Opioid Analgesics

Opioids and Youth Athletes

CONTEXT

The ongoing opioid epidemic and associated adverse effects impart a large burden on our current healthcare system. The annual economic and noneconomic cost of opioid use disorder and fatal opioid overdose is currently estimated at $1 trillion.

OBJECTIVE

This review presents the prevalence, frequency of use, need, and effectiveness of opioid analgesia in the youth and adolescent athlete population. It identifies current indications for opioid versus nonopioid analgesic use in the setting of acute orthopaedic injuries, postoperative management, concussion, and chronic pain. Current knowledge of youth athlete opioid use, risks related to use, misuse, diversion, and addiction are reviewed.

DATA SOURCES

A PubMed, Medline, and Cochrane Library search was conducted in February 2023 to review opioid pain management strategies in the pediatric athlete population from 2000 to present.

STUDY SELECTION

Searches were restricted to English language articles and human subjects. Initial reviews of titles and abstracts were performed by all authors and relevant full-text articles were selected. Priority was given to systematic and narrative reviews, meta-analyses, and prospective studies.

STUDY DESIGN

Narrative review.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

First author name, publication year, study design, study country, subject demographics, and data on the frequency, type, and duration of analgesic treatments for musculoskeletal injuries, postsurgical care, chronic pain disorders, and concussion were extracted.

RESULTS

Pediatric athletes comprise a high-risk population seeking analgesic relief for injury-related pain. Participation in high school sports is associated with increased risk of opioid use. An average of 28% to 46% of high school athletes have used opioids in their lifetime. Participation in ≥1 high school sport puts adolescents at 30% greater odds of future opioid misuse.

CONCLUSION

The use of opioids in the pediatric athlete population is common and associated with both short- and long-term risks of misuse and addiction.

Negative allosteric modulation of cannabinoid CB 1 receptor signaling suppresses opioid-mediated tolerance and withdrawal without blocking opioid antinociception

The direct blockade of CB 1 cannabinoid receptors produces therapeutic effects as well as adverse side-effects that limit their clinical potential. CB 1 negative allosteric modulators (NAMs) represent an indirect approach to decrease the affinity and/or efficacy of orthosteric cannabinoid ligands or endocannabinoids at CB 1 . We recently reported that GAT358, a CB 1 -NAM, blocked opioid-induced mesocorticolimbic dopamine release and reward via a CB 1 -allosteric mechanism of action. Whether a CB 1 -NAM dampens opioid-mediated therapeutic effects such as analgesia or alters other unwanted side-effects of opioids remain unknown. Here, we characterized the effects of GAT358 on nociceptive behaviors in the presence and absence of morphine. We examined the impact of GAT358 on formalin-evoked pain behavior and Fos protein expression, a marker of neuronal activation, in the lumbar dorsal horn. We also assessed the impact of GAT358 on morphine-induced slowing of colonic transit, tolerance, and withdrawal behaviors. GAT358 attenuated morphine antinociceptive tolerance without blocking acute antinociception. GAT358 also reduced morphine-induced slowing of colonic motility without impacting fecal boli production. GAT358 produced antinociception in the presence and absence of morphine in the formalin model of inflammatory nociception and reduced the number of formalin-evoked Fos protein-like immunoreactive cells in the lumbar spinal dorsal horn. Finally, GAT358 mitigated the somatic signs of naloxone-precipitated, but not spontaneous, opioid withdrawal following chronic morphine dosing in mice. Our results support the therapeutic potential of CB 1 -NAMs as novel drug candidates aimed at preserving opioid-mediated analgesia while preventing their unwanted side-effects. Our studies also uncover previously unrecognized antinociceptive properties associated with an arrestin-biased CB 1 -NAMs.

Highlights

CB 1 negative allosteric modulator (NAM) GAT358 attenuated morphine tolerance GAT358 reduced morphine-induced slowing of colonic motility but not fecal productionGAT358 was antinociceptive for formalin pain alone and when combined with morphineGAT358 reduced formalin-evoked Fos protein expression in the lumbar spinal cordGAT358 mitigated naloxone precipitated withdrawal after chronic morphine dosing.

Risk Factors for Self-Harm Ideation Among Persons Treated With Opioids for Chronic Low Back Pain

OBJECTIVES

Chronic pain is a significant health concern that adversely affects all aspects of life, including emotional well-being. Opioids are prescribed for the management of refractory, severe chronic pain, although they have been associated with adverse effects, including addiction and overdose. The aim of this study was to examine factors that predict thoughts of self-harm among adults with chronic pain who are prescribed opioids.

MATERIALS AND METHODS

Seven hundred sixty-five (N=765) persons with opioid-treated chronic lower back pain completed the Current Opioid Misuse Measure (COMM) and other validated questionnaires as part of a larger study. Response to 1 question from the COMM ("How often have you seriously thought about hurting yourself?") was used to assess suicide risk on a 5-point scale (0=never; 4=very often).

RESULTS

Participants were categorized into 3 groups according to their responses to the self-harm question: never (N=628; 82.1%), seldom or sometimes (N=74; 9.7%), and often or very often (N=63; 8.2%). Multivariate adjusted odds ratio (aOR) analyses indicated that reports of alcohol or drug overuse within the past month (aOR=1.41,[95% CI 1.11-1.78]), posttraumatic stress (PTSD; aOR=1.24,[1.07 to 1.44]), pain catastrophizing (aOR=1.03,[1.01 to 1.05]), not loving oneself (aOR=0.99,[.98-1.00]) and poor perceived mental health (aOR=0.94,[.92 to 97]) were most associated with thoughts of self-harm. Importantly, the ideation frequency of self-harm was highest among individuals treated with higher daily doses of opioids.

DISCUSSION

These results support the need for continued monitoring of adults treated with opioids for chronic pain, particularly among those on high-dose opioids who present with increased negative affect and concerns of substance misuse.

An Overview of Recent Developments in the Management of Burn Injuries

According to the World Health Organization (WHO), around 11 million people suffer from burns every year, and 180,000 die from them. A burn is a condition in which heat, chemical substances, an electrical current or other factors cause tissue damage. Burns mainly affect the skin, but can also affect deeper tissues such as bones or muscles. When burned, the skin loses its main functions, such as protection from the external environment, pathogens, evaporation and heat loss. Depending on the stage of the burn, the patient's condition and the cause of the burn, we need to choose the most appropriate treatment. Personalization and multidisciplinary collaboration are key to the successful management of burn patients. In this comprehensive review, we have collected and discussed the available treatment options, focusing on recent advances in topical treatments, wound cleansing, dressings, skin grafting, nutrition, pain and scar tissue management.

Strategies Used to Manage Chronic Pain in HIV-Disease: Comparing Persons Prescribed Opioids Versus Persons not Receiving Opioids

Chronic pain is common in people living with HIV (PLWH), causes substantial disability and is associated with limitations in daily activities. Opioids are commonly prescribed for pain treatment among PLWH, but evidence of sustained efficacy is mixed. There is little information available on how PLWH who have chronic pain use multimodal strategies in pain management. The current cross-sectional study examined background characteristics, self-reported pain, and the use of other pain treatments among 187 PLWH with chronic pain and depressive symptoms who were and were not prescribed opioids. Approximately 20.9% of participants reported using prescription opioids at the time of the study interview. These individuals were significantly more likely to report having engaged in physical therapy or stretching, strengthening or aerobic exercises in the previous 3 months, recent benzodiazepine use, and receiving disability payments. There were no significant differences in pain characteristics (pain-related interference, average pain severity, and worst pain severity) between the two groups. Those not prescribed opioids were more likely to report better concurrent physical functioning and general health, and fewer physical role limitations, but higher depression symptom severity. Our findings suggest that many PLWH with chronic pain and depressive symptoms express high levels of pain with deficits in physical function or quality of life despite their use of opioids. The high rate of co-use of opioids and benzodiazepines (30.8%) is a concern because it may increase risk of overdose. An integrated care approach that includes a variety of effective non-pharmacologic treatment strategies such as physical therapy may be beneficial in reducing the reliance on opioids for pain management.

Opioid deprescribing in long-term care in Ontario: A comparison of resident and facility characteristics

Residents of long-term care (LTC) homes have potentially painful conditions and are prescribed opioids to manage their pain, despite the risks associated with the use of these high-risk medications. Therefore, the overall aim of this study was to describe the associations between resident and facility characteristics of residents prescribed long-term opioid therapy and those who remained on opioids or had opioids deprescribed. We conducted a retrospective cohort study utilizing health administrative databases housed within ICES. Our cohort included 26,592 of 121,564 LTC residents (21.9%) of Ontario LTC homes who were prescribed long-term opioid therapy at cohort inception. Of these residents, 4,299 (16.2%) residents had opioids deprescribed during the follow-up period. Opioid deprescribing was associated with younger age, high comorbidity, and co-prescription with benzodiazepines and gabapentinoids. Our findings suggest that there is variation in the characteristics of residents who continued long-term opioid therapy and those who subsequently had opioids deprescribed, and these characteristics need to be considered as part of individualized pain management plans of care.

