Current knowledge of buprenorphine and its unique pharmacological profile

Long-term efficacy and reduced side-effects of buprenorphine in patients with moderate and severe chronic pain

Background

Chronic pain significantly impacts quality of life and poses substantial public health challenges. Buprenorphine, a synthetic analog of thebaine, is recognized for its potential in managing moderate to severe chronic pain with fewer side effects and a lower incidence of tolerance compared to traditional opioids.

Objective

This retrospective study aimed to assess the long-term efficacy and safety of buprenorphine transdermal patches in patients with moderate and severe chronic pain, with a focus on pain relief sustainability and tolerance development.

Methods

This retrospective observational study involved 246 patients prescribed buprenorphine transdermal patches. We evaluated changes in pain intensity using the Numeric Rating Scale (NRS), assessed opioid tolerance based on FDA guidelines for morphine-equivalent doses, and measured patient-reported outcomes through the Patients' Global Impression of Change (PGIC). Any adverse events were also recorded.

Results

Over the 36-month period, there was a significant reduction in NRS scores for both moderate and severe pain patients, demonstrating buprenorphine's sustained analgesic effect. Tolerance measurement indicated that no patients required increases in morphine-equivalent doses that would meet or exceed the FDA's threshold for opioid tolerance (60 mg/day of morphine or equivalent). Additionally, patient satisfaction was high, with the PGIC reflecting significant improvements in pain management and overall wellbeing. The side effects were minimal, with skin reactions and nausea being the most commonly reported but manageable adverse events.

Conclusion

The study findings validate the long-term use of buprenorphine transdermal patches as an effective and safe option for chronic pain management, maintaining efficacy without significant tolerance development. These results support the continued and expanded use of buprenorphine in clinical settings, emphasizing its role in reducing the burdens of chronic pain and opioid-related side effects. Further research is encouraged to refine pain management protocols and explore buprenorphine's full potential in diverse patient populations.

Development and Verification of a Full Physiologically Based Pharmacokinetic Model for Sublingual Buprenorphine in Healthy Adult Volunteers that Accounts for Nonlinear Bioavailability

Sublingual buprenorphine is used for opioid use disorder and neonatal opioid withdrawal syndrome. The study aimed to develop a full physiologically based pharmacokinetic (PBPK) model that can adequately describe dose- and formulation-dependent bioavailability of buprenorphine. Simcyp (v21.0) was used for model construction. Four linear regression models (i.e., untransformed or log transformed for dose or proportion sublingually absorbed) were explored to describe sublingual absorption of buprenorphine across dose. Published clinical trial data not used in model development were used for verification. The PBPK model's predictive performance was deemed adequate if the geometric means of ratios between predicted and observed (P/O) area under the curve (AUC), peak concentration (Cmax), and time to reach Cmax (Tmax) fell within the 1.25-fold prediction error range. Sublingual buprenorphine absorption was best described by a regression model with logarithmically transformed dose. By integrating this nonlinear absorption profile, the PBPK model adequately predicted buprenorphine pharmacokinetics (PK) following administration of sublingual tablets and solution across a dose range of 2-32 mg, with geometric mean (95% confidence interval) P/O ratios for AUC and Cmax equaling 0.99 (0.86-1.12) and 1.24 (1.09-1.40), respectively, and median (5th to 95th percentile) for Tmax equaling 1.11 (0.69-1.57). A verified PBPK model was developed that adequately predicts dose- and formulation-dependent buprenorphine PK following sublingual administration. SIGNIFICANCE STATEMENT: The physiologically based pharmacokinetic (PBPK) model developed in this study is the first to adequately predict dose- and formulation-dependent sublingual buprenorphine pharmacokinetics. Accurate prediction was facilitated by the incorporation of a novel nonlinear absorption model. The developed model will serve as the foundation for maternal-fetal PBPK modeling to predict maternal and fetal buprenorphine exposures to optimize buprenorphine treatment for neonatal opioid withdrawal syndrome.

Plasma concentrations of buprenorphine administered via matrix-type transdermal patches applied at three different anatomical locations in healthy adult horses

Background

Anatomical location-dependent differences in transdermal opioid penetration are well described in human patients. Although this has been investigated in horses with fentanyl, there is no literature available on location-dependent plasma buprenorphine concentrations when administered as a transdermal matrix-type patch.

Objective

This study aims to compare the plasma concentrations achieved from the matrix-type transdermal buprenorphine patches placed at different anatomical sites (metacarpus, gaskin, and ventral tail base) in healthy adult horses.

Study design

This is a randomized experimental study with a Latin square design.

Methods

Six adult horses were given each of three treatments with a minimum 10-day washout period. For each treatment, two 20 μg h-1 matrix-type buprenorphine patches were applied to the ventral aspect of the tail base (TailTDP), metacarpus region (MetacarpusTDP), or gaskin region (GaskinTDP). Whole blood samples (for determination of buprenorphine concentration) and physiological variables were collected before (0 h) and at 0.5, 2, 4, 6, 8, 10, 12, 16, 24, 32, 48, 56, 72, 96 and 120 h after patches were applied. The patches were removed 96 h following placement and were analyzed for residual buprenorphine content. Buprenorphine concentrations were measured in plasma by LC-MS/MS. A mixed-effects model was used to analyze the physiological variables.

Results

Between the three treatment groups, there was no change in physiological variables across timepoints as compared to baseline and when compared to each other in a single horse and between horses (p > 0.3). When comparing all three locations, the buprenorphine uptake was observed to be more consistent with respect to measurable plasma concentrations >0.1 ng ml-1 when applied to the ventral aspect of the tail base. In the TailTDP group, the mean plasma buprenorphine concentrations were >0.1 ng ml-1 from 2 to 32 h. The highest group mean was 0.25 ng ml-1 noted at 4 h.

Conclusions

The metacarpal and gaskin regions presented more erratic and inconsistent buprenorphine uptake and plasma concentrations as compared to the ventral aspect of the tail base. Further research must be directed at investigating the optimal dose, achievable duration of analgesia, change in measurable plasma concentrations, and behavioral and systemic effects.

[Pharmacological pain management in cancer patients]

Pharmacological pain therapy in cancer patients is based on guideline recommendations, which, however, do not fully coincide in all aspects due to varying weighting of evidence. The present article discusses current issues including the decreasing significance of the World Health Organization (WHO) analgesic ladder, with its distinction between step 2 and 3 being increasingly questioned. Risks of nonopioid analgesics such as paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs), particularly in older populations, are discussed. Paracetamol may potentially reduce the effectiveness of immunotherapies. Aspects of administering analgesics via a feeding tube are considered. Recommendations for the treatment of episodic pain, transitioning between different opioids, and some relevant interactions are also discussed.

Morphinan Evolution: The Impact of Advances in Biochemistry and Molecular Biology

Morphinan-based opioids, derived from natural alkaloids like morphine, codeine and thebaine, have long been pivotal in managing severe pain. However, their clinical utility is marred by significant side effects and high addiction potential. This review traces the evolution of the morphinan scaffold in light of advancements in biochemistry and molecular biology, which have expanded our understanding of opioid receptor pharmacology. We explore the development of semi-synthetic and synthetic morphinans, their receptor selectivity and the emergence of biased agonism as a strategy to dissociate analgesic properties from undesirable effects. By examining the molecular intricacies of opioid receptors and their signaling pathways, we highlight how receptor-type selectivity and signaling bias have informed the design of novel analgesics. This synthesis of historical and contemporary perspectives provides an overview of the morphinan landscape, underscoring the ongoing efforts to mitigate the problems facing opioids through smarter drug design. We also highlight that most morphinan derivatives show a preference for the G protein pathway, although detailed experimental comparisons are still necessary. This fact underscores the utility of the morphinan skeleton in future opioid drug discovery.

