Treatment of cocaine craving with as-needed nalmefene, a partial κ opioid receptor agonist: first clinical experience

Nalmefene Hydrochloride: Potential Implications for Treating Alcohol and Opioid Use Disorder

Nalmefene hydrochloride was first discovered as an opioid antagonist derivative of naltrexone in 1975. It is among the most potent opioid antagonists currently on the market and is differentiated from naloxone and naltrexone by its partial agonist activity at the kappa-opioid receptor which may benefit in the treatment of alcohol use disorder. Oral nalmefene has been approved in the European Union for treatment of alcohol use disorder since 2013. As of 2023, nalmefene is available in the United States as an intranasal spray for reversal of opioid overdose but is not approved for alcohol or opioid use disorder as a maintenance treatment. The substantially longer half-life of nalmefene and 5-fold higher binding affinity to opioid receptors makes it a superior agent over naloxone in the reversal of high potency synthetic opioids like fentanyl and the emerging nitazenes. Nalmefene presents with a comparable side effect profile to other opioid antagonists and should be considered for further development as a maintenance treatment for opioid and other substance use disorders.

Deep Brain Stimulation Compared With Contingency Management for the Treatment of Cocaine Use Disorders: A Threshold and Cost-Effectiveness Analysis

OBJECTIVES

Cocaine is the second most frequently used illicit drug worldwide (after cannabis), and cocaine use disorder (CUD) related deaths increased globally by 80% from 1990 to 2013. There is yet to be a regulatory-approved treatment. Emerging preclinical evidence indicates that deep brain stimulation (DBS) of the nucleus accumbens may be a therapeutic option. Prior to expanding the costly investigation of DBS for treatment of CUD, it is important to ensure societal cost-effectiveness.

AIMS

We conducted a threshold and cost-effectiveness analysis to determine the success rate at which DBS would be equivalent to contingency management (CM), recently identified as the most efficacious therapy for treatments of CUDs.

MATERIALS AND METHODS

Quality of life, efficacy, and safety parameters for CM were obtained from previous literature. Costs were calculated from a societal perspective. Our model predicted the utility benefit based on quality-adjusted-life-years (QALYs) and incremental-cost-effectiveness-ratio resulting from two treatments on a one-, two-, and five-year timeline.

RESULTS

On a one-year timeline, DBS would need to impart a success rate (i.e., cocaine free) of 70% for it to yield the same utility benefit (0.492 QALYs per year) as CM. At no success rate would DBS be more cost-effective (incremental-cost-effectiveness-ratio <$50,000) than CM during the first year. Nevertheless, as DBS costs are front-loaded, DBS would need to achieve success rates of 74% and 51% for its cost-effectiveness to exceed that of CM over a two- and five-year period, respectively.

CONCLUSIONS

We find DBS would not be cost-effective in the short-term (one year) but may be cost-effective in longer timelines. Since DBS holds promise to potentially be a cost-effective treatment for CUDs, future randomized controlled trials should be performed to assess its efficacy.

Nalmefene, a mu opioid receptor antagonist/kappa opioid receptor partial agonist, potentiates cocaine motivation but not intake with extended access self-administration in adult male mice

The mu opioid receptor antagonist/kappa opioid receptor (KOR) partial agonist nalmefene (NMF), a close structural analog of naltrexone (NTX), has been shown to reduce cocaine reward in preclinical models. Given the greater KOR potency and improved bioavailability compared to NTX, NMF may be a promising pharmacotherapeutic for cocaine use disorder (CUD). Here we examine the effects of NMF pretreatment on chronic daily extended access (4h) cocaine intravenous self-administration (IVSA) in adult male C57Bl/6J mice.

