Pain management with opioids in adults

The Effectiveness of Tramadol in Pain Relief in Chronic Diseases: A Review Based on Clinical Trials

Tramadol is a synthetic opioid with a central effect from the aminocyclohexanol group, which has two main mechanisms of action, including as a weak agonist of opioid receptors and as a norepinephrine and serotonin reuptake inhibitor. The present study presents a review based on clinical trials designed in 2023. In July 2023, six international databases, including Medline/PubMed, ProQuest, Scopus, EMBASE, Google Scholar, and ISI (Web of Science), were searched and 58 articles were included in the study. The results of most studies showed that tramadol can be used as an analgesic drug, although in some studies it was shown that tramadol is not therapeutically superior in reducing pain compared to other treatments. Also, complications related to this treatment have been reported in some studies. Physicians should consider these factors to prevent drug toxicity, poor pain relief, use disorder in patients, and unpredictable complications. It should be noted that there is not enough evidence to support the long-term effectiveness of tramadol, but this argument also extends to nonopioid and other types of opioid analgesics, and the lack of long-term trials is due to regulatory and ethical issues. Although opioids can cause addiction when used for a long time, tramadol has a reasonable safety profile. According to the patient's condition and the clinical judgment of the medical professional, tramadol can be prescribed for patients, but the consequences of its use must be considered and a personalized treatment algorithm should be selected if the benefits outweigh the risks of the drug.

Targeting Pannexin-1 Channels: Addressing the 'Gap' in Chronic Pain

Chronic pain complicates many diseases and is notoriously difficult to treat. In search of new therapeutic targets, pannexin-1 (Panx1) channels have sparked intense interest as a key mechanism involved in a variety of chronic pain conditions. Panx1 channels are transmembrane proteins that release ions and small molecules, such as adenosine triphosphate (ATP). They are expressed along important nodes of the pain pathway, modulating activity of diverse cell types implicated in the development and progression of chronic pain caused by injury or pathology. This review highlights advances that have unlocked the core structure and machinery controlling Panx1 function with a focus on understanding and treating chronic pain.

Recent Trends in Nanomaterial Based Electrochemical Sensors for Drug Detection: Considering Green Assessment

An individual's therapeutic drug exposure level is directly linked to corresponding clinical effects. Rapid, sensitive, inexpensive, portable and reliable devices are needed for diagnosis related to drug exposure, treatment, and prognosis of diseases. Electrochemical sensors are useful for drug monitoring due to their high sensitivity and fast response time. Also, they can be combined with portable signal read-out devices for point-of-care applications. In recent years, nanomaterials such as carbon-based, carbon-metal nanocomposites, noble nanomaterials have been widely used to modify electrode surfaces due to their outstanding features including catalytic abilities, conductivity, chemical stability, biocompatibility for development of electrochemical sensors. This review paper presents the most recent advances about nanomaterials-based electrochemical sensors including the use of green assessment approach for detection of drugs including anticancer, antiviral, anti-inflammatory, and antibiotics covering the period from 2019 to 2023. The sensor characteristics such as analyte interactions, fabrication, sensitivity, and selectivity are also discussed. In addition, the current challenges and potential future directions of the field are highlighted.

Examining the relationship between head trauma and opioid use disorder: A systematic review

OBJECTIVE

To examine recent literature and determine common clinical risk factors between antecedent traumatic brain injury (TBI) and the following development of opioid misuse and provide a framework for clinical identification of at-risk subjects and evaluate potential treatment implications within this association.

DESIGN

A comprehensive systematic literature search of PubMed was conducted for articles between 2000 and December 2022. Studies were included if the human participant had any head trauma exposure and any chronic opioid use or dependence. After eligibility criteria were applied, 16 studies were assessed for thematic trends.

RESULTS

Opioid use disorder (OUD) risks are heightened in cohorts with head trauma exposed to opioids while in the hospital, specifically with tramadol and oxycodone. Chronic pain was the most common predictor of long-term OUD, and continuous somatic symptoms associated with the TBI can lead to long-term opioid usage. Individuals who present with coexisting psychiatric conditions pose significantly more risk associated with a higher risk of long-term opioid use.

