The relationship of pharmacokinetics to pharmacological activity: morphine, methadone and naloxone

Acute Opioid Administration Undermines Recovery after SCI: Adverse Effects Are Not Restricted to Morphine

Previous studies have shown that administration of high doses of morphine in the acute phase of spinal cord injury (SCI) significantly undermines locomotor recovery and increases symptoms of chronic pain in a rat spinal contusion model. Similarly, SCI patients treated with high doses of opioid for the first 24 h postinjury have increased symptoms of chronic pain 1 year later. Whether these adverse effects are driven by morphine only or all opioids compromise recovery after SCI, however, is unknown. Based on our previous findings we hypothesized that activation of the kappa opioid receptor (KOR) is key in the morphine-induced attenuation of locomotor recovery after SCI. Thus, we posited that opioids that engage KOR-mediated signaling pathways (morphine, oxycodone) would undermine recovery, and clinically relevant opioids with less KOR activity (fentanyl and buprenorphine) would not. To test this, we compared the effects of the clinically relevant opioids on locomotor recovery and pain in a male rat spinal contusion model. Rats were given a moderate spinal contusion injury followed by 7 days of intravenous morphine, oxycodone, fentanyl, buprenorphine, or saline, and recovery was assessed for 28 days. All opioids produced analgesia on tests of thermal, mechanical, and incremented shock reactivity. However, tolerance developed rapidly with buprenorphine administration, particularly with daily administrations of 5 morphine milligram equivalent (MME) buprenorphine. Opioid-induced hyperalgesia (OIH) also developed across days following administration of higher doses (10 MME, 20 MME) of morphine and oxycodone. Fentanyl and buprenorphine did not produce OIH. Contrary to our hypothesis, however, we found that high doses of all opioids reduced recovery of locomotor function. Unlike the other opioids, the effects of buprenorphine on locomotor recovery appeared transient, but it also produced chronic pain. Morphine, oxycodone, and buprenorphine decreased reactivity thresholds on tests of mechanical and incremented shock stimulation. In sum, all opioids undermined long-term recovery in the rat model. Further interrogation of the molecular mechanisms driving the adverse effects is essential. This study provides critical insight into pain management strategies in the acute phase of SCI and potential long-term consequences of early opioid administration.

Medications for Opioid Use Disorder in People Who Inject Substances: Reflection on the Potential Place of Morphine Sulfate as Substitution Treatment? Results of COSINUS Cohort Study

BACKGROUND

Opioid Use Disorder (OUD) often provokes dramatic consequences in terms of increased morbi-mortality. Two medications have mainly been worldwide used for OUD (MOUD), buprenorphine and methadone. Recently, however, some reports have highlighted the use of Morphine Sulfate (MS) mainly obtained without a prescription but used as MOUD by opioid users and especially People Who Inject Substances (PWIS). We propose to characterize the prevalence and distribution of MOUD and MS use in PWIS.

METHODS

This study examines the use of MOUD and MS amongst French PWIS recruited in harm reduction facilities and drug consumption rooms in the context of the COSINUS (Cohort to assess structural and individual factors in drug use) study.

RESULTS

MOUD are prescribed, respectively, to one-third and one-fifth of PWIS, whereas a half of them declared MS consumption without prescription. MS users live with higher precariousness and are younger than non-users. MS is associated with salt cocaine and heroin use. It is often consumed with methadone and more rarely with buprenorphine and we hypothesized that this is probably linked to buprenorphine's pharmacological antagonism.

DISCUSSION

Our results show the high prevalence of MS consumption and highlight the importance of considering the highly restricted possibility of prescribing MS as MOUD. Its association with methadone raises the question of their synergistic action on craving and mental disorders. The profiles of opioid users who could benefit from MS with or without methadone must be examined to improve their care but with the utmost caution, given the risk of overdose.

Characterizing the opioidergic mechanisms of repetitive transcranial magnetic stimulation-induced analgesia: a randomized controlled trial

ABSTRACT

Repetitive transcranial magnetic stimulation (rTMS) is a promising technology to reduce chronic pain. Investigating the mechanisms of rTMS analgesia holds the potential to improve treatment efficacy. Using a double-blind and placebo-controlled design at both stimulation and pharmacologic ends, this study investigated the opioidergic mechanisms of rTMS analgesia by abolishing and recovering analgesia in 2 separate stages across brain regions and TMS doses. A group of 45 healthy participants were equally randomized to the primary motor cortex (M1), the dorsolateral prefrontal cortex (DLPFC), and the Sham group. In each session, participants received an intravenous infusion of naloxone or saline before the first rTMS session. Participants then received a second dose of rTMS session after the drugs were metabolized at 90 minutes. M1-rTMS-induced analgesia was abolished by naloxone compared with saline and was recovered by the second rTMS run when naloxone was metabolized. In the DLPFC, double but not the first TMS session induced significant pain reduction in the saline condition, resulting in less pain compared with the naloxone condition. In addition, TMS over the M1 or DLPFC selectively increased plasma concentrations of β-endorphin or encephalin, respectively. Overall, we present causal evidence that opioidergic mechanisms are involved in both M1-induced and DLPFC-rTMS-induced analgesia; however, these are shaped by rTMS dosage and the release of different endogenous opioids.

Clinical Pharmacokinetics and Pharmacodynamics of Naloxone

Naloxone is a World Health Organization (WHO)-listed essential medicine and is the first choice for treating the respiratory depression of opioids, also by lay-people witnessing an opioid overdose. Naloxone acts by competitive displacement of opioid agonists at the μ-opioid receptor (MOR). Its effect depends on pharmacological characteristics of the opioid agonist, such as dissociation rate from the MOR receptor and constitution of the victim. Aim of treatment is a balancing act between restoration of respiration (not consciousness) and avoidance of withdrawal, achieved by titration to response after initial doses of 0.4-2 mg. Naloxone is rapidly eliminated [half-life (t1/2) 60-120 min] due to high clearance. Metabolites are inactive. Major routes for administration are intravenous, intramuscular, and intranasal, the latter primarily for take-home naloxone. Nasal bioavailability is about 50%. Nasal uptake [mean time to maximum concentration (Tmax) 15-30 min] is likely slower than intramuscular, as reversal of respiration lag behind intramuscular naloxone in overdose victims. The intraindividual, interindividual and between-study variability in pharmacokinetics in volunteers are large. Variability in the target population is unknown. The duration of action of 1 mg intravenous (IV) is 2 h, possibly longer by intramuscular and intranasal administration. Initial parenteral doses of 0.4-0.8 mg are usually sufficient to restore breathing after heroin overdose. Fentanyl overdoses likely require higher doses of naloxone. Controlled clinical trials are feasible in opioid overdose but are absent in cohorts with synthetic opioids. Modeling studies provide valuable insight in pharmacotherapy but cannot replace clinical trials. Laypeople should always have access to at least two dose kits for their interim intervention.

Dedicated nursing care pathway improved management of opioid-poisoned patients in the emergency department: A before-after observational study

OBJECTIVE

Opioid overdose is increasing and accounts for two-thirds of poisoning deaths. Opioid induced respiratory depression is life-threatening and can be under-recognised even in the hospital setting. We aimed to evaluate the effect of a care pathway on the management of opioid-poisoned patients.

METHODS

This is a before-after observational study following the introduction of a nursing care pathway for opioid-poisoned patients presenting to ED. Medical records were retrospectively reviewed pre (6-month period 1 year prior) and post (9-month period following) the introduction of the pathway. The primary outcome was the proportion of documented episodes of respiratory depression (respiratory rate <10 or oxygen saturation <93% on room air) receiving naloxone. Secondary outcomes were time to naloxone, number of documented observations (first 4 h) and length of stay.

