Lofexidine: A Newly FDA-Approved, Nonopioid Treatment for Opioid Withdrawal

The Mitragyna speciosa (kratom) alkaloid mitragynine: Analysis of adrenergic α2 receptor activity in vitro and in vivo

Mitragynine, an alkaloid present in the leaves of Mitragyna speciosa (kratom), has a complex pharmacology that includes low efficacy agonism at μ-opioid receptors (MORs). This study examined the activity of mitragynine at adrenergic α2 receptors (Aα2Rs) in vitro and in vivo. Mitragynine displaced a radiolabeled Aα2R antagonist ([3H]RX821002) from human Aα2ARs in vitro with lower affinity (Ki = 1260 nM) than the agonists (-)-epinephrine (Ki = 263 nM) or lofexidine (Ki = 7.42 nM). Mitragynine did not significantly stimulate [35S]GTPγS binding at Aα2ARs in vitro, but in rats trained to discriminate 32 mg/kg mitragynine from vehicle (intraperitoneally administered; i.p.), mitragynine exerted an Aα2R agonist-like effect. Both α2R antagonists (atipamezole and yohimbine) and MOR antagonists (naloxone and naltrexone) produced rightward shifts in mitragynine discrimination dose-effect function and Aα2R agonists lofexidine and clonidine produced leftward shifts. In the mitragynine trained rats, Aα2R agonists also produced leftward shifts in discrimination dose-effect functions for morphine and fentanyl. In a separate rat cohort trained to discriminate 3.2 mg/kg i.p. morphine from vehicle, naltrexone produced a rightward shift, but neither an Aα2R agonist or antagonist affected morphine discrimination. In a hypothermia assay, both lofexidine and clonidine produced marked effects antagonized by yohimbine. Mitragynine did not produce hypothermia. Together, these data demonstrate that mitragynine acts in vivo like an Aα2R agonist, although its failure to induce hypothermia or stimulate [35S]GTPγS binding in vitro, suggests that mitragynine maybe a low efficacy Aα2R agonist.

Designing Chromane Derivatives as α2A-Adrenoceptor Selective Agonists via Conformation Constraint

Enhancing the selectivity of alpha2-adrenoceptor (α2A-AR) agonists remains an unresolved issue. Herein, we reported the design of an α2A-AR agonist using the conformation constraint method, beginning with medetomidine. The structure-activity relationship indicated that the 8-substituent of chromane derivatives exerted the most pronounced effect on α2A-AR agonistic activity. Compounds A9 and B9 were identified as the most promising, exhibiting EC50 values of 0.78 and 0.23 nM, respectively. Their selectivity indexes surpassed dexmedetomidine (DMED) by 10-80 fold. In vivo studies demonstrated that both A9 and B9 dose-dependently increased the loss of righting reflex in mice, with ED50 values of 1.54 and 0.138 mg/kg, respectively. Binding mode calculations and mutation studies suggested the indispensability of the hydrogen bond between ASP1283.32 and α2A-AR agonist. In particular, A9 and B9 showed no dual reverse pharmacological effect, a characteristic exhibited by DMED in α2A-AR activation.

Establishing a research agenda for the study and assessment of opioid withdrawal

The opioid crisis is an international public health concern. Treatments for opioid use disorder centre largely on the management of opioid withdrawal, an aversive collection of signs and symptoms that contribute to opioid use disorder. Whereas in the past 50 years more than 90 medications have been developed for depression, only five medications have been developed for opioid use disorder during this period. We posit that underinvestment has occurred in part due to an underdeveloped understanding of opioid withdrawal syndrome. This Personal View summarises substantial gaps in our understanding of opioid withdrawal that are likely to continue to limit major advancements in its treatment. There is no firm consensus in the field as to how withdrawal should be precisely defined; 10-550 symptoms of withdrawal can be measured on 18 scales. The imprecise understanding of withdrawal is likely to result in overestimating or underestimating the severity of an individual's withdrawal syndrome or potential therapeutic effects of different candidate medications. The severity of the opioid crisis is not remitting, and an international research agenda for the study and assessment of opioid withdrawal is necessary to support transformational changes in withdrawal management and treatment of opioid use disorder. Nine actionable targets are delineated here: develop a consensus definition of opioid withdrawal; understand withdrawal symptomatology after exposure to different opioids (particularly fentanyl); understand precipitated opioid withdrawal; understand how co-exposure of other drugs (eg, xylazine and stimulants) influences withdrawal expression; examine individual variation in withdrawal phenotypes; precisely characterise the protracted withdrawal syndrome; identify biomarkers of opioid withdrawal severity; identify predictors of opioid withdrawal severity; and understand which symptoms are most closely associated with treatment attrition or relapse. The US Food and Drug Administration recently established a formal indication for opioid withdrawal that has invigorated interest in drug development for opioid withdrawal management. Action is now needed to support these interests and help industry identify new classes of medications so that real change can be achieved for people with opioid use disorder.