Opioid Agents and Cardiac Arrhythmia: A Literature Review

Opioids are compounds that cause similar effects to morphine by binding to its receptors. Opioids can be synthetic, semi-synthetic, or natural and can easily bind to the receptors of opioids in order to depict their effects, which may vary depending upon the exposure of the drug and its dose. However, several side effects of opioids can also be observed, with the most crucial being their impact on the heart's electrical activity. This review majorly focuses on opioids' impact on the prolongation of the QT curve and their arrhythmogenic susceptibility. Articles published up to the year 2022 in various databases were identified and searched with the use of keywords. Search terms included "cardiac arrhythmias," "QT interval," "opioids," "opioid dependence," and "torsade de pointes (TdP)". These terms highlight the impact of each opioid agent on the activity of the heart on an electrocardiogram. The results of the available data depict that opioids, such as methadone, pose higher risks, even when taken in smaller amounts, and have the capability for QT interval prolongation and TdP development. A variety of opioids, i.e., oxycodone and tramadol, are considered as intermediary risk drugs and can build long QT intervals and TdP in large doses. Several other opioids are considered low-risk drugs, including buprenorphine and morphine, which lead to no production of TdP and QT interval prolongation in daily routine doses. Evidence indicates a high risk of sinus bradycardia, atrial fibrillation, cardiac block, and supra-ventricular arrhythmias in opium consumers. This literature review will play a key role in determining the association between the use of opioids and cardiac arrhythmias. It will further highlight the practical implications of opioids for the management of cardiac issues based on their dose, frequency, and intensity. Moreover, it will also depict the adverse effects of opioids along with their dose-specific relationship. Opioids display disparate cardiac arrhythmogenicity, and methadone contains a greater ability to induce long QT intervals and hazardous arrhythmias at conventional doses. In order to reduce arrhythmogenic risk, opioids taken in large amounts should be monitored with a regular electrocardiogram in high-risk consumers, i.e., patients on opioid maintenance.

Polypharmacy and Potentially Inappropriate Medication Use in Older Adults With Systemic Lupus Erythematosus

OBJECTIVE

To assess the prevalence and potential risk factors for polypharmacy and prescribing of the potentially inappropriate medications, opioids and benzodiazepines/Z-drugs, in older adults with systemic lupus erythematosus (SLE).

METHODS

The study population comprised adults age ≥50 years meeting American College of Rheumatology or Systemic Lupus International Collaborating Clinics classification criteria followed at a tertiary care rheumatology clinic. Information on prescriptions filled in the 4 months preceding chart review was obtained from the Manitoba Drug Program Information Network. Clinical data, including age, sex, Charlson Comorbidity Index (CCI) score, Systemic Lupus Erythematosus Disease Activity Index 2000 score, prednisone use, SLE duration, and rural residence were abstracted from electronic medical records. Logistic regression analyses were performed to assess any association between polypharmacy (using 2 definitions: ≥5 and ≥10 medications), potentially inappropriate medication use, and clinical features.

RESULTS

A total of 206 patients (mean age 62 years, 91% female, 36% rural) were included: 148 (72%) filled ≥5 medications, 71 (35%) filled ≥10 medications, 63 (31%) used benzodiazepines/Z-drugs, and 50 (24%) used opioids. Among the 77 patients age ≥65 years, 57 (74%) filled ≥5 medications, and 26 (34%) filled ≥10 medications, compared to 30% and 4%, respectively, of Manitobans age ≥65 years (National Prescription Drug Utilization Information System, 2016). The odds of polypharmacy were greater with prednisone use (adjusted odds ratio [OR] 3.70 [95% confidence interval (95% CI) 1.40-9.79] for ≥5 medications), CCI score (adjusted OR 1.62 [95% CI 1.20-2.17]), and rural residence (adjusted OR 2.05 [95% CI 1.01-4.18]). Odds of benzodiazepine/Z-drug use were increased with polypharmacy (adjusted OR 4.35 [95% CI 1.69-11.22]), and odds of opioid use were increased with polypharmacy (adjusted OR 6.75 [95% CI 1.93-23.69]) and CCI score (adjusted OR 1.29 [95% CI 1.08-1.54]).

CONCLUSION

The prevalence of polypharmacy in this SLE cohort was higher than in the general Manitoban population. Polypharmacy is a strong marker for use of prescription benzodiazepines/Z-drugs and opioids.

Negative allosteric modulation of CB1 cannabinoid receptor signaling suppresses opioid-mediated reward

Blockade of cannabinoid type 1 (CB₁)-receptor signaling decreases the rewarding properties of many drugs of abuse and has been proposed as an anti-addiction strategy. However, psychiatric side-effects limit the clinical potential of orthosteric CB₁ antagonists. Negative allosteric modulators (NAMs) represent a novel and indirect approach to attenuate CB₁ signaling by decreasing affinity and/or efficacy of CB₁ ligands. We hypothesized that a CB₁-NAM would block opioid reward while avoiding the unwanted effects of orthosteric CB₁ antagonists. GAT358, a CB₁-NAM, failed to elicit cardinal signs of direct CB₁ activation or inactivation when administered by itself. GAT358 decreased catalepsy and hypothermia but not antinociception produced by the orthosteric CB₁ agonist CP55,940, suggesting that a CB₁-NAM blocked cardinal signs of CB₁ activation. Next, GAT358 was evaluated using in vivo assays of opioid-induced dopamine release and reward in male rodents. In the nucleus accumbens shell, a key component of the mesocorticolimbic reward pathway, morphine increased electrically-evoked dopamine efflux and this effect was blocked by a dose of GAT358 that lacked intrinsic effects on evoked dopamine efflux. Moreover, GAT358 blocked morphine-induced reward in a conditioned place preference (CPP) assay without producing reward or aversion alone. GAT358-induced blockade of morphine CPP was also occluded by GAT229, a CB₁ positive allosteric modulator (CB₁-PAM), and absent in CB₁-knockout mice. Finally, GAT358 also reduced oral oxycodone (but not water) consumption in a two-bottle choice paradigm. Our results support the therapeutic potential of CB₁-NAMs as novel drug candidates aimed at preventing opioid reward and treating opioid abuse while avoiding unwanted side-effects.

Metformin prevents morphine-induced apoptosis in rats with diabetic neuropathy: a possible mechanism for attenuating morphine tolerance

Morphine is a drug of choice for the treatment of severe and chronic pain, but tolerance to the antinociceptive effect limits its use. The development of tolerance to morphine has recently been associated with neuronal apoptosis. In this study, our aim was to investigate the effects of metformin on morphine-induced neuronal apoptosis and antinociceptive tolerance in diabetic rats. Three days of cumulative dosing were administered to establish morphine tolerance in rats. The antinociceptive effects of metformin (50 mg/kg) and test dose of morphine (5 mg/kg) were considered at 30-min intervals by thermal antinociceptive tests. To induce diabetic neuropathy, streptozotocin (STZ, 65 mg/kg) was injected intraperitoneally. ELISA kits were used to measure caspase-3, bax, and bcl-2 levels from dorsal root ganglion (DRG) tissue. Semi-quantitative scoring system was used to evaluate apoptotic cells with the the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method. The findings suggest that co-administration of metformin with morphine to diabetic rats showed a significant increase in antinociceptive effect compared to morphine alone. The antinociceptive tests indicated that metformin significantly attenuated morphine antinociceptive tolerance in diabetic rats. In addition, metformin decreased the levels of apoptotic proteins caspase 3 and Bax in DRG neurons, while significantly increased the levels of antiapoptotic Bcl-2. Semi-quantitative scoring showed that metformin provided a significant reduction in apoptotic cell counts in diabetic rats. These data revealed that metformin demonstrated antiapoptotic activity in diabetic rat DRG neurons and attenuated morphine tolerance. The antiapoptotic activity of metformin probably plays a significant role in reducing morphine tolerance.

