Opioid and adjuvant analgesics: compared and contrasted

Delta-9-tetrahydrocannabinol modulates pain sensitivity among persons receiving opioid agonist therapy for opioid use disorder: A within-subject, randomized, placebo-controlled laboratory study

The opioid and cannabinoid receptor systems are inextricably linked-overlapping at the anatomical, functional and behavioural levels. Preclinical studies have reported that cannabinoid and opioid agonists produce synergistic antinociceptive effects. Still, there are no experimental data on the effects of cannabinoid agonists among humans who receive opioid agonist therapies for opioid use disorder (OUD). We conducted an experimental study to investigate the acute effects of the delta-9-tetrahydrocannabinol (THC) among persons receiving methadone therapy for OUD. Using a within-subject, crossover, human laboratory design, 25 persons on methadone therapy for OUD (24% women) were randomly assigned to receive single oral doses of THC (10 or 20 mg, administered as dronabinol) or placebo, during three separate 5-h test sessions. Measures of experimental and self-reported pain sensitivity, abuse potential, cognitive performance and physiological effects were collected. Mixed-effects models examined the main effects of THC dose and interactions between THC (10 and 20 mg) and methadone doses (low-dose methadone defined as <90 mg/day; high dose defined as >90 mg/day). Results demonstrated that, for self-reported rather than experimental pain sensitivity measures, 10 mg THC provided greater relief than 20 mg THC, with no substantial evidence of abuse potential, and inconsistent dose-dependent cognitive adverse effects. There was no indication of any interaction between THC and methadone doses. Collectively, these results provide valuable insights for future studies aiming to evaluate the risk-benefit profile of cannabinoids to relieve pain among individuals receiving opioid agonist therapy for OUD, a timely endeavour amidst the opioid crisis.

Pharmacological Methods of Pain Management: Narrative Review of Medication Used

Background

Pain management is a critical aspect of healthcare, aimed at alleviating discomfort and improving the quality of life for individuals experiencing acute or chronic pain. Pharmacological methods constitute a primary approach to pain management, including a diverse array of drugs that work through different mechanisms.

Aim

Identifying medications commonly employed in pain management, focusing on their mechanism of actions, uses, efficacy and pharmacological applications.

Methods

The methodology involved a systematic search of scientific literature using various databases, including PubMed, Scopus, and Google Scholar. Relevant articles published between 2000 and 2023 were screened for inclusion. The selected studies encompassed original research, review articles, therapeutic guidelines and randomized controlled trials.

Results

The findings of this review suggest that a multimodal approach combining various analgesics can enhance pain relief while minimizing adverse effects. It emphasizes the importance of assessing pain intensity, determining the underlying etiology, and utilizing evidence-based guidelines to optimize pain management outcomes.

Conclusion

Pharmacological methods of pain management are an essential component of pain management strategies to achieve optimal pain relief while minimizing adverse effects. The article concludes with a discussion on emerging trends and future directions in pharmacological pain management, including novel drug targets and advances in drug delivery systems.

Personalized Medicine in Cancer Pain Management

BACKGROUND

Previous studies have documented pain as an important concern for quality of life (QoL) and one of the most challenging manifestations for cancer patients. Thus, cancer pain management (CPM) plays a key role in treating pain related to cancer. The aim of this systematic review was to investigate CPM, with an emphasis on personalized medicine, and introduce new pharmacogenomics-based procedures for detecting and treating cancer pain patients.

METHODS

This study systematically reviewed PubMed from 1990 to 2023 using keywords such as cancer, pain, and personalized medicine. A total of 597 publications were found, and after multiple filtering processes, 75 papers were included. In silico analyses were performed using the GeneCards, STRING-MODEL, miRTargetLink2, and PharmGKB databases.

RESULTS

The results reveal that recent reports have mainly focused on personalized medicine strategies for CPM, and pharmacogenomics-based data are rapidly being introduced. The literature review of the 75 highly relevant publications, combined with the bioinformatics results, identified a list of 57 evidence-based genes as the primary gene list for further personalized medicine approaches. The most frequently mentioned genes were CYP2D6, COMT, and OPRM1. Moreover, among the 127 variants identified through both the literature review and data mining in the PharmGKB database, 21 variants remain as potential candidates for whole-exome sequencing (WES) analysis. Interestingly, hsa-miR-34a-5p and hsa-miR-146a-5p were suggested as putative circulating biomarkers for cancer pain prognosis and diagnosis.

CONCLUSIONS

In conclusion, this study highlights personalized medicine as the most promising strategy in CPM, utilizing pharmacogenomics-based approaches to alleviate cancer pain.

