Continuous subcutaneous injection of ketamine for cancer pain

Should Subanesthetic Ketamine be Considered When Managing Opioid Refractory Cancer Pain?

In the cancer pain setting, ketamine has been typically employed as a co-analgesic for opioid refractory and neuropathic pain. One controversial topic is whether subanesthetic ketamine be considered when managing opioid refractory cancer pain. In this "Controversies in Palliative Care" article, three clinicians independently answer this question. Specifically, each clinician provides a synopsis of the key studies that inform their thought processes, share practical advice on their clinical approach, and highlight the opportunities for future research. Three independent clinicians reported a divergence of opinion regarding the usefulness of subanesthetic ketamine for managing opioid refractory cancer pain. All investigators acknowledged the lack of high-quality trials. All agreed on the need for adequately powered trials, the development of standardized methodology, and the exploration of any patient sub-populations that may benefit from ketamine for cancer related pain.

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: A Practical Review for the Consultation-Liaison Psychiatrist

BACKGROUND

Ketamine is a noncompetitive N-methyl-D-aspartate-receptor antagonist often used for sedation and management of acute agitation in general hospital settings. Many hospitals now include ketamine as part of their standard agitation protocol, and consultation-liaison psychiatrists frequently find themselves treating patients who have received ketamine, despite lack of clear recommendations for management.

OBJECTIVE

Conduct a nonsystematic narrative review regarding the use of ketamine for agitation and continuous sedation, including benefits and adverse psychiatric effects. Compare ketamine to more traditional agents of agitation control. Provide consultation-liaison psychiatrists with a summary of available knowledge and recommendations for managing patients receiving ketamine.

METHODS

A literature review was performed using PubMed, querying published articles from inception to March 2023 for articles related to use of ketamine for agitation or continuous sedation and side effects including psychosis and catatonia.

RESULTS

A total of 37 articles were included. Ketamine was found to have multiple benefits, including shorter time to adequate sedation for agitated patients when compared to haloperidol ± benzodiazepines and unique advantages for continuous sedation. However, ketamine carries significant medical risks including high rates of intubation. Ketamine appears to induce a syndrome that mimics schizophrenia in healthy controls, and such effects are more pronounced and longer-lasting in patients with schizophrenia. Evidence regarding rates of delirium with ketamine for continuous sedation is mixed and requires further investigation before the agent is widely adopted for this purpose. Finally, the diagnosis of "excited delirium syndrome" and use of ketamine to treat this controversial syndrome warrants critical evaluation.

CONCLUSIONS

Ketamine carries many potential benefits and can be an appropriate medication for patients with profound undifferentiated agitation. However, intubation rates remain high, and ketamine may worsen underlying psychotic disorders. It is essential that consultation-liaison psychiatrists understand the advantages, disadvantages, biased administration, and areas of limited knowledge regarding ketamine.

Subcutaneous Drugs and Off-label Use in Hospice and Palliative Care: A Scoping Review

BACKGROUND

Subcutaneous drug administration is an interesting approach for symptom control in hospice and palliative care. However, most drugs have no marketing authorization for subcutaneous administration and are therefore used off-label. In order to meet the requirements of a safe and effective drug therapy, especially in highly vulnerable patients, it is essential to investigate the scope of evidence of these common practices.

OBJECTIVES

The purpose of this scoping review was to provide an overview of available data on the tolerability and/or effectiveness of subcutaneously administered and off-label used drugs.

METHOD

We performed a scoping review according to the PRISMA extension to identify data available on the tolerability and/or effectiveness of 17 predefined drugs that are commonly administered subcutaneously in Swiss hospices and hospice-like institutions and that have no marketing authorization (off-label use).

RESULTS

The scoping review identified 57 studies with most data available on their tolerability (68% local, 54% systemic), clinical effects (82%), details on dosage (96%) and routes of application (100%). Information on pharmacokinetic properties was mostly missing and only available for fentanyl, levetiracetam, midazolam, and ondansetron. For seven drugs, less than five articles were identified and no studies on codeine or clonazepam were available.

CONCLUSION

This work provides an overview of current evidence on subcutaneous and off-label used drugs in hospice and palliative care. Although both are common practices, evidence on tolerability and effectiveness, particularly pharmacokinetic data, is limited and the identified information gaps need to be closed. This work establishes a basis for further research in this area.