Association between benzodiazepine coprescription and mortality in people on opioid replacement therapy: a population-based cohort study

OBJECTIVE

To investigate the association between opioid replacement therapy (ORT) and benzodiazepine (BZD) coprescription and all-cause mortality compared with the prescription of ORT alone.

DESIGN

Population-based cohort study.

SETTING

Scotland, UK.

PARTICIPANTS

Participants were people prescribed ORT between January 2010 and end of December 2020 aged 18 years or above.

MAIN OUTCOME MEASURES

All-cause mortality, drug-related deaths and non-drug related deaths.

SECONDARY OUTCOME

ORT continuous treatment duration.

ANALYSIS

Cox regression with time-varying covariates.

RESULTS

During follow-up, 5776 of 46 899 participants died: 1398 while on coprescription and 4378 while on ORT only. The mortality per 100 person years was 3.11 during coprescription and 2.34 on ORT only. The adjusted HR for all-cause mortality was 1.17 (1.10 to 1.24). The adjusted HR for drug-related death was 1.14 (95% CI, 1.04 to 1.24) and the hazard for death not classified as drug-related was 1.19 (95% CI, 1.09 to 1.30).

CONCLUSION

Coprescription of BZDs in ORT was associated with an increased risk of all-cause mortality, although with a small effect size than the international literature. Coprescribing was also associated with longer retention in treatment. Risk from BZD coprescription needs to be balanced against the risk from illicit BZDs and unplanned treatment discontinuation. A randomised controlled trial is urgently needed to provide a clear clinical direction.

TRIAL REGISTRATION NUMBER

NCT04622995.

Access challenges to opioid use disorder treatment among individuals experiencing homelessness: Voices from the streets

BACKGROUND

Achieving equitable access to medications for opioid use disorder (MOUD) such as buprenorphine is a pressing issue. Evidence suggests disparities in MOUD access based on race and socioeconomic status, further exacerbated by the COVID-19 pandemic. However, the drivers behind this access gap remain poorly understood. This study explores barriers to treatment access among individuals with opioid use disorder (OUD) experiencing homelessness.

METHODS

We interviewed 28 individuals in and around the Boston Public Health Commission (BPHC) Engagement Center, an area known for its high density of active substance use and homelessness. We asked about people's experiences, perceptions, and attitudes toward OUD treatment. We conducted a thematic analysis of our interview data.

RESULTS

Fifty-four percent of participants sampled were not prescribed MOUD. None of the participants reported having an active prescription of sublingual buprenorphine or buprenorphine/naloxone. White participants were more likely to have been prescribed buprenorphine in the past compared to participants of other races even in this socioeconomically homogeneous sample. Themes that emerged in our data included challenges to accessing MOUD due to reduced services during the COVID-19 pandemic, lost or stolen medications, fewer inpatient withdrawal management beds for women, transportation challenges, fear of adverse effects of MOUD, the perception that taking MOUD replaces one addiction for another, and community disapproval of MOUD. Participants also reported stigma and discrimination based on race, gender, and socioeconomic status.

CONCLUSION

Systems and individual-level factors contribute to the MOUD treatment gap across race and socioeconomic status. The COVID-19 pandemic posed additional access challenges. This study provides important, actionable insights about the barriers faced by a particularly vulnerable population of individuals with OUD experiencing homelessness.

Assessment of the potential of novel and classical opioids to induce respiratory depression in mice

BACKGROUND AND PURPOSE

Opioid-induced respiratory depression limits the use of μ-opioid receptor agonists in clinical settings and is the main cause of opioid overdose fatalities. The relative potential of different opioid agonists to induce respiratory depression at doses exceeding those producing analgesia is understudied despite its relevance to assessments of opioid safety. Here we evaluated the respiratory depressant and anti-nociceptive effects of three novel opioids and relate these measurements to their in vitro efficacy.

EXPERIMENTAL APPROACH

Respiration was measured in awake, freely moving male CD-1 mice using whole body plethysmography. Anti-nociception was measured using the hot plate test. Morphine, oliceridine and tianeptine were administered intraperitoneally, whereas methadone, oxycodone and SR-17018 were administered orally. Receptor activation and arrestin-3 recruitment were measured in HEK293 cells using BRET assays.

KEY RESULTS

Across the dose ranges examined, all opioids studied depressed respiration in a dose-dependent manner, with similar effects at the highest doses, and with tianeptine and oliceridine showing reduced duration of effect, when compared with morphine, oxycodone, methadone and SR-17018. When administered at doses that induced similar respiratory depression, all opioids induced similar anti-nociception, with tianeptine and oliceridine again showing reduced duration of effect. These data were consistent with the in vitro agonist activity of the tested compounds.

CONCLUSION AND IMPLICATIONS

In addition to providing effective anti-nociception, the novel opioids, oliceridine, tianeptine and SR-17018 depress respiration in male mice. However, the different potencies and kinetics of effect between these novel opioids may be relevant to their therapeutic application in different clinical settings.

Postoperative buprenorphine continuation in stabilized buprenorphine patients: A population cohort study

BACKGROUND AND AIMS

Sudden discontinuation of buprenorphine in the treatment of opioid use disorder can increase the risk of subsequent relapse and overdose. Little is known about buprenorphine use in the perioperative period. The aim of this study was to determine the rate of buprenorphine continuation after hospital discharge following surgery and factors associated with continuation.

DESIGN

A population-based retrospective cohort study was conducted using administrative data from Ontario, Canada, between 2012 and 2018. The cohort included individuals on continuous buprenorphine prior to surgery. Logistic regression modeling was used to estimate the association of buprenorphine continuation with demographic, opioid agonist treatment, surgical and health service use factors.

SETTING

Administrative databases from Institute for Clinical Evaluative Sciences (ICES) were used, which capture the Ontario, Canada, population. The data sets describe physician billing, monitoring of controlled substances and hospital discharges.

PARTICIPANTS

Adults (≥ 18 years, n = 2176) had received a buprenorphine/naloxone product continuously for at least 60 days for the treatment of opioid use disorder and subsequently underwent a surgical procedure.

MEASUREMENTS

Continuation (versus discontinuation) of buprenorphine prescriptions in the 14 days after surgical discharge was recommended. Exposures included demographic, comorbidity, opioid agonist treatment, surgical and health service use characteristics.

FINDINGS

About 176 (8.1%) of the 2176 patients discontinued buprenorphine after surgery. Inpatient surgery (versus ambulatory) was associated with reduced odds of continuation, with an unadjusted odds ratio (OR) of 0.17 [95% confidence interval (CI) = 0.12-0.25] and an adjusted OR of 0.16 (95% CI = 0.11-0.23) after accounting for age, sex, rural residence, neighborhood income quintile, Charlson comorbidity index, psychiatric hospitalizations in the past 5 years and recent dispensed supply of buprenorphine (number needed to harm of 6.6).

CONCLUSIONS

In Ontario, Canada, from 2012 to 2018, most patients receiving continuous preoperative buprenorphine therapy continued buprenorphine use after surgery. Inpatient surgery was a strong predictor of discontinuation compared with ambulatory procedures.

