Neonatal Abstinence Syndrome: A Review of Treatment in the Neonatal Intensive Care Unit

Background

Neonatal abstinence syndrome (NAS) is a collection of symptoms that neonates may experience following antenatal exposure to substances that induce withdrawal. Optimal management remains unknown, and there is variation in management and outcomes.

Objectives

To describe the management, length of hospitalization, and adverse events in near-term and full-term neonates with NAS for whom treatment (pharmacotherapy and/or supportive care) was initiated in the neonatal intensive care unit (NICU).

Methods

A chart review was conducted of neonates admitted to the NICU of Surrey Memorial Hospital, Surrey, British Columbia, who received treatment for NAS between September 1, 2016, and September 1, 2021.

Results

A total of 48 neonates met the inclusion criteria. Opioids represented the most frequent type of antenatal exposure. Polysubstance exposures occurred in 45 (94%) of the neonates. Morphine was given to 29 (60%) of the neonates, and phenobarbital to 6 (13%); 5 of these neonates received both medications. The average duration of morphine treatment was 14 days, and the average length of hospitalization (all patients) was 16 days. All of the neonates experienced adverse events; in particular, 9 (30%) of the 30 who received pharmacotherapy were too sedated to feed, compared with 0% of the 18 with no pharmacotherapy.

Conclusions

The common finding of polysubstance antenatal exposure, involving predominantly opioids, was associated with scheduled morphine pharmacotherapy for the majority of patients, prolonged hospitalization, and frequent adverse events. Pharmacotherapy for NAS was associated with levels of sedation that interfered with feeding in neonates.

Comparative Study Between Intravenous Patient-Controlled Analgesia Morphine and Computerized Ambulatory Delivery Device Epidural Morphine for Post Operative Analgesia for Nuss Procedure in Pectus Excavatum: A Retrospective Analysis

BACKGROUND

Pectus deformities are commonly seen in chest wall deformities among the pediatric age group. Pectus deformities occur due to defective growth of the sternum and its surrounding cartilage. The Nuss procedure is the technique of choice for correcting the deformity surgically which includes placing a convex bar under the sternum without resection or injury to costal cartilages. Adequate pain control is utmost to improve wound healing, patient satisfaction, short hospital stays, and decrease the financial burden on attendants. Therefore, it is necessary to investigate which analgesic method is more advantageous for the Nuss procedure.

OBJECTIVE

To compare the analgesic effects of intravenous patient-controlled analgesia (IVPCA) morphine versus computerized ambulatory delivery device (CADD) epidural morphine on acute post-operative pain management in Nuss procedures.

METHODS

A retrospective study was done at Rajiv Gandhi Cancer and Research Hospital, New Delhi from 2015 to 2020 to assess the efficacy and safety between IVPCA morphine and CADD epidural for post-operative analgesia following pectus excavatum repair. A total of 34 cases of Nuss procedures were taken with 17 cases in each group. Group 1 (intravenous PCA morphine) was given 39 ml normal saline + 6 ml morphine (total 45 ml, 2 mg/ml morphine), set at demand dose 0.5 ml, i.e. 1 mg, lockout interval 7 minutes, doses per hour was six and Group 2 (CADD epidural morphine) was given 42 ml normal saline + 3 ml morphine (1 mg/ml morphine) with continuous infusion at the rate of 0.5 ml/hr. Demand dose 0, lockout interval nil. Visual analog pain scores using a scale of 0-10 and Ramsay Sedation Score (RSS) scores were obtained on arrival at the post-anesthesia care unit, at 12, 24, 48, and 72 hours throughout the subsequent hospital stay.

RESULTS

This study yielded positive information about our experience with the pectus post-operative pain management. The mean visual analog scale (VAS) score was lower in Group 1 compared to Group 2 but significantly different at 12 and 72 hours only. The mean RSS score was comparable between groups. The mean hospital stay (days) and requirement of rescue analgesia doses were 3.47±0.51 and 0.12±0.33 in Group 1 and 4.76±0.44, 0.59±1.12 in Group 2.

CONCLUSION

 Both IVPCA morphine and CADD morphine were effective in controlling post-surgical pain in the Nuss procedure, but IVPCA morphine was better as compared to CADD morphine in this regard because it was noninvasive, safe, and cost-effective with non-significant complications.

Ultrasound-guided anterior suprascapular nerve block versus interscalene brachial plexus block for arthroscopic shoulder surgery: A randomised controlled study

Background and Aims

The interscalene brachial plexus block (ISB) affects the phrenic nerve, resulting in hemi-diaphragmatic paresis (HDP) and, possibly, respiratory distress. Suprascapular nerve block via an anterior approach (SSB-A) is performed more distally at the level of the trunk of the brachial plexus and, thus, may spare the phrenic nerve. This study compares the analgesic efficacy and decline of hemi-diaphragmatic excursion (HDE) following ultrasound (US)-guided SSB-A versus ISB for arthroscopic shoulder surgery.

Methods

This study was conducted on 60 adult participants undergoing arthroscopic shoulder surgery under general anaesthesia. Both US-guided SSB-A (n = 30) and ISB (n = 30) were performed with a combination of 10 ml bupivacaine (0.5%) and 4 mg dexamethasone. The primary objective was to compare the duration of analgesia (time to first rescue analgesia), and secondary objectives were to compare 24-h postoperative numerical rating scale (NRS) scores, 24-h morphine consumption and post block change in HDE, and pulmonary function tests (PFTs) between the two groups. For analysing intergroup differences of NRS, HDE and PFT; Pearson's Chi-squared test or Fisher's exact test, unpaired t test, and Mann-Whitney U test were used. For intragroup differences, paired t test was used. A P value <0.05 was considered significant.

Results

The duration of analgesia (mean ± Standard Deviation) was similar in two groups (SSB-A = 1,345 ± 182 min, ISB = 1,375 ± 156 min; P = 0.8). The reduction in HDE was significantly greater in the ISB group (44%) than in the SSB-A group (10%). Pulmonary function was better preserved in the SSB-A group.

Conclusion

Compared to ISB, SSB-A has a similar analgesic efficacy for arthroscopic shoulder surgeries, but it is superior in preserving diaphragmatic function and pulmonary function.

Etoricoxib Can Reduce Post-Operative Morphine Consumption and Pain Score in Patients Undergoing Lumbar Laminectomy Compare to Acetaminophen: A Randomized Trial

STUDY DESIGN

Randomized controlled trial.

OBJECTIVES

This prospective trial aimed to compare the effectiveness of etoricoxib and acetaminophen in terms of post-operative morphine consumption and pain score in patients undergoing lumbar laminectomy.

METHODS

Forty lumbar-laminectomy patients aged between 18 and 50 years were enrolled, randomized, and allocated into either the etoricoxib group or the acetaminophen group. The measures assessed were the amount of morphine consumed and pain visual analog score (VAS) at 12, 24, and 48 hours after surgery. Adverse events were recorded.

RESULTS

Patients in the etoricoxib group had statistically significantly lower morphine consumption than those in the acetaminophen group at 12 hours (P-value = .006), 24 hours (P-value = .006) and 48 hours (P-value = .011). Patients in the etoricoxib group had lower VAS scores than those in the acetaminophen group at 0, 12, 24, 48 hours, the difference being statistically significant at 48 hours (P < .001).

CONCLUSIONS

Compared to acetaminophen, etoricoxib can significantly reduce post-operative morphine consumption and improve the pain score at 12, 24, and 48 hours.

Low Current Intensity Plus an Ineffective Dose of Morphine Affect Conditioning Place Preference Through Different Pathways in the Lateral Habenula

Background

The involvement of lateral habenula and the ineffective dose of morphine on reward-related learning and memory is less well-known. This study looked into the effects of electrical stimulation, GABAB receptor blockade, and a combination of both with morphine on conditioned place preference.

Materials and Methods

In this experiment, male rats were anesthetized with ketamine/xylazine (six rats in each group). A 5-day biased conditioned place preference paradigm was used for the behavioral test. The effects of electrical stimulation and phaclofen plus a low dose of morphine on the acquisition and expression phases were examined during conditioning sessions and before the test phase, respectively.

Results

The conditioning scores were reduced by antagonist injection during the acquisition phase. Interestingly, different intensities exhibited opposite effects on the acquisition phase. Conditioned place preference scores during the acquisition phase were significantly induced by 25 μA electrical stimulation, while conditioning scores were suppressed by electrical stimulation at 150 μA. Phaclofen (2 μg/rat) combined with high intensity induced aversion during the acquisition phase, while inhibiting expression. In contrast, high intensity with phaclofen (1 μg/rat) inhibited only the acquisition session. However, low intensity during the acquisition phase had an additive effect that was prevented by pretreatment with phaclofen (2 μg/rat), but this response was modified by the antagonist's low dose.

Conclusions

A behavioral technique called conditioned place preference is frequently used to evaluate learning that is related to rewards. Therefore, lateral habenula electrical stimulation and phaclofen plus morphine could affect place preference through the involvement of the reward system.

Effects of the Co-Administration of Morphine and Lipopolysaccharide on Toll-Like Receptor-4/Nuclear Factor Kappa β Signaling Pathway of MDA-MB-231 Breast Cancer Cells

Background

The Toll-like receptor 4 (TLR4) gene promotes migration in adenocarcinoma cells. Morphine is an agonist for TLR4 that has a dual role in cancer development. The promoter or inhibitor role of morphine in cancer progression remains controversial. This study aims to evaluate the effects of morphine on the TLR4, myeloid differentiation primary response protein 88-dependent (MyD88), and nuclear factor-kappa B (NF-κB) expressions in the human MDA-MB-231 breast cancer cell line.