Alcohol Use Disorder Treatment: Problems and Solutions

Alcohol use disorder (AUD) afflicts over 29 million individuals and causes more than 140,000 deaths annually in the United States. A heuristic framework for AUD includes a three-stage cycle-binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation-that provides a starting point for exploring the heterogeneity of AUD with regard to treatment. Effective behavioral health treatments and US Food and Drug Administration-approved medications are available but greatly underutilized, creating a major treatment gap. This review outlines challenges that face the alcohol field in closing this treatment gap and offers solutions, including broadening end points for the approval of medications for the treatment of AUD; increasing the uptake of screening, brief intervention, and referral to treatment; addressing stigma; implementing a heuristic definition of recovery; engaging early treatment; and educating health-care professionals and the public about challenges that are associated with alcohol misuse. Additionally, this review focuses on broadening potential targets for the development of medications for AUD by utilizing the three-stage heuristic model of addiction that outlines domains of dysfunction in AUD and the mediating neurobiology of AUD.

Low dose lofexidine for medically directed outpatient opioid tapering in adults with chronic pain: a prospective case series

BACKGROUND

In adults with chronic pain, mild-to-moderate withdrawal symptoms during medically directed opioid tapering in the outpatient setting may not be accompanied by hypertension or tachycardia. This clinical scenario could limit the use of lofexidine at dosages reported in clinical trials of opioid withdrawal precipitated by abrupt opioid discontinuation. Thus, the primary aim of this prospective case series is to describe the use of low dose lofexidine for opioid withdrawal in patients with chronic pain undergoing medically directed opioid tapering in an outpatient setting.

METHODS

Six patients (white 5, Latino 1) admitted to an outpatient interdisciplinary pain rehabilitation program met inclusion and exclusion criteria. Patients self-selected to undergo medically directed opioid tapering, and the medication the patients were prescribed upon admission was used in the taper schedule. Upon initiation of the opioid taper, patients received 0.18 mg of lofexidine every 6 hours.

RESULTS

Five of the six patients were women, and the median morphine milligram equivalents at baseline were 36.9. The median taper duration was 15 days, and the median duration of lofexidine administration was 14 days. Withdrawal scores were mild throughout the taper in four patients, and two patients with fibromyalgia experienced single episodes of moderately severe withdrawal symptoms at the median morphine milligram equivalent midpoint of the taper. No hypotension or sustained bradycardia were observed, and no adverse effects related to lofexidine were reported.

CONCLUSION

The observations from this prospective case series suggest that low-dose lofexidine may be a feasible adjunct medication to attenuate withdrawal symptoms in adults with chronic pain undergoing outpatient opioid tapering.

IUPHAR review: Recent progress in the development of Mu opioid receptor modulators to treat opioid use disorders

Opioid Use Disorder (OUD) can be described as intense preoccupation with using or obtaining opioids despite the negative consequences associated with their use. As the number of OUD cases in the U.S. increase, so do the number of opioid-related overdose deaths. In 2022, opioid-related overdose became the No. 1 cause of death for individuals in the U.S. between the ages of 25 and 64 years of age. Because of the introduction of highly potent synthetic opioids (e.g. fentanyl) to the illicit drug market, there is an urgent need for therapeutics that successfully reduce the number of overdoses and can help OUD patients maintain sobriety. Most abused opioids stimulate the mu-opioid receptor (MOR) and activation of this receptor can lead to positive (e.g., euphoria) consequences. However, the negative side effects of MOR stimulation can be fatal (e.g., sedation, respiratory depression). Therefore, the MOR is an attractive target for developing medications to treat OUD. Current FDA drugs include MOR agonists that aid in detoxification and relapse prevention, and MOR antagonists that also serve as maintenance therapies or reverse overdose. These medications are limited by their abuse potential, adverse effects, or pharmacological profiles which leaves ample room for research into designing new chemical entities with optimal physiological effects. These includes, orthosteric ligands that target the primary binding site of the MOR, allosteric ligands that positively, negatively, or "silently" modulate receptor function, and lastly, bitopic ligands target both the orthosteric and allosteric sites simultaneously.

