Impact of opioid rescue medication for breakthrough pain on the efficacy and tolerability of long-acting opioids in patients with chronic non-malignant pain

Living with hidradenitis suppurativa: managing the pain

“extraordinarily debilitating. I can’t work, I can’t do school. I can’t function and....every day moving on with my life turns into the worst thing ever”. Only a hard-hearted clinician could read this quote from a woman living with Hidradenitis Suppurativa (HS) and not be moved. The qualitative study in this issue of pain experiences in HS reveals a disconnect between patients and practitioners and offers new insights that may help improve HS care.

Impact of rescue medication in placebo-controlled trials of pharmacotherapy for neuropathic pain and low back pain

ABSTRACT

Rescue medication (RM) consumption is commonly used as a secondary outcome in placebo-controlled trials of chronic pain, but its validity has yet to be established. If participants randomized to placebo take more RM than those randomized to an active drug, the difference in pain between the 2 groups may be reduced, potentially masking effects of the active drug. This study assessed proportional RM consumption in the placebo and active groups according to results of 42 randomized controlled trials of neuropathic pain (NeP), and 29 trials of low back pain, which were included in 2 systematic reviews and meta-analyses. Trial results were assessed based on effect size, statistical significance, and whether the drug was recommended as first-line treatment by the systematic reviews. In trials indicating effect of the investigational drug, RM consumption was generally higher in the placebo groups than in the active groups. In trials reporting a small or a medium effect size of the investigational drug, subjects receiving placebo consumed 17% to 30% more RM than subjects receiving active drug, potentially leading to underestimation of the effects of the investigational drugs. Few trials reported a large effect size. Differences in RM consumption between participants receiving placebo and those receiving active drug were seldom taken in account by the individual trials and not at all by the systemic reviews when making treatment recommendations for NeP or low back pain. Elaboration on analytical methods to assess treatment effects in chronic pain trials using RM is warranted.

Continuous Wound Infiltration with Local Anesthetic Is an Effective and Safe Postoperative Analgesic Strategy: A Meta-Analysis

Introduction

Postoperative pain management is an essential module for perioperative care, especially for enhanced recovery after surgery programs. Continuous wound infiltration (CWI) with local anesthetic may be a promising postoperative analgesic strategy. However, its analgesic efficacy and safety remain debatable.

Methods

Embase and PubMed databases were systematically searched for relevant randomized controlled trials (RCTs). RCTs assessing the analgesic efficacy and safety of CWI with local anesthetic for postoperative analgesia were selected. The outcomes contained pain scores during rest and mobilization, total opioid consumption, time to the first request of rescue analgesia, length of hospital stay, satisfaction with analgesia, time to return of bowel function, postoperative nausea and vomiting, total complication, wound infection, hypotension, and pruritus. The weighted mean difference and risk ratio were used to pool continuous and dichotomous variables, respectively.

Results

A total of 121 RCTs were included. CWI with local anesthetic reduced postoperative pain during rest and mobilization at different time points, increased satisfaction with analgesia, shortened recovery of bowel function, and reduced postoperative nausea and vomiting compared with the placebo group, especially for laparotomy surgery. There were no significant differences in these clinical outcomes compared to epidural and intravenous analgesia. CWI with local anesthetic reduced the total opioid consumption and hypotension risk and did not increase total complications, wound infection, or pruritus. CWI with local anesthetic had a better analgesic efficacy without increased side effects for sternotomy surgery. However, CWI with local anesthetic did not translate into favorable analgesic benefits in laparoscopic surgery.

Conclusion

CWI with local anesthetic is an effective postoperative analgesic strategy with good safety profiles in laparotomy and sternotomy surgery, and thus CWI with local anesthetic may be a promising analgesic option enhancing recovery after surgery programs for these surgeries.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40122-021-00241-4.

Continuous wound infiltration (CWI) with local anesthetic may be a promising postoperative analgesic strategy, but its effect remains debatable. We performed this meta-analysis based on 121 high-quality articles (RCTs) to evaluate the analgesic efficacy and safety of CWI with local anesthetic. We found that CWI with local anesthetic could reduce postoperative pain, increase satisfaction with analgesia, shorten recovery of bowel function, and reduce postoperative nausea and vomiting, especially for laparotomy surgery. However, CWI with local anesthetic did not show favorable analgesic benefits in laparoscopic surgery.

[Use of rapid-onset fentanyl preparations beyond indication : A random questionnaire survey among congress participants and pain physicians]

BACKGROUND

Despite publicised advice and warnings, there are only scant data on the non-indicated prescription of rapid-onset preparations of fentanyl (ROF) in non-cancer pain (NCP). Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation.