Materials and Methods

The cells were examined after 24 hours of incubation with morphine using the Boyden chamber system. TLR4, MyD88, and NF-κB mRNA expressions were assessed using quantitative real-time polymerase chain reaction (RT-PCR). The concentration of interleukin-2 beta was also measured using the ELISA assay.

Results

According to the findings, three doses of morphine (0.25, 1.25, and 0.025 μM) increased the expression of the TLR4 and NF-κB genes, whereas no significant change was observed in the mRNA expression of MyD88. Furthermore, treatment with morphine and lipopolysaccharide (LPS) significantly decreased the expression of TLR4, MyD88, and NF-κB. However, no significant change was observed in interleukin 2 beta concentration.

Conclusions

These findings confirmed the excitatory effects of morphine on TRL4 expression and the MYD88 signaling pathway in vitro.

Opioid Analgesics after Bariatric Surgery: A Scoping Review to Evaluate Physiological Risk Factors for Opioid-Related Harm

The persisting use of opioids following bariatric surgery has emerged as a prevalent complication, heightening the probability of opioid-related harm (ORM), such as opioid-related fatalities and prescription opioid use disorder (OUD). A comprehensive review of PubMed literature from 1990 to 2023 was conducted to pinpoint physiological influences on postoperative ORM. As a result, we found that patients undertaking bariatric operations often exhibit an inherently higher risk for substance use disorders, likely attributable to genetic predisposition and related neurobiological changes that engender obesity and addiction-like tendencies. Furthermore, chronic pain is a common post-bariatric surgery complaint, and the surgical type impacts opioid needs, with increased long-term opioid use after surgeries. Additionally, the subjective nature of pain perception in patients with obesity can distort pain reporting and the corresponding opioid prescription both before and after surgery. Furthermore, the postoperative alterations to the gastrointestinal structure can affect the microbiome and opioid absorption rates, resulting in fluctuating systemic exposure to orally ingested opioids. The prospect of ORM development post-bariatric surgery appears amplified due to a preexisting susceptibility to addictive habits, surgically induced pain, modified gut-brain interaction and pain management and the changed pharmacokinetics post-surgery. Further research is warranted to clarify these potential risk variables for ORM, specifically OUD, in the bariatric population.

Activation of the mu-delta opioid receptor heteromers blocks morphine rewarding effects

BACKGROUND

Evidence has accumulated demonstrating the existence of opioid receptor heteromers and recent data suggest that targeting these heteromers could reduce opioid side effects while retaining therapeutic effects. Indeed, CYM51010 characterised as a MOR (mu opioid receptor)/DOR (delta opioid receptor) heteromers preferring agonist promoted antinociception comparable to morphine but with less tolerance. In the perspective of developing these new classes of pharmacological agents, data on their putative side effects are mandatory.

METHODS

Therefore, in this study, we investigated the effects of CYM51010 in different models related to drug addiction in mice including behavioural sensitization, conditioned place preference and withdrawal.

RESULTS

We found that, like morphine, CYM51010 promoted acute locomotor activity as well as psychomotor sensitization and rewarding effect. However, it induced less physical dependence than morphine. We also investigated the ability of CYM51010 to modulate some morphine-induced behaviour. Whereas CYM51010 was unable to block morphine-induced physical dependence, it blocked reinstatement of an extinguished morphine induced-conditioned place preference.

CONCLUSIONS

Altogether, our results reveal that targeting MOR-DOR heteromers could represent a promising strategy to block morphine reward.

A Novel UHPLC-MS/MS Method for the Quantification of Seven Opioids in Different Human Tissues

BACKGROUND

Opioids are considered the cornerstone of pain management: they show good efficacy as a first-line therapy for moderate to severe cancer pain. Since pharmacokinetic/pharmacodynamic information about the tissue-specific effect and toxicity of opioids is still scarce, their quantification in post-mortem autoptic specimens could give interesting insights.

METHODS

We describe an ultra-high-performance liquid chromatography coupled with tandem mass spectrometry method for the simultaneous quantification of methadone, morphine, oxycodone, hydrocodone, oxymorphone, hydromorphone and fentanyl in several tissues: liver, brain, kidney, abdominal adipose tissue, lung and blood plasma. The presented method has been applied on 28 autoptic samples from different organs obtained from four deceased PLWH who used opioids for palliative care during terminal disease.

RESULTS

Sample preparation was based on tissue weighing, disruption, sonication with drug extraction medium and a protein precipitation protocol. The extracts were then dried, reconstituted and injected onto the LX50 QSight 220 (Perkin Elmer, Milan, Italy) system. Separation was obtained by a 7 min gradient run at 40 °C with a Kinetex Biphenyl 2.6 µm, 2.1 × 100 mm. Concerning the analyzed samples, higher opioids concentrations were observed in tissues than in plasma. Particularly, O-MOR and O-COD showed higher concentrations in kidney and liver than other tissues (>15-20 times greater) and blood plasma (>100 times greater).

CONCLUSIONS

Results in terms of linearity, accuracy, precision, recovery and matrix effect fitted the recommendations of FDA and EMA guidelines, and the sensitivity was high enough to allow successful application on human autoptic specimens from an ethically approved clinical study, confirming its eligibility for post-mortem pharmacological/toxicological studies.

Morphine pharmacokinetics and opioid transporter expression at the blood-retina barrier of male and female mice

Opioids are effective analgesics for treating moderate to severe pain, however, their use must be weighed against their dangerous side effects. Investigations into opioid pharmacokinetics provide crucial information regarding both on- and off-target drug effects. Our recent work showed that morphine deposits and accumulates in the mouse retina at higher concentrations than in the brain upon chronic systemic exposure. We also found reduced retinal expression of P-glycoprotein (P-gp), a major opioid extruder at the blood-brain barrier (BBB). Here, we systematically interrogated the expression of three putative opioid transporters at the blood-retina barrier (BRB): P-gp, breast cancer resistance protein (Bcrp) and multidrug resistance protein 2 (Mrp2). Using immunohistochemistry, we found robust expression of P-gp and Bcrp, but not Mrp2, at the inner BRB of the mouse retina. Previous studies have suggested that P-gp expression may be regulated by sex hormones. However, upon acute morphine treatment we found no sex differences in morphine deposition levels in the retina or brain, nor on transporter expression in the retinas of males and females with a high or low estrogen:progesterone ratio. Importantly, we found that P-gp, but not Bcrp, expression significantly correlated with morphine concentration in the retina, suggesting P-gp is the predominant opioid transporter at the BRB. In addition, fluorescence extravasation studies revealed that chronic morphine treatment did not alter the permeability of either the BBB or BRB. Together, these data suggest that reduced P-gp expression mediates retinal morphine accumulation upon systemic delivery, and in turn, potential effects on circadian photoentrainment.

Peripheralization Strategies Applied to Morphinans and Implications for Improved Treatment of Pain

Opioids are considered the most effective analgesics for the treatment of moderate to severe acute and chronic pain. However, the inadequate benefit/risk ratio of currently available opioids, together with the current 'opioid crisis', warrant consideration on new opioid analgesic discovery strategies. Targeting peripheral opioid receptors as effective means of treating pain and avoiding the centrally mediated side effects represents a research area of substantial and continuous attention. Among clinically used analgesics, opioids from the class of morphinans (i.e., morphine and structurally related analogues) are of utmost clinical importance as analgesic drugs activating the mu-opioid receptor. In this review, we focus on peripheralization strategies applied to N-methylmorphinans to limit their ability to cross the blood-brain barrier, thus minimizing central exposure and the associated undesired side effects. Chemical modifications to the morphinan scaffold to increase hydrophilicity of known and new opioids, and nanocarrier-based approaches to selectively deliver opioids, such as morphine, to the peripheral tissue are discussed. The preclinical and clinical research activities have allowed for the characterization of a variety of compounds that show low central nervous system penetration, and therefore an improved side effect profile, yet maintaining the desired opioid-related antinociceptive activity. Such peripheral opioid analgesics may represent alternatives to presently available drugs for an efficient and safer pain therapy.

Differential Effects of Cocaine and Morphine on the Diurnal Regulation of the Mouse Nucleus Accumbens Proteome

Substance use disorders are associated with disruptions in sleep and circadian rhythms that persist during abstinence and may contribute to relapse risk. Repeated use of substances such as psychostimulants and opioids may lead to significant alterations in molecular rhythms in the nucleus accumbens (NAc), a brain region central to reward and motivation. Previous studies have identified rhythm alterations in the transcriptome of the NAc and other brain regions following the administration of psychostimulants or opioids. However, little is known about the impact of substance use on the diurnal rhythms of the proteome in the NAc. We used liquid chromatography coupled to tandem mass spectrometry-based quantitative proteomics, along with a data-independent acquisition analysis pipeline, to investigate the effects of cocaine or morphine administration on diurnal rhythms of proteome in the mouse NAc. Overall, our data reveal cocaine and morphine differentially alter diurnal rhythms of the proteome in the NAc, with largely independent differentially expressed proteins dependent on time-of-day. Pathways enriched from cocaine altered protein rhythms were primarily associated with glucocorticoid signaling and metabolism, whereas morphine was associated with neuroinflammation. Collectively, these findings are the first to characterize the diurnal regulation of the NAc proteome and demonstrate a novel relationship between the phase-dependent regulation of protein expression and the differential effects of cocaine and morphine on the NAc proteome. The proteomics data in this study are available via ProteomeXchange with identifier PXD042043.

