Use of oral ketamine in chronic pain management: a review

New use for an old drug: oral ketamine for treatment-resistant depression

Treatment-resistant depression (TRD) is a disabling disorder that can interfere with a patient's capacity to understand and participate in medical care and thus negatively impact individual morbidity and mortality. Hospitalised patients with TRD may require rapid alleviation of severe symptomatology, particularly when suicidal or if unable to participate in care decisions. Ketamine is well known for its anaesthetic effects and its use as a 'street' drug; however, its action as an N-methyl-D-aspartate receptor antagonist makes ketamine a potential therapy for TRD. The majority of studies investigating ketamine for TRD have used intravenous drug delivery, demonstrating benefit for rapid alleviation and sustained response of depression symptoms. Oral ketamine for urgent alleviation of TRD symptoms is less reported. We describe rapid alleviation of severe TRD with oral ketamine in a severely ill postoperative hospitalised patient, and review the current literature on 'off-label' use of ketamine for treatment of refractory depression.

A literature review on the pharmacological sensitivity of human evoked hyperalgesia pain models

AIMS

Human evoked pain models can be used to determine the efficacy of new and existing analgesics and to aid in the identification of new targets. Aspects of neuropathic pain can be simulated by inducing hyperalgesia resulting from provoked sensitization. The present literature review aimed to provide insight into the sensitivity of different hyperalgesia and allodynia models of pharmacological treatment.

METHODS

A literature search was performed to identify randomized, double-blind, placebo-controlled studies that included human hyperalgesia pain models and investigated the pharmacodynamic effects of different classes of drugs.

RESULTS

Three hyperalgesia models [ultraviolet B (UVB) irradiation, capsaicin and thermode burn] have been used extensively. Assessment of hyperalgesia/allodynia and pharmacological effect are measured using challenge tests, which generally comprise thermal (heat/cold) or mechanical stimulation (pin-prick, stroking or impact). The UVB model was sensitive to the antihyperalgesic effects of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids. The capsaicin model was partially sensitive to opioids. The burn model did not detect any antihyperalgesic effects when NSAIDs or local anaesthetics were administered but responded to the effects of N-methyl D-aspartate (NMDA) receptor antagonists by moderately reducing mechanical hyperalgesia.

CONCLUSIONS

Based on pharmacological sensitivity, the UVB model adequately reflects inflammatory pain and was sensitive to NSAIDs and opioids. Findings from the capsaicin and burn models raised questions about the translatability of these models to the treatment of neuropathic pain. There is a need for a reproducible and predictive model of neuropathic pain, either in healthy subjects or in patients.

The nitroxyl donor, Angeli's salt, reduces chronic constriction injury-induced neuropathic pain

Chronic pain is a major health problem worldwide. We have recently demonstrated the analgesic effect of the nitroxyl donor, Angeli's salt (AS) in models of inflammatory pain. In the present study, the acute and chronic analgesic effects of AS was investigated in chronic constriction injury of the sciatic nerve (CCI)-induced neuropathic pain in mice. Acute (7th day after CCI) AS treatment (1 and 3 mg/kg; s.c.) reduced CCI-induced mechanical, but not thermal hyperalgesia. The acute analgesic effect of AS was prevented by treatment with 1H-[1,2, 4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor), KT5823 (an inhibitor of protein kinase G [PKG]) or glibenclamide (GLB, an ATP-sensitive potassium channel blocker). Chronic (7-14 days after CCI) treatment with AS (3 mg/kg, s.c.) promoted a sustained reduction of CCI-induced mechanical and thermal hyperalgesia. Acute AS treatment reduced CCI-induced spinal cord allograft inflammatory factor 1 (known as Iba-1), interleukin-1β (IL-1β), and ST2 receptor mRNA expression. Chronic AS treatment reduced CCI-induced spinal cord glial fibrillary acidic protein (GFAP), Iba-1, IL-1β, tumor necrosis factor-α (TNF-α), interleukin-33 (IL-33) and ST2 mRNA expression. Chronic treatment with AS (3 mg/kg, s.c.) did not alter aspartate aminotransferase, alanine aminotransferase, urea or creatinine plasma levels. Together, these results suggest that the acute analgesic effect of AS depends on activating the cGMP/PKG/ATP-sensitive potassium channel signaling pathway. Moreover, chronic AS diminishes CCI-induced mechanical and thermal hyperalgesia by reducing the activation of spinal cord microglia and astrocytes, decreasing TNF-α, IL-1β and IL-33 cytokines expression. This spinal cord immune modulation was more prominent in the chronic treatment with AS. Thus, nitroxyl limits CCI-induced neuropathic pain by reducing spinal cord glial cells activation.

Oral ketamine for the treatment of pain and treatment-resistant depression†

BACKGROUND

Recent studies with intravenous (i.v.) application of ketamine show remarkable but short-term success in patients with MDD. Studies in patients with chronic pain have used different ketamine applications for longer time periods. This experience may be relevant for psychiatric indications.

AIMS

To review the literature about the dosing regimen, duration, effects and side-effects of oral, intravenous, intranasal and subcutaneous routes of administration of ketamine for treatment-resistant depression and pain.