RESULTS

There were 111 patients included in the study, 61 pre-intervention and 50 post-intervention (35 followed the pathway). A significantly larger proportion of patients received naloxone for respiratory depression when the pathway was used (134/200 [67%] vs 34/118 [29%], difference 38%, 95% CI 28-48%). The median time to naloxone was similar (pathway 28.5 min vs no pathway 35 min, difference -6.5 min, 95% CI -19 to 12 min). Documentation increased when the pathway was used (12.0 observations/presentation vs 7.5 observations/presentation, difference 4.5 observations/patient, 95% CI 2.1-7.0 observations/patient). Length of stay was similar (pathway 16.7 h vs no pathway 15.3 h, difference 1.4 h, 95% CI -2.4 to 5.9 h).

CONCLUSIONS

Following the introduction of a dedicated opioid poisoning nursing care pathway, naloxone delivery and observation documentation increased. A care pathway may improve ED management of opioid poisoning.

Effects of GABAB receptor blockade on lateral habenula glutamatergic neuron activity following morphine injection in the rat: an electrophysiological study

Background and purpose

The lateral habenula (LHb), a key area in the regulation of the reward system, exerts a major influence on midbrain neurons. It has been shown that the gamma-aminobutyric acid (GABA)- ergic system plays the main role in morphine dependency. The role of GABA type B receptors (GABABRs) in the regulation of LHb neural activity in response to morphine, remains unknown. In this study, the effect of GABABRs blockade in response to morphine was assessed on the neuronal activity in the LHb.

Experimental approach

The baseline firing rate was recorded for 15 min, then morphine (5 mg/kg; s.c) and phaclofen (0, 0.5, 1, and 2 μg/rat), a GABABRs' antagonist, were microinjected into the LHb. Their effects on firing LHb neurons were investigated using an extracellular single-unit recording in male rats.

Findings/Results

The results revealed that morphine decreased neuronal activity, and GABABRs blockade alone did not have any effect on the neuronal activity of the LHb. A low dose of the antagonist had no significant effect on neuronal firing rate, while blockade with doses of 1 and 2 μg/rat of the antagonist could significantly prevent the inhibitory effects of morphine on the LHb neuronal activity.

Conclusion and implications

This result indicated that GABABRs have a potential modulator effect, in response to morphine in the LHb.

Pharmacokinetic considerations for community-based dosing of nasal naloxone in opioid overdose in adults

INTRODUCTION

The administration of the opioid antagonist naloxone in the community is a measure to prevent death from opioid overdose. Approved nasal naloxone sprays deliver initial doses of 0.9 to 8 mg. The level of the initial community dose is controversial, as the scientific base is weak.In this review knowledge of the pharmacokinetics of nasal, both approved and improvised nasal sprays, and intramuscular naloxone will be utilized to evaluate dose-effect relationships in previous studies of opioid overdose outcomes.

AREAS COVERED

The aim was to present scientifically based considerations on the initial nasal naloxone doses currently available, which reasonably balances the effect and adverse outcomes, given that at least two doses are at hand. Also included in these considerations is the challenge by illicitly manufactured fentanyl and analogs.This paper is based on both peer-reviewed and grey literature identified by several searches, of such as naloxone pharmacokinetics/formulations/outcomes/emergency medical services, in PubMed and Embase.

EXPERT OPINION

There is little scientific evidence that supports the use of initial systemic dosing that exceeds 0.8 mg in the community. Higher doses increase the risk of withdrawal symptoms feared in people who use opioids. Many obstacles may reduce the potential of community-administered naloxone.

Pharmacogenetic study of methadone treatment for heroin addiction: associations between drug-metabolizing gene polymorphisms and treatment efficacy

OBJECTIVES

Opioid dependence is currently one of the most serious problems affecting the social norms and public health system. Methadone maintenance therapy (MMT) is being widely used in treating heroin-dependent patients. The mechanism of methadone metabolism and disposition has been shown to involve cytochrome P450 (CYP450) and P-glycoprotein. The aim of this study was to explore the relationships among genetic polymorphisms, BMI and effective dose of methadone used in MMT within a northern Taiwan cohort.

METHODS

One hundred heroin-dependent patients were enrolled in the study. The clinical data gathered included methadone dose, sex and BMI. DNA was collected from the oral swab of the participants to analyze the relevant alleles.

RESULTS

An effective methadone dose correlated with sex, BMI and the presence of ABCB1 2677GG (rs2032582) and CYP2B6 516GG (rs374527). Furthermore, the CYP2B6 516GG homozygote was related to a higher average dose of methadone (GG: 68.50 ± 32.43; GT: 52.28 ± 25.75; TT: 44.44 ± 29.64; P < 0.02), whereas the ABCB1 2677GG homozygote was related to a lower dose (GG: 51.09 ± 20.83; GT: 69.65 ± 37.51; TT: 62.52 ± 30.44; P < 0.05). We examined the predictive effect of polymorphisms combined with sex and BMI on methadone dose by conducting multiple linear regressions. Our data predicted the average dose of methadone in approximately 30% of heroin-dependent patients.

CONCLUSION

The interactions between genetic polymorphisms and clinical features proved useful in identifying the effective dose of MMT for heroin-dependent patients in Taiwan more precisely.

Enriched Environment Ameliorates Cognitive Deficits and Locomotor Sensitization in Morphine-Withdrawn Rats Receiving Methadone Maintenance Treatment

OBJECTIVE

This study was designed to examine whether enriched environments (EE) would attenuate object recognition and spatial learning and memory deficits and locomotor sensitization induced by methadone maintenance treatment (MMT) in morphine-withdrawn rats.

METHODS

Male Wistar rats (170 ± 10 g) were injected with bi-daily doses (10 mg/kg, 12-h intervals) of morphine for 14 days. Rats receiving MMT were reared in the standard environment (SE) or EE during 30 days of morphine withdrawal. Then, the rats were tested for object recognition (the object recognition memory test, ORMT) and spatial learning and memory (the water maze) and then challenged with morphine (1 mg/kg, i.p.) and evaluated for locomotor activity (open-field box).

RESULTS

The results revealed that the dependent/saline/EE (D/Sal/EE) and D/methadone/EE (D/Meth/EE) rats exhibited significant preference for the new object (p = 0.006 and p = 0.049), spent more time in the target zone (p = 0.045 and p = 0.005) on the water maze, and displayed a lower level of distance traveled (p = 0.002 and p = 0.0001) compared to their control groups reared in SE.

CONCLUSIONS

We conclude that exposure to EE could ameliorate the object recognition and spatial memory deficits and also decrease locomotor sensitivity in morphine-withdrawn rats receiving MMT. Thus, EE may be beneficial in the treatment of addiction during MMT.

Drugs of Abuse-Opioids, Sedatives, Hypnotics

Over the last 2 decades, prescription and nonprescription substance use has significantly increased. In this article, 3 particular drug classes-opioids, sedatives, and hypnotics-are discussed. For each class, a brief history of the agent, a description of relevant pharmacology, the clinical presentation of overdose, the management of specific drug overdoses, and a summary of salient points are presented. The intent is to provide a clinically relevant and comprehensive approach to understanding these potential substance exposures in order to provide a framework for management of opioid, sedative, and hypnotic overdoses.

Impact of the Opioid Epidemic

In recent years the prescription opioid overdose epidemic has decreased, but has been more than offset by increases in overdose caused by fentanyl and fentanyl analogues. Opioid overdose patients should receive naloxone if they have significant respiratory depression and/or loss of protective airway reflexes. Patients who receive naloxone should be observed for recurrent opioid effects. Patients with opioid overdose may be admitted to the intensive care unit for naloxone infusions, treatment of noncardiogenic pulmonary edema, autonomic instability, or sequelae of hypoxia-ischemia or cardiac arrest. Primary and secondary prevention are important to reduce the number of people with life-threatening opioid overdose.