CONCLUSION

Findings indicate that therapists and clinicians must consider a risk profile for persons with TBI and follow an integrated care approach to account for mental health, prior substance misuse, presenting somatic symptoms, and current medication regimen during evaluation.

Evidence-based guideline on chronic postsurgical pain management in adult patients in resource-restricted setting, 2023: systematic review and guideline

Background

Chronic postsurgical pain (CPSP) after tissue trauma is frequent and may have a long-lasting impact on the functioning and quality of life. The development of CPSP increases the burden on both the patient and the community. This review aims to systematically review articles and, lastly, pull an evidence-based guideline for CPSP management in adult patients in resource-limited areas.

Methodology

The review was reported based on preferred reporting items for the systemic review and meta-analysis (PRISMA) protocol. A literature search was conducted from the Cochrane, PubMed/Medline, and Google Scholar databases, and other gray literature from 2010 to 2022. The conclusion was made based on the level of evidence.

Results

A total of 3521 articles were identified through the database by searching strategies. Finally, by filtering duplicates unrelated to the topics, 22 articles (9 meta-analyses and systematic reviews, 12 systematic reviews, and one cohort study) were selected on the management of CPSP in adult patients. Filtering was made based on the intervention, outcome data of the population, and methodological quality.

Conclusion

Given the complexity and multidimensional nature of chronic postsurgical pain, effective assessment, and management require a comprehensive, multiaxial approach. Adequate preoperative preparation and counseling, potential risk identification and optimization, and use of a multimodal approach, and noninvasive surgical techniques are crucial in reducing the development of chronic postsurgical pain.

A Pilot Mixed-Methods Study to Establish the Clinical Usefulness of a Chronic Pain Profile (CPP) for Pain Management

The Chronic Pain Profile (CPP) was developed as a tool for patients to document types and levels of use for all pain management strategies used. This pilot mixed-methods (quantitative and qualitative methods) study aimed to assess the perceived clinical usefulness of the CPP and identify potential areas of difficulty using the CPP among a sample of pharmacists. Data were obtained from an online survey of pharmacists licensed to practice in Arizona. Quantitative analysis included assessing the clinical usefulness of the CPP using 10 numerical items (scores ≥50% = useful), 5 ordinal items (scores ≥ 4 out of 5 = useful), and 11 open-response items. Qualitative analysis was conducted by two independent researchers who coded the comments and identified key themes through consensus. Data were collected for 33 individuals. Mean usefulness scores ranged from 66.6 ± 22.4 to 80.9 ± 23.5, and three of the five ordinal items had a median score ≥ 4. Three key themes (and subthemes) were identified: favorable features of the CPP, which included promoting patient advocacy and saving time when accessing pain information; using the CPP, which included evaluating of the effectiveness and appropriateness of the pain management approach and identifying gaps in patient knowledge; and limitations of the CPP, which included absence of customization, interpretation issues, complexity and wording issues, and concerns of internal consistency and reliability. This pilot study provides initial evidence of the CPP's clinical usefulness that could ultimately be used to help manage pain and improve health outcomes. Further analyses are needed to assess the CPP's validity and explore its use in wider populations of patients with pain.

I Feel! Therefore, I Am from Pain to Consciousness in DOC Patients

Pain assessment and management in patients with disorders of consciousness (DOC) is a challenging and important aspect of care, with implications for detecting consciousness and promoting recovery. This narrative review explores the role of pain in consciousness, the challenges of pain assessment, pharmacological treatment in DOC, and the implications of pain assessment when detecting changes in consciousness. The review discusses the Nociception Coma Scale and its revised version, which are behavioral scales used to assess pain in DOC patients, and the challenges and controversies surrounding the appropriate pharmacological treatment of pain in these patients. Moreover, we highlight recent evidence suggesting that an accurate pain assessment may predict changes in the level of consciousness in unresponsive wakefulness syndrome/vegetative state patients, underscoring the importance of ongoing pain management in these patients.