OBJECTIVE

Initiated by the Working Group Cancer Pain and supported by the German Pain Society, a random sample survey was conducted to assess the non-indicated use of ROF.

METHODS

The survey addressed attendees of pain conferences who were given the option to fill in the questionnaires outside the conference or online. Primary endpoints of the structured questionnaire were quantitative and qualitative items with regard to the prescription of ROF, while secondary endpoints were opioid-induced side effects.

RESULTS

Obtaining a response rate of 44% (132/300) and an additional 51 online questionnaires revealed that 165 (90%) respondents had knowledge of non-indicated prescriptions or were involved in these. Of these, 65% were clinicians and 17% worked in an outpatient capacity. In all, 22% were trained pain or palliative physicians. Approximately 1205 patients were assessed indirectly. The main causes for dispensing ROF included NCP entities such as back pain (44%), neuropathic pain (33%), head or facial pain (12%), and dyspnea (5%) in cancer pain or lack of break-through pain or basic medication (44%). Sedation (32%), nausea/vomiting (31%), constipation (16%) and insufficient analgesia (31%) were the mostly commonly reported adverse effects.

CONCLUSION

Despite the non-ambiguous indication for ROF, physicians often demonstrate inappropriate prescription behaviour. Iatrogenic misuse of ROF should be minimized. The rates of adverse effects of ROF seems to be in line with other opioids.

The granulopoietic cytokine granulocyte colony-stimulating factor (G-CSF) induces pain: analgesia by rutin

Rutin is a glycone form of the flavonol quercetin and it reduces inflammatory pain in animal models. Therapy with granulocyte colony-stimulating factor (G-CSF) is known by the pain caused as its main side effect. The effect of rutin and its mechanisms of action were evaluated in a model of hyperalgesia induced by G-CSF in mice. The mechanical hyperalgesia induced by G-CSF was reduced by treatment with rutin in a dose-dependent manner. Treatment with both rutin + morphine or rutin + indomethacin, at doses that are ineffectual per se, significantly reduced the pain caused by G-CSF. The nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-ATP-sensitive potassium channel (K_ATP) signaling pathway activation is one of the analgesic mechanisms of rutin. Rutin also reduced the pro-hyperalgesic and increased anti-hyperalgesic cytokine production induced by G-CSF. Furthermore, rutin inhibited the activation of the nuclear factor kappa-light-chain enhancer of activated B cells (NFκB), which might explain the inhibition of the cytokine production. Treatment with rutin upregulated the decreased mRNA expression of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) combined with enhancement of the mRNA expression of the Nrf2 downstream target heme oxygenase (HO-1). Intraperitoneal (i.p.) treatment with rutin did not alter the mobilization of neutrophils induced by G-CSF. The analgesia by rutin can be explained by: NO-cGMP-PKG-K_ATP channel signaling activation, inhibition of NFκB and triggering the Nrf2/HO-1 pathway. The present study demonstrates rutin as a promising pharmacological approach to treat the pain induced by G-CSF without impairing its primary therapeutic benefit of mobilizing hematopoietic progenitor cells into the blood.

The relationship between overactivity and opioid use in chronic pain: a 5-day observational study

With increasing concerns about the potential harm of long-term opioid therapy, there is a need for the development and implementation of alternative treatment strategies for patients with chronic pain who have been using opioids for a prolonged period of time. Based on the findings from a recent qualitative investigation that suggested there may be a bidirectional association between opioid reliance and habitual overactivity behaviour (activity engagement that significantly exacerbates pain), this study was designed to quantitatively investigate the association between opioid use and habitual overactivity over a 5-day period in a group of chronic pain patients. Participants provided a list of their prescribed pain medication, completed a self-report measure of habitual overactivity, and then commenced 5 days of data collection. Data collection required participants to wear an activity monitor and to complete a diary that detailed their daily activities and the time at which they took medication. Individuals reporting higher levels of habitual overactivity were more likely to be prescribed opioids. In addition, higher levels of habitual overactivity were associated with more frequent pro re nata ("as needed") opioid use over the 5 days, and with a discrepancy between the prescribed and actual oral morphine-equivalent daily dose, where more medication was taken than was prescribed. There was no predominant context for pro re nata use. The results of this study support the idea that habitual overactivity behaviour may play a role in the development of reliance on opioid medication and that such an association may provide a potential treatment target for opioid therapy rationalisation.

