Doses Of Naltrexone Research Articles

Alternative Reinforcers Enhance the Effects of Opioid Antagonists, but Not Agonists, on Oxycodone Choice Self-Administration in Nonhuman Primates.

Clinical reports suggest that the most effective strategies for managing opioid use disorder comprise a comprehensive treatment program of both pharmacological and nonpharmacological approaches. However, the conditions under which these combinations are most effective are not well characterized. This study examined whether the presence of an alternative reinforcer could alter the efficacy of Food and Drug Administration-approved opioid antagonist or agonist medications, as well as the nonopioid flumazenil, in decreasing oxycodone choice self-administration in nonhuman primates. Adult squirrel monkeys (n = 7; four females) responded under concurrent second-order fixed-ratio (FR)-3(FR5:S);TO45s schedules of reinforcement for intravenous oxycodone (0.1 mg/kg) or saline on one lever and 30% sweetened condensed milk or water on the other. Doses of naltrexone (0.00032-1.0 mg/kg), nalbuphine (0.32-10 mg/kg), buprenorphine (0.0032-0.032 mg/kg), methadone (0.32-1.0 mg/kg), or flumazenil (1-3.2 mg/kg) were administered intramuscularly prior to oxycodone self-administration sessions that occurred with either milk or water as the alternative. Naltrexone, a μ-opioid receptor antagonist, was >30-fold more potent when milk was available compared with water and abolished oxycodone intake (injections/session) while concomitantly increasing milk deliveries at the highest dose tested. Pretreatment with the low-efficacy μ-agonist nalbuphine was most effective in the presence of milk compared with water, decreasing oxycodone preference to <50% of control values. The higher efficacy μ-agonists, methadone and buprenorphine, and the benzodiazepine antagonist flumazenil did not appreciably alter the reinforcing potency of oxycodone under either condition. These results suggest that antagonist medications used in combination with alternative reinforcers may be an effective strategy to curtail opioid abuse-related behaviors. SIGNIFICANCE STATEMENT: Clinical treatment programs for opioid use disorder use a combination of pharmacological and nonpharmacological approaches. However, the conditions under which these combinations are most effective have not been fully characterized. This study examined whether the effectiveness of μ-opioid medications to decrease oxycodone self-administration is altered in the presence of an alternative reinforcer. The results suggest that alternative reinforcers enhance the effects of antagonist or low-efficacy partial agonists, suggesting they may be a more effective strategy to curtail opioid use.

Targeting α1- and α2-adrenergic receptors as a countermeasure for fentanyl-induced locomotor and ventilatory depression

This study assessed the ability of α1 and α2-adrenergic drugs to decrease fentanyl-induced locomotor and ventilatory depression. Rats were given saline or fentanyl, followed by: (1) naltrexone, (2) naloxone, (3) nalmefene, (4) α1 agonist phenylephrine, (5) α1 antagonist prazosin, (6) α1D antagonist BMY-7378, (7) α2 agonist clonidine, (8) α2 antagonist yohimbine or (9) vehicle. All µ-opioid antagonists dose-dependently reversed fentanyl-induced locomotor and ventilatory depression. While the α1 drugs did not alter the effects of fentanyl, clonidine dose-dependently decreased locomotion and respiration with and without fentanyl. Conversely, yohimbine given at a low dose (0.3–1 mg/kg) stimulated ventilation when given alone and higher doses (>1 mg/kg) partially reversed (∼50 %) fentanyl-induced ventilatory depression, but not locomotor depression. High doses of yohimbine in combination with a suboptimal dose of naltrexone reversed fentanyl-induced ventilatory depression, suggestive of additivity. Yohimbine may serve as an effective adjunctive countermeasure agent combined with naltrexone to rescue fentanyl-induced ventilatory depression.

Perioperative Naltrexone Management: A Scoping Review by the Perioperative Pain and Addiction Interdisciplinary Network.