Evaluation of analgesic interaction between morphine, maropitant and dexmedetomidine in dogs undergoing ovariohysterectomy

ABSTRACTAims: To compare the analgesic effect of morphine combined with maropitant and/or dexmedetomidine to morphine alone but at a higher dose, and to evaluate the pharmacokinetics of the drug combinations, in dogs undergoing ovariohysterectomy (OHE).Methods: Forty client-owned dogs were randomised into four treatment groups (n = 10 per group) each to receive a different analgesic protocol. After premedication with I/M acepromazine, anaesthesia was induced with propofol to effect and maintained with isoflurane in 100% oxygen delivered via a circle system. The heart rate, respiratory rate, blood pressure, haemoglobin oxygen saturation, end-tidal partial pressure of carbon dioxide, electrocardiogram and rectal temperature were monitored during anaesthesia. The test drugs (Mor: 0.6 mg/kg morphine; Maro + Mor: 0.3 mg/kg morphine and 1 mg/kg maropitant; Dex + Mor: 0.3 mg/kg morphine and 10 μg/kg dexmedetomidine; Dex + Maro + Mor: 0.2 mg/kg morphine, 7 μg/kg dexmedetomidine and 0.7 mg/kg maropitant) were administered I/M after induction of anaesthesia and 30 minutes before the expected start time of ovariohysterectomy, which was carried out by veterinary students under veterinary supervision. The short form of the Glasgow composite measure pain scale (CMPS-SF) and visual analogue scale (VAS) were used for pain assessment at 15 and 30 minutes and 1, 2, 3, 6, 9 and 24 hours after extubation. Dogs with CMPS-SF pain score ≥ 6 received rescue analgesia with S/C buprenorphine (0.02 mg/kg). Blood samples were collected before, 15, 30, 60 and 120 minutes after injection of the test drugs and concentration of the test drugs in plasma was determined by liquid chromatography-mass spectrometry.Results: Dogs that received Dex + Mor had significantly lower CMPS-SF (estimate of difference = -1.53 (SE 0.58); p = 0.010) and VAS (estimate of difference = -0.67 (SE 0.25); p = 0.007) scores compared to the dogs that received morphine alone. There was no evidence of a difference in the number of dogs requiring rescue between groups. All dogs that received dexmedetomidine showed cardiac arrhythmia and second-degree heart block. Mean (SD) maximum concentrations (C_max,) of morphine in plasma were 6.8 (4.56), 9.56 (8.29), 9.30 (3.35) and 18.99 (9.41) ng/mL for the groups Dex + Mor, Dex + Maro + Mor, Maro + Mor and Mor respectively. The C_max of morphine was significantly lower in the Dex + Mor (p = 0.004), Dex + Maro + Mor (p = 0.034) and Maro + Mor (p = 0.018) groups compared to the Mor group.Conclusions For dogs undergoing ovariohysterectomy, lower doses of morphine (0.2 and 0.3 mg/kg) combined with dexmedetomidine or maropitant may provide analgesia equivalent to or better than morphine when given alone at a higher dose (0.6 mg/kg).Abbreviations: AUC: Area under curve; C_max: Maximum concentration in plasma; CMPS-SF: Glasgow composite measure pain scale - short form; NK1: Neurokinin-1; OHE: Ovariohysterectomy; T_max: Time to C_max; T_1/2: Half-life of terminal elimination phase; VAS: Visual analogue scale.

Evaluation of functional status among patients undergoing maintenance treatments for opioid use disorders

Background

Methadone and buprenorphine are the most prevalent types of opioid maintenance programs in Andalusia. The main objective is comparing the functional status of patients with pharmacological opioid maintenance treatments according to different socio-demographic characteristic, health and disabilities domains and sexual difficulties.

Methods

A total of 593 patients from the Andalusia community, 329 were undergoing methadone treatment and 264 were undergoing buprenorphine treatment. The patients were interviewed by socio-demographic and opioid-related variables, assessed by functioning, disability and health domains (WHODAS 2.0.) and for sexual problems (PRSexDQ-SALSEX).

Results

We found significant differences in the socio-demographic and the opioid-related variables as the onset of opioid use, being on previous maintenance programs, opioid intravenous use, the length of previous maintenance programs, polydrug use and elevated seroprevalence rates (HCV and HIV) between the methadone group and the buprenorphine group. Regarding health and disability domains there were differences in the Understanding and communication domain, Getting around domain, Participation in society domain and in the WHODAS 2.0. simple and complex score, favoring buprenorphine-treated patients. The methadone group referred elevated sexual impairments compared with the buprenorphine group. Opioid-related variables as seroprevalence rates, other previous lifetime maintenance program, the daily opioid dosage and the daily alcohol use are the most discriminative variables between both groups. Participation in society variables and sexual problems were the most important clinical variables in distinguishing the methadone group from the buprenorphine group regarding their functional status.

Conclusions

The methadone group showed higher prevalence in opioid dependence-related variables, elevated disabilities in participation in society activities and sexual problems compared with the buprenorphine group. This study shows the importance of carry out a functional evaluation in the healthcare follow-up, especially in those areas related with social activity and with sexual problems.

Chronic morphine administration differentially modulates viral reservoirs in SIVmac251 infected rhesus macaque model

HIV persists in cellular reservoirs despite effective combined antiretroviral therapy (cART) and there is viremia flare up upon therapy interruption. Opioids modulate the immune system and suppress antiviral gene responses, which significantly impact people living with HIV (PLWH). However, the effect of opioids on viral reservoir dynamics remain elusive. Herein, we developed a morphine dependent SIVmac251 infected Rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. RMs on a morphine (or saline control) regimen were infected with SIVmac251. The cART was initiated in approximately half the animals five weeks post-infection, and morphine/saline administration continued until the end of the study. Among the untreated RM, we did not find any difference in plasma/CSF or in cell-associated DNA/RNA viral load in anatomical tissues. On the other hand, within the cART suppressed macaques, there was a reduction in cell-associated DNA load, intact proviral DNA levels, and in inducible SIV reservoir in lymph nodes (LNs) of morphine administered RMs. In distinction to LNs, in the CNS, the size of latent SIV reservoirs was higher in the CD11b+ microglia/macrophages in morphine dependent RMs. These results suggest that in the proposed model, morphine plays a differential role in SIV reservoirs by reducing the CD4+ T-cell reservoir in lymphoid tissues, while increasing the microglia/reservoir size in CNS tissue. The findings from this pre-clinical model will serve as a tool for screening therapeutic strategies to reduce/eliminate HIV reservoirs in opioid dependent PLWH.IMPORTANCE Identification and clearance of HIV reservoirs is a major challenge in achieving a cure for HIV. This is further complicated by co-morbidities that may alter the size of the reservoirs. There is an overlap between the risk factors for HIV and opioid abuse. Opiates have been recognized as prominent co-morbidities in HIV-infected populations. People infected with HIV also abusing opioids have immune modulatory effects and more severe neurological disease. However, the impact of opioid abuse on HIV reservoirs remains unclear. In this study, we used morphine dependent SIVmac251 infected rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. Our studies suggested that people with HIV who abuse opioids had higher reservoirs in CNS than the lymphoid system. Extrapolating the macaque findings in humans suggests that such differential modulation of HIV reservoirs among people living with HIV abusing opioids could be considered for future HIV cure research efforts.

Potential implications of DMET ontogeny on the disposition of commonly prescribed drugs in neonatal and pediatric intensive care units

Introduction: Pediatric patients, especially neonates and infants, are more susceptible to adverse drug events as compared to adults. In particular, immature small molecule drug metabolism and excretion can result in higher incidences of pediatric toxicity than adults if the pediatric dose is not adjusted.Area covered: We reviewed the top 29 small molecule drugs prescribed in neonatal and pediatric intensive care units and compiled the mechanisms of their metabolism and excretion. The ontogeny of Phase I and II drug metabolizing enzymes and transporters (DMETs), particularly relevant to these drugs, are summarized. The potential effects of DMET ontogeny on the metabolism and excretion of the top pediatric drugs were predicted. The current regulatory requirements and recommendations regarding safe and effective use of drugs in children are discussed. A few representative examples of the use of ontogeny-informed physiologically based pharmacokinetic (PBPK) models are highlighted.Expert opinion: Empirical prediction of pediatric drug dosing based on body weight or body-surface area from the adult parameters can be inaccurate because DMETs are not mature in children and the age-dependent maturation of these proteins is different. Ontogeny-informed-PBPK modeling provides a better alternative to predict the pharmacokinetics of drugs in children.

