Gabapentin for Neuropathic Cancer Pain: A Randomized Controlled Trial From the Gabapentin Cancer Pain Study Group

Implementation of a publication strategy in the context of reporting biases. A case study based on new documents from Neurontin litigation

Background

Previous studies have documented strategies to promote off-label use of drugs using journal publications and other means. Few studies have presented internal company communications that discussed financial reasons for manipulating the scholarly record related to off-label indications. The objective of this study was to build on previous studies to illustrate implementation of a publication strategy by the drug manufacturer for four off-label uses of gabapentin (Neurontin®, Pfizer, Inc.): migraine prophylaxis, treatment of bipolar disorders, neuropathic pain, and nociceptive pain.

Methods

We included in this study internal company documents, email correspondence, memoranda, study protocols and reports that were made publicly available in 2008 as part of litigation brought by consumers and health insurers against Pfizer for fraudulent sales practices in its marketing of gabapentin (see http://pacer.mad.uscourts.gov/dc/cgi-bin/recentops.pl?filename=saris/pdf/ucl%20opinion.pdf for the Court’s findings).

We reviewed documents pertaining to 20 clinical trials, 12 of which were published. We categorized our observations related to reporting biases and linked them with topics covered in internal documents, that is, deciding what should and should not be published and how to spin the study findings (re-framing study results to explain away unfavorable findings or to emphasize favorable findings); and where and when findings should be published and by whom.

Results

We present extracts from internal company marketing assessments recommending that Pfizer and Parke-Davis (Pfizer acquired Parke-Davis in 2000) adopt a publication strategy to conduct trials and disseminate trial findings for unapproved uses rather than an indication strategy to obtain regulatory approval. We show internal company email correspondence and documents revealing how publication content was influenced and spin was applied; how the company selected where trial findings would be presented or published; how publication of study results was delayed; and the role of ghost authorship.

Conclusions

Taken together, the extracts we present from internal company documents illustrate implementation of a strategy at odds with unbiased study conduct and dissemination. Our findings suggest that Pfizer and Parke-Davis’s publication strategy had the potential to distort the scientific literature, and thus misinform healthcare decision-makers.

Combination pharmacotherapy for the treatment of neuropathic pain in adults

BACKGROUND

Pharmacotherapy remains an important modality for the treatment of neuropathic pain. However, as monotherapy current drugs are associated with limited efficacy and dose-related side effects. Combining two or more different drugs may improve analgesic efficacy and, in some situations, reduce overall side effects (e.g. if synergistic interactions allow for dose reductions of combined drugs).

OBJECTIVES

This review evaluated the efficacy, tolerability and safety of various drug combinations for the treatment of neuropathic pain.

SEARCH METHODS

We identified randomised controlled trials (RCTs) of various drug combinations for neuropathic pain from CENTRAL, MEDLINE, EMBASE and handsearches of other reviews and trial registries. The most recent search was performed on 9 April 2012.

SELECTION CRITERIA

Double-blind, randomised studies comparing combinations of two or more drugs (systemic or topical) to placebo and/or at least one other comparator for the treatment of neuropathic pain.

DATA COLLECTION AND ANALYSIS

Data extracted from each study included: proportion of participants a) reporting ≥ 30% pain reduction from baseline OR ≥ moderate pain relief OR ≥ moderate global improvement; b) dropping out of the trial due to treatment-emergent adverse effects; c) reporting each specific adverse effect (e.g. sedation, dizziness) of ≥ moderate severity. The primary comparison of interest was between study drug(s) and one or both single-agent comparators. We combined studies if they evaluated the same drug class combination at roughly similar doses and durations of treatment. We used RevMan 5 to analyse data for binary outcomes.

MAIN RESULTS

We identified 21 eligible studies: four (578 participants) evaluated the combination of an opioid with gabapentin or pregabalin; two (77 participants) evaluated an opioid with a tricyclic antidepressant; one (56 participants) of gabapentin and nortriptyline; one (120 participants) of gabapentin and alpha-lipoic acid, three (90 participants) of fluphenazine with a tricyclic antidepressant; three (90 participants) of an N-methyl-D-aspartate (NMDA) blocker with an agent from a different drug class; five (604 participants) of various topical medications; one (313 participants) of tramadol with acetaminophen; and another one (44 participants) of a cholecystokinin blocker (L-365,260) with morphine. The majority of combinations evaluated to date involve drugs, each of which share some element of central nervous system (CNS) depression (e.g. sedation, cognitive dysfunction). This aspect of side effect overlap between the combined agents was often reflected in similar or higher dropout rates for the combination and may thus substantially limit the utility of such drug combinations. Meta-analysis was possible for only one comparison of only one combination, i.e. gabapentin + opioid versus gabapentin alone. This meta-analysis involving 386 participants from two studies demonstrated modest, yet statistically significant, superiority of a gabapentin + opioid combination over gabapentin alone. However, this combination also produced significantly more frequent side effect-related trial dropouts compared to gabapentin alone.