Pharmacogenetic Guided Opioid Therapy Improves Chronic Pain Outcomes and Comorbid Mental Health: A Randomized, Double-Blind, Controlled Study

Interindividual variability in analgesic response is at least partly due to well-characterized polymorphisms that are associated with opioid dosing and adverse outcomes. The Clinical Pharmacogenetics Implementation Consortium (CPIC) has put forward recommendations for the CYP2D6 phenotype, but the list of studied drug-gene pairs continues to grow. This clinical trial randomized chronic pain patients (n = 60), referred from primary care to pain unit care into two opioid prescribing arms, one guided by CYP2D6, μ-opioid receptor (OPRM1), and catechol-O-methyl transferase (COMT) genotypes vs. one with clinical routine. The genotype-guided treatment reduced pain intensity (76 vs. 59 mm, p < 0.01) by improving pain relief (28 vs. 48 mm, p < 0.05), increased quality of life (43 vs. 56 mm p < 0.001), and lowered the incidence of clinically relevant adverse events (3 [1-5] vs. 1 [0-2], p < 0.01) and 42% opioid dose (35 [22-61] vs. 60 [40-80] mg/day, p < 0.05) as opposed to usual prescribing arm. The final health utility score was significantly higher (0.71 [0.58-0.82] vs. 0.51 [0.13-0.67] controls, p < 0.05) by improving sleepiness and depression comorbidity, with a significant reduction of 30-34% for headache, dry mouth, nervousness, and constipation. A large-scale implementation analysis could help clinical translation, together with a pharmaco-economic evaluation.

Potential Roles of 5-HT3 Receptor Antagonists in Reducing Chemotherapy-induced Peripheral Neuropathy (CIPN)

5-HT₃ receptor antagonists corresponding to ondansetron, granisetron, tropisetron, and palonosetron are clinically accustomed to treating nausea and emesis in chemotherapy patients. However, current and previous studies reveal novel potentials of those ligands in other diseases involving the nervous system, such as addiction, pruritus, and neurological disorders, such as anxiety, psychosis, nociception, and cognitive function. This review gathers existing studies to support the role of 5-HT₃ receptors in CIPN modulation. It has been reported that chemotherapy drugs increase the 5-HT content that binds with the 5-HT₃ receptor, which later induces pain. As also shown in pre-clinical and clinical studies that various neuropathic pains could be blocked by the 5-HT₃ receptor antagonists, we proposed that 5-HT₃ receptor antagonists via 5- HT₃ receptors may also inhibit neuropathic pain induced by chemotherapy. Our review suggests that future studies focus more on the 5-HT₃ receptor antagonists and their modulation in CIPN to reduce the gap in the current pharmacotherapy for cancer-related pain.

Approach to Cancer Pain Management in Emergency Departments: Comparison of General and Oncology Based Settings

Cancer-related pain constitutes a dominant reason for admission to emergency services, and a significant patient and healthcare challenge. Evidence points to the rising prevalence of opioid misuse in this patient group. We sought to compare drug delivery in an oncology-dedicated emergency department (OED) and a general emergency department (GED) within the same hospital. As such, we obtained patient and drug-related data for OED and GED during a designated three-month period, and compared them using Fisher’s exact test, chi-square tests and the Mann-Whitney test. In total, 584 patients had 922 visits to emergency services (OED n = 479; GED n = 443), and were given 1478 drugs (OED n = 557; GED n = 921). Pain was a prominent chief complaint among visitors to the OED (17%) and GED (21%). Approximately a fifth of all drugs used were analgesics (OED—18.5%; GED—20.4%), however, in the GED, 51.6% (n = 97) were used for non-pain-related admissions, compared with 33.0% (n = 34) in OED. Opioid usage significantly differed between emergency settings. The GED administered three times as many intravenous opioids (p <0.001), a narrower spectrum of oral and intravenous drugs (p = 0.003) and no rapid-acting opioids, significantly fewer pain adjuvants (10.9% versus 18.7%, p < 0.001), and, finally, non-guideline-recommended drugs for pain, such as meperidine and benzodiazepines. Taken together, compared with the GED, the management of cancer-related pain in the OED was more personalized, and characterized by fewer intravenous opioids, enhanced diversity in drug type, route and method of delivery. Efforts should be directed toward reduction of disparities in the treatment of cancer pain in emergency settings.

CYP2D6 phenotypes and opioid metabolism: the path to personalized analgesia

INTRODUCTION

Opioids play a fundamental role in chronic pain, especially considering when 1 of 5 Europeans adults, even more in older females, suffer from it. However, half of them do not reach an adequate pain relief. Could pharmacogenomics help to choose the most appropriate analgesic drug?

AREAS COVERED

The objective of the present narrative review was to assess the influence of cytochrome P450 2D6 (CYP2D6) phenotypes on pain relief, analgesic tolerability, and potential opioid misuse. Until December 2021, a literature search was conducted through the MEDLINE, PubMed database, including papers from the last 10 years. CYP2D6 plays a major role in metabolism that directly impacts on opioid (tramadol, codeine, or oxycodone) concentration with differences between sexes, with a female trend toward poorer pain control. In fact, CYP2D6 gene variants are the most actionable to be translated into clinical practice according to regulatory drug agencies and international guidelines.

EXPERT OPINION

CYP2D6 genotype can influence opioids' pharmacokinetics, effectiveness, side effects, and average opioid dose. This knowledge needs to be incorporated in pain management. Environmental factors, psychological together with genetic factors, under a sex perspective, must be considered when you are selecting the most personalized pain therapy for your patients.