A rapid positive influence of S-ketamine on the anxiety of patients in palliative care: a retrospective pilot study

BACKGROUND

Patients in palliative care need rapid-acting pharmacological options for psychological distress. N-methyl-D-aspartate antagonist ketamine is known to have a fast onset of anti-depressant and anxiolytic action. Its S-enantiomer S-ketamine (or esketamine) is an analgesic used as a routine treatment for refractory pain as an intravenous infusion (0.25 mg/kg over 45 min). This study investigates whether S-ketamine pain therapy has a positive impact on psychological distress caused by anxiety and depression in palliative care.

METHODS

Patient routine data from a palliative care unit of a tertiary care hospital were used in a retrospective analysis after positive ethics approval. Eight patients, who received analgesic S-ketamine treatment, were compared to a control group matched by gender and age. The main analysis was conducted using three-way mixed MANOVA followed by two-way mixed ANOVA. Target variables were the values for anxiety and depression in the state-trait anxiety-depression inventory STADI. The predictor variables were the time of measurement before (T1) and after (T2) S-ketamine application and group membership.

RESULTS

Comparison of the S-ketamine group (n = 8; 4 male, 4 female; average age 52 years) with the control group (n = 8; 3 male, 5 female; average age 55 years) revealed a significant multivariate effect on anxiety and depression F(1, 14) = 4.78; p = 0.046; r = 0.50. The univariate comparisons showed a significant reduction of the anxiety scores from T1 to T2 in the S-ketamine group compared to the control group F(1, 14) = 10.14; p = 0.007; r = 0.65. With regard to depression, there was no significant reduction from T1 to T2 in the group comparison F(1, 14) = 1.60; p = 0.23; r = 0.32. No long-lasting effects on pain were found.

CONCLUSIONS

Our findings show that psychological distress of patients in palliative care may improve after a single administration of S-ketamine, which mainly alleviates anxiety in those patients. Limitations of this study arise from non-randomization, retrospective analysis and low sample size. Therefore, further prospective and ideally randomized studies are necessary.

Ketamine for pain management

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Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

This is an update of a review first published in 2003 and updated in 2012.Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of refractory cancer pain, when opioids alone or in combination with appropriate adjuvant analgesics prove to be ineffective. Ketamine is known to have psychomimetic (including hallucinogenic), urological, and hepatic adverse effects.

OBJECTIVES

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

SEARCH METHODS

For this update, we searched MEDLINE (OVID) to December 2016. We searched CENTRAL (CRSO), Embase (OVID) and two clinical trial registries to January 2017.

SELECTION CRITERIA

The intervention considered by this review was the addition of ketamine, given by any route of administration, in any dose, to pre-existing opioid treatment given by any route and in any dose, compared with placebo or active control. We included studies with a group size of at least 10 participants who completed the trial.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results and performed 'Risk of bias' assessments. We aimed to extract data on patient-reported pain intensity, total opioid consumption over the study period; use of rescue medication; adverse events; measures of patient satisfaction/preference; function; and distress. We also assessed participant withdrawal (dropout) from trial. We assessed the quality of the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation).

MAIN RESULTS

One new study (185 participants) was identified by the updated search and included in the review. We included a total of three studies in this update.Two small studies, both with cross-over design, with 20 and 10 participants respectively, were eligible for inclusion in the original review. One study with 20 participants examined the addition of intrathecal ketamine to intrathecal morphine, compared with intrathecal morphine alone. The second study with 10 participants examined the addition of intravenous ketamine bolus in two different doses to ongoing morphine therapy, compared with placebo. Both of these studies reported reduction in pain intensity and reduction in morphine requirements when ketamine was added to opioid for refractory cancer pain. The new study identified by the updated search had a parallel group design and 185 participants. This placebo-controlled study examined rapid titration of subcutaneous ketamine to high dose (500 mg) in participants who were using different opioids. There were no differences between groups for patient-reported pain intensity.Pooling of the data from the three included trials was not appropriate because of clinical heterogeneity.The study examining intrathecal drug administration reported no adverse events related to ketamine. In the study using intravenous bolus administration, ketamine caused hallucinations in four of 10 participants. In the rapid dose escalation/high-dose subcutaneous ketamine study, there was almost twice the incidence of adverse events in the ketamine group, compared to the placebo group, with the most common adverse events being needle site irritation and cognitive disturbance. Two serious adverse events (bradyarrhythmia and cardiac arrest) thought to be related to ketamine were also reported in this trial.For all three studies there was an unclear risk of bias overall. Using GRADE, we judged the quality of the evidence to be very low due to study limitations and imprecision due to the small number of participants in all comparisons.