The cannabinoid agonist CB-13 produces peripherally mediated analgesia in mice but elicits tolerance and signs of central nervous system activity with repeated dosing

ABSTRACT

Activation of cannabinoid receptor type 1 (CB 1 ) produces analgesia in a variety of preclinical models of pain; however, engagement of central CB 1 receptors is accompanied by unwanted side effects, such as psychoactivity, tolerance, and dependence. Therefore, some efforts to develop novel analgesics have focused on targeting peripheral CB 1 receptors to circumvent central CB 1 -related side effects. In the present study, we evaluated the effects of acute and repeated dosing with the peripherally selective CB 1 -preferring agonist CB-13 on nociception and central CB 1 -related phenotypes in a model of inflammatory pain in mice. We also evaluated cellular mechanisms underlying CB-13-induced antinociception in vitro using cultured mouse dorsal root ganglion neurons. CB-13 reduced inflammation-induced mechanical allodynia in male and female mice in a peripheral CB 1 -receptor-dependent manner and relieved inflammatory thermal hyperalgesia. In cultured mouse dorsal root ganglion neurons, CB-13 reduced TRPV1 sensitization and neuronal hyperexcitability induced by the inflammatory mediator prostaglandin E 2 , providing potential mechanistic explanations for the analgesic actions of peripheral CB 1 receptor activation. With acute dosing, phenotypes associated with central CB 1 receptor activation occurred only at a dose of CB-13 approximately 10-fold the ED 50 for reducing allodynia. Strikingly, repeated dosing resulted in both analgesic tolerance and CB 1 receptor dependence, even at a dose that did not produce central CB 1 -receptor-mediated phenotypes on acute dosing. This suggests that repeated CB-13 dosing leads to increased CNS exposure and unwanted engagement of central CB 1 receptors. Thus, caution is warranted regarding therapeutic use of CB-13 with the goal of avoiding CNS side effects. Nonetheless, the clear analgesic effect of acute peripheral CB 1 receptor activation suggests that peripherally restricted cannabinoids are a viable target for novel analgesic development.

Current Strategies for the Management of Painful Diabetic Neuropathy

The development of painful diabetic neuropathy (PDN) is a common complication of chronic diabetes that can be associated with significant disability and healthcare costs. Prompt symptom identification and aggressive glycemic control is essential in controlling the development of neuropathic complications; however, adequate pain relief remains challenging and there are considerable unmet needs in this patient population. Although guidelines have been established regarding the pharmacological management of PDN, pain control is inadequate or refractory in a high proportion of patients. Pharmacotherapy with anticonvulsants (pregabalin, gabapentin) and antidepressants (duloxetine) are common first-line agents. The use of oral opioids is associated with considerable morbidity and mortality and can also lead to opioid-induced hyperalgesia. Their use is therefore discouraged. There is an emerging role for neuromodulation treatment modalities including intrathecal drug delivery, spinal cord stimulation, and dorsal root ganglion stimulation. Furthermore, consideration of holistic alternative therapies such as yoga and acupuncture may augment a multidisciplinary treatment approach. This aim of this review is to focus on the current management strategies for the treatment of PDN, with a discussion of treatment rationale and practical considerations for their implementation.

Which Surgeries Are the Best Choice for Chronic Pancreatitis: A Network Meta-Analysis of Randomized Controlled Trials

Background

Surgery is an effective choice for the treatment of chronic pancreatitis (CP). However, there is no clear consensus regarding the best choice among the surgical procedures. The aim of this study is to conduct a network meta-analysis of randomized controlled trials comparing treatment outcomes to provide high-quality evidences regarding which is the best surgery for CP.

Methods

A systematic search of the PubMed (MEDLINE), SCIE, EMBASE, CENTRAL, and CDSR databases were performed to identify studies comparing surgeries for CP from the beginning of the databases to May 2020. Pain relief and mortality were the primary outcomes of interest.

Results

Ten studies including a total of 680 patients were identified for inclusion. PPPD had a better postoperative short-term pain relief and quality of life (QOL), but a worse pancreatic exocrine function deficiency and high morbidity. Berne had a significant postoperative long-term pain relief and mortality with a lower risk of pancreatic exocrine function deficiency.

Conclusion

The main surgical procedures including the PPPD, Beger procedure, Frey modification and Berne modification can efficaciously treat CP. The Berne modification may be first choice with better efficacy and less complications in pancreatic function, but the impact of postoperative QOL cannot be ignored. Furthermore, when the CP patients have a mass in the pancreatic head which cannot be distinguished from pancreatic cancer, the only legitimate choice should be PPPD or classical pancreaticoduodenectomy.

Optimization of bifunctional piperidinamide derivatives as σ1R Antagonists/MOR agonists for treating neuropathic pain

Here, we describe the optimization, synthesis, and associated pharmacological analgesic activities of a new series of bifunctional piperidinamide derivatives as sigma-1 receptor (σ1R) antagonists and mu opioid receptor (MOR) agonists. The new compounds were evaluated in vitro in σ1R and MOR binding assays. The most promising compound 114 (also called HKC-126), showed superior affinities for σ1R and MOR and good selectivity to additional receptors related to pain. Compound 114 showed powerful dose-dependent analgesic effects in the acetic acid writhing test, formalin test, hot plate test, and chronic constriction injury (CCI) neuropathic pain model. In contrast to an equianalgesic dose of fentanyl, compound 114 produced fewer opioid-like side effects, such as reward liability, respiratory depression, physical dependence, and sedation. Lastly, the pharmacokinetic properties of this drug were also acceptable, and these results suggest that compound 114, as a mixed σ1R/MOR ligand, has potential for treating neuropathic pain.

Valoración del riego de adicción a tramadol en pacientes con dolor crónico no oncológico

Objetivo El manejo del dolor crónico no oncológico con analgésicos opioides ha sido de importancia para el control de los síntomas y el restablecimiento de la actividad, sin embargo, el riesgo de adicción asociado a estos medicamentos es ampliamente conocido y evaluado. Este estudio evalúa el riesgo de adicción que presentaban los pacientes con manejo de tramadol describiendo los factores mas frecuentes en la muestra estudiada frente a lo reportado en la literatura. Métodos Una muestra de 76 pacientes de una clínica de dolor que están en manejo con tramadol y se les administra un cuestionario con características demográficas y con la escala Opioid Risk Tool para el riesgo de adicción. Resultados El 57,89% de los sujetos fueron mujeres, el 55,20% se encontraba entre los 29 y 59 años. El riesgo de adicción moderado se encontró en el 9,09% de las mujeres y en el 37,05% de los hombres. La inclusión de otras enfermedades como ansiedad y trastorno de estrés postraumático aumenta el riesgo de adicción a severo en 6,06% de los hombres. Conclusiones La valoración del riesgo de adicción a opioides debe tener en cuenta los factores encontrados en la población colombiana.

Effect of histone acetylation on maintenance and reinstatement of morphine-induced conditioned place preference and ΔFosB expression in the nucleus accumbens and prefrontal cortex of male rats

Recently, epigenetic mechanisms are considered as the new potential targets for addiction treatment. This research was designed to explore the effect of histone acetylation on ΔFosB gene expression in morphine-induced conditioned place preference (CPP) in male rats. CPP was induced via morphine injection (5 mg/kg) for three consecutive days. Animals received low-dose theophylline (LDT) or Suberoylanilide Hydroxamic acid (SAHA), as an histone deacetylase (HDAC) activator or inhibitor, respectively, and a combination of both in subsequent extinction days. Following extinction, a priming dose of morphine (1 mg/kg) was administered to induce reinstatement. H4 acetylation and ΔFosB expression in the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) were assessed on the last day of extinction and the following CPP reinstatement. Our results demonstrated that daily administration of SAHA (25 mg/kg; i.p.), facilitated morphine-extinction and decreased CPP score in reinstatement of place preference. Conversely, injections of LDT (20 mg/kg; i.p.) prolonged extinction in animals. Co-administration of LDT and SAHA on extinction days counterbalanced each other, such that maintenance and reinstatement were no different than the control group. The gene expression of ΔFosB was increased by SAHA in NAc and mPFC compared to the control group. Administration of SAHA during extinction days, also altered histone acetylation in the NAc and mPFC on the last day of extinction, but not on reinstatement day. Collectively, administration of SAHA facilitated extinction and reduced reinstatement of morphine-induced CPP in rats. This study confirms the essential role of epigenetic mechanisms, specifically histone acetylation, in regulating drug-induced plasticity and seeking behaviors.

Fecal microbiota transplantation and antibiotic treatment attenuate naloxone-precipitated opioid withdrawal in morphine-dependent mice

Opioid addiction can produce severe side effects including physical dependence and withdrawal. Perturbations of the gut microbiome have recently been shown to alter opioid-induced side-effects such as addiction, tolerance and dependence. In the present study, we investigated the influence of the gut microbiome on opioid withdrawal by evaluating the effects of fecal microbiota transplantation (FMT), antibiotic and probiotic treatments, and pharmacological inhibition of gut permeability in a mouse model of opioid dependence. Repeated intraperitoneal (i.p.) morphine treatment produced physical dependence that was quantified by measuring somatic signs of withdrawal (i.e. number of jumps) precipitated using the opioid antagonist naloxone. Morphine-dependent mice that received FMT from morphine-treated donor mice exhibited fewer naloxone-precipitated jumps compared to morphine-dependent counterparts receiving FMT from saline-treated donor mice. Microbial contents in the mouse cecum were altered by morphine treatment but were not differentially impacted by FMT. A broad-spectrum antibiotic cocktail (ABX) regimen reduced the bacterial load and attenuated naloxone-precipitated morphine withdrawal in morphine-dependent mice, whereas commercially available probiotic strains did not reliably alter somatic signs of opioid withdrawal. ML-7, a pharmacological inhibitor of gut permeability, reduced the morphine-induced increase in gut permeability in vivo but did not reliably alter somatic signs of naloxone-precipitated opioid withdrawal. Our results suggest that the gut microbiome impacts the development of physical dependence induced by chronic morphine administration, and that therapeutic manipulations of the gut microbiome may reduce opioid withdrawal.

