Analgesic effect of oral ketamine in chronic neuropathic pain of spinal origin: a case report

Predictive factors of success and failure for intravenous ketamine therapy in patients suffering from chronic neuropathic pain

Background

Intravenous (IV) ketamine is used for chronic neuropathic pain refractory to other treatments. Administration of such a medication requires high-cost services while the result is not always satisfactory with a significant percentage of failure. Success and failure are related to some factors.

Method

In this study, we aim to point the most responsive disease category to IV ketamine and the predictive factors for successful and failed treatment. Two hundred and sixty-nine patients out of 371 were included. Demographic, clinical, and therapy-related variables were retrospectively collected and then statistically analyzed using various descriptive and inferential methods. A few descriptive statistics are obtained for the variables depending on their nature (e.g., percentages for qualitative variables and means for quantitative variables). Furthermore, several inferential methods are considered to address some statistical points of interest, including, but not limited to, odds ratio interpretations via logistic regression as well as association and correlation analyses.

Results

A significant association was found between the presence of intermittent pain pattern as well as the pain of chronic primary category and favorable response to IV ketamine while the history of previous analgesic interventions was significantly associated with a negative response.

Conclusion

The identified factors can be used to prospectively study the efficacy of ketamine using selection criteria based on the observed results in our study to re-evaluate the percentage of responsiveness according to these new parameters.

A systematic review of ketamine for the management of vaso-occlusive pain in sickle cell disease

Vaso-occlusive episodes (VOEs) are a common complication of sickle cell disease (SCD) and a significant cause of morbidity. Managing VOE pain can be difficult and complex. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has been used to manage VOE pain. This systematic literature review synthesizes research published from 2010 to 2020 on the use of ketamine infusion to decrease VOE pain. The review demonstrates that ketamine, a safe and effective treatment for VOE pain, could be considered more widely. However, the significant variability among published clinical studies with regard to dosing, timing of initiation, duration of infusion, and timing of discontinuation highlights the need for standardized ketamine infusion protocols for the management of VOE pain. We conclude with a brief discussion of key components of a potential standardized protocol supported by the literature reviewed as well as areas for future investigation.

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.

Can Gradual Dose Titration of Ketamine for Management of Neuropathic Pain Prevent Psychotomimetic Effects in Patients With Advanced Cancer?

Background:

Ketamine is often used to manage neuropathic pain in patients with cancer. However, it occasionally causes psychotomimetic effects such as vivid dreams, nightmares, illusions, hallucinations, and altered body image. Objective: To examine whether gradual dose titration of ketamine for management of neuropathic pain prevents psychotomimetic effects in patients with advanced cancer.

Methods:

This was a retrospective chart review. We administered ketamine when neuropathic pain in patients with advanced cancer became refractory to opioids and oral adjuvant analgesics. The starting dose of ketamine was 10 mg/d by continuous intravenous infusion. The dose was gradually increased by 10 mg/d every 4 to 6 hours to 50 mg/d or until the pain was relieved. It was subsequently increased by 25 mg/d every 12 to 24 hours until the pain was relieved.

Results:

For this study, we enrolled 46 patients with advanced cancer. The mean age was 52.2 ± 16.9 years. The mean dose at onset of action and maximum dose of ketamine were 56 ± 58 and 272 ± 214 mg/d, respectively. The mean pain intensity (numerical rating scale) decreased significantly from 7.3 ± 2.0 to 3.5 ± 2.2 after the administration of ketamine ( P < .01). The effectiveness was 69.5%. No psychotomimetic effect of less than 300 mg/d was observed during the introduction phase even though psychotropic drugs were not prescribed. Mild sedation was observed in 3 patients (7%) as the only adverse effect during the introduction phase.

Conclusion:

Gradual dose titration of ketamine for management of neuropathic pain can prevent psychotomimetic effects in patients with advanced cancer.