Predicting favorable response to intravenous morphine in pediatric critically ill cardiac patients

INTRODUCTION

Analgesia and sedation are integral to the care of critically ill children. However, the choice and dose of the analgesic or sedative drug is often empiric, and models predicting favorable responses are lacking. We aimed to compute models to predict a patient's response to intravenous morphine.

METHODS

We retrospectively analyzed data from consecutive patients admitted to the Cardiac Intensive Care Unit (January 2011- January 2020) who received at least one intravenous bolus of morphine. The primary outcome was a decrease in the State Behavioral Scale (SBS) ≥1 point; the secondary outcome was a decrease in the heart rate Z-score (zHR) at 30 minutes. Effective doses were modeled using logistic regression, Lasso regression, and random forest modeling.

RESULTS

A total of 117,495 administrations of intravenous morphine among 8,140 patients (median age 0.6 years [interquartile range [IQR] 0.19, 3.3]) were included. The median morphine dose was 0.051 mg/kg (IQR 0.048, 0.099) and the median 30-day cumulative dose was 2.2 mg/kg (IQR 0.4, 15.3). SBS decreased following 30% of doses, did not change following 45%, and increased following 25%. The zHR significantly decreased after morphine administration (median delta-zHR -0.34 (IQR-1.03, 0.00), P<0.001). A concomitant infusion of propofol, higher prior-30-day cumulative dose, being invasively ventilated and/or on vasopressors were associated with favorable response to morphine. Higher morphine dose, higher zHR pre-morphine, an additional analgosedation bolus ±30 minutes around the index bolus, a concomitant ketamine or dexmedetomidine infusion, and showing signs of withdrawal syndrome were associated with unfavorable response. Logistic regression (area under the receiver operating characteristic [ROC] curve [AUC] 0.900) and machine learning models (AUC 0.906) performed comparably, with a sensitivity of 95%, specificity of 71%, and negative predictive value of 97%.

CONCLUSIONS

Statistical models identify 95% of effective intravenous morphine doses in pediatric critically ill cardiac patients, while incorrectly suggesting an effective dose in 29% of cases. This work represents an important step towards computer-aided, personalized clinical decision support tool for sedation and analgesia in ICU patients.

Detection of Three Opioids (Morphine, Codeine and Methadone) and Their Metabolites (6-Monoacetylmorphine and 2-Ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine) in Larvae of Lucilia sericata Species by UHPLC-TF-MS and Validation

Insects on corpses could be a useful tool for the detection of exogenous substances such as drugs of abuse. The identification of exogenous substances in carrion insects is critical for proper estimation of the postmortem interval. It also provides information about the deceased person that may prove useful for forensic purposes. High-performance liquid chromatography coupled with Fourier transform mass spectrometry is a highly sensitive analytical technique that can identify substances even at very low concentrations, such as in the case of searching for exogenous substances in larvae. In this paper, a method is proposed for the identification of morphine, codeine, methadone, 6-monoacetylmorphine (6-MAM) and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in the larvae of Lucilia sericata, a common carrion fly widely distributed in temperate areas of the world. The larvae, which were reared on a pig meat substrate, were killed once they reached their third stage by immersion in hot water at 80 °C and aliquoted into 400 mg samples. The samples were fortified with 5 ng of morphine, methadone and codeine. After solid-phase extraction, the samples were processed with a liquid chromatograph coupled to a Fourier transform mass spectrometer. This qualitative method has been validated and tested on larvae from a real case. The results lead to the correct identification of morphine, codeine, methadone and their metabolites. This method could prove useful in cases where toxicological analysis must be conducted on highly decomposed human remains, where biological matrices are very limited. Furthermore, it could help the forensic pathologist to better estimate the time of death, as the growth cycle of carrion insects can undergo changes if exogenous substances are taken.

Intranasal dexmedetomidine with morphine or tramadol: A comparative study of effects on alfaxalone requirements for anesthesia in cats

Background and Aim

Intranasal (IN) sedatives provide a non-invasive route for premedication drug administration. This study compared the cardiorespiratory and sparing effects of IN dexmedetomidine combined with morphine (DM) or tramadol (DT) on alfaxalone requirements for anesthesia induction in cats.

Materials and Methods

Twenty-four cats were randomly assigned to three groups: Dexmedetomidine combined morphine (IN dexmedetomidine 20 μg/kg plus 0.2 mg/kg morphine), DT (IN dexmedetomidine 20 μg/kg plus 1 mg/kg tramadol), or control (no premedication). The intravenous dose of 1% alfaxalone for endotracheal intubation was recorded with sedation scores, cardiorespiratory parameters (heart rate and respiration rate), and side effects.

Results

Both DM and DT were associated with significantly higher sedation scores than baseline, and sedation scores were found to be highest 20 min after premedication. Sedation scores were comparable between DM and DT groups. Side effects, including hypersalivation, vomiting, and pupillary dilation, were observed in the DM and DT groups. The dosage of alfaxalone required in the DM group (1.5 ± 0.3 mg/kg) was comparable to that of the DT group (2.0 ± 0.6 mg/kg, p = 0.0861), and both groups required significantly less alfaxalone than the control group (3.0 ± 0.6 mg/kg; p < 0.01). Heart and respiratory rates were comparable between the DM and DT groups. Duration of anesthesia in the control group (11 ± 4 min) was significantly shorter than in the DM (29 ± 5 min, p = 0.0016) and DT (38 ± 14 min, p < 0.001) groups.

Conclusion

Intranasal administration of DM or DT produces good sedation and offers an alternative, non-invasive route for cats undergoing general anesthesia.

Knowledge, Perception and Barriers to Cancer Pain Management among Doctors in Malaysia

Background

Pain remains common in people living with advanced cancer and is often inadequately managed. This study was designed to assess knowledge, perceptions and barriers to morphine use in cancer pain management among doctors in Malaysia.

Methods

Doctors from multiple disciplines in a general hospital were invited to complete a 39-item self-reported questionnaire between November 2020 and December 2020. Each question was based on a 5-point Likert scale (1 = strongly disagree; 5 = strongly agree). 'Agree' and 'strongly agree' were considered correct or positive responses, except for nine questions worded in the opposite direction. Associations between variables were confirmed using Pearson's chi-squared and Fisher's exact tests.

Results

Most respondents were house officers (206/321; 64.2%) with less than two years of service, followed by medical officers (68/321; 21.2%) and specialists (47/321; 14.6%). Only 7.2% of the respondents had received formal palliative care training before the study. Of the respondents, 73.5% were aware of the World Health Organization (WHO) analgaesic ladder, 60.7% were correct on oral morphine as the first line for moderate to severe cancer pain treatment and 91.9% knew the need to add rescue morphine for breakthrough pain. Additionally, 34.0% (P < 0.001) perceived morphine use caused addiction, 57.9% (n = 186) expressed fear of respiratory depression and 18.3% of medical officers and specialists perceived limited access and a maximum dose to prescribe. There was a significant difference in knowledge and perception between junior doctors and senior clinicians. The majority strongly agreed and agreed that there were inadequate training opportunities in cancer pain management.

Conclusion

Inconsistent knowledge and negative perceptions of cancer pain management among doctors were demonstrated in this study.

Microglia NLRP3 Inflammasome and Neuroimmune Signaling in Substance Use Disorders

During the last decade, substance use disorders (SUDs) have been increasingly recognized as neuroinflammation-related brain diseases. Various types of abused drugs (cocaine, methamphetamine, alcohol, opiate-like drugs, marijuana, etc.) can modulate the activation status of microglia and neuroinflammation levels which are involved in the pathogenesis of SUDs. Several neuroimmune signaling pathways, including TLR/NF-кB, reactive oxygen species, mitochondria dysfunction, as well as autophagy defection, etc., have been implicated in promoting SUDs. Recently, inflammasome-mediated signaling has been identified as playing critical roles in the microglia activation induced by abused drugs. Among the family of inflammasomes, NOD-, LRR-, and pyrin-domain-containing protein 3 (NLRP3) serves the primary research target due to its abundant expression in microglia. NLRP3 has the capability of integrating multiple external and internal inputs and coordinately determining the intensity of microglia activation under various pathological conditions. Here, we summarize the effects of abused drugs on NLRP3 inflammasomes, as well as others, if any. The research on this topic is still at an infant stage; however, the readily available findings suggest that NLRP3 inflammasome could be a common downstream effector stimulated by various types of abused drugs and play critical roles in determining abused-drug-mediated biological effects through enhancing glia-neuron communications. NLRP3 inflammasome might serve as a novel target for ameliorating the development of SUDs.

Challenges of Access to Oral Morphine Medicine: Palliative Care at a Crossroads for Cancer Patients in Ethiopia

Ethiopia registers 77,352 new cases of cancer and 51,865 deaths every year, and the number is showing an increasing trend year to year. Despite the importance of providing palliative care, the country has a long way to go to match the needs of and provide relief for patients with cancer. The promotion and expansion of palliative care services is challenged by a number of problems, among which lack of access to pain-relieving medicine is one of, if not the main, problems raised by health professionals and by various parties involved in health care. Oral morphine is effective and the preferred pain-relieving medicine with tolerable side effects, especially when given by titrating the dose. However, Ethiopia is facing a shortage of oral morphine in health-care facilities and other places where the product is needed. Unless an immediate solution is sought to address the inaccessibility of this medicine, the problem of palliative care will be pronounced and the suffering of patients will continue.