A Comparison of Tertiary Drug Resources' Consistency Regarding Drug-Drug Interactions of Adjunctive Analgesics

Background: Health care providers routinely rely on tertiary drug information resources to affirm knowledge or proactively verify the safety and efficacy of medications. Though all patient care areas are affected, the reliability of these resources is perhaps nowhere as poignant as it is in high-acuity settings, including the emergency department and the intensive care unit. As providers seek to identify adjunctive analgesics for acute pain in these areas, they must be able to rely on the integrity to whichever resource their institution has granted access. Objective: To determine the congruency of drug-drug interaction information found on 3 tertiary drug resources. Methods: A drug-drug interaction analysis was conducted on Micromedex, Lexicomp, and Medscape. Adjunctive analgesics included dexmedetomidine and ketamine, which were compared with the intravenous opioid products morphine, fentanyl, and hydromorphone. Results: Significant discrepancies were appreciated with regard to the severity of drug-drug interactions. In addition, the heterogeneity in which reaction severity and likelihood are described by each respective resource makes direct comparisons difficult. Interaction warnings for dexmedetomidine and fentanyl included a "major interaction" from Micromedex, whereas Lexicomp did not identify a risk and Medscape only recommended increased monitoring on the grounds of respiratory and central nervous system depression. Conclusions: Health care providers must remain vigilant when reviewing tertiary drug information resources. Pharmacists possess the training and skills necessary to assist interdisciplinary medical teams in providing optimal patient care through evaluating and applying the information gleaned from these resources.

Pharmacologic Stepwise Multimodal Approach for Postpartum Pain Management: ACOG Clinical Consensus No. 1

SUMMARY

Pain in the postpartum period is common and considered by many individuals to be both problematic and persistent (1). Pain can interfere with individuals' ability to care for themselves and their infants, and untreated pain is associated with risk of greater opioid use, postpartum depression, and development of persistent pain (2). Clinicians should therefore be skilled in individualized management of postpartum pain. Though no formal time-based definition of postpartum pain exists, the recommendations presented here provide a framework for management of acute perineal, uterine, and incisional pain. This Clinical Consensus document was developed using an a priori protocol in conjunction with the authors listed. This document has been revised to incorporate more recent evidence regarding postpartum pain.

Assessment of safety and effectiveness of oral morphine on patients attending pain and palliative care: a study on Indian population

Opioid analgesics remain the corner stone of effective management of moderate to severe pain. Morphine in its oral and parenteral form is one of the most affordable options left to treat severe cancer pain in most Palliative centres in India. The main objective of our study was to assess the safety and effectiveness, as well as the prescribing pattern of immediate release oral morphine on the Indian population attending Pain and Palliative Care in a multi-speciality hospital. Within the sample population, 74.8% of all patients achieved a pain score reduction of less than or equal to 3 within the 72nd hour. Although the mean baseline pain score was similar in the cancer (8.23±0.75) and the non-cancer (8.26±0.98) group, the mean pain score at the 24th and 72nd hours were significantly different (5.6±1.29 in cancer and 5.09±1.26 in the non-cancer group within the 24th hour, followed by 3.66±1.479 and 3.12±0.88 after the 72nd hour, respectively). The majority of the patients (58.3%) were prescribed at a frequency of 5 mg every 4th hourly, with double dose at bedtime. A similar prescribing trend was seen in both the cancer and non-cancer groups. Moreover, 14 patients underwent dose escalation – with 12 belonging to the cancer group, while 11 patients falling under the cancer group required a switch to different therapy. The major adverse drug reactions (ADR) observed in both study groups were constipation (89.2%), fatigue (37.4%), dry mouth (36%) and nausea/vomiting (23%). The severity of nausea/vomiting and sleepiness was higher in the cancer group whereas itching was more predominant among the non-cancer group.

Implementation of a Standardized Post-Cesarean Delivery Order Set with Multimodal Combination Analgesia Reduces Inpatient Opioid Usage

Background: Opioid use has emerged as a leading cause of death in the US. Given that 1 in 300 opioid-naive patients exposed to opioids after cesarean birth will become persistent users, hospitals should strive to limit exposure to these medications. We set out to evaluate whether transitioning to a standardized order set based on multimodal combination analgesic therapy decreases the exposure to opioids after cesarean delivery. Methods: Our health system’s post-cesarean pain management electronic medical record (EMR) order set was changed from standing NSAIDs (Ibuprofen 600 mg every 6 h) and additional acetaminophen and opioid medications (Oxycodone 5 mg/acetaminophen 325 mg every 3 h or Oxycodone 10 mg/acetaminophen 650 mg every 6 h for moderate and severe pain, respectively) as needed (PRN) to a multimodal combination therapy with acetaminophen (975 mg every 6 h) and NSAIDs (Ibuprofen 600 mg every 6 h) as primary analgesics and opioids PRN (Oxycodone immediate release (IR) 5 mg every 3 h for moderate to severe pain). We performed a retrospective analysis across seven hospitals comparing inpatient opioid use, administration of other analgesics, and severe pain episodes (pain score ≥ 7) between the patients who were treated before and after implementation of the multimodal order set. Chi square and Student t-test were used for statistical analysis with significance determined as p < 0.05. Results: A total of 12,898 cesarean births were included (8696 prior and 4202 after implementation). The multimodal order set was associated with marked decrease in the incidence of post cesarean opioid use (45.4% vs. 67.5%; p < 0.0001), lower average opioid dose (26.7 mg vs. 36.6 mg of oxycodone; p < 0.0001), and increased dose of acetaminophen (8422 mg vs. 4563 mg; p < 0.0001), while severe pain scores were less frequent (46.3% vs. 56.6%, p < 0.0001). Conclusions: Multimodal analgesic therapy for post-cesarean pain management reduces inpatient opioid use while improving pain control. Incorporation of a multimodal order set as a default in the EMR facilitates effective and widespread implementation on a large scale. Obstetric units should consider standardizing post-cesarean pain management orders to include routine (not PRN) multimodal combination therapy with acetaminophen and NSAIDs as primary analgesics.