METHOD

Searches in PubMed with the terms 'oral ketamine', 'depression', 'chronic pain', 'neuropathic pain', 'intravenous ketamine', 'intranasal ketamine' and 'subcutaneous ketamine' yielded 88 articles. We reviewed all papers for information about dosing regimen, number of individuals who received ketamine, number of ketamine days per study, results and side-effects, as well as study quality.

RESULTS

Overall, the methodological strength of studies investigating the antidepressant effects of ketamine was considered low, regardless of the route of administration. The doses for depression were in the lower range compared with studies that investigated analgesic use. Studies on pain suggested that oral ketamine may be acceptable for treatment-resistant depression in terms of tolerability and side-effects.

CONCLUSIONS

Oral ketamine, given for longer time periods in the described doses, appears to be well tolerated, but few studies have systematically examined the longer-term negative consequences. The short- and longer-term depression outcomes as well as side-effects need to be studied with rigorous randomised controlled trials.

Long-Term Intravenous Ketamine for Analgesia in a Child with Severe Chronic Intestinal Graft versus Host Disease

Ketamine is reported to be an effective adjuvant to opioids in the treatment of refractory cancer pain; however, the use of high doses of ketamine for extended periods in pediatric patients has not been described. We present a five-year-old male with grade IV intestinal GVHD whose abdominal pain required both hydromorphone and ketamine for a period of over four months. There was no evidence of hepatotoxicity, hemorrhagic cystitis, or other adverse effects. Possible withdrawal symptoms were mild and were readily mitigated by gradually weaning ketamine.

The role of ketamine in the treatment of chronic cancer pain

Background and aim

Ketamine is a drug used for the induction and maintenance of general anesthesia, for the treatment of postoperative and posttraumatic acute pain, and more recently, for the reduction of postoperative opioid requirements. The main mechanism of action of ketamine is the antagonization of N-methyl-D-aspartate (NMDA) receptors that are associated with central sensitization. In the pathogenesis of chronic pain and particularly in neuropathic pain, an important role is played by the activation of NMDA receptors. Although ketamine is indicated and used for the treatment of chronic cancer pain as an adjuvant to opioids, there are few clinical studies that clearly demonstrate the effectiveness of ketamine in this type of pain.

The aim of this study is to analyze evidence-based clinical data on the effectiveness and safety of ketamine administration in the treatment of chronic neoplastic pain, and to summarize the evidence-based recommendations for the use of ketamine in the treatment of chronic cancer pain.

Method

We reviewed the literature from the electronic databases of MEDLINE, COCHRANE, PUBMED, MEDSCAPE (1998–2014), as well as chapters of specialized books (palliative care, pain management, anesthesia).

Results

A number of studies support the effectiveness of ketamine in the treatment of chronic cancer pain, one study does not evidence clear clinical benefits for the use of ketamine, and some studies included too few patients to be conclusive.

Conclusions

Ketamine represents an option for neoplasic pain that no longer responds to conventional opioid treatment, but this drug should be used with caution, and the development of potential side effects should be carefully monitored.

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.

Ketamine Affects In Vitro Differentiation of Monocyte into Immature Dendritic Cells

Background:

Monocytes (MOs) have the unique ability to differentiate into immature dendritic cells (iDCs) (MO→iDC) under the influence of interleukin-4 and granulocyte–monocyte colony-stimulating factor (IL-4&GM-CSF). In this study, the authors investigated the influence of ketamine on the process of MO→iDC.

Methods:

iDCs were cultured from MO obtained from 36 subjects in the presence of IL-4 and GM-CSF and ketamine at 100, 10, and 1 μg/ml for 5 days. In some of the experiments, the authors used nonspecific N-methyl-d-aspartate (NMDA) receptor antagonist MK-801, NMDA, or a neutralizing antibody for transforming growth factor β (TGFβ). The expression of surface markers and functional assays were used to assess the effect of ketamine on IL-4&GM-CSF-stimulated MO. IL-4&GM-CSF-stimulated MO’s supernatants were assessed for cytokine levels.

Results:

Ketamine at 10 μg/ml, and higher concentrations, diminished the expression of CD1a on IL-4&GM-CSF-stimulated MO and retarded both their ability to process DQ ovalbumin and mixed lymphocyte reaction stimulation. The addition of ketamine to IL-4&GM-CSF-differentiated MO resulted in the persistent expression of CD14 and unchanged expression of CD86 and CD206. The phagocytic abilities of IL-4&GM-CSF-differentiated MO were not changed by ketamine. MK-801, a nonselective NMDA agonist, mimicked ketamine’s effect on MO→iDC differentiation. Adding exogenous NMDA to IL-4&GM-CSF-stimulated MO in the presence of ketamine partially restored the level of CD1a+. TGFβ was elevated in supernatants of IL-4&GM-CSF-stimulated MO in the presence of ketamine. Adding neutralizing TGFβ antibody or TGFβR1 blocker (SB431542) resulted in the full recovery of MO→iDC, despite the presence of ketamine.

Conclusions:

Ketamine diminishes the process of MO→iDC in vitro. This is mediated via NMDA-dependent mechanisms and TGFβ.