Substance use disorders, including alcohol use disorder, are a public health concern that affect more than 150 million people globally. The opioid antagonist naltrexone is being increasingly prescribed to treat opioid use disorder, alcohol use disorder, and chronic pain. Perioperative management of patients on naltrexone is inconsistent and remains a controversial topic, with mismanagement posing a significant risk to the long-term health of these patients. This scoping review was conducted to identify human studies in which the perioperative management of naltrexone was described. This review includes a systematic literature search involving Medline, Medline In-Process, Embase, PsycINFO, and Web of Science. Seventeen articles that describe perioperative naltrexone management strategies were included, including thirteen guidelines, one case report, and three randomized trials. Despite its use in patients with alcohol use disorder and chronic pain, no clinical studies, case reports, or guidelines addressed naltrexone use in these clinical populations. All of the guideline documents recommended the preoperative cessation of naltrexone, irrespective of dose, indication, or route of administration. None of these guideline documents were designed on the basis of a systematic literature search or a Delphi protocol. As described by the primary studies, perioperative pain relief varied depending on naltrexone dose and route of administration, time since last naltrexone administration, and underlying substance use disorder. None of the studies commented on the maintenance of recovery for the patient's substance use disorder in the context of perioperative naltrexone management. The current understanding of the risks and benefits of continuing or stopping naltrexone perioperatively is limited by a lack of high-quality evidence. In patients with risk factors for return to use of opioids or alcohol, the discontinuation of naltrexone should have a strong rationale. Future studies and guidelines should seek to address both acute pain management and maintaining recovery when discussing perioperative naltrexone management strategies.

Rapid Initiation of Injection Naltrexone for Opioid Use Disorder

Injectable extended-release (XR)-naltrexone is an effective treatment option for opioid use disorder (OUD), but the need to withdraw patients from opioid treatment prior to initiation is a barrier to implementation. To compare the effectiveness of the standard procedure (SP) with the rapid procedure (RP) for XR-naltrexone initiation. The Surmounting Withdrawal to Initiate Fast Treatment with Naltrexone study was an optimized stepped-wedge cluster randomized trial conducted at 6 community-based inpatient addiction treatment units. Units using the SP were randomly assigned at 14-week intervals to implement the RP. Participants admitted with OUD received the procedure the unit was delivering at the time of their admission. Participant recruitment took place between March 16, 2021, and July 18, 2022. The last visit was September 21, 2022. Standard procedure, based on the XR-naltrexone package insert (approximately 5-day buprenorphine taper followed by a 7- to 10-day opioid-free period and RP, defined as 1 day of buprenorphine at minimum necessary dose, 1 opioid-free day, and ascending low doses of oral naltrexone and adjunctive medications (eg, clonidine, clonazepam, antiemetics) for opioid withdrawal. Receipt of XR-naltrexone injection prior to inpatient discharge (primary outcome). Secondary outcomes included opioid withdrawal scores and targeted safety events and serious adverse events. All analyses were intention-to-treat. A total of 415 participants with OUD were enrolled (mean [SD] age, 33.6 [8.48] years; 205 [49.4%] identified sex as male); 54 [13.0%] individuals identified as Black, 91 [21.9%] as Hispanic, 290 [69.9%] as White, and 22 [5.3%] as multiracial. Rates of successful initiation of XR-naltrexone among the RP group (141 of 225 [62.7%]) were noninferior to those of the SP group (68 of 190 [35.8%]) (odds ratio [OR], 3.60; 95% CI, 2.12-6.10). Withdrawal did not differ significantly between conditions (proportion of days with a moderate or greater maximum Clinical Opiate Withdrawal Scale score (>12) for RP vs SP: OR, 1.25; 95% CI, 0.62-2.50). Targeted safety events (RP: 12 [5.3%]; SP: 4 [2.1%]) and serious adverse events (RP: 15 [6.7%]; SP: 3 [1.6%]) were infrequent but occurred more often with RP than SP. In this trial, the RP of XR-naltrexone initiation was noninferior to the standard approach and saved time, although it required more intensive medical management and safety monitoring. The results of this trial suggest that rapid initiation could make XR-naltrexone a more viable treatment for patients with OUD. ClinicalTrials.gov Identifier: NCT04762537.

Low-dose naltrexone for post-COVID fatigue syndrome: a study protocol for a double-blind, randomised trial in British Columbia

IntroductionA significant proportion of individuals suffering from post COVID-19 condition (PCC, also known as long COVID) can present with persistent, disabling fatigue similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and...

Effective Doses of Low-Dose Naltrexone for Chronic Pain - An Observational Study.