Perioperative management of the child on long-term opioids

The strategies used to manage children exposed to long-term opioids are extrapolated from adult literature. Opioid consumption during the perioperative period is more than three times that observed in patients not taking chronic opioids. A sparing use of opioids in the perioperative period results in both poor pain management and withdrawal phenomena. The child's pre-existing opioid requirement should be maintained, and acute pain associated with operative procedures should be managed with additional analgesia. This usually comprises short-acting opioids, regional or local anesthesia, and adjuvant therapies. Long-acting opioids, transdermal opioid patches, and implantable pumps can be used to maintain the regular opioid requirement. Intravenous infusion, nurse controlled analgesia, patient-controlled analgesia, or oral formulations are invaluable for supplemental requirements postoperatively. Effective management requires more than simply increasing opioid dose during this time. Collaboration of the child, family, and all teams involved is necessary. While chronic pain or palliative care teams and other staff experienced with the care of children suffering chronic pain may have helpful input, many pediatric hospitals do not have chronic pain teams, and many patients receiving long-term opioids are not palliative. Acute pain services are appropriate to deal with those on long-term opioids in the perioperative setting and do so successfully in many centers. Staff caring for such children in the perioperative period should be aware of the challenges these children face and be educated before surgery about strategies for postoperative management and discharge planning.

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.

[Oral ketamine-midazolam premedication of uncooperative patients in major outpatient surgery]

BACKGROUND

Currently, ketamine is not often used as an anesthetic. Its clinical characteristics and mechanism of action largely depend on antagonism of the N-methyl-D-aspartate receptor.

OBJECTIVE

To evaluate the utility of oral ketamine as a preanesthetic agent to lower surgical stress for patients with mental disability.

MATERIAL AND METHODS

Observational, retrospective study of 112 mentally disabled patients undergoing major dental surgery on an outpatient basis. The study group received oral midazolam, ibuprofen, and 6 mg/kg of ketamine; the control group received only midazolam and ibuprofen. We recorded data concerning demographics, anesthesia, surgery, physiologic variables, Glasgow score, time of onset of anxiolysis, duration of stay in the recovery ward, and adverse events.

RESULTS

Conservative odontologic treatment was provided in 66.3% of the cases. Seventy-one patients (64.4%) were in the control group and 41 patients (36.6%) in the study group. Hemodynamic, respiratory, and neurologic changes were minimal and there were no significant between-group differences. Level of sedation differed significantly between groups (P = .001) at 15 and 30 minutes; differences were also observed within the study group. Mean (SD) duration of surgery was 72.6 (29.7) minutes. Mean duration of stay in the postoperative recovery ward was 140.9 (52.1) minutes (135.8 [54.89] minutes in the study group and 144.2 [50.5] minutes in the control group). The incidence of adverse events did not differ significantly between groups.

CONCLUSIONS

Oral ketamine is an effective premedication for major ambulatory surgery and does not increase the incidence of side effects.

Use of oral ketamine in chronic pain management: a review

The analgesic effect of ketamine is primarily based on the antagonism of the N-methyl-d-aspartate (NMDA) receptor. Activation of NMDA receptors may play a crucial role in the pathogenesis of chronic pain. Little formal research has been performed on the efficacy and safety of ketamine in chronic pain, especially concerning long-term oral administration. This review provides an overview of the available clinical data on the use of oral ketamine in chronic pain management. A literature search was performed in MEDLINE, EMBASE and the Cochrane Library, resulting in 22 relevant articles. Because most retrieved articles were of a descriptive nature (e.g. case reports and case series) a quantitative analysis was not possible. There was no consistent dose-response relation. A recommended starting dosage in ketamine-naive patients is 0.5 mg/kg racemic ketamine or 0.25 mg/kg S-ketamine as a single oral dose. The dosage is increased by the same amount if required. For a continuous analgesic effect it is usually given 3-4 times daily. The injection fluid can be taken orally. When parenteral ketamine is switched to oral administration the daily dosage can be kept equal and, depending on clinical effect and/or adverse effects, is slowly increased. The pharmacologically active metabolite norketamine is believed to contribute to the analgesic effect of oral ketamine. Lack of evidence regarding efficacy, and the poor safety profile, do not support routine use of oral ketamine in chronic pain management. Oral ketamine may have a limited place as add-on therapy in complex chronic pain patients if other therapeutic options have failed.