Complex regional pain syndrome type I: a comprehensive review

BACKGROUND

Complex regional pain syndrome type I (CRPS I), formerly known as reflex sympathetic dystrophy (RSD), is a chronic painful disorder that usually develops after a minor injury to a limb. This topical review gives a synopsis of CRPS I and discusses the current concepts of our understanding of CRPS I in adults, the diagnosis, and treatment options based on the limited evidence found in medical literature. CRPS I is a multifactorial disorder. Possible pathophysiological mechanisms of CRPS I are classic and neurogenic inflammation, and maladaptive neuroplasticity. At the level of the central nervous system, it has been suggested that an increased input from peripheral nociceptors alters the central processing mechanisms.

METHODS

A literature search was conducted using, as electronic bibliographic database, Medline from 1980 until 2014.

RESULTS

An early diagnosis and multidisciplinary treatment are necessary to prevent permanent disability.

CONCLUSIONS

The pharmacological treatment of CRPS I is empirical and insufficiently effective. Further research is needed regarding the therapeutic modalities discussed in the guidelines. Physical therapy is widely recommended as a first-line treatment. The efficacy of local anesthetic sympathetic blockade as treatment for CRPS I is questionable.

Ketamine: Current applications in anesthesia, pain, and critical care

Ketamine was introduced commercially in 1970 with the manufacturer's description as a "rapidly acting, nonbarbiturate general anesthetic" and a suggestion that it would be useful for short procedures. With the help of its old unique pharmacological properties and newly found beneficial clinical properties, ketamine has survived the strong winds of time, and it currently has a wide variety of clinical applications. It's newly found neuroprotective, antiinflammatory and antitumor effects, and the finding of the usefulness of low dose ketamine regimens have helped to widen the clinical application profile of ketamine. The present article attempts to review the current useful applications of ketamine in anesthesia, pain and critical care. It is based on scientific evidence gathered from textbooks, journals, and electronic databases.

Oral ketamine analgesia in chronic pain and problematic rise in blood pressure

Hospitals and specialists in the UK are increasingly prescribing and dispensing off-license drugs such as ketamine which are not routinely included in the prescribing record of the general practitioner (GP). We present the case of a 67-year-old woman who developed an episode of uncontrolled raised blood pressure (BP) (224/124 mm Hg) following hospital introduction of oral ketamine for chronic pain. This raised BP was not followed up, and she was then found to be persistently hypertensive in the community some months later. No obvious cause for the patient's increase in BP could be identified. Only on reduction of the ketamine dose and introduction of additional antihypertensive medication, did her BP normalise. We postulate that long-term ketamine use may have been associated with this unexpected and persistent rise in BP. Clinicians should monitor BP closely during ketamine therapy and be wary of new hypertension associated with its long-term use. Further research is needed on the long-term effects of ketamine on BP.

Efficacy and safety of oral ketamine for the relief of intractable chronic pain: A retrospective 5-year study of 51 patients

BACKGROUND

This work summarizes the efficiency, failures and adverse effects of oral administration of ketamine at home for intractable pain.

METHODS

This 5-year retrospective study involved testing ketamine by intravenous in-hospital administration, then a conversion to an oral route, or oral treatment directly administered at home. The daily intravenous dose was increased by steps of 0.5 mg/kg to attain an effective daily dose of 1.5-3.0 mg/kg. Pain was evaluated on a numeric scale from 0 to 10, and evidence of adverse effects was collected every day. The effective daily dose was delivered orally (three to four intakes). If effective, ketamine was continued for 3 months. Short infusions or direct oral treatment began with a 0.5-mg/kg dose, then the daily ketamine dose was increased in 15- to 20-mg increments.

RESULTS

Among 55 cases (51 patients, neuropathic pain 60%), the mean effective oral dose was 2 mg/kg. Ketamine was effective in 24 patients (44%, mean pain reduction 67 ± 17%), partially effective in 20% (mean pain reduction 30 ± 11%), with a mean opioid sparing of 63 ± 32%, and failure in 22%. Half of the patients experienced adverse effects, but only eight had to stop treatment. For patients with opioid therapy, failure of ketamine was less frequent (7% vs. 36%; p < 0.02), with fewer adverse effects (33% vs. 68%; p < 0.01).

CONCLUSIONS

Pain was reduced or abolished in two-thirds of patients under ketamine therapy; ketamine was effective for patients taking opioids and resulted in few adverse effects.

Pain care for patients with epidermolysis bullosa: best care practice guidelines

BACKGROUND

Inherited epidermolysis bullosa (EB) comprises a group of rare disorders that have multi-system effects and patients present with a number of both acute and chronic pain care needs. Effects on quality of life are substantial. Pain and itching are burdensome daily problems. Experience with, and knowledge of, the best pain and itch care for these patients is minimal. Evidence-based best care practice guidelines are needed to establish a base of knowledge and practice for practitioners of many disciplines to improve the quality of life for both adult and pediatric patients with EB.

METHODS

The process was begun at the request of Dystrophic Epidermolysis Bullosa Research Association International (DEBRA International), an organization dedicated to improvement of care, research and dissemination of knowledge for EB patients worldwide. An international panel of experts in pain and palliative care who have extensive experience caring for patients with EB was assembled. Literature was reviewed and systematically evaluated. For areas of care without direct evidence, clinically relevant literature was assessed, and rounds of consensus building were conducted. The process involved a face-to-face consensus meeting that involved a family representative and methodologist, as well as the panel of clinical experts. During development, EB family input was obtained and the document was reviewed by a wide variety of experts representing several disciplines related to the care of patients with EB.