Post craniotomy pain management in Copenhagen rat by intraperitoneal or oral dosage of Tramadol: a comparative evaluation

Calvarial craniotomy in animal models involves pain and distress. Moderate to severe pain in laboratory animals requires adequate pain management strategies. According to previous studies, the options available for suitable analgesia for rat calvarial craniotomy are very few. For most analgesic treatments, injectable routes of administration are predominantly used. However, these routes require restraining the animals, which may cause unnecessary pain, distress and suffering. As a well-fare measure, we focused on pain management by oral administration of analgesia. In this particular study, which is a sub-study of a major experiment on bone regeneration with different polymeric scaffold materials, we have compared the analgesic efficacy of intraperitoneal (I/P) and oral administration of tramadol (10 mg/kg) over a period of 96 h post-surgery in rat craniotomy models. The focus of our study is to evaluate the potential pain reduction efficacy of orally administered Tramadol without any restraining involved. We have used various non-invasive methods to assess the pain-alleviating efficacy of tramadol administered through different methods. We found that the efficacy of oral administration of tramadol is comparable to I/P administration in alleviating pain. Additionally, oral administration through drinking water has the benefit of not putting the animal under unwanted restraining stress.

Reliability of urine drug testing among patients on buprenorphine transdermal patch

BACKGROUND

Urine drug testing (UDT) plays a significant role in monitoring patients on chronic opioid therapy (COT) for non-medical opioid use (NMOU). UDT, at times, can be inconsistent and misleading. We present a case where a patient on a buprenorphine patch had false negative results.

CASE DESCRIPTION

A female in her 70s with metastatic breast cancer presented with uncontrolled pain from a T6 compression fracture. She had no relief with tramadol 50 mg every 6 hours as needed. Due to an allergic reaction to hydromorphone, our team prescribed a buprenorphine patch of 5 μg/h. Subsequently, she expressed excellent pain control, and the clinician confirmed the patch placement on examination. She underwent a UDT during the visit. The UDT was negative for both buprenorphine and its metabolites. The literature review showed that false negative UDT results are relatively common among patients with low-dose buprenorphine patches. The combination of a thorough physical examination, a review of the Prescription Drug Monitoring Program, and reassuring scores on screening tools placed her at low risk for NMOU.

DISCUSSION

Buprenorphine has a ceiling effect on respiratory depression and a lower risk for addiction. However, when used in low doses, the drug might not have enough metabolites in the urine, leading to a false negative UDT. Such results might affect patient-physician relationships.

CONCLUSION

In addition to the UDT, a thorough history, screening for NMOU, physical exam, a review of PDMP, and a good understanding of opioid metabolism are necessary to help guide pain management.

The Emerging Role of Sigma Receptors in Pain Medicine

Sigma receptors are protein chaperones with the unexpected characteristic of being activated by ligand binding. As such, they represent intriguing new targets for potential drug development. As a protein chaperone, these "receptors" escort proteins from the endoplasmic reticulum to their destinations and act to correct misfolded proteins. The two subtypes of sigma receptors, named σ1 and σ2, are markedly distinct from each other. Agonists and antagonists at these receptors show promise as new drug targets, addressing a range of diseases including neurodegenerative disorders, cancer, and cardiac disorders, and may also be analgesic agents and rehabilitation drugs for opioid use disorder. As an analgesic, sigma receptors seem to be more effective in treating neuropathic than nociceptive pain. New bifunctional compounds are being developed with opioids, because agents targeting sigma receptors may have an opioid-sparing effect. The pipeline of agents based on the sigma receptors is long and may treat things from Fragile X syndrome to Parkinson's disease to Huntington's disease to cancer. A novel agent ADV502 acts as a high-affinity σ1 antagonist and partial agonist at the µ-opioid receptor and may be an important agent both for the treatment of neuropathic cancer pain and for rehabilitation of opioid use disorder. Since there has been little recent innovation in pain medicine regarding new compounds and drug targets, drugs that affect the sigma receptor system seem promising and encouraging.

Analgesic Effect of Buprenorphine for Chronic Noncancer Pain: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Buprenorphine is a partial agonist at the µ-opioid receptor and an antagonist at the delta and kappa opioid receptors. It has high affinity and low intrinsic activity at the µ-opioid receptor. Buprenorphine demonstrates no ceiling effect for clinical analgesia, but demonstrates this for respiratory depression and euphoria. It may provide effective analgesia while producing less adverse effects, making it a promising opioid analgesic. A systematic review and meta-analysis were performed to examine the analgesic efficacy of buprenorphine for patients with chronic noncancer pain.

METHODS

PubMed, MEDLNE, Embase, and the Cochrane Library were searched up to January 2022. Randomized controlled trials were included if they compared buprenorphine versus placebo or active analgesic in patients with chronic noncancer pain, where pain score was an outcome. Nonrandomized controlled trials, observational studies, qualitative studies, case reports, and commentaries were excluded. Two investigators independently performed the literature search, study selection, and data collection. A random-effects model was used. The primary outcome was the effect of buprenorphine on pain intensity in patients with chronic noncancer pain based on standardized mean difference (SMD) in pain score. Quality of evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Two separate literature searches were conducted for patients with and without opioid use disorder (OUD). Only one study met the search criteria for those with OUD. Fourteen randomized controlled trials were included for those without OUD. Buprenorphine was associated with reduced pain score (SMD = -0.368, P < .001, I 2 = 89.37%) compared to placebo or active analgesic. Subgroup meta-analyses showed statistically significant differences in favor of buprenorphine versus placebo (SMD = -0.404, P < .001), for chronic low back pain (SMD = -0.383, P < .001), when administered via the transdermal route (SMD = -0.572, P = .001), via the buccal route (SMD = -0.453, P < .001), with length of follow-up lasting <12 weeks (SMD = -0.848, P < .05), and length of follow-up lasting 12 weeks or more (SMD = -0.415, P < .001). There was no significant difference when compared to active analgesic (SMD = 0.045, P > .05). Quality of evidence was low to moderate.

CONCLUSIONS

Buprenorphine was associated with a statistically significant and small reduction in pain intensity compared to placebo. Both the transdermal and buccal routes provided pain relief. There was more evidence supporting its use for chronic low back pain.

Acute Pain Management in Traumatically Injured Patients With Outpatient Buprenorphine Therapy

INTRODUCTION

Acute pain management is challenging in trauma patients undergoing outpatient buprenorphine therapy at the time of injury due to the high binding affinity of this partial agonist. The purpose of this study was to evaluate acute pain management in admitted trauma patients with discontinued versus continued outpatient buprenorphine therapy.

MATERIALS AND METHODS

This retrospective study included adult trauma patients admitted to a level-1 trauma center between January 2017 and August 2020 who were receiving buprenorphine prior to admission. Groups were defined as buprenorphine discontinued (BD) or continued (BC) during hospitalization. The primary outcome compared median daily morphine milligram equivalents between groups. Secondary outcomes utilized patient-reported numeric rating scale (NRS) scores to compare incidences of no pain (NRS 0), mild (NRS 1-3), moderate (NRS 4-6), and severe (NRS 7-10) pain.

RESULTS

A total of 57 patients were included (BD 37 [64.9%] and BC 20 [35.1%]). The median (interquartile range) outpatient daily buprenorphine dose was similar between groups (8 [8-16] mg versus 16 [8-16], P = 0.25). Median daily morphine milligram equivalents was significantly higher during admission in the BD group (103.7 [80.7-166] versus 67 [30.8-97.4], P = 0.002). Incidence of no pain (7.1% versus 5.7%, P = 0.283), mild (5.5% versus 4.3%, P = 0.295), moderate (20.2%, 19.8%, P = 0.855), or severe (67.2% versus 70.2%, P = 0.185) pain was similar between BD and BC groups, respectively.