Multifunctional Opioid-Derived Hybrids in Neuropathic Pain: Preclinical Evidence, Ideas and Challenges

When the first- and second-line therapeutics used to treat neuropathic pain (NP) fail to induce efficient analgesia—which is estimated to relate to more than half of the patients—opioid drugs are prescribed. Still, the pathological changes following the nerve tissue injury, i.a. pronociceptive neuropeptide systems activation, oppose the analgesic effects of opiates, enforcing the use of relatively high therapeutic doses in order to obtain satisfying pain relief. In parallel, the repeated use of opioid agonists is associated with burdensome adverse effects due to compensatory mechanisms that arise thereafter. Rational design of hybrid drugs, in which opioid ligands are combined with other pharmacophores that block the antiopioid action of pronociceptive systems, delivers the opportunity to ameliorate the NP-oriented opioid treatment via addressing neuropathological mechanisms shared both by NP and repeated exposition to opioids. Therewith, the new dually acting drugs, tailored for the specificity of NP, can gain in efficacy under nerve injury conditions and have an improved safety profile as compared to selective opioid agonists. The current review presents the latest ideas on opioid-comprising hybrid drugs designed to treat painful neuropathy, with focus on their biological action, as well as limitations and challenges related to this therapeutic approach.

Postoperative Pain Management of Non-"Opioid-Naive" Patients Undergoing Hand and Upper-Extremity Surgery

Background: Patients with prior opioid use are often difficult to manage postoperatively. We examined potential strategies for managing these patients: (1) prescribing a different opioid; and (2) encouraging the use of nonopioid analgesics over opioids. Methods: A pain control program was implemented at an outpatient hand and upper-extremity center. Patients were recruited before (n = 305) and after (n = 225) implementation. Seventy of them were taking opioids prior to surgery. Information about pain control satisfaction and opioid use was collected. The Fisher exact test was used to compare categorical variables with small expected frequencies. Wilcoxon rank sum test was used to compare nonnormally distributed continuous variables. Results: Opioid users used 28.8 ± 25.6 opioid pills; nonopioid users used 14.5 ± 21.5 pills. Furthermore, 41.4% of opioid users sought more pills after surgery compared with 14.0% among nonopioid users. The pain control program was more effective in reducing opioid consumption and waste and increasing nonopioid consumption for nonopioid users than for opioid users. Prior opioid users who were prescribed a different opioid after surgery used 24.6 ± 22.0 opioid pills. Patients prescribed the same opioid used 37.9 ± 30.8 pills. Conclusions: Patients taking opioids prior to hand and upper-extremity surgery use more opioid pills, seek more pills after surgery, and are less satisfied with their pain control than their nonopioid user counterparts. Furthermore, the comprehensive pain plan was less effective in this patient population. Prescribing a different opioid reduced medication requirements for these patients, but additional strategies are needed to address postoperative pain management.

Soluble epoxide hydrolase inhibitor mediated analgesia lacks tolerance in rat models

Effectively treating chronic pain remains a therapeutic challenge in the clinic. Recent evidence has shown the inhibition of the soluble epoxide hydrolase (sEH) to be an effective strategy to limit chronic pain in preclinical models, horses and companion animals. Determining the safety of sEH inhibition in addition to this demonstrated efficacy is a critical step to the further development of sEH inhibitors (sEHI) as analgesics. Here we describe a comparison of the sEHI TPPU with other first in class analgesics for human chronic pain. We assess the development of tolerance to the analgesia mediated by TPPU with extended use. We also assess for CNS effects by measuring changes in motor control and functioning. The sEHI are multimodal analgesics that have demonstrated potent efficacy against chronic pain. They have previously been tested and show no reward potential using operant methods. The results of the current experiments show that they lack motor function effects and also lack the development of tolerance with extended dosing.