RESULTS

The first evidence-based care guidelines for the care of pain in EB were produced. The guidelines are clinically relevant for care of patients of all subtypes and ages, and apply to practitioners of all disciplines involved in the care of patients with EB. When the evidence suggests that the diagnosis or treatment of painful conditions differs between adults and children, it will be so noted.

CONCLUSIONS

Evidence-based care guidelines are a means of standardizing optimal care for EB patients, whose disease is often times horrific in its effects on quality of life, and whose care is resource-intensive and difficult. The guideline development process also highlighted areas for research in order to improve further the evidence base for future care.

Withdrawal assessment following subchronic oral ketamine administration in Cynomolgus macaques

Recently there is increased regulatory interest in the assessment of physical dependence and withdrawal as part of the safety assessment for novel therapeutic entities. Choosing appropriate and sensitive parameters to detect withdrawal syndromes, and relevant positive control comparator drugs that can be administered in the same manner as the test agent, are critical study design elements. Pilot studies to determine the effects of oral ketamine in cynomolgus monkeys during, and following cessation of treatment, were explored. Detailed behavioral observations (both remote and interactive), food consumption, and body weight and temperature, were assessed during the dose-ranging, repeat dose (5 or 14 days), and withdrawal phases (3 or 5 days). Doses explored during dose-ranging included 20, 40, 100, or 200 mg/kg ketamine; subsequent withdrawal assessments were conducted following repeat dosing of 150 mg/kg. In the 14-day dosing study, exposure to ketamine and norketamine was assessed following 8 days of dosing. Administration of 150 mg/kg ketamine produced decreased activity, loss of balance, ataxia, hunched posture, nystagmus, lateral recumbence, and changes in alertness levels during dosing phases. When ketamine was withdrawn, increased reactivity, increased activity, and stereotypic behaviors were demonstrated that were absent during baseline or the dosing phase of the studies.

Chronic pain resolution after a lucid dream: a case for neural plasticity?

Chronic pain is often managed using a multidisciplinary, biopsychosocial approach. Interventions targeting the biological, psychological, and social aspects of both the patient and the pain have been demonstrated to provide objective and subjective improvement in chronic pain symptoms. The mechanism by which pain attenuation occurs after these interventions remains to be elucidated. While there is a relatively large body of empirical literature suggesting that functional and structural changes in the peripheral and central nervous systems are key in the development and maintenance of chronic pain states, less is known about changes that take place in the nervous system as a whole after biopsychosocial interventions. Using as a model the unique case of Mr. S, a patient suffering with chronic pain for 22 years who experienced a complete resolution of pain after a lucid dream following 2 years of biopsychosocial treatments, we postulate that central nervous system (CNS) reorganization (i.e., neural plasticity) serves as a possible mechanism for the therapeutic benefit of multidisciplinary treatments, and may set a neural framework for healing, in this case via a lucid dream.

Antidepressant, mood stabilizing and procognitive effects of very low dose sublingual ketamine in refractory unipolar and bipolar depression

Intravenous ketamine (0.5 mg/kg) produces robust, rapid and long-lasting antidepressant effects, but is unpractical. Sublingual administration of ketamine renders better bioavailability (~30%) and less conversion to norketamine than oral administration. We evaluated the therapeutic effects and tolerability of very low dose sublingual (VLDS) racemic ketamine (10 mg from a 100 mg/ml solution for 5 min and swallowed), repeatedly administered every 2-3 d or weekly, in 26 out-patients with refractory unipolar or bipolar depression. According to patients' reports, VLDS ketamine produced rapid, clear and sustained effects, improving mood level and stability, cognition and sleep in 20 patients (77%), with only mild and transient light-headedness as a common side-effect (no euphoria, psychotic or dissociative symptoms). Remission remained in some patients after stopping ketamine. Thus, VLDS ketamine may have broad spectrum effects beyond its antidepressant properties, with rapid onset of action, high efficacy, good tolerability and low cost, allowing extended treatment as needed.

Ketamine for pain in adults and children with cancer: a systematic review and synthesis of the literature

OBJECTIVE

Chronic cancer pain is often refractory and difficult to treat. Ketamine is a medication with evidence of efficacy in the treatment of chronic pain.

DESIGN

This article presents a synthesis of the data on ketamine for refractory cancer pain in adults and children.

RESULTS

There are five randomized, double-blind, controlled trials of ketamine use in cancer pain that demonstrate improvement in pain for some patients. There are six prospective, uncontrolled trials in cancer pain that also demonstrate improvement in pain scores for some patients. There are no randomized, controlled trials in children with cancer pain, although there are a few studies reflecting improved pain control with ketamine for children with cancer pain. Adverse events for adults on ketamine are most commonly somnolence, feelings of insobriety, nausea/vomiting, hallucinations, depersonalization/derealization, and drowsiness. However, when ketamine is combined with benzodiazepines, feelings of insobriety, hallucinations, and depersonalization/derealization are not reported. Children on ketamine have had few reported adverse effects, which include sedation, anorexia, urinary retention, and myoclonic movements. Recommended ketamine infusion dosages are from 0.05 to 0.5 mg/kg/h (intravenous or subcutaneous). Recommended oral dosages of ketamine are 0.2-0.5 mg/kg/dose two to three times daily with a maximum of 50 mg/dose three times daily.