The relationship between early administration of morphine or nitrous oxide gas and PTSD symptom development

BACKGROUND

Posttraumatic Stress Disorder (PTSD) is a debilitating mental health disorder. Certain drugs, such as morphine and nitrous oxide gas (N₂O), are administered to individuals who just experienced a traumatic event (e.g., soldiers, injured civilians). It is therefore crucial to understand if they incidentally affect PTSD symptom development. Furthermore, such observations could pave the way for the development of pharmacological prevention strategies of PTSD.

METHODS

In this prospective population-based cohort study (n = 2,070), we examined the relationship between morphine or N₂O administration during childbirth, and subsequent childbirth-related PTSD symptoms at eight weeks postpartum. Pain during labour, prior PTSD symptoms, and birth medical severity were included as covariates in the analyses.

RESULTS

In women who developed PTSD symptoms, N₂O administration during childbirth predicted reduced PTSD symptom severity (p < .001, small to medium effect size). A similar tendency was observed for morphine, but was not significant (p < .065, null to small effect size). Both drugs predicted increased PTSD symptoms when combined with severe pain during labour.

LIMITATIONS

This study was observational, thus drug administration was not randomised. Additionally, PTSD symptoms were self-reported.

CONCLUSIONS

Peritraumatic N₂O administration may reduce subsequent PTSD symptom severity and thus be a potential avenue for PTSD secondary prevention. This might also be the case for morphine. However, the role of severe peritraumatic pain in context of drug administration deserves further investigation.

Effect of the morphine/heroin vaccine on opioid and non-opioid drug-induced antinociception in mice

Pain is a common symptom in patients with opioid use disorder (OUD), which increases synthetic and illicit synthetic opioid abuse and even fatalities due to opioid overdose. Many FDA-approved drugs are available for the treatment of OUD, however, the use of these medications is limited, mainly due to the development of various side effects. Active vaccination is a new therapeutic approach but the resulting antibodies may compromise the use and efficiency of opioid and non-opioid drugs. In this study, we evaluated whether the antibodies produced by the morphine/heroin vaccine (M-TT) would alter the antinociceptive effects of opioid and non-opioid drugs. Female Balb-c mice were immunized with the M-TT vaccine. A solid-phase antibody-capture ELISA was used for monitoring antibody titer responses after each booster dose in vaccinated animals, followed by tail-flick testing. This study found that the M-TT vaccine did not affect the antinociception induced by different doses of morphine or the ability of non-opioid and synthetic opioid drugs to decrease thermal pain. Moreover, the combination of vaccination and naloxone increased the time-course of morphine antagonism relative to either vaccination or naloxone alone. These results suggest that the antibody titers generated by the M-TT vaccine 1) are capable of reducing morphine-induced antinociception and 2) are selective enough not to alter antinociception induced by non-opioid or synthetic drugs. These characteristics support its potential as a treatment agent for patients with symptoms of pain comorbid to OUD.

Sublingual buprenorphine-naloxone precipitated withdrawal-A case report with review of literature and clinical considerations

Buprenorphine- Naloxone Fixed Dose Combination (BNX) is widely used to manage opioid use disorders. Contrary to evidence based concepts about sublingual bio-availability of naloxone, a few small studies have reported non-negligible amounts absorbed sublingually. But the extent to which these amounts exert opioid antagonist effects is yet to be established. We hereby report the first case of opioid dependence who developed a rare phenomenon of moderate to severe opioid withdrawal symptoms on administration of sublingual BNX after several days of being stabilized on plain buprenorphine (BUP). The case demonstrates the need to consider using buprenorphine monotherapy whenever such adverse effects are encountered. We also discuss the possible pharmacological explanations behind this rare side effect.

Effect of combinations of morphine, dexmedetomidine and maropitant on the electroencephalogram in response to acute electrical stimulation in anaesthetized dogs

This study was conducted to compare the efficacy of combinations of morphine, dexmedetomidine and maropitant in preventing the changes in electroencephalographic (EEG) indices of nociception in anaesthetized dogs subjected to a noxious electrical stimulus. In a crossover study, eight healthy adult dogs were randomly allocated to four groups: Mor: morphine 0.6 mg/kg; Dex + Mor: morphine 0.3 mg/kg + dexmedetomidine 5 μg/kg; Maro + Mor: morphine 0.3 mg/kg + maropitant 1 mg/kg; and Dex + Maro + Mor: morphine 0.2 mg/kg + dexmedetomidine 3 μg/kg + maropitant 0.7 mg/kg. Following intramuscular administration of test drugs in a minimal anaesthesia model, a supramaximal electrical stimulus (50 V at 50 Hz for 2 s) was applied and the EEG data were recorded. There were significant increases (p < .05) in the poststimulus median frequency (F50) only in groups Mor and Maro + Mor. Dex + Mor group had a significantly lower change in F50 and F95 compared to all other treatment groups. There was no correlation of the changes in EEG frequencies with blood plasma concentration of the drugs during and after noxious stimulation. Combination of dexmedetomidine and morphine was most effective in abolishing the changes in EEG indices in response to a noxious stimulus indicating a supra-additive interaction between these two drugs.

Mass Spectrometric Imaging of the Brain Demonstrates the Regional Displacement of 6-Monoacetylmorphine by Naloxone

Overdose is the main cause of mortality among heroin users. Many of these overdose-induced deaths can be prevented through the timely administration of naloxone (NLX), a nonselective mu (μ)-, kappa (κ)-, and delta (δ)-opioid receptor antagonist. NLX competitively inhibits opioid-overdose-induced respiratory depression without eliciting any narcotic effect itself. The aim of this study was to investigate the antagonistic action of NLX by comparing its distribution to that of 6-monacetylmorphine (6-MAM), heroin's major metabolite, in a rodent model using mass spectrometric imaging (MSI) in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Male Sprague-Dawley rats (n = 5) received heroin (10 mg kg^-1) intraperitoneally, NLX (10 mg kg^-1) intranasally, and NLX injected intranasally 5 min after heroin administration. The animals were sacrificed 15 min after dose and brain tissues were harvested. The MSI image analysis showed a region-specific distribution of 6-MAM in the brain regions including the corpus callosum, hippocampal formation, cerebral cortex, corticospinal tracts, caudate putamen, thalamus, globus pallidus, hypothalamus, and basal forebrain regions of the brain. The antagonist had a similar biodistribution throughout the brain in both groups of animals that received NLX or NLX after heroin administration. The MSI analysis demonstrated that the intensity of 6-MAM in these brain regions was reduced following NLX treatment. The decrease in 6-MAM intensity was caused by its displacement by the antagonist and its binding to these receptors in these specific brain regions, consequently enhancing the opioid elimination. These findings will contribute to the evaluation of other narcotic antagonists that might be considered for use in the treatment of drug overdose via MSI.