Use of Continuous Intravenous Ketamine for End-Stage Cancer Pain in Children

Children in the terminal stage of cancer may experience intractable pain despite the use of high doses of opioids. The resultant sedating effect of the opioids limits the child's ability to communicate and participate in activities, thereby negatively affecting quality of life. Ketamine, an intravenous (IV) anesthetic with analgesic properties, when used in low doses, may be useful in managing pediatric cancer pain at the end of life. Ketamine can prevent the development of opioid tolerance and provide additional analgesia without an increase in sedating effects. At the authors' institution, 2 children with end-stage cancer were started on continuous infusion low-dose ketamine to help achieve adequate pain control and allow the children to be home and interactive for the last weeks of their lives. Each case illustrates the complexities of achieving and maintaining adequate pain control and promoting care of the child and family in a setting that is most appropriate for them.

Ketamine as an adjuvant in sympathetic blocks for management of central sensitization following peripheral nerve injury

Proliferation of NMDA receptors and role of glutamate in producing central sensitization and 'wind up' phenomena in CRPS [complex regional pain syndrome] forms a strong basis for the use of Ketamine to block the cellular mechanisms that initiate and maintain these changes. In this case series, we describe 3 patients of CRPS Type II with debilitating central sensitization, heat/mechano allodynia and cognitive symptoms that we termed 'vicarious pain'. Each of these patients had dramatic relief with addition of Ketamine as an adjuvant to the sympathetic blocks after conventional therapy failed.

Case Reports

All 3 patients suffered gunshot wounds and developed characteristic features of CRPS Type II. Within 2–3 weeks they developed extraterritorial symptoms typical of central sensitization. The generalized mechanical allodynia and debilitating heat allodynia described to be rare in human subjects had life altering affect on their daily life. Case 2 and 3 also described an unusual cognitive phenomenon i.e. visual stimuli of friction would evoke severe pain in the affected limb that we have termed as 'vicarious pain'. They responded positively to sympathetic blocks but the sympatholysis did not bring relief to the heat and mechanical allodynia. Addition of Ketamine 0.5 mg/kg to the sympathetic blocks elicited resulted in marked relief in the allodynia.

Conclusion

Ketamine has a special role in patients with debilitating heat allodynia and positive cognitive symptoms via its action on central pain pathway. As an adjuvant in sympatholytic blocks it has a targeted action without significant neuropsychiatric side effects.

Oral ketamine for the treatment of type I complex regional pain syndrome

Ketamine has been shown to be effective in the treatment of neuropathic pain. We present a case of severe complex regional pain syndrome type 1 that was treated with oral ketamine. The response and tolerability of this preparation suggest that further study is warranted.

Iontophoretic administration of S(+)-ketamine in patients with intractable central pain: A placebo-controlled trial

The efficacy of 50 and 75 mg S(+)-ketamine administered daily by an iontophoresis-assisted transdermal drug delivery system was tested against placebo in a randomized, double-blind design in 33 patients with central neuropathic pain. At baseline and 1 week after the start of treatment subjects were evaluated with standard measures of efficacy: pain intensity measured by visual analog scale (VAS), health status (Pain Disability Index and EQ-5D) and quality of life (SF-36). Safety assessment included incidence and intensity of adverse events. No significant differences in pain scores (VAS) were observed between the ketamine groups and placebo during the course of the trial. Corrected for baseline levels, daily 50 mg S(+)-ketamine did not improve patient's health status or quality of life compared with placebo treatment. However, daily 75 mg S(+)-ketamine showed significant improvements on the Pain Disability Index, on the EQ-5D, and on the SF-36 except for the role-physical functioning and general health perception. Iontophoretic administration of S(+)-ketamine was well tolerated with a low incidence of adverse events (mild and transient in nature, resolving spontaneously). Iontophoretic administration of S(+)-ketamine was not more effective than placebo treatment in reducing pain scores in patients with severe central neuropathic pain. However, iontophoretic administration of 75 mg S(+)-ketamine improved the health status and the quality of life in these patients.