METHODS

separate groups of mice had daily 4h cocaine IVSA sessions (0.25 or 0.5 mg/kg/inf, FR1) for 14 days. Starting on day 8, mice were pretreated with NMF (0, 1, or 10 mg/kg) 30m before each session. A separate group of mice acquired cocaine IVSA [seven days FR1 then four FR3 of 4h daily sessions (0.5 mg/kg/inf)] prior to a single progressive ratio 3 session to examine the effect of 1 mg/kg NMF on cocaine motivation.

RESULTS

No significant effect of NMF pretreatment on cocaine intake was observed. Acute pretreatment of 1 mg/kg NMF significantly potentiated cocaine motivation as measured by progressive ratio breakpoint.

CONCLUSIONS

NMF did not significantly attenuate cocaine intake and increased motivation for cocaine suggesting that NMF may not be suitable for non-abstinent CUD patients. Further research is needed with KOR selective partial or full agonists to determine their effect on cocaine reinforcement.

Determination of structural factors affecting binding to mu, kappa and delta opioid receptors

Addiction is a complex behavioral phenomenon in which naturally occurring or synthetic chemicals modulate the response of the reward system through their binding to a variety of neuroreceptors, resulting in compulsive substance-seeking and use despite harmful consequences to the individual. Among these, the opioid receptor (OR) family and more specifically, the mu-opioid receptor (MOR) subtype plays a critical role in the addiction to powerful prescription and illicit drugs such as hydrocodone, oxycodone, fentanyl, cocaine, and methamphetamine (Contet et al. in Curr Opin Neurobiol 14(3):370-378, 2004). Conversely, agonists binding to kappa (KOR) and antagonists binding to delta opioid receptors (DOR) have been reported to induce negative reinforcing effects. As more than 700 new psychoactive substances were illegally sold between 2009 and 2016 (DEA-DCT-DIR-032-18), most of them lacking basic toxicological and pharmacological profiles, molecular modeling approaches that could quickly and reliably fill the gaps in our knowledge would be highly desirable tools for determining the effects of these synthetics. Here, we report accurate 3D-spectrometric data-activity relationship classification models for large and diverse datasets of MOR, KOR and DOR binders with areas under the receiver operating characteristic curve for the "blind" prediction sets exceeding 0.88. Structural features associated with (selective) binding to MOR, KOR and/or DOR were identified. These models could assist regulatory agencies in evaluating the health risks associated with the use of unprofiled substances as well as to help the pharmaceutical industry in its search for new drugs to combat addiction.

Cutting-Edge Search for Safer Opioid Pain Relief: Retrospective Review of Salvinorin A and Its Analogs

Over the years, pain has contributed to low life quality, poor health, and economic loss. Opioids are very effective analgesic drugs for treating mild, moderate, or severe pain. Therapeutic application of opioids has been limited by short and long-term side effects. These side effects and opioid-overuse crisis has intensified interest in the search for new molecular targets and drugs. The present review focuses on salvinorin A and its analogs with the aim of exploring their structural and pharmacological profiles as clues for the development of safer analgesics. Ethnopharmacological reports and growing preclinical data have demonstrated the antinociceptive effect of salvinorin A and some of its analogs. The pharmacology of analogs modified at C-2 dominates the literature when compared to the ones from other positions. The distinctive binding affinity of these analogs seems to correlate with their chemical structure and in vivo antinociceptive effects. The high susceptibility of salvinorin A to chemical modification makes it an important pharmacological tool for cellular probing and developing analogs with promising analgesic effects. Additional research is still needed to draw reliable conclusions on the therapeutic potential of salvinorin A and its analogs.

Opioid Antagonists for Pharmacological Treatment of Gambling Disorder: Are they Relevant?

Background:

To date, no drugs have been approved for gambling disorder. Numerous publications have described the value of opioid antagonists. Indeed, the mesocorticolimbic dopaminergic pathway has been suggested as the underlying cause of reward-seeking behaviour, and it is modulated by the opioid system.

Objective:

This study aims to evaluate the relevance of opioid antagonists for treating GD.