Synergistic antihyperalgesic and antinociceptive effects of morphine and methyl 8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepine-3-carboxylate (MP-III-024): a positive allosteric modulator at α2GABAA and α3GABAA receptors

RATIONALE

Opioid and GABA_A receptors are both located in central nociceptive pathways, and compounds that activate these receptors have pain-relieving properties. To date, the interactive effects of concurrent administration of these compounds in preclinical models of pain-like behaviors have not been assessed.

OBJECTIVE

The purpose of this study was to examine the interactive effects of the μ-opioid agonist morphine and the α2GABA_A and α3GABA_A receptor positive allosteric modulator methyl 8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepine-3-carboxylate (MP-III-024) in preclinical models of mechanical hyperalgesia and thermal nociception.

METHODS

The antihyperalgesic and antinociceptive effects of morphine and MP-III-024 administered alone were assessed initially, followed by fixed-ratio mixtures of MP-III-024/morphine combinations. Drug interaction data were analyzed using isobolographic and dose-addition analyses. All studies were conducted in male CD-1 mice.

RESULTS

In the assay of mechanical hyperalgesia, each compound produced dose-dependent antihyperalgesic effects, whereas only morphine was effective on thermal nociception. Fixed-ratio mixtures of MP-III-024/morphine were also dose-dependently effective in both procedures. These drug combination studies revealed that morphine and MP-III-024 produced supra-additive (synergistic) effects in both assays, depending on their relative proportions.

CONCLUSIONS

These results demonstrate an interaction between α2GABA_A and α3GABA_A receptor- and μ-opioid receptor-mediated signals and suggest that combination therapy may be useful for the treatment of pain-related disorders.

PA-Int5: An isatin-thiosemicarbazone derivative that exhibits anti-nociceptive and anti-inflammatory effects in Swiss mice

Pain and inflammation are symptoms of various diseases, and they can be modulated by different pathways, thus highlighting the importance of investigating the therapeutic effects of novel compounds. Previous studies have shown that isatin-thiosemicarbazone exhibits antitumor, antifungal antibacterial and other biological properties. Based on the wide range of biological effects of these compounds, the aim of the present study was to investigate the central nervous system (CNS) performance, and the anti-nociceptive and anti-inflammatory activity of (Z)-2-(5-nitro-2-oxoindolin-3-ilidene)-N-hydroazinecarbothioamide (PA-Int5) in treated mice. Three doses of PA-Int5 were tested orally (1.0, 2.5 and 5.0 mg/kg) in the nociceptive and inflammatory animal models. Additionally, the potential sedative effects of PA-Int5 (5 mg/kg, oral gavage) were investigated using an open field and rotarod tests, to exclude any possible unspecific effects of the nociceptive assays. Anti-nociceptive activity was assessed using the acetic acid-induced abdominal contortion and formalin tests, whereas anti-inflammatory activity was assessed using a carrageenan-induced paw edema and zymosan-induced air-pouch models. PA-Int5 (5 mg/kg) induced anti-nociceptive activity in the abdominal contortion model. In the formalin test, PA-Int5 (at 2.5 and 5 mg/kg) reduced nociception in the second phase. At the higher dose tested, PA-Int5 did not affect spontaneous locomotion or motor coordination. The data revealed that at all doses tested, the compound significantly reduced paw edema following carrageenan administration. In the zymosan-induced air-pouch model, PA-Int5 potently inhibited leukocyte migration and protein levels at the site of inflammation. When combined, the results revealed, for the first time, that PA-Int5 exhibited anti-nociceptive and anti-inflammatory activities, and highlights its potential, as well that of other derivatives, as novel candidates for pain relief.

The self-serving benefits of being a good host: A role for our micro-inhabitants in shaping opioids' function

Opioids are highly efficacious in their ability to relieve pain, but they are liable for abuse, dependence, and addiction. Risk factors to develop opioid use disorders (OUD) include chronic stress, socio-environment, and preexisting major depressive disorders (MDD) and posttraumatic stress disorders (PTSD). Additionally, opioids reduce gut motility, induce loss of gut barrier function, and alter the composition of the trillions of microbes hosted in the gastrointestinal tract, known as the gut microbiota. The microbiota are significant contributors to the reciprocal communication between the central nervous system (CNS) and the gut, termed the gut-brain axis. They have strong influences on their host behaviors, including the ability to cope with stress, sociability, affect, mood, and anxiety. Thus, they are implicated in the etiology of MDD and PTSD. Here we review the latest studies demonstrating that intestinal flora can, directly and indirectly, by affecting sociability levels, responses to stress, and mental state, alter the responses to opioids. It suggests that microbiota can potentially be used to increase the resilience to develop analgesic tolerance and OUD.

Effectiveness and safety of repetitive transcranial magnetic stimulation for the treatment of morphine dependence: A retrospective study

Morphine dependence (MD) is a very common complication because of the chronic morphine consumption. Studies suggest that repetitive transcranial magnetic stimulation (rTMS) can be used for the treatment of MD. However, there is still lacking evidence to support rTMS for MD. Thus, this retrospective study aimed to investigate the effectiveness and safety of rTMS for patients with MD.In this retrosepctive study, a total of 100 patients with MD were included, and they were divided into a rTMS group (n = 50), and a control group (n = 50). All patients in both groups received occupational therapy. In addition, patients in the rTMS group received rTMS. All patients in both groups received a total of 8 weeks treatment. The outcomes comprised of morphine craving intensity, depression, anxiety, and sleep quality, which were appraised by Visual Analogue Scale (VAS), Self-Rating Depression Scale (SDS), Self-Rating Anxiety Scale (SAS), and Pittsburgh Sleep Quality Index (PSQI), respectively. In addition, treatment-related adverse events were also considered for assessment.After 8 weeks treatment, patients in the rTMS group exerted better benefits in improving VAS (P < .01), SDS (P < .01), SAS (P < .01), and PSQI (P < .01), than patients in the control group. In addition, this study did not identify treatment-related adverse events in both groups.The findings of this study showed that rTMS treatment showed promising effectiveness on patients with MD. However, future studies should focus on warranting the present findings.

Physician Perspective and Challenges Ordering/Interpreting Laboratory Tests Related to the Opioid Crisis in America

ABSTRACT

The opioid crisis is a profound public health crisis in the United States. It has significantly increased morbidity and mortality in our nation. There are many contributing factors to the opioid crisis, including a strong national and international interest to treat pain as effectively as possible. To combat this crisis, numerous strategies have been implemented over the past few years at the legislative, health system, and patient levels. As a result of these efforts, for the first time since 1999, drug overdose deaths in the United States decreased from 2017 to 2018, when deaths involving all opioids, prescription opioids, and heroin decreased by 2%, 13.5%, and 4.1%, respectively. To continue to curb the opioid crisis, it is imperative to optimize pain control through multidisciplinary and multimodal approaches and to adhere to opioid prescribing guidelines from regulatory and professional organizations to minimize risks for opioid misuse and abuse. Urine drug testing is an important means to assist with opioid monitoring and safe opioid prescribing. There are challenges when ordering urine drug tests, collecting specimens, and interpreting test results. Inaccurate interpretations of laboratory results can have significantly negative impacts on patients care and life. There is a critical need for prescriber education by laboratory experts in the use of drug testing and interpretation of results. To interpret test results correctly and make safe prescribing decisions, it is very important for prescribers/providers to consult clinical toxicologists, laboratory directors, and reporting staff. This interaction is vital and provides excellence of care for patients. This review aims to provide information concerning the opioid crisis in the United States and summarizes the challenges ordering and interpreting opioid-related laboratory testing as well as pertinent guidelines and recommendations.

Assessing the impact of a restrictive opioid prescribing law in West Virginia

Background

The Opioid Reduction Act (SB 273) took effect in West Virginia in June 2018. This legislation limited ongoing chronic opioid prescriptions to 30 days’ supply, and first-time opioid prescriptions to 7 days’ supply for surgeons and 3 days’ for emergency rooms and dentists. The purpose of this study was to determine the effect of this legislation on reducing opioid prescriptions in West Virginia, with the goal of informing future similar policy efforts.

Methods

Data were requested from the state Prescription Drug Monitoring Program (PDMP) including overall number of opioid prescriptions, number of first-time opioid prescriptions, average daily morphine milligram equivalents (MME) and prescription duration (expressed as “days’ supply”) given to adults during the 64 week time periods before and after legislation enactment. Statistical analysis was done utilizing an autoregressive integrated moving average (ARIMA) interrupted time series analysis to assess impact of both legislation announcement and enactment while controlling secular trends and considering autocorrelation trends. Benzodiazepine prescriptions were utilized as a control.