Factors Associated with Improvement in Uncontrolled Cancer Pain without Increasing the Opioid Daily Dose among Patients Seen by an Inpatient Palliative Care Team

Background: Increasing the total opioid dose is the standard approach for managing uncontrolled cancer pain. Other than simply increasing the opioid dose, palliative care interventions are multidimensional and may improve pain control in the absence of opioid dose increase. Objective: The purpose of this study was to determine the proportion of patients referred to our inpatient palliative care (IPC) team who achieved clinically improved pain (CIP) without opioid dose increase. Design: We reviewed consecutive patients referred to our IPC team. Setting/Subjects: Eligibility criteria included (1) taking opioid medication; (2) having ≥2 consecutive visits with the IPC team; and (3) an Edmonton Symptom Assessment Scale (ESAS) pain score ≥4 at consultation. Measurements: We assessed patient demographics and clinical variables, including cancer type, opioid prescription data (type, route, and oral morphine equivalent daily dose [MEDD]), presence of opioid rotation, psychological consultation, changes in adjuvant medications (e.g., corticosteroids; antiepileptics-gabapentin and pregabalin; benzodiazepines; and neuroleptics), and achievement of CIP. Results: Of the 300 patients enrolled, CIP was achieved in 196 (65%) patients. Of CIP patients, 85 (43%) achieved CIP without an increase in MEDD. CIP without MEDD increase was associated with more adjuvant medication changes (p = 0.003), less opioid rotation (p = 0.005), and lower symptom distress scale of ESAS (p = 0.04). Conclusions: Nearly half of the patients achieved CIP without MEDD increase, suggesting that the multidimensional palliative care intervention is effective in improving pain control in many opioid-tolerant patients without the need to increase the opioid dose.

Cannabinoid modulation of opioid analgesia and subjective drug effects in healthy humans

RATIONALE

Dozens of preclinical studies have reported cannabinoid agonist potentiation of the analgesic effects of μ-opioid agonists.

OBJECTIVES

The aim of this study was to determine if a cannabinoid agonist could potentiate opioid analgesia in humans using several laboratory pain models.

METHODS

Healthy participants (n = 10) with/out current drug use/pain conditions completed this within-subject, double-blind, placebo-controlled, randomized outpatient study. Nine 8-h sessions were completed during which dronabinol (0, 2.5, 5 mg, p.o.) was administered 1 h before oxycodone (0, 5, 10 mg, p.o.) for a total of 9 test conditions. Outcomes included sensory threshold and tolerance from four experimental pain models (cold pressor, pressure algometer, hot thermode, cold hyperalgesia), along with participant- and observer-rated, performance and physiological effects.

RESULTS

Oxycodone produced miosis (p < 0.05) and analgesic responses (e.g., pressure algometer [p < 0.05]), while dronabinol did not (p > 0.05). Depending on the dose combination, dronabinol attenuated or did not alter oxycodone analgesia; for example, dronabinol (2.5 mg) decreased the analgesic effects of oxycodone (10 mg) on pressure tolerance. Conversely, dronabinol increased oxycodone subjective effects (e.g., drug liking) (p < 0.05); oxycodone (5 mg) ratings of "high" were potentiated by 5 mg dronabinol (p < 0.05; placebo = 1.1 [± 0.7]; 5 mg oxycodone = 4.7 [± 2.2]; 5 mg dronabinol = 9.9 [± 8.4]; 5 mg oxycodone + 5 mg dronabinol = 37.4 [± 11.3]).

CONCLUSIONS

This study indicates that dronabinol did not enhance the analgesic effects of oxycodone and increased abuse- and impairment-related subjective effects. These data suggest that dronabinol may not be an effective or appropriate opioid adjuvant; it could potentially increase opioid dose requirements, while increasing psychoactive opioid effects.

Sex-specific and Age-specific Analgesia for Early Postoperative Pain Management After Lumbar Decompressive Surgery: A Randomized Clinical Trial

STUDY DESIGN

This was a randomized clinical trial.

OBJECTIVE

To compare the efficacy and safety of nonsteroidal anti-inflammatory drug and opioid for acute pain management after lumbar decompressive surgery.

SUMMARY OF BACKGROUND DATA

Multimodal analgesia is associated with synergistic effects while reducing opioid-related adverse effects. However, there is no consensus on the ideal multimodal analgesic regimen. We assumed that each agent in various multimodal regimens under different conditions may have different effects.

MATERIALS AND METHODS

This prospective randomized clinical trial recruited adult patients who underwent single-level lumbar decompressive surgery. Patients were randomized to receive our postoperative analgesic regimen including either nonsteroidal anti-inflammatory drug (celecoxib) or opioid (extended-release oxycodone) from postoperative day 3 to 14. The Visual Analog Scale (VAS) and Oswestry Back Pain Disability Index (ODI) were used to evaluate effectiveness preoperatively and on postoperative days 2, 3, 7, and 14, and at 6 months. Drug-related adverse effects were also recorded.

RESULTS

One hundred patients were enrolled and 93 patients (46 patients with celecoxib vs. 47 patients with oxycodone) were randomized. No differences were observed in patient demographics and preoperative VAS and ODI between the 2 groups. VAS and ODI were not different at all postoperative time points. However, subanalysis according to sex and age, revealed significant differences in efficacy: celecoxib was effective in female individuals and oxycodone was effective in male individuals on postoperative days 7 and 14; oxycodone was effective in patients aged above 65 years on postoperative days 7 and 14. Although nausea/vomiting and constipation were more common in the oxycodone group than in the celecoxib group, other adverse effects were not different.

CONCLUSIONS

In patients who underwent single-level lumbar decompressive surgery, treatment with celecoxib and oxycodone for postoperative pain management showed no significant differences in efficacy. However, subanalysis showed that each drug was effective in different ages and sex groups.