Activation of neurons and satellite glial cells in the DRG produces morphine-induced hyperalgesia

Activation of neurons and glial cells in the dorsal root ganglion is one of the key mechanisms for the development of hyperalgesia. The aim of the present study was to examine the role of neuroglial activity in the development of opioid-induced hyperalgesia. Male rats were treated with morphine daily for 3 days. The resultant phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 in the dorsal root ganglion was analyzed by immunohistochemistry and Western blotting. Pain hypersensitivity was analyzed using behavioral studies. The amount of cytokine expression in the dorsal root ganglion was also analyzed. Repeated morphine treatment induced hyperalgesia and marked induction of phosphorylated ERK1/2 in the neurons and satellite glial cells on day 3. An opioid receptor antagonist, toll like receptor-4 inhibitor, MAP/ERK kinase (MEK) inhibitor and gap junction inhibitor inhibited morphine-induced hyperalgesia and ERK1/2 phosphorylation. Morphine treatment induced alteration of cytokine expression, which was inhibited by the opioid receptor antagonist, toll like receptor-4 inhibitor, MEK inhibitor and gap junction inhibitor. Dexamethasone inhibited morphine-induced hyperalgesia and ERK1/2 phosphorylation after morphine treatment. The peripherally restricted opioid receptor antagonist, methylnaltrexone, inhibited hyperalgesia and ERK1/2 phosphorylation. Morphine activates ERK1/2 in neurons and satellite glial cells in the dorsal root ganglion via the opioid receptor and toll like receptor-4. ERK1/2 phosphorylation is gap junction-dependent and is associated with the alteration of cytokine expression. Inhibition of neuroinflammation by activation of neurons and glia might be a promising target to prevent opioid-induced hyperalgesia.

Phenytoin Decreases Pain-like Behaviors and Improves Opioid Analgesia in a Rat Model of Neuropathic Pain

Neuropathic pain remains a clinical challenge due to its complex and not yet fully understood pathomechanism, which result in limited analgesic effectiveness of the management offered, particularly for patients with acute, refractory neuropathic pain states. In addition to the introduction of several modern therapeutic approaches, such as neuromodulation or novel anti-neuropathic drugs, significant efforts have been made in the repurposing of well-known substances such as phenytoin. Although its main mechanism of action occurs at sodium channels in excitable and non-excitable cells and is well documented, how the drug affects the disturbed neuropathic interactions at the spinal cord level and how it influences morphine-induced analgesia have not been clarified, both being crucial from a clinical perspective. We demonstrated that single and repeated systemic administrations of phenytoin decreased tactile and thermal hypersensitivity in an animal model of neuropathic pain. Importantly, we observed an increase in the antinociceptive effect on thermal stimuli with repeated administrations of phenytoin. This is the first study to report that phenytoin improves morphine-induced antinociceptive effects and influences microglia/macrophage activity at the spinal cord and dorsal root ganglion levels in a neuropathic pain model. Our findings support the hypothesis that phenytoin may represent an effective strategy for neuropathic pain management in clinical practice, particularly when combination with opioids is needed.

Chronic Morphine Modulates PDGFR-β and PDGF-B Expression and Distribution in Dorsal Root Ganglia and Spinal Cord in Male Rats

The analgesic effect of opioids decreases over time due to the development of analgesic tolerance. We have shown that inhibition of the platelet-derived growth factor beta (PDGFR-β) signaling eliminates morphine analgesic tolerance in rats. Although the PDGFR-β and its ligand, the platelet-derived growth factor type B (PDGF-B), are expressed in the substantia gelatinosa of the spinal cord (SG) and in the dorsal root ganglia (DRG), their precise distribution within different cell types of these structures is unknown. Additionally, the impact of a tolerance-mediating chronic morphine treatment, on the expression and distribution of PDGF-B and PDGFR-β has not yet been studied. Using immunohistochemistry (IHC), we found that in the spinal cord, PDGFR-β and PDGF-B were expressed in neurons and oligodendrocytes and co-localized with the mu-opioid receptor (MOPr) in opioid naïve rats. PDGF-B was also found in microglia and astrocytes. Both PDGFR-β and PDGF-B were detected in DRG neurons but not in spinal primary afferent terminals. Chronic morphine exposure did not change the cellular distribution of PDGFR-β or PDGF-B. However, PDGFR-β expression was downregulated in the SG and upregulated in the DRG. Consistent with our previous finding that morphine caused tolerance by inducing PDGF-B release, PDGF-B was upregulated in the spinal cord. We also found that chronic morphine exposure caused a spinal proliferation of oligodendrocytes. The changes in PDGFR-β and PDGF-B expression induced by chronic morphine treatment suggest potential mechanistic substrates underlying opioid tolerance.

Analgesic Effects of Fisetin, Peimine, Astaxanthin, Artemisinin, Bardoxolone Methyl and 740 Y-P and Their Influence on Opioid Analgesia in a Mouse Model of Neuropathic Pain

Treatment of neuropathic pain remains a challenge for modern medicine due to the insufficiently understood molecular mechanisms of its development and maintenance. One of the most important cascades that modulate the nociceptive response is the family of mitogen-activated protein (MAP) kinases and phosphatidylinositol-3-kinase (PI3K), as well as nuclear factor erythroid 2-related factor 2 (Nrf2). The aim of this study was to determine the effect of nonselective modulators of MAP kinases-fisetin (ERK1/2 and NFκB inhibitor, PI3K activator), peimine (MAPK inhibitor), astaxanthin (MAPK inhibitor, Nrf2 activator) and artemisinin (MAPK inhibitor, NFκB activator), as well as bardoxolone methyl (selective activator of Nrf2) and 740 Y-P (selective activator of PI3K)-in mice with peripheral neuropathy and to compare their antinociceptive potency and examine their effect on analgesia induced by opioids. The study was performed using albino Swiss male mice that were exposed to chronic constriction injury of the sciatic nerve (CCI model). Tactile and thermal hypersensitivity was measured using von Frey and cold plate tests, respectively. Single doses of substances were administered intrathecally on day 7 after CCI. Among the tested substances, fisetin, peimine, and astaxanthin effectively diminished tactile and thermal hypersensitivity in mice after CCI, while artemisinin did not exhibit analgesic potency in this model of neuropathic pain. Additionally, both of the activators tested, bardoxolone methyl and 740 Y-P, also showed analgesic effects after intrathecal administration in mice exposed to CCI. In the case of astaxanthin and bardoxolone methyl, an increase in analgesia after combined administration with morphine, buprenorphine, and/or oxycodone was observed. Fisetin and peimine induced a similar effect on tactile hypersensitivity, where analgesia was enhanced after administration of morphine or oxycodone. In the case of 740 Y-P, the effects of combined administration with each opioid were observed only in the case of thermal hypersensitivity. The results of our research clearly indicate that substances that inhibit all three MAPKs provide pain relief and improve opioid effectiveness, especially if they additionally block NF-κB, such as peimine, inhibit NF-κB and activate PI3K, such as fisetin, or activate Nrf2, such as astaxanthin. In light of our research, Nrf2 activation appears to be particularly beneficial. The abovementioned substances bring promising results, and further research on them will broaden our knowledge regarding the mechanisms of neuropathy and perhaps contribute to the development of more effective therapy in the future.

Efficacy of reconstituted intravenous fentanyl to sublingual solution versus oral morphine syrup for breakthrough pain among patients with chronic gynecologic cancer pain: A randomized, double-blind, placebo-controlled trial

Rapid-acting fentanyl formulations are superior to oral morphine (OM) syrup in controlling breakthrough pain among patients with cancer, but they are expensive and unavailable in many countries.

OBJECTIVE

To evaluate the efficacy of reconstituted intravenous fentanyl to sublingual solution (IFS) in relieving breakthrough pain as compared with OM.

METHODS

In this randomized, double-blind, double-dummy, placebo-controlled trial, patients with gynecologic cancer aged ≥18 years experiencing chronic cancer pain with breakthrough pain were enrolled. Patients were randomly allocated (1:1) to receive either 50 μg IFS or 5 mg OM. Pain intensity level was assessed at 5, 15, 30, 45, 60, and 120 min after treatment. The primary outcome was the reduction in pain intensity at 15 min in the intention-to-treat population (ClinicalTrials.gov, NCT05037539).

RESULTS

Between June 15, 2021 and December 30, 2021, 40 participants were equally and randomly assigned to receive IFS or OM. The primary outcome was significantly higher in the IFS group (4.25 vs. 1.05, p < 0.0001). The secondary outcomes also showed higher reduction in pain intensity at 5 min in the IFS group. Subsequent breakthrough pain did not differ between the two groups. However, the reduction in pain was lower in the IFS group at 45, 60, and 120 min, where pain was classified as mild. No severe adverse effects were observed in both groups. Burning sensation without noticeable lesion was found in 20% of the IFS group.

CONCLUSION

IFS can reduce early breakthrough pain. IFS may be considered for breakthrough pain when rapid-acting fentanyl formulations are unavailable.