Depression and Outcomes of Methadone and Buprenorphine Treatment Among People with Opioid Use Disorders: A Literature Review

Objective: Depression is the most common psychiatric comorbidity among people with opioid use disorders (OUDs). However, whether and how comorbid depression is associated with the outcomes of opioid agonist therapy (OAT) remains poorly understood. The objective of this review was to identify and describe the association between depression and main outcomes (opioid use and treatment retention) of methadone and buprenorphine treatment among people with OUDs. Methods: A literature review was conducted by searching five electronic databases (MEDLINE, PubMed, Embase, Evidence-Based Medicine Reviews [EBMR], and Cumulative Index of Nursing and Allied Health Literature [CINAHL] Complete) from January 1970 to April 2019. Two independent reviewers screened titles and abstracts of the identified records by using pre-established eligibility criteria. Next, full texts were reviewed and studies that met inclusion criteria were selected. Finally, a descriptive synthesis of extracted data was performed. Results: In total, 12,296 records were identified and 18 studies that met inclusion criteria were retained. Of these, six studies reported reduced opioid use and seven reported increased opioid use during methadone or buprenorphine treatment. In addition, three studies reported an increased retention rate and four documented a decreased retention rate during methadone or buprenorphine treatment. The remaining studies did not find any significant association between depression and opioid use or treatment retention. Overall, the evidence did not demonstrate a consistent association between depression and outcomes of methadone or buprenorphine treatment. Conclusions: Although the inconsistent nature of the current evidence prohibited us from drawing definitive conclusions, we posit that the presence of depression among OUDs patients may not always predict negative outcomes related to retention and drug use during the course of OAT. Particularly, the hypothesis that adequate treatment of depression can improve treatment retention is promising and is in line with the call for increased efforts to provide integrated care for comorbid mental health disorders and addiction. Future studies with rigorous methodology are essential to better characterize the complex interplay between depression, OAT, and OUDs.

Take-Home Naloxone for the Emergency Interim Management of Opioid Overdose: The Public Health Application of an Emergency Medicine

Naloxone is a well-established essential medicine for the treatment of life-threatening heroin/opioid overdose in emergency medicine. Over two decades, the concept of 'take-home naloxone' has evolved, comprising pre-provision of an emergency supply to laypersons likely to witness an opioid overdose (e.g. peers and family members of people who use opioids as well as non-medical personnel), with the recommendation to administer the naloxone to the overdose victim as interim care while awaiting an ambulance. There is an urgent need for more widespread naloxone access considering the growing problem of opioid overdose deaths, accounting for more than 100,000 deaths worldwide annually. Rises in mortality are particularly sharp in North America, where the ongoing prescription opioid problem is now overlaid with a rapid growth in overdose deaths from heroin and illicit fentanyl. Using opioids alone is dangerous, and the mortality risk is clustered at certain times and contexts, including on prison release and discharge from hospital and residential care. The provision of take-home naloxone has required the introduction of new legislation and new naloxone products. These include pre-filled syringes and auto-injectors and, crucially, new concentrated nasal sprays (four formulations recently approved in different countries) with speed of onset comparable to intramuscular naloxone and relative bioavailability of approximately 40-50%. Choosing the right naloxone dose in the fentanyl era is a matter of ongoing debate, but the safety margin of the approved nasal sprays is superior to improvised nasal kits. New legislation in different countries permits over-the-counter sales or other prescription-free methods of provision. However, access remains uneven with take-home naloxone still not provided in many countries and communities, and with ongoing barriers contributing to implementation inertia. Take-home naloxone is an important component of the response to the global overdose problem, but greater commitment to implementation will be essential, alongside improved affordable products, if a greater impact is to be achieved.

Developing a clinical decision support for opioid use disorders: a NIDA center for the clinical trials network working group report

There is an urgent need for strategies to address the US epidemic of prescription opioid, heroin and fentanyl-related overdoses, misuse, addiction, and diversion. Evidence-based treatment such as medications for opioid use disorder (MOUD) are available but lack numbers of providers offering these services to meet the demands. Availability of electronic health record (EHR) systems has greatly increased and led to innovative quality improvement initiatives but this has not yet been optimized to address the opioid epidemic or to treat opioid use disorder (OUD). This report from a clinical decision support (CDS) working group convened by the NIDA Center for the Clinical Trials Network aims to converge electronic technology in the EHR with the urgent need to improve screening, identification, and treatment of OUD in primary care settings through the development of a CDS algorithm that could be implemented as a tool in the EHR. This aim is consistent with federal, state and local government and private sector efforts to improve access and quality of MOUD treatment for OUD, existing clinical quality and HEDIS measures for OUD or drug and alcohol use disorders, and with a recent draft grade B recommendation from the US Preventative Services Task Force (USPSTF) for screening for illicit drug use in adults when appropriate diagnosis, treatment and care services can be offered or referred. Through a face-to-face expert panel meeting and multiple follow-up conference calls, the working group drafted CDS algorithms for clinical care felt to be essential for screening, diagnosis, and management of OUD in primary care. The CDS algorithm was reviewed by addiction specialists and primary care providers and revised based on their input. A clinical decision support tool for OUD screening, assessment, and treatment within primary care systems may help improve healthcare delivery to help address the current epidemic of opioid misuse and overdose that has outpaced the capacity of specialized treatment settings. A semi-structured outline of clinical decision support for OUD was developed to facilitate implementation within the EHR. Further work for adaptation at specific sites and for testing is needed.

Critical Care Pain Management in Patients Affected by the Opioid Epidemic: A Review

The rapid rise in the opioid epidemic has had a deleterious impact across the United States. This increase has drawn the attention of the critical care community not only because of the surge in acute opioid overdose-related admissions, but also due to the increase in the number of opioid-dependent and opioid-tolerant patients being treated in the intensive care unit (ICU). Opioid-related issues relevant to the critical care physician include direct care of patients with opioid overdoses, the provision of sufficient analgesia to patients with opioid dependence and tolerance, and the task of preventing long-term opioid dependence in patients who survive ICU care. This review identifies the challenges facing the ICU physician working with patients presenting with opioid-related complications, discusses current solutions, and suggests future areas of research and heightened ICU clinician attention.

Fentanyls and the safety of first responders: Science and recommendations

Opioids have many beneficial uses in medicine, but, taken inappropriately, they can cause life-threatening health effects. The increasing use of physician-prescribed and illicit opioids, including highly potent fentanyl and its analogs, have contributed to a significant increase in opioid-related drug overdoses in the United States, leading to a public health emergency. There have been a number of reports describing adverse health effects experienced by police officers, fire-fighter emergency medical services providers, and private sector ambulance personnel when responding to drug overdose incidents. Several sets of exposure prevention recommendations for first responders are available from government and the private sector. Understanding the scientific basis for these recommendations, increasing awareness by responders of the potential risks associated with opioid exposure during a response, and educating responders about safe work practices when exposure to opioids is suspected or confirmed are all critical prevention measures that can keep first responders safe.

Pain Therapy Guided by Purpose and Perspective in Light of the Opioid Epidemic

Prescription opioid misuse is an ongoing and escalating epidemic. Although these pharmacological agents are highly effective analgesics prescribed for different types of pain, opioids also induce euphoria, leading to increasing diversion and misuse. Opioid use and related mortalities have developed in spite of initial claims that OxyContin, one of the first opioids prescribed in the USA, was not addictive in the presence of pain. These claims allayed the fears of clinicians and contributed to an increase in the number of prescriptions, quantity of drugs manufactured, and the unforeseen diversion of these drugs for non-medical uses. Understanding the history of opioid drug development, the widespread marketing campaign for opioids, the immense financial incentive behind the treatment of pain, and vulnerable socioeconomic and physical demographics for opioid misuse give perspective on the current epidemic as an American-born problem that has expanded to global significance. In light of the current worldwide opioid epidemic, it is imperative that novel opioids are developed to treat pain without inducing the euphoria that fosters physical dependence and addiction. We describe insights from preclinical findings on the properties of opioid drugs that offer insights into improving abuse-deterrent formulations. One finding is that the ability of some agonists to activate one pathway over another, or agonist bias, can predict whether several novel opioid compounds bear promise in treating pain without causing reward among other off-target effects. In addition, we outline how the pharmacokinetic profile of each opioid contributes to their potential for misuse and discuss the emergence of mixed agonists as a promising pipeline of opioid-based analgesics. These insights from preclinical findings can be used to more effectively identify opioids that treat pain without causing physical dependence and subsequent opioid abuse.