AUTHORS' CONCLUSIONS

Multiple, good-quality studies demonstrate superior efficacy of two-drug combinations. However, the number of available studies for any one specific combination, as well as other study factors (e.g. limited trial size and duration), preclude the recommendation of any one specific drug combination for neuropathic pain. Demonstration of combination benefits by several studies together with reports of widespread clinical polypharmacy for neuropathic pain surely provide a rationale for additional future rigorous evaluations. In order to properly identify specific drug combinations which provide superior efficacy and/or safety, we recommend that future neuropathic pain studies of two-drug combinations include comparisons with placebo and both single-agent components. Given the apparent adverse impact of combining agents with similar adverse effect profiles (e.g. CNS depression), the anticipated development and availability of non-sedating neuropathic pain agents could lead to the identification of more favourable analgesic drug combinations in which side effects are not compounded.

Management of Severe Neuropathic Cancer Pain

Neuropathic cancer pain is common, very disabling and difficult to treat. It can be related to tumor invasion of neural structures and neuronal damage by surgery, chemotherapy and radiation therapy. Adjuvant analgesics are often used with opioids to control neuropathic pain in cancer patients. Methadone, a synthetic opioid with multiple mechanisms of action, is gaining increasing importance as an effective agent in the treatment of cancer related neuropathic pain. This case illustrates the challenges of managing severe pain in a patient with head and neck cancer while undergoing anti-tumor treatment. A review of the adjuvant analgesics and opioids, particularly methadone, in the management of neuropathic pain is also included.

Prostate cancer pain management: EAU guidelines on pain management

CONTEXT

The first publication of the European Association of Urology (EAU) guidelines on Pain Management in Urology dates back to 2003. Since then, these guidelines have been revised several times with the most recent update achieved in 2010.

OBJECTIVE

Given the scope of the full text guidelines, condensing the entire document was no option in this context. This paper presents a summary of the section of pain management in prostate cancer, a topic considered of direct relevance for the practicing urologist.

EVIDENCE ACQUISITION

A multidisciplinary expert panel (urologists, anaesthesiologists, radio-oncologists) compiled this document based on a comprehensive consultation of the literature. Data were identified through a structured search, covering the time frame 2000 through 2010, using Medline and Embase as well as the Cochrane Library of systematic reviews. The scientific papers were weighed by the expert panel and a level of evidence (LE) assigned. Recommendations have been graded as a means to provide transparency between the underlying evidence and the guidance provided. Pain can occur in each stage of prostate cancer. It could be caused by the cancer itself (77%), be related to the cancer treatment (19%) or be unrelated to either (3%). The incidence of pain rises to 90% as patients enter the terminal phase of their illness. The physician's task is to discover and treat the cause of pain and the pain itself, to determine whether or not the underlying cause is treatable, to provide pain relief and palliative care. These tasks more often than not require a multidisciplinary team. Pain management involves mainly pharmacotherapy, including direct anticancer therapy such as androgen deprivation and chemotherapy, as well as analgetics, for instance non-steroidal anti-inflammatory drugs (NSAIDs) or opioids. In case of local impairment due to the cancer or its metastases, primary treatments like surgery, radiotherapy or radionuclides can provide adequate pain relief. In addition, in palliative care, functional, psychosocial and spiritual support are essential components. The EAU guidelines on Pain Management in Urology are available in a number of different formats through the EAU Central Office and the EAU website ( http://www.uroweb.org/guidelines/online-guidelines/ ).

CONCLUSION

The mainstay of pain management in prostate cancer is involvement of and collaboration between experts from a number of disciplines to be able to achieve a complete pain evaluation and to offer the full range of treatment options. Prostate cancer-related pain can, in most cases, be managed effectively, but it requires careful monitoring where a balance should be found between pain relief and potential side effects of treatment and quality of life (QoL).

Transformation of acute cancer pain to chronic cancer pain syndromes

For many cancer survivors, disease-related long-term morbidities and the application of advanced cancer treatments have resulted in the development of a chronic pain state. This brief review explores the relationship between what is known about the treatment of active cancer pain syndromes-both continuous pain and breakthrough pain-and persisting pain syndromes in cancer survivors. We also posit that because there is evidence to suggest that poorly treated acute pain can lead to protracted pain conditions, acute pain should be recognized and treated promptly, both for short- and long-term gain. In the short term, better acute pain treatment can improve functionality and psychological well-being, whereas in the long term, mounting evidence suggests that it could prevent of future chronic pain.

Preliminary assessment of a neuropathic pain treatment and referral algorithm for patients with cancer

CONTEXT

The purpose of this case series study was to pilot test an evidence-based neuropathic pain (NP) treatment and referral algorithm for use by oncology nurses when managing cancer-related NP.