Results

Our analysis demonstrates a significant decrease in overall state opioid prescribing as well as a small change in average daily MME associated with the date of the legislation’s enactment when considering serial correlation in the time series and accounting for pre-intervention trends. There was no such association found with benzodiazepine prescriptions.

Conclusion

Results of the current study suggest that SB 273 was associated with an average 22.1% decrease of overall opioid prescriptions and a small change in average daily MME relative to the date of legislative implementation in West Virginia. There was, however, no association of the legislation on first-time opioid prescriptions or days’ supply of opioid medication, and all variables were trending downward prior to implementation of SB 273. The control demonstrated no relationship to the law.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13011-021-00349-y.

Prevalence and Its Correlation with Sustained Opioid Use in Korea: A Group-Based Trajectory Analysis

Long-term use of opioid analgesics can lead to addiction and opioid-related death. We aimed to present the pattern of long-term opioid utilization and identify factors associated with it by using group-based trajectory modeling. We used the nationwide health insurance claims database from 2009 to 2013. Multinomial logistic regression was conducted to estimate the adjusted odds ratio (aOR) and its 95% confidence intervals (CI) for the risk of sustained opioid use associated with various clinical factors. Among 15,327 patients prescribed with opioids, three trajectories were identified: high-sustained users (4.6%, n = 713), early discontinuation (84.2%, n = 12,916), and slow discontinuation (11.2%, n = 1,698). A higher proportion of women (72.8% vs. 58.4%) and elderly patients (55.9% vs. 22.1%) were found in the high-sustained users than the early discontinuation group. Depression (aOR 3.55, 95% CI 1.99-6.35) and epilepsy (aOR 10.12, CI 4.72-21.67) were the two highest comorbidities associated with sustained opioid use in the high-sustained users when compared to the early discontinuation group. Among chronic non-cancer patients, 4.6% were prescribed opioids consistently. Both healthcare providers and patients should be aware of the factors associated with sustained opioid use when prescribing it to patients with mental-related conditions, and its consequent adverse events should be carefully monitored.

Possible mechanism and potential application of anti-opioid effect of diazepam-binding inhibitor

AIMS

Our previous study has demonstrated that porcine diazepam-binding inhibitor (pDBI) and its active fragments, pDBI-16 and pDBI-19, have inhibition effect on morphine analgesia in mice. The present study aimed to investigate the underlying mechanism and potential application of this anti-opioid effect.

MATERIALS AND METHODS

Effect of DBI on morphine analgesia was examined by the tail electric stimulation vocalization test. Complementary peptides and antiserum were used to further confirm the effect of DBI in morphine tolerance and dependence. Pharmacological and microinjection methods were used to investigate the underlying mechanism.

KEY FINDINGS

Firstly, pDBI administered either intracerebroventricularly or intravenously dose-dependently inhibited morphine analgesia, while blocking DBI-16 or DBI-19 by the complementary peptides for DBI-16 (CP-DBI-16) or DBI-19 (CP-DBI-19) potentiated it in mice. Secondly, explicit immunoexpression of DBI in the lateral habenular (LHb) was observed in naive rats, and intra-LHb injection of pDBI dose-dependently abolished analgesic effect produced by intra-periaqueductal gray (PAG) injection of morphine in rats. Thirdly, pretreatment with N-Methyl-d-Aspartate receptor (NMDAR) antagonist MK-801 or nitric oxide (NO) synthase inhibitor L-NAME abolished the inhibition effect of pDBI, pDBI-16 or pDBI-19 on morphine analgesia in mice. Finally, antiserum against DBI dose-dependently reversed analgesic tolerance induced by increasing doses of morphine twice daily for 13 days in mice, while CP-DBI-16 or CP-DBI-19 significantly inhibited naloxone-precipitated morphine withdrawal jumping in mice.

SIGNIFICANCE

Taken together, our results demonstrated that NMDAR/NO signaling and LHb-PAG pathway are crucially involved in the anti-opioid effect of DBI, which could provide a potential biological target for opioid tolerance and dependence.

Use of Tramadol or Other Analgesics in Patients Treated in the Emergency Department as a Risk Factor for Opioid Use

The objective of this cohort study was to determine the association between the use of tramadol in emergency departments and the later consumption of opioids at the outpatient level in a group of patients from Colombia. Based on a medication dispensation database, patients over 18 years of age treated in different clinics in Colombia who for the first time received tramadol, dipyrone, or a nonsteroidal anti-inflammatory drug (NSAID) in the emergency room between January and December 2018 were identified. Three mutually exclusive cohorts were created, and each patient was followed up for 12 months after the administration of the analgesic to identify new formulations of any opioid. A Cox proportional-hazards regression model was constructed to identify variables associated with receiving a new opioid. A total of 12,783 patients were identified: 6020 treated with dipyrone, 5309 treated with NSAIDs, and 1454 treated with tramadol. The mean age was 47.1 ± 20.4 years, and 61.6% were women. A total of 17.3% (n = 2207) of all patients received an opioid during follow-up. Those treated with tramadol received a new opioid with a higher frequency (n = 346, 23.8%) than the other cohorts (14.7% NSAIDs and 17.9% dipyrone, both p < 0.001). In the tramadol group, using more than 10 mg of morphine equivalents was associated with a greater use of new opioids (HR:1.47, 95%CI:1.12-1.93). Patients treated with tramadol in emergency departments have a higher risk of opioid use at the one-year follow-up than those treated with NSAIDs or dipyrone.

The Role of Hydrogen Sulfide in the Development of Tolerance and Dependence to Morphine in Mice

OBJECTIVE

Hydrogen sulfide is an endogenous gaseous mediator that has been indicated to have a role in pain mechanisms. In this study, we aimed to detect brain and spinal cord hydrogen sulfide levels during different phases of tolerance and dependence to morphine and to determine the effects of inhibition of endogenous hydrogen sulfide production on the development of tolerance and dependence.

METHODS

Morphine tolerance and dependence was developed by subcutaneous injection of morphine (10 mg/kg) twice daily for 12 days. Physical dependence was determined by counting the jumps for 20 min, which is a withdrawal symptom occurring after a single dose of naloxone (5 mg/kg) administered intraperitoneally (i.p.). Propargylglycine (30 mg/kg, i.p.), a cystathionine-γ-lyase inhibitor, and hydroxylamine (12.5 mg/kg, i.p.), a cystathionine-β-synthase inhibitor, were used as hydrogen sulfide synthase inhibitors. The tail-flick and hot-plate tests were used to determine the loss of antinociceptive effects of morphine and development of tolerance.

RESULTS

It was found that chronic and acute uses of both propargylglycine and hydroxylamine prevented the development of tolerance to morphine, whereas they had no effect on morphine dependence. Chronic and acute administrations of hydrogen sulfide synthase inhibitors did not exert any difference in hydrogen sulfide levels in brain and spinal cords of both morphine-tolerant and -dependent animals.

CONCLUSION

It has been concluded that hydrogen sulfide synthase inhibitors may have utility in preventing morphine tolerance.

Effect of heat shock protein 70 modulators on the development of morphine analgesic tolerance in rats

The clinical use of opioid analgesics, such as morphine, is limited by analgesic tolerance, molecular mechanism of which is not well understood. Recently, molecular chaperone heat shock protein 70 (Hsp70) has been demonstrated to play important roles in morphine-induced neuroadaptation. Here, we focused on the involvement of Hsp70 in the development of analgesic tolerance to morphine. Rats were treated with morphine (5, 10, 20 mg/kg, subcutaneously) or saline once daily for 10 consecutive days. Hsp70 modulator N-formyl-3, 4-methylenedioxybenzylidine-γ-butyrolactam [KNK437, 100 mg/kg, intraperitoneally (i.p.)], geranylgeranylacetone (500 mg/kg, i.p.) or pifithrin-μ (20 mg/kg, i.p.) was administered before morphine (10 mg/kg, subcutaneously)/saline treatment. Analgesic effect of morphine was measured using the tail-flick latency test, and Hsp70 protein expression was examined by western blot. Analgesic effect of morphine decreased gradually with the increase in the number of days of morphine injection, indicating development of analgesic tolerance. A significant increase of Hsp70 expression in the periaqueductal gray was observed during the development of analgesic tolerance after repeated morphine injections. The development of morphine analgesic tolerance was suppressed by pre-treatment with Hsp70 transcriptional inhibitor KNK437 or functional antagonist pifithrin-μ, while promoted by pre-treatment with Hsp70 transcriptional inducer geranylgeranylacetone. Our results demonstrated that the development of morphine analgesic tolerance was dual regulated by Hsp70 modulators, suggesting Hsp70 as an interesting and new target for preventing the development of opioid analgesic tolerance.