AUTHORS' CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of refractory cancer pain. The evidence was of very low quality, meaning that it does not provide a reliable indication of the likely effect, and the likelihood that the effect will be substantially different is high. Rapid dose escalation of ketamine to high dose (500 mg) does not appear to have clinical benefit and may be associated with serious adverse events. More randomised controlled trials (RCTs) examining specific low-dose ketamine clinical regimens in current use are needed.

Subcutaneous fluid and drug delivery: safe, efficient and inexpensive

Patients with difficult venous access or oral intolerance and clinical situations with inadequate response to oral therapy have generated the need for alternative routes of delivery for drugs and fluids.

The purpose of this study was to conduct a systematic review examining the evidence for subcutaneous (SC) administration of drugs and/or fluids.

We used a broad search strategy using electronic databases CINAHL, EMBASE, PubMed and Cochrane library, key terms and ‘Medical Subject Headings’ (MeSH) such as ‘subcutaneous route’, ‘hypodermoclysis’ and the name/group of the most used drugs via this route (e.g. ‘ketorolac, morphine, ceftriaxone’, ‘analgesics, opioids, antibiotics’).

We conclude that the SC route is an effective alternative for rehydration in patients with mild–moderate dehydration and offers a number of potential advantages in appropriately selected scenarios. Experience of administering drugs by this route suggests that it is well tolerated and is associated with minimal side-effects.

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.

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.

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.

Dissociative conscious sedation, an alternative to general anesthesia for laparoscopic peritoneal dialysis catheter implantation: a randomized trial comparing intravenous and subcutaneous ketamine

Laparoscopy is an effective method of implantation for peritoneal dialysis (PD) catheters. Use of the laparoscopic technique is increasing because of its potential advantages over other techniques. In most patients, selection for PD is based on negative criteria, and because of the need for general anesthesia, the laparoscopic technique can be life-threatening in these patients. On the other hand, local anesthesia is insufficient for laparoscopic catheter implantation. To avoid the need for general anesthesia and to achieve patient safety and satisfaction, we designed a type of conscious sedation (dissociative conscious sedation) and compared the efficacy of subcutaneous (SC) and intravenous (IV) ketamine added to narcotics in patients scheduled for laparoscopic implantation of a PD catheter.

METHODS

Our prospective randomized double-blind study enrolled 60 adult patients with chronic renal failure who were scheduled for laparoscopic implantation of a PD catheter. Patients were randomly assigned to one of two groups: one receiving IV ketamine, and the other receiving SC ketamine. In both groups, patients were premedicated with IV midazolam 0.015 mg/kg, fentanyl 1-2 μg/kg, and lidocaine 1.5 mg/kg. Patients then received 0.6 mg/kg ketamine either intravenously (IV group) or by subcutaneous injection at the anterior aspect of the forearm (SC group). If systolic blood pressure (BP) increased more than 20% from baseline or exceeded 170 mmHg, IV nitroglycerine (TNG) 50 μg was administered incrementally (repeated 50-μg doses). After a desirable level of conscious sedation was achieved, local anesthesia and nitrous oxide pneumoperitoneum were applied, and the PD catheter was implanted under laparoscopic guidance. Heart rate and BP were measured throughout the procedure. Adverse effects and recovery events were recorded.

RESULTS

All patients tolerated the procedure well. Administration of TNG was significantly more frequent in the IV ketamine group. Pain intensity during the surgery was similar in both groups. Both groups were comparable with regard to heart rate, but patients in the SC ketamine group had a significantly lower systolic BP at the 2nd measurement and a lower rate-pressure product at the 2nd, 4th, and 5th measurements. All patients in the SC ketamine group were cooperative during surgery and experienced uneventful recoveries; mild hallucinations were observed in 5 patients in the IV ketamine group. In the IV ketamine group, 3 patients lost the ability to cooperate during surgery. All catheters were successfully placed.

CONCLUSIONS

Dissociative conscious sedation is an acceptable alternative to general anesthesia in laparoscopic implantation of the PD catheter. Ketamine by the SC route is as effective as, but safer than, IV ketamine.

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.