OBJECTIVES

The primary study objective was to assess patient-reported outcomes (pain severity, changes in activities of daily living, and satisfaction) resulting from algorithm use.

METHODS

Outpatients (n=20) with cancer-related NP scores ≥4 on a 0-10 numeric rating scale participated in the study. NP assessment, treatment, and referral to ancillary providers were guided by an evidence-based NP algorithm that was implemented by oncology nurse practitioners. Based on efficacy evidenced through randomized clinical trials published at the time of study implementation, the following drugs were included in the algorithm: lidocaine patch, gabapentin, oxycodone, tramadol, morphine, methadone, duloxetine, pregabalin, and nortriptyline. Recommendations for starting dose, dose escalation, drug combinations, treatment duration, and contraindications were included for first-tier drugs. Patient-reported outcomes (pain severity, functional capacity, and satisfaction) were assessed monthly over 12 weeks.

RESULTS

Average NP severity (P=0.001), general activity (P<0.001), mood (P=0.002), walking ability (P=0.01), ability to perform normal work (P=0.002), relationships (P=0.002), sleep (P=0.01), life enjoyment (P<0.001), and patient satisfaction (P=0.003) all improved by 12 weeks.

CONCLUSION

Evidence from this pilot study suggests that NP evidence-based treatment may result in improved symptoms, function, and patient satisfaction. A randomized controlled trial is needed to further assess algorithm efficacy.

Anti-epileptic drugs

Therapeutic Reviews aim to provide essential independent information for health professionals about drugs used in palliative and hospice care. Additional content is available on www.palliativedrugs.com. Country-specific books (Hospice and Palliative Care Formulary USA, and Palliative Care Formulary, British and Canadian editions) are also available and can be ordered from www.palliativedrugs.com. The series editors welcome feedback on the articles (hq@palliativedrugs.com).

Pharmacological treatment of neuropathic cancer pain: a comprehensive review of the current literature

Neuropathic cancer pain (NCP), commonly encountered in clinical practice, may be cancer-related, namely resulting from nervous system tumor invasion, surgical nerve damage during tumor removal, radiation-induced nerve damage and chemotherapy-related neuropathy, or may be of benign origin, unrelated to cancer. A neuropathic component is evident in about 1/3 of cancer pain cases. Although from a pathophysiological perspective NCP may differ from chronic neuropathic pain (NP), such as noncancer-related pain, clinical practice, and limited publications have shown that these two pain entities may share some treatment modalities. For example, co-analgesics have been well integrated into cancer pain-management strategies and are often used as First-Line options for the treatment of NCP. These drugs, including antidepressants and anticonvulsants, are recommended by evidence-based guidelines, whereas, others such as lidocaine patch 5%, are supported by randomized, controlled, clinical data and are included in guidelines for restricted conditions treatment. The vast majority of these drugs have already been proven useful in the management of benign NP syndromes. Treatment decisions for patients with NP can be difficult. The intrinsic difficulties in performing randomized controlled trials in cancer pain have traditionally justified the acceptance of drugs already known to be effective in benign NP for the management of malignant NP, despite the lack of relevant high quality data. Interest in NCP mechanisms and pharmacotherapy has increased, resulting in significant mechanism-based treatment advances for the future. In this comprehensive review, we present the latest knowledge regarding NCP pharmacological management.

Effectiveness of antiepileptic or antidepressant drugs when added to opioids for cancer pain: systematic review

Neuropathic pain mechanisms are present in up to 40% of patients with cancer pain. In these situations, additional or adjuvant analgesic drugs (such as antidepressants or antiepileptics) are often required to optimize pain control alongside standard opioid therapy. This systematic review aimed to determine the effectiveness of antidepressants and antiepileptics when added to opioids, compared to opioids alone, for the management of pain caused directly by cancer. Prospective clinical studies, published in English that used a before-after design or randomized or non-randomized group comparisons were identified. Data were extracted on pain intensity, pain relief and adverse events. Eight studies were eligible (five randomized controlled trials) that recruited 465 patients in total, of whom 370 (79.5%) completed the study period. A narrative analysis was performed because clinical and methodological heterogeneity prevented meta-analysis. Included studies suggested that adjuvants improve pain control within 4-8 days when added to opioids for cancer pain; the strongest evidence supports gabapentin. However, a reduction in pain intensity of greater than 1 point on a 0-10 numerical rating scale is unlikely, but an increase in adverse events is likely. For all adjuvants, the effect size was much less than that seen in patients with non-cancer neuropathic pain. Dosing strategies that can be examined in future clinical trials are suggested.

Gabapentin for chronic neuropathic pain and fibromyalgia in adults

BACKGROUND

This review updates parts of two earlier Cochrane reviews investigating effects of gabapentin in chronic neuropathic pain (pain due to nerve damage). Antiepileptic drugs are used to manage pain, predominantly for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for chronic neuropathic pain management.