LEVEL OF EVIDENCE

Level II.

Prevalence of pain and treatment outcomes among cancer patients in a Malaysian palliative care unit

Background:

Pain remains one of the most common and debilitating symptoms of advanced cancer. To date, there is a lack of studies on pain and its treatment among Malaysian palliative care patients.

Objective:

This study aimed to explore the prevalence of pain and its treatment outcomes among adult cancer patients admitted to a palliative care unit in Sabah, Malaysia.

Methods:

Of 327 patients screened (01/09/15-31/12/17), 151 patients with assessed self-reported pain scores based on the numerical rating scale of 0-10 (current, worst and least pain within the past 24 hours) upon admission (baseline), 24, 48 and 72 hours post-admission and discharge were included. Pain severity and pain score reductions were analysed among those who experienced pain upon admission or in the past 24 hours. Treatment adequacy was measured by the Pain Management Index (PMI) among discharged patients. The PMI was constructed upon worst scores categorised as 0 (no pain), 1 (1-4, mild pain), 2 (5-6, moderate pain), or 3 (7-10, severe pain) which is then subtracted from the most potent level of prescribed analgesic drug scored as 0 (no analgesia), 1 (non-opioid), 2 (weak opioid) or 3 (strong opioid). PMI≥0 indicated adequate treatment.

Results:

Upon admission, 61.1% [95%CI 0.54:0.69] of 151 patients presented with pain. Of 123 patients who experienced pain upon admission or in the past 24 hours, 82.1% had moderate to severe worst pain. Throughout patients’ ward stay until discharge, there was an increased prescribing of analgesics and adjuvants compared to baseline, excluding weak opioids, with strong opioids as the mainstay treatment. For all pain score types (current, worst and least pain within the past 24 hours), means decreased at each time point (24, 48 and 72 hours post-admission and discharge) from baseline, with a significant decrease at 24 hours post-admission (p<0.001). Upon discharge (n=100), treatment adequacy significantly improved (PMI≥0 100% versus 68% upon admission, p<0.001).

Conclusions:

Accounting for pain’s dynamic nature, there was a high prevalence of pain among cancer patients in the palliative care unit. Continuous efforts incorporating comprehensive pain assessments, evidence-based treatments and patient education are necessary to provide adequate pain relief and end-of-life comfort care.

High dose gabapentin does not alter tumor growth in mice but reduces arginase activity and increases superoxide dismutase, IL-6 and MCP-1 levels in Ehrlich ascites

Objectives

The purpose of this study was to evaluate the effect of gabapentin on Ehrlich tumor growth in Swiss mice, a highly aggressive and inflammatory tumor model. Mice were grouped into sets of 5 animals and treated from days 2 to 8 with gabapentin 30 mg/kg body weight (G30) or 100 mg/kg body weight (G100), or normal sterile saline (control).

Results

The mice were euthanized on day 10. Tumor growth, tumoricidal agents and inflammatory cytokines levels were assessed. At day 10, G30 and G100 mice gained weight, but there were no differences in tumor cell count or in ascites volume. In G100, there was a reduction in arginase and an increase in SOD activities. There was an increase in IL-6 and MCP-1 levels, especially in G100, but no alterations in TNF-α. There was no direct evidence of tumor induction by gabapentin. However, the findings suggest that its use modulates immune response to a more effector and less deleterious profile, with increase in activity of anti-oxidant enzymes and in cytokines that favor activation of macrophages, which could improve the general status of the tumor host.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4103-9) contains supplementary material, which is available to authorized users.

A comparison between ketorolac and nefopam as adjuvant analgesics for postoperative patient-controlled analgesia: a randomized, double-blind, prospective study

Background

We compared the analgesic efficacy and side effects of ketorolac and nefopam that were co-administered with fentanyl via intravenous patient-controlled analgesia.

Methods

One hundred and sixty patients scheduled for laparoscopic cholecystectomy were randomly assigned to ketorolac (Group K) or nefopam (Group N) groups. The anesthetic regimen was standardized for all patients. The analgesic solution contained fentanyl 600 µg and ketorolac 180 mg in Group K, and fentanyl 600 µg and nefopam 120 mg in Group N. The total volume of analgesic solution was 120 ml. Postoperative analgesic consumption, recovery of pulmonary function, and pain intensities at rest and during the forced expiration were evaluated at postoperative 2, 6, 24, and 48 h. The postoperative side effects of analgesics were recorded.

Results

Cumulative postoperative analgesic consumptions at postoperative 48 h were comparable (Group K: 93.4 ± 24.0 ml vs. Group N: 92.9 ± 26.1 ml, P = 0.906) between the groups. Pain scores at rest and during deep breathing were similar at the time of each examination. The recovery of pulmonary function showed no significant differences between the groups. Overall, postoperative nausea and vomiting incidence was higher in Group N compared with Group K (59% vs. 34%, P = 0.015). The other side effects were comparable between both groups.

Conclusions

Analgesic efficacies of ketorolac and nefopam that were co-administered with fentanyl for postoperative pain management as adjuvant analgesics were similar. However, postoperative nausea and vomiting incidence was higher in the nefopam-fentanyl combination compared with the ketorolac-fentanyl combination.