Prospective audit of short-term concurrent ketamine, opioid and anti-inflammatory (‘triple-agent’) therapy for episodes of acute on chronic pain

AIM

This prospective audit was undertaken in order to document the analgesic response and adverse effects of concurrent short-term ('burst') triple-agent analgesic (ketamine, an opioid and an anti-inflammatory agent--either steroidal or non-steroidal) administration, for episodes of acute on chronic pain. The clinical hypothesis in this study is that better pain control may be obtained by simultaneous multiple target receptor blockade.

METHOD

The response of 18 patients is reported. The pain and analgesic requirement data for the 24 h before starting triple-agent therapy were compared with the last 24 h on the triple-agent therapy. Patients were then classified as responders or non-responders.

RESULTS

According to stringent clinical criteria, 12 out of the 18 patients were classified as responders. The response rate was highest for somatic pain (7/9) and appeared to decrease with duration of prior uncontrolled pain. Only four out of the 18 patients reported adverse effects and all of these were minor.

CONCLUSIONS

The results suggest that this 'burst' triple-agent approach is safe and effective in an inpatient palliative care population during episodes of poorly controlled acute on chronic pain, and warrants further investigation to ascertain whether it gives superior results compared to the 'gold-standard' WHO ladder approach.

Ketamine as adjuvant to opioids for cancer pain. A qualitative systematic review

Ketamine is increasingly being used as an adjuvant to opioids in the treatment of refractory cancer pain. This systematic review examines the available evidence. Randomized, controlled trials, with or without crossover, were included. Studies were identified from MEDLINE, EMBASE, CANCERLIT, the Cochrane Library, handsearched reference lists from review articles and chapters from standard textbooks on pain and palliative care and reference lists from papers retrieved. Four randomized, controlled studies were identified. Two were excluded due to poor quality. Both included studies concluded that ketamine improves morphine treatment in cancer pain. Quantitative meta-analysis was not possible. The available evidence is not sufficient to conclude that ketamine improves the effectiveness of opioid treatment in cancer pain. High quality, randomized, controlled trials with larger numbers of patients and standardized, clinically relevant routes of administration of ketamine are needed.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

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 hallucinogenic side effects. To date no systematic review of the benefits and harms of adjuvant ketamine for cancer pain has been undertaken.

OBJECTIVES

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

SEARCH STRATEGY

Studies were identified from MEDLINE (1966-2001), EMBASE (1980-2001), CancerLit (1966-2001), 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.

SELECTION CRITERIA

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.

DATA COLLECTION AND ANALYSIS

Two independent reviewers 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 reviewers, and two RCTs were excluded because of inappropriate study design. Patient reported pain intensity and pain relief was assessed using visual analog scales, verbal rating scales or other validated scales, and adverse effects data were collated.

MAIN RESULTS

Two trials were eligible for inclusion in the 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 patients (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.

REVIEWER'S CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of cancer pain. More randomized controlled trials are needed.

Advances in cancer pain management

Although most patients with cancer pain can attain a favorable balance between analgesia and side effects with a conventional approach to opioid therapy, a substantial minority cannot. For these patients, an important subgroup of whom have neuropathic pain, alternative therapeutic strategies are needed. With a detailed assessment, clinicians should be able to choose among the large and diverse group of options available and implement an approach, or combination of approaches, that have a high probability of improving analgesic outcomes.

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.

"Burst" ketamine for refractory cancer pain: an open-label audit of 39 patients

The results of a novel approach to the use of ketamine in refractory cancer pain are reported. In this prospective, multicenter, unblinded, open-label audit, 39 patients (with a total of 43 pains) received a short duration (3 to 5 days) ketamine infusion. The initial dose of 100 mg/24 hr was escalated if required to 300 mg/24 hr and then to a maximum dose of 500 mg/24hr. The overall response rate was 29/43 (67%). Analysis of results according to pain mechanisms showed that 15/17 somatic and 14/23 neuropathic pains responded. In 5 patients who appeared to respond, it is possible that another concurrent intervention may have contributed in whole or part for the pain relief observed. After cessation of ketamine, 24/29 maintained good pain control, with a maximum documented duration of eight weeks. However, 5 of the initial 29 responders experienced a recurrence of pain within 24 hours, and ketamine was recommenced. Of these, 2 underwent another intervention for pain control while 3 continued on ketamine until their deaths between two and four weeks later. Twelve patients reported adverse psychomimetic effects, with the incidence rising with increasing dose. Four of these were non-responders and the ketamine was stopped. Eight were responders, and in 3 the adverse effects were rendered acceptable with dose reduction; the other 5 rejected a dose reduction. The results reported suggest the need for further investigation of the place of ketamine in cancer pain management.