CONCLUSIONS

Despite limitations in the breadth and depth of data available, there is evidence that ketamine may be a viable option for treatment-refractory cancer pain.

Clinical outcomes of augmentation cystoplasty in patients suffering from ketamine-related bladder contractures

OBJECTIVE

To evaluate the outcomes of augmentation cystoplasty in patients with bladder contractures secondary to chronic ketamine abuse.

METHOD

Patients who had received augmentation cystoplasty to treat ketamine-related bladder contractures in two hospitals in our region were reviewed retrospectively. Their history of ketamine consumption, presenting symptoms, history of treatment, surgical information and post-operative conditions were retrieved from clinical records and then summarized.

RESULTS

Between 2006 and 2011, four patients (three women and one man), aged 21-30 years (mean 27 years), underwent augmentation cystoplasty for ketamine-related bladder contractures. The duration of ketamine consumption ranged from 3 to 15 years, and all four patients resumed ketamine consumption after surgery. The mean maximal baseline and post-operative bladder capacity was 37.5 cc (range 25-50 cc) and up to 400-500 cc, respectively. Three patients experienced a further deterioration in renal function that was secondary to new-onset ureteral strictures in two cases and to sepsis in the other. At the time of the last follow-up, three patients could void spontaneously and one required regular intermittent catheterization.

CONCLUSION

Ketamine cystitis is an emerging medical condition that requires a multi-disciplinary approach to manage the patients. Simple surgical management of the physical component of the contracted bladder may produce only suboptimal results, and could even cause further problems in some patients. The importance of compliance with post-operative care and abstinence from drug use should be stressed to the patients before surgery. In view of the high complication rate, the option of a simple ileal conduit should also be discussed prior to surgical intervention.

Interventions for treating pain and disability in adults with complex regional pain syndrome

BACKGROUND

There is currently no strong consensus regarding the optimal management of complex regional pain syndrome although a multitude of interventions have been described and are commonly used.

OBJECTIVES

To summarise the evidence from Cochrane and non-Cochrane systematic reviews of the effectiveness of any therapeutic intervention used to reduce pain, disability or both in adults with complex regional pain syndrome (CRPS).

METHODS

We identified Cochrane reviews and non-Cochrane reviews through a systematic search of the following databases: Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects (DARE), Ovid MEDLINE, Ovid EMBASE, CINAHL, LILACS and PEDro. We included non-Cochrane systematic reviews where they contained evidence not covered by identified Cochrane reviews. The methodological quality of reviews was assessed using the AMSTAR tool.We extracted data for the primary outcomes pain, disability and adverse events, and the secondary outcomes of quality of life, emotional well being and participants' ratings of satisfaction or improvement. Only evidence arising from randomised controlled trials was considered. We used the GRADE system to assess the quality of evidence.

MAIN RESULTS

We included six Cochrane reviews and 13 non-Cochrane systematic reviews. Cochrane reviews demonstrated better methodological quality than non-Cochrane reviews. Trials were typically small and the quality variable.There is moderate quality evidence that intravenous regional blockade with guanethidine is not effective in CRPS and that the procedure appears to be associated with the risk of significant adverse events.There is low quality evidence that bisphosphonates, calcitonin or a daily course of intravenous ketamine may be effective for pain when compared with placebo; graded motor imagery may be effective for pain and function when compared with usual care; and that mirror therapy may be effective for pain in post-stroke CRPS compared with a 'covered mirror' control. This evidence should be interpreted with caution. There is low quality evidence that local anaesthetic sympathetic blockade is not effective. Low quality evidence suggests that physiotherapy or occupational therapy are associated with small positive effects that are unlikely to be clinically important at one year follow up when compared with a social work passive attention control.For a wide range of other interventions, there is either no evidence or very low quality evidence available from which no conclusions should be drawn.

AUTHORS' CONCLUSIONS

There is a critical lack of high quality evidence for the effectiveness of most therapies for CRPS. Until further larger trials are undertaken, formulating an evidence-based approach to managing CRPS will remain difficult.

Interventions for treating pain and disability in adults with complex regional pain syndrome

BACKGROUND

There is currently no strong consensus regarding the optimal management of complex regional pain syndrome although a multitude of interventions have been described and are commonly used.

OBJECTIVES

To summarise the evidence from Cochrane and non-Cochrane systematic reviews of the effectiveness of any therapeutic intervention used to reduce pain, disability or both in adults with complex regional pain syndrome (CRPS).

METHODS

We identified Cochrane reviews and non-Cochrane reviews through a systematic search of the following databases: Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects (DARE), Ovid MEDLINE, Ovid EMBASE, CINAHL, LILACS and PEDro. We included non-Cochrane systematic reviews where they contained evidence not covered by identified Cochrane reviews. The methodological quality of reviews was assessed using the AMSTAR tool.We extracted data for the primary outcomes pain, disability and adverse events, and the secondary outcomes of quality of life, emotional well being and participants' ratings of satisfaction or improvement. Only evidence arising from randomised controlled trials was considered. We used the GRADE system to assess the quality of evidence.