SEARCH STRATEGY

We identified randomised trials of gabapentin in acute, chronic or cancer pain from MEDLINE, EMBASE, and CENTRAL. We obtained clinical trial reports and synopses of published and unpublished studies from Internet sources. The date of the most recent search was January 2011.

SELECTION CRITERIA

Randomised, double-blind studies reporting the analgesic and adverse effects of gabapentin in neuropathic pain with assessment of pain intensity and/or pain relief, using validated scales. Participants were adults aged 18 and over.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We calculated numbers needed to treat to benefit (NNTs), concentrating on IMMPACT (Initiative on Methods, Measurement and Pain Assessment in Clinical Trials) definitions of at least moderate and substantial benefit, and to harm (NNH) for adverse effects and withdrawal. Meta-analysis was undertaken using a fixed-effect model.

MAIN RESULTS

Twenty-nine studies (3571 participants), studied gabapentin at daily doses of 1200 mg or more in 12 chronic pain conditions; 78% of participants were in studies of postherpetic neuralgia, painful diabetic neuropathy or mixed neuropathic pain. Using the IMMPACT definition of at least moderate benefit, gabapentin was superior to placebo in 14 studies with 2831 participants, 43% improving with gabapentin and 26% with placebo; the NNT was 5.8 (4.8 to 7.2). Using the IMMPACT definition of substantial benefit, gabapentin was superior to placebo in 13 studies with 2627 participants, 31% improving with gabapentin and 17% with placebo; the NNT was 6.8 (5.6 to 8.7). These estimates of efficacy are more conservative than those reported in a previous review. Data from few studies and participants were available for other painful conditions.Adverse events occurred significantly more often with gabapentin. Persons taking gabapentin can expect to have at least one adverse event (66%), withdraw because of an adverse event (12%), suffer dizziness (21%), somnolence (16%), peripheral oedema (8%), and gait disturbance (9%). Serious adverse events (4%) were no more common than with placebo.There were insufficient data for comparisons with other active treatments.

AUTHORS' CONCLUSIONS

Gabapentin provides pain relief of a high level in about a third of people who take if for painful neuropathic pain. Adverse events are frequent, but mostly tolerable. More conservative estimates of efficacy resulted from using better definitions of efficacy outcome at higher, clinically important, levels, combined with a considerable increase in the numbers of studies and participants available for analysis.

WITHDRAWN: Gabapentin for acute and chronic pain

BACKGROUND

February 2009: The authors are aware of unpublished trial data for Gabapentin which could affect the results of this review. This information together with that from trials published since 2005, will be considered when this review is updated in 2009.Anticonvulsant drugs have been used in the management of pain since the 1960s. The clinical impression is that they are useful for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for pain management in clinical practice.

SEARCH STRATEGY

Randomised trials of gabapentin in acute, chronic or cancer pain were identified by MEDLINE (1966 to Nov 2004), EMBASE (1994 to Nov 2004), SIGLE (1980 to Jan 2004) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004). Additional studies were identified from the reference list of the retrieved papers, and by contacting investigators. Date of most recent search: January 2004.

SELECTION CRITERIA

Randomised trials reporting the analgesic effects of gabapentin in participants with subjective pain assessment as either the primary or a secondary outcome.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent review authors, and trials were quality scored. Numbers-needed-to-treat-to-benefit (NNTs) were calculated, where possible, from dichotomous data for effectiveness, adverse effects and drug-related study withdrawal.

MAIN RESULTS

Fourteen reports describing 15 studies of gabapentin were considered eligible (1468 participants). One was a study of acute pain. The remainder included the following conditions: post-herpetic neuralgia (two studies), diabetic neuropathy (seven studies), a cancer related neuropathic pain (one study) phantom limb pain (one study), Guillain Barré syndrome (one study), spinal chord injury pain (one study) and various neuropathic pains (one study).The study in acute post-operative pain (70 participants) showed no benefit for gabapentin compared to placebo for pain at rest.In chronic pain, the NNT for improvement in all trials with evaluable data is 4.3 (95% CI 3.5 to 5.7). Forty two percent of participants improved on gabapentin compared to 19% on placebo. The number needed to harm (NNH) for adverse events leading to withdrawal from a trial was not significant. Fourteen percent of participants withdrew from active arms compared to 10% in placebo arms. The NNH for minor harm was 3.7 (95% CI 2.4 to 5.4). The NNT for effective pain relief in diabetic neuropathy was 2.9 (95% CI 2.2 to 4.3) and for post herpetic neuralgia 3.9 (95% CI 3 to 5.7).

AUTHORS' CONCLUSIONS

There is evidence to show that gabapentin is effective in neuropathic pain. There is limited evidence to show that gabapentin is ineffective in acute pain.