Neuropathic Pain: Implications for the Surgeon

Pharmacologic therapy for neuropathic pain is based on an evolving understanding of its underlying mechanisms, and often requires a patient,methodical sequence of trials that include the "four As": analgesics,antidepressants, anticonvulsants, and antiarrhythmics. Critical for success is a willingness to stay engaged with the patient to evolve a mutually acceptable plan and goals of care with realistic outcomes that emphasize symptom control and maximization of function. Such management is within the capabilities of surgeons for most patients, whereas the use of consultation and interdisciplinary supportive interventions from comprehensive pain management centers, if available, is helpful in more difficult cases.

Parenteral Ketamine as an Analgesic Adjuvant for Severe Pain: Development and Retrospective Audit of a Protocol for a Palliative Care Unit

BACKGROUND

Ketamine is an effective analgesic agent for treating a variety of neuropathic and cancer pain syndromes. Recent studies indicate that ketamine may have a particular role in the management of patients with neuropathic and/or pain syndromes that are poorly responsive to opioids.

OBJECTIVE

To develop, implement, and subsequently assess a protocol designed to maximize the analgesic effect of ketamine while minimizing its side effects.

DESIGN

A retrospective chart audit of 16 patients who had used the ketamine protocol over a 12-month period. Criteria for assessing the effectiveness of ketamine were defined.

RESULTS

Ketamine was an effective, well-tolerated analgesic adjuvant for 11 of 16 patients with previously uncontrolled pain. Pain scores were reduced by at least 4 of 10 in 15 of the 16 patients. Median opioid dose reduction on starting ketamine was 25%.

CONCLUSION

The audit confirmed the safety and effectiveness of ketamine as an analgesic adjuvant for patients with severe pain. Baseline opioid dose reduction and prophylactic use of haloperidol or benzodiazepine were effective in minimizing psychotomimetic side effects.

Ketamine in chronic pain management: an evidence-based review

Ketamine has diverse effects that may be of relevance to chronic pain including: N-methyl-D-aspartic acid, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, gamma-aminobutyric acid(A) receptors; inhibition of voltage gated Na(+) and K(+) channels and serotonin, dopamine re-uptake. Ketamine has been in clinical practice for over 30 yr; however, there has been little formal research on the effectiveness of ketamine for chronic pain management. In this review we evaluate the available clinical data as a basis for defining the potential use of ketamine for chronic pain. Literature referenced in this review was obtained from a computer search of EMBASE and MEDLINE from 1966 through August, 2002. Search terms included ketamine, ketalar, pain, painful, analgesic, and analgesia. Abstracts were screened for relevance and publications relating to chronic pain use were obtained. Levels of evidence were stratified according to accepted guidelines (level I-IV). For central pain, there is level II and level IV evidence of efficacy for parenteral and oral ketamine. For complex regional pain syndromes, there is only level IV evidence of efficacy of epidural ketamine. For fibromyalgia, there is level II evidence of pain relief, reduced tenderness at trigger points, and increased endurance. For ischemic pain, a level II study reported a potent dose-dependent analgesic effect, but with a narrow therapeutic window. For nonspecific neuropathic pain, level II and level IV studies reported divergent results with questionable long-term effects on pain. For phantom limb pain and postherpetic neuralgia, level II and level II studies provided objective evidence of reduced hyperpathia and pain relief was usually substantial either after parenteral or oral ketamine. Acute on chronic episodes of severe neuropathic pain represented the most frequent use of ketamine as a "third line analgesic," often by IV or subcutaneous infusion (level IV). In conclusion, the evidence for efficacy of ketamine for treatment of chronic pain is moderate to weak. However, in situations where standard analgesic options have failed ketamine is a reasonable "third line" option. Further controlled studies are needed.