Buprenorphine alone or with naloxone: Which is safer?

To address concerns regarding the intravenous diversion of buprenorphine, a combined buprenorphine-naloxone (BUP-NLX) preparation was developed. The aim of this study is to compare health outcomes in opioid dependent patients treated with BUP and BUP-NLX. All patients treated with BUP and/or BUP-NLX in Western Australia between 2001 and 2010 were included in the study ( N = 3455). Patients were identified via State prescribing records and matched against the State mortality, hospital, and emergency department records. Rates of health events were examined and compared using Cox Proportional Hazard Models and Generalized Estimating Equations. While on treatment there was no significant difference between mortality rates in the two groups, mortality rates following the cessation of treatment were significantly higher in patients treated with BUP-NLX (adjusted hazard ratio: 1.59). Rates of hospitalization were significantly elevated in BUP-NLX patients (adjusted odds ratio: 1.17) compared with BUP treated patients; however, rates of hospitalization with a skin/subcutaneous diagnosis were significantly lower in BUP-NLX treated patients (adjusted odds ratio: 0.65). Off-treatment rates of both all-cause hospital admissions (adjusted odds ratio: 1.53) and hospital admissions with an opioid poisoning diagnosis (adjusted odds ratio: 1.59) were significantly elevated in BUP-NLX treated patients compared with BUP treated patients. The addition of naloxone does not appear to improve the safety profile of buprenorphine.

Dispensing Naloxone Without a Prescription: Survey Evaluation of Ohio Pharmacists

Background:

The Centers for Disease Control and Prevention (CDC) reports a 200% escalation in the rate of opioid overdose deaths in the United States. Unfortunately, Ohio has been deemed the epicenter of the nation’s opioid epidemic. In 2015, Ohio passed a bill that permits a pharmacist to distribute naloxone without a prescription.

Objectives:

This survey was aimed to discover pharmacists’ knowledge of naloxone and Ohio law, perceived barriers that may prohibit naloxone dispensing, and Ohio pharmacists’ general confidence, comfort, perception, and experience dispensing naloxone per physician protocol.

Methods:

Pharmacists’ knowledge of naloxone and Ohio law pertaining to dispensing naloxone; perceived barriers to naloxone distribution; and overall experience, willingness, comfort, and perceptions of personally supplying naloxone were assessed using multiple-choice and Likert-type scale questions through an e-mail survey.

Results:

Overall, Ohio pharmacists were knowledgeable about naloxone and displayed confidence in their training and ability to provide patient education on naloxone. Pharmacists were less certain about Ohio law pertaining to naloxone distribution, especially those who have been in practice longer. Pharmacists indicated several barriers to dispensing naloxone and the need for more training. Younger pharmacists were more likely to report a concern with clientele who would frequent their pharmacy and moral and ethical concerns as barriers to dispensing naloxone.

Conclusion:

Additional educational programs should be delivered to Ohio pharmacists to inform them of the state law and policies. Continuing education programs that review substance abuse and attempt to reduce social stigma may assist with increasing naloxone distribution to those in need, especially, if directed toward younger pharmacists in Ohio.

Naloxone dosage for opioid reversal: current evidence and clinical implications

Opioid-related mortality is a growing problem in the United States, and in 2015 there were over 33,000 opioid-related deaths. To combat this mortality trend, naloxone is increasingly being utilized in a pre-hospital setting by emergency personnel and prescribed to laypersons for out-of-hospital administration. With increased utilization of naloxone there has been a subsequent reduction in mortality following an opioid overdose. Reversal of opioid toxicity may precipitate an opioid-withdrawal syndrome. At the same time, there is a risk of inadequate response or re-narcotization after the administration of a single dose of naloxone in patients who have taken large doses or long-acting opioid formulations, as the duration of effect of naloxone is shorter than that of many opioid agonists. As out-of-hospital use of this medication is growing, so too is concern about effective but safe dosing.

Naloxone administration for suspected opioid overdose: An expanded scope of practice by a basic life support collegiate-based emergency medical services agency

Opioid abuse is a growing and significant public health concern in the United States. Naloxone is an opioid antagonist that can rapidly reverse the respiratory depression associated with opioid toxicity. Georgetown University's collegiate-based emergency medical services (EMS) agency recently adopted a protocol, allowing providers to administer intranasal naloxone for patients with suspected opioid overdose. While normally not within the scope of practice of basic life support prehospital agencies, the recognition of an increasing epidemic of opioid abuse has led many states, including the District of Columbia, to expand access to naloxone for prehospital providers of all levels of training. In particular, intranasal naloxone is a method of administering this medication that potentially avoids needlestick injuries among EMS providers. Universities with collegiate-based EMS agencies are well positioned to provide life-saving treatments for patients acutely ill from opioid overdose.

Evaluation of Analgesic Activity of Papaver libanoticum Extract in Mice: Involvement of Opioids Receptors

Papaver libanoticum is an endemic plant to Lebanese region (family Papaveraceae) that has not been investigated before. The present study aimed to explore the analgesic activity of dried ethanolic extract of Papaver libanoticum (PLE) using tail flick, hot plate, and acetic acid induced writhing models in mice. The involvement of opioid receptors in the analgesic mechanism was investigated using naloxone antagonism. Results demonstrated that PLE exhibited a potent dose dependent analgesic activity in all tested models for analgesia. The analgesic effect involved activation of opioid receptors in the central nervous system, where both spinal and supraspinal components might be involved. The time course for analgesia revealed maximum activity after three hours in both tail flick and hot plate methods, which was prolonged to 24 hours. Metabolites of PLE could be responsible for activation of opioid receptors. The EC50 of PLE was 79 and 50 mg/kg in tail flick and hot plate tests, respectively. The total coverage of analgesia by PLE was double that of morphine in both tests. In conclusion, PLE proved to have opioid agonistic activity with a novel feature of slow and prolonged effect. The present study could add a potential tool in the armaments of opioid drugs as a natural potent analgesic and for treatment of opioid withdrawal syndrome.

Chronic Pain Management with Opioids in Patients with Past or Current Substance Abuse Problems

Among patients who present to medical providers with chronic pain complaints, there is an elevated prevalence of illicit substance use and prescription misuse. For those with legitimate pain, this predicament potentiates the risk of being medically underserved or undertreated. Complicating factors include a lack of specificity and sensitivity to the issue of defining substance abuse or misuse in the health care setting. Irrespective of whether patients have histories of addiction, problematic behavior manifests during the course of chronic pain therapy, making a conceptualization of the nature and function of this behavior difficult. The objective of this article is to highlight known confounds in the assessment of “normal” pain-related vs. substance abuse behavior. Our aim is to offer important points to consider, a set of systematic guidelines to follow, and an armamentarium of essential tools to facilitate contingency management planning in the context of treating chronic pain with controlled substances.

Stress induces analgesia via orexin 1 receptor-initiated endocannabinoid/CB1 signaling in the mouse periaqueductal gray

The orexin system consists of orexin A/hypocretin 1 and orexin B/hypocretin 2, and OX1 and OX2 receptors. Our previous electrophysiological study showed that orexin A in the rat ventrolateral periaqueductal gray (vlPAG) induced antinociception via an OX1 receptor-initiated and endocannabinoid-mediated disinhibition mechanism. Here, we further characterized antinociceptive effects of orexins in the mouse vlPAG and investigated whether this mechanism in the vlPAG can contribute to stress-induced analgesia (SIA) in mice. Intra-vlPAG (i.pag.) microinjection of orexin A in the mouse vlPAG increased the hot-plate latency. This effect was mimicked by i.pag. injection of WIN 55,212-2, a CB1 agonist, and antagonized by i.pag. injection of the antagonist of OX1 (SB 334867) or CB1 (AM 251), but not OX2 (TCS-OX2-29) or opioid (naloxone), receptors. [Ala(11), D-Leu(15)]-orexin B (i.pag.), an OX2 selective agonist, also induced antinociception in a manner blocked by i.pag. injection of TCS-OX2-29, but not SB 334867 or AM 251. Mice receiving restraint stress for 30 min showed significantly longer hot-plate latency, more c-Fos-expressing orexin neurons in the lateral hypothalamus and higher orexin levels in the vlPAG than unrestrained mice. Restraint SIA in mice was prevented by i.pag. or intraperitoneal injection of SB 334867 or AM 251, but not TCS-OX2-29 or naloxone. These results suggest that during stress, hypothalamic orexin neurons are activated, releasing orexins into the vlPAG to induce analgesia, possibly via the OX1 receptor-initiated, endocannabinoid-mediated disinhibition mechanism previously reported. Although activating either OX1 or OX2 receptors in the vlPAG can lead to antinociception, only OX1 receptor-initiated antinociception is endocannabinoid-dependent.