Forward or Backward: Lessons Learned from Small Molecule Drugs Approved by FDA from 2012 to 2022

At every juncture in history, the design and identification of new drugs pose significant challenges. To gain valuable insights for future drug development, we conducted a detailed analysis of New Molecular Entitiy (NME) approved by the Food and Drug Administration (FDA) from 2012 to 2022 and focused on the analysis of first-in-class (FIC) small-molecules from a perspective of a medicinal chemist. We compared the change of numbers between all the FDA-approved NMEs and FIC, which could be more visual to analyze the changing trend of FIC. To get a more visual change of molecular physical properties, we computed the annual average trends in molecular weight for FIC across various therapeutic fields. Furthermore, we consolidated essential information into three comprehensive databases, which covered the indications, canonical SMILES, structural formula, research and development (R&D) institutions, molecular weight, calculated LogP (CLogP), and route of administration on all the small-molecule pharmaceutical. Through the analysis of the database of 11 years of approvals, we forecast the development trend of NME approval in the future.

All Hands on Deck: We Need Multiple Approaches To Uncover the Neuroscience behind the Opioid Overdose Crisis

Opioid use disorder (OUD) affects millions of people throughout the United States, yet there are only three Food and Drug Administration-approved pharmacological treatments. Though these treatments have been shown to be effective, the number of overdose deaths continues to rise. The increase of fentanyl, fentanyl analogs, and adulterants in the illicit drug supply has further complicated treatment strategies. Preclinical researchers strive to model OUD to better understand this complicated disorder, and this research is a critical enabler for the development of novel treatments. As a result, there are many different preclinical models of OUD. Often, researchers form strong opinions on what they believe to be the "best" model to mimic the human condition. Here, we argue that researchers should be supportive of multiple models to promote new perspectives and discoveries and always consider the trends in human opioid use when designing preclinical studies. We describe the benefits of contingent and noncontingent models as well as models of opioid withdrawal and how each of these can help illuminate different components of OUD.

Conformationally Selective 2-Aminotetralin Ligands Targeting the alpha2A- and alpha2C-Adrenergic Receptors

Many important physiological processes are mediated by alpha2A- and alpha2C-adrenergic receptors (α2Rs), a subtype of class A G protein-coupled receptors (GPCRs). However, α2R signaling is poorly understood, and there are few approved medications targeting these receptors. Drug discovery aimed at α2Rs is complicated by the high degree of binding pocket homology between α2AR and α2CR, which confounds ligand-mediated selective activation or inactivation of signaling associated with a particular subtype. Meanwhile, α2R signaling is complex and it is reported that activating α2AR is beneficial in many clinical contexts, while activating α2CR signaling may be detrimental to these positive effects. Here, we report on a novel 5-substituted-2-aminotetralin (5-SAT) chemotype that, depending on substitution, has diverse pharmacological activities at α2Rs. Certain lead 5-SAT analogues act as partial agonists at α2ARs, while functioning as inverse agonists at α2CRs, a novel pharmacological profile. Leads demonstrate high potency (e.g., EC50 < 2 nM) at the α2AR and α2CRs regarding Gαi-mediated inhibition of adenylyl cyclase and production of cyclic adenosine monophosphate (cAMP). To help understand the molecular basis of 5-SAT α2R multifaceted functional activity, α2AR and α2CR molecular models were built from the crystal structures and 1 μs molecular dynamics (MD) simulations and molecular docking experiments were performed for a lead 5-SAT with α2AR agonist and α2CR inverse agonist activity, i.e., (2S)-5-(2'-fluorophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (FPT), in comparison to the FDA-approved (for opioid withdrawal symptoms) α2AR/α2CR agonist lofexidine. Results reveal several interactions between FPT and α2AR and α2CR amino acids that may impact the functional activity. The computational data in conjunction with experimental in vitro affinity and function results provide information to understand ligand stabilization of functionally distinct GPCR conformations regarding α2AR and α2CRs.

Norepinephrine system at the interface of attention and reward

Reward learning is key to survival for individuals. Attention plays an important role in the rapid recognition of reward cues and establishment of reward memories. Reward history reciprocally guides attention to reward stimuli. However, the neurological processes of the interplay between reward and attention remain largely elusive, due to the diversity of the neural substrates that participate in these two processes. In this review, we delineate the complex and differentiated locus coeruleus norepinephrine (LC-NE) system in relation to different behavioral and cognitive substrates of reward and attention. The LC receives reward related sensory, perceptual, and visceral inputs, releases NE, glutamate, dopamine and various neuropeptides, forms reward memories, drives attentional bias and selects behavioral strategies for reward. Preclinical and clinical studies have found that abnormalities in the LC-NE system are involved in a variety of psychiatric conditions marked by disturbed functions in reward and attention. Therefore, we propose that the LC-NE system is an important hub in the interplay between reward and attention as well as a critical therapeutic target for psychiatric disorders characterized by compromised functions in reward and attention.