Method:

A systematic literature review was conducted. A search of the PubMed electronic database, PsycINFO and the Cochrane Systematic Review Database without any limits was performed.

Results:

There is little information concerning the effects of opioid antagonists on GD. The total search with “nalmefene and gambling” without any limits revealed only 11 articles. The search with “naltrexone and gambling” without any limits gener-ated 47 articles. Nevertheless, the best available data support the use of opioid antagonists, particularly in individuals with a history of alcohol use disorder or strong gambling urges.

Conclusion:

Future trials are still needed. Indeed, opioid antagonists effectiveness has been investigated in only a limited number of patients, clinical trials do not reflect the heterogeneity of GD and there is little knowledge of the predictive factors of response to treatments. Moreover, differential affinity to nalmefene for kappa receptors may be associated with a particular effect in a yet to be defined addiction phenotype. Head to head comparisons between naltrexone and nalmefene would be helpful in combining other medication or psychotherapy. The identification of subgroups of patients that are more likely to benefit from opioid antagonists should be a goal

Addressing Structural Flexibility at the A-Ring on Salvinorin A: Discovery of a Potent Kappa-Opioid Agonist with Enhanced Metabolic Stability

Previous structure-activity studies on the neoclerodane diterpenoid salvinorin A have demonstrated the importance of the acetoxy functionality on the A-ring in its activity as a κ-opioid receptor agonist. Few studies have focused on understanding the role of conformation in these interactions. Herein we describe the synthesis and evaluation of both flexible and conformationally restricted compounds derived from salvinorin A. One such compound, spirobutyrolactone 14, was synthesized in a single step from salvinorin B and had similar potency and selectivity to salvinorin A (EC₅₀ = 0.6 ± 0.2 nM at κ; >10000 nM at μ and δ). Microsomal stability studies demonstrated that 14 was more metabolically resistant than salvinorin A. Evaluation of analgesic and anti-inflammatory properties revealed similar in vivo effects between 14 and salvinorin A. To our knowledge, this study represents the first example of bioisosteric replacement of an acetate group by a spirobutyrolactone to produce a metabolically resistant derivative.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Nalmefene is effective at reducing alcohol seeking, treating alcohol-cocaine interactions and reducing alcohol-induced histone deacetylases gene expression in blood

BACKGROUND AND PURPOSE

The opioid antagonist nalmefene (selincro®) was approved for alcohol-related disorders by the European Medicines Agency in 2013. However, there have been no studies regarding the effectiveness of nalmefene when alcohol is used in combination with cocaine.

EXPERIMENTAL APPROACH

Using operant alcohol self-administration in Wistar rats and qRT-PCR, we evaluated (i) the dose-response curve for s.c. and p.o. nalmefene; (ii) the effects of nalmefene with increasing concentrations of alcohol; (iii) the efficacy of nalmefene on cocaine-potentiated alcohol responding; and (iv) the gene expression profiles of histone deacetylases (Hdac1-11) in peripheral blood in vivo and in the prefrontal cortex, heart, liver and kidney post mortem.

KEY RESULTS

S.c. (0.01, 0.05, 0.1 mg·kg(-1) ) and p.o. (10, 20, 40 mg·kg(-1) ) nalmefene dose-dependently reduced alcohol-reinforced responding by up to 50.3%. This effect of nalmefene was not dependent on alcohol concentration (10, 15, 20%). Cocaine potentiated alcohol responding by approximately 40% and nalmefene (0.05 mg·kg(-1) ) reversed this effect of cocaine. Alcohol increased Hdac gene expression in blood and nalmefene prevented the increases in Hdacs 3, 8, 5, 7, 9, 6 and 10. In the other tissues, alcohol and nalmefene either did not alter the gene expression of Hdacs, as in the prefrontal cortex, or a tissue-Hdac-specific effect was observed.

