Improved Opioid Analgesic Effect Following Opioid Dose Reduction

Blocking IL-17A prevents oxycodone-induced depression-like effects and elevation of IL-6 levels in the ventral tegmental area and reduces oxycodone-derived physical dependence in rats

Oxycodone is the most prescribed opioid for pain management and has been available in clinics for almost a century, but effects of chronic oxycodone have been studied less than morphine in preclinical and clinical studies. Newly developed depression has been coupled with chronic oxycodone use in a few clinical studies, but no preclinical studies have investigated the pathogenesis of oxycodone-induced depression. Gut microbiome changes following oxycodone use is an understudied area, and interleukin-17A (IL-17A) is linked to both the development of mood disorders and regulation of gut microbiome. The present study investigated effects of chronic oxycodone exposure on mood-related behaviors (depression and anxiety), pain hypersensitivity, physical dependence, immune markers, and the gut microbiome and tested the hypothesis that blocking IL-17A with a systemically administered monoclonal antibody reduces oxycodone-derived effects. Oxycodone (using an incremental dosing regimen) or saline was injected twice a day for 12 days. IL-17A Ab (200 µg/100 µl) or saline was administered every 3rd day during the 12-day interval. Chronic oxycodone induced a depression-like effect, but not anxiogenic- or anxiolytic-like effects; promoted hyperalgesia; increased IL-17A and IL-6 levels in the ventral tegmental area (VTA); and induced physical dependence. IL-17A Ab co-administration with oxycodone prevented the depression-like effect and hyperalgesia, reduced naloxone-precipitated withdrawal signs, and normalized the increase in cytokine levels. Chronic oxycodone exposure did not affect gut microbiome and integrity. Our results identify a role for IL-17A in oxycodone-related behavioral and neuroimmune effects and show that IL-17A Ab has potential therapeutic value in blocking these effects. Given that humanized IL-17A Ab is approved for treatment of psoriasis and psoriatic arthritis, our findings point toward studying it for use in the treatment of oxycodone use disorder.

Interactions between Ketamine and Magnesium for the Treatment of Pain: Current State of the Art

BACKGROUND

Over the past three decades, NMDA-receptor antagonists have been shown to be efficient drugs for treating pain, particularly pain resistant to conventional analgesics. Emphasis will be on the old-new drugs, ketamine and magnesium, and their combination as a novel approach for treating chronic pain.

METHODS

The MEDLINE database was searched via PubMed for articles that were published up to March 1, 2020, with the keywords 'ketamine', 'magnesium', and 'pain' (in the title/abstract).

RESULTS

Studies in animals, as well as humans, have shown that interactions of ketamine and magnesium can be additive, antagonistic, and synergistic. These discrepancies might be due to differences in magnesium and ketamine dosage, administration times, and the chronological order of drug administration. Different kinds of pain can also be the source of divergent results.

CONCLUSION

This review explains why studies performed with a combination of ketamine and magnesium have given inconsistent results. Because of the lack of efficacy of drugs available for pain, ketamine and magnesium in combination provide a novel therapeutic approach that needs to be standardized with a suitable dosing regimen, including the chronological order of drug administration.

Opioid Tapering/Detoxification Protocols, A Compendium: Narrative Review

OBJECTIVES

The opioid epidemic has put pressure on clinicians to taper their chronic pain patients (CPPs) from opioids. This has resulted in rapid or forced tapers and opioid discontinuation. Partially responsible is lack of information on how to taper (tapering protocols).The objectives of this narrative review were then the following: compile all the published opioid tapering/detoxification protocols from the pain/drug rehabilitation/psychiatric literature whether for inpatient or outpatient use; organize these into general types; compare the types for advantages/disadvantages for use by a clinician in an outpatient setting; and answer some commonly asked questions relating to opioid tapering.

METHODS

Relevant references were identified by a search strategy utilizing the terms tapering, tapering protocols, detoxification, detoxification protocols, withdrawal, dependence, addiction, and drug rehabilitation. These were explored with the term opioids. Identified abstract were reviewed for any study relating to the objectives of this review. Those studies were then included in this review. As this is a narrative review, no quality ratings of these references were performed.