Management of cancer pain

In the last decades, studies validating the WHO analgesic ladder have been shown to have methodological limitations and different problems are unresolved due to a lack of controlled studies on this subject. These problems include a better definition of the role of NSAIDs, the prolonged use of NSAIDs in cancer pain, and the utility of step 2. Moreover, the indications for using different strong opioids and alternate routes of administration to improve pain relief in difficult pain situations are not well established. The proportion of patients who do not benefit from these treatments remain unclear, and how the opioid response may be improved with the use of adjuvants is also uncertain. This review will offer an update on these problems and the existing therapeutic opportunities.

Treatment of pain in children after limb-sparing surgery: an institution's 26-year experience

A significant proportion of patients report long-term pain that is ≥5 on a 0-10 intensity scale after limb-sparing surgery for malignancies of the long bones. Patients experience several distinct types of pain after limb-sparing surgery which constitute a complex clinical entity. This retrospective study examined 26 years of experience in a pediatric institution (1981-2007) in pain management as long as 6 months after limb-sparing surgery and reviewed the historical evolution of pain interventions. One hundred fifty patients underwent 151 limb-salvage surgeries for bone cancer of the extremities in this series. Pain treatment increased progressively in complexity. Therapies included opioids, nonsteroidal antiinflammatory drugs, acetaminophen-opioid combinations, postoperative continuous epidural infusion, anticonvulsants and tricyclic antidepressants for neuropathic pain, local anesthetic wound catheters, and continuous peripheral nerve block catheters. Management of pain after limb-sparing surgery has evolved over the 26 years of this review. It currently relies on multiple "layers" of pharmacologic and nonpharmacologic strategies to address the complex mixed nociceptive and neuropathic mechanisms of pain in this patient population.

alpha(2)delta Modulators for Management of Compression Neuropathic Pain: A Review of Three Case Series

CONTEXT

The alpha(2)delta modulators gabapentin and pregabalin are effective against neuropathic pain. Numerous brands of alpha(2)delta modulators are available in India, and are expected to have equivalent clinical effects. They are routinely used for management of neuropathic pain associated with radiculopathy.

AIM

To describe clinical outcomes in three series of cases of neuropathic pain treated with three available brands of alpha(2)delta modulators.

SETTINGS AND DESIGN

Retrospective analysis of clinical outcomes in patients attending an interventional pain clinic

PATIENTS AND METHODS

One hundred and ninety-four consecutive patients with neuropathic pain secondary to Magnetic Resonance Imaging (MRI)-documented compression radiculopathy received either LYRICA (LYR), a locally available generic brand of pregabalin (PGN), or a locally available generic brand of gabapentin (GBN), respectively. Drug treatment was continued till adequate pain relief was achieved. In each of the three groups, mean pain scores were analyzed at Days 0, 15, 60 and 90, and daytime sedation scores at Days 1, 15, 60 and 90.

STATISTICAL ANALYSIS USED

Analysis of variance (ANOVA) followed by pair-wise comparison using two-tailed unpaired t-test (if P value was significant).

RESULTS

Mean pain score was significantly lower in the LYR series as compared to the PGN and GBN series at Days 15, 60 and 90. As compared to the PGN and GBN series, a greater proportion of patients in the LYR series could discontinue drug therapy following adequate pain relief, by Day 90. Daytime sedation scores were significantly lower in the LYR series as compared to the PGN and GBN series at Days 1, 15 and 60, and as compared to the PGN series at Day 90.

CONCLUSION

These results indicate the effectiveness of alpha(2)delta modulators for management of neuropathic pain secondary to compression radiculopathy. The results also suggest a possible therapeutic superiority of LYRICA over locally available generic brands of pregabalin and gabapentin. These findings need to be further examined in randomized, controlled trials.

A prospective open-label trial of gabapentin as an adjuvant analgesic with opioids for Japanese patients with neuropathic cancer pain

BACKGROUND

Neuropathic pain is regarded as one of the main causes of cancer pain refractory to standard opioid therapy in palliative care. The use of adjuvant analgesics for neuropathic cancer pain is largely empirical and the true efficacy of these adjuvant analgesics has been unknown. Gabapentin is one of the new promising anticonvulsant drugs as an adjuvant analgesic for neuropathic cancer pain.

METHODS

The clinical usefulness of gabapentin in combination with opioids for Japanese patients with neuropathic cancer pain was assessed in an open-label, single-center, prospective study. Gabapentin was initiated in addition to the drugs currently being administered. The dose of gabapentin was titrated from 200 mg to a maximum dose of 2400 mg per day over 15 days, based on discussion with each patient. The primary endpoint variable was the numerical rating scale (NRS) of 0-10 measured using the brief pain inventory.

RESULTS

From February 2007 to December 2007, gabapentin was administered to 24 patients that were already receiving an opioid without sufficient analgesia. Administration of gabapentin statistically reduced the worst-NRS, the least-NRS, and the average-NRS (7.3 --> 5.8, 3.6 --> 3.0, 5.8 --> 4.5, respectively). Four patients (16.7%) were withdrawn from the study because of adverse events (headache, myoclonus, heartburn, bronchial asthma).