The cannabinoid CB2 receptor agonist LY2828360 synergizes with morphine to suppress neuropathic nociception and attenuates morphine reward and physical dependence

The opioid crisis has underscored the urgent need to identify safe and effective therapeutic strategies to overcome opioid-induced liabilities. We recently reported that LY2828360, a slowly signaling G protein-biased cannabinoid CB₂ receptor agonist, suppresses neuropathic nociception and attenuates the development of tolerance to the opioid analgesic morphine in paclitaxel-treated mice. Whether beneficial effects of LY2828360 are dependent upon the presence of a pathological pain state are unknown and its impact on unwanted opioid-induced side-effects have never been investigated. Here, we asked whether LY2828360 would produce synergistic anti-allodynic effects with morphine in a paclitaxel model of chemotherapy-induced neuropathic pain and characterized its impact on opioid-induced reward and other unwanted side-effects associated with chronic opioid administration. Isobolographic analysis revealed that combinations of LY2828360 and morphine produced synergistic anti-allodynic effects in suppressing paclitaxel-induced mechanical allodynia. In wildtype (WT) mice, LY2828360 blocked morphine-induced reward in a conditioned place preference assay without producing reward or aversion when administered alone. The LY2828360-induced attenuation of morphine-induced reward was absent in CB₂ knockout (CB₂KO) mice. In the absence of a neuropathic pain state, LY2828360 partially attenuated naloxone-precipitated opioid withdrawal in morphine-dependent WT mice, and this withdrawal was itself markedly exacerbated in CB₂KO mice. Moreover, LY2828360 did not reliably alter morphine-induced slowing of colonic transit or attenuate tolerance to morphine antinociceptive efficacy in the hot plate test of acute nociception. Our results suggest that cannabinoid CB₂ receptor activation enhances the therapeutic properties of opioids while attenuating unwanted side-effects such as reward and dependence that occur with sustained opioid treatment.

Assessment of Probable Opioid Use Disorder Using Electronic Health Record Documentation

IMPORTANCE

Electronic health records are a potentially valuable source of information for identifying patients with opioid use disorder (OUD).

OBJECTIVE

To evaluate whether proxy measures from electronic health record data can be used reliably to identify patients with probable OUD based on Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) (DSM-5) criteria.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cross-sectional study analyzed individuals within the Geisinger health system who were prescribed opioids between December 31, 2000, and May 31, 2017, using a mixed-methods approach. The cohort was identified from 16 253 patients enrolled in a contract-based, Geisinger-specific medication monitoring program (GMMP) for opioid use, including patients who maintained or violated contract terms, as well as a demographically matched control group of 16 253 patients who were prescribed opioids but not enrolled in the GMMP. Substance use diagnoses and psychiatric comorbidities were assessed using automated electronic health record summaries. A manual medical record review procedure using DSM-5 criteria for OUD was completed for a subset of patients. The analysis was conducted beginning from June 5, 2017, until May 29, 2020.

MAIN OUTCOMES AND MEASURES

The primary outcome was the prevalence of OUD as defined by proxy measures for DSM-5 criteria for OUD as well as the prevalence of comorbidities among patients prescribed opioids within an integrated health system.

RESULTS

Among the 16 253 patients enrolled in the GMMP (9309 women [57%]; mean [SD] age, 52 [14] years), OUD diagnoses as defined by diagnostic codes were present at a much lower rate than expected (291 [2%]), indicating the necessity for alternative diagnostic strategies. The DSM-5 criteria for OUD can be assessed using manual medical record review; a manual review of 200 patients in the GMMP and 200 control patients identifed a larger percentage of patients with probable moderate to severe OUD (GMMP, 145 of 200 [73%]; and control, 27 of 200 [14%]) compared with the prevalence of OUD assessed using diagnostic codes.

CONCLUSIONS AND RELEVANCE

These results suggest that patients with OUD may be identified using information available in the electronic health record, even when diagnostic codes do not reflect this diagnosis. Furthermore, the study demonstrates the utility of coding for DSM-5 criteria from medical records to generate a quantitative DSM-5 score that is associated with OUD severity.

Spinal administration of the multi-functional opioid/neuropeptide FF agonist BN-9 produced potent antinociception without development of tolerance and opioid-induced hyperalgesia

Chronic opioids treatment is impeded by the development of analgesic tolerance and opioid-induced hyperalgesia. Recent studies have shown that multi-functional opioid compounds produce analgesic activities with limited side effects. We developed a novel multi-functional peptide targeting opioid and neuropeptide FF receptors named BN-9, which produced potent and non-tolerance forming antinociceptive effect after supraspinal and systemic administrations. In the present study, the analgesic properties and potential side effects of intrathecal BN-9 were investigated in a range of preclinical rodent models. In complete Freund's adjuvant-induced inflammatory pain model, intrathecal BN-9 dose-dependently produced analgesic effect via opioid receptors, and the spinal antinociceptive effect was augmented by the neuropeptide FF receptor antagonist RF9. In contrast, in plantar incision-induced postoperative pain model, BN-9 exhibited potent anti-allodynic effect via opioid receptors and, at least partially, neuropeptide FF receptors. In mouse models of acetic acid-induced visceral pain and formalin pain, BN-9-induced spinal antinociception was mainly mediated by opioid receptors, independent of neuropeptide FF receptors. Furthermore, at the spinal level, chronic treatments with BN-9 did not lead to analgesic tolerance and cross-tolerance to morphine. Moreover, opioid-induced hyperalgesia was observed after repeated administration of morphine, but not BN-9. Taken together, our present study suggests that intrathecal BN-9 produces potent and non-tolerance forming antinociception, and does not cause opioid-induced hyperalgesia. Thus, BN-9 might serve as a promising lead compound in the development of multi-functional opioid analgesics with minimized side effects.

HDAC6-selective inhibitors decrease nerve-injury and inflammation-associated mechanical hypersensitivity in mice

BACKGROUND

HDAC6 is a class IIB histone deacetylase expressed at many levels of the nociceptive pathway. This study tested the ability of novel and selective HDAC6 inhibitors to alleviate sensory hypersensitivity behaviors in mouse models of peripheral nerve injury and peripheral inflammation.

METHODS

We utilized the murine spared nerve injury (SNI) model for peripheral nerve injury and the Complete Freund's Adjuvant (CFA) model of peripheral inflammation. We applied the Von Frey assay to monitor mechanical allodynia.

RESULTS

Using the SNI model, we demonstrate that daily administration of the brain-penetrant HDAC6 inhibitor, ACY-738, abolishes mechanical allodynia in male and in female mice. Importantly, there is no tolerance to the antiallodynic actions of these compounds as they produce a consistent increase in Von Frey thresholds for several weeks. We observed a similar antiallodynic effect when utilizing the HDAC6 inhibitor, ACY-257, which shows limited brain expression when administered systemically. We also demonstrate that ACY-738 and ACY-257 attenuate mechanical allodynia in the CFA model of peripheral inflammation.

CONCLUSIONS

Overall, our findings suggest that inhibition of HDAC6 provides a promising therapeutic avenue for the alleviation of mechanical allodynia associated with peripheral nerve injury and peripheral inflammation.

Substance use disorders: diagnosis and management for hospitalists

Substance use disorder is a significant health concern. Hospitalists manage patient with various forms of substance use disorder on a daily basis. In this review, we have tried to synthesize evidence together to give a brief, yet succinct, review of commonly encounters disorders; alcohol intoxication and withdrawal, opioid intoxication and withdrawal, cocaine intoxication and methamphetamine intoxication. We describe clinical features, diagnosis and management, which would serve as a great resource for hospitalist when managing these complicated patients.