RESULTS

Of 1,922 abstracts identified by this search strategy, 301 were reviewed in detail for potential inclusion. Of these, 104 were utilized in this review. Nine types of opioid tapering protocols were identified and compared in tabular form. Twenty-two questions in reference to opioid tapering were addressed.

CONCLUSIONS

Based on this review, the protocol utilizing the opioid of current use is the simplest to use as it requires no rotation to another opioid and thereby avoids rotation errors. It also has behavior advantages.

Attitudes Towards and Management of Opioid-induced Hyperalgesia: A Survey of Chronic Pain Practitioners

OBJECTIVES

Opioid-induced hyperalgesia (OIH) is a phenomenon whereby opioids increase patients' pain sensitivity, complicating their use in analgesia. We explored practitioners' attitudes towards, and knowledge concerning diagnosis, risk factors, and treatment of OIH.

MATERIALS AND METHODS

We administered an 18-item cross-sectional survey to 850 clinicians that managed chronic pain with opioid therapy.

RESULTS

The survey response rate was 37% (318/850). Most respondents (240/318, 76%) reported they had observed patients with OIH in their practice, of which 38% (84/222) reported OIH affected >5% of their chronic pain patients. The majority (133/222, 60%) indicated that OIH could result from any dose of opioid therapy. The most commonly endorsed chronic pain conditions associated with the development of OIH were fibromyalgia (109/216, 51%) and low back pain (91/216, 42%), while 42% (91/216) indicated that no individual chronic pain condition was associated with greater risk of OIH. The most commonly endorsed opioids associated with the development of OIH were oxycodone (94/216, 44%), fentanyl (86/216, 40%), and morphine (84/216, 39%); 27% (59/216) endorsed that no specific opioid was more likely to result in OIH. Respondents commonly managed OIH by opioid dose reduction (147/216, 68%), administering a nonopioid adjuvant (133/216, 62%), or discontinuing opioids (95/216, 44%).

DISCUSSION

Most clinicians agreed that OIH is a complication of opioid therapy, but were divided regarding the prevalence of OIH, etiological factors, and optimal management.

Effect of Stellate Ganglion Block on Intraoperative Propofol and Fentanyl Consumption in Patients with Complex Regional Pain Syndrome Undergoing Surgical Repair of Brachial Plexus Injury: A Randomized, Double-blind, Placebo-controlled Trial

Introduction

Stellate ganglion block (SGB) is commonly performed to treat chronic painful conditions, such as complex regional pain syndrome (CRPS) and postherpetic neuralgia. However, whether it is effective in reducing anesthesia and analgesia requirement during surgery (acute pain) is not known.

Materials and Methods

Sixty American Society of Anesthesiologists (ASA) physical status I and II patients with CRPS type II undergoing surgery for repair of brachial plexus injury were randomized (1:1) to receive SGB with either 10 mL of 0.5% bupivacaine (Group B) or a matching placebo (Group S) before induction of anesthesia.

Results

There was a significant reduction in the requirement of total intraoperative propofol (1659.7 ± 787.5 vs. 2500.7 ± 740.9 mg, P = 0.0003) and fentanyl (190.0 ± 82.5 vs. 327.3 ± 139.3, P = 0.0001) in Group B compared with Group S. Similarly, in Group B, the time to first analgesic was much longer (328 ± 219 vs. 64 ± 116 min, P = 0.000) and postoperative fentanyl requirement for 24 h was lesser compared to Group S (0.6 ± 1.1 vs. 2.1 ± 1.3 μg/kg, P = 0.000).

Conclusion

SGB is effective in reducing the requirement of intraoperative propofol and fentanyl as well as decreasing opioid requirement in the postoperative period in patients with CRPS type II undergoing surgery.