Adjuvant ketamine analgesia for the management of cancer pain

OBJECTIVE

To review the clinical literature evaluating the utilization of intravenous ketamine for the management of cancer-related pain, to summarize the data that suggest ketamine is an appropriate adjuvant method of providing analgesia and to report a case of successful pain management using ketamine in a patient with recurrent testicular cancer at our institution.

DATA SOURCES

Primary literature was identified through a MEDLINE search (1966-March 2002), and additional information was obtained through secondary and tertiary sources.

DATA SYNTHESIS

The available data suggest that supplementation of morphine with ketamine improves analgesia in patients with cancer, and also provides insight to the controversy regarding the efficacy and adverse effects of various ketamine doses. At subanesthetic doses, ketamine may be beneficial at reducing opioid requirements and related adverse effects.

CASE SUMMARY

A 34-year-old white man with recurrent testicular cancer was admitted with radiating neuropathic pain of the legs and lower back. The patient was suspected to also be experiencing opioid adverse effects; therefore, alternative analgesic options were warranted. Ketamine was successful in reducing patient-reported pain and was also well tolerated.

CONCLUSIONS

Ketamine is an adjuvant analgesic for the treatment of cancer-related pain when other agents either fail or are intolerable. Accordingly, there are several factors that may prevent adequate pain control with opioid use; therefore, alternative analgesic options should be considered. Promise exists for ketamine as a contemporary analgesic in the appropriate patient.

Effects of low-dose ketamine on neuropathic pain: An electroencephalogram-electrooculogram/behavioral study

The aim of the present study was to clarify the neurophysiological changes associated with analgesic and behavioral effects of low-dose ketamine HCl in patients suffering from chronic neuropathic pain. Ten in-patients with neuropathic pain participated in this single-blind, placebo-controlled study after giving written informed consent. Following intravenous injections of a saline solution (placebo), three bolus injections of 5 mg ketamine HCl were administered at 5 min intervals. Changes in pain perception were assessed using a numerical rating scale for pain. Behavioral changes, including psychotomimetic effects, were assessed using the Brief Psychiatric Rating Scale (BPRS). Electroencephalograms (EEG) and electrooculograms (EOG) were recorded continuously throughout the testing period. One minute EEG and closed-eye eye movements were quantified. The effects of ketamine were evaluated by comparing the neurophysiological and behavioral parameters obtained from the placebo and ketamine trials. Pain reduction was significantly correlated with ketamine-induced changes in hallucinatory behavior and excitement as measured by the BPRS. Ketamine injections caused a significant decrease in the EEGalpha amplitude without an accompanying reduction in EEG frequency. The EEGalpha amplitude reduction at the right central electrode was significantly related to subjective pain relief. Subanesthetic doses of ketamine significantly decreased rapid eye movements, but did not initiate slow eye movements. In conclusion, the present EEG-EOG/behavioral results indicate that ketamine-induced failure of neural integration between cortical-subcortical regions induces psychotic symptoms and alters pain perception on neuropathic pain.

Low dose ketamine as an analgesic adjuvant in difficult pain syndromes: a strategy for conversion from parenteral to oral ketamine

Ketamine is a non-competitive N-methyl D-aspartate (NMDA) receptor antagonist with analgesic and dissociative anesthetic properties. Low dose or sub-anesthetic doses of ketamine have been used effectively as either a primary analgesic or analgesic adjuvant in a variety of pain syndromes. In this paper, three patients with difficult to treat, predominantly neuropathic pain syndromes will be described. Their pain syndromes were initially managed successfully with the addition of low dose parenteral ketamine as an analgesic adjuvant. The strategy of concurrently starting ketamine at a low dose, i.e., 40-60 mg over 24 hours, with a benzodiazepine proved effective in preventing psychotomimetic side effects. An unavoidable shortage of ketamine prompted a literature search, which suggested that the equianalgesic dose of oral ketamine could be lower than the parenteral dose. Subsequently the patients were converted to oral ketamine at doses 30 to 40% of the previous parenteral dose. Their pain syndromes remained controlled on the lower dose of oral ketamine with remarkably few side effects. The implications of this warrant further discussion and study.