MAIN RESULTS

We included six Cochrane reviews and 13 non-Cochrane systematic reviews. Cochrane reviews demonstrated better methodological quality than non-Cochrane reviews. Trials were typically small and the quality variable.There is moderate quality evidence that intravenous regional blockade with guanethidine is not effective in CRPS and that the procedure appears to be associated with the risk of significant adverse events.There is low quality evidence that bisphosphonates, calcitonin or a daily course of intravenous ketamine may be effective for pain when compared with placebo; graded motor imagery may be effective for pain and function when compared with usual care; and that mirror therapy may be effective for pain in post-stroke CRPS compared with a 'covered mirror' control. This evidence should be interpreted with caution. There is low quality evidence that local anaesthetic sympathetic blockade is not effective. Low quality evidence suggests that physiotherapy or occupational therapy are associated with small positive effects that are unlikely to be clinically important at one year follow up when compared with a social work passive attention control.For a wide range of other interventions, there is either no evidence or very low quality evidence available from which no conclusions should be drawn.

AUTHORS' CONCLUSIONS

There is a critical lack of high quality evidence for the effectiveness of most therapies for CRPS. Until further larger trials are undertaken, formulating an evidence-based approach to managing CRPS will remain difficult.

Regulator of G protein signaling 4 [corrected] is a crucial modulator of antidepressant drug action in depression and neuropathic pain models

Regulator of G protein signaling 4 (Rgs4) is a signal transduction protein that controls the function of monoamine, opiate, muscarinic, and other G protein-coupled receptors via interactions with Gα subunits. Rgs4 is expressed in several brain regions involved in mood, movement, cognition, and addiction and is regulated by psychotropic drugs, stress, and corticosteroids. In this study, we use genetic mouse models and viral-mediated gene transfer to examine the role of Rgs4 in the actions of antidepressant medications. We first analyzed human postmortem brain tissue and found robust up-regulation of RGS4 expression in the nucleus accumbens (NAc) of subjects receiving standard antidepressant medications that target monoamine systems. Behavioral studies of mice lacking Rgs4, including specific knockdowns in NAc, demonstrate that Rgs4 in this brain region acts as a positive modulator of the antidepressant-like and antiallodynic-like actions of several monoamine-directed antidepressant drugs, including tricyclic antidepressants, selective serotonin reuptake inhibitors, and norepinephrine reuptake inhibitors. Studies using viral-mediated increases in Rgs4 activity in NAc further support this hypothesis. Interestingly, in prefrontal cortex, Rgs4 acts as a negative modulator of the actions of nonmonoamine-directed drugs that are purported to act as antidepressants: the N-methyl-D-aspartate glutamate receptor antagonist ketamine and the delta opioid agonist (+)-4-[(αR)-α-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide. Together, these data reveal a unique modulatory role of Rgs4 in the brain region-specific actions of a wide range of antidepressant drugs and indicate that pharmacological interventions at the level of RGS4 activity may enhance the actions of such drugs used for the treatment of depression and neuropathic pain.

Oral ketamine and dexmedetomidine in adults' burns wound dressing--A randomized double blind cross over study

Study was designed to compare analgesic efficacy and side effects of oral dexmedetomidine and ketamine in adults for burn wound dressing. Sixty healthy adults with thermal burns with burn area (20-50%) were randomly assigned into 2 groups. In Group K 5mg/kg ketamine and in Group D 4 mcg/kg dexmedetomidine was given orally. Patients crossed over to the other group the following day. Visual analogue score, sedation score, haemodynamic parameters were recorded from 30min after drug administration to 2h after procedure. Patients' preference was also recorded. Mean VAS score was significantly reduced from baseline in both the groups at all time points (P<0.05). Pain relief in Group K (overall mean VAS 2.6±0.6cm) was significantly better when compared to Group D (overall mean VAS 3.8±0.8cm). Patients in group K were significantly more sedated (median 3) when compared to group D (median 2), P<0.05. Delirium and excessive salivation were significant complications observed with ketamine. More patients preferred ketamine (63.3%) than dexmedetomidine (36.7%), P<0.05. Oral ketamine and dexmedetomidine produced significant pain relief during burns wound dressing. Oral ketamine produced significantly better pain relief than dexmedetomidine but was associated with delirium and excessive salivation.

Developmental neurotoxicity of ketamine in pediatric clinical use

Ketamine is widely used as an anesthetic, analgesic, and sedative in pediatric clinical practice and it is also listed as an illicit drug by most countries. Recent in vivo and in vitro animal studies have confirmed that ketamine can induce neuronal cell death in the immature brain, resulting from widespread neuronal apoptosis. These effects can disturb normal development further altering the structure and functions of the brain. Our recent studies further indicate that ketamine can alter neurogenesis from neural stem progenitor cells in the developing brain. Taken together, these findings identify a novel complication associated with ketamine use in premature infants, term newborns, and pregnant women. Recent data on the developmental neurotoxicity of ketamine are reviewed with proposed future directions for evaluating the safety of ketamine in these patient populations.