Regular dosing compared with as-needed dosing of opioids for management of chronic cancer pain: systematic review and meta-analysis

Opioids are the recommended form of analgesia for patients with persistent cancer pain, and regular dosing "by the clock" is advocated in many international guidelines on cancer pain management. The development of sustained-release opioid preparations has made regular dosing easier for patients. However, patients report that the intensity and impact of their cancer pain varies considerably day to day, and many try to find a trade-off between acceptable pain control and impact of cognitive (and other) adverse effects on daily activities. In acute care settings, (eg, postoperative) as-needed dosing and other opioid-sparing approaches have resulted in better patient outcomes compared with regular dosing. The aim of this study was to determine whether regular dosing of opioids was superior to as-needed dosing for persistent cancer pain. We systematically searched for randomised controlled trials that directly compared pain outcomes from regular dosing of opioids with as-needed dosing in adult cancer patients. We identified 4347 records, 25 randomised controlled trials meet the inclusion criteria, 9 were included in the review, and 7 of these included in meta-analysis. We found no clear evidence demonstrating superiority of regular dosing of opioids compared with as-needed dosing in persistent cancer pain, and regular dosing was associated with significantly higher total opioid doses. There was, however, a paucity of trials directly answering this question, and low-quality evidence limits the conclusions that can be drawn. It is clear that further high-quality clinical trials are needed to answer this question and to guide clinical practice.

Total Knee Arthroplasty: Opioid-Free Analgesia in a Patient with Opioid-Induced Hyperalgesia: A Case Report

CASE

Pain control after total knee arthroplasty (TKA) remains a significant challenge, especially in the context of certain patient-specific factors. We present a case of a 59-year-old woman with opioid-induced hyperalgesia who was referred for left knee pain and end-stage tricompartmental degenerative joint disease after failure of conservative management. We outline an approach to control postoperative pain in patients undergoing TKA who have severe opioid contraindications.

CONCLUSIONS

TKA and rehabilitation with a 6-year follow-up period was accomplished using a multimodal nonopioid approach, consisting of a combination of gabapentin, acetaminophen, ketorolac, meloxicam, methocarbamol, a tunneled femoral nerve catheter, and periarticular injection.

Does Opioid Tapering in Chronic Pain Patients Result in Improved Pain or Same Pain vs Increased Pain at Taper Completion? A Structured Evidence-Based Systematic Review

Objective

To support or refute the hypothesis that opioid tapering in chronic pain patients (CPPs) improves pain or maintains the same pain level by taper completion but does not increase pain.

Methods

Of 364 references, 20 fulfilled inclusion/exclusion criteria. These studies were type 3 and 4 (not controlled) but reported pre/post-taper pain levels. Characteristics of the studies were abstracted into tabular form for numerical analysis. Studies were rated independently by two reviewers for quality. The percentage of studies supporting the above hypothesis was determined.

Results

No studies had a rejection quality score. Combining all studies, 2,109 CPPs were tapered. Eighty percent of the studies reported that by taper completion pain had improved. Of these, 81.25% demonstrated this statistically. In 15% of the studies, pain was the same by taper completion. One study reported that by taper completion, 97% of the CPPs had improved or the same pain, but CPPs had worse pain in 3%. As such, 100% of the studies supported the hypothesis. Applying the Agency for Health Care Policy and Research Levels of Evidence Guidelines to this result produced an A consistency rating.

Conclusions

There is consistent type 3 and 4 study evidence that opioid tapering in CPPs reduces pain or maintains the same level of pain. However, these studies represented lower levels of evidence and were not designed to test the hypothesis, with the evidence being marginal in quality with large amounts of missing data. These results then primarily reveal the need for controlled studies (type 2) to address this hypothesis.

Withdrawal-associated injury site pain (WISP): a descriptive case series of an opioid cessation phenomenon

Supplemental Digital Content is Available in the Text.

This descriptive case series among adults documents that pain can return temporarily at healed, previously pain-free injury sites during acute opioid withdrawal.