Intranasal buprenorphine alone and in combination with naloxone: Abuse liability and reinforcing efficacy in physically dependent opioid abusers

BACKGROUND

Buprenorphine can be abused by the intranasal route. This study sought to examine the relative abuse liability and reinforcing efficacy of intranasal buprenorphine compared to intranasal buprenorphine/naloxone in opioid-dependent individuals.

METHODS

Eleven healthy male and female volunteers physically dependent on short-acting opioids resided as inpatients during participation in this double blind, within subject, placebo-controlled study. Participants were maintained on oxycodone (30 mg/q.i.d., p.o.) throughout the 6-week study. Eight pairs of experimental sessions were conducted at ≥48 h intervals to examine the pharmacodynamic profile (Sample) and reinforcing efficacy (Self-administration the following day) of intranasal placebo, oxycodone (60 mg), buprenorphine (2, 8 & 16 mg) and buprenorphine/naloxone (2/0.5, 8/2 & 16/4 mg). Subjective, observer-rated and physiological measures were collected to assess the magnitude of opioid agonist and antagonist effects. A progressive ratio self-administration procedure assessed choices for drug versus money.

RESULTS

All active doses produced opioid agonist-like effects (e.g., increased ratings of "liking," and miosis) compared to placebo. The effects of buprenorphine and buprenorphine/naloxone were not reliably dose-dependent. Intranasal buprenorphine/naloxone elicited modest and transient opioid withdrawal-like effects in the first hour post-drug administration, while simultaneously blunting or blocking the early onset of agonist effects seen with buprenorphine alone. All active doses of buprenorphine were self-administered more than placebo, but buprenorphine/naloxone doses were not.

CONCLUSIONS

These data confirm that intranasal buprenorphine/naloxone has deterrent properties related to transient withdrawal effects that likely decrease its desirability for misuse compared to buprenorphine in opioid-dependent individuals maintained on short-acting opioids.

Effect of a high-dose target-controlled naloxone infusion on pain and hyperalgesia in patients following groin hernia repair: study protocol for a randomized controlled trial

Background

Central sensitization is modulated by the endogenous opioid system and plays a major role in the development and maintenance of pain. Recent animal studies performed following resolution of inflammatory pain showed reinstatement of tactile hypersensitivity induced by administration of a mu-opioid-antagonist, suggesting latent sensitization is mediated by endogenous opioids. In a recent crossover study in healthy volunteers, following resolution of a first-degree burn, 4 out of 12 volunteers developed large secondary areas of hyperalgesia areas after a naloxone infusion, while no volunteer developed significant secondary hyperalgesia after the placebo infusion. In order to consistently demonstrate latent sensitization in humans, a pain model inducing deep tissue inflammation, as used in animal studies, might be necessary. The aim of the present study is to examine whether a high-dose target-controlled naloxone infusion can reinstate pain and hyperalgesia following recovery from open groin hernia repair and thus consistently demonstrate opioid-mediated latent sensitization in humans.

Methods/Design

Patients submitted to unilateral, primary, open groin hernia repair will be included in this randomized, placebo-controlled, double-blind, crossover study. The experimental days take place 6–8 weeks after surgery, time-points at which patients are expected to be almost pain- free. Prior to administration of naloxone or placebo, the primary outcome (a summated measure of pain: at rest, during transition from supine to standing position, and evoked by pressure algometry) and the secondary outcomes (secondary hyperalgesia/allodynia, pressure pain thresholds, assessed at the surgical site and at the mirror-site in the contralateral groin, and, opioid withdrawal symptoms) will be assessed. These assessments will be repeated at each step of the target-controlled infusion of placebo or naloxone at estimated median (95 % CI) plasma concentrations of 344 ng/ml (130;567), 1059 ng/ml (400;1752) and 3196 ng/ml (1205;5276).

Discussion

We aim to demonstrate opioid-mediated latent sensitization in a post-surgical setting, using pain as a clinical relevant variable. Impairment of the protective endogenous opioid system may play an important role in the transition from acute to chronic pain. In order to sufficiently block the endogenous opioid system, a high-dose target-controlled naloxone-infusion is used, in accordance with recent findings in animal studies.

Trial registration number

EUDRACT: 2015-000793-36 (Registration date: 16 February 2015)

Clinicaltrials.gov: NCT01992146 (Registration date: 12 December 2014)

Orienting patients to greater opioid safety: models of community pharmacy-based naloxone

The leading cause of adult injury death in the USA is drug overdose, the majority of which involves prescription opioid medications. Outside of the USA, deaths by drug overdose are also on the rise, and overdose is a leading cause of death for drug users. Reducing overdose risk while maintaining access to prescription opioids when medically indicated requires careful consideration of how opioids are prescribed and dispensed, how patients use them, how they interact with other medications, and how they are safely stored. Pharmacists, highly trained professionals expert at detecting and managing medication errors and drug-drug interactions, safe dispensing, and patient counseling, are an under-utilized asset in addressing overdose in the US and globally. Pharmacies provide a high-yield setting where patient and caregiver customers can access naloxone—an opioid antagonist that reverses opioid overdose—and overdose prevention counseling. This case study briefly describes and provides two US state-specific examples of innovative policy models of pharmacy-based naloxone, implemented to reduce overdose events and improve opioid safety: Collaborative Pharmacy Practice Agreements and Pharmacy Standing Orders.

The effects of morphine, naloxone, and κ opioid manipulation on endocrine functioning and social behavior in monogamous titi monkeys (Callicebus cupreus)

The μ opioid receptor (MOR) and κ opioid receptor (KOR) have been implicated in pair-bond formation and maintenance in socially monogamous species. Utilizing monogamous titi monkeys (Callicebus cupreus), the present study examined the potential role opioids play in modulating the response to separation, a potent challenge to the pair-bond. In Experiment 1, paired male titi monkeys were separated from their pair-mate for 30-min and then received saline, naloxone (1.0mg/kg), morphine (0.25mg/kg), or the KOR agonist, U50,488 (0.01, 0.03, or 0.1mg/kg) in a counter-balanced fashion, immediately prior to a 30-min reunion with their mate. Blood samples were collected immediately prior to and after the reunion. Males receiving morphine approached females less, initiated contact less, and females broke contact with the males less. The increase in cortisol in response to naloxone was greater compared to vehicle, and the increase in cortisol in response to the high dose of U50,488 compared to vehicle approached significance. In Experiment 2, paired males were treated with the KOR antagonist, GNTI (0.1, 0.3, or 1.0mg/kg), or saline 24h prior to a 60-min separation from their mate. Blood samples were collected at the time of injection and immediately before and after separation. Administration of the low dose of GNTI decreased the locomotor component of the separation response compared to vehicle. The present study found that the opioid system is involved in both the affiliative and separation distress components of a pair-bond, and these components are regulated by different opioid receptors.