CONCLUSIONS AND IMPLICATIONS

Nalmefene might be effective as a treatment for alcohol-dependent patients who also use cocaine. Also, the expression of Hdacs in peripheral blood might be useful as a biomarker of alcohol use and drug response.

The Brain on Drugs: From Reward to Addiction

Advances in neuroscience identified addiction as a chronic brain disease with strong genetic, neurodevelopmental, and sociocultural components. We here discuss the circuit- and cell-level mechanisms of this condition and its co-option of pathways regulating reward, self-control, and affect. Drugs of abuse exert their initial reinforcing effects by triggering supraphysiologic surges of dopamine in the nucleus accumbens that activate the direct striatal pathway via D1 receptors and inhibit the indirect striato-cortical pathway via D2 receptors. Repeated drug administration triggers neuroplastic changes in glutamatergic inputs to the striatum and midbrain dopamine neurons, enhancing the brain's reactivity to drug cues, reducing the sensitivity to non-drug rewards, weakening self-regulation, and increasing the sensitivity to stressful stimuli and dysphoria. Drug-induced impairments are long lasting; thus, interventions designed to mitigate or even reverse them would be beneficial for the treatment of addiction.

Lipophilic nalmefene prodrugs to achieve a one-month sustained release

Nalmefene is an opioid antagonist which as a once-a-day tablet formulation has recently been approved for reducing ethanol intake in alcoholic subjects. In order to address the compliance issue in this patient population, a number of potential nalmefene prodrugs were synthesized with the aim of providing a formulation that could provide plasma drug concentrations in the region of 0.5-1.0ng/mL for a one-month period when dosed intramuscular to dogs or minipigs. In an initial series of studies, three different lipophilic nalmefene derivatives were evaluated: the palmitate (C16), the octadecyl glutarate diester (C18-C5) and the decyl carbamate (CB10). They were administered intramuscularly to dogs in a sesame oil solution at a dose of 1mg-eq. nalmefene/kg. The decyl carbamate was released relatively quickly from the oil depot and its carbamate bond was too stable to be used as a prodrug. The other two derivatives delivered a fairly constant level of 0.2-0.3ng nalmefene/mL plasma for one month and since there was no significant difference between these two, the less complex palmitate monoester was chosen to demonstrate that dog plasma nalmefene concentrations were dose-dependent at 1, 5 and 20mg-eq. nalmefene/kg. In a second set of experiments, the effect of the chain length of the fatty acid monoester promoieties was examined. The increasingly lipophilic octanoate (C8), decanoate (C10) and dodecanoate (C12) derivatives were evaluated in dogs and in minipigs, at a dose of 5mg-eq. nalmefene/kg and plasma nalmefene concentrations were measured over a four-week period. The pharmacokinetic profiles were very similar in both species with Cmax decreasing and Tmax increasing with increasing fatty acid chain length and the target plasma concentrations (0.5-1.0ng/mL over a month-long period) were achieved with the dodecanoate (C12) prodrug. These data therefore demonstrate that sustained plasma nalmefene concentrations can be achieved in both dog and minipig using nalmefene prodrugs and that the pharmacokinetic profile of nalmefene can be tuned by varying the length of the alkyl group.

Clinical experience about an unexpected adverse event during nalmefene treatment in two patients with alcohol use disorder

WHAT IS KNOWN AND OBJECTIVE

Nalmefene, a new opioid system regulator, has recently been approved for the treatment of alcohol dependence, primarily for reducing heavy drinking days.

CASES DESCRIPTION

Two patients with a diagnosis of alcohol use disorder were treated with nalmefene. Both patients developed fatigue and deep sleepiness after 2 days of treatment. Only after 1 day of drug discontinuation, symptoms normalized.

WHAT IS NEW AND CONCLUSION

We have analysed symptoms' development before and after treatment discontinuation and the possible association with nalmefene therapy. This case should pinpoint our attention on this adverse event for a careful choice of anticraving therapy in patients with severe alcohol use disorder.