Positive Allosteric Modulation of CB1 Cannabinoid Receptor Signaling Enhances Morphine Antinociception and Attenuates Morphine Tolerance Without Enhancing Morphine- Induced Dependence or Reward

Opioid analgesics represent a critical treatment for chronic pain in the analgesic ladder of the World Health Organization. However, their use can result in a number of unwanted side-effects including incomplete efficacy, constipation, physical dependence, and overdose liability. Cannabinoids enhance the pain-relieving effects of opioids in preclinical studies and dampen unwanted side-effects resulting from excessive opioid intake. We recently reported that a CB₁ positive allosteric modulator (PAM) exhibits antinociceptive efficacy in models of pathological pain and lacks the adverse side effects of direct CB₁ receptor activation. In the present study, we evaluated whether a CB₁ PAM would enhance morphine’s therapeutic efficacy in an animal model of chemotherapy-induced neuropathic pain and characterized its impact on unwanted side-effects associated with chronic opioid administration. In paclitaxel-treated mice, both the CB₁ PAM GAT211 and the opioid analgesic morphine reduced paclitaxel-induced behavioral hypersensitivities to mechanical and cold stimulation in a dose-dependent manner. Isobolographic analysis revealed that combinations of GAT211 and morphine resulted in anti-allodynic synergism. In paclitaxel-treated mice, a sub-threshold dose of GAT211 prevented the development of tolerance to the anti-allodynic effects of morphine over 20 days of once daily dosing. However, GAT211 did not reliably alter somatic withdrawal signs (i.e., jumps, paw tremors) in morphine-dependent neuropathic mice challenged with naloxone. In otherwise naïve mice, GAT211 also prolonged antinociceptive efficacy of morphine in the tail-flick test and reduced the overall right-ward shift in the ED₅₀ for morphine to produce antinociception in the tail-flick test, consistent with attenuation of morphine tolerance. Pretreatment with GAT211 did not alter somatic signs of μ opioid receptor dependence in mice rendered dependent upon morphine via subcutaneous implantation of a morphine pellet. Moreover, GAT211 did not reliably alter μ-opioid receptor-mediated reward as measured by conditioned place preference to morphine. Our results suggest that a CB₁ PAM may be beneficial in enhancing and prolonging the therapeutic properties of opioids while potentially sparing unwanted side-effects (e.g., tolerance) that occur with repeated opioid treatment.

French-Canadian translation of a self-report questionnaire to monitor opioid therapy for chronic pain: The Opioid Compliance Checklist (OCC-FC)

Context: Chronic noncancer pain (CNCP) is a frequent condition among Canadians. The psychosocial and economic costs of CNCP for individuals, their families, and society are substantial. Though opioid therapy is often used to manage CNCP, it is also associated with risks of misuse. The Opioid Compliance Checklist (OCC) was developed to monitor opioid misuse in patients taking opioids for CNCP. The objective of the present study was to provide a French-Canadian translation of the eight-item OCC, the OCC-FC. Methods: The eight-item OCC was translated for use in Québec using published guidelines for the translation and adaptation of self-report measures, including an expert committee and a double forward-backward translation process. A pretest of the adapted eight-item OCC was also conducted among 30 patients with CNCP. Results: A French-Canadian version of the OCC was generated. When ambiguity in the items was detected during expert committee consultation or pretest administration, modifications made were kept to a strict minimum to facilitate future comparisons across studies using the original English and translated French-Canadian version. Discussion: This study provides a culturally adapted tool that will contribute to identifying French-Canadian patients with CNCP who misuse opioids over the course of opioid therapy. This translation of the OCC has the strong potential to be useful in research and clinical settings.

Grayanane diterpenoid glucosides as potent analgesics from Pieris japonica

A total of fifteen grayanane diterpenoid glucosides including eight undescribed ones, pierisjaponosides A-H, were isolated from the leaves of Pieris japonica (Thunb.) D. Don ex G. Don (Ericaceae). Their structures were established by extensive spectros copic techniques including HRESIMS and NMR, as well as chemical methods. The absolute configurations of pierisjaponosides A, B, and D were finally established by single-crystal X-ray diffraction with Cu Kα radiation. This is the first time to report the crystal structure of a 5,9-epoxygrayanane diterpenoid glucoside. Pierisjaponoside E represents the first example of a 9β-hydroxygrayan-1(10)-ene diterpenoid. All the isolated grayanane diterpenoid glucosides were evaluated for their analgesic activities in the acetic acid-induced writhing models in mice, and showed significant analgesic effects. Pierisjaponosides A and C-H, micranthanoside A, pieroside A, and craiobiosides A and B displayed significant analgesic effects with the writhe inhibition rates over 50% at a dose of 5.0 mg/kg. Pierisjaponoside E exhibited significant analgesic activities with the percentage inhibitions of 81.7%, 70.4%, and 52.1% at the doses of 5.0, 1.0, and 0.2 mg/kg, respectively. The preliminary structure-activity relationships of grayanane diterpenoid glucosides as potent analgesics were discussed, giving some clues to design novel analgesics.

Medication-assisted therapies for opioid use disorders in patients with chronic pain

Opioids have been used to treat pain and invoke pleasure for centuries. Modern scientific advancements have led to more potent, synthetic opioids. While certainly more effective in treating pain, they can also be much more addictive. Over the years the scientific community has developed a clearer understanding of the role opioid receptors play in causing and treating opioid use disorders (OUD) and we now know that OUD can develop in individuals taking opioids for "legitimate" pain. Current guidelines suggest that all prescribers (especially those prescribing opioids) be capable treating OUD. Pharmacological advances have led to a wide array of safe and effective treatment options to address OUDs. This paper will discuss the history of opioid development, what is known about the transition from analgesic uses to addiction and modern evidenced based treatment strategies to address OUDs.

Drug-specific differences in the ability of opioids to manage burn pain

Burn injury pain is a significant public health problem. Burn injury treatment has improved tremendously in recent decades. However, an unintended consequence is that a larger number of patients now survive more severe injuries, and face intense pain that is very hard to treat. Although many efforts have been made to find alternative treatments, opioids remain the most effective medication available. Burn patients are frequently prescribed opioids in doses and durations that are significantly higher and longer than standard analgesic dosing guidelines. Despite this, many continue to experience unrelieved pain. They are also placed at a higher risk for developing dependence and opioid use disorder. Burn injury profoundly alters the functional state of the immune system. It also alters the expression levels of receptor, effector, and signaling molecules within the spinal cord's dorsal horn. These alterations could explain the reduced potency of opioids. However, recent studies demonstrate that different opioids signal preferentially via differential signaling pathways. This ligand-specific signaling by different opioids implies that burn injury may reduce the antinociceptive potency of opioids to different degrees, in a drug-specific manner. Indeed, recent findings hint at drug-specific differences in the ability of opioids to manage burn pain early after injury, as well as differences in their ability to prevent or treat the development of chronic and neuropathic pain. Here we review the current state of opioid treatment, as well as new findings that could potentially lead to opioid-based pain management strategies that may be significantly more effective than the current solutions.

Long-term naturalistic follow-up of chronic pain in adults with prescription opioid use disorder

BACKGROUND

Chronic pain is common in patients with prescription opioid use disorder (OUD), and pain severity has been shown to predict opioid use for those with chronic pain. However, recent research suggests that focusing on pain status (i.e., the presence or absence of chronic pain) at treatment initiation may not reflect the clinical significance of pain over the long-term course of OUD. Reports of variability in chronic pain and its clinical significance over time have yet to be investigated in patients with prescription OUD. The present study examined variability in chronic pain status from entry into prescription OUD treatment through 3.5-year follow-up. Additionally, we examined the association between concurrent chronic pain and opioid use at three follow-up time points.

METHODS

This secondary analysis (N = 309) of a national, randomized, controlled trial of prescription OUD treatment used generalized estimating equations to assess variability in the prevalence of chronic pain from study entry to 3.5-year follow-up, and the association between chronic pain status and concurrent opioid use.

RESULTS

Fifty-three percent of participants reported variability in chronic pain status over time. The prevalence of chronic pain decreased from study entry through follow-up (aOR = 0.47, p < 0.001). Chronic pain was associated with increased opioid use at each follow-up assessment (aOR = 3.56, p < 0.001).

CONCLUSIONS

Chronic pain status may vary over time in those with prescription OUD, and chronic pain appears to be associated with concurrent opioid use. The present findings highlight the importance of assessing chronic pain throughout the course of prescription OUD.

Does bedtime matter among patients with chronic pain? A longitudinal comparison study

Introduction

Chronic pain patients frequently report having sleep disturbances and many tend to stay up during the night and then sleep into the day.

Objectives

This study was designed to compare a heterogeneous group of persons with chronic pain who reported typically going to bed between the hours of 9 pm and midnight with those who go to bed at other hours of the day and night.

Methods

Two hundred seventy-nine participants were divided between those who reported going to bed between the hours of 9 pm and midnight (N = 205) and those who reported having atypical bedtimes (N = 74) based on pre-post questionnaire data and average pain assessments from a smartphone pain application (app).

Results

Those individuals in the atypical bedtime group reported waking up more frequently and getting fewer hours sleep (P < 0.05). These individuals also reported significantly higher pain scores, activity interference, and taking more prescription opioid medication compared with those who had typical bedtimes (P < 0.05). Based on average 3-month daily assessments, those subjects with an atypical bedtime consistently reported more sleep disturbances, pain, activity interference, negative mood, and general worsening conditions over time, and elevated pain catastrophizing, pain-related disability, emotional distress scores, and more prescription medication for pain at 3-month follow-up (P < 0.01).

Conclusion

These results support the importance of providers asking patients with pain about what time they typically go to bed at night to gain a greater understanding of their lifestyle habits. Future studies are needed to further determine the importance of maintaining a typical bedtime among patients with chronic pain.