Withdrawal pain can be a barrier to opioid cessation. Yet, little is known about old injury site pain in this context. We conducted an exploratory mixed-methods descriptive case series using a web-based survey and in-person interviews with adults recruited from pain and addiction treatment and research settings. We included individuals who self-reported a past significant injury that was healed and pain-free before the initiation of opioids, which then became temporarily painful upon opioid cessation—a phenomenon we have named withdrawal-associated injury site pain (WISP). Screening identified WISP in 47 people, of whom 34 (72%) completed the descriptive survey, including 21 who completed qualitative interviews. Recalled pain severity scores for WISP were typically high (median: 8/10; interquartile range [IQR]: 2), emotionally and physically aversive, and took approximately 2 weeks to resolve (median: 14; IQR: 24 days). Withdrawal-associated injury site pain intensity was typically slightly less than participants' original injury pain (median: 10/10; IQR: 3), and more painful than other generalized withdrawal symptoms which also lasted approximately 2 weeks (median: 13; IQR: 25 days). Fifteen surveyed participants (44%) reported returning to opioid use because of WISP in the past. Participants developed theories about the etiology of WISP, including that the pain is the brain's way of communicating a desire for opioids. This research represents the first known documentation that previously healed, and pain-free injury sites can temporarily become painful again during opioid withdrawal, an experience which may be a barrier to opioid cessation, and a contributor to opioid reinitiation.

The dark side of opioids in pain management: basic science explains clinical observation

Although there is no doubt about opioids' ability to relieve pain in the short term, it is not always clear why longer-term analgesic efficacy seems to be impaired. Tolerance and hyperalgesia have been suggested as mechanisms for opioid analgesic deterioration. But could there also be an effect of opioids on pain itself?

Introduction:

In the past 2 decades, opioids have been used increasingly for the treatment of persistent pain, and doses have tended to creep up. As basic science elucidates mechanisms of pain and analgesia, the cross talk between central pain and opioid actions becomes clearer.

Objectives:

We aimed to examine the published literature on basic science explaining pronociceptive opioid actions, and apply this knowledge to clinical observation.

Methods:

We reviewed the existing literature on the pronociceptive actions of opioids, both preclinical and clinical studies.

Results:

Basic science provides a rationale for the clinical observation that opioids sometimes increase rather than decrease pain. Central sensitization (hyperalgesia) underlies pain chronification, but can also be produced by high dose and high potency opioids. Many of the same mechanisms account for both central pain and opioid hyperalgesia.

Conclusion:

Newly revealed basic mechanisms suggest possible avenues for drug development and new drug therapies that could alter pain sensitization through endogenous and exogenous opioid mechanisms. Recent changes in practice such as the introduction of titration-to-effect for opioids have resulted in higher doses used in the clinic setting than ever seen previously. New basic science knowledge hints that these newer dosing practices may need to be reexamined. When pain worsens in a patient taking opioids, can we be assured that this is not because of the opioids, and can we alter this negative effect of opioids through different dosing strategies or new drug intervention?

Methadone as a Coanalgesic for Palliative Care Cancer Patients

BACKGROUND

Methadone offers many advantages for treating cancer pain. However, its pharmacokinetic profile makes its use as a full-dose opioid challenging.

OBJECTIVES

To evaluate the efficacy and safety of low-dose methadone as an adjunct to opioids in the treatment of cancer pain in palliative care patients.

DESIGN

A cohort was followed retrospectively for up to 60 days after the initiation of methadone as a coanalgesic.

SETTING/SUBJECTS

Patients were eligible if they were prescribed methadone as a coanalgesic for cancer pain management and followed by the palliative care team.

MEASUREMENTS

The primary efficacy end point was reduction of pain intensity (11-point numerical rating scale). Variables associated with pain intensity reduction were explored using logistic regressions. Adverse events were collected throughout the follow-up.

RESULTS

Seventy-two of the 146 subjects (49%) qualified as significant responders (≥30% reduction in pain intensity). Median time to significant response was seven days, and pain intensity on the day of methadone initiation predicted the response to treatment. The most frequently reported adverse events were drowsiness, confusion, constipation, and nausea. As expected in a palliative care population, there was a substantial amount of missing data.

CONCLUSIONS

A significant reduction in pain can be seen rapidly after the addition of methadone as a coanalgesic, particularly among patients with high pain intensity. More studies are needed to corroborate the efficacy of methadone as an adjunct to opioids.