Paraventricular Nucleus of the Hypothalamus Oxytocin and Incubation of Heroin Seeking

INTRODUCTION

There are numerous pharmacologic treatments for opioid use disorder (OUD), but none that directly target the underlying addictive effects of opioids. Oxytocin, a peptide hormone produced in the paraventricular nucleus (PVN) of the hypothalamus, has been investigated as a potential therapeutic for OUD. Promising preclinical and clinical results have been reported, but the brain region(s) and mechanism(s) by which oxytocin impacts reward processes remain undetermined.

METHODS

Here, we assess peripherally administered oxytocin's impacts on cued reinstatement of heroin seeking following forced abstinence and its effects on neuronal activation in the PVN and key projection regions. We also examine how designer receptors exclusively activated by designer drug (DREADD)-mediated activation or inhibition of oxytocinergic PVN neurons alters cued heroin seeking and social interaction.

RESULTS

As predicted, peripheral oxytocin administration successfully decreased cued heroin seeking on days 1 and 30 of abstinence. Oxytocin administration also led to increased neuronal activity within the PVN and the central amygdala (CeA). Activation of oxytocinergic PVN neurons with an excitatory (Gq) DREADD did not impact cued reinstatement or social interaction. In contrast, suppression with an inhibitory (Gi) DREADD reduced heroin seeking on abstinence day 30 and decreased time spent interacting with a novel conspecific.

DISCUSSION

These findings reinforce oxytocin's therapeutic potential for OUD, the basis for which may be driven in part by increased PVN-CeA circuit activity. Our results also suggest that oxytocin has distinct signaling and/or other mechanisms of action to produce these effects, as inhibition, but not activation, of oxytocinergic PVN neurons did not recapitulate the suppression in heroin seeking.

Sublingual dexmedetomidine (BXCL501) reduces opioid withdrawal symptoms: findings from a multi-site, phase 1b/2, randomized, double-blind, placebo-controlled trial

Background: Like other alpha-2-adrenergic receptor agonists, dexmedetomidine may reduce the severity of opioid withdrawal but with fewer adverse cardiovascular effects.Objective: This study assessed the safety of sublingual dexmedetomidine (BXCL501) and its preliminary efficacy in treating opioid withdrawal (ClinicalTrials.gov: NCT04470050).Methods: Withdrawal was induced among individuals with physiological dependence on opioids via discontinuation of oral morphine (Days 1-5). Participants were randomized to receive placebo or active BXCL501: 30, 60, 90, 120, 180, and 240 μg twice daily (Days 6-12). Treatment-emergent adverse events (TEAEs) were the primary outcome measure. Secondary outcomes included the Clinical and Subjective Opiate Withdrawal Scales (COWS and SOWS-Gossop, respectively), and the Agitation and Calmness Evaluation Scale (ACES).Results: Of 225 participants enrolled, 90 discontinued during morphine stabilization. Post-BXCL501 randomization (Day 6) data were available from 135 participants (73% male), with 33% completing thru Day 12. In total, 36 subjects reported 1 or more TEAE. Higher doses of BXCL501 (i.e. 180 and 240 µg, twice daily) increased the frequency of: hypotension, orthostatic hypotension, and somnolence. TEAEs related to BXCL501 were mild or moderate in severity, except for one participant in the 120 µg condition whose orthostatic hypotension and bradycardia were classified as severe. Higher BXCL501 dose conditions (120, 180, and 240 µg) resulted in statistically significant reductions in COWS & SOWS scores. Mean ratings on the ACES were between 3 (mild), 4 (normal), and 5 (mild calmness), with few significant differences as a function of dose.Conclusions: These findings support the continued development of BXCL501 for the management of opioid withdrawal.