CONCLUSIONS

Continuation of outpatient buprenorphine therapy in acute trauma patients is associated with decreased daily opioid requirements and similar analgesic efficacy compared to patients with BD. Based on our findings, trauma patients receiving outpatient buprenorphine and not requiring ventilator support may benefit from buprenorphine continuation within 48 h of initial presentation.

Scope of, Motivations for, and Outcomes Associated with Buprenorphine Diversion in the United States: A Scoping Review

BACKGROUND

Expanding access to medications to treat opioid use disorder (OUD), such as buprenorphine, is an evidence-based response to the mounting drug overdose crisis. However, concerns about buprenorphine diversion persist and contribute to limited access.

METHODS

To inform decisions about expanding access, a scoping review was conducted on publications describing the scope of, motivations for, and outcomes associated with diverted buprenorphine in the U.S.

RESULTS

In the 57 included studies, definitions for diversion were inconsistent. Most studied use of illicitly-obtained buprenorphine. Across studies, the scope of buprenorphine diversion ranged from 0% to 100%, varying by sample type and recall period. Among samples of people receiving buprenorphine for OUD treatment, diversion peaked at 4.8%. Motivations for using diverted buprenorphine were self-treatment, management of drug use, to get high, and when drug of choice was unavailable. Associated outcomes examined trended toward positive or neutral, including improved attitudes toward and retention in MOUD.

CONCLUSIONS

Despite inconsistent definitions of diversion, studies reported a low scope of diversion among people receiving MOUD, with inability to access treatment as a motivating factor for using diverted buprenorphine, and increased retention in MOUD as an outcome associated with use of diverted buprenorphine. Future research should explore reasons for diverted buprenorphine use in the context of expanded treatment availability to address persistent barriers to evidence-based treatment for OUD.

Treatment of Pain in Ferrets

Ferrets often require pain management as part of comprehensive veterinary care. Recognition and objective quantification of pain, such as the ferret grimace scale, are the first steps of an analgesic plan. As in other species, a multimodal approach to pain management is preferred, which includes combining analgesic drugs of multiple classes and/or techniques to affect different areas of the pain pathway. This article reviews the current published literature on analgesic medications in domestic ferrets, including specific drugs, doses, dosing intervals, and routes of administration.

Treatment of Pain in Rats, Mice, and Prairie Dogs

Recent myomorph and scuiromorph rodent analgesia studies are reviewed and evaluated for potential clinical application. Differences between laboratory animal studies and clinical use in diseased animals are discussed. Analgesia classes reviewed include local anesthetics, nonsteroidal anti-inflammatories, acetaminophen, opioids, and adjuvants such as anticonvulsants. Routes of administration including sustained-release mechanisms are discussed, as are reversal agents. Drug interactions are reviewed in the context of beneficial multimodal analgesia as well as potential adverse effects. Dosage recommendations for clinical patients are explored.

Fixed Dose Versus Loose Dose: Analgesic Combinations

Combinations of drugs may be fixed (two or more entities in a single product) or loose (two or more agents taken together but as individual agents) to help address multimechanistic pain. The use of opioids plus nonopioids can result in lower opioid consumption without sacrificing analgesic benefits. Drug combinations may offer additive or synergistic benefits. A variety of fixed-dose combination products are available on the market such as diclofenac plus thiocolchicoside, acetaminophen and caffeine, acetaminophen and opioid, ibuprofen and acetaminophen, tramadol and acetaminophen, and others. Fixed-dose combination products offer predictable pharmacokinetics and pharmacodynamics, known adverse events, and can reduce the pill burden. However, they are limited to certain drug combinations and doses; loose dosing allows prescribers the versatility to meet individual patient requirements as well as the ability to titrate as needed. Not all drug combinations offer synergistic benefits, which depend on the drugs and their doses. Certain drugs offer dual mechanisms of action in a single molecule, such as tapentadol, and these may further be used in combination with other analgesics. New technology allows for co-crystal productions of analgesic agents which may further improve drug characteristics, such as bioavailability. Combination analgesics are important additions to the analgesic armamentarium and may offer important benefits at lower doses than monotherapy.

Continuing Chronic Buprenorphine Perioperatively is Associated With Reduced Postoperative Opioid Use

INTRODUCTION

Buprenorphine is a frequently used medication for opioid use disorder and misunderstanding buprenorphine's unique pharmacology has historically complicated perioperative analgesia. The purpose of this study was to evaluate the association of perioperative buprenorphine continuation in patients with substance use disorder on perioperative opioid use.

MATERIALS AND METHODS

This was a single-center retrospective study at a level 1 trauma academic medical center. Adult patients using outpatient buprenorphine for medication for opioid use disorder admitted with an operating room booking were included. Patients were grouped (continuation, withheld) retrospectively based upon the decision to continue or omit buprenorphine therapy while admitted. The primary outcome of the study was any use of full mu-opioid agonists during days 1-7 of admission. Secondary outcomes included length of stay and average pain scores during days 1-7 of admission.

RESULTS

43.4% of patients in the continuation cohort used no full mu-opioid agonists during days 1-7 compared to 3.1% of patients in the withheld cohort (P < 0.001). No significant difference in median length of stay was noted (4.7 d [2.8-6.6] versus 6.1 d [4.0-8.2], P = 0.36). There was no statistical difference in average pain scores on postoperative days 1 (5.2 versus 6.9, P = 0.82) and 7 (0 versus 0, P = 0.41).

CONCLUSIONS

Perioperative continuation of buprenorphine is associated with reduced use of alternative full mu-opioid agents while admitted without impacting pain scores.

Suboxone: History, controversy, and open questions

There are more than 200 opioid overdose deaths each day in the US. In combating this epidemic we look to available treatment tools. Here, we find only three medications approved by the Food and Drug Administration (FDA) for the treatment of opioid use disorder. Of the three, buprenorphine is of particular importance due to its reduced overdose potential as a partial opioid agonist. Evidence supports its clinical equivalence to its full agonist cousin methadone, and suggests that it is better slated for long-term treatment of opioid use disorder compared to the non-selective opioid antagonist naltrexone. Buprenorphine is most popularized within Suboxone, a medication which also contains the non-selective opioid antagonist naloxone. The naloxone has no additional effect when the drug is taken as instructed, as it is intended to prevent diversion in those that would attempt to inject the medication. While Suboxone is regarded by some as the future of medical treatment, others have expressed concerns. This review aims to explore the history, controversy, and open questions that surround buprenorphine and its most prescribed variation, Suboxone. These include its pharmacological, legislative, and social history, alternative indications, efficacy as a treatment of opioid use disorder, and more. Armed with this information, the reader will have a more in-depth and holistic understanding of the medication's place in their community.

Opioid signaling and design of analgesics

Clinical treatment of acute to severe pain relies on the use of opioids. While their potency is significant, there are considerable side effects that can negatively affect patients. Their rise in usage has correlated with the current opioid epidemic in the United States, which has led to more than 70,000 deaths per year (Volkow and Blanco, 2021). Opioid-related drug development aims to make target compounds that show strong potency but with diminished side effects. Research into pharmaceuticals that could act as potential alternatives to current pains medications has relied on mechanistic insights of opioid receptors, a class of G-protein coupled receptors (GPCRs), and biased agonism, a common phenomenon among pharmaceutical compounds where downstream effects can be altered at the same receptor via different agonists. Opioids function typically by binding to an active site on the extracellular portion of opioid receptors. Once activated, the opioid receptor initiates a G-protein signaling pathway and/or the β-arrestin2 pathway. The proposed concept for the development of safe analgesics around mu and kappa opioid receptor subtypes has focused on not recruiting β-arrestin2 (biased agonism) and/or having low efficacy at the receptor (partial agonism). By altering chemical motifs on a common scaffold, chemists can take advantage of biased agonism as well as create compounds with low intrinsic efficacy for the desired treatments. This review will focus on ligands with bias profile, signaling aspects of the receptor and probe into the structural basis of receptor that leads to bias and/or partial agonism.