Identification of novel natural compound inhibitors for human complement component 5a receptor by homology modeling and virtual screening

Abstract

Neuropathic pain and inflammatory pain are two common types of pathological pain in human health problems. To date, normal painkillers are only partially effective in treating such pain, leading to a tremendous demand to develop new chemical entities to combat pain and inflammation. A promising pharmacological treatment is to control signal transduction via the inflammatory mediator-coupled receptor protein C5aR by finding antagonists to inhibit C5aR activation. Here, we report the first computational study on the identification of non-peptide natural compound inhibitors for C5aR by homology modeling and virtual screening. Our study revealed a novel natural compound inhibitor Acteoside with better docking scores than all four existing non-peptidic natural compounds. The MM-GBSA binding free energy calculations confirmed that Acteoside has a decrease of ~39 kcal/mol in the free energy of binding compared to the strongest binding reference compound. Main contributions to the higher affinity of Acteoside to C5aR are the exceptionally strong lipophilic interaction, enhanced electrostatics and hydrogen bond interactions. Detailed analysis on the physiochemical properties of Acteoside suggests further directions in lead optimization. Taken together, our study proposes that Acteoside is a potential lead molecule targeting the C5aR allosteric site and provides helpful information for further experimental studies.

Graphical Abstract

Quercetin reduces Ehrlich tumor-induced cancer pain in mice

Cancer pain directly affects the patient's quality of life. We have previously demonstrated that the subcutaneous administration of the mammary adenocarcinoma known as Ehrlich tumor induces pain in mice. Several studies have shown that the flavonoid quercetin presents important biological effects, including anti-inflammatory, antioxidant, analgesic, and antitumor activity. Therefore, the analgesic effect and mechanisms of quercetin were evaluated in Ehrlich tumor-induced cancer pain in mice. Intraperitoneal (i.p.) treatments with quercetin reduced Ehrlich tumor-induced mechanical and thermal hyperalgesia, but not paw thickness or histological alterations, indicating an analgesic effect without affecting tumor growth. Regarding the analgesic mechanisms of quercetin, it inhibited the production of hyperalgesic cytokines IL-1β and TNFα and decreased neutrophil recruitment (myeloperoxidase activity) and oxidative stress. Naloxone (opioid receptor antagonist) inhibited quercetin analgesia without interfering with neutrophil recruitment, cytokine production, and oxidative stress. Importantly, cotreatment with morphine and quercetin at doses that were ineffective as single treatment reduced the nociceptive responses. Concluding, quercetin reduces the Ehrlich tumor-induced cancer pain by reducing the production of hyperalgesic cytokines, neutrophil recruitment, and oxidative stress as well as by activating an opioid-dependent analgesic pathway and potentiation of morphine analgesia. Thus, quercetin treatment seems a suitable therapeutic approach for cancer pain that merits further investigation.

Granulocyte-colony stimulating factor (G-CSF)-induced mechanical hyperalgesia in mice: Role for peripheral TNFα, IL-1β and IL-10

Granulocyte-colony stimulating factor (G-CSF) is a therapeutic approach to increase peripheral neutrophil counts after anti-tumor therapies. Pain is the major side effect of G-CSF. Intraplantar administration of G-CSF in mice induces mechanical hyperalgesia. However, the peripheral mechanisms involved in this effect were not elucidated. Therefore, the participation of pronociceptive cytokines tumor necrosis factor (TNF) alpha (TNFα), interleukin (IL)-1 beta (IL-1β) and antinociceptive cytokine IL-10 in G-CSF-induced mechanical hyperalgesia in mice was investigated. G-CSF-induced mechanical hyperalgesia was inhibited by systemic and local treatment with etanercept and IL-1 receptor antagonist (IL-1ra) or TNF receptor 1 (TNFR1) deficiency and increased in IL-10 deficient mice. In agreement, G-CSF injection induced significant TNFα, IL-1β and IL-10 production in paw tissue. G-CSF-induced hyperalgesia was dose-dependently inhibited by thalidomide (5-45mg/kg) and pentoxifylline (0.5-13.5mg/kg), and treatment with these drugs inhibited G-CSF-induced TNFα, IL-1β and IL-10 production. The combined treatment with pentoxifylline or thalidomide with morphine, at doses that are ineffective as single treatment, diminished G-CSF-induced hyperalgesia through inhibiting cytokine production. Indomethacin also reduces G-CSF hyperalgesia alone or combined with pentoxifylline or thalidomide. Thus, G-CSF-induced hyperalgesia might be mediate by peripheral production of pronociceptive cytokines TNFα and IL-1β and down-regulated by IL-10. Systemic IL-1ra reduced G-CSF-induced increase of peripheral neutrophil counts. However, local treatment with morphine, IL-1ra or etanercept, and systemic treatment with indomethacin, etanercept, thalidomide and pentoxifylline did not alter G-CSF-induced mobilization of neutrophils. Therefore, this study advances in the understanding of G-CSF-induced hyperalgesia and suggests therapeutic approaches for its control.