Management of migraine headaches in a chronic pain patient: A case report

Managing migraines complicated with medication overuse headaches and opioid-induced hyperalgesia can be challenging, especially within the geriatric and chronic pain population. A 65-year-old woman with a degenerative spine condition and chronic migraine headaches, along with other comorbidities, was admitted to the geriatric psychiatry unit for extreme mood swings and paranoia. Prior to admission, she had been taking extended-release morphine sulfate twice daily for more than a month and was unable to determine triggers to her frequent migraine headaches. She had a history of medication overuse and severe migraine episodes within 4 weeks prior to admission. This case report reviews the challenges of treating a geriatric patient with probable chronic migraines in addition to other pain conditions and comorbidities.

Targeting Opioid-Induced Hyperalgesia in Clinical Treatment: Neurobiological Considerations

Opioid analgesics have become a cornerstone in the treatment of moderate to severe pain, resulting in a steady rise of opioid prescriptions. Subsequently, there has been a striking increase in the number of opioid-dependent individuals, opioid-related overdoses, and fatalities. Clinical use of opioids is further complicated by an increasingly deleterious profile of side effects beyond addiction, including tolerance and opioid-induced hyperalgesia (OIH), where OIH is defined as an increased sensitivity to already painful stimuli. This paradoxical state of increased nociception results from acute and long-term exposure to opioids, and appears to develop in a substantial subset of patients using opioids. Recently, there has been considerable interest in developing an efficacious treatment regimen for acute and chronic pain. However, there are currently no well-established treatments for OIH. Several substrates have emerged as potential modulators of OIH, including the N-methyl-D-aspartate and γ-aminobutyric acid receptors, and most notably, the innate neuroimmune system. This review summarizes the neurobiology of OIH in the context of clinical treatment; specifically, we review evidence for several pathways that show promise for the treatment of pain going forward, as prospective adjuvants to opioid analgesics. Overall, we suggest that this paradoxical state be considered an additional target of clinical treatment for chronic pain.

Opioid-induced hyperalgesia in chronic pain patients and the mitigating effects of gabapentin

Chronic pain patients receiving opioid drugs are at risk for opioid-induced hyperalgesia (OIH), wherein opioid pain medication leads to a paradoxical pain state. OIH involves central sensitization of primary and secondary afferent neurons in the dorsal horn and dorsal root ganglion, similar to neuropathic pain. Gabapentin, a gamma-aminobutyric acid (GABA) analog anticonvulsant used to treat neuropathic pain, has been shown in animal models to reduce fentanyl hyperalgesia without compromising analgesic effect. Chronic pain patients have also exhibited lower opioid consumption and improved pain response when given gabapentin. However, few human studies investigating gabapentin use in OIH have been performed in recent years. In this review, we discuss the potential mechanisms that underlie OIH and provide a critical overview of interventional therapeutic strategies, especially the clinically-successful drug gabapentin, which may reduce OIH.

Known unknowns: A review of opioid-induced hyperalgesia

Opioid-induced hyperalgesia (OIH) is a relatively new paradigm that has added to the already growing uncertainty surrounding long-term opioid treatment. OIH is the oversensitization to stimuli in the nervous system resulting from opioid exposure and subsequent neuroplastic changes. Because of its novelty and difficulty in identification, the true prevalence of OIH is unknown. Several mechanisms have been proposed for its development. These include changes in the N-methyl-D-aspartate system, descending pathway modulation, dynorphin activity, inflammatory changes mediated by cyclooxygenase, and increased sensitivity to excitatory neurochemicals. The clinical controversy regarding the management of OIH is due largely to the lack of guidance in diagnosis and lack of quality evidence to direct treatment. As a diagnosis of exclusion, several alternative causes of antianalgesia must be ruled out before OIH can be declared. Pharmacodynamic phenomena such as opioid tolerance share overlapping mechanisms with OIH and may present similarly. Pharmacokinetic changes such as drug-induced or disease-induced alterations to the cytochrome P450 or P-glycoprotein systems should also be excluded as causes of increased opioid demand that may be seen as OIH. Certain pharmacologic agents, such as N-methyl-D-aspartate receptor antagonists, alpha2 receptor agonists, and cyclooxygenase inhibitors, have been identified as possible treatments to reverse the effects of OIH. Opioid rotation and dose reductions have also been used with some degree of success. Pharmacist involvement in the identification and management of OIH will be central to success because of the unique expertise they offer. The quality of these studies is limited by study design, small sample sizes, and lack of generalizability to chronic pain patients with long-standing opioid use.