Extracellular vesicle-mediated delivery of anti-miR-106b inhibits morphine-induced primary ciliogenesis in the brain

Repeated use of opioids such as morphine causes changes in the shape and signal transduction pathways of various brain cells, including astrocytes and neurons, resulting in alterations in brain functioning and ultimately leading to opioid use disorder. We previously demonstrated that extracellular vesicle (EV)-induced primary ciliogenesis contributes to the development of morphine tolerance. Herein, we aimed to investigate the underlying mechanisms and potential EV-mediated therapeutic approach to inhibit morphine-mediated primary ciliogenesis. We demonstrated that miRNA cargo in morphine-stimulated-astrocyte-derived EVs (morphine-ADEVs) mediated morphine-induced primary ciliogenesis in astrocytes. CEP97 is a target of miR-106b and is a negative regulator of primary ciliogenesis. Intranasal delivery of ADEVs loaded with anti-miR-106b decreased the expression of miR-106b in astrocytes, inhibited primary ciliogenesis, and prevented the development of tolerance in morphine-administered mice. Furthermore, we confirmed primary ciliogenesis in the astrocytes of opioid abusers. miR-106b-5p in morphine-ADEVs induces primary ciliogenesis via targeting CEP97. Intranasal delivery of ADEVs loaded with anti-miR-106b ameliorates morphine-mediated primary ciliogenesis and prevents morphine tolerance. Our findings bring new insights into the mechanisms underlying primary cilium-mediated morphine tolerance and pave the way for developing ADEV-mediated small RNA delivery strategies for preventing substance use disorders.

Brain glucose metabolism and dopamine transporter changes in rats with morphine-induced conditioned place preference

Addiction to morphine is a chronic brain disease leading to compulsive abuse. Drug addiction animal models with and without conditioned place preference (CPP) training have been used to investigate cue-elicited drug craving. We used ¹⁸ F-fluorodeoxyglucose (¹⁸ F-FDG) and ¹¹ C-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane (¹¹ C-CFT) micro-PET/CT scans to examine the regional changes in brain glucose metabolism and dopamine transporter (DAT) availability to study their relationship underlying drug memory in morphine-treated rat models with and without CPP. Standardized uptake value ratio (SUVr) of ¹⁸ F-FDG significantly decreased in the medial prefrontal cortex (mPFC) and cingulate with short-term morphine administration compared with the baseline condition. Voxelwise analysis indicated glucose metabolism alterations in the somatosensory cortex, hippocampus and cingulate in morphine-treated rats and in the striatum, thalamus, medial prefrontal cortex, primary motor cortex and many regions in the cortex in the CPP group compared with the baseline condition. Alterative glucose metabolism was also observed in the striatum, primary somatosensory cortex and some cortical regions in the CPP group compared with morphine alone group. DAT expression alterations were only observed in the long-term morphine compared with the short-term morphine group. This study shows that cerebral glucose metabolism significantly altered during morphine administration and CPP process mainly in the mPFC, striatum and hippocampus, which indicates that the function of these brain regions is involved in cue-induced craving and memory retrieval.

Cigarette Smoke Modulates Inflammation and Immunity via Reactive Oxygen Species-Regulated Trained Immunity and Trained Tolerance Mechanisms

Significance: Cigarette smoke (CS) is a prominent cause of morbidity and death and poses a serious challenge to the current health care system worldwide. Its multifaceted roles have led to cardiovascular, respiratory, immunological, and neoplastic diseases. Recent Advances: CS influences both innate and adaptive immunity and regulates immune responses by exacerbating pathogenic immunological responses and/or suppressing defense immunity. There is substantial evidence pointing toward a critical role of CS in vascular immunopathology, but a comprehensive and up-to-date review is lacking. Critical Issues: This review aims to synthesize novel conceptual advances on the immunomodulatory action of CS with a focus on the cardiovascular system from the following perspectives: (i) the signaling of danger-associated molecular pattern (DAMP) receptors contributes to CS modulation of inflammation and immunity; (ii) CS reprograms immunometabolism and trained immunity-related metabolic pathways in innate immune cells and T cells, which can be sensed by the cytoplasmic (cytosolic and non-nuclear organelles) reactive oxygen species (ROS) system in vascular cells; (iii) how nuclear ROS drive CS-promoted DNA damage and cell death pathways, thereby amplifying inflammation and immune responses; and (iv) CS induces endothelial cell (EC) dysfunction and vascular inflammation to promote cardiovascular diseases (CVDs). Future Directions: Despite significant progress in understanding the cellular and molecular mechanisms linking CS to immunity, further investigations are warranted to elucidate novel mechanisms responsible for CS-mediated immunopathology of CVDs; in particular, the research in redox regulation of immune functions of ECs and their fate affected by CS is still in its infancy.

Pharmacogenetics of pain management in Zimbabwean patients with sickle cell disease

Background: Pain is a common cause of hospitalization in sickle cell disease (SCD) patients. Failure to effectively control pain remains a challenge in patient care. Materials & methods: The authors conducted a cross-sectional study to determine the effect of CYP2D6 and UGT2B7 polymorphisms on pain management in 106 Zimbabwean SCD patients. Participant information was collected on a questionnaire. Genotyping was conducted using the GenoPharm® pharmacogenomics open array panel containing CYP2D6 and UGT genetic variants implicated in opioid response. Results: The reduced function alleles CYP2D6*17 and *29 had high frequencies of 15.9% and 12.9%, respectively. UGT2B7 rs73823859 showed a statistically significant correlation with pain levels (p = 0.0454). Conclusion: This study demonstrated the role of UGT2B7 polymorphism in SCD patient pain management.

Adolescence as a critical period for nandrolone-induced muscular strength in relation to abuse liability, alone and in conjunction with morphine, using accumbal dopamine efflux in freely moving rats

Nandrolone, an anabolic androgenic steroid, is included in the prohibited list of the World Anti-Doping Agency. Drugs of abuse activate brain dopamine neurons and nandrolone has been suspected of inducing dependence. Accordingly, possible critical periods for the effects of nandrolone on muscular strength and dopaminergic activity have been investigated, including the effects of chronically administered nandrolone alone and on morphine-induced increases in dopamine efflux in the nucleus accumbens. Six- or 10-week-old male Sprague-Dawley rats were used. Treatment with nandrolone was initiated in adolescent (6-week-old) and young adult (10-week-old) rats. Nandrolone (5.0 mg/kg s.c.) or sesame oil vehicle was given once daily, on six consecutive days per week, for 3 weeks and then once per day for 4 consecutive days. Nandrolone enhanced the developmental increase in grip strength of 6- but not 10-week-old rats, without altering the developmental increase in body weight of either age group. Using in vivo microdialysis in freely moving 6-week-old rats given nandrolone for 4 weeks, basal accumbal dopamine efflux was unaltered, while the increase in dopamine efflux induced by acute administration of morphine (1.0 mg/kg s.c.) was reduced. The present study provides in vivo evidence that adolescence constitutes a critical period during which repeated administration of nandrolone enhances increases in muscular strength without influencing increases in body weight. Though repeated administration of nandrolone during this period of adolescence did not stimulate in vivo mesolimbic dopaminergic activity, it disrupted stimulation by an opioid, the drug class that is most commonly coabused with nandrolone.

The role of NMDA glutamate receptors in the lateral habenula on morphine-induced conditioned place preference in rats

The lateral habenula (LHb) has received special attention due to its role in modulating motivated behavior, stress response, and rewarding and aversive stimuli through monoamine transmission. In the present study, the involvement of the N-methyl-d-aspartate (NMDA) receptors of the LHb in the expression and acquisition phases of morphine-induced conditioned place preference (CPP) was studied in male rats. Bilateral injections of agonist/antagonist (MK-801) of NMDA receptor were performed during the conditioning sessions of the acquisition phase. In other separate groups, drugs were also injected into the LHb before the test session during the expression phase of CPP. A 5-day CPP bias paradigm was used to study the effect of injections of NMDA and MK-801 into the LHb on morphine reward-related behavior. Different doses of NMDA plus morphine reduced the CPP score during the acquisition phase, whereas MK-801 significantly increased conditioning scores during the acquisition phase of CPP. The injection of agonists and antagonists of NMDA receptors in LHb had no significant effect on CPP scores and locomotion during the expression phase of CPP, whereas the motor activity in the acquisition phase was affected by the drugs. The reduction effect of NMDA on the CPP scores during the acquisition phase was blocked by pretreatment with MK-801. Our findings also suggest that NMDA receptors in the LHb may be involved in the acquisition phase of morphine-induced CPP.

Scheduled Opioid Administration in Hospice Patients Before and After Targeted Caregiver Education

Background

Hospice and palliative care have been shown to increase patient satisfaction and improve symptom control at the end of life. Opioid analgesics are typically given around the clock at the end of life to maintain symptom control and prevent the need for larger doses later. Many hospice patients have some degree of cognitive impairment, putting them at risk of being undertreated for pain.

Methods

This was a retrospective, quasi-experimental study at a 766-bed community hospital with hospice and palliative care services. Adult patients admitted to inpatient hospice care with active orders for scheduled opioids for at least 12 hours with at least 1 dose administered were included. The primary intervention was the creation and dissemination of education to non-intensive care nursing staff. The primary outcome was the administration rate of scheduled opioid analgesics to hospice patients before and after targeted caregiver education. Secondary outcomes included the rate of use of 1-time or as-needed opioids, the rate of use-of-reversal agents, and the impact of COVID-19 infection status on administration rates of scheduled opioids.