Opioid poorly-responsive cancer pain. Part 3. Clinical strategies to improve opioid responsiveness

Some pain syndromes may be difficult to treat due to a poor response to opioids. This situation demands a range of alternative measures, including the use of adjuvant drugs with independent effects, such as antidepressants, sodium channel-blocking agents, steroids and anti-inflammatory drugs (NSAIDs); drugs that reduce opioid side effects; and drugs that enhance analgesia produced by opioids, such as N-methyl-D-aspartate (NMDA) antagonists, calcium channel antagonists, and clonidine. Other approaches, including opioid trials, neural blockade when necessary, and psychological interventions, also may be useful.

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.

Analgesic effect of intravenous ketamine in cancer patients on morphine therapy: a randomized, controlled, double-blind, crossover, double-dose study

Pain not responsive to morphine is often problematic. Animal and clinical studies have suggested that N-methyl-D-aspartate (NMDA) antagonists, such as ketamine, may be effective in improving opioid analgesia in difficult pain syndromes, such as neuropathic pain. A slow bolus of subhypnotic doses of ketamine (0.25 mg/kg or 0.50 mg/kg) was given to 10 cancer patients whose pain was unrelieved by morphine in a randomized, double-blind, crossover, double-dose study. Pain intensity on a 0 to 10 numerical scale; nausea and vomiting, drowsiness, confusion, and dry mouth, using a scale from 0 to 3 (not at all, slight, a lot, awful); Mini-Mental State Examination (MMSE) (0-30); and arterial pressure were recorded before administration of drugs (T0) and after 30 minutes (T30), 60 minutes (T60), 120 minutes (T120), and 180 minutes (T180). Ketamine, but not saline solution, significantly reduced the pain intensity in almost all the patients at both doses. This effect was more relevant in patients treated with higher doses. Hallucinations occurred in 4 patients, and an unpleasant sensation ("empty head") was also reported by 2 patients. These episodes reversed after the administration of diazepam 1 mg intravenously. Significant increases in drowsiness were reported in patients treated with ketamine in both groups and were more marked with ketamine 0.50 mg/kg. A significant difference in MMSE was observed at T30 in patients who received 0.50 mg/kg of ketamine. Ketamine can improve morphine analgesia in difficult pain syndromes, such as neuropathic pain. However, the occurrence of central adverse effects should be taken into account, especially when using higher doses. This observation should be tested in studies of prolonged ketamine administration.

Different effects of NMDA/group I metabotropic glutamate receptor agents in delta- and mu-opioid receptor agonist-induced supraspinal antinociception

The N-methyl-D-aspartate (NMDA) and metabotropic glutamate (mGlu) receptors are involved in nociceptive transmission in the central nervous system. The present study was designed to study the effects of NMDA and group I mGlu receptor agents on delta- and mu-opioid receptor agonist-induced antinociception in the mouse brain. Intracerebroventricular (i.c.v.) treatment with the non-competitive NMDA receptor antagonist dizocilpine and the group I mGlu receptor antagonist (S)-4-carboxyphenylglycine ((S)-4CPG) significantly attenuated the antinociception induced by the delta-opioid receptor agonists [D-Pen(2), Pen(5)]enkephalin (DPDPE), (-)-TAN 67 and [D-Ala(2)]deltorphin II. On the contrary, i.c.v. administration of dizocilpine and (S)-4CPG slightly but significantly enhanced the antinociception induced by the mu-opioid receptor agonist [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]enkephalin (DAMGO). Under these conditions, i.c.v. administration of NMDA and the group I mGlu receptor agonist 3,5-dihydrophenylglycine (DHPG) significantly enhanced the antinociception induced by delta-opioid receptor agonists, whereas both reduced DAMGO-induced antinociception. These findings suggest that the supraspinal antinociceptive actions of mu- and delta-opioid receptor agonists appear to be modulated differently by NMDA and group I mGlu receptors in the mouse.

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

Ketamine is an injectable anesthetic induction agent that has been reported to have analgesic activity in pain from a variety of mechanisms, but predominantly in neuralgic and dysesthetic neuropathic pain. In this case report we illustrate the effectiveness of ketamine in a patient with neuropathic pain resulting from cauda equina trauma. Among the issues addressed are the role of pretreatment with haloperidol to prevent ketamine-induced psychomimetic effects, the potential for fewer side effects and a need for lower doses when ketamine is administered orally, and the need for further study regarding appropriate monitoring parameters during the titration phase. Oral ketamine can be effective in treatment refractory chronic neuropathic pain of spinal origin.