Opioid-induced hyperalgesia (OIH): a real clinical problem or just an experimental phenomenon?

Although opioid-induced hyperalgesia (OIH) is mentioned as a potential cause of opioid dose escalation without adequate analgesia, true evidence in support of this notion is relatively limited. Most studies conducted in the context of acute and experimental pain, which seemingly demonstrated evidence for OIH, actually might have measured other phenomena such as acute opioid withdrawal or tolerance. OIH studies in patients with chronic pain have used various experimental pain models (such as cold pain tolerance or heat pain intensity). Therefore, the fact that they have yielded inconsistent results is hard to interpret. Thus far, with the exception of a few clinical case reports on OIH in patients with cancer pain and one prospective study in patients with chronic neuropathic pain, evidence for OIH in patients with chronic or cancer-related pain is lacking. Whether experimental pain models are necessary for establishing the clinical diagnosis of OIH, and which specific model is preferred, are yet to be determined.

Increased pain sensitivity in chronic pain subjects on opioid therapy: a cross-sectional study using quantitative sensory testing

OBJECTIVE

The aim of this study was to compare the sensitivity to experimental pain of chronic pain patients on opioid therapy vs chronic pain patients on non-opioid therapy and healthy subjects by quantitative sensory testing (QST).

SETTING

There is a growing body of evidence demonstrating that chronic use of opioid drugs may alter pain sensitivity. Identifying the characteristic changes in thermal pain sensitivity in chronic opioid users will be helpful in diagnosing pain sensitivity alterations associated with chronic opioid use.

METHODS

Utilizing an office-based QST technique, we examined thermal pain threshold, tolerance, and temporal summation in 172 chronic pain subjects receiving opioid therapy, 121 chronic pain subjects receiving non-opioid therapy, and 129 healthy subjects.

RESULTS

In chronic pain subjects receiving opioid therapy, there were detectable differences in QST characteristics compared with both chronic pain subjects receiving non-opioid therapy and healthy subjects. Specifically, in chronic pain subjects receiving opioid therapy, 1) sensitivity to heat pain was increased; threshold to heat pain was significantly lower; 2) tolerance to supra-threshold heat pain was significantly decreased; and 3) temporal pain summation was exacerbated, as compared with chronic pain subjects receiving non-opioid therapy. In a subgroup of chronic pain subjects receiving opioid therapy with increased heat pain sensitivity, their average opioid medication dosage was significantly higher than those who had an above-average heat pain threshold. Moreover, a subset of chronic pain subjects on opioid therapy exhibited a significant decrease in diffuse noxious inhibitory control (DNIC) compared with chronic pain subjects on non-opioid therapy.

CONCLUSION

These findings suggest that a subset of QST parameters can reflect opioid-associated thermal pain sensitivity alteration, including decreased heat pain threshold, decreased cold and heat pain tolerance, diminished DNIC, and/or exacerbated temporal summation.

Toward a systematic approach to opioid rotation

Patients requiring chronic opioid therapy may not respond to or tolerate the first opioid prescribed to them, necessitating rotation to another opioid. They may also require dose increases for a number of reasons, including worsening disease and increased pain. Dose escalation to restore analgesia using the primary opioid may lead to increased adverse events. In these patients, rotation to a different opioid at a lower-than-equivalent dose may be sufficient to maintain adequate tolerability and analgesia. In published trials and case series, opioid rotation is performed either using a predetermined substitute opioid with fixed conversion methods, or in a manner that appears to be no more systematic than trial and error. In clinical practice, opioid rotation must be performed with consideration of individual patient characteristics, comorbidities (eg, concurrent psychiatric, pulmonary, renal, or hepatic illness), and concurrent medications, using flexible dosing protocols that take into account incomplete opioid cross-tolerance. References cited in this review were identified via a search of PubMed covering all English language publications up to May 21, 2013 pertaining to opioid rotation, excluding narrative reviews, letters, and expert opinion. The search yielded a total of 129 articles, 92 of which were judged to provide relevant information and subsequently included in this review. Through a review of this literature and from the authors’ empiric experience, this review provides practical information on performing opioid rotation in clinical practice.