'Red Flags' and 'Red Tape': Telehealth and pharmacy-level barriers to buprenorphine in the United States

BACKGROUND

Structural vulnerabilities for people who use drugs (PWUD) were exacerbated by the COVID-19 pandemic. In this context, federal lawmakers in the United States (U.S.) invoked an exemption to the 2008 Ryan Haight Act requiring in-person evaluation to prescribe buprenorphine for treatment of opioid use disorder (OUD), which allowed for the initiation and maintenance of buprenorphine via telehealth. Despite the potential for telehealth to address some of the geographic disparities in OUD treatment access, recent research has suggested that significant barriers to buprenorphine also exist at the pharmacy level. The purpose of this study was to qualitatively assess how efforts to increase access to buprenorphine via telehealth are implemented by prescribers and pharmacists and experienced by patients.

METHODS

Participant observation and semi-structured interviews focused on telehealth for OUD treatment and buprenorphine prescribing and dispensing were conducted with patients (n = 19), prescribers and clinic staff (n = 24), and pharmacists (n = 10) in Pennsylvania and California between May 2020 - May 2021.

FINDINGS

While participants stated that telehealth for OUD treatment was a welcome option, pharmacy-level barriers to buprenorphine persisted. Geographical distance from patient to provider or pharmacist continued to serve as "red flags" for pharmacists, leading to pharmacy-level "red tape:" gatekeeping measures including geographic restrictions, telephone prescription "confirmations," prescription cancellations and refusals. Patients' unmet expectations of buprenorphine access in some cases led to unanticipated risks including a return to injection drug use.

CONCLUSION

Challenges to increasing buprenorphine access persist in the U.S. even in settings where telehealth is implemented, and telehealth may inadvertently produce new barriers for some patients. Despite national support for policies aimed at increasing access to treatment for substance use disorders rather than punishment, policy shifts from punishment to treatment have not permeated evenly across all geographic areas and populations. Perceived threats of Drug Enforcement Administration (DEA) enforcement, and self-defensive institutional practices in pharmacies, reinforce ideologies of drug law enforcement, leading to poor patient outcomes including lack of buprenorphine access.

Oral Morphine as an Alternative Substitution Treatment for Opioid Use Disorder, a Rare but Non-risk-free Use

Background

National health monitoring agencies have reported the alternative use of morphine sulfate painkiller for maintenance treatment of opioid use disorder (OUD), associated with a potential increase in overdose risk.

Objectives

This study sought to assess the prevalence of regular and occasional legally prescribed morphine use in patients treated for OUD and compare their characteristics to those of patients receiving conventional opioid maintenance treatment (OMT), buprenorphine or methadone. Then, we assessed the factors associated with opioid overdose risk.

Methods

Data were extracted from the French national healthcare system database, covering the entire population in 2015. Diagnosis associated with hospital discharge and long-term disease codes were extracted to select the population and identify outcomes and covariates. OUD non-chronic pain patients were divided into regular (≤35 days between dispensing and ≥3 months of continuous treatment duration) morphine users, and occasional users. Their sociodemographic and health characteristics were compared to OMT controls. A multivariate logistic regression model was performed to determine factors associated with opioid overdose.

Results

In patients treated for OUD, 2,237 (2.2%) morphine users (1,288 regular and 949 occasional), 64,578 (63.7%) buprenorphine and 34,638 (34.1%) methadone controls were included. The prevalence of regular morphine use among patients treated for OUD regularly receiving an opioid was 1.3%. Compared to users who receive morphine regularly, occasional users had an increased risk of overdose [OR = 2.2 (1.5-3.3)], while the risk was reduced in the buprenorphine group [OR = 0.5 (0.4-0.7)] and not significantly different for methadone [OR = 1.0 (0.7-1.4)]. Other overdose risk factors were low-income, comorbidity, i.e., psychiatric conditions, alcohol use disorder or complications related to intravenous drug use, and coprescription with benzodiazepines or pregabalin. These factors were more frequent in morphine groups.

Conclusions

Patients that were prescribed oral morphine represented a small minority of the treated for OUD. The poorer health condition affected by numerous comorbidities and higher risk of opioid overdose in patients treated with oral morphine compared with OMT controls points toward the need to better supervise the practices of these patients, to strengthen multidisciplinary care and risk reduction measures.

Comparison between Preoperative Methadone and Buprenorphine Use on Postoperative Opioid Requirement: A Retrospective Cohort Study

OBJECTIVES

Buprenorphine is a partial agonist at mu-opioid receptors and competes for these receptors with other opioids in vitro. Whether patients on buprenorphine maintenance require high doses of opioid analgesics to attain adequate postoperative pain control has not been determined. We evaluated differences in acute postoperative opioid consumption and pain burden between patients taking buprenorphine and those taking methadone preoperatively.

METHODS

Retrospective review of medical records of 928 patients of whom 195 were on buprenorphine and 733 were on methadone preoperatively, was performed. Among methadone and buprenorphine patients, 615 and 89 continued to receive the medications postoperatively. Buprenorphine patients were compared to methadone patients for the first 48-hours postoperatively with regard to acute opioid dose requirements (morphine milligram equivalents (MME) above their baseline buprenorphine and methadone doses) and time-weighted average (TWA) pain scores (using targeted maximum likelihood estimation).

RESULTS

Opioid dose requirements for 48-hours postoperatively were 150 [22 to 297] (median [interquartile range]) and 220 [90 to 360] MME for buprenorphine and methadone patients respectively. Preoperative buprenorphine was associated with a 59.9% lower postoperative MME (95% CI: 46.6 to 69.8%, P<0.0001) compared with methadone. Postoperative TWA pain scores for the first 48 hours were 5.0±2.7 (mean±standard deviation), and 5.4±2.3 for buprenorphine and methadone patients, respectively. Preoperative buprenorphine was associated with 0.37-point lower TWA pain score (95% CI from 0.14 to 0.61, P=0.0021) compared with methadone.

DISCUSSION

Preoperative buprenorphine use was associated with more than a 50% reduction in postoperative opioid dose requirement and a statistically significant, though clinically unimportant, reduction in acute pain burden in comparison to methadone. The study is limited by several important factors such as the exclusion of patients requiring intravenous patient controlled analgesia, small number of patients were on higher dose of buprenorphine, and a large percentage of methadone patients were not on stable dose of methadone yet.

Effects of Buprenorphine Treatment on Influenza Pathogenesis in the Ferret (Mustela putorius furo)

Ferrets are the gold-standard model for influenza A virus (IAV) research due to their natural susceptibility to human and zoonotic IAV, comparable respiratory anatomy and physiology to humans, and development of clinical signs similar to those seen in infected people. Because the presence and progression of clinical signs can be useful in infectious disease research, uncertainty in how analgesics alter research outcomes or compromise characteristics of disease progression have outweighed the concern regarding animal discomfort from these symptoms. Nonetheless, the principles of animal research require consideration of refinements for this important model for IAV research. Opioids offer a possible refinement option that would not directly affect the inflammatory cascade involved in IAV infection. Mirroring pathogenicity studies that use ferrets, 12 ferrets were inoculated intranasally with the A(H3N2) IAV A/Panama/2007/1999 and divided into 3 treatment groups ( n = 4 each), of which 2 groups received buprenorphine treatments on different schedules and the third received a saline control. The duration and location of viral replication, lymphohematopoietic changes, and clinical signs were comparable across all groups at all time points. High quantities of infectious virus in nasal wash specimens were detected in ferrets from all groups through day 5 after inoculation, and peak viral titers from the upper respiratory tract did not differ between ferrets receiving buprenorphine treatments on either schedule. Compared with the saline group, ferrets receiving buprenorphine exhibited transient weight loss and pyrexia, but all groups ultimately achieved similar peaks in both of these measurements. Collectively, these findings support the continued evaluation of buprenorphine as a refinement for IAV-challenged ferrets.

