Opioid poorly-responsive cancer pain. Part 1: clinical considerations

An overview of the current drug treatment strategies for moderate to severe, chronic malignant tumor-related pain

INTRODUCTION

The pharmacological management of cancer pain is a complex issue that requires knowledge and experience in the use of analgesics. The aim of this expert review is to provide a panorama of the pharmacological strategies in cancer pain management.

AREAS COVERED

Opioid dose titration is a delicate process regarding the start of opioid treatment in different clinical conditions. How to improve the opioid response is a fundamental step, which includes different strategies when an initial treatment with opioids fails. The use of adjuvants is another relevant issue that should be considered in some specific circumstances to optimize the management of cancer pain management. Some clinical conditions, such as neuropathic pain and breakthrough pain, deserve a special attention. Relevant literature was selected to provide an overview of cancer pain management strategies.

EXPERT OPINION

Opioid therapy still remains the cornerstone of pharmacological management of cancer pain. Opioids should be used according to the level of tolerance, also personalizing the treatment (route, drug, and dosing). Adjuvant drugs may help in specific conditions, although their use should be balanced with the adverse effects. Breakthrough pain requires expertise in tailoring a treatment according to patient's profile and characteristics of episodes.

Methadone prescribed as an analgesic by a specialist palliative medicine team in an acute hospital inpatient setting: retrospective study

Emerging evidence suggests that methadone has a specific role in the management of treatment resistant cancer-related pain.

OBJECTIVES

To investigate the utilisation pattern, safety and efficacy of methadone prescribed as an analgesic for the management of complex cancer-related pain in an acute hospital inpatient setting.

METHODS

A retrospective longitudinal observational study of patients prescribed methadone as an analgesic between April 2020 and July 2021 was performed.Changes in coprescribed baseline opioid, use of breakthrough opioid analgesic, patient rated pain scores and adverse side effects were analysed.

RESULTS

16 patients with complex cancer-related treatment resistant pain who were prescribed methadone were included in the study. Of the 16 patients, 14 patients had metastatic disease. Pain was classified in 14 patients as mixed nociceptive-neuropathic and in 2 patients as neuropathic. 13 patients were coprescribed methadone with a pre-established opioid. Methadone was associated with a statistically significant decrease in both opioid breakthrough analgesic by 61%±28% (p<0.001), and coprescribed opioid by 17%±12% (p=0.015). Patient rated pain scores were also significantly decreased (p<0.001).

CONCLUSION

Methadone appears to have a specific role in the management of complex cancer pain, neuropathic pain, opioid-tolerance and opioid-induced hyperalgesia, which may be attributable to N-methyl-D-aspartate receptor antagonism.

Switching to Intravenous Methadone in Advanced Cancer Patients: A Retrospective Analysis

CONTEXT

Information about opioid switching to intravenous methadone is lacking.

OBJECTIVES

The aim of this study was to assess the outcome of opioid switching to intravenous methadone (IV-ME) in patients admitted to an acute supportive/palliative care unit (ASPCU). The secondary outcome was to assess the conversion ratio from IV-ME to oral methadone at time of hospital discharge.

METHODS

We retrieved from the pharmacy registry the list of patients who were prescribed IV-ME during their ASPCU admission for a period of 47 months. Poor analgesia with previous opioids and/or adverse effects were the main indications for opioid switching. IV-ME was titrated until acceptable analgesia was achieved. The effective dose was multiplied by three to establish the intravenous daily dose, given as a continuous infusion. Doses were then changed according to the clinical needs. Once the patient was stabilized, IV-ME dose was converted to oral methadone, by using an initial ratio of 1:1.2. Further dose changes were made according to clinical needs until stabilization, before patients' discharge. Information about patients' characteristics, pain scores on the Edmonton Symptom Assessment Scale (ESAS), Memorial Delirium Assessment Scale (MDAS), Cut-down, Annoyed, Guilty, Eye-opener (CAGE) questionnaire, previous opioids and their doses, expressed as oral morphine equivalents (OME), were recorded. The effective bolus of IV-ME, initial daily infusion rate, and oral methadone doses were assessed, and conversion ratios calculated.

RESULTS

Forty-one patients were taken into consideration for the study. The mean effective bolus of IV-ME titrated for achieving acceptable analgesia was 9 mg (range 5-15 mg). The mean daily continuous infusion rate of IV-ME was 27.6 mg/day (SD 21). The mean daily dose of oral methadone at time of discharge was 46.8 mg/day (SD 43). Discharge occurred within a median of seven days (range 6-9) after admission. Previous opioid (OME)/IV-ME, oral-IV-ME, and previous opioid (OME)/oral methadone were 6.25, 1.7, and 3.7, respectively.

CONCLUSION

IV-ME dose titration followed by intravenous infusion allowed a rapid pain control in few minutes in patients with severe pain intensity, not responsive to previous opioids. Conversion to oral route was successful and facilitated home discharge. Further studies should be performed to confirm these preliminary results.

Improvement in patient-reported pain among patients with metastatic cancer and its association with opioid prescribing

PURPOSE

Opioids are a mainstay of cancer pain management; however, patients with metastatic cancer are often excluded from studies, leading to a lack of evidence on whether increased prescribing (dosage and/or duration) results in improved outcomes for this population. This study aimed to investigate whether increased opioid prescribing is associated with an improvement in patient-reported pain among patients with metastatic cancer.

PATIENTS AND METHODS

A retrospective cohort of all adult patients diagnosed with stage IV cancers, who completed at least two patient-reported outcomes (PROs) within 30 days of each other, was identified from administrative data. Opioid prescriptions were categorized by dosage level and number of prescription days. Multivariable logistic regression was used to investigate the association between opioid prescribing and clinically important improvement in pain score (≥ 1 point change on the Edmonton Symptom Assessment System).

RESULTS

A total of 2169 patients were included, 770 (35.5%) of whom had active opioid prescription between PROs, with an average daily dosage of 86.1 mg of oral morphine equivalent. Active prescription was associated with improvement in pain (OR = 2.17, P < 0.001). However, among patients with active prescription, neither dosage nor number of prescription days was significantly associated with pain improvement.

CONCLUSION

Opioid prescription is important for treating cancer-related pain; however, increased dosage or duration may not be leading to greater improvements in pain. Patients with metastatic cancer who are receiving increased opioid prescribing may have difficult-to-treat pain and may benefit from multidisciplinary pain management strategies to supplement opioid prescription and improve outcomes.