Adjunctive Management of Opioid Withdrawal with the Nonopioid Medication Cannabidiol

Introduction: Opioid use disorder (OUD) is a major public health crisis worldwide. Patients with OUD inevitably experience withdrawal symptoms when they attempt to taper down on their current opioid use, abstain completely from opioids, or attempt to transition to certain medications for opioid use disorder. Acute opioid withdrawal can be debilitating and include a range of symptoms such as anxiety, pain, insomnia, and gastrointestinal symptoms. Whereas acute opioid withdrawal only lasts for 1-2 weeks, protracted withdrawal symptoms can persist for months after the cessation of opioids. Insufficient management of opioid withdrawal often leads to devastating results including treatment failure, relapse, and overdose. Thus, there is a critical need for cost-effective, nonopioid medications, with minimal side effects to help in the medical management of opioid withdrawal syndrome. We discuss the potential consideration of cannabidiol (CBD), a nonintoxicating component of the cannabis plant, as an adjunctive treatment in managing the opioid withdrawal syndrome. Materials and Methods: A review of the literature was performed using keywords related to CBD and opioid withdrawal syndrome in PubMed and Google Scholar. A total of 144 abstracts were identified, and 41 articles were selected where CBD had been evaluated in clinical studies relevant to opioid withdrawal. Results: CBD has been reported to have several therapeutic properties including anxiolytic, antidepressant, anti-inflammatory, anti-emetic, analgesic, as well as reduction of cue-induced craving for opioids, all of which are highly relevant to opioid withdrawal syndrome. In addition, CBD has been shown in several clinical trials to be a well-tolerated with no significant adverse effects, even when co-administered with a potent opioid agonist. Conclusions: Growing evidence suggests that CBD could potentially be added to the standard opioid detoxification regimen to mitigate acute or protracted opioid withdrawal-related symptoms. However, most existing findings are either based on preclinical studies and/or small clinical trials. Well-designed, prospective, randomized-controlled studies evaluating the effect of CBD on managing opioid withdrawal symptoms are warranted.

Using Named Entity Recognition to Identify Substances Used in the Self-medication of Opioid Withdrawal: Natural Language Processing Study of Reddit Data

BACKGROUND

The cessation of opioid use can cause withdrawal symptoms. People often continue opioid misuse to avoid these symptoms. Many people who use opioids self-treat withdrawal symptoms with a range of substances. Little is known about the substances that people use or their effects.

OBJECTIVE

The aim of this study is to validate a methodology for identifying the substances used to treat symptoms of opioid withdrawal by a community of people who use opioids on the social media site Reddit.

METHODS

We developed a named entity recognition model to extract substances and effects from nearly 4 million comments from the r/opiates and r/OpiatesRecovery subreddits. To identify effects that are symptoms of opioid withdrawal and substances that are potential remedies for these symptoms, we deduplicated substances and effects by using clustering and manual review, then built a network of substance and effect co-occurrence. For each of the 16 effects identified as symptoms of opioid withdrawal in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, we identified the 10 most strongly associated substances. We classified these pairs as follows: substance is a Food and Drug Administration-approved or commonly used treatment for the symptom, substance is not often used to treat the symptom but could be potentially useful given its pharmacological profile, substance is a home or natural remedy for the symptom, substance can cause the symptom, or other or unclear. We developed the Withdrawal Remedy Explorer application to facilitate the further exploration of the data.

RESULTS

Our named entity recognition model achieved F1 scores of 92.1 (substances) and 81.7 (effects) on hold-out data. We identified 458 unique substances and 235 unique effects. Of the 130 potential remedies strongly associated with withdrawal symptoms, 54 (41.5%) were Food and Drug Administration-approved or commonly used treatments for the symptom, 17 (13.1%) were not often used to treat the symptom but could be potentially useful given their pharmacological profile, 13 (10%) were natural or home remedies, 7 (5.4%) were causes of the symptom, and 39 (30%) were other or unclear. We identified both potentially promising remedies (eg, gabapentin for body aches) and potentially common but harmful remedies (eg, antihistamines for restless leg syndrome).

CONCLUSIONS

Many of the withdrawal remedies discussed by Reddit users are either clinically proven or potentially useful. These results suggest that this methodology is a valid way to study the self-treatment behavior of a web-based community of people who use opioids. Our Withdrawal Remedy Explorer application provides a platform for using these data for pharmacovigilance, the identification of new treatments, and the better understanding of the needs of people undergoing opioid withdrawal. Furthermore, this approach could be applied to many other disease states for which people self-manage their symptoms and discuss their experiences on the web.

Cannabinoids in the Treatment of Cannabis Use Disorder: Systematic Review of Randomized Controlled Trials

BACKGROUND

The prevalence of cannabis use and cannabis use disorders (CUD) has significantly increased over time. However, there are no approved pharmacological treatments for CUD. The aim of this study was to determine the efficacy and safety of various medical cannabinoids in the treatment of CUD.