Effects of ketamine and its metabolites on ion currents in differentiated hippocampal H19-7 neuronal cells and in HEK293T cells transfected with α-hslo subunit

Ketamine (KT), a dissociative anesthetic, is known to induce schizophrenia-like psychosis. The percentage of KT abuse has recently grown fast despite KT being a controlled drug. The mechanism of KT actions is related to the inhibition of NMDA receptors. Whether KT produces other effects on ion currents in hippocampal neurons remains unclear. In this study, we attempted to evaluate the possible effects of KT and other related compounds on ion currents in hippocampal neuron-derived H19-7 cells. This drug exerted an inhibitory effect on Ca(2+)-activated K(+) current (IK(Ca)) in these cells with an IC(50) value of 274 μM. Pimaric acid (30 μM) or abietic acid (30 μM), known to stimulate large-conductance Ca(2+)-activated K(+) channels, reversed KT-induced inhibition of I(K)(Ca). In HEK293T cells expressing a-humans low poke, KT-induced inhibition of I(K)(Ca) still existed. Dehydronorketamine (300 μM) had little or no effect on the IK(Ca) amplitude, while norketamine (300 μM) slightly but significantly suppressed it. In inside–out configuration, KT applied to the intracellular face of the membrane did not alter single channel conductance of large-conductance Ca(2+)-activated K(+) (BKCa) channels; however, it did significantly reduce the probability of channel openings. Addition of KT was effective in depressing the peak amplitude of voltage-gated Na(+) current. Moreover, the presence of KT was noted to enhance the amplitude of membrane electroporation-induced inward currents (IMEP) in differentiated H19-7 cells. KT-stimulated IMEP was reversed by further application of LaCl(3) (100 μM), but not by NMDA (30 μM). The modulations by this compound of ion channels may contribute to the underlying mechanisms through which KT and its metabolites influence the electrical behavior of hippocampal neurons if similar findings occur in vivo.

Oral ketamine and midazolam for pediatric burn patients: a prospective, randomized, double-blind study

PURPOSE

The aim of this study was to compare the efficacy of oral midazolam and ketamine with oral midazolam, acetaminophen, and codeine in providing sedation and analgesia for wound care procedures in children with burns.

METHODS

This is a prospective, randomized, double-blind study that includes patients 1 to 5 years old hospitalized between 2010 and 2011, with burns covering up to 10% of total body surface area that required bedside wound care. Group 1 received oral midazolam (0.5mg/kg) and ketamine (5mg/ kg). Group 2 received oral midazolam (0.5mg/kg), acetaminophen (10mg/kg), and codeine (1mg/kg). Sedation was assessed using the University of Michigan Sedation Scale and pain using the CHEOPS scale.

RESULTS

Sixty patients were enrolled and evenly distributed into the two groups. There were a higher percentage of well-sedated patients in Group 1, but this was not statistically significant. Patients in Group 2 reported lower levels of pain (p=0.0245). Adverse reactions were reported in both groups. The only parameter that had a statistical difference was nystagmus (p=0.001).

CONCLUSION

The combination of oral midazolam and ketamine provides better analgesia than the combination of midazolam, acetaminophen, and codeine for painful procedures in burned children.

Ketamine for treatment-resistant unipolar depression: current evidence

Currently available drugs for unipolar major depressive disorder (MDD), which target monoaminergic systems, have a delayed onset of action and significant limitations in efficacy. Antidepressants with primary pharmacological targets outside the monoamine system may offer the potential for more rapid activity with improved therapeutic benefit. The glutamate system has been scrutinized as a target for antidepressant drug discovery. The purpose of this article is to review emerging literature on the potential rapid-onset antidepressant properties of the glutamate NMDA receptor antagonist ketamine, an established anaesthetic agent. The pharmacology of ketamine and its enantiomer S-ketamine is reviewed, followed by examples of its clinical application in chronic, refractory pain conditions, which are commonly co-morbid with depression. The first generation of studies in patients with treatment-resistant depression (TRD) reported the safety and acute efficacy of a single subanaesthetic dose (0.5 mg/kg) of intravenous ketamine. A second generation of ketamine studies is focused on testing alternate routes of drug delivery, identifying methods to prevent relapse following resolution of depressive symptoms and understanding the neural basis for the putative antidepressant actions of ketamine. In addition to traditional depression rating endpoints, ongoing research is examining the impact of ketamine on neurocognition. Although the first clinical report in MDD was published in 2000, there is a paucity of adequately controlled double-blind trials, and limited clinical experience outside of research settings. Given the potential risks of ketamine, safety considerations will ultimately determine whether this old drug is successfully repositioned as a new therapy for TRD.

Cancer pain management in resource-limited settings: a practice review

Pain in cancer is a common and burdensome symptom with different causes but in a significant number of cases it is undiagnosed and undertreated because of lack of skills for its assessment. Pain has significant negative impact on the patient and, therefore, it needs to be managed urgently and appropriately. In resource-limited settings, there are several barriers and challenges to pain management but even in these circumstances pain can be well managed with planned and innovative use of resources and if the World Health Organization public health system approach is used to ensure opioid availability.

Chronic pain after trauma

Chronic pain is more common following trauma than often realised. It may be due to nociceptive pain or often include a neuropathic component which can be difficult to treat. There are several pain syndromes, such as complex regional pain syndrome and post-amputation pains, which are specifically associated with trauma. These are described, as are the differences in features of nociceptive and neuropathic pain. This article aims to describe the features of chronic pain following trauma using a bio-psycho-social model. An approach to taking a comprehensive pain history and management options are also considered. A multi-disciplinary team using physiotherapists and psychologists is generally required and the importance of good rehabilitation following major trauma cannot be over-emphasised. For the physician, there are a range of pharmaceutical options available and a multimodal approach is recommended. There are also a number of non-invasive therapies on offer such as transcutaneous electrical nerve stimulation and massage. The limited role of invasive procedures is also discussed.