Low-dose ketamine in the management of opioid nonresponsive terminal cancer pain

Two patients with far-advanced cancer, near death, who were experiencing excruciating and intractable pain that was poorly responsive to rapidly escalating doses of morphine and hydromorphone were treated with low-dose intravenous ketamine (0.1-0.2 mg/kg). This intervention eliminated the need for any further opioid use, providing profound analgesia and a sense of calm during the last hours and days of these patients' lives. These case reports add to the small but growing body of clinical literature suggesting that ketamine may have a significant place in the care of patients with pain that is poorly responsive to opioids, or who experience dose-limiting adverse effects, near the end of life. This is an important matter to disseminate in order to reassure the public that we do have the tools necessary to keep the promise that no one need die with uncontrolled pain. This therapeutic approach may also serve to reassure concerned physicians that their efforts to assure pain relief may not be misconstrued as hastening death.

Analgesic and cognitive effects of intravenous ketamine-alfentanil combinations versus either drug alone after intradermal capsaicin in normal subjects

Combinations of opioids and N-methyl-D-aspartate (NMDA) antagonists enhance acute antinociception and reduce opioid tolerance in some animal experiments but have received little rigorous study in humans. To quantitatively assess the nature of the interaction of these two classes of drugs in producing analgesia and cognitive impairment, we compared i.v. infusions of ketamine, alfentanil, and ketamine-alfentanil combinations in 12 normal volunteers after an intradermal injection of capsaicin. Drug doses for a 70-kg subject in this six-session, randomized, double-blind, cross-over study were: ketamine 20 mg, ketamine 5 mg, alfentanil 2 mg, alfentanil 0.5 mg, ketamine 10 mg + alfentanil 1 mg, and ketamine 2.5 mg + alfentanil 0.25 mg, given over 35 min. Outcome measures were background pain, area and magnitude of hyperalgesia to pinprick, and cognitive performance on the Digit Symbol Substitution Test and the Perception Speed Test. The results demonstrated simple additivity for the effects of ketamine and alfentanil on pain, pinprick hyperalgesia, and cognitive impairment. We conclude that, at least in this experimental pain model, there is no clear advantage or disadvantage of a ketamine-alfentanil combination over equianalgesic doses of either component.

IMPLICATIONS

In a double-blind, controlled trial, we administered doses of an opioid analgesic (alfentanil), an N-methyl-D-aspartate receptor antagonist (ketamine), or their combination to normal volunteers and found no advantage of the combination over a larger dose of either drug alone in relieving pain caused by painful chemical stimulation.

Ketamine injection used orally

Ketamine has been used parenterally for pain unresponsive to opioids, including neuropathic pain, and has also been used as an alternative analgesic agent after surgery. Although oral administration of ketamine has been used for some time as a single dose, it has not been given by this route on a regular basis. The use of ketamine administered orally is described for two patients with severe neuropathic pain who were intolerant of, or whose pain was unrelieved by, more commonly used agents. Pain relief was achieved without significant side effects.

Long-term ketamine subcutaneous continuous infusion in neuropathic cancer pain

Neuropathic cancer pain may be less responsive to opioids than other pain. Several studies suggest that N-methyl-D-aspartate (NMDA)-receptor antagonists could play a role in the treatment of neuropathic pain. Ketamine is an NMDA-receptor antagonist that is used as an anesthetic and has been suggested as a useful drug for neuropathic pain. Subanesthetic doses of ketamine can yield analgesia without hypnosis. We describe a patient who developed neuropathic cancer pain unresponsive to opioid escalation and spinal administration of a combination of bupivacaine-morphine and was subsequently treated by subcutaneous continuous ketamine infusion. A starting dose of 150 mg/day provided good pain relief and a dramatic reduction of the oral morphine dose (from 5 g to 200 mg). A slow and progressive increase of ketamine and morphine dosage (400 mg and 200 mg by the subcutaneous route, respectively) continued to provide adequate pain relief after 13 months of therapy despite signs of progressive disease.