Maddalena Opioid Switching Score in patients with cancer pain

ABSTRACT

Evaluation of opioid switching (OS) for cancer pain has not been properly assessed. The aim of this study was to assess an integrated score (Maddalena Opioid Switching Score) as a simple and repeatable tool to evaluate the outcomes of OS, facilitating the interpretation and comparison of studies, and information exchange among researchers. The integrated score took into account pain intensity, intensity of opioid-related symptoms, and cognitive function by using an author's formula. Physical and psychological symptoms were evaluated by the Edmonton Symptom Assessment Scale and Patient Global Impression (PGI) by the minimal clinically important difference. One hundred six patients were analyzed. Ninety-five patients were switched successfully, and 11 patients underwent a further OS and/or an alternative procedure. The Maddalena Opioid Switching Score significantly decreased after OS and was highly correlated to PGI of improvement ( P < 0.0005). In patients with unsuccessful OS, no significant changes in the Maddalena Opioid Switching Score and PGI were observed. A significant reduction in Edmonton Symptom Assessment Scale items intensity was observed after OS. The Maddalena Opioid Switching Score resulted to be a sensitive instrument for measuring the clinical improvement produced by OS.

Cancer Pain Treatment Strategies in Patients with Cancer

Management of cancer pain is challenging. Despite the poor evidence, opioid therapy still remains the cornerstone for the management of cancer-related pain. Opioids should be given according to the clinical presentation in the different stages of disease. There is no drug of choice, as most opioids are effective. Thus, the choice should be based on the individual characteristics of patients. Optimization of opioid therapy may allow individual treatment according to the patient's characteristics and pain syndromes, providing timely alternatives in the different stages of disease. While most patients respond to an appropriate treatment associated with a comprehensive assessment and symptom control, a high level of experience and knowledge is necessary in determining conditions to maximize the analgesic response, eventually adding adjuvants in some specific circumstances. Alternative opioids may improve the balance between analgesia and adverse effects in the presence of a poor response to the first opioid in a large number of patients. Finally, a selected population can benefit from some interventional procedures.

When the game is hard, more complex weapons are needed

OBJECTIVES

The aim of this paper is to illustrate how to manage a very difficult pain condition.

METHODS

This is a clinical note of a complex approach using multiple analgesic regimens to effectively afford challenging pain situations.

RESULTS

A man underwent an opioid dose titration, followed by dose stabilisation for some months. Then he underwent two opioid substitutions, unsuccessfully. A spinal analgesia provided good analgesia for a prolonged period of time, necessitating variable interventions to counteract the evolving, challenging clinical situation.

CONCLUSIONS

The description of this case illustrates the need of a high level of experience and knowledge to elaborate complex strategies step by step every time the pain syndrome was worsening. Recommendations are unlikely in these extreme circumstances, and treatment should be based on continuous clinical counteraction to the evolving clinical conditions.

Peripherally acting opioid analgesics and peripherally-induced analgesia

The management of pain, particularly chronic pain, is still an area of medical need. In this context, opioids remain a gold standard for the treatment of pain. However, significant side effects, mainly of central origin, limit their clinical use. Here, we review recent progress to improve the therapeutic and safety profiles of opioids for pain management. Characterization of peripheral opioid-mediated pain mechanisms have been a key component of this process. Several studies identified peripheral µ, δ, and κ opioid receptors (MOR, DOR, and KOR, respectively) and nociceptin/orphanin FQ (NOP) receptors as significant players of opioid-mediated antinociception, able to achieve clinically significant effects independently of any central action. Following this, particularly from a medicinal chemistry point of view, main efforts have been directed towards the peripheralization of opioid receptor agonists with the objective of optimizing receptor activity and minimizing central exposure and the associated undesired effects. These activities have allowed the characterization of a great variety of compounds and investigational drugs that show low central nervous system (CNS) penetration (and therefore a reduced side effect profile) yet maintaining the desired opioid-related peripheral antinociceptive activity. These include highly hydrophilic/amphiphilic and massive molecules unable to easily cross lipid membranes, substrates of glycoprotein P (a extrusion pump that avoids CNS penetration), nanocarriers that release the analgesic agent at the site of inflammation and pain, and pH-sensitive opioid agonists that selectively activate at those sites (and represent a new pharmacodynamic paradigm). Hopefully, patients with pain will benefit soon from the incorporation of these new entities.

Upregulation of μ-Opioid Receptor in the Rat Spinal Cord Contributes to the α2-Adrenoceptor Agonist Dexmedetomidine-Induced Attenuation of Chronic Morphine Tolerance in Cancer Pain

Background

Sustained morphine treatment for cancer pain has been limited due to analgesic tolerance. Opioid receptor internalization and desensitization mediated by downregulation of mu-opioid receptor (MOR) expression have been confirmed as one of the mechanisms of chronic morphine tolerance. In addition to the opiate system, the α2-adrenergic system is involved in the development of morphine tolerance. Several studies reported that co-administration of α2-adrenoceptor agonist dexmedetomidine inhibits morphine tolerance in normal or neuropathic pain animals. However, the effect of dexmedetomidine on morphine tolerance has not been studied in cancer pain. Therefore, we investigated the effect of intrathecal injection of dexmedetomidine on the development of morphine tolerance in cancer pain and on the expression of MOR in the spinal cord of morphine-tolerant cancer pain rats.

Methods

The model was established using a rat’s right hind paw injection of Walker 256 cancer cells. Subcutaneous morphine (10mg/kg) was administrated twice daily for 7 days; meanwhile, the rats received intrathecal α2-adrenoceptor agonist dexmedetomidine (10μ/kg) or antagonist MK-467 (0.25mg/kg) in test groups. Rats receiving drug vehicle served as the control group. Antinociception was detected by von Frey filaments and hot-plate tests. The expression of MOR in the spinal cord was examined through real-time reverse transcription polymerase chain reaction and Western blotting. The data were analyzed via analysis of variance followed by Student t-test with Bonferroni correction.

Results

Seven-day chronic morphine administration elicited notable analgesic tolerance in the rats with cancer pain. Co-administration of α2-adrenoceptor agonist dexmedetomidine enhanced morphine analgesia and attenuated morphine tolerance, which could be blocked by α2-adrenoceptor antagonist MK-467. Furthermore, pre-treatment of dexmedetomidine significantly upregulated MOR protein expression without a notable change in MOR mRNA expression in the spinal cord.

Conclusion

Our findings suggest that intrathecal injection of dexmedetomidine enhanced morphine analgesia and attenuated morphine tolerance in cancer pain, potentially by upregulating MOR expression in the spinal cord. The α2-adrenoceptor agonist may provide a more versatile analgesia option for morphine treatment for cancer pain.

Spinal cord stimulation alleviates intractable pain due to malignant pleural mesothelioma: a case report

Background

Patients with malignant pleural mesothelioma (MPM) frequently complain of intractable pain that is resistant to conservative treatments. Although spinal cord stimulation (SCS) may be promising in the alleviation of such devastating pain, the effects of SCS on MPM-associated pain and the appropriate timing of its application remain unknown.