Oral ketamine in the palliative care setting: a review of the literature and case report of a patient with neurofibromatosis type 1 and glomus tumor-associated complex regional pain syndrome

Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has been shown to be effective not only for its anesthetic properties but also for the analgesic and opiate-sparing effects. However, data on efficacy and safety of oral ketamine for the treatment of neuropathic or cancer pain syndromes is limited with most of the evidence based on small clinical trials and anecdotal experiences. In this review, we will analyze the clinical data on oral ketamine in the palliative care setting. After an extensive search using five major databases, a total of 19 relevant articles were included. No official clinical guidelines for the use of oral ketamine in this patient population were found. Studies on oral ketamine for cancer and neuropathic pain have shown mixed results which could be partially due to significant differences in hepatic metabolism. In addition, we will include a case report of a 38-year-old female with neurofibromatosis type 1 (NF1) with history of chronic, severe pain in her fingertips secondary to multiple glomus tumors which evolved into CRPS resistant to multiple therapies but responsive to oral ketamine. Based on our experience with oral ketamine, this drug should be administered after an intravenous trial to monitor response and side effects in patients with an adequate functional status. However, patients in the palliative care and hospice setting, especially the one at the end of their lives, may also benefit from oral ketamine even if an intravenous trial is not feasible.

Methodological challenges in supportive and palliative care cancer research

As a growing medical field, palliative and supportive care should incorporate evidence-based medical practice. The gold standard research method continues to be the randomized clinical trial. This has been pursued with regard to cancer trials focused on cure. It has specific operational and methodological challenges in advanced disease. There are numerous reasons why effective research in palliative and supportive care is difficult. A consensus on the best research strategies and design is lacking. We will discuss the principles of palliative and supportive care research, examine the inherent challenges particularly in randomized controlled trials, and offer some suggestions to overcome them.

A strategy for conversion from subcutaneous to oral ketamine in cancer pain patients: effect of a 1:1 ratio

CONTEXT

No consensus exists about the most appropriate dose ratio for conversion from parenteral to oral ketamine.

OBJECTIVES

To confirm that a 1:1 dose ratio is suitable for converting subcutaneous (s.c.) to oral ketamine in cancer patients.

METHODS

Patients with opioid poorly responsive cancer pain, who responded to 0.4, 0.6, or 0.8 mg s.c. ketamine bolus, were treated with 0.1, 0.15, or 0.2mg/kg/h ketamine infusion, respectively. Switching to the oral route, by applying a 1:1 dose ratio, was carried out in patients who experienced adequate pain relief and continued to need ketamine as a coanalgesic. Pain, somnolence, feelings of insobriety, confusion, and cardiovascular parameters were assessed throughout the process.

RESULTS

Twenty-nine patients were enrolled in the study. Ketamine infusion decreased pain intensity from severe to no pain or slight pain in 23 of 29 and six of 29 patients, respectively. The median of s.c. ketamine doses was 0.2mg/kg/h (range 0.1-0.5). After oral switching, 27 of 29 patients remained as successfully controlled as when receiving s.c. ketamine. The other two patients needed a slight dose ratio readjustment, to 1:1.3 and 1:1.5, to maintain pain control. The median of oral ketamine doses was 300 mg/day (interquartile range 240-382.5). Seven of 29 patients receiving s.c. ketamine developed moderate and transitory side effects, such as feelings of insobriety and somnolence. No side effects were present while receiving oral ketamine. No significant changes were observed in cardiovascular parameters.

CONCLUSION

A 1:1 dose ratio for conversion from s.c. to oral ketamine is safe and effective in cancer pain patients.

Successful pain relief in non-responders to spinal cord stimulation: the combined use of ketamine and spinal cord stimulation

Although spinal cord stimulation (SCS) is an established therapy for chronic neuropathic pain, still 30% of patients do not respond adequately to trial stimulation. These so called "non-responders" do not receive a permanent implantation for pain relief. The induction and maintenance of central sensitization plays a pivotal role in (chronic) neuropathic pain and is thought to be the resultant of the activation of the N-methyl-d-aspartate (NMDA) receptor in the dorsal horn. Blocking the NMDA receptor through the use of the non-competitive blocker ketamine has shown to attenuate neuropathic pain, although the undesirable side effects limit its use. The present study was performed to examine whether the combination of SCS with an individually determined sub-effective dose of intrathecal (i.t.) ketamine could convert non-responders into responders in rats with chronic neuropathic pain. Rats received a partial ligation of the sciatic nerve for the induction of neuropathic pain. Animals with tactile hypersensitivity to von Frey monofilaments (n=15) received 30 min of SCS. Non-responders to SCS (n=8) received their individually determined sub-effective i.t. dose of ketamine followed by 30 min of SCS. No side effects of the sub-effective dose of ketamine could be noted. The combined treatment of SCS and sub-effective dose of i.t. ketamine in non-responders resulted in a significant reduction of the withdrawal threshold in all previous non-responders to SCS, thereby converting them into responders to SCS.