Opioids and opioid receptors; understanding pharmacological mechanisms as a key to therapeutic advances and mitigation of the misuse crisis

Opioids are a mainstay in acute pain management and produce their effects and side effects (e.g., tolerance, opioid-use disorder and immune suppression) by interaction with opioid receptors. I will discuss opioid pharmacology in some controversial areas of enquiry of anaesthetic relevance. The main opioid target is the µ (mu,MOP) receptor but other members of the opioid receptor family, δ (delta; DOP) and κ (kappa; KOP) opioid receptors also produce analgesic actions. These are naloxone-sensitive. There is important clinical development relating to the Nociceptin/Orphanin FQ (NOP) receptor, an opioid receptor that is not naloxone-sensitive. Better understanding of the drivers for opioid effects and side effects may facilitate separation of side effects and production of safer drugs. Opioids bind to the receptor orthosteric site to produce their effects and can engage monomer or homo-, heterodimer receptors. Some ligands can drive one intracellular pathway over another. This is the basis of biased agonism (or functional selectivity). Opioid actions at the orthosteric site can be modulated allosterically and positive allosteric modulators that enhance opioid action are in development. As well as targeting ligand-receptor interaction and transduction, modulating receptor expression and hence function is also tractable. There is evidence for epigenetic associations with different types of pain and also substance misuse. As long as the opioid narrative is defined by the 'opioid crisis' the drive to remove them could gather pace. This will deny use where they are effective, and access to morphine for pain relief in low income countries.

Ketogenic diet enhances the effects of oxycodone in mice

Opioids have been used to manage pain for thousands of years, but they have significant potential for abuse. Prescription opioids, like oxycodone, are associated with 32% of overdoses, that have reached a total of 75,673 deaths in 2021. A major challenge is maximizing their therapeutic potential while minimizing the negative side effects including opioid use disorder (OUD). The Ketogenic Diet (KD) has been reported to reduce pain and decrease the severity of alcohol use disorder, yet its effects on oxycodone responses remain unknown. KD mice displayed increased oxycodone-induced locomotor activity and enhanced antinociceptive effects of oxycodone, suggesting a dietary effect on opiate sensitivity. Male KD mice exposed to chronic oxycodone exhibited increased naloxone-induced jumps, suggesting a sex-specific effect of diet on opioid withdrawal. Consistent with this, male KD mice self-administered less oxycodone while female KD mice did not differ from controls. Finally, no effect of KD on motivation to obtain oxycodone was observed during a progressive ratio schedule. These data suggest sex-biased effects of KD on responses to opioids that should be considered and potentially leveraged in both clinical pain management and treatment of OUD.

Interactive Effects of µ-Opioid and Adrenergic-α 2 Receptor Agonists in Rats: Pharmacological Investigation of the Primary Kratom Alkaloid Mitragynine and Its Metabolite 7-Hydroxymitragynine