METHODS

We conducted a systematic review of randomized controlled trials which evaluated the therapeutic potential of medical cannabinoids in individuals with CUD and summarized the main study outcomes in terms of cannabis use, abstinence, withdrawal symptoms, craving, retention in treatment and adverse events.

RESULTS

We identified eight trials with a total of 667 study participants. Dronabinol reduced cannabis withdrawal symptoms whereas nabiximols, cannabidiol and PF-04457845, a fatty acid amide inhibitor, also reduced cannabis use and improved abstinence, compared to placebo. Nabilone failed to demonstrate efficacy in the treatment of CUD. All medications were well-tolerated.

CONCLUSIONS

Cannabinoid receptor agonists, i.e., dronabinol and nabilone, showed only limited or no therapeutic potential in the treatment of CUD. In contrast, modulators of endocannabinoid activity, i.e., nabiximols, cannabidiol and PF-04457845, demonstrated broader efficacy which covered almost all aspects of CUD. Endocannabinoid modulation appears to be a promising treatment approach in CUD, but the evidence to support this strategy is still small and future research in this direction is needed.

Neurocircuitry basis of the opioid use disorder-post-traumatic stress disorder comorbid state: conceptual analyses using a dimensional framework

Understanding the interface between opioid use disorder (OUD) and post-traumatic stress disorder (PTSD) is challenging. By use of a dimensional framework, such as research domain criteria, convergent and targetable neurobiological processes in OUD-PTSD comorbidity can be identified. We hypothesise that, in OUD-PTSD, circuitry that is implicated in two research domain criteria systems (ie, negative valence and cognitive control) underpins dysregulation of incentive salience, negative emotionality, and executive function. We also propose that the OUD-PTSD state might be systematically investigated with approaches outlined within a neuroclinical assessment framework for addictions and PTSD. Our dimensional analysis of the OUD-PTSD state shows how first-line therapeutic approaches (ie, partial μ-type opioid receptor [MOR1] agonism) modulate overlapping neurobiological and clinical features and also provides mechanistic rationale for evaluating polytherapeutic strategies (ie, partial MOR1 agonism, κ-type opioid receptor [KOR1] antagonism, and α-2A adrenergic receptor [ADRA2A] agonism). A combination of these therapeutic mechanisms is projected to facilitate recovery in patients with OUD-PTSD by mitigating negative valence states and enhancing executive control.

Kratom Alkaloids, Natural and Semi-Synthetic, Show Less Physical Dependence and Ameliorate Opioid Withdrawal

Chronic administration of opioids produces physical dependence and opioid-induced hyperalgesia. Users claim the Thai traditional tea "kratom" and component alkaloid mitragynine ameliorate opioid withdrawal without increased sensitivity to pain. Testing these claims, we assessed the combined kratom alkaloid extract (KAE) and two individual alkaloids, mitragynine (MG) and the analog mitragynine pseudoindoxyl (MP), evaluating their ability to produce physical dependence and induce hyperalgesia after chronic administration, and as treatments for withdrawal in morphine-dependent subjects. C57BL/6J mice (n = 10/drug) were administered repeated saline, or graded, escalating doses of morphine (intraperitoneal; i.p.), kratom alkaloid extract (orally, p.o.), mitragynine (p.o.), or MP (subcutaneously, s.c.) for 5 days. Mice treated chronically with morphine, KAE, or mitragynine demonstrated significant drug-induced hyperalgesia by day 5 in a 48 °C warm-water tail-withdrawal test. Mice were then administered naloxone (10 mg/kg, s.c.) and tested for opioid withdrawal signs. Kratom alkaloid extract and the two individual alkaloids demonstrated significantly fewer naloxone-precipitated withdrawal signs than morphine-treated mice. Additional C57BL/6J mice made physically dependent on morphine were then used to test the therapeutic potential of combined KAE, mitragynine, or MP given twice daily over the next 3 days at either a fixed dose or in graded, tapering descending doses. When administered naloxone, mice treated with KAE, mitragynine, or MP under either regimen demonstrated significantly fewer signs of precipitated withdrawal than control mice that continued to receive morphine. In conclusion, while retaining some liabilities, kratom, mitragynine, and mitragynine pseudoindoxyl produced significantly less physical dependence and ameliorated precipitated withdrawal in morphine-dependent animals, suggesting some clinical value.