The use of very-low-dose methadone for palliative pain control and the prevention of opioid hyperalgesia

BACKGROUND

Opioid dose escalation may cause hyperalgesia, mediated by the N-methyl-D-aspartate (NMDA) pathway. Methadone is an atypical opioid that inhibits hyperalgesia through NMDA-blockade, especially at low doses.

OBJECTIVE

To evaluate the efficacy of using very-low-dose methadone as the sole long-acting opioid agent in a hospice practice.

DESIGN

A retrospective, observational study of the use of methadone, ≤15 mg daily, with as-needed short-acting opiates. Adjuvant nonopioid medications included haloperidol, which may have NMDA-blocking effects.

SETTING/SUBJECTS

We reviewed the records of 240 patients admitted to a community-based hospice from July 1, 2011 to April 1, 2012, with data collected until hospice discharge or until April 30, 2012.

MEASUREMENTS

Descriptive statistics were used to summarize patient demographics, medication regimens, and reported pain scores measured on a numeric rating scale from 0 to 10.

RESULTS

All patients received short-acting opiates, in a morphine-equivalent dose of 5 mg every 4 hours as needed, while 40% also received methadone at a median daily dose of 5 mg. Of those on methadone, almost half received scheduled haloperidol. The population had a median reported pain score of 0 and a peak score of 3, with similar results seen for cancer and noncancer groups. Two-thirds of patients never reported a pain score greater than 3.

CONCLUSION

The use of very-low-dose methadone in conjunction with adjuvant haloperidol resulted in excellent pain control without dose escalation or opioid-induced hyperalgesia, for both cancer and noncancer diseases. We conclude that low-dose methadone should be part of first-line treatment in palliative pain management.

Medication-overuse headache and opioid-induced hyperalgesia: A review of mechanisms, a neuroimmune hypothesis and a novel approach to treatment

Introduction

Patients with chronic headache who consume large amounts of analgesics are often encountered in clinical practice. Excessive intake of analgesics is now considered to be a cause, rather than simply a consequence, of frequent headaches, and as such the diagnosis “medication-overuse headache” (MOH) has been formulated. Despite the prevalence and clinical impact of MOH, the pathophysiology behind this disorder remains unclear and specific mechanism-based treatment options are lacking.

Discussion

Although most acute headache treatments have been alleged to cause MOH, here we conclude from the literature that opioids are a particularly problematic drug class consistently associated with worsening headache. MOH may not be a single entity, as each class of drug implicated may cause MOH via a different mechanism. Recent evidence indicates that chronic opioid administration may exacerbate pain in the long term by activating toll-like receptor-4 on glial cells, resulting in a pro-inflammatory state that manifests clinically as increased pain. Thus, from the available evidence it seems opioid-overuse headache is a phenomenon similar to opioid-induced hyperalgesia, which derives from a cumulative interaction between central sensitisation, due to repeated activation of nociceptive pathways by recurrent headaches, and pain facilitation due to glial activation.

Conclusion

Treatment strategies directed at inhibiting glial activation may be of benefit alongside medication withdrawal in the management of MOH.

European Palliative Care Research collaborative pain guidelines. Central side-effects management: what is the evidence to support best practice in the management of sedation, cognitive impairment and myoclonus?

This is a systematic review examining the management of opioid-induced central side effects. It has been conducted as part of a larger European Palliative Care Research collaborative review into the use and role of opioids in cancer pain. The review process identified 26 studies that met the inclusion criteria. The overall quality of the data was low and the few recommendations that can be made are weak and require confirmatory studies. The main central side effects examined were sedation, cognitive failure, sleep disturbance and myoclonus. Overall there is limited evidence for the use of methylphenidate in counteracting opioid-induced sedation and cognitive disturbance. No clear recommendations can be made concerning other individual drugs for the management of any of the central side effects examined. Given the lack of available data from this review there need to be further prospective controlled trials to confirm or refute these findings.