Buprenorphine for Chronic Pain: A Safer Alternative to Traditional Opioids

With the ongoing public health crisis with prescription opioids, there is a need for safer alternatives for medication management in chronic pain patients. Buprenorphine is a partial mu-opioid agonist which is commonly utilized to treat patients with opioid-use disorders. The purpose of this review is to discuss the potential use of this medication for the treatment of chronic pain instead of resorting to more traditional Schedule II opioids. Buprenorphine offers a safer alternative for patients who require opioids to manage chronic pain, given the unique pharmacological properties that allow it to provide adequate analgesia with less abuse potential.

Comparing characteristics and outcomes of different opioid agonist treatment modalities among opioid-dependent federal men correctional populations in Canada

BACKGROUND

Limited evidence exists in Canada on outcomes related to Opioid Agonist Treatment (OAT) and/or differences between OAT modalities among persons in correctional institutions. This study addresses this knowledge gap by examining key characteristics and outcomes of men in Canadian federal correctional institutions across treatment modalities.

METHODS

A retrospective cohort of men incarcerated in federal correctional institutions (N = 2833) were classified into four groups - three OAT participant groups: prescribed methadone (M-OAT), prescribed buprenorphine/naloxone (Suboxone®; S-OAT) and those who switched between the two OAT modalities at least once (X-OAT). The fourth group was a non-treatment comparison group (Non-OAT). Two-thirds of study participants were released and examined for post-release outcomes. Descriptive statistics and multi-variate Cox proportional hazards regression were used.

RESULTS

The X-OAT group was more likely than the other study groups to have positive urinalysis tests, disciplinary charges, or institutional security or behavioral incidents. Survival analysis indicated that the X-OAT had an adjusted hazard of a return to custody that was 57% greater than the other groups.

CONCLUSIONS

This study indicates that individuals switching OAT modalities are a more complex group needing additional supports, especially for community reintegration. Although few of the returns to custody were due to new offences, a third of participants in the OAT groups had their release revoked, indicating a high need population mostly due to their substance use.

Transdermal buprenorphine for pain management in children

Pain is one of the main symptoms reported by sick children, particularly by those suffering from cancer. Opioids are very useful in controlling this symptom but they are burdened with significant side effects that limit their use in children. Buprenorphine is a strong opioid that, due to its particular pharmacological characteristics, ensures excellent pain relief with fewer side effects than other opioids. The transdermal formulation allows for good pain control associated with optimal compliance by patients and few limitations on daily life. Unfortunately, transdermal buprenorphine use remains off-label for the control of chronic pain in children; therefore, it is desirable that new studies can validate its use in the paediatric population. This review aims to analyse the clinical advantages of transdermal buprenorphine in the paediatric population and the possible side effects registered in daily clinical practice.

A Novel Mitragynine Analog with Low-Efficacy Mu Opioid Receptor Agonism Displays Antinociception with Attenuated Adverse Effects

Mitragynine and 7-hydroxymitragynine (7OH) are the major alkaloids mediating the biological actions of the psychoactive plant kratom. To investigate the structure-activity relationships of mitragynine/7OH templates, we diversified the aromatic ring of the indole at the C9, C10, and C12 positions and investigated their G-protein and arrestin signaling mediated by mu opioid receptors (MOR). Three synthesized lead C9 analogs replacing the 9-OCH3 group with phenyl (4), methyl (5), or 3'-furanyl [6 (SC13)] substituents demonstrated partial agonism with a lower efficacy than DAMGO or morphine in heterologous G-protein assays and synaptic physiology. In assays limiting MOR reserve, the G-protein efficacy of all three was comparable to buprenorphine. 6 (SC13) showed MOR-dependent analgesia with potency similar to morphine without respiratory depression, hyperlocomotion, constipation, or place conditioning in mice. These results suggest the possibility of activating MOR minimally (G-protein Emax ≈ 10%) in cell lines while yet attaining maximal antinociception in vivo with reduced opioid liabilities.

SR-17018 Stimulates Atypical µ-Opioid Receptor Phosphorylation and Dephosphorylation

Opioid-associated overdoses and deaths due to respiratory depression are a major public health problem in the US and other Western countries. In the past decade, much research effort has been directed towards the development of G-protein-biased µ-opioid receptor (MOP) agonists as a possible means to circumvent this problem. The bias hypothesis proposes that G-protein signaling mediates analgesia, whereas ß-arrestin signaling mediates respiratory depression. SR-17018 was initially reported as a highly biased µ-opioid with an extremely wide therapeutic window. It was later shown that SR-17018 can also reverse morphine tolerance and prevent withdrawal via a hitherto unknown mechanism of action. Here, we examined the temporal dynamics of SR-17018-induced MOP phosphorylation and dephosphorylation. Exposure of MOP to saturating concentrations of SR-17018 for extended periods of time stimulated a MOP phosphorylation pattern that was indistinguishable from that induced by the full agonist DAMGO. Unlike DAMGO-induced MOP phosphorylation, which is reversible within minutes after agonist washout, SR-17018-induced MOP phosphorylation persisted for hours under otherwise identical conditions. Such delayed MOP dephosphorylation kinetics were also found for the partial agonist buprenorphine. However, buprenorphine, SR-17018-induced MOP phosphorylation was fully reversible when naloxone was included in the washout solution. SR-17018 exhibits a qualitative and temporal MOP phosphorylation profile that is strikingly different from any other known biased, partial, or full MOP agonist. We conclude that detailed analysis of receptor phosphorylation may provide novel insights into previously unappreciated pharmacological properties of newly synthesized MOP ligands.

Comparison of Nociceptive Effects of Buprenorphine, Firocoxib, and Meloxicam in a Plantar Incision Model in Sprague-Dawley Rats

Due to their reduced frequency of dosing and ease of availability, NSAIDs are generally preferred over opioids for rodent analgesia. We evaluated the efficacy of the highly COX2-selective NSAID firocoxib as compared with meloxicam and buprenorphine for reducing allodynia and hyperalgesia in rats in a plantar incision model of surgical pain. After a preliminary pharmacokinetic study using firocoxib, Sprague-Dawley rats (n = 12 per group, 6 of each sex) were divided into 6 groups: no surgery (anesthesia only), saline (surgery but no analgesia), buprenorphine (0.05 mg/kg SC every 8 h), meloxicam (2 mg/kg SC every 24 h), and 2 dosages of firocoxib (10 and 20 mg/kg SC every 24 h). The nociception assays were performed by using von Frey and Hargreaves methodology to test mechanical allodynia and thermal hyperalgesia. These assays were performed at 24 h before and at 20, 28, 44, and 52 h after start of surgery. None of the analgesics used in this study produced significantly different responses in allodynia or hyperalgesia from those of saline-treated rats. In the Hargreaves assay, female saline-treated rats experienced significantly greater hyperalgesia than did males. These findings add to a growing body of literature suggestingthat commonly used dosages of analgesics may not provide sufficient analgesia in rats experiencing incisional pain.