Results

A total of 75 patients were included in the final analysis. The rate of missed doses was 5% in the pre-implementation cohort and 4% in the post-implementation cohort (P = .21). The rate of delayed doses was 6% in the pre-implementation cohort and 6% in the post-implementation cohort (P = .97). Secondary outcomes were similar between the two groups with the exception of a higher rate of delayed doses in patients with confirmed COVID-19 as compared to those without COVID-19 (P = .047).

Conclusion

The creation and dissemination of nursing education were not associated with a decrease in missed or delayed doses of scheduled opioids in hospice patients.

Telmisartan Is a Promising Agent for Managing Neuropathic Pain and Delaying Opioid Analgesic Tolerance in Rats

Despite the large arsenal of analgesic medications, neuropathic pain (NP) management is not solved yet. Angiotensin II receptor type 1 (AT1) has been identified as a potential target in NP therapy. Here, we investigate the antiallodynic effect of AT1 blockers telmisartan and losartan, and particularly their combination with morphine on rat mononeuropathic pain following acute or chronic oral administration. The impact of telmisartan on morphine analgesic tolerance was also assessed using the rat tail-flick assay. Morphine potency and efficacy in spinal cord samples of treated neuropathic animals were assessed by [35S]GTPγS-binding assay. Finally, the glutamate content of the cerebrospinal fluid (CSF) was measured by capillary electrophoresis. Oral telmisartan or losartan in higher doses showed an acute antiallodynic effect. In the chronic treatment study, the combination of subanalgesic doses of telmisartan and morphine ameliorated allodynia and resulted in a leftward shift in the dose-response curve of morphine in the [35S]GTPγS binding assay and increased CSF glutamate content. Telmisartan delayed morphine analgesic-tolerance development. Our study has identified a promising combination therapy composed of telmisartan and morphine for NP and opioid tolerance. Since telmisartan is an inhibitor of AT1 and activator of PPAR-γ, future studies are needed to analyze the effect of each component.

Repeated Administration of the Cannabinoid WIN Alters the Isoflurane-Sparing Effect of Morphine and Dexmedetomidine

The impacts of morphine and dexmedetomidine on the MAC of isoflurane were studied in rats constantly medicated with the cannabinoid WIN 55,212-2.

METHODS

Prior to the administration of morphine, the MAC was measured in both untreated rats (MAC _(ISO)) and those treated with a cannabinoid (MAC _{(ISO + CANN)}). The effects of morphine (MAC _{(ISO + MOR)}) and dexmedetomidine (MAC _{(ISO + DEX)}) on untreated rats and rats treated for 21 days with the cannabinoids (MAC _{(ISO + CANN + MOR)}) and (MAC _{(ISO + CANN + DEX}) were also studied.

RESULTS

MAC _(ISO) was 1.32 ± 0.06, and MAC _{(ISO + CANN)} was 1.69 ± 0.09. MAC _{(ISO + MOR)} was 0.97 ± 0.02 (26% less than MAC _(ISO)). MAC _{(ISO + CANN + MOR)} was 1.55 ± 0.08 (8% less than MAC _{(ISO + CANN)}), MAC _{(ISO + DEX)} was 0.68 ± 0.10 (48% less than MAC _(ISO)), and MAC _{(ISO + CANN + DEX)} was 0.67 ± 0.08 (60% less than MAC _{(ISO + CANN)}).

CONCLUSIONS

Medication with a cannabinoid for 21 days augmented the MAC of isoflurane. The sparing effect of morphine on isoflurane is lower in rats constantly medicated with a cannabinoid. The sparing effect of dexmedetomidine on the minimum alveolar concentration of isoflurane is greater in rats repeatedly medicated with a cannabinoid.

Prenatal Morphine Exposure Increases Cardiovascular Disease Risk and Programs Neurogenic Hypertension in the Adult Offspring

BACKGROUND

The opioid overdose and opioid use disorder epidemics are concomitant with increased metabolic and CVD risk. Although opioid use disorder causes adverse pregnancy outcomes, the offspring's cardiovascular health is understudied. We hypothesized that offspring exposed to morphine in utero would show increased CVD risk factors and endogenous opioid system dysregulation.

METHODS

Sprague Dawley dams were treated with saline (vehicle, n=10) or escalating doses of morphine (5-20 mg/kg per day, SC, n=10) during gestation. Cardiovascular and metabolic parameters were assessed in adult offspring.

RESULTS

Litter size and pups' birth weight were not different in response to morphine exposure. Female and male morphine-exposed offspring showed reduced body length at birth (P<0.05) and body weight from weeks 1 to 3 of life (P<0.05), followed by a catch-up growth effect. By week 16, female and male morphine-exposed rats showed reduced tibia length (P<0.05) and fat mass. In utero morphine exposure increases the mean arterial pressure and the depressor response to mecamylamine (5 mg/kg per day, IP) increases were abolished by a chronic treatment with an alpha-adrenergic receptor blocker (prazosin; 1 mg/kg per day, IP). Although circulating levels of angiotensin peptides were similar between groups, in utero morphine exposure exacerbated maximal ex vivo Ang (angiotensin) II-induced vasoconstriction (P<0.05) and induced endothelial dysfunction in a sex-specific manner (P<0.05). Proenkephalin, an endogenous opioid peptide that lowers blood pressure and sympathetic-mediated vasoconstriction, showed reduced mRNA expression in the heart, aorta, and kidneys from morphine versus vehicle group (P<0.05).

CONCLUSIONS

Among the effects of in utero morphine exposure, neurogenic hypertension, vascular dysfunction, and metabolic dysfunction could be associated with the dysregulation of the endogenous opioid system.

Opioid Receptors Modulate Firing and Synaptic Transmission in the Paraventricular Nucleus of the Thalamus

The paraventricular nucleus of the thalamus (PVT) is involved in drug addiction-related behaviors, and morphine is a widely used opioid for the relief of severe pain. Morphine acts via opioid receptors, but the function of opioid receptors in the PVT has not been fully elucidated. Here, we used in vitro electrophysiology to study neuronal activity and synaptic transmission in the PVT of male and female mice. Activation of opioid receptors suppresses the firing and inhibitory synaptic transmission of PVT neurons in brain slices. On the other hand, the involvement of opioid modulation is reduced after chronic morphine exposure, probably because of desensitization and internalization of opioid receptors in the PVT. Overall, the opioid system is essential for the modulation of PVT activities.SIGNIFICANCE STATEMENT Opioid receptors modulate the activities and synaptic transmission in the PVT by suppressing the firing rate and inhibitory synaptic inputs. These modulations were largely diminished after chronic morphine exposure.

Adolescent morphine exposure impairs cognitive flexibility in female but not male mice

Use of prescription opioids continues to rise, especially in adolescent individuals. As adolescence is a critical development window for higher order cognitive functions, thus opioid exposure during this period may have significant long-lasting effects on cognitive function and predisposition individuals to be at greater risk of developing opioid use later in life. Here, we examine previously explored effects of opioid exposure during adolescence on affect-related behavior, motivation, and cognitive flexibility. We find that a two-week exposure to non-contingent morphine during adolescence (i.e., post-weaning) does not alter performance in an elevated plus maze, forced swim test, or motivation for appetitive reward in male or female mice when tested during adolescence or adulthood. Examination of how adolescent morphine impacts cognition revealed impairments in visual-based discriminative learning and cognitive flexibility in female but not male mice, as assessed using an operant-based attentional set-shifting task. Unexpectedly, deficits in discriminative learning are observed when testing occurred during adolescence but not adulthood, whereas impaired performance in the extradimensional shift remained impaired into adulthood. The data indicate that opioid exposure during adolescence has a greater impact on cognitive function in female mice and that these deficits may be more widespread during acute withdrawal periods, while deficits in flexibility more enduring.

Central metabolism as a potential origin of sex differences in morphine antinociception but not induction of antinociceptive tolerance in mice

BACKGROUND AND PURPOSE

In rodents, morphine antinociception is influenced by sex. However, conflicting results have been reported regarding the interaction between sex and morphine antinociceptive tolerance. Morphine is metabolised in the liver and brain into morphine-3-glucuronide (M3G). Sex differences in morphine metabolism and differential metabolic adaptations during tolerance development might contribute to behavioural discrepancies. This article investigates the differences in peripheral and central morphine metabolism after acute and chronic morphine treatment in male and female mice.

EXPERIMENTAL APPROACH

Sex differences in morphine antinociception and tolerance were assessed using the tail-immersion test. After acute and chronic morphine treatment, morphine and M3G metabolic kinetics in the blood were evaluated using LC-MS/MS. They were also quantified in several CNS regions. Finally, the blood-brain barrier (BBB) permeability of M3G was assessed in male and female mice.

KEY RESULTS

This study demonstrated that female mice showed weaker morphine antinociception and faster induction of tolerance than males. Additionally, female mice showed higher levels of M3G in the blood and in several pain-related CNS regions than male mice, whereas lower levels of morphine were observed in these regions. M3G brain/blood ratios after injection of M3G indicated no sex differences in M3G BBB permeability, and these ratios were lower than those obtained after injection of morphine.

CONCLUSION

These differences are attributable mainly to morphine central metabolism, which differed between males and females in pain-related CNS regions, consistent with weaker morphine antinociceptive effects in females. However, the role of morphine metabolism in antinociceptive tolerance seemed limited.