Despite the availability of a wide variety of analgesics, many patients with chronic pain often experience suboptimal pain relief in part related to the absence of any medication to address the nociplastic component of common pain syndromes. Low-dose naltrexone has been used for the treatment of chronic pain, typically at 4.5 mg per day, even though it is also noted that effective doses of naltrexone for chronic pain presentations range from 0.1 to 4.5 mg per day. We performed an observational analysis to determine the range of effective naltrexone daily dosing in 41 patients with chronic musculoskeletal pain. Charts of 385 patients, 115 males, 270 females, ages 18-92, were reviewed. Two hundred and sixty patients with chronic diffuse, symmetrical pain were prescribed a titrating dose of naltrexone to determine a maximally effective dose established by self-report of 1) reduction of diffuse/generalized and/or severity level of pain and/or 2) positive effects on mood, energy, and mental clarity. Brief Pain Inventory and PROMIS scales were given pre- and post-determining a maximally effective naltrexone dose. Forty-one patients met all criteria for inclusion, successfully attained a maximally effective dose, and completed a pre- and post-outcome questionnaire. Hormesis was demonstrated during the determination of the maximally effective dosing, which varied over a wide range, with statistically significant improvement in BPI. The maximally effective dose of low-dose naltrexone for the treatment of chronic pain is idiosyncratic, suggesting the need for 1) dosage titration to establish a maximally effective dose and 2) the possibility of re-introduction of low-dose naltrexone to patients who had failed initial trials on a fixed dose of naltrexone.

Combination of low doses of Naltrexone and physical exercise in an animal fibromyalgia model

Our aim was to evaluate if a single session of physical activity until fatigue promotes analgesic effects in a fibromyalgia model, and if this effect is enhanced by low dose of naltrexone. 40 male Wistar rats were used, between 55 and 65 days-old (≥ 250g). The fibromyalgia model was developed using the reserpine model (1mg/kg, 3 consecutive days). The rats were divided into five groups: control (reserpine vehicle+naltrexone vehicle); 2nd group: fibromyalgia (reserpine+naltrexone+physical exercise); 3rd group: fibromyalgia (reserpine+naltrexone vehicle +physical exercise); 4th group: fibromyalgia (reserpine+ naltrexone + no exercise), 5th group: fibromyalgia (reserpine+naltrexone vehicle+no exercise). Interventions were: low dose of naltrexone (LDN, 0.5 mg/kg by gavage) or vehicle, and treadmill exercise or sedentary. Mechanical hyperalgesia was measured using Von-Frey test. Anxiety-like behavior was assessed using Plus-Maze test. BDNF levels were measured by ELISA. The results reserpine induced mechanical hyperalgesia in rats, and LDN associated or not to exercise presented an analgesic effect at short-term; however only LDN plus exercise was able to maintain this effect 24h after. Anxiety-like behavior and BDNF levels were modulated by LDN and exercise. LDN and exercise are promising tools to treat chronic pain as fibromyalgia.

Evaluation of the Use of Naltrexone for Cholestatic Pruritus.

Pruritus is a common symptom of liver disease, managed with various medications including opioid antagonists like naltrexone. Current literature surrounding the safety and efficacy of naltrexone for cholestatic pruritus is limited. Our objective was to describe naltrexone prescribing practices for cholestatic pruritus. We conducted a single-center, retrospective review of inpatients who received naltrexone for cholestatic pruritus. We gathered information on naltrexone dosing, frequency, dose adjustments, duration, elevations in liver function tests (LFTs), and use of additional antipruritic agents. Thirty-nine patients and 122 dosing regimens were included for analysis. Most patients were male (56.4%) with a median age of 6.32 years (range, 0.63-18.89). The median weight-based doses of naltrexone were 1.45 mg/kg/dose (IQR, 0.84-2.81) and 1.86 mg/kg/day (IQR, 0.97-3.37). The median flat doses were 25 mg/dose (IQR, 12.25-50) and 50 mg/day (IQR, 25-50). The median number of additional antipruritic agents used before and after naltrexone initiation was 3 (IQR, 2-4) and 4 (IQR, 3-5), respectively (p < 0.001). The most common elevated LFTs were total bilirubin and alanine aminotransferase (ALT), occurring in 15% of patients. Naltrexone dosing ranged between 1 and 2 mg/kg/dose once or twice daily, with larger weight-based doses prescribed in younger and lower-weight patients. Naltrexone was commonly added as a fourth-line agent and did not lead to discontinuation of other antipruritic therapies. Larger, prospective, controlled studies are needed to assess the safety and efficacy of naltrexone for cholestatic pruritus.

Use of the opioid receptor antagonist - naltrexone in the treatment of non-suicidal self-injury.