Site selective C-H functionalization of Mitragyna alkaloids reveals a molecular switch for tuning opioid receptor signaling efficacy

Mitragynine (MG) is the most abundant alkaloid component of the psychoactive plant material "kratom", which according to numerous anecdotal reports shows efficacy in self-medication for pain syndromes, depression, anxiety, and substance use disorders. We have developed a synthetic method for selective functionalization of the unexplored C11 position of the MG scaffold (C6 position in indole numbering) via the use of an indole-ethylene glycol adduct and subsequent iridium-catalyzed borylation. Through this work we discover that C11 represents a key locant for fine-tuning opioid receptor signaling efficacy. 7-Hydroxymitragynine (7OH), the parent compound with low efficacy on par with buprenorphine, is transformed to an even lower efficacy agonist by introducing a fluorine substituent in this position (11-F-7OH), as demonstrated in vitro at both mouse and human mu opioid receptors (mMOR/hMOR) and in vivo in mouse analgesia tests. Low efficacy opioid agonists are of high interest as candidates for generating safer opioid medications with mitigated adverse effects.

Benefit-Risk Analysis of Buprenorphine for Pain Management

Health care providers in the United States are facing challenges in selecting appropriate medication for patients with acute and chronic pain in the midst of the current opioid crisis and COVID-19 pandemic. When compared with conventional opioids, the partial µ-opioid receptor agonist buprenorphine has unique pharmacologic properties that may be more desirable for pain management. The formulations of buprenorphine approved by the US Food and Drug Administration for pain management include intravenous injection, transdermal patch, and buccal film. A comparison of efficacy and safety data from studies of buprenorphine and conventional opioids suggests that buprenorphine may be a better-tolerated treatment option for many patients that provides similar or superior analgesia. Our benefit-risk assessment in this narrative review suggests that health care providers should consider that buprenorphine may be an appropriate alternative for pain management over other opioids.

The End of the X-Waiver: Not a Moment Too Soon!

The X-waiver requires a physician to obtain specific training and federal certification to prescribe buprenorphine to treat opioid use disorder (OUD). Outgoing President Donald Trump issued an order that would have exempted many physicians from the X-waiver, but incoming President Biden stated they would repeal the Trump order despite campaign promises to better treat OUD. Opioid rehabilitation is a big business and a complex one, but there are not enough places in rehabilitation programs to meet demand, which is increasing year after year. In many cases, the X-waiver makes it more difficult and imposes more limitations on physicians to offer buprenorphine maintenance therapy than opioid prescribing. The Biden administration recently announced that it will not block the Trump orders, but rather will get rid of the X-waiver. The authors hope this is a permanent move away from the antiquated X-waiver. Further, this would provide greater access to accessible, affordable, and evidence-based OUD treatment to more patients, and may help break down some healthcare disparities in the treatment of drug disorders.

Transdermal Buprenorphine for Acute Pain in the Clinical Setting: A Narrative Review

Transdermal buprenorphine is indicated for chronic pain management, but as its role in the clinical management of acute pain is less clear, this narrative review examines studies of the patch for acute pain, mainly in the postoperative setting. Although perhaps better known for its role in opioid rehabilitation programs, buprenorphine is also an effective analgesic that is a Schedule III controlled substance. Although buprenorphine is a partial agonist at the μ-opioid receptor, it is erroneous to think of the agent as a partial analgesic; it has full analgesic efficacy and unique attributes among opioids, such as a ceiling for respiratory depression and low “drug likeability” among those who take opioids for recreational purposes. Transdermal buprenorphine has been most thoroughly studied for acute pain control in postoperative patients. Postoperative pain follows a distinct and predictable trajectory depending on the type of surgery and patient characteristics. Overall, when the patch is applied prior to surgery and left in place for the prescribed seven days, it was associated with reduced postoperative pain, lower consumption of other analgesics, and patient satisfaction. Transdermal buprenorphine has been evaluated in clinical studies of patients undergoing gynecological surgery, hip fracture surgery, knee or hip arthroscopy/arthroplasty, shoulder surgery, and spinal surgery. Transdermal buprenorphine may also be appropriate pain medication for controlling pain during postsurgical orthopedic rehabilitation programs. Transdermal buprenorphine may result in typical opioid-associated side effects but with less frequency than other opioids. Despite clinical reservations about transdermal buprenorphine and its potential role in acute pain management in the clinical setting, clinical acceptance may be hampered by the fact that it is off-label and buprenorphine is better known as an opioid maintenance agent rather than an analgesic.

Perioperative Pain Management and Opioid Stewardship: A Practical Guide

Surgical procedures are key drivers of pain development and opioid utilization globally. Various organizations have generated guidance on postoperative pain management, enhanced recovery strategies, multimodal analgesic and anesthetic techniques, and postoperative opioid prescribing. Still, comprehensive integration of these recommendations into standard practice at the institutional level remains elusive, and persistent postoperative pain and opioid use pose significant societal burdens. The multitude of guidance publications, many different healthcare providers involved in executing them, evolution of surgical technique, and complexities of perioperative care transitions all represent challenges to process improvement. This review seeks to summarize and integrate key recommendations into a "roadmap" for institutional adoption of perioperative analgesic and opioid optimization strategies. We present a brief review of applicable statistics and definitions as impetus for prioritizing both analgesia and opioid exposure in surgical quality improvement. We then review recommended modalities at each phase of perioperative care. We showcase the value of interprofessional collaboration in implementing and sustaining perioperative performance measures related to pain management and analgesic exposure, including those from the patient perspective. Surgery centers across the globe should adopt an integrated, collaborative approach to the twin goals of optimal pain management and opioid stewardship across the care continuum.

Relative addictive potential of opioid analgesic agents

Opioid overdoses and deaths continue to be a problem in the USA with a significant portion related to prescribed opioid analgesic agents. The role of pharmacogentic factors in opioid addiction is an active area of research. While all opioid analgesic agents have some addictive potential, it is clear that there are some with greater addictive potential. Oxycodone is the most widely abused opioid analgesic and it appears to predispose to chronic use with high likability by users. Fentanyl and hydromorphone are both very lipophilic allowing rapid penetration into the CNS, but are not rated as highly as other agents. Providers should consider the risk of addiction with the opioids they prescribe and give those with a lower addictive potential.

Novel hybrid compounds, opioid agonist+melanocortin 4 receptor antagonist, as efficient analgesics in mouse chronic constriction injury model of neuropathic pain

When the nerve tissue is injured, endogenous agonist of melanocortin type 4 (MC4) receptor, α-MSH, exerts tonic pronociceptive action in the central nervous system, contributing to sustaining the neuropathic pain state and counteracting the analgesic effects of exogenous opioids. With the intent of enhancing opioid analgesia in neuropathy by blocking the MC4 activation, so-called parent compounds (opioid agonist, MC4 antagonist) were joined together using various linkers to create novel bifunctional hybrid compounds. Analgesic action of four hybrids was tested after intrathecal (i.t.) administration in mouse models of acute and neuropathic pain (chronic constriction injury model, CCI). Under nerve injury conditions, one of the hybrids, UW3, induced analgesia in 1500 times lower i.t. dose than the opioid parent (ED50: 0.0002 nmol for the hybrid, 0.3 nmol for the opioid parent) and in an over 16000 times lower dose than the MC4 parent (ED50: 3.33 nmol) as measured by the von Frey test. Two selected hybrids were tested for analgesic properties in CCI mice after intravenous (i.v.) and intraperitoneal (i.p.) administration. Opioid receptor antagonists and MC4 receptor agonists diminished the analgesic action of these two hybrids studied, though the extent of this effect differed between the hybrids; this suggests that linker is of key importance here. Further results indicate a significant advantage of hybrid compounds over the physical mixture of individual pharmacophores in their analgesic effect. All this evidence justifies the idea of synthesizing a bifunctional opioid agonist-linker-MC4 antagonist compound, as such structure may bring important benefits in neuropathic pain treatment.