Oral ketamine as an adjuvant to oral morphine for neuropathic pain in cancer patients

To evaluate the role of oral ketamine as an adjuvant to oral morphine in cancer patients experiencing neuropathic pain, 9 cancer patients (5 men, 4 women) taking maximally tolerated doses of either morphine, amitriptyline, sodium valproate, or a combination of these drugs for intractable neuropathic pain, and reporting a pain score of >6 on a 0-10 scale, were studied prospectively to evaluate analgesia and adverse effects. Ketamine in the dose of 0.5 mg/kg body weight three times daily was added to the existing drug regimen. Patients were taught to maintain a pain diary wherein they daily recorded their pain, sedation, and vomiting scores, and other side effects. A decrease of more than 3 from the baseline in the average pain score, or a score of < or =3 was taken as a successful response. Seven patients exhibited a decrease of more than 3. Four patients experienced nausea, of which one had vomiting. Two developed loss of appetite. Eight patients reported drowsiness during the first two weeks of therapy (P = 0.001), and this gradually improved over the next two weeks in 5 of these 8 patients. Three patients withdrew from the study, two owing to excessive sedation and another due to a "feeling of unreality." None of the patients reported visual or auditory hallucinations. This experience suggests that low dose oral ketamine is beneficial and effective in the management of intractable neuropathic pain in patients with advanced cancer. However, its utility is limited in some patients by the adverse effects that accompany its use.

Long-term treatment with ketamine in a 12-year-old girl with severe neuropathic pain caused by a cervical spinal tumor

A 12-year-old girl presented with head and neck pain, myoclonic movements, and decreased strength in all extremities caused by a cervical spinal tumor (glioblastoma multiforme). A partial resection of the tumor was performed. Three weeks later, she had superficial pain distributed in all dermatomes below her cervical medullary lesion. Touch (e.g., gentle hugs from relatives) and movements elicited paroxysm of intense pain. The pain was not relieved by increased doses of morphine. A test dose of ketamine (7.5 mg intravenous) provided an abrupt decrease in pain intensity, and continuous infusions of subcutaneous morphine and intravenous ketamine were started. Benzodiazepines were administered to avoid psychotomimetic effects from ketamine and to diminish myoclonic movements. The doses of analgesics and benzodiazepines were increasingly titrated (subcutaneous morphine 163-750 mg/24 hr, intravenous ketamine 36-410 mg/24 hr, subcutaneous midazolam 5-20 mg/24 hr, and intravenous diazepam 11.5-122.5 mg/24 hr) until her death 67 days after start of ketamine. She remained awake until the last day before her death. For the last 29 days of life, the pain treatment regimen was successfully continued in her home (400-km distance from the hospital). In conclusion, this case demonstrates that ketamine treatment may be effective in children with severe neuropathic pain not responsive to other analgesics. This patient also demonstrates the feasibility of long-term ketamine treatment in pediatric oncology and that such treatment can be administered in a home care setting.