CONCLUSION

Although gabapentin might be regarded as a promising new adjuvant analgesic for neuropathic cancer pain, our results indicated that the decrease in pain score was of minimal clinical benefit. Controlled trials with other adjuvant analgesics are needed.

Cancer pain: part 2: physical, interventional and complimentary therapies; management in the community; acute, treatment-related and complex cancer pain: a perspective from the British Pain Society endorsed by the UK Association of Palliative Medicine and the Royal College of General Practitioners

OBJECTIVE

This discussion document about the management of cancer pain is written from the pain specialists' perspective in order to provoke thought and interest in a multimodal approach to the management of cancer pain, not just towards the end of life, but pain at diagnosis, as a consequence of cancer therapies, and in cancer survivors. It relates the science of pain to the clinical setting and explains the role of psychological, physical, interventional and complementary therapies in cancer pain.

METHODS

This document has been produced by a consensus group of relevant healthcare professionals in the United Kingdom and patients' representatives making reference to the current body of evidence relating to cancer pain. In the second of two parts, physical, invasive and complementary cancer pain therapies; treatment in the community; acute, treatment-related and complex cancer pain are considered.

CONCLUSIONS

It is recognized that the World Health Organization (WHO) analgesic ladder, whilst providing relief of cancer pain towards the end of life for many sufferers world-wide, may have limitations in the context of longer survival and increasing disease complexity. To complement this, it is suggested that a more comprehensive model of managing cancer pain is needed that is mechanism-based and multimodal, using combination therapies including interventions where appropriate, tailored to the needs of an individual, with the aim to optimize pain relief with minimization of adverse effects.

Gabapentin toxicity in patients with chronic kidney disease: a preventable cause of morbidity

BACKGROUND

Gabapentin is frequently used as an analgesic in patients with chronic kidney disease. Although gabapentin is well known for its favorable pharmacokinetics, it is exclusively eliminated renally, and patients with chronic kidney disease are at risk for toxicity. Existing literature on such risk is lacking.

METHODS

We examined the Mayo Clinic Rochester database from 1998 to 2007 in patients with serum gabapentin measurements and known medical outcomes. A total of 729 patients were stratified according to their estimated glomerular filtration rate: group I, 126 individuals with estimated glomerular filtration greater than 90 mL/min/1.72 mm(2) [corrected] ; group II, 594 individuals with estimated glomerular filtration less than 90 mL/min/1.72 mm(2) [corrected] without dialysis; group III, 9 individuals with chronic dialysis.

RESULTS

Patients in groups II and III had higher serum gabapentin levels (8.39+/-0.32 microL/mL and 58.8+/-10.22 microL/mL, respectively) than in group I (5.52+/-0.32 microL/mL, P<.01). Toxicity occurred exclusively in groups II (5.56%) and III (77.8%); toxic manifestations were more severe in group III than in group II. Elderly individuals with multiple comorbidities were overrepresented in those with toxic manifestations. Gabapentin toxicity was suspected initially in only 41.5% of symptomatic cases.

CONCLUSION

Gabapentin toxicity in patients with chronic kidney disease is underrecognized. Patients with chronic kidney disease often receive inappropriately high gabapentin dosage for their kidney function, occasioning overt toxicity; advanced age and comorbidity predispose these patients for toxicity. Heightened awareness of such preventable risk, amid the chronic kidney disease epidemic, would be cost-effective and improve healthcare quality.

Use of lidocaine patches for neuropathic pain in a comprehensive cancer centre

BACKGROUND

There are few reports of the use of the lidocaine 5% patch (L5%P) for neuropathic pain (NP) in the cancer patient. Within a comprehensive cancer centre, L5%P has been prescribed by the Pain and Palliative Care Service (Peter McCallum Cancer Centre, East Melbourne, Victoria, Australia) for selected patients with NP since 2001.

OBJECTIVE

To retrospectively audit the use of L5%P within a comprehensive cancer centre.

METHODS

All L5%P prescriptions up to January 2009 were listed and patient medical records were searched to determine neuropathic pain syndromes treated, the presence of allodynia, previous analgesic medications, treatment duration and outcome.

RESULTS

L5%P was prescribed for 97 patients, most frequently for persistent postsurgical NP (n=26), postherpetic neuralgia (n=24) and cancer-related NP (n=18). Six patients had no history of cancer and two patients never applied L5%P. Reviewers classed L5%P analgesic efficacy as 'potent' in 38% of patients with postherpetic neuralgia, 35% of patients with postsurgical pain, 27% of patients with NP after other treatments for cancer and 12% of patients with NP attributed to cancer alone. Allodynia featured in at least 60% of patients. Where allodynia was present, the efficacy of L5%P was assessed as 'potent' in 38% and 'partial' in 24%, but 'ineffective' in 26%, and 'causing worse pain' in 3.4% of patients. Treatment duration extended longer than one month in 52 patients, longer than two months in 29 patients and longer than one year in 13 patients. Therapy was ceased due to skin irritation in seven patients. The outcomes in relation to other reports are discussed.