What Do We Know about Opioids and the Kidney?

Evidence suggests a link between opioid use and kidney disease. This review summarizes the known renal manifestations of opioid use including its role in acute and chronic kidney injury. Both the direct and indirect effects of the drug, and the context which leads to the development of renal failure, are explored. While commonly used safely for pain control and anesthesia in those with kidney disease, the concerns with respect to side effects and toxicity of opioids are addressed. This is especially relevant with the worldwide increase in the use of opioids for medical and recreational use.

The research on long-term clinical effects and patients' satisfaction of gabapentin combined with oxycontin in treatment of severe cancer pain

Gabapentin has been used as an adjuvant for treatment of cancer pain. Previous studies showed that opioids combined with gabapentin for management of cancer pain reduced the dosage of opioids.The objective of this study was to explore the clinical effect and patients' satisfaction of oxycontin combined with gabapentin in treatment of severe cancer pain. After titration of morphine, 60 severe cancer patients with visual analog score (VAS) more than 7 were randomly divided into trial group (n = 30) and control group (n = 30). The control group was administered oxycontin and placebo, and the trial group was given oxycontin and gabapentin. VAS score was recorded pre- and post-treatment; while daily dose of oxycontin, daily cost of pain relief and life quality score were observed 1 week, 1 month, 2 months, 3 months, and 6 months post-treatment. We found that daily dose of oxycontin 1 month post was comparable between the 2 groups (P > 0.05). Three months post, compared with control group (58.0 ± 15.2 mg), average daily dose of oxycontin was significant lower in trial group (33.4 ± 11 mg) (P < 0.001). Average daily cost of pain relief in trail group (34.5 ± 10.2 RMB) was less than the control group (52.4 ± 13.7 RMB) (P < 0.001). Life quality score increased in all of the patients in both group post-treatment (P < 0.05); while life quality score in trail group was greater than in control group 3 months (46.8 ± 4.5 vs 43.5 ± 4.6, P = 0.007) and 6 months (46.5 ± 4.8 vs 41.4 ± 4.3, P < 0.001) post-treatment. The incidence of drowsiness and dizziness was comparable between the 2 groups (P > 0.05), while the incidence of nausea and vomiting (P = 0.038), and constipation (P < 0.001) was higher in the control group.We concluded that oxycontin combined with gabapentin used in severe cancer pain management can control pain effectively, decreased the dose of oxycontin and the cost of cancer pain relief, and reduced the incidence of nausea and vomiting, and constipation, increased the life quality.

How Do Hospital Palliative Care Teams Use the WHO Guidelines to Manage Unrelieved Cancer Pain? A 1-Year, Multicenter Audit in Japan

It has been reported that pain relief for patients with cancer is suboptimal in Japan. This has been mainly attributed to inadequate dissemination of the World Health Organization (WHO) guidelines for cancer pain management. To better understand this problem, we reviewed how 6 hospital palliative care teams (HPCTs) used the WHO guidelines for unrelieved pain in a 1-year audit that included 534 patients. The HPCT interventions were classified according to the contents of the WHO guidelines. In our study, HPCT interventions involved opioid prescriptions in >80% of referred patients, and “For the Individual” and “Attention to Detail” were the 2 most important principles. Our study indicates which parts of the WHO guidelines should be most heavily emphasized, when disseminating them in Japan.

Harpagophytum procumbens extract potentiates morphine antinociception in neuropathic rats

The association of opioids and non-steroidal anti-inflammatory drugs, to enhance pain relief and reduce the development of side effects, has been demonstrated. Given many reports concerning the antinociceptive and anti-inflammatory effects of Harpagophytum procumbens extracts, the aim of our study was to investigate the advantage of a co-administration of a subanalgesic dose of morphine preceded by a low dose of H. procumbens to verify this therapeutically useful association in a neuropathic pain model. Time course, registered with the association of the natural extract, at a dose that does not induce an antinociceptive effect, followed by a subanalgesic dose of morphine showed a well-defined antiallodynic and antihyperalgesic effect, suggesting a synergism as a result of the two-drug association. H. procumbens cooperates synergistically with morphine in resolving hyperalgesia and allodynia, two typical symptoms of neuropathic pain. The results support the strategy of using an adjuvant drug to improve opioid analgesic efficacy.

Use of non-opioid analgesics as adjuvants to opioid analgesia for cancer pain management in an inpatient palliative unit: does this improve pain control and reduce opioid requirements?

BACKGROUND

Cancer pain is complex, and despite the introduction of the WHO cancer pain ladder, few studies have looked at the prevalence of adjuvant medication use in an inpatient palliative medicine unit. In this study, we evaluate the use of adjuvant pain medications in patients admitted to an inpatient palliative care unit and whether their use affects pain scores or opiate dosing.

METHODS

In this retrospective observational study, patients admitted to the inpatient palliative care unit over a 3-month period with a diagnosis of cancer on opioid therapy were selected. Data pertaining to demographics, diagnosis, oral morphine dose equivalent of the opioid at the time of discharge, adjuvant analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and pain scores as reported by nurses and physicians were collected.