Case presentation

A 66-year-old man diagnosed with MPM presented with severe neuropathic pain due to rapid progression of the tumor to the intercostal nerves. The patient immediately decided to receive SCS implantation and burst stimulus, which relieved the conservative therapy-resistant pain and improved his sleep and daily activities.

Conclusion

This report suggests that the execution of SCS as soon as possible may help to alleviate MPM symptoms. Since MPM extends aggressively to the thorax and nerves that cause mixed nociceptive and/or neuropathic pain, appropriate pain management requires the proper assessment of the etiology by an expert in pain management.

Tapentadol is effective in the management of moderate-to-severe cancer-related pain in opioid-naïve and opioid-tolerant patients: a retrospective study

Purpose

Tapentadol is a dual-acting mu-opioid receptor agonist and noradrenaline reuptake inhibitor with non-inferior analgesic efficacy to oxycodone and better gastrointestinal tolerability than full mu-opioid receptor agonists. Tapentadol is approved for cancer pain in Japan; however, real-world evidence on tapentadol’s effectiveness and safety for cancer-related pain in Japan is limited.

Methods

This retrospective study evaluated the effectiveness, safety, and tolerability of tapentadol (by patient type—opioid-naïve and opioid-tolerant) in 84 patients with moderate-to-severe cancer pain at Ichikawa General Hospital between September 2014 and August 2016.

Results

Almost 93% of patients achieved clinically relevant pain relief within 4 days (median). Over 90% of patients with neuropathic pain or mixed pain and all patients with nociceptive pain were responders. Pain intensity significantly decreased from baseline through to the end of maintenance period in opioid-naïve and opioid-tolerant patients. No patients discontinued tapentadol due to serious adverse events. No opioid-naïve patients experienced nausea or vomiting during tapentadol treatment. Only three opioid-tolerant patients experienced nausea which was considered to be related to tapentadol.

Conclusion

Tapentadol is effective and well tolerated in opioid-naïve and opioid-tolerant patients with cancer pain of varying pathophysiology, including those with nociceptive and/or neuropathic components. Tapentadol may be considered for first-line use in moderate-to-severe cancer-related pain.

Hydroethanolic Stem Bark Extract of Burkea africana Attenuates Vincristine-Induced Peripheral Neuropathy in Rats

Context. The stem bark of the savanna tree Burkea africana (Hook) (family: Leguminosae) is used in the Ghanaian traditional medicine for the management of various pain-related diseases.

The Complex Balance between Analgesic Efficacy, Change of Dose and Safety Profile Over Time, in Cancer Patients Treated with Opioids: Providing the Clinicians with an Evaluation Tool

Background: Scanty data exist on the integration between the analgesic effect of opioids, dose changes, and adverse events in cancer patients. Methods: To provide further information on this issue, we analysed data on 498 advanced-stage cancer patients treated with strong opioids. At baseline and three visits (at days 7, 14, and 21), pain intensity, oral morphine-equivalent daily dose, and the prevalence of major adverse events were measured. The proportion of responders (pain intensity decrease ≥30% from baseline) and non-responders, as well as of patients with low or high dose escalation, was calculated. Results: Pain intensity strongly decreased from baseline (pain intensity difference −4.0 at day 7 and −4.2 at day 21) in responders, while it was quite stable in non-responders (pain intensity difference −0.8 at day 7 and −0.9 at day 21). In low dose escalation patients (82.4% at final visit), daily dose changed from 52.3 to 65.3 mg; in high dose escalation patients (17.6%), it varied from 94.1 to 146.7 mg. Among responders, high dose escalation patients experienced significantly more frequent adverse events compared to low or high dose escalation patients, while no differences were observed in non-responders. Conclusions: The response to opioids results from the combination of three clinical aspects, which are strongly interrelated. These results provide some thoughts to help clinical evaluations and therapeutic decisions regarding opioid use.

Lack of Efficacy: When Opioids Do Not Achieve Analgesia from the Beginning of Treatment in Cancer Patients

Introduction

Opioids are often used to relieve moderate to severe pain, but their analgesic response may vary. We focused on the absolute lack of analgesic response immediately after beginning opioid treatment, quantifying the proportion of patients with unchanged or worse pain on day 3 (defined as early non-responders (ENRs)) and day 7.

Methods

This is a post-hoc analysis from a randomized controlled trial involving 498 cancer patients with pain, starting to receive WHO step III opioids. On days 1, 3 and 7 pain intensity (PI) was measured.

Results

On day 3, 68 (13.7%) patients were ENRs, 53 no change and 15 greater PI compared to baseline. The relationships between pain and clinical characteristics showed no significant differences between ENRs and Early responders (ERs), except for PI at baseline, which was significantly lower in ENRs. ENRs on day 3 were re-assessed on day 7 to explore the patterns of analgesic response: 31.7% of patients remained NRs, 48.3% had become responders, and 20.0% were poor responders. Adverse drug reactions were similar in ERs and ENRs at each visit.

Discussion

The complete lack of early response to opioids in cancer patients is clinically important and more frequent than expected. Better definition of the mechanism will allow better pain management in cancer and non-cancer patients.

The use of alternative therapies in conjunction with opioids for cancer pain

Introduction: There is a growing recognition of the role of interventional techniques (IT) for the management of cancer pain (CP). However, there are many controversies on how and when to use such techniques. Areas covered: Patients who are unresponsive to systemic opioid analgesics or patients unable to tolerate systemic opioids may benefit from different IT for which the successful use depends on the selection of the right therapy for the right patient. The evidence regarding these techniques is often anecdotal and the potential risks, benefits, alternatives, and complications should be balanced to take a decision. Expert opinion: The successful use of IT depends on many factors, including a careful assessment of previous treatments, patient's characteristics, and the logistics. Risks, benefits, alternatives, and complications should be balanced to take a decision. Although IT have been described as effective in patients with CP, the evidence is still limited, unless for celiac plexus block, which has a high benefit-risk ratio. The intrathecal therapy should be chosen in patients who were poorly responding to opioid therapy, after an appropriate trial with different opioids. A careful selection of patients and techniques, a large experience in performing the procedures, sufficient logistics and staff skills, appropriate indications, and assessment of benefits and risks may help to achieve the best benefit for patients in individual cases.

The Patient with Difficult Cancer Pain

Most patients with cancer pain can be managed with relatively simple methods using oral analgesics at relatively low doses, even for prolonged periods of time. However, in some clinical conditions pain may be more difficult to manage. Various factors can interfere with a desirable and favorable analgesic response. Data from several studies assessing factors of negative pain prognosis have indicated that neuropathic pain, incident pain, psychological distress, opioid addiction, and baseline pain intensity were associated with more difficult pain control. In this narrative review, the main factors that make the therapeutic response to opioids difficult are examined.