The primary kratom alkaloid mitragynine is proposed to act through multiple mechanisms, including actions at µ-opioid receptors (MORs) and adrenergic-α 2 receptors (Aα 2Rs), as well as conversion in vivo to a MOR agonist metabolite (i.e., 7-hydroxymitragynine). Aα 2R and MOR agonists can produce antinociceptive synergism. Here, contributions of both receptors to produce mitragynine-related effects were assessed by measuring receptor binding in cell membranes and, in rats, pharmacological behavioral effect antagonism studies. Mitragynine displayed binding affinity at both receptors, whereas 7-hydroxymitragynine only displayed MOR binding affinity. Compounds were tested for their capacity to decrease food-maintained responding and rectal temperature and to produce antinociception in a hotplate test. Prototypical MOR agonists and 7-hydroxymitragynine, but not mitragynine, produced antinociception. MOR agonist and 7-hydroxymitragynine rate-deceasing and antinociceptive effects were antagonized by the opioid antagonist naltrexone but not by the Aα 2R antagonist yohimbine. Hypothermia only resulted from reference Aα 2R agonists. The rate-deceasing and hypothermic effects of reference Aα 2R agonists were antagonized by yohimbine but not naltrexone. Neither naltrexone nor yohimbine antagonized the rate-decreasing effects of mitragynine. Mitragynine and 7-hydroxymitragynine increased the potency of the antinociceptive effects of Aα 2R but not MOR reference agonists. Only mitragynine produced hypothermic effects. Isobolographic analyses for the rate-decreasing effects of the reference Aα 2R and MOR agonists were also conducted. These results suggest mitragynine and 7-hydroxymitragynine may produce antinociceptive synergism with Aα 2R and MOR agonists. When combined with Aα 2R agonists, mitragynine could also produce hypothermic synergism. SIGNIFICANCE STATEMENT: Mitragynine is proposed to target the µ-opioid receptor (MOR) and adrenergic-α2 receptor (Aα2R) and to produce behavioral effects through conversion to its MOR agonist metabolite 7-hydroxymitragynine. Isobolographic analyses indicated supra-additivity in some dose ratio combinations. This study suggests mitragynine and 7-hydroxymitragynine may produce antinociceptive synergism with Aα2R and MOR agonists. When combined with Aα2R agonists, mitragynine could also produce hypothermic synergism.

A 9-aminoacridine derivative induces growth inhibition of Ehrlich ascites carcinoma cells and antinociceptive effect in mice

Acridine derivatives have been found with anticancer and antinociceptive activities. Herein, we aimed to evaluate the toxicological, antitumor, and antinociceptive actions of N’-(6-chloro-2-methoxyacridin-9-yl)-2-cyanoacetohydrazide (ACS-AZ), a 9-aminoacridine derivative with antimalarial activity. The toxicity was assessed by acute toxicity and micronucleus tests in mice. The in vivo antitumor effect of ACS-AZ (12.5, 25, or 50 mg/kg, intraperitoneally, i.p.) was determined using the Ehrlich tumor model, and toxicity. The antinociceptive efficacy of the compound (50 mg/kg, i.p.) was investigated using formalin and hot plate assays in mice. The role of the opioid system was also investigated. In the acute toxicity test, the LD₅₀ (lethal dose 50%) value was 500 mg/kg (i.p.), and no detectable genotoxic effect was observed. After a 7-day treatment, ACS-AZ significantly (p < 0.05) reduced tumor cell viability and peritumoral microvessels density, suggesting antiangiogenic action. In addition, ACS-AZ reduced (p < 0.05) IL-1β and CCL-2 levels, which may be related to the antiangiogenic effect, while increasing (p < 0.05) TNF-α and IL-4 levels, which are related to its direct cytotoxicity. ACS-AZ also decreased (p < 0.05) oxidative stress and nitric oxide (NO) levels, both of which are crucial mediators in cancer known for their angiogenic action. Moreover, weak toxicological effects were recorded after a 7-day treatment (biochemical, hematological, and histological parameters). Concerning antinociceptive activity, ACS-AZ was effective on hotplate and formalin (early and late phases) tests (p < 0.05), characteristic of analgesic agents with central action. Through pretreatment with the non-selective (naloxone) and μ1-selective (naloxonazine) opioid antagonists, we observed that the antinociceptive effect of ACS-AZ is mediated mainly by μ1-opioid receptors (p < 0.05). In conclusion, ACS-AZ has low toxicity and antitumoral activity related to cytotoxic and antiangiogenic actions that involve the modulation of reactive oxygen species, NO, and cytokine levels, in addition to antinociceptive properties involving the opioid system.