Targeting the minor pocket of C5aR for the rational design of an oral allosteric inhibitor for inflammatory and neuropathic pain relief

Chronic pain resulting from inflammatory and neuropathic disorders causes considerable economic and social burden. Pharmacological therapies currently available for certain types of pain are only partially effective and may cause severe adverse side effects. The C5a anaphylatoxin acting on its cognate G protein-coupled receptor (GPCR), C5aR, is a potent pronociceptive mediator in several models of inflammatory and neuropathic pain. Although there has long been interest in the identification of C5aR inhibitors, their development has been complicated, as for many peptidomimetic drugs, mostly by poor drug-like properties. Herein, we report the de novo design of a potent and selective C5aR noncompetitive allosteric inhibitor, DF2593A, guided by the hypothesis that an allosteric site, the "minor pocket," previously characterized in CXC chemokine receptors-1 and -2, is functionally conserved in the GPCR class. In vitro, DF2593A potently inhibited C5a-induced migration of human and rodent neutrophils. In vivo, oral administration of DF2593A effectively reduced mechanical hyperalgesia in several models of acute and chronic inflammatory and neuropathic pain, without any apparent side effects. Mechanical hyperalgesia after spared nerve injury was also reduced in C5aR(-/-) mice compared with WT mice. Furthermore, treatment of C5aR(-/-) mice with DF2593A did not produce any further antinociceptive effect compared with C5aR(-/-) mice treated with vehicle. The successful medicinal chemistry strategy confirms that a conserved minor pocket is amenable for the rational design of selective inhibitors and the pharmacological results support that the allosteric blockade of the C5aR represents a highly promising therapeutic approach to control chronic inflammatory and neuropathic pain.

End-of-dose pain in chronic pain: does it vary with the use of different long-acting opioids?

A large percentage of patients with chronic pain on around-the-clock (ATC) opioids may experience increased pain occurring at the end of a scheduled dose, also known as end-of-dose pain. Despite the significant prevalence and impact of end-of-dose pain in patients using extended-release (ER) opioids, there are no detailed analyses examining how the frequency of end-of-dose pain is linked to the formulations of long-acting opioids. Consequently, we performed a systematic review to evaluate how many published studies on patients with chronic cancer or noncancer pain identified end-of-dose pain. As only a few studies mentioned end-of-dose pain explicitly, we used breakthrough pain (BTP) as a surrogate parameter. We determined if any opioid formulation had a greater association with the frequency of BTP, the use of rescue medication for BTP, and the frequency of end-of-dose pain. Of the 39 studies entered in the final analysis, 14 studies across different formulations showed that ER opioids were effective in the prevention of BTP. The opioids most frequently studied were hydromorphone (26%), followed by morphine (23%), and transdermal buprenorphine (23%). Only 5% of the studies used immediate-release preparations. Overall, most studies showed that patients using ER preparations experienced fewer episodes of BTP compared with patients on placebo or an active comparator. This could reflect the favorable duration of action of these opioids compared with short-acting formulations. Future studies should examine the incidence of end-of-dose pain and use of rescue medicine in a longitudinal manner in patients with chronic pain taking short- vs. long-acting ATC opioids.

The ruthenium NO donor, [Ru(bpy)2(NO)SO3](PF6), inhibits inflammatory pain: involvement of TRPV1 and cGMP/PKG/ATP-sensitive potassium channel signaling pathway

The activation of nitric oxide (NO) production is an analgesic mechanism shared by drugs such as morphine and diclofenac. Therefore, the controlled release of low amounts of NO seems to be a promising analgesic approach. In the present study, the antinociceptive effect of the ruthenium NO donor [Ru(bpy)2(NO)SO3](PF6) (complex I) was investigated. It was observed that complex I inhibited in a dose (0.3-10mg/kg)-dependent manner the acetic acid-induced writhing response. At the dose of 1mg/kg, complex I inhibited the phenyl-p-benzoquinone-induced writhing response and formalin- and complete Freund's adjuvant-induced licking and flinch responses. Additionally, complex I also inhibited transient receptor potential cation channel subfamily V member 1 (TRPV1)-dependent overt pain-like behavior induced by capsaicin. Complex I also inhibited the carrageenin-induced mechanical hyperalgesia and increase of myeloperoxidase activity (MPO) in paw skin samples. The inhibitory effect of complex I in the carrageenin-induced hyperalgesia, MPO activity and formalin was prevented by the treatment with ODQ, KT5823 and glybenclamide, indicating that complex I inhibits inflammatory hyperalgesia by activating the cGMP/PKG/ATP-sensitive potassium channel signaling pathway. The present study demonstrates the efficacy of a novel ruthenium NO donor and its analgesic mechanisms.