Topical morphine for treatment of cancer-related painful mucosal and cutaneous lesions: a double-blind, placebo-controlled cross-over clinical trial

INTRODUCTION

Painful mucosal and cutaneous lesions are often less responsive or even refractory to systemic opioid analgesics. There is evidence suggesting that the effectiveness of topical morphine be restricted to inflammatory pain. The studied groups were small and the observation period relatively short. The aim of this study was to assess the effectiveness and safety of topical morphine for pain related to mucosal lesions and skin ulcers.

MATERIAL AND METHODS

The study was a 14-day randomized placebo-controlled cross-over trial (RCT) with a 28-day follow-up open phase (OP). The trial was conducted in adult patients with localized cancer-related pain and treated with systemic opioids in an oncology center or home hospice. The patients administered 0.2% gel on the mucosal lesion or 0.2% ointment on the skin lesion by themselves, without restrictions regarding the number of doses per day. The primary measurements were mean pain intensity (MPI) and mean pain relief (MPR) on the numeric rating scale (NRS 0-10), and ITT analysis was performed.

RESULTS

Thirty-five patients were randomized to the RCT, and all of them completed 14-day observation. The MPI before the treatment was NRS 5.9 and decreased to 2.5 after morphine (p < 0.0001 vs. placebo). The MPR was 57% after morphine, and 77% of the patients using topical morphine obtained clinically significant (at least 50% of the starting value) pain relief, statistically different from placebo. The analgesic effect was sustained over the 28-day OP period (p = 0.00001). There were only 2 cases of moderate pruritus, and no other side effects were reported.

CONCLUSIONS

Topical morphine was found to be a fast acting, highly effective, and safe medication for mucosal and skin lesions in palliative patients, with a sustainable pain relief effect over the 28-day observation period.

Safe Opioid Use: Management of Opioid-Related Adverse Effects and Aberrant Behaviors

Opioids are highly effective for cancer pain but are associated with multiple adverse effects and risk of addiction. This article provides a synopsis on the management of various opioid-related adverse effects and strategies to minimize aberrant opioid use in patients who have cancer. Many adverse effects can be effectively managed. Some patients on chronic opioid therapy may demonstrate aberrant behaviors suggestive of opioid misuse or diversion. Through intensive education, longitudinal monitoring, early identification, and timely management, clinicians can optimize the risk to benefit ratio to support safe opioid use.

Nonresponsiveness and Susceptibility of Opioid Side Effects Related to Cancer Patients' Clinical Characteristics: A Post-Hoc Analysis

BACKGROUND

The response to opioids is not always positive in cancer patients. A considerable proportion of patients do not respond (nonresponders [NRs]) or experience severe toxicity. The aim of this analysis was to assess the role of demographic characteristics, pain features, comorbidities, and ongoing therapy on the lack of efficacy and on the occurrence of severe adverse drug reactions (ADRs).

METHODS

This is a post-hoc analysis of a randomized controlled trial that involved 520 patients and aimed to evaluate the efficacy and safety of 4 strong opioids. Patients who presented with unchanged or worsened pain compared to the first visit were considered to be NRs. As for toxicity, severe ADRs with an incidence of greater than 10% were evaluated. Univariate and multivariate logistic models were used.

RESULTS

498 patients were analyzed. Liver metastases and breakthrough pain (BTP) were found to increase the risk for nonresponse. Conversely, a high basal pain intensity significantly decreased the same risk. Constipation risk was worsened by previous weak opioid therapy but decreased with aging and with the use of transdermal opioids. Risk for drowsiness was aggravated by bone metastases and concomitant treatment with anticoagulant, antidiabetic, and central nervous system drugs. Risk for confusion increased with antidiabetics, antibiotics, and previous weak opioid therapy but decreased when fentanyl was used. Occurrence of nausea increased in patients with a high rating on the Karnofsky Performance Status Index. Risk for xerostomia was higher in women and in patients treated with antidiabetic or long-term opioids.

CONCLUSIONS

Several clinical variables are correlated with opioid response in cancer patients. In particular, the presence of BTP is associated with nonresponse. Additionally, patients who receive polypharmacological therapy are more likely to experience opioid adverse events.

Effects of Electroacupuncture Treatment on Bone Cancer Pain Model with Morphine Tolerance

Objective. To explore the efficacy of electroacupuncture treatment in cancer induced bone pain (CIBP) rat model with morphine tolerance and explore changes of calcitonin-gene related peptide (CGRP) expression in dorsal root ganglion (DRG). Methods. Forty SD rats were divided into five groups: sham, CIBP (B), CIBP + morphine (BM), CIBP + electroacupuncture (BE), and CIBP + morphine + electroacupuncture (BME). B, BM, BE, and BME groups were prepared CIBP model. The latter three groups then accepted morphine, electroacupuncture, and morphine combined electroacupuncture, separately, nine days consecutively (M1 to M9). Mechanical withdraw threshold (MWT) was evaluated. Results. BE group only had differences in M1, M2, and M3 compared to B group (P < 0.01). From M5, BM group showed significantly decreased MWT. Electroacupuncture could obtain analgesic effects only at early stage (M1 to M5). From M5 to M9, BME had the differences with BM group (P < 0.01). IOD value of CGRP in BM and BME was substantially less than in B group. CGRP in BME was significantly lower than that in BM group (P < 0.01). Conclusion. When used in combination with electroacupuncture, morphine could result in improving analgesic effects and reducing tolerance. CGRP may be associated with pain behaviors.

Methadone for cancer pain: What have we learned from clinical studies?

The analgesic ladder guideline proposed by the World Health Organization has been shown to be effective in controlling cancer pain in about 80 percent of patients, but the remaining 20 percent still experience pain. Several strategies have been used to manage refractory cancer pain and opioid toxicity. Switching opioids, alternative routes of opioid administration, optimizing adjuvants, and invasive procedures are proposed treatments. Extensive medical literature corroborates each one of those treatments. Rotation from one opioid to another is a noninvasive strategy to overcome opioid side effects and refractory pain. Frequently, methadone is used during opioid rotation. However, there is a lack of consensus on how to proceed on rotation from morphine to methadone. In the current era of evidence-based medicine, the medical literature fails to answer some cancer pain-management issues. The purpose of this review is to clarify a process for transitioning from morphine to methadone.

Cognitive Effects and Sedation

OBJECTIVE

Cognitive effects and sedation (CES) are prevalent in chronic nonmalignant pain populations receiving long-term opioid therapy and are among the most common reasons patients discontinue opioid use. In this narrative review, we describe the phenomenology, epidemiology, mechanisms, assessment, and management of opioid-related CES.

DESIGN

We reviewed the empirical and theoretical literature on CES in opioid-treated populations with chronic pain. Data on long-term opioid therapy (≥ 3 months in duration) in chronic nonmalignant pain patients were sought.