LINKED ARTICLES

This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Distinct and sex-specific expression of mu opioid receptors in anterior cingulate and somatosensory S1 cortical areas

ABSTRACT

The anterior cingulate cortex (ACC) processes the affective component of pain, whereas the primary somatosensory cortex (S1) is involved in its sensory-discriminative component. Injection of morphine in the ACC has been reported to be analgesic, and endogenous opioids in this area are required for pain relief. Mu opioid receptors (MORs) are expressed in both ACC and S1; however, the identity of MOR-expressing cortical neurons remains unknown. Using the Oprm1-mCherry mouse line, we performed selective patch clamp recordings of MOR+ neurons, as well as immunohistochemistry with validated neuronal markers, to determine the identity and laminar distribution of MOR+ neurons in ACC and S1. We found that the electrophysiological signatures of MOR+ neurons differ significantly between these 2 areas, with interneuron-like firing patterns more frequent in ACC. While MOR+ somatostatin interneurons are more prominent in ACC, MOR+ excitatory neurons and MOR+ parvalbumin interneurons are more prominent in S1. Our results suggest a differential contribution of MOR-mediated modulation to ACC and S1 outputs. We also found that females had a greater density of MOR+ neurons compared with males in both areas. In summary, we conclude that MOR-dependent opioidergic signaling in the cortex displays sexual dimorphisms and likely evolved to meet the distinct function of pain-processing circuits in limbic and sensory cortical areas.

The efficacy of paravertebral block evaluated by pain-related biomarkers and reactive oxygen species (ROS) following surgery for breast cancer: A randomized controlled study

Background and Aims

Paravertebral block has been found to be a recommended method of analgesia for breast surgeries. We aimed to assess the efficacy of paravertebral block compared to morphine by means of the visual analogue scale (VAS), pain-related biomarkers, and reactive oxygen species (ROS) in adult patients undergoing breast cancer surgeries under general anesthesia.

Methodology

Forty patients undergoing breast surgery with or without lymph outcome were randomly divided into two groups. Group M received general anesthesia with intraoperative injection morphine (0.1 mg/kg) and group P received general anesthesia with paravertebral block with 0.25% bupivacaine (0.3 ml/kg). The primary objective was to compare the postoperative pain using VAS at baseline, 2 hours, 24 hours, and 48 hours. Secondary objectives were to compare the levels of pain-related biomarkers and ROS in both the groups at baseline, 24 hours, and 48 hours and to study the correlation between the VAS and level of pain-related biomarkers and ROS.

Results

There was no significant difference in the postoperative VAS scores in both the groups (P = 0.252, 0.548, 0.488 at baseline, 24 hours, and 48 hours, respectively) and no significant difference in the mean biomarkers in both the groups. The mean VAS negatively correlated with biomarker levels at 24 hours and 48 hours, but the change in VAS after 24 hours and 48 hours did not significantly correlate with the change in the biomarkers.

Conclusion

Paravertebral block is equally efficacious to intraoperative morphine for breast surgeries for postoperative analgesia. The biomarker levels were not significantly different when patients received paravertebral block or morphine.

Remote local photoactivation of morphine produces analgesia without opioid-related adverse effects

BACKGROUND AND PURPOSE

Opioid-based drugs are the gold standard medicines for pain relief. However, tolerance and several side effects (i.e. constipation and dependence) may occur upon chronic opioid administration. Photopharmacology is a promising approach to improve the benefit/risk profiles of these drugs. Thus, opioids can be locally activated with high spatiotemporal resolution, potentially minimizing systemic-mediated adverse effects. Here, we aimed at developing a morphine photo-derivative (photocaged morphine), which can be activated upon light irradiation both in vitro and in vivo.

EXPERIMENTAL APPROACH

Light-dependent activity of pc-morphine was assessed in cell-based assays (intracellular calcium accumulation and electrophysiology) and in mice (formalin animal model of pain). In addition, tolerance, constipation and dependence were investigated in vivo using experimental paradigms.

KEY RESULTS

In mice, pc-morphine was able to elicit antinociceptive effects, both using external light-irradiation (hind paw) and spinal cord implanted fibre-optics. In addition, remote morphine photoactivation was devoid of common systemic opioid-related undesired effects, namely, constipation, tolerance to the analgesic effects, rewarding effects and naloxone-induced withdrawal.

CONCLUSION AND IMPLICATIONS

Light-dependent opioid-based drugs may allow effective analgesia without the occurrence of tolerance or the associated and severe opioid-related undesired effects.

LINKED ARTICLES

This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

A morphine reward generalization mouse model based on conditioned place preference and aversion

BACKGROUND

Conditioned place preference (CPP) is a common behavioral paradigm for studying the association of unconditioned stimulus reward memory with context. Generalization is a flexible memory recall pattern developed on the basis of original memory. Drug-seeking behaviors in substance use disorders (SUDs) exhibit diversity, which we generally attribute to the highly generalized features of SUD memory. However, to date, there are no animal models for SUD generalization studies.

METHODS

We design the generalization box (G-box) and the generalization retrieval process based on the conditioned place preference (CPP) model. In the memory retrieval stage, we replaced the conditioning CPP box (T-box) with a generalization box (G-box) to study drug generalization memory. For appearance, the generalized boxes have different angles and numbers of sides compared to the conditioning boxes. For the visual cues, the shapes of the symbols are different (triangle icons for the hexagonal chamber and dot icons for the round chamber), but the orientation information remains the same. To establish CPP generalization, the mice received morphine on the vertical or horizontal side of a conditioning box (T-box) and saline on the other side. Then, after CPP conditioning, the generalization test was performed in a generalization box (G-box: hexagonal chamber and Gr-box: round chamber) 21 days later.

RESULTS

CPP-conditioned mice still displayed a clear preference for similar visual information in the G-box. CPA-conditioned mice behaved similarly to CPP, with mice consistently avoiding similar visual information in the G-box. We further observed that the generalization results are similar using two generalization boxes (G-box and Gr-box).

CONCLUSION

In this study, we succeeded in creating a simple and effective generalization model for morphine reward. The establishment of this model provides a new tool for generalization studies of SUD and therapy in humans.

High-dose opioids for chronic non-cancer pain: an overview of Cochrane Reviews

BACKGROUND

This overview was originally published in 2017, and is being updated in 2022.  Chronic pain is typically described as pain on most days for at least three months. Chronic non-cancer pain (CNCP) is any chronic pain that is not due to a malignancy. Chronic non-cancer pain in adults is a common and complex clinical issue, for which opioids are prescribed by some physicians for pain management. There are concerns that the use of high doses of opioids for CNCP lacks evidence of effectiveness, and may increase the risk of adverse events.

OBJECTIVES

To describe the evidence from Cochrane Reviews and overviews regarding the efficacy and safety of high-dose opioids (defined as 200 mg morphine equivalent or more per day) for CNCP.

METHODS

We identified Cochrane Reviews and overviews by searching the Cochrane Database of Systematic Reviews in The Cochrane Library. The date of the last search was 21 July 2022. Two overview authors independently assessed the search results. We planned to analyse data on any opioid agent used at a high dose for two weeks or more for the treatment of CNCP in adults.

MAIN RESULTS

We did not identify any reviews or overviews that met the inclusion criteria. The excluded reviews largely reflected low doses or titrated doses, where all doses were analysed as a single group; we were unable to extract any data for high-dose use only.

AUTHORS' CONCLUSIONS

There is a critical lack of high-quality evidence, in the form of Cochrane Reviews, about how well high-dose opioids work for the management of CNCP in adults, and regarding the presence and severity of adverse events.  No evidence-based argument can be made on the use of high-dose opioids, i.e. 200 mg morphine equivalent or more daily, in clinical practice. Considering that high-dose opioids have been, and are still being used in clinical practice to treat CNCP, knowing about the efficacy and safety of these higher doses is imperative.

Morphine Versus Oxycodone for Cancer Pain Using a Catechol-O-methyltransferase Genotype Biomarker: A Multicenter, Randomized, Open-Label, Phase III Clinical Trial (RELIEF Study)

BACKGROUND

We hypothesized that the high-dose opioid requirement in patients carrying the rs4680-GG variant in the COMT gene encoding catechol-O-methyltransferase would be greater for patients taking morphine than for those taking oxycodone, thus providing a much-needed biomarker to inform opioid selection for cancer pain.

METHODS

A randomized, multicenter, open-label trial was conducted at a Japanese hospital's palliative care service. Patients with cancer pain treated with regular doses of nonsteroidal anti-inflammatory drugs or acetaminophen were enrolled and randomized (1:1) into morphine (group M) and oxycodone (group O) groups. The minimum standard dose of immediate-release (IR) oral opioids was repeatedly administered by palliative care physicians to achieve pain-reduction goals (Pain reduction ≥ 33% from baseline and up to ≤ 3 on a numerical rating scale). The primary endpoint was the proportion of subjects requiring high-dose opioids on day 0 with the GG genotype.

RESULTS

Of 140 participants who developed cancer-related pain among 378 subjects registered and pre-screened for the genotype, 139 were evaluated in the current study. Among patients carrying a COMT rs4680-GG genotype, 48.3% required high-dose opioids in group M, compared with the 20.0% in group O (95% CI, 3.7%-50.8%; P = .029). Of those with the non-GG genotype, 41.5% treated with morphine and 23.1% with oxycodone required high-dose opioids (95% CI, 3.3%-38.3%; P = 0.098).