Improving Translational Research Outcomes for Opioid Use Disorder Treatments

Purpose of Review

Pharmacotherapies are the most effective means of reducing the harms associated with opioid use disorder (OUD). Translational research seeking to develop novel medications to treat OUD has been challenging due to the complex etiology of addiction. Preclinical outcome measures are often behavioral, and it is difficult, if not impossible, to fully mirror the various emotional and cognitive processes that motivate opioid use in humans. The goal of the current narrative review was to summarize the translational progression of three potential medications for OUD, which had varying levels of success.

Recent Findings

Memantine, lorcaserin, and lofexidine all showed promise in preclinical studies; however, only lofexidine was able to consistently replicate these findings in human subjects, and receive FDA approval. It was the authors' objective to use this review to identify areas of needed improvement in translational research for OUD.

Summary

Preclinical studies vary significantly in their ability to forecast effectiveness in clinical trials. Among the various preclinical models, suppression of opioid self-administration appears to have the best predictive validity. As they model a mostly physiological phenomenon, preclinical assessments of opioid withdrawal also appear to have high predictive validity. In our review of the literature, the authors noted numerous examples of clinical trials that were underpowered, lack precision, and proper outcomes. Better-validated preclinical targets and improved design of proof-of-concept human studies should allow investigators to more efficiently develop and test medications for OUD.

A Decade of FDA-Approved Drugs (2010-2019): Trends and Future Directions

A total of 378 novel drugs and 27 biosimilars approved by the U.S. Food and Drug Administration (FDA) between 2010 and 2019 were evaluated according to approval numbers by year, therapeutic areas, modalities, route of administration, first-in-class designation, approval times, and expedited review categories. From this review, oncology remains the top therapy area (25%), followed by infection (15%) and central nervous system disorders (11%). Regulatory incentives have been effective as evidenced by an increase in orphan drugs as well as antibacterial drugs approved under the GAIN act. Clinical development times may be increasing, perhaps as a result of the increase in orphan drug indications. Small molecules continue to mostly adhere to "Rule of 5" (Ro5) parameters, but innovation in new modalities is rapidly progressing with approvals for antisense oligonucleotides (ASO), small-interfering RNA (siRNAs), and antibody-directed conjugates (ADCs). Finally, novel targets and scientific breakthroughs that address areas of unmet clinical need are discussed in detail.

Lofexidine for acute opioid withdrawal: A clinical case series

Introduction

Maintaining abstinence through the opioid withdrawal period is a substantial barrier to treatment for patients with opioid use disorder. The alpha-2 agonist lofexidine has demonstrated efficacy and safety in clinical trials, but pragmatic studies describing its use in clinical practice are lacking. This case series describes the use of lofexidine for opioid withdrawal symptoms in an inpatient addiction treatment facility.

Methods

Seventeen patients receiving at least 1 dose of lofexidine during inpatient treatment for opioid withdrawal were included in this study. A retrospective chart review was conducted for clinical, subjective, and objective data. Adverse events, total daily dose, clinical opioid withdrawal scale (COWS) scores, vital signs, and reasons for early discontinuation of lofexidine are reported.

Results

Patients treated with lofexidine experienced mild withdrawal symptoms throughout treatment. Most patients (65%) experienced a decrease in their average daily COWS scores from intake to discharge. Two patients (12%) left treatment against medical advice, and 5 patients (29%) discontinued treatment prior to day 7 due to resolution of symptoms. Average daily blood pressure readings remained stable, and daily average heart rate decreased over time.

Discussion

Lofexidine can be successfully incorporated into a conventional withdrawal management protocol. The cost of lofexidine and its recent introduction to the market remain barriers to accessibility in the United States. Studies evaluating patient-reported outcomes as well as direct comparisons with other alpha-2 agonists are needed to inform optimal clinical use of lofexidine.

New directions in the treatment of opioid withdrawal

The treatment of opioid withdrawal is an important area of clinical concern when treating patients with chronic, non-cancer pain, patients with active opioid use disorder, and patients receiving medication for opioid use disorder. Current standards of care for medically supervised withdrawal include treatment with μ-opioid receptor agonists, (eg, methadone), partial agonists (eg, buprenorphine), and α2-adrenergic receptor agonists (eg, clonidine and lofexidine). Newer agents likewise exploit these pharmacological mechanisms, including tramadol (μ-opioid receptor agonism) and tizanidine (α2 agonism). Areas for future research include managing withdrawal in the context of stabilising patients with opioid use disorder to extended-release naltrexone, transitioning patients with opioid use disorder from methadone to buprenorphine, and tapering opioids in patients with chronic, non-cancer pain.