RESULTS

The phenomenology of CES includes: inattention, concentration difficulties, memory deficits, psychomotor dysfunction, perceptual distortions, and executive dysfunction and somnolence, sleep disorders, and lethargy. Deficits may be caused by unrelieved pain or opioid therapy alone, or from a combination of these and other factors. Mechanisms include central nervous system effects, for example, direct toxic effects on neurons resulting in decreased consciousness; direct effects on processing and reaction resulting in cognitive or psychomotor impairment, and inhibitory effects on cholinergic activity. Pharmacological management approaches may include opioid dose reduction and rotation or psychostimulant use. Nonpharmacological approaches may include cognitive-behavioral therapy, mindfulness-based stress reduction, acupuncture, exercise, and yoga.

CONCLUSIONS

The most prevalent CES include: memory deficits (73-81%), sleep disturbance (35-57%), and fatigue (10%). At its most severe, extreme cognitive dysfunction can result in frank delirium and decreased alertness can result in coma. Emotional distress, sleep disorders, and other comorbidities and treatments can worsen CES, particularly among the elderly. Conclusions about the neuropsychological domains affected by opioids are limited due to the heterogeneity of studies and methodological issues.

MicroRNAs Are Involved in the Development of Morphine-Induced Analgesic Tolerance and Regulate Functionally Relevant Changes in Serpini1

Long-term opioid treatment results in reduced therapeutic efficacy and in turn leads to an increase in the dose required to produce equivalent pain relief and alleviate break-through or insurmountable pain. Altered gene expression is a likely means for inducing long-term neuroadaptations responsible for tolerance. Studies conducted by our laboratory (Tapocik et al., 2009) revealed a network of gene expression changes occurring in canonical pathways involved in neuroplasticity, and uncovered miRNA processing as a potential mechanism. In particular, the mRNA coding the protein responsible for processing miRNAs, Dicer1, was positively correlated with the development of analgesic tolerance. The purpose of the present study was to test the hypothesis that miRNAs play a significant role in the development of analgesic tolerance as measured by thermal nociception. Dicer1 knockdown, miRNA profiling, bioinformatics, and confirmation of high value targets were used to test the proposition. Regionally targeted Dicer1 knockdown (via shRNA) had the anticipated consequence of eliminating the development of tolerance in C57BL/6J (B6) mice, thus supporting the involvement of miRNAs in the development of tolerance. MiRNA expression profiling identified a core set of chronic morphine-regulated miRNAs (miR's 27a, 9, 483, 505, 146b, 202). Bioinformatics approaches were implemented to identify and prioritize their predicted target mRNAs. We focused our attention on miR27a and its predicted target serpin peptidase inhibitor clade I (Serpini1) mRNA, a transcript known to be intricately involved in dendritic spine density regulation in a manner consistent with chronic morphine's consequences and previously found to be correlated with the development of analgesic tolerance. In vitro reporter assay confirmed the targeting of the Serpini1 3'-untranslated region by miR27a. Interestingly miR27a was found to positively regulate Serpini1 mRNA and protein levels in multiple neuronal cell lines. Lastly, Serpini1 knockout mice developed analgesic tolerance at a slower rate than wild-type mice thus confirming a role for the protein in analgesic tolerance. Overall, these results provide evidence to support a specific role for miR27a and Serpini1 in the behavioral response to chronic opioid administration (COA) and suggest that miRNA expression and mRNA targeting may underlie the neuroadaptations that mediate tolerance to the analgesic effects of morphine.

Are strong opioids equally effective and safe in the treatment of chronic cancer pain? A multicenter randomized phase IV 'real life' trial on the variability of response to opioids

BACKGROUND

Guidelines tend to consider morphine and morphine-like opioids comparable and interchangeable in the treatment of chronic cancer pain, but individual responses can vary. This study compared the analgesic efficacy, changes of therapy and safety profile over time of four strong opioids given for cancer pain.

PATIENT AND METHODS

In this four-arm multicenter, randomized, comparative, of superiority, phase IV trial, oncological patients with moderate to severe pain requiring WHO step III opioids were randomly assigned to receive oral morphine or oxycodone or transdermal fentanyl or buprenorphine for 28 days. At each visit, pain intensity, modifications of therapy and adverse drug reactions (ADRs) were recorded. The primary efficacy end point was the proportion of nonresponders, meaning patients with worse or unchanged average pain intensity (API) between the first and last visit, measured on a 0-10 numerical rating scale. (NCT01809106).

RESULTS

Forty-four centers participated in the trial and recruited 520 patients. Worst pain intensity and API decreased over 4 weeks with no significant differences between drugs. Nonresponders ranged from 11.5% (morphine) to 14.4% (buprenorphine). Appreciable changes were made in the treatment schedules over time. Each group required increases in the daily dose, from 32.7% (morphine) to 121.2% (transdermal fentanyl). Patients requiring adjuvant analgesics ranged from 68.9% (morphine) to 81.6% (oxycodone), switches varied from 22.1% (morphine) to 12% (oxycodone), discontinuation of treatment from 27% ( morphine) to 14.5% (fentanyl). ADRs were similar except for effects on the nervous system, which significantly prevailed with morphine.

CONCLUSION

The main findings were the similarity in pain control, response rates and main adverse reactions among opioids. Changes in therapy schedules were notable over time. A considerable proportion of patients were nonresponders or poor responders.

CLINICAL TRIAL REGISTRATION

NCT01809106 (https://clinicaltrials.gov/ct2/show/NCT01809106?term=cerp&rank=2).

The role of analgesic adjustment strategies in achieving analgesic efficacy in opioid-tolerant hospice patients in China

Diverse strategies of analgesic adjustment are often, respectively, used to sustain analgesic efficiency for opioid-tolerant patients with different refractory factors of pain. In order to select effective analgesic adjustment strategy for hospice patient without knowing explicit causes of diminishing analgesic efficiency, a retrospective data of 743 patients among 3760 hospice patients were analyzed. The efficacy and adverse effects were not significantly different among analgesic adjustment strategies at each adjustment. Opioid duration was not associated with clinical characteristics. For opioid-tolerant hospice patients, the analgesic adjustment strategy can be selected for individual patient. After repeated analgesic adjustments, opioid tapering may also occur.

Budget impact analysis of the fentanyl buccal tablet for treatment of breakthrough cancer pain

BACKGROUND

The purpose of this study was to assess the economic impact of the fentanyl buccal tablet for the management of breakthrough cancer pain (BTcP) in Spain.

METHODS

A 4-year budget impact model was developed for the period 2012-2015 for patients with BTcP from the perspective of the Spanish National Health System. BTcP products included in this model were rapid-onset opioids containing fentanyl (buccal, sublingual, or nasal transmucosal). Prevalence data on cancer, BTcP, opioid use, and number of BTcP episodes were obtained from the literature. Input data on health care resources associated with opioid use and opioid-induced side effects were obtained by consulting experts in oncology from different Spanish hospitals. Resources used included drugs, medical and emergency visits, other nonpharmacologic treatments, and treatment of opioid-induced side effects. Unit costs were obtained from the literature, and a 3% discount rate was applied to costs. Based on the unit costs for drugs and health care resources, the annual BTcP treatment costs per patient associated with each fentanyl product were determined to estimate the overall budget impact based on the total treatment population and the percentage of drug utilization associated with each product. One-way sensitivity analyses were conducted to test the robustness of the model.