Advances in cancer pain management

Control of malignant pain and related symptoms is paramount to clinical success in caring for cancer patients. To achieve the best quality of life for patients and families, oncologists and palliative care clinicians must work together to understand problems related to psychologic, social, and spiritual pain. Pain is the primary problem targeted for control using the World Health Organization's (WHO) analgesic ladder. This article focuses on increased knowledge of analgesic action that may enable expansion of the WHO analgesic ladder to fulfill the broader objectives of palliative medicine. We discuss clinical experience with several classes of drugs that are currently used to treat cancer pain: 1) nonsteroidal anti-inflammatory drugs, with emphasis on cyclooxygenase-2 inhibitors; 2) opioid analgesics, with specific emphasis on methadone and its newly recognized value in cancer pain; 3) ketamine, an antagonist at N-methyl-d-aspartate receptors; and 4) bisphosphonates, used for pain resulting from bone metastases. New concepts that compare molecular actions of morphine at excitatory opioid receptors, and methadone at nonopioid receptor systems, are presented to underscore the importance of balancing central nervous system excitatory (anti-analgesic) versus inhibitory (analgesic) influences.

Treatment of central post-stroke pain with oral ketamine

Case report of 68 year old female with central post-stroke pain successfully treated with oral ketamine. The patient's pain was refractory to conventional pain treatments and she had persistent right hemi-body neuropathic pain with allodynia and hyperalgesia. An intravenous ketamine trial, followed by oral ketamine with titration to 50mg three times a day was beneficial in decreasing allodynia and hyperalgesia, as well as improving functional capabilities. Known side effects including dysphoria, hallucinations, and paranoid feelings were attenuated with benzodiazepines.

Targeting the N-methyl-D-aspartate receptor for chronic pain management. Preclinical animal studies, recent clinical experience and future research directions

A 1967-1999 MEDLINE search of published reports evaluating the role of the glutamate N-methyl-D-aspartate (NMDA) receptor in pain identified 378 animal studies and 132 human studies. There is convincing evidence in these studies that the NMDA receptor mediates prolonged nociceptive behaviors in animal models and various chronic pain symptoms in the clinical population. Administration of older compounds, such as ketamine, dextromethorphan, and amantadine, which are now known to act as NMDA receptor antagonists, have recently been shown to alleviate chronic pain. For years, the pharmaceutical industry has been attempting to produce novel compounds that modulate NMDA receptor activity; however, the adverse effects associated with this class of drugs have prevented their widespread clinical use. Collaborative studies between basic researchers, clinical scientists, and clinicians are needed to delineate characteristics of NMDA receptor antagonism that predict optimal analgesic activity and an acceptable toxicity profile in patients with chronic pain.

Novel drugs for neuropathic pain

Neuropathic pain is often inadequately controlled by conventional analgesics. Because the aetiology of neuropathic pain is only partially understood, specific treatment approaches have not been defined. A variety of pharmacological treatments have been proposed. However, for only a small minority of drugs used in neuropathic pain has the scientific evidence been evaluated in a satisfactory manner. The present review of the recent literature reveals the potential of certain novel drugs in treatment of neuropathic pain.

Advances in cancer pain management

Control of malignant pain and related symptoms is paramount to clinical success in caring for cancer patients. To achieve the best quality of life for patients and families, oncologists and palliative care clinicians must work together to understand problems related to psychologic, social, and spiritual pain. Pain is the primary problem targeted for control using the World Health Organization's (WHO) analgesic ladder. This article focuses on increased knowledge of analgesic action that may enable expansion of the WHO analgesic ladder to fulfill the broader objectives of palliative medicine. We discuss clinical experience with several classes of drugs that are currently used to treat cancer pain: 1) nonsteroidal anti-inflammatory drugs (NSAIDs), with emphasis on cyclooxygenase-2 (COX-2) inhibitors; 2) opioid analgesics, with specific emphasis on methadone and its newly recognized value in cancer pain; 3) ketamine, an antagonist at N-methyl d-aspartate (NMDA) receptors; and 4) bisphosphonates, used for pain resulting from bone metastases. New concepts that compare molecular actions of morphine at excitatory opioid receptors, and methadone at non-opioid receptor systems, are presented to underscore the importance of balancing central nervous system excitatory (anti-analgesic) versus inhibitory (analgesic) influences.