A physician-driven solution--the Association for Medical Ethics, the Physician Payment Sunshine Act, and ethical challenges in pain medicine

The practice of contemporary pain medicine is laced with a number of significant ethical challenges. Considerable difficulties include the overutilization of interventional procedures, the application of under-evidenced treatment modalities, and potentially superfluous opioid prescribing. As with many other fields in medicine, including orthopedic surgery, relationships with industry are both common and pervasive, and influence our medical practice through education, publications, and research. This article highlights these ethical challenges and broaches several physician-driven solutions: The Association for Medical Ethics, the Physicians Payment Sunshine inspired by it, and other non-legislative reforms are discussed.

Perioperative management of the child on long-term opioids

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

Granulocyte-colony stimulating factor (G-CSF) induces mechanical hyperalgesia via spinal activation of MAP kinases and PI3K in mice

Granulocyte-colony stimulating factor (G-CSF) is a current pharmacological approach to increase peripheral neutrophil counts after anti-tumor therapies. Pain is most relevant side effect of G-CSF in healthy volunteers and cancer patients. Therefore, the mechanisms of G-CSF-induced hyperalgesia were investigated focusing on the role of spinal mitogen-activated protein (MAP) kinases ERK (extracellular signal-regulated kinase), JNK (Jun N-terminal Kinase) and p38, and PI(3)K (phosphatidylinositol 3-kinase). G-CSF induced dose (30-300 ng/paw)-dependent mechanical hyperalgesia, which was inhibited by local post-treatment with morphine. This effect of morphine was reversed by naloxone (opioid receptor antagonist). Furthermore, G-CSF-induced hyperalgesia was inhibited in a dose-dependent manner by intrathecal pre-treatment with ERK (PD98059), JNK (SB600125), p38 (SB202190) or PI(3)K (wortmanin) inhibitors. The co-treatment with MAP kinase and PI(3)K inhibitors, at doses that were ineffective as single treatment, significantly inhibited G-CSF-induced hyperalgesia. Concluding, in addition to systemic opioids, peripheral opioids as well as spinal treatment with MAP kinases and PI(3)K inhibitors also reduce G-CSF-induced pain.

[Physicians' knowledge and attitudes concerning the use of opioids in the treatment of chronic cancer and non-cancer pain]

INTRODUCTION

The efficacy of opioids has been proved and several guidelines and expert panel-based recommendations regarding the use of opioids in different pain syndromes are available. Nevertheless, undertreatment of pain with strong opioids was reported in previous studies. It was shown that physicians' lack of knowledge, their concerns and misconceptions about the opioid use and the controlled substances regulations that govern the prescriptions of opioids occasionally contribute to insufficient pain treatment. This study was designed to evaluate German physicians' knowledge and their concerns about the use of opioids.

METHOD

During a postgraduate course a questionnaire was completed by German physicians specializing in pain therapy.

RESULTS

A total of 226 physicians completed the questionnaire (response rate 57%). Many of them had poor knowledge of the WHO recommendations for the treatment of cancer pain including the WHO analgesic ladder. Deficiencies in the knowledge of pharmacological aspects and controlled substances regulations were revealed. Many physicians would prescribe strong opioids for non-opioid-sensitive types of pain. The concerns regarding opioid therapy included adverse effects and addiction. In contrast to earlier findings the German controlled substances regulations no longer seem to be a barrier to the prescription of opioids in the treatment of chronic severe pain since they were changed in 1998. As a result, the lack of knowledge and the physicians' concerns about the use of opioids as shown in this survey may likely lead to an insufficient treatment of patients suffering from severe chronic pain.

CONCLUSION

It is necessary to improve the medical students' education and the physicians' postgraduate training regarding principles of pain management such as the WHO guidelines for the treatment of cancer pain. A better knowledge of important pharmacological aspects of opioids should help to reduce physicians' concerns about the use of strong opioids. Nevertheless, improvement of physicians' skills in pain therapy is only one aim in a multidisciplinary concept in order to improve patients' pain therapy.