RESULTS

Patients treated with oral opioids for BTcP were estimated at 23,291 in 2012, with an increase up to 23,413 in 2015. The average annual budget savings, with an increase of fentanyl buccal tablets, fentanyl sublingual tablets, and intranasal fentanyl spray, and a decrease in oral transmucosal fentanyl citrate, was estimated at €2.6 million, which represents a 0.5% decrease in the total costs of BTcP over the next 4 years. Results of the sensitivity analysis showed that the model was most sensitive to drug cost per day for the fentanyl buccal tablet. A 50% decrease in the daily cost of the fentanyl buccal tablet resulted in the largest overall decrease in budget impact of €5.4 million.

CONCLUSION

The increase in use of the fentanyl buccal tablet leads to overall savings in the budget impact for the Spanish National Health System. Although the economic impact of treatment for BTcP was shown to increase over 4 years due to population growth, the average annual cost per patient was reduced by €29 with increased use of the fentanyl buccal tablet.

Effects of acupuncture for cancer pain and quality of life - a case series

BACKGROUND

Many cancer patients seek complementary and alternative medicine (CAM) including acupuncture to manage their cancer-related symptoms or side effects of treatments. Acupuncture is used to manage cancer pain and improve quality of life (QoL). This study aimed to conduct a preliminary study on a case series to evaluate the feasibility of acupuncture for treating cancer pain and to collect preliminary data on the effectiveness of acupuncture in treating cancer pain and improving QoL.

METHODS

A semi-standardized acupuncture treatment comprising one to three treatment sessions (20-30 minutes per session) per week for 8 weeks was provided by four licensed acupuncturists, who had more than 5 years of clinical experience, at the University Health Center. The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C3) and a visual analogue scale (VAS) for pain rating were used as the outcome measures to assess pain and QoL. Data were collected at baseline, immediately after 2, 4, 6, and 8 weeks of treatment and at 4 weeks after treatment completion (week 12).

RESULTS

Two males and five females with a median age of 66 years (range: 44-71 years) completed the study. For the VAS, the percentage of improvement ranged between 18% and 95%. The baseline mean raw score was reduced from 51 mm to 36 mm at the end of week 8 and to 23 mm at the end of week 12. The percentage of overall QoL improvement ranged between 20% and 100%. The mean raw score for QoL improved with time. The baseline score was increased from 55 to 69 at the end of treatment (week 8) and to 73 after the follow-up (week 12).

CONCLUSIONS

This pilot study on a case series showed that acupuncture might be beneficial for reducing pain and improving QoL in cancer patients.

The non-selective cannabinoid receptor agonist WIN 55,212-2 attenuates responses of C-fiber nociceptors in a murine model of cancer pain

Pain from cancer can be severe, difficult to treat, and greatly diminishes patients' quality of life. It is therefore important to gain new information on the mechanisms of cancer pain and develop new treatment strategies. We have used a murine model of bone cancer pain to investigate underlying peripheral neural mechanisms and novel treatment approaches. In this model, implantation of fibrosarcoma cells into and around the calcaneous bone produces mechanical and thermal hyperalgesia in mice. C-fiber nociceptors in tumor-bearing mice develop spontaneous ongoing activity and sensitization to thermal stimuli. However, it is unclear whether sensitization of nociceptors to mechanical stimuli underlies the mechanical hyperalgesia seen in tumor-bearing mice. We therefore examined responses of C-fiber nociceptors to suprathreshold mechanical stimuli in tumor-bearing mice and found they did not differ from those of C-nociceptors in control mice. Thus, sensitization of C-fiber nociceptors to mechanical stimulation does not appear to underlie tumor-evoked mechanical hyperalgesia in this murine model of bone cancer pain. We also examined the effect of the non-selective cannabinoid receptor agonist, WIN 55,212-2, on spontaneous activity and responses evoked by mechanical stimuli of C-fiber nociceptors innervating the tumor-bearing paw. Selective CB1 and CB2 antagonists were administered to determine the contribution of each receptor subtype to the effects of WIN 55,212-2. Intraplantar administration of WIN 55,212-2 attenuated spontaneous discharge and responses evoked by mechanical stimulation of C-fiber nociceptors. These effects were inhibited by prior intraplantar administration of selective CB1 (AM281) or CB2 (AM630) receptor antagonists but not by vehicle. These results indicate that activation of either CB1 or CB2 receptors reduced the spontaneous activity of C-fiber nociceptors associated with tumor growth as well as their evoked responses. Our results provide further evidence that activation of peripheral cannabinoid receptors may be a useful target for the treatment of cancer pain.

Frequency, outcome, and predictors of success within 6 weeks of an opioid rotation among outpatients with cancer receiving strong opioids

BACKGROUND

Opioid rotation is used to treat uncontrolled pain and/or opioid-related adverse effects. Our aim was to determine the frequency, indications, outcomes, and predictors of successful opioid rotation in outpatients with cancer.

METHODS

Medical records of consecutive outpatients with cancer who received strong opioids and returned for follow-up visit within ≤6 weeks to our supportive care center from January to December 2008 were reviewed. Data on patient characteristics, symptoms, opioid use, indications for opioid rotation, outcomes, and morphine equivalent daily dose were collected. Successful opioid rotation was defined as a two-point or 30% reduction in the symptom score or the resolution of opioid-induced neurotoxicity and continuation of the new opioid at follow-up.

RESULTS

Opioid rotation was performed in 120 of 385 patients (31%). The median patient age was 55 years. There were 6/120 patients with missing data. Of the 114 evaluable patients, 68 (60%) were men, 81 (71%) were white, 27 (24%) had gastrointestinal cancer, and 90 (80%) had advanced-stage disease. The median Eastern Cooperative Oncology Group score was 1 (interquartile range: 1-2) and the median time between opioid rotation and follow-up was 14 days (interquartile range: 7-21 days). The most common indications for opioid rotation were uncontrolled pain (95/114; 83%) and opioid-induced neurotoxicity (13/114; 12%). A total of 35 patients (31%) had partial opioid rotation. The median improvements in pain and symptom distress score were -2 (interquartile range: -4 to 0; p < .001) and -5 (interquartile range: -14 to 7; p = .004), respectively. The morphine equivalent daily dose did not change significantly after opioid rotation (p = .156). A total of 65% of patients (74/114) had successful opioid rotation. There were no clinically significant independent predictors for successful opioid rotation.