RESULTS

Seventy-seven patients were eligible over a 3-month period, out of which 65 (84 %) were taking an adjuvant medication. The most commonly prescribed adjuvant was gabapentin (70 %). Fifty-seven percent were taking more than one adjuvant. There were more women in the group receiving adjuvants (57 vs. 17%, p = 0.010). Those without adjuvants compared with those on adjuvants did not have worse pain scores on discharge as reported by physicians (0.8 ± 0.8 vs. 1.0 ± 0.7, p = 0.58) or nurses (2.0 ± 2.7 vs. 2.1 ± 2.6, p = 0.86). There was no difference in morphine equivalent doses of the opioid in both groups (median (min, max); 112 (58, 504) vs. 200 (30, 5,040)) at the time of discharge; 75-80 % of patients had improvement in pain scores as measured by a two-point reduction in numerical rating scale (NRS).

DISCUSSION

This study shows that adjuvant medications are commonly used for treating pain in patients with cancer. More than half of study population were on two adjuvants or an adjuvant plus NSAID along with an opioid. We did not demonstrate any benefit in terms of improved pain scores or opioid doses with adjuvants, but this could reflect confounding variables and physician choice. Larger prospective studies are needed to define the opioid-sparing effects of adjuvants.

CONCLUSION

Adjuvant agents are used in over 80 % of those treated for cancer pain.

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.

Withania somnifera root extract prolongs analgesia and suppresses hyperalgesia in mice treated with morphine

Previous studies demonstrated that Withania somnifera Dunal (WS), a safe medicinal plant, prevents the development of tolerance to the analgesic effect of morphine. In the present study, we investigated whether WS extract (WSE) (100 mg/kg, i.p.) may also modulate the analgesic effect induced by acute morphine administration (2.5, 5, 10 mg/kg, s.c.) in the tail-flick and in the hot plate tests, and if it may prevent the development of 2.5 mg/kg morphine-induced rebound hyperalgesia in the low intensity tail-flick test. Further, to characterize the receptor(s) involved in these effects, we studied, by receptor-binding assay, the affinity of WSE for opioid (μ, δ, k), cannabinoid (CB1, CB2), glutamatergic (NMDA), GABAergic (GABAA, GABAB), serotoninergic (5HT2A) and adrenergic (α2) receptors. The results demonstrated that (i) WSE alone failed to alter basal nociceptive threshold in both tests, (ii) WSE pre-treatment significantly protracted the antinociceptive effect induced by 5 and 10 mg/kg of morphine only in tail-flick test, (iii) WSE pre-treatment prevented morphine-induced hyperalgesia in the low intensity tail-flick test, and (iv) WSE exhibited a high affinity for the GABAA and moderate affinity for GABAB, NMDA and δ opioid receptors. WSE prolongs morphine-induced analgesia and suppresses the development of morphine-induced rebound hyperalgesia probably through involvement of GABAA, GABAB, NMDA and δ opioid receptors. This study suggests the therapeutic potential of WSE as a valuable adjuvant agent in opioid-sparing therapies.

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.

Valproic acid: an anticonvulsant drug with potent antinociceptive and anti-inflammatory properties

Valproic acid (VA) is a major antiepileptic drug, used for several therapeutic indications. It has a wide activity spectrum, reflecting on mechanisms of action that are not fully understood. The objectives of this work were to study the effects of VA on acute models of nociception and inflammation in rodents. VA (0.5, 1, 10, 25, and 50 mg/kg, p.o.) effects were evaluated on the carrageenan-induced paw edema, carrageenan-induced peritonitis, and plantar tests in rats, as well as by the formalin test in mice. The HE staining and immunohistochemistry assay for TNF-α in carrageenan-induced edema, from paws of untreated and VA-treated rats, were also carried out. VA decreased paw edema after carrageenan, and maximum effects were seen with doses equal to or higher than 10 mg/kg. VA also preserved the tissue architecture as assessed by the HE staining. Immunohistochemical studies revealed that VA significantly reduced TNF-α immunostaining in carrageenan-inflamed rat paws. In addition, the anti-inflammatory action of VA was potentiated by pentoxifylline (a phosphodiesterase inhibitor, known to inhibit TNF-α production), but not by sodium butyrate or by suberoylanilide hydroxamic acid (SAHA), nonspecific and specific inhibitors, respectively, of histone deacetylase. However, the decrease in the number of positive TNF-α cells in the rat paw was drastically potentiated in the VA + SAHA associated group. VA also reduced leukocytes and myeloperoxidase (MPO) releases to the peritoneal exudate, in the carrageenan-induced peritonitis. Although in the formalin test, VA inhibited both phases, the inhibition was mainly on the second phase. Furthermore, VA significantly increased the reaction time to thermal stimuli, as assessed by the plantar test. VA is a multi-target drug, presenting potent antinociceptive and anti-inflammatory properties at a lower dose range. These effects are partly dependent upon its inhibitory action on TNF-α-related pathways. However, the participation of the HDAC inhibition with the VA anti-inflammatory action cannot be ruled out. Inflammatory processes are associated with free radical damage and oxidative stress, and their blockade by VA could also explain the present results.