Multi-mechanistic analgesia for opioid-induced hyperalgesia

WHAT IS KNOWN AND OBJECTIVE

The phenomenon of opioid-induced hyperalgesia (OIH), an increased sensitivity to pain attributed to the very opioid drugs administered to manage the pain, is well established in animal models, and there is concern that it also occurs in patients. Our objective is to briefly summarize the basic science and clinical evidence about OIH as background to consider the possible benefit of using a multi-mechanistic analgesic approach.

COMMENT

It is unclear how OIH occurs, or even why; presumably, it is part of an adaptive response. But development of OIH poses a serious treatment dilemma. OIH differs from tolerance, which also presents as reduced analgesic effect, in that tolerance is addressed by judicious and monitored increase in opioid dose, but OIH would be treated by a decrease in opioid dose. Therefore, it is important to avoid induction of OIH. Currently, it is not clear which patients are at greater risk of developing OIH, or which drugs are at greater risk of producing it.

WHAT IS NEW AND CONCLUSION

We suggest that multi-mechanistic analgesia, accomplished within either a single drug or a combination of drugs, is a logical approach that might result in a reduced development of OIH.

Opioid-induced hyperalgesia: clinically relevant or extraneous research phenomenon?

Opioids have become the unequivocal therapy of choice in treating many varieties of chronic pain. With the increased prescription of opioids, some unintended consequences have occurred. After prolonged opioid exposure, opioid-induced hyperalgesia (OIH), the paradoxical effect that opioid therapy may in fact enhance or aggravate preexisting pain, may occur. Over the past several decades, an increasing number of laboratory and clinical reports have suggested lowered pain thresholds and heightened atypical pain unrelated to the original perceived pain sensations as hallmarks of OIH. However, not all evidence supports the clinical importance of OIH, and some question whether the phenomenon exists at all. Here, we present a nonexhaustive, brief review of the recent literature. OIH will be reviewed in terms of preclinical and clinical evidence for and against its existence; recommendations for clinical evaluation and intervention also will be discussed.

Management of opioid medications in patients with chronic pain and risk of substance misuse

When prescribed appropriately and used as prescribed, opioid medications can safely and effectively treat pain. Best practices with respect to their use in chronic non-cancer-related pain (CNCP) are evolving. Opioids may be subject to misuse for a variety of purposes, including self-medication, use for reward, compulsive use because of addiction, and diversion for profit. Individuals with chronic pain and co-occurring substance use, mental health disorders, and other conditions may be at increased risk for misuse of prescribed opioids. Interdisciplinary pain management, the use of universal precautions in all patients, and special attention to the structure of care in those at higher risk for opioid misuse may improve outcomes in opioid treatment of CNCP. This article discusses evolving research and clinical literature related to the care of individuals with CNCP at a higher risk for opioid misuse.

Altered quantitative sensory testing outcome in subjects with opioid therapy

Preclinical studies have suggested that opioid exposure may induce a paradoxical decrease in the nociceptive threshold, commonly referred as opioid-induced hyperalgesia (OIH). While OIH may have implications in acute and chronic pain management, its clinical features remain unclear. Using an office-based quantitative sensory testing (QST) method, we compared pain threshold, pain tolerance, and the degree of temporal summation of the second pain in response to thermal stimulation among three groups of subjects: those with neither pain nor opioid therapy (group 1), with chronic pain but without opioid therapy (group 2), and with both chronic pain and opioid therapy (group 3). We also examined the possible correlation between QST responses to thermal stimulation and opioid dose, opioid treatment duration, opioid analgesic type, pain duration, or gender in group 3 subjects. As compared with both group 1 (n=41) and group 2 (n=41) subjects, group 3 subjects (n=58) displayed a decreased heat pain threshold and exacerbated temporal summation of the second pain to thermal stimulation. In contrast, there were no differences in cold or warm sensation among three groups. Among clinical factors, daily opioid dose consistently correlated with the decreased heat pain threshold and exacerbated temporal summation of the second pain in group 3 subjects. These results indicate that decreased heat pain threshold and exacerbated temporal summation of the second pain may be characteristic QST changes in subjects with opioid therapy. The data suggest that QST may be a useful tool in the clinical assessment of OIH.