CONCLUSION

Opioid rotation was conducted in 31% of outpatients with cancer, with a 65% success rate. The most frequent reason for opioid rotation was uncontrolled pain. There were no independent predictors for successful opioid rotation.

Opioid-induced or pain relief-reduced symptoms in advanced cancer patients?

BACKGROUND

While opioids in increasing doses may produce adverse effects, the same adverse effects may be associated with poor pain control. Moreover, in the clinical setting symptomatic treatment and illness may balance the outcome of opioid titration. Some adverse effects may tend to disappear continuing the treatment in a long-term period.

AIMS

The aim of this study was to monitor the effects of a rapid opioid titration combined with symptomatic treatment in patients with poor relief and to monitor these changes in the following period of 20 days.

METHODS

A consecutive sample of 35 patients admitted to an acute Pain Relief and Palliative Care Unit were titrated with opioids, according to a department policy, allowing administration of parenteral opioids to assist opioid titration with oral or transdermal opioids.

RESULTS

Thirty-three patients were followed up for the period of the study. Pain was adequately controlled and doses were opioid doses were stable after a mean of 40 h. Opioid escalation index (OEI) was extremely high initially, and then progressively declined at the following study intervals. Weakness and nausea and vomiting did not change, as well as confusion and appetite. Drowsiness, constipation and dry mouth significantly increased and then did not change, although a significant decrease in drowsiness was subsequently observed. Well-being improved some weeks after opioid stabilization. In multivariate analysis, drowsiness and dry mouth were correlated to opioid doses.

CONCLUSION

The effects reported were often due to multiple causes. A rapid decrease in pain intensity induced by rapid opioid titration does not produce changes in weakness, nausea and vomiting, appetite. While constipation appears the most relevant problem, resistant to common symptomatic treatment, drowsiness initially produced by acute opioid dose increase and the achievement of pain relief, tends to spontaneously decrease, probably as the result of late tolerance. Improved well-being may be the late positive effect of pain relief, also influenced by the setting of home care.

Prospects and challenges in opioid analgesia for pain management

Pain is still one of the most prevalent and distressing symptom in patients with chronic pain. Opioids are the most potent existing analgesics available in clinical practice. However, they are not always effective, particularly in the non-cancer population. Alternately adverse effects may limit their analgesic activity. Several different drug-development strategies have attempted to reduce side effects by exploiting anatomic barriers to drug distribution and to provide different analgesic mechanisms, as in the case of the oxycodone-naloxone combination or tapentadol. New delivery systems have been developed for a more effective management of breakthrough pain. Pharmacogenetics could play a critical role in personalizing pain management in the future.

Adverse effects in hospice patients with chronic kidney disease receiving hydromorphone

BACKGROUND

Pain is one the most common symptoms experienced by palliative care patients. The treatment of pain involves the use of strong opioids such as hydromorphone, morphine, methadone, fentanyl, oxycodone, oxymorphone, or levorphanol for moderate to severe pain. Hydromorphone is metabolized by the liver to hydromorphone-3-glucuronide (H3G), a compound that can potentially cause neuroexcitatory phenomena with accumulation. Pharmacokinetic studies have shown that H3G levels in patients with renal insufficiency are 4 times as high as those with normal renal function; however, reports have been conflicting as to whether or not it is safe to use hydromorphone in renal insufficiency.

METHODS

In this study we sought to determine the prevalence of neuroexcitation in patients with renal insufficiency who were given hydromorphone, as measured by the glomerular filtration rate (GFR), and to investigate factors associated with increased risk of neuroexcitation in this patient group. For the 12- month period from June 2007 through June 2008, charts of inpatient hospice patients that showed a glomerular filtration rate of <60 (mL/min/1.73 m(2)) and hydromorphone administration for pain control via continuous infusion were reviewed for the occurrence of neuroexcitatory effects, including tremor, myoclonus, agitation, cognitive dysfunction, and seizures.

RESULTS

Overall prevalence of neuroexcitatory effects were: tremor 11 (20%), myoclonus 11 (20%), agitation 26 (48%), and cognitive dysfunction 21 (39%). No seizures were observed. No neuroexcitatory effects were observed for the lowest quartile of dose or duration of hydromorphone. There was a strong and graded increase in neuroexcitatory effects with increasing quartile of dose or duration of hydromorphone for agitation (dose, p<0.0001; duration, p<0.0001) and cognitive dysfunction (dose, p<0.0002; duration, p<0.002). Consistent but weaker trends were observed for tremor and myoclonus.

CONCLUSION

Parenteral hydromorphone has few neuroexcitatory symptoms until H3G accumulates past a neurotoxic threshold, such as might occur with increasing dose or duration, which, when exceeded, causes neuroexcitatory symptoms to manifest.

P2X7 receptor-deficient mice are susceptible to bone cancer pain

The purinergic P2X7 receptor is implicated in both neuropathic and inflammatory pain, and has been suggested as a possible target in pain treatment. However, the specific role of the P2X7 receptor in bone cancer pain is unknown. We demonstrated that BALB/cJ P2X7 receptor knockout (P2X7R KO) mice were susceptible to bone cancer pain and moreover had an earlier onset of pain-related behaviours compared with cancer-bearing, wild-type mice. Furthermore, acute treatment with the selective P2X7 receptor antagonist, A-438079, failed to alleviate pain-related behaviours in models of bone cancer pain with and without astrocyte activation (BALB/cJ or C3H mice inoculated with 4T1 mammary cancer cells or NCTC 2472 osteosarcoma cells, respectively), suggesting that astrocytic P2X7 receptors play a negligible role in bone cancer pain. The results support the hypothesis that bone cancer pain is a separate pain state compared with those of neuropathic and inflammatory pain. However, the recent discovery of a P2X7 receptor splice variant expressed in the knockout mice used for this study complicates the interpretation of the results. The P2X7 splice variant receptor was detected in the spinal cord but not in osteoclasts of the P2X7R KO mouse. Further experiments are needed to elucidate the exact role of the P2X7 receptors in bone cancer pain.

Combined catechol-O-methyltransferase and mu-opioid receptor gene polymorphisms affect morphine postoperative analgesia and central side effects

BACKGROUND

Previous studies have generated controversial results regarding the influence of the genetic variations of μ-opioid receptors on morphine analgesia and opioid-related side effects in the postoperative period. Few studies have been conducted attempting to assess the combined effects of variation within ≥2 genes in relation to morphine response. In this study, we investigated whether combined catechol-O-methyltransferase and μ-opioid receptor polymorphisms contribute to the morphine response in postoperative analgesia.

METHODS

One hundred two surgical patients were enrolled in this prospective, observational study. All patients received general anesthesia and were screened for μ-opioid receptor polymorphism A118G (Asn40Asp) and catechol-O-methyltransferase G1947A (Val158Met) polymorphism using a blood sample of DNA. Patient-controlled analgesia was provided postoperatively and morphine consumption was observed. Any pain at rest or side effects were measured with rating scales.

