brief glutamate applications

N-methyl-D-aspartate receptors (NMDARs) are ionotropic glutamate receptors that are essential for synaptic plasticity, learning and memory. Dysfunction of NMDARs has been implicated in many nervous system disorders; therefore, pharmacological modulation of NMDAR activity has great therapeutic potential. However, given the broad physiological importance of NMDARs, modulating their activity often has detrimental side effects precluding pharmaceutical use of many NMDAR modulators. One approach to possibly improve the therapeutic potential of NMDAR modulators is to identify compounds that modulate subsets of NMDARs. An obvious target for modulating NMDAR subsets is the many NMDAR subtypes produced through different combinations of NMDAR subunits. With seven identified genes that encode NMDAR subunits, there are many neuronal NMDAR subtypes with distinct properties and potentially differential pharmacological sensitivities. Study of NMDAR subtype-specific pharmacology is complicated in neurons, however, because most neurons express at least three NMDAR subtypes. Thus, use of an approach that permits study in isolation of a single receptor subtype is preferred. Additionally, the effects of drugs on agonist-activated responses typically depend on duration of agonist exposure. To evaluate drug effects on synaptic transmission, an approach should be used that allows for activation of receptor responses as brief as those observed during synaptic transmission, both in the absence and presence of drug. To address these issues, we designed a fast perfusion system capable of (1) delivering brief (~5 ms) and consistent applications of glutamate to recombinant NMDARs of known subunit composition, and (2) easily and quickly (~5 s) changing between glutamate applications in the absence and presence of drug.

Ketamine in pain management

For ketamine's fiftieth birthday, a narrative review of this unique drug in pain management is presented. Its history is traced from its conception, and its heritage, as a phencyclidine offspring, delineated. The earliest roots of the conceptions concerning the mechanisms of action are sought, and then followed in preclinical as well as clinical research. The major proposed mechanisms in the literature are commented on and evaluated. The growth of the clinical evidence for perioperative pain, acute pain, and chronic pain is followed from early attempts to systematic reviews. Finally, an attempt is made to foresee what the next 50 years might hold in store for our 50 years old.

Comparison of behavioral effects of the NMDA receptor channel blockers memantine and ketamine in rats

Memantine and ketamine block N-methyl-D-aspartate (NMDA) receptors with similar affinity and kinetics, yet their behavioral consequences differ: e.g., memantine is used to alleviate symptoms of Alzheimer's disease, whereas ketamine reproduces symptoms of schizophrenia. The two drugs exhibit different pharmacokinetics, which may play a principal role in their differential behavioral effects. To gain insight into the drugs' behavioral consequences, we treated adult male rats acutely with varying doses (0-40 mg/kg i.p.) of memantine or ketamine and assessed exploratory behavior and spatial working memory. To examine the importance of pharmacokinetics, we assessed behavior either 15 or 45 min after drug administration. Both drugs decreased ambulation, fine movements, and rearing at the beginning of the exploratory activity test; however, at the end of the test, high doses of only memantine increased ambulation and fine movements. High doses of both drugs disrupted spontaneous alternation, a measure of working memory, but high doses of only memantine elicited perseverative behavior. Surprisingly, ketamine's effects were influenced by the delay between drug administration and testing no more frequently than were memantine's. Our findings show that, regardless of test delay, memantine and ketamine evoke similar behavioral effects at lower doses, consistent with NMDA receptors being both drugs' principal site of action, but can have divergent effects at higher doses. Our results suggest that the divergence of memantine's and ketamine's behavioral consequences is likely to result from differences in mechanisms of NMDA receptor antagonism or actions at other targets.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

This is an update of the original review published in Issue 1, 2003. Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of cancer pain, particularly when opioids alone prove to be ineffective. Ketamine is known to have psychotomimetic (including hallucinogenic), urological and hepatic adverse effects.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids in the treatment of cancer pain.

SEARCH METHODS

Studies were originally identified from MEDLINE (1966 to 2002), EMBASE (1980 to 2002), CancerLit (1966 to 2002), The Cochrane Library (Issue 1, 2001); by handsearching reference lists from review articles, trials, and chapters from standard textbooks on pain and palliative care. The manufacturer of ketamine (Pfizer Parke-Davis) provided search results from their in-house database, PARDLARS.An improved and updated search of the following was performed in May 2012: CENTRAL, MEDLINE & OVID MEDLINE R, EMBASE.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of adult patients with cancer and pain being treated with an opioid, and receiving either ketamine (any dose and any route of administration) or placebo or an active control. Studies having a group size of at least 10 participants who completed the trial.

DATA COLLECTION AND ANALYSIS

Two independent review authors identified four RCTs for possible inclusion in the review, and 32 case studies/case series reports. Quality and validity assessment was performed by three independent review authors, and two RCTs were excluded because of inappropriate study design. Patient-reported pain intensity and pain relief was assessed using visual analogue scales (VAS), verbal rating scales or other validated scales, and adverse effects data were collated. For the update three RCTs were identified for possible inclusion in the review.

MAIN RESULTS

Three new studies were identified by the updated search. All three were excluded from the review. Two studies were eligible for inclusion in the original review and both concluded that ketamine improves the effectiveness of morphine in the treatment of cancer pain. However, pooling of the data was not appropriate because of the small total number of participants (30), and the presence of clinical heterogeneity. Some patients experienced hallucinations on both ketamine plus morphine and morphine alone and were treated successfully with diazepam. No other serious adverse effects were reported.

AUTHORS' CONCLUSIONS

Since the last version of this review three new studies were identified but excluded from the review. Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of cancer pain. More RCTs are needed.