Continuous subcutaneous administration of the N-methyl-D-aspartic acid (NMDA) receptor antagonist ketamine in the treatment of post-herpetic neuralgia

The effect of continuous subcutaneous (s.c.) infusion of ketamine on nerve injury pain was examined in patients with post-herpetic neuralgia. Five patients that reported pain relief after acute intravenous injection of ketamine were included in this open prospective study. Ketamine was administered continuously in increasing doses using a portable infusion pump (CADD-PLUS, Pharmacia), and the treatment period for each infusion rate (0.05, 0.075, 0.10, or 0.15 mg/kg/h) was 7 days and nights. Relief of continuous pain, as evaluated daily by visual analogue scales, was observed at the infusion rate of 0.05 mg/kg/h, but was most marked during infusion of 0.15 mg/kg/h. All the patients reported that ketamine reduced the severity of continuous pain as well as reduced the severity and number of attacks of spontaneous pain. Changes in evoked pain (allodynia and wind-up-like pain) were recorded before change of infusion rate. Allodynia was maximally reduced 59-100% after 1 week infusion of 0.05 mg/kg/h, and wind-up-like pain was maximally reduced 60-100% after 1 week infusion of 0.15 mg/kg/h. Itching and painful indurations at the injection site was the most bothersome side-effect and for this reason 1 patient discontinued treatment after 2 weeks. Other common side-effects were nausea, fatigue and dizziness. The present results show that continuous, spontaneous and evoked pain in patients with post-herpetic neuralgia is reduced by continuous s.c. infusion of ketamine, but is associated with intolerable side effects.

Effective treatment of severe cancer pain of the head using low-dose ketamine in an opioid-tolerant patient

We report the case of a 39-year-old man with severe pain due to unresectable squamous-cell carcinoma of the maxillary sinus that had invaded cranial bone and had metastasized to the cervical spine. Tolerance to opioids had developed, and high doses of transdermal, continuous intravenous, and epidural opioids did not control his pain. An acute episode of extremely severe head pain was immediately controlled with a subanesthetic dose of ketamine after failure of a stress dose of corticosteroid and intravenous lidocaine. Because the patient was terminally ill and invasive procedures were not options, we controlled his pain using a low-dose ketamine infusion until his death 13 days later. Ketamine may be a good co-analgesic for breakthrough pain and for severe pain caused by terminal cancer when invasive techniques are inappropriate. Its mechanism of action may include reversal of opioid tolerance in addition to an inherent analgesic effect.

Spinal analgesia in terminal care: risk versus benefit

Cancer pain treatment is well established. The World Health Organization provides clinicians an "analgesic ladder" scheme to optimize cancer pain treatment. At the beginning of the pain treatment, oral analgesic administration is preferred. The analgesic dose must be individualized. Many published papers describe the spinal administration of opioids in combination with various other drugs such as bupivacaine in selected patients with cancer pain. Although complications have been reported to be few, some recent reports debate this idea. We first describe a population of 92 cancer patients, 13 of whom received intrathecal morphine. We then present our experience with a separate group of 33 cancer patients who were also managed using intrathecal morphine. Based on this experience, the generally accepted indications for the technique appeared to be justified. Concern about spinal infection is well considered, however. Three out of those patients developed meningitis, a complication rate that is far too high.

Response of chronic neuropathic pain syndromes to ketamine: a preliminary study

Hyperactivity of N-methyl-D-aspartate (NMDA) receptors may be one of the factors in the genesis of neuropathic pain. Ketamine is an NMDA-blocking agent widely used in human medicine. Ketamine (at 250 mcg/kg i.v. slow push) was administered to 6 patients for control of chronic neuropathic pain syndromes in double-blind placebo-controlled fashion. All 3 patients with peripheral nervous system (PNS) disease-related pain, and 2 of 3 patients with central pain and dysesthesia syndromes responded with a temporary decrease in the rating of ongoing pain. The allodynia, hyperalgesia and after-sensation present in 5 patients improved after the administration of ketamine. Dose-response estimation in 2 patients with PNS-related neuropathic pain revealed that ketamine was effective in dose-related fashion. Continuous subcutaneous infusion of ketamine administered to 1 patient with PNS-related neuropathic pain caused no additional improvement in pain control but caused intolerable cognitive and memory side effects. In contrast, side effects during single-dose injections were mild and well tolerated. Ketamine affected the evoked pain and associated after-sensation in chronic neuropathic pain syndromes more than the ongoing constant pain.

Ketamine hydrochloride in the treatment of phantom limb pain

Three cases are described in which phantom limb pain was successfully treated with ketamine hydrochloride. Possible mechanisms for this observation are suggested.