RESULTS

The heterozygous patients with μ-opioid receptor A118G and catechol-O-methyltransferase G1947A mutation consumed significantly less morphine in the postanesthetic recovery room and 48 hours after surgery compared with homozygous patients of the A118 variant. Nausea and sedation scores were also significantly lower during all observed postoperative periods for heterozygous patients and only 2 patients (18%) from this group received antinausea treatment.

CONCLUSION

This study has demonstrated the importance of the gene-gene approach in understanding the morphine response in patients after lower abdominal surgery. More studies are needed to characterize the combined effects of multiple genes and demographic as well as clinical variables in predicting the correct morphine dosage and corresponding opioid-related side effects.

Methadone for Cancer Pain

Pain is one of the most common and incapacitating symptoms experienced by patients with advanced cancer. Methadone is a potent opioid with strong affinity for the µ opioid receptor. In addition to being a potent µ opioid receptor ligand, methadone blocks the N-methyl-D-aspartic acid receptor and modulates neurotransmitters involved in descending pain modulation. These 3 properties enhance analgesic activity. Methadone's lack of active metabolites makes it an attractive option when opioid responsiveness declines and renal insufficiency complicates opioid therapy. A lipophilic opioid, methadone can be given by multiple routes. Clinical trial data show equivalence with morphine as an analgesic in moderate to severe cancer pain. Further investigations are needed to define the role of methadone in the management of breakthrough pain and neuropathic pain and to determine whether it is truly superior to morphine, the gold standard of cancer analgesia.

Cost-effectiveness of ziconotide in intrathecal pain management for severe chronic pain patients in the UK

OBJECTIVE

To examine the cost-effectiveness of using intrathecal ziconotide in the treatment of severe chronic pain compared to best supportive care for patients with intractable chronic pain in the United Kingdom.

METHODS

Using a simulation model, the analysis evaluated the cost and health economic consequences of using ziconotide as a treatment for severe chronic pain. The modelled population and clinical data were based on a randomised controlled trial in which the main outcome was reduction in pain as measured by the visual analogue scale of pain intensity (VASPI). Resource use data were elicited using a modified Delphi panel and costed using published sources. Utility values were derived from a separate research study. The main outcome measure was the cost per quality-adjusted life-year (QALY). Extensive scenario analysis was conducted to evaluate parameter uncertainty.

RESULTS

Overall, findings were robust to most assumptions. The cost-effectiveness of ziconotide compared to best supportive care (BSC) was pound 27,443 per QALY (95% CI pound 18,304-38,504). Scenarios were investigated in which discount rates, the time horizon, the threshold for qualifying as a responder, pump-related assumptions, utilities, ziconotide drug dose, and the patient discontinuation rate with ziconotide were varied. The most sensitive parameter was the dosage of ziconotide: using the lower and upper bounds of the average ziconotide dosage observed in the long-term open-label study changed the incremental cost-effectiveness ratio (ICER) to pound 15,500 [pound 8206-25,405] and pound 44,700 [pound 30,541-62, 670].

CONCLUSIONS

Ziconotide may offer an economically feasible alternative solution for patients for whom current treatment is inappropriate or ineffective. The main study limitation is that some model inputs, mainly related to resource use, are based on assumptions or expert interviews.

An intravenous ketamine test as a predictive response tool in opioid-exposed patients with persistent pain

Chronic pain patients who are treated with opioid therapy represent a significant challenge to medical professionals. When pain recurs in the face of a previously effective opioid regimen, treatment options include dose escalation, opioid rotation, drug holidays, and the addition of adjuvants. Some experts advocate the use of N-methyl-D-aspartate receptor (NMDA-R) antagonists to combat tolerance. Recently, the use of an intravenous (i.v.) ketamine infusion to predict the response to a dextromethorphan (DX) treatment trial has been described. In this study, 56 opioid-exposed patients with recurrent pain were treated with a low-dose (0.1mg/kg) i.v. ketamine test followed by a DX treatment course. Using previously designated cutoff values for a positive response to ketamine (67% or more pain relief) and DX (50% or more pain relief), the sensitivity, specificity, positive predictive value, and negative predictive value for an i.v. ketamine infusion to predict subsequent response to DX treatment were 72%, 68%, 52%, and 85%, respectively. The observed agreement between analgesic responses was 78%, indicating a highly significant correlation (r=0.54, P=0.0001). Subgroup classification revealed no significant differences in the response to either ketamine or DX treatment based on pain classification (i.e., nociceptive, neuropathic, or mixed) or placebo response. In contrast, a weaker correlation between ketamine and DX response was found in subjects requiring high-dose rather than low-dose opioid therapy. A significant correlation also was noted between the development of side effects for the two NMDA-R antagonists. Based on these results, we conclude that an i.v. ketamine test may be a valuable tool in predicting subsequent response to DX treatment in opioid-exposed patients. with persistent pain.

Frequency, indications, outcomes, and predictive factors of opioid switching in an acute palliative care unit

The aim of this study was to prospectively evaluate the frequency, indications, outcomes, and predictive factors associated with opioid switching, using a protocol that had been clinically applied and viewed as effective for many years. A prospective study was carried out on a cohort of consecutive cancer patients who were receiving opioids but had an unacceptable balance between analgesia and adverse effects, despite symptomatic treatment of side effects. The initial conversion ratio between opioids and routes was as follows (mg/day): oral morphine 100=intravenous morphine 33=transdermal fentanyl 1=intravenous fentanyl 1=oral methadone 20=intravenous methadone 16=oral oxycodone 70=transdermal buprenorphine 1.3. The switch was assisted by opioids used as needed, and doses were changed after the initial conversion according to clinical response in an acute care setting. Intensity of pain and symptoms associated with opioid therapy were recorded. A distress score (DS) was calculated as a sum of symptom intensity. A switch was considered successful when the intensity of pain and/or DS, or the principal symptom necessitating the switch, decreased to at least 33% of the value recorded before switching. One hundred eighteen patients underwent opioid substitutions. The indications for opioid switching were uncontrolled pain and adverse effects (50.8%), adverse effects (28.8%), uncontrolled pain (15.2%), and convenience (4.2%). Overall, 103 substitutions were successful. Ninety-six substitutions were successful after the first switching, and a further substitution was successful in seven patients who did not respond to the first switch. The mean time to achieve dose stabilization after switching was 3.2 days. The presence of both poor pain control and adverse effects was related to unsuccessful switching (P<0.004). No relationship was identified between unsuccessful switching and the opioid dose, opioid sequence, pain mechanism, or use of adjuvant medications. Opioid switching was an effective method to improve the balance between analgesia and adverse effects in more than 80% of cancer patients with a poor response to an opioid. The presence of both poor pain relief and adverse effects is a negative factor for switching prognosis, whereas renal failure is not.