CONCLUSION

The present data support trials of L5%P for cancer patients with NP syndromes associated with allodynia.

Outcome reporting in industry-sponsored trials of gabapentin for off-label use

BACKGROUND

There is good evidence of selective outcome reporting in published reports of randomized trials.

METHODS

We examined reporting practices for trials of gabapentin funded by Pfizer and Warner-Lambert's subsidiary, Parke-Davis (hereafter referred to as Pfizer and Parke-Davis) for off-label indications (prophylaxis against migraine and treatment of bipolar disorders, neuropathic pain, and nociceptive pain), comparing internal company documents with published reports.

RESULTS

We identified 20 clinical trials for which internal documents were available from Pfizer and Parke-Davis; of these trials, 12 were reported in publications. For 8 of the 12 reported trials, the primary outcome defined in the published report differed from that described in the protocol. Sources of disagreement included the introduction of a new primary outcome (in the case of 6 trials), failure to distinguish between primary and secondary outcomes (2 trials), relegation of primary outcomes to secondary outcomes (2 trials), and failure to report one or more protocol-defined primary outcomes (5 trials). Trials that presented findings that were not significant (P > or = 0.05) for the protocol-defined primary outcome in the internal documents either were not reported in full or were reported with a changed primary outcome. The primary outcome was changed in the case of 5 of 8 published trials for which statistically significant differences favoring gabapentin were reported. Of the 21 primary outcomes described in the protocols of the published trials, 6 were not reported at all and 4 were reported as secondary outcomes. Of 28 primary outcomes described in the published reports, 12 were newly introduced.

CONCLUSIONS

We identified selective outcome reporting for trials of off-label use of gabapentin. This practice threatens the validity of evidence for the effectiveness of off-label interventions.

How effective are patient-based educational interventions in the management of cancer pain? Systematic review and meta-analysis

This review aimed to quantify the benefit of patient-based educational interventions in the management of cancer pain. We undertook a systematic review and meta-analysis of experimentally randomised and non-randomised controlled clinical trials identified from six databases from inception to November 2007.Two reviewers independently selected trials comparing intervention (formal instruction on cancer pain and analgesia on an individual basis using any medium) to usual care or other control in adults with cancer pain. Methodological quality was assessed, and data extraction undertaken by one reviewer with a second reviewer checking for accuracy. We used random effects model to combine the effect estimates from studies. Main outcome measures were effects on knowledge and attitudes towards cancer pain and analgesia, and pain intensity. Twenty-one trials (19 randomised) totalling 3501 patients met inclusion criteria, and 15 were included in the meta-analysis. Compared to usual care or control, educational interventions improved knowledge and attitudes by half a point on 0-5 rating scale (weighted mean difference 0.52, 95% confidence interval 0.04-1.0), reduced average pain intensity by over one point on 0-10 rating scale (WMD -1.1, -1.8 to -0.41) and reduced worst pain intensity by just under one point (WMD -0.78, -1.21 to -0.35). We found equivocal evidence for the effect of education on self-efficacy, but no significant benefit on medication adherence or on reducing interference with daily activities. Patient-based educational interventions can result in modest but significant benefits in the management of cancer pain, and are probably underused alongside more traditional analgesic approaches.

Management of chronic pain in cancer survivors

Chronic pain is a frequent complication of cancer and its treatments and is often underreported, underdiagnosed, and undertreated. Pain in cancer survivors is caused by residual tissue damage from the cancer and/or the cancer therapy. This pain can be divided into 3 pathophysiologic categories: somatic, visceral, and neuropathic. The most common treatment-induced chronic pain syndromes are neuropathies secondary to surgery, radiation therapy, and chemotherapy. Comfort and function are optimized in cancer survivors by a multidisciplinary approach using an individually tailored combination of opioids, coanalgesics, physical therapy, interventional procedures, psychosocial interventions, and complementary and alternative modalities. Management of chronic pain must be integrated into comprehensive cancer care so that cancer patients can fully enjoy their survival.