Discovery of a novel class of benzoxazole derivatives as histamine H3 receptor ligands for the treatment of neuropathic pain

To discover effective analgesics, we summarize the synthesis, optimization, and pharmacological anti-nociceptive effects of a novel series of benzoxazole derivatives targeting H₃ receptor (H₃R). The new benzoxazoles were assayed in vitro for histamine H₃R and H₁R binding affinity. The best compound 8d (2-methyl-6-(3-(4-methylpiperazin-1-yl)propoxy)benzo[d]oxazole) exhibited high affinity for H₃R (K_i = 19.7 nM), high selectivity for ten other off-target receptors, and negligible effects on human ether-a-go-go-related gene (hERG, cardiac ion channel). In rodent animals, compound 8d dose-dependently reversed formalin-evoked pain (Phase I, ED₅₀ = 6.0 mg/kg; Phase II, ED₅₀ = 7.8 mg/kg) and CCI-induced neuropathic pain (chronic constriction injury, ED₅₀ = 15.6 mg/kg). Furthermore, compound 8d showed an excellent safety profile in acute toxicity test (LD₅₀ > 2000 mg/kg) with a therapeutic index (TI = LD₅₀/ED₅₀) > 250 and showed a desirable drug-like pharmacokinetic profile. Above characteristics indicate that compound 8d represents a promising candidate analgesic for the treatment of neuropathic pain.

Multidisciplinary management of chronic refractory pain in autosomal dominant polycystic kidney disease

BACKGROUND

Chronic pain is often difficult to manage in autosomal dominant polycystic kidney disease (ADPKD) patients and sometimes even leads to nephrectomy. We analyzed the long-term efficacy of our innovative multidisciplinary protocol to treat chronic refractory pain that aims to preserve kidney function by applying among other sequential nerve blocks.

METHODS

Patients were eligible if pain was present ≥3 months with a score of ≥50 on a visual analog scale (VAS) of 100, was negatively affecting quality of life and if there had been insufficient response to previous therapies, including opioid treatment. Treatment options were, in order, analgesics, cyst aspiration and fenestration, nerve blocks and nephrectomy.

RESULTS

A total of 101 patients were assessed in our clinic (mean age 50 ± 11 years, 65.3% females). Eight patients were treated with medication, 6 by cyst aspiration or fenestration, 63 by nerve blocks and 6 received surgery as the first treatment option. Overall, 76.9% experienced a positive effect on pain complaints shortly after treatment. The VAS score was reduced from 60/100 to 20/100 (P < 0.001) and patients decreased their number of nonopioid and opioid analgesics significantly (P < 0.001, P = 0.01, respectively). A substantial number of the patients (n = 51) needed additional treatment. At the end of follow-up in only 13 patients (12.9%) was surgical intervention necessary: 11 nephrectomies (of which 10 were in patients already on kidney function replacement treatment), 1 liver transplantation and 1 partial hepatectomy. After a median follow-up of 4.5 years (interquartile range 2.5-5.3), 69.0% of the patients still had fewer pain complaints.

CONCLUSIONS

These data indicate that our multidisciplinary treatment protocol appears effective in reducing pain in the majority of patients with chronic refractory pain, while postponing or even avoiding in most patients surgical interventions such as nephrectomy in most patients.

Targeting the Sphingosine-1-Phosphate Axis for Developing Non-narcotic Pain Therapeutics

Chronic pain is a life-altering condition affecting millions of people. Current treatments are inadequate and prolonged therapies come with severe side effects, especially dependence and addiction to opiates. Identification of non-narcotic analgesics is of paramount importance. Preclinical and clinical studies suggest that sphingolipid metabolism alterations contribute to neuropathic pain development. Functional sphingosine-1-phosphate (S1P) receptor 1 (S1PR1) antagonists, such as FTY720/fingolimod, used clinically for non-pain conditions, are emerging as non-narcotic analgesics, supporting the repurposing of fingolimod for chronic pain treatment and energizing drug discovery focused on S1P signaling. Here, we summarize the role of S1P in pain to highlight the potential of targeting the S1P axis towards development of non-narcotic therapeutics, which, in turn, will hopefully help lessen misuse of opioid pain medications and address the ongoing opioid epidemic.