Opioid withdrawal symptoms, frequency, and pain characteristics as correlates of health risk among people who inject drugs

OBJECTIVE

Opioid withdrawal symptoms are widely understood to contribute to health risk but have rarely been measured in community samples of opioid using people who inject drugs (PWID).

METHODS

Using targeted sampling methods, 814 PWID who reported regular opioid use (at least 12 uses in the last 30 days) were recruited and interviewed about demographics, drug use, health risk, and withdrawal symptoms, frequency, and pain. Multivariable regression models were developed to examine factors associated with any opioid withdrawal, withdrawal frequency, pain severity, and two important health risks (receptive syringe sharing and non-fatal overdose).

RESULTS

Opioid withdrawal symptoms were reported by 85 % of participants in the last 6 months, with 29 % reporting at least monthly withdrawal symptoms and 35 % reporting at least weekly withdrawal symptoms. Very or extremely painful symptoms were reported by 57 %. In separate models, we found any opioid withdrawal (adjusted odds ratio [AOR] = 2.75, 95 % confidence interval [CI] = 1.52, 5.00) and weekly or more opioid withdrawal frequency (AOR = 1.94; 95 % CI = 1.26, 3.00) (as compared to less than monthly) to be independently associated with receptive syringe sharing while controlling for confounders. Any opioid withdrawal (AOR = 1.71; 95 % CI = 1.04, 2.81) was independently associated with nonfatal overdose while controlling for confounders. In a separate model, weekly or more withdrawal frequency (AOR = 1.69; 95 % CI = 1.12, 2.55) and extreme or very painful withdrawal symptoms (AOR = 1.53; 95 % CI = 1.08, 2.16) were associated with nonfatal overdose as well.

CONCLUSIONS

Withdrawal symptoms among PWID increase health risk. Treatment of withdrawal symptoms is urgently needed and should include buprenorphine dispensing.

R-(-)-ketamine modifies behavioral effects of morphine predicting efficacy as a novel therapy for opioid use disorder1

Substance abuse disorder continues to have devastating consequences for individuals and society and current therapies are not sufficient to provide the magnitude of medical impact required. Although some evidence suggests the use of ketamine in treating various substance use related- symptoms, its adverse event profile including dissociation, dysphoria, and abuse liability limit its potential as a therapy. Here, we outline experiments to test our hypothesis that (R)-ketamine can both alleviate withdrawal symptoms and produce effects that help sustain abstinence. In morphine-dependent rats, (R)-ketamine alleviated naloxone-precipitated withdrawal signs. (R)-ketamine also blocked morphine-induced place preference in mice without inducing place preference on its own. We also evaluated whether (R)-ketamine would induce anhedonia, a counter-indicated effect for a drug abuse treatment agent. S-(+)- but not R-(-)-ketamine produced anhedonia-like responses in rats that electrically self-stimulated the medial forebrain bundle (ICSS). However, time-course studies of ICSS are needed to fully appreciate these differences. These data begin to support the claim that (R)-ketamine will dampen withdrawal symptoms and drug liking, factors known to contribute to the cycle of drug addiction. In addition, these data suggest that (R)-ketamine would not produce negative mood or anhedonia that could interfere with treatment. It is suggested that continued investigation of (R)-ketamine as a novel therapeutic for substance abuse disorder be given consideration by the preclinical and clinical research communities. This suggestion is further encouraged by a recent report on the efficacy of (R)-ketamine in treatment-resistant depressed patients at a dose with little measurable dissociative side-effects.

The rising crisis of illicit fentanyl use, overdose, and potential therapeutic strategies

Fentanyl is a powerful opioid anesthetic and analgesic, the use of which has caused an increasing public health threat in the United States and elsewhere. Fentanyl was initially approved and used for the treatment of moderate to severe pain, especially cancer pain. However, recent years have seen a growing concern that fentanyl and its analogs are widely synthesized in laboratories and adulterated with illicit supplies of heroin, cocaine, methamphetamine, and counterfeit pills, contributing to the exponential growth in the number of drug-related overdose deaths. This review summarizes the recent epidemic and evolution of illicit fentanyl use, its pharmacological mechanisms and side effects, and the potential clinical management and prevention of fentanyl-related overdoses. Because social, economic, and health problems that are related to the use of fentanyl and its analogs are growing, there is an urgent need to implement large-scale safe and effective harm reduction strategies to prevent fentanyl-related overdoses.