Sublingual Buprenorphine for Pediatric Cancer Pain: A Case Report and Review of the Literature

Pain is a common symptom in pediatric patients with cancer, and most patients in palliative care will receive opioids. Traditional opioids have several drawbacks, including their adverse effects, inconsistent or diminishing efficacy, and limited available routes of administration. Buprenorphine is an attractive option for pain management because of its safety profile, unique pharmacology, and availability in transdermal, buccal, parenteral, and sublingual (SL) dosage forms. Unfortunately, data supporting the use of buprenorphine in pediatric pain patients, particularly SL buprenorphine, are lacking. This case report describes the feasibility of SL buprenorphine use in pediatric patients with complex cancer-related pain.

Neuromodulation Management of Chronic Neuropathic Pain in The Central Nervous system

Neuromodulation is becoming one of the clinical tools for treating chronic neuropathic pain by transmitting controlled physical energy to the pre-identified neural targets in the central nervous system. Its nature of drug-free, non-addictive and improved targeting have attracted increasing attention among neuroscience research and clinical practices. This article provides a brief overview of the neuropathic pain and pharmacological routines for treatment, summarizes both the invasive and non-invasive neuromodulation modalities for pain management, and highlights an emerging brain stimulation technology, transcranial focused ultrasound (tFUS) with a focus on ultrasound transducer devices and the achieved neuromodulation effects and applications on pain management. Practical considerations of spatial guidance for tFUS are discussed for clinical applications. The safety of transcranial ultrasound neuromodulation and its future prospectives on pain management are also discussed.

The CB2 Agonist β-Caryophyllene in Male and Female Rats Exposed to a Model of Persistent Inflammatory Pain

Cannabinoids help in pain treatment through their action on CB1 and CB2 receptors. β-caryophyllene (BCP), an ancient remedy to treat pain, is a sesquiterpene found in large amounts in the essential oils of various spice and food plants such as oregano, cinnamon, and black pepper. It binds to the CB2 receptor, acting as a full agonist. Sex differences in the BCP-induced analgesic effect were studied by exposing male and female rats to a persistent/repeated painful stimulation. To simulate treatment of a repeated inflammatory condition, after the first formalin injection (FT1; 50 μl, 2.5%), rats received BCP per os for 7 days at two dosages: 5 and 10 mg/kg dissolved in olive oil (OIL). The control group was treated with OIL for 7 days. On day 8, the formalin test was repeated (FT2) with a lower formalin concentration (50 μl, 1%). During the first and second formalin tests, pain-induced responses (licking, flexing, and paw jerk) and spontaneous behaviors were recorded and analyzed. In the FT1 (before the beginning of treatment with BCP), females displayed higher pain responses than did males in terms of flexing duration during the first part of the test (I phase and interphase), while during the second part (II phase early and late) males showed higher levels than did females in licking duration. In the FT2, the pain responses generally decreased in the BCP groups in a dose-dependent manner (i.e., greater effect of BCP10), with a more pronounced reduction in males than in females; moreover, the pain responses remained high in the OIL groups and in the female BCP5 group. In conclusion, long-term intake of BCP appears to be able to decrease pain behaviors in a model of repeated inflammatory pain in both sexes, but to a greater degree in males.

Developments in combined analgesic regimens for improved safety in postoperative pain management

Introduction: Fixed-dose combination analgesic regimens may be similarly effective to opioid monotherapy but with potentially less risk. A number of individualized combination regimens can be created, including nonopioid agents such as acetaminophen and nonsteroidal anti-inflammatory drugs, opioids, and adjunctive agents such as gabapentin, pregabalin, and muscle relaxants. Areas covered: When such combinations have a synergistic effect, analgesic benefits may be enhanced. Many combination analgesic regimens are opioid sparing, which sometimes but not always results in reduced opioid-associated side effects. Safety concerns for all analgesics must be considered but postoperative analgesia is typically administered for a brief period (days), reducing risks that may occur with prolonged exposure. Expert opinion: Judiciously considered combination analgesic regimens can be effective postoperative analgesics that reduce opioid consumption without compromising pain control, which are important factors for patient recovery and satisfaction. The specific combinations used must be based on the patient, the type and duration of the surgical procedure, and complementary mechanisms of action of the agents used. In opioid-sparing combination analgesic regimens, the short-term use of small doses of opioids in this setting may be helpful for appropriate patients.

The utilization of buprenorphine in chronic pain

Reclassification of chronic pain as a disease may be helpful because patients with chronic pain require significant treatment and rehabilitation with a clear diagnosis. This can help address critical factors including suffering, quality of life, participation, and with family and social life, which continue to become more important in evaluating the quality of the health care we give our patients today. During the past decade of the opioid epidemic, methadone was the primary treatment for opioid addiction until buprenorphine was approved. Buprenorphine's high-affinity partial agonist properties make it a good alternative to methadone due to lower abuse potential and safer adverse effect profile while maintaining significant efficacy. Expanded out-patient prescribing options have allowed physician and physician extenders such as physician assistants and nurse practitioners to treat these patients that otherwise would have been required to utilize methadone. With unique pharmacological properties, buprenorphine is a safe and effective analgesic for chronic pain. The literature for buprenorphine shows great potential for its utilization in the treatment of chronic pain.

Adjuvants in pain medicine. Selection of the drug depending on the desired effect – so which drug to choose?

To date, much research has focused on finding the ideal adjuvant for local anesthetics. Each of them can have different effects. In anesthesiology and pain medicine, depending on the purpose, one or another effect may be desirable. For example, in some situations it is desirable to accelerate the onset of action or prolong the duration of the block, in others the desired effect may be a “response to intravascular administration”, it should also be borne in mind that not all adjuvants are allowed for intrathecal administration.

Analgesic impact of buprenorphine transdermal patch in total hip arthroplasty: A randomized controlled trial protocol

BACKGROUND

The efficacy and safety of buprenorphine transdermal patch (BTP) has been well established in chronic pain, but data regarding acute postoperative pain relief is still very limited. Therefore, we design a prospective, randomized, controlled study to evaluate the effectiveness and safety of the BTP for postoperative analgesia in total hip arthroplasty.

METHODS

This study is designed as a single-center, prospective, double-blind, randomized controlled trial. Group A receives a 10 mg patch of buprenorphine at the conclusion of surgery which is continued for 14 days. Group B receives a conventional analgesic regimen, that is, IV paracetamol 1 mg every 8 hours alternating with parenteral tramadol 50 mg every 8 hours for the first 2 postoperative days followed by oral administration of the same drug still the end of 2 weeks. A total of 160 patients are needed with an allowance for 10% drop-out. The primary outcome of this noninferiority study is opioid consumption within the first 24 hours following surgery. The secondary outcomes included numerical rating scale scores at rest, postoperative complications, length of hospital stay, and patient satisfaction.

RESULTS

This trial is expected to be the largest randomized trial assessing the efficacy of BTP after primary total hip arthroplasty and powered to detect a potential difference in the primary outcome.

TRIAL REGISTRATION NUMBER

This study protocol was registered in Research Registry (researchregistry5524).