The pharmacology of medieval sedatives: the "Great Rest" of the Antidotarium Nicolai

ETHNOPHARMACOLOGICAL RELEVANCE

Past practices of compound drugs from different plant ingredients enjoyed remarkable longevity over centuries yet are largely dismissed by modern science as subtherapeutic, lethal or fanciful.

AIM OF THE STUDY

To examine the phytochemical content of a popular medieval opiate drug called the "Great Rest" and gauge the bioavailability and combined effects of its alkaloid compounds (morphine, codeine, hyoscyamine, scopolamine) on the human body according to modern pharmacokinetic and pharmacodynamic parameters established for these compounds.

CALCULATIONS AND THEORY

We reviewed the most recent studies on the pharmacodynamics of morphine, codeine, hyoscyamine and scopolamine to ascertain plasma concentrations required for different physiological effects and applied these findings to dosage of the Great Rest.

RESULTS

Given the proportional quantities of the alkaloid rich plants, we calculate the optimal dose of Great Rest to be 3.1±0.1-5.3±0.76 g and reveal that the lethal dose of Great Rest is double the therapeutic concentration where all three alkaloid compounds are biologically active.

CONCLUSION

This study helps establish the effective dose (ED50), toxic dose (TD50) and lethal dose (LD50) rates for the ingestion of raw opium, henbane and mandrake, and describes their probable combined effects, which may be applied to similar types of pre-modern pharmaceuticals to reveal the empirical logic behind past practices.

The role of the opioid system in alcohol dependence

The role of the brain opioid system in alcohol dependence has been the subject of much research for over 25 years. This review explores the evidence: firstly describing the opioid receptors in terms of their individual subtypes, neuroanatomy, neurophysiology and ligands; secondly, summarising emerging data from specific neurochemical, behavioural and neuroimaging studies, explaining the characteristics of addiction with a focus on alcohol dependence and connecting the opioid system with alcohol dependence; and finally reviewing the known literature regarding opioid antagonists in clinical use for alcohol dependence. Further interrogation of how modulation of the opioid system, via use of MOP (mu), DOP (delta) and KOP (kappa) agents, restores the balance of a dysregulated system in alcohol dependence should increase our insight into this disease process and therefore guide better methods for understanding and treating alcohol dependence in the future.

Anxiolytic medication as an adjunct to morphine analgesia for acute low back pain management in the emergency department: a prospective randomized trial

STUDY DESIGN

Prospective, single-blinded, and randomized clinical trial.

OBJECTIVE

This study evaluates the added benefit of promethazine administration as an anxiolytic adjunct to morphine analgesia in reducing acute low back pain (LBP) compared with morphine alone.

SUMMARY OF BACKGROUND DATA

Acute LBP is one of the most common reasons for emergency department (ED) visits. The optimal analgesic treatment for acute LBP remains controversial. Anxiety relief has been shown to improve pain management in the ED setting. We hypothesized that administration of the antihistamine promethazine as an anxiolytic adjunct to morphine analgesia will improve LBP management compared with morphine alone.

METHODS

Fifty-nine adults, who were treated in our ED for severe acute LBP (visual analogue scale ≥ 70 mm), were randomly enrolled in the study. Thirty patients received slow infusion of intravenous (IV) morphine 0.1 mg/kg in normal saline and 29 patients received an analgesic regimen of IV morphine 0.1 mg/kg with promethazine 25 mg administered similarly. Pain and anxiety levels were subjectively assessed by the patients on a 100-mm visual analogue scale before and after treatment. Adverse event related to analgesia were recorded in real time.

RESULTS

After analgesia administration patients' pain rating decreased by 43 mm in the morphine group and by 39 mm in the morphine/promethazine group (P = 0.26). Similarly, patients' anxiety decreased by 19 mm in the morphine group and by 13 mm in the morphine/promethazine group (P = 0.37). The average ED stay was 78 minutes longer in the morphine/promethazine group (P = 0.01), due to the strong sedative effect of promethazine. Patients' satisfaction and the rate of adverse events were similar in both groups.

CONCLUSION

IV administration of morphine-promethazine regimen for pain and anxiety relief associated with acute LBP showed no advantage compared with IV morphine alone and significantly lengthened the overall ED stay. Thus, we think that promethazine has no place in acute LBP management in the adult ED setting.

LEVEL OF EVIDENCE

1.

Pharmacotherapies for treating opioid use disorder

Opioid use disorder (OUD) is a major public health problem in the United States. It has resulted in devastating consequences for people with this condition, including psychosocial and legal problems, in addition to contraction of infectious diseases such as HIV and hepatitis B and C. Furthermore, this disease can cause fatalities from drug overdoses and drug-drug interactions. OUD shatters families and destroys relationships. Effective treatment is crucial in order to curtail the consequences of this condition. The objective of this article is to provide a review of the pharmacotherapies currently being used to treat OUD.

Naloxone-reversible modulation of pain circuitry by left prefrontal rTMS

A 20-minute session of 10 Hz repetitive transcranial magnetic stimulation (rTMS) of Brodmann Area (BA) nine of the left dorsolateral prefrontal cortex (DLPFC) can produce analgesic effects on postoperative and laboratory-induced pain. This analgesia is blocked by pretreatment with naloxone, a μ-opioid antagonist. The purpose of this sham-controlled, double-blind, crossover study was to identify the neural circuitry that underlies the analgesic effects of left DLPFC rTMS, and to examine how the function of this circuit, including midbrain and medulla, changes during opioid blockade. Fourteen healthy volunteers were randomized to receive intravenous saline or naloxone immediately before sham and real left DLPFC rTMS on the same experimental visit. One week later, each participant received the novel pretreatment but the same stimulation paradigm. Using short sessions of heat on capsaicin-sensitized skin, hot allodynia was assessed during 3 Tesla functional magnetic resonance imaging (fMRI) scanning at baseline, post-sham rTMS, and post-real rTMS. Data were analyzed using whole-brain voxel-based analysis, as well as time series extractions from anatomically-defined regions of interest representing midbrain and medulla. Consistent with previous findings, real rTMS significantly reduced hot allodynia pain ratings. This analgesia was associated with elevated blood oxygenation-level dependent (BOLD) signal in BAs 9 and 10, and diminished BOLD signal in the anterior cingulate, thalamus, midbrain, and medulla during pain. Naloxone pretreatment largely abolished rTMS-induced analgesia, as well as rTMS-induced attenuation of BOLD signal response to painful stimuli throughout pain processing regions, including midbrain and medulla. These preliminary results suggest that left DLPFC rTMS drives top-down opioidergic analgesia.

Reactive microglia after taste nerve injury: comparison to nerve injury models of chronic pain

The chorda tympani (CT), which innervates taste buds on the anterior portion of the tongue, is susceptible to damage during inner ear surgeries. Injury to the CT causes a disappearance of taste buds, which is concurrent with significant microglial responses at central nerve terminals in the nucleus of the solitary tract (nTS). The resulting taste disturbances that can occur may persist for months or years, long after the nerve and taste buds have regenerated. These persistent changes in taste sensation suggest alterations in central functioning and may be related to the microglial responses. This is reminiscent of nerve injuries that result in chronic pain, where microglial reactivity is essential in maintaining the altered sensation (i.e., pain). In these models, methods that diminish microglial responses also diminish the corresponding pain behavior. Although the CT nerve does not contain nociceptive pain fibers, the microglial reactivity after CT damage is similar to that described in pain models. Therefore, methods that decrease microglial responses in pain models were used here to test if they could also affect microglial reactivity after CT injury. Treatment with minocycline, an antibiotic that dampens pain responsive microglia, was largely ineffective in diminishing microglial responses after CT injury. In addition, signaling through the toll-like 4 receptor (TLR4) does not seem to be required after CT injury as blocking or deleting TLR4 had no effect on microglial reactivity. These results suggest that microglial responses following CT injury rely on different signaling mechanisms than those described in nerve injuries resulting in chronic pain.