Core Outcome Measures in Preclinical Assessment of Candidate Analgesics

All preclinical procedures for analgesic drug discovery involve two components: 1) a “pain stimulus” (the principal independent variable), which is delivered to an experimental subject with the intention of producing a pain state; and 2) a “pain behavior” (the principal dependent variable), which is measured as evidence of that pain state. Candidate analgesics are then evaluated for their effectiveness to reduce the pain behavior, and results are used to prioritize drugs for advancement to clinical testing. This review describes a taxonomy of preclinical procedures organized into an “antinociception matrix” by reference to their types of pain stimulus (noxious, inflammatory, neuropathic, disease related) and pain behavior (unconditioned, classically conditioned, operant conditioned). Particular emphasis is devoted to pain behaviors and the behavioral principals that govern their expression, pharmacological modulation, and preclinical-to-clinical translation. Strengths and weaknesses are compared and contrasted for procedures using each type of behavioral outcome measure, and the following four recommendations are offered to promote strategic use of these procedures for preclinical-to-clinical analgesic drug testing. First, attend to the degree of homology between preclinical and clinical outcome measures, and use preclinical procedures with behavioral outcome measures homologous to clinically relevant outcomes in humans. Second, use combinations of preclinical procedures with complementary strengths and weaknesses to optimize both sensitivity and selectivity of preclinical testing. Third, take advantage of failed clinical translation to identify drugs that can be back-translated preclinically as active negative controls. Finally, increase precision of procedure labels by indicating both the pain stimulus and the pain behavior in naming preclinical procedures.

The association between severity of depression and prescription opioid misuse among chronic pain patients with and without anxiety: A cross-sectional study

BACKGROUND

In light of the increased rates of Prescription Opioid (PO) misuse and associated mortality in several developed countries in recent years, efforts have been made to identify populations who may be at increased risk for misuse of POs. Though the association between depression and PO misuse among pain patients is well documented, little is known regarding the effects of severity of depression on rates of misuse. In this study we explored rates of PO misuse among chronic pain patients screening positive for depression according to level of severity.

METHODS

Participants included chronic pain patients receiving POs (N = 554). All participants were screened for depression using the Patient Health Questionnaire (PHQ-9; cut-off scores of 5, 10, 15, and 20 for mild, moderate, moderate-severe and severe depression, respectively) and for opioid misuse using the Current Opioid Misuse Measure (COMM). Logistic regression analyses controlling for additional sociodemographic and clinical factors were conducted.

RESULTS

Participants who screened positive for depression were at significantly increased odds to screen positive for opioid misuse (Adjusted Odds Ratio (AOR) = 3.63; 95% Confidence Interval (CI) = 1.71-7.7) compared to those without depression. Severity of depression was significantly associated with increased odds for opioid misuse for moderate (AOR = 3.71; 95% CI = 1.01-13.76), moderate-severe (AOR = 6.28; 95% CI = 1.6-24.57) and severe (AOR = 14.66; 95% CI = 3.28-65.52) depression but not among those who screened positive for mild depression (AOR = 1.49; 95% CI = 0.39-5.68).

LIMITATIONS

Cross-sectional study.

CONCLUSIONS

Our results highlight the need to properly asses and address level of severity of co-morbid depression among chronic pain patients receiving POs.

Earlier surgery improves outcomes from painful chronic pancreatitis

The timing of surgery for painful chronic pancreatitis (CP) may affect outcomes.Clinical course, Izbicki pain scores, and pancreatic function were retrospectively compared and analyzed between patients undergoing either early or late surgery (< 3 or ≥ 3 years from diagnosis) for painful CP in a single center from 2007 to 2012.The early surgery group (n = 98) more frequently than the late group (n = 199) had abdominal pain with jaundice (22.4% vs 9.5%, P = .002) and pancreatic mass +/- ductal dilatation (47% vs 27%, P < .001), but less frequently abdominal pain alone (73.5% vs 85.9%, P = .009), ductal dilatation alone (31% vs 71%, P < .001), parenchymal calcification (91.8% vs 100%, P < .001) or exocrine insufficiency (60% vs 72%, P = .034); there were no other significant differences. The early group had longer hospital stay (14.4 vs 12.2 days, P = .009), but no difference in complications. Significantly greater pain relief followed early surgery (complete 69% vs 47%, partial 22% vs 37%, none 8% vs 16%, P = .01) with lower rates of exocrine (60% vs 80%, P = .005) and endocrine insufficiency (36% vs 53%, P = .033).Our data indicate that early surgery results in higher rates of pain relief and pancreatic sufficiency than late surgery for chronic pancreatitis patients. Frey and Berne procedures showed better results than other surgical procedures.

The effect of ampule size of fentanyl on perioperative intravenous opioid dosing

Background and Aims:

There are limited data on the effect of ampule size on drug dosing. The objective of this study is to determine the effect of ampule size on perioperative opioid dosing and post-anesthesia care unit (PACU) outcomes.

Material and Methods:

This was a retrospective review of patients undergoing robotically assisted laparoscopic radical prostatectomy before and after a 5-ml fentanyl ampule was discontinued. The primary outcome was intraoperative opioid administration divided into fentanyl at induction of anesthesia, total fentanyl, and total opioid. Secondary outcomes observed in PACU included the opioid administered, visual analog scale (VAS) pain scores, postoperative nausea and vomiting, and length of stay in PACU.

Results:

A total of 100 patients (50 PRE and 50 POST) were included. In the intraoperative opioid administration, mean (SD) of fentanyl at induction was 117.0 (49.3) in PRE group and 85.0 (35.4) μg in POST group (P < 0.01). The total fentanyl requirement was 247.0 (31.0) in PRE group and 158.5 (85.1) μg in POST group (P < 0.01). The total opioid in intravenous morphine equivalents (IVME) was 34.1 (5.8) in PRE group and 23.2 (6.8) mg in POST group (P < 0.01). Among the secondary outcomes, mean (SD) of IVME of opioid was 7.7 (8.2) in PRE group and 9.9 (8.1) mg in POST group (P = 0.18). The VAS pain score on arrival was 0.7 (1.4) in PRE group and 3.8 (3.3) in POST group (P < 0.01). The cumulative VAS pain score was 2.3 (2.0) in PRE group and 3.3 (2.2) in POST group (P < 0.01). The length of stay was significantly more in POST group, 193.8 (75.8) minutes, as compared with PRE group, 138.6 (61.0) minutes (P < 0.01).

Conclusions:

A change in the ampule size significantly affected intraoperative dosing, PACU pain scores, and PACU length of stay in patients undergoing robotically assisted laparoscopic radical prostatectomy under general anesthesia. This was explained by clinician's desire to conserve the drug and avoid the complex process of narcotic waste disposal.

Evaluation and comparison of tools for diagnosing problematic prescription opioid use among chronic pain patients

Prescription opioid medications are commonly used for the treatment of chronic pain. Assessments of problematic opioid use among pain patients are inconsistent across studies, partially due to differences between various measures. Therefore, the most appropriate measure to use is often unclear. In this study we assessed problematic opioid use in a sample of 551 individuals receiving treatment for chronic pain, using three questionnaires: the Alcohol Use Disorder and Associated Disabilities Interview Schedule - Fourth Edition (AUDADIS-IV), the Current Opioid Misuse Measure (COMM) questionnaire and Portenoy's criteria (PC). These questionnaires yielded discordant positive rates of problematic use: 52.6%, 28.7%, and 17.1%, respectively, which did not change substantially when excluding AUDADIS-IV criteria of physical symptoms of tolerance and withdrawal. Although these three questionnaires share some statistically correlated content-based congruent questions, positive response rates to them were significantly different based on construction features, including questionnaires' referred time-frame, wording of questions and response alternatives. The findings of the present study illustrate strengths and limitations of the AUDADIS-IV, COMM and PC in diagnosing problematic opioid use in a population of adults suffering from chronic pain, and highlight the importance of recognizing and addressing specific questionnaire and question-related differences when identifying problematic opioid use in this population.

Opioid Reduction Following Interventional Procedures for Chronic Pain: A Synthesis of the Evidence

The past decade has witnessed the tremendous growth of procedures to treat chronic pain, which has resulted in increased third-party scrutiny. Although most of these procedures appear to be associated with significant pain relief, at least in the short and intermediate term, their ability to improve secondary outcome measures, including function and work status is less clear-cut. One of these secondary outcome measures that has garnered substantial interest in the pain and general medical communities is whether interventions can reduce opioid intake, which is associated with significant risks that in most cases outweigh the benefits in the long term. In the article, we examine whether procedural interventions for chronic pain can reduce opioid intake. Most studies that have examined analgesic reduction as a secondary outcome measure have not separated opioid and nonopioid analgesics, and, among those studies that have, few have demonstrated between-group differences. Reasons for failure to demonstrate opioid reduction can be broadly classified into procedural, design-related, clinical, psychosocial, biological, and pharmacological categories, all of which are discussed. In the future, clinical trials in which this outcome is examined should be designed to evaluate this, at least on a preliminary basis.