Systematic review of the effectiveness of botulinum toxin or radiotherapy for sialorrhea in patients with amyotrophic lateral sclerosis

Fifty percent of patients with amyotrophic lateral sclerosis (ALS) experience problems handling serous saliva and 20% fail to achieve adequate control of sialorrhea with anticholinergic medications, or experience intolerable adverse effects from these drugs. Both botulinum and radiotherapy have been suggested in the literature as treatments for intractable sialorrhea. In this review, we assess the evidence for the effectiveness and toxicity of botulinum toxin and radiotherapy for sialorrhea in patients with ALS. Relevant studies were retrieved from Medline, Embase and Cochrane Databases. Handsearching of Neurology, Journal of Pain and Symptom Management, and Palliative Medicine and of reference lists, was carried out. Five studies (28 patients) were included in the analysis of botulinum. Of the four studies using an intraglandular method of injection, no adverse effects occurred. Two of these had positive findings of the effect of botulinum in salivary secretion rate and quality of life. In contrast, significant adverse effects were experienced by two patients in a study of retrograde injections into the salivary ducts. Two studies were included in the analysis of radiotherapy (27 patients). Both demonstrated a positive effect of radiotherapy on salivary secretion rate. Some patients experienced mild acute side effects. Because of the small numbers of studies, small sample sizes, and poor quality of reporting, it is not possible to draw firm conclusions. There is some evidence indicating that both botulinum and radiotherapy are well tolerated, effective treatments for persistent sialorrhea in patients with ALS and that the duration of action is up to three months with botulinum and six months with radiotherapy.

Pain therapy

Cancer-related pain is a major issue of healthcare systems worldwide. The reported incidence, considering all stages of the disease, is 51%, which can increase to 74% in the advanced and terminal stages. For advanced cancer, pain is moderate to severe in about 40-50% and very severe or excruciating in 25-30% of cases. Pain is both a sensation and an emotional experience. Pain is always subjective; and may be affected by emotional, social and spiritual components thus it has been defined as "total pain". From a pathophysiological point of view, pain can be classified as nociceptive (somatic and visceral), neuropathic (central, peripheral, sympathetic) idiopathic or psychogenic. A proper pain assessment is fundamental for an effective and individualised treatment. In 1986 the World Health Organisation (WHO) published analgesic guidelines for the treatment of cancer pain based on a three-step ladder and practical recommendations. These guidelines serve as an algorithm for a sequential pharmacological approach to treatment according to the intensity of pain as reported by the patient. The WHO analgesic ladder remains the clinical model for pain therapy. Its clinical application should be employed only after a complete and comprehensive assessment and evaluation based on the needs of each patient. When applying the WHO guidelines, up to 90% of patients can find relief regardless of the settings of care, social and/or cultural environment. This is the standard treatment on a type C basis. Only when such an approach is ineffective are interventions such as spinal administration of opioid analgesics or neuroinvasive procedures recommended.

Therapy of chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is still a common and disabling side effect of many chemotherapy agents in use today. Unfortunately, neither prophylactic strategies nor symptomatic treatments have proven useful yet. This review will discuss the diagnosis and evaluation of neuropathy in cancer patients, as well as reviewing the various prophylactic and symptomatic treatments that have been proposed or tried. However, sufficient evidence is lacking to recommend any of these treatments to patients suffering with CIPN. Therefore, the best approach is to treat symptomatically, and to start with broad-spectrum analgesic medications such as non-steroidal anti-inflammatory drugs (NSAIDs). If NSAIDs fail, a reasonable second-line agent in properly selected patients may be an opioid. Unfortunately, even when effective in other types of neuropathic pain, anti-depressants and anticonvulsants have not yet proven effective for treating the symptoms of CIPN.

Experimental studies of potential analgesics for the treatment of chemotherapy-evoked painful peripheral neuropathies

OBJECTIVE

We investigated potential analgesics for chemotherapy-evoked neuropathic pain using rats treated with paclitaxel.

DESIGN

Drugs were tested in a repeated dosing paradigm (four daily injections). Topiramate was tested with a long-term treatment paradigm (12 days). A literature search was performed to summarize prior data.

MEASURES

Mechanical stimulation of the hind paw was used to assay antiallodynic and antihyperalgesic effects acutely and 24 hours after injection.

RESULTS

Amitriptyline produced significant analgesia, but this was not apparent until after the second injection. Baclofen produced significant effects, but the response varied erratically. Mexiletine and NMED-126 (a mixed N- and T-type calcium channel blocker) produced consistent, significant analgesia when tested acutely, but the pain relief did not persist at 24 hours postinjection. Oxcarbazepine had no effect at any time. Tramadol produced consistent, near-complete analgesia when tested acutely, but the analgesia did not persist to 24 hours postinjection. Topiramate produced significant effects that were first evident after 6-8 days of dosing.

CONCLUSIONS

The present data and data from the literature review suggest that there are several potential treatments for chemotherapy-evoked neuropathic pain. Nonsteroidal anti-inflammatory drugs have little or no efficacy. Opioids have an effect, but probably only with high doses. At least some antidepressants are analgesic in these conditions. Some, but clearly not all, anticonvulsants and sodium channel blockers have efficacy. Tramadol is a particularly promising candidate. Topiramate, acetyl-L-carnitine, carbamazepine, and venlafaxine may have protective or restorative effects. Clinical trials of these candidates are needed to advance the treatment of chemotherapy-evoked pain.