CONCLUSION

Using the COMT rs4680 genotype alone is not recommended for selecting between morphine and oxycodone for pain relief.

Concentrations, pharmacokinetics and selected pharmacodynamics of morphine and its active metabolites following oral administration to horses

The metabolism and pharmacokinetics of intravenous (i.v.) morphine in the horse have been described; however, administration of therapeutic doses has also been associated with neuroexcitation and adverse gastrointestinal effects. In this study, we hypothesized that oral administration would lead to comparable concentrations of morphine and its presumed active metabolite, morphine 6-glucuronide (M6G) without the adverse effects associated with i.v. administration. Eight horses were administered a single i.v. dose of 0.2 mg/kg morphine and oral doses of 0.2, 0.6, and 0.8 mg/kg of morphine in a four-way balanced crossover design, with a 2-week washout period between doses. Concentrations of morphine and metabolites were determined, and pharmacokinetic parameters determined. Physiologic and behavioral outcomes including the number of steps taken, changes in heart rate, and gastrointestinal borborygmi were assessed. Oral administration of morphine resulted in higher concentrations of morphine metabolites, including M6G (C_max : 11.6-37.8 ng/mL (0.6 mg/kg); 15.8-42.6 ng/mL (0.8 mg/kg)), compared with i.v. Bioavailability was 36.5%, 27.6% and 28.0% for 0.2, 0.6 and 0.8 mg/kg, respectively. Behavioral and physiologic changes were noted in all groups but were less prominent with oral compared with i.v. administration. Results of the current study are encouraging for further study, specifically anti-nociceptive effects of morphine following oral administration.

Novel GluN2B-Selective NMDA Receptor Negative Allosteric Modulator Possesses Intrinsic Analgesic Properties and Enhances Analgesia of Morphine in a Rodent Tail Flick Pain Model

Many cases of accidental death associated with drug overdose are due to chronic opioid use, tolerance, and addiction. Analgesic tolerance is characterized by a decreased response to the analgesic effects of opioids, requiring increasingly higher doses to maintain the desired level of pain relief. Overactivation of GluN2B-containing N-methyl-d-Aspartate receptors is thought to play a key role in mechanisms underlying cellular adaptation that takes place in the development of analgesic tolerance. Herein, we describe a novel GluN2B-selective negative allosteric modulator, EU93-108, that shows high potency and brain penetrance. We describe the structural basis for binding at atomic resolution. This compound possesses intrinsic analgesic properties in the rodent tail immersion test. EU93-108 has an acute and significant anodyne effect, whereby morphine when combined with EU93-108 produces a higher tail flick latency compared to that of morphine alone. These data suggest that engagement of GluN2B as a target has utility in the treatment of pain, and EU93-108 could serve as an appropriate tool compound to interrogate this hypothesis. Future structure-activity relationship work around this scaffold could give rise to compounds that can be co-administered with opioids to diminish the onset of tolerance due to chronic opioid use, thereby modifying their utility.

The roles of ubiquitin-proteasome system and regulator of G protein signaling 4 in behavioral sensitization induced by a single morphine exposure

AIMS

Opioid addiction is a major public health issue, yet its underlying mechanism is still unknown. The aim of this study was to explore the roles of ubiquitin-proteasome system (UPS) and regulator of G protein signaling 4 (RGS4) in morphine-induced behavioral sensitization, a well-recognized animal model of opioid addiction.

METHODS

We explored the characteristics of RGS4 protein expression and polyubiquitination in the development of behavioral sensitization induced by a single morphine exposure in rats, and the effect of a selective proteasome inhibitor, lactacystin (LAC), on behavioral sensitization.

RESULTS

Polyubiquitination expression was increased in time-dependent and dose-related fashions during the development of behavioral sensitization, while RGS4 protein expression was not significantly changed during this phase. Stereotaxic administration of LAC into nucleus accumbens (NAc) core inhibited the establishment of behavioral sensitization.

CONCLUSION

UPS in NAc core is positively involved in behavioral sensitization induced by a single morphine exposure in rats. Polyubiquitination was observed during the development phase of behavioral sensitization, while RGS4 protein expression was not significantly changed, indicating that other members of RGS family might be substrate proteins in UPS-mediated behavioral sensitization.

Comparisons of stress-related neuronal activation induced by restraint in adult male rat offspring with prenatal exposure to buprenorphine, methadone, or morphine

Prenatal opioid exposure may impede the development of adaptive responses to environmental stimuli by altering the stress-sensitive brain circuitry located at the paraventricular nucleus of the hypothalamus (PVH) and locus coeruleus (LC). Corticotropin-releasing factor (CRF) released from neurons in the PVH has emerged as a key molecule to initiate and integrate the stress response. Methadone (Meth) and buprenorphine (Bu) are two major types of synthetic opioid agonists for first-line medication-assisted treatment of opioid (e.g., morphine, Mor) use disorder in pregnant women. No studies have compared the detrimental effects of prenatal exposure to Meth versus Bu on the stress response of their offspring upon reaching adulthood. In this study, we aimed to compare stress-related neuronal activation in the PVH and LC induced by restraint (RST) stress in adult male rat offspring with prenatal exposure to the vehicle (Veh), Bu, Meth, or Mor. CFos-immunoreactive cells were used as an indicator for neuronal activation. We found that RST induced less neuronal activation in the Meth or Mor exposure groups compared with that in the Bu or Veh groups; no significant difference was detected between the Bu and Veh exposure groups. RST-induced neuronal activation was completely prevented by central administration of a CRF receptor antagonist (α-helical CRF_9-41, 10 μg/3 μL) in all exposure groups, suggesting the crucial role of CRF in this stress response. In offspring without RST, central administration of CRF (0.5 μg/3 μL)-induced neuronal activation in the PVH and LC. CRF-induced neuronal activation was lessened in the Meth or Mor exposure groups compared with that in the Bu or Veh groups; no significant difference was detected between the Bu and Veh exposure groups. Moreover, RST- or CRF-induced neuronal activation in the Meth exposure group was comparable with that in the Mor exposure group. Further immunohistochemical analysis revealed that the Meth and Mor exposure groups displayed less CRF neurons in the PVH of offspring with or without RST compared with the Bu or Veh groups. Thus, stress-induced neuronal activation in the PVH and LC was well preserved in adult male rat offspring with prenatal exposure to Bu, but it was substantially lessened in those with prenatal exposure to Meth or Mor. Lowered neuronal activation found in the Meth or Mor exposure groups may be, at least in part, due to the reduction in the density of CRF neurons in the PVH.

Striatal μ-opioid receptor activation triggers direct-pathway GABAergic plasticity and induces negative affect

Withdrawal from chronic opioid use often causes hypodopaminergic states and negative affect, which may drive relapse. Direct-pathway medium spiny neurons (dMSNs) in the striatal patch compartment contain μ-opioid receptors (MORs). It remains unclear how chronic opioid exposure and withdrawal impact these MOR-expressing dMSNs and their outputs. Here, we report that MOR activation acutely suppressed GABAergic striatopallidal transmission in habenula-projecting globus pallidus neurons. Notably, withdrawal from repeated morphine or fentanyl administration potentiated this GABAergic transmission. Furthermore, intravenous fentanyl self-administration enhanced GABAergic striatonigral transmission and reduced midbrain dopaminergic activity. Fentanyl-activated striatal neurons mediated contextual memory retrieval required for conditioned place preference tests. Importantly, chemogenetic inhibition of striatal MOR+ neurons rescued fentanyl withdrawal-induced physical symptoms and anxiety-like behaviors. These data suggest that chronic opioid use triggers GABAergic striatopallidal and striatonigral plasticity to induce a hypodopaminergic state, which may promote negative emotions and relapse.

Morphine prophylaxis alleviates pain in transjugular intrahepatic portosystemic shunt procedure: A randomized clinical trial

BACKGROUND

Transjugular intrahepatic portosystemic shunt (TIPS) is an accepted minimal invasive procedure for the management of complications of portal hypertension.

OBJECTIVE

This study aims to investigate the value of the preemptive administration of morphine, when compared with on-demand morphine, during TIPS.

METHODS

The present study was a randomized control trial. A total of 49 patients were selected to receive 10 mg of morphine either before the TIPS procedure (group B, n= 26), or on demand when needed during the TIPS procedure (group A, n= 23). The patient's pain was scored using the visual analog scale (VAS) during the procedure. VAS, pain performance, HR, systolic pressure, diastolic pressure and SPO2 were recorded at four-time points: before the operation (T0), during the trans-hepatic puncture of the portal vein (T1), during the intrahepatic channel expansion (T2), and when the operation was finished (T3). The duration of the operation was also recorded.

RESULTS

In group A, the proportion of severe pain at T1 was 4.3% (one case), two cases were combined with vagus reflex, and the proportion of severe pain at T2 was 65.2% (15 cases). No severe pain occurred in group B. The VAS score significantly decreased at T1, T2 and T3 in group B, when compared to group A (P< 0.05). HR, systolic pressure and diastolic pressure significantly decreased at T2 and T3 in group B, when compared to group A (P< 0.05). There was no significant difference between the two groups in terms of SPO2 (P> 0.05).

CONCLUSION

Preemptive analgesia can effectively relieve severe pain during TIPS, improve patient comfort and compliance, ensure a routine procedure, and offer excellent safety, and is simple and effective.