The aim of the study was to review the existing research, conducted on animal and human models, regarding the possibility of using low doses of naltrexone (LDN) in treatment of non-suicidal self-injury (NSSI). The available Polish - and English-language literature on NSSI was reviewed. Relevant studies were identified through an electronic search of PubMed/MEDLINE and Google Scholar databases using the following keywords: non-suicidal self-injury, NSSI, naltrexone, LDN, self-injury, self-harm, and time descriptors 1982-2022. The review was based on information reported in original papers, review articles and case reports. The quality of the article was assessed using the six-point Scale for the Assessment of Narrative Review Articles (SANRA). Studies conducted on animal models show that use of LDN can prevent habitual self-injury. As far as the possibility of clinical use of LDN in treatment of NSSI is concerned, results of a relatively small number of studies conducted so far confirm the efficacy of using naltrexone 25-50 mg/day to decrease or eliminate self-injurious behaviors in NSSI patients. The use of LDN in treatment of NSSI seems to be a promising clinical option, whose efficacy, however, needs to be corroborated in a larger number of randomized placebo-controlled clinical trials.

Acute Low Dose Naltrexone Increases β-Endorphin and Promotes Neuronal Recovery Following Hypoxia-Ischemic Stroke in Type-2 Diabetic Mice.

Diabetic patients experience significant mortality and poor recovery following ischemic stroke. Our clinical and basic science studies demonstrate an overall immune suppression in the periphery of diabetic stroke patients, as well as within the central nervous system (CNS) of type-2 diabetic mice following hypoxia-ischemia (HI). Low doses of naltrexone (LDN) improved clinical outcomes in many autoimmune diseases by acting on opioid receptors to release β-endorphin which in turn balances inflammatory cytokines and modulates the opioid growth factor (OGF)-opioid growth factor receptor (OGFr) pathway. We hypothesized that in our model of diabetic mice, LDN treatment will induce the release of β-endorphin and improve CNS response by promoting neuronal recovery post HI. To test this hypothesis, we induced HI in 10week old male db/db and db/ + mice, collected tissue at 24 and 72h post HI, and measured OGF levels in plasma and brain tissue. The infarct size and number of OGF + neurons in the motor cortex, caudate and hippocampus (CA3) were measured. Following HI, db/db mice had significant increases in brain OGF expression, increased infarct size and neurological deficits, and loss of OGFr + neurons in several different brain regions. In the second experiment, we injected LDN (1mg/kg) intraperitoneally into db/db and db/ + mice at 4, 24, and 48h post HI, and collected brain tissue and blood at 72h. Acute LDN treatment increased β-endorphin and OGF levels in plasma and promoted neuronal recovery in db/db mice compared to phosphate buffer saline (PBS)-treated diabetic mice suggesting a protective or regenerative effect of LDN.

481 Interactions between buprenorphine and norbuprenorphine in neonatal opioid withdrawal syndrome

OBJECTIVES/GOALS: Buprenorphine (BUP) is used for opioid use disorder during pregnancy but causes neonatal opioid withdrawal syndrome (NOWS). The goal of this study was to determine the contribution of the active metabolite, norbuprenorphine (NorBUP), to the development of NOWS when the parent drug, BUP, is administered during pregnancy. METHODS/STUDY POPULATION: Subcutaneously implanted osmotic minipumps delivered BUP (0, 0.01, 0.1 or 1 mg/kg/day) ± NorBUP (1 mg/kg/day) to pregnant Long-Evans rats from gestation day 9 until after delivery. NOWS was measured between 3 and 12 hours after delivery. Withdrawal was precipitated by an intraperitoneal injection of a mu opioid receptor antagonist naltrexone (NTX; 0, 1 or 10 mg/kg), and movement duration (MD; a validated proxy for NOWS) was measured using Noldus Ethovision. Concentrations of BUP, NorBUP, and their glucuronide conjugates in the brains of neonatal littermates not undergoing withdrawal testing were determined using LC/MS/MS. Two-way ANOVA and multiple linear regression analyses tested for interactions between BUP and NorBUP on MD and related brain concentrations to MD, respectively. RESULTS/ANTICIPATED RESULTS: There was no interaction effect between BUP and NorBUP on MD for either sex or at any dose of naltrexone. In females, but not males, BUP (1 mg/kg/day) significantly increased NorBUP-induced MD by 58% following an injection with 1 mg/kg NTX. A multiple linear regression model that included BUP and NorBUP brain concentrations as predictors of MD was significant and well-fitting [FEMALES: F (2, 40) = 23.97, P &lt; .0001, adj R2 = 0.52; MALES: F (2, 40) = 5.84, P = .0059, adj R2 = 0.19]. There was a differential contribution of NorBUP brain concentrations to MD based on sex. The partial regression coefficient for NorBUP was 51.34 (p &lt; .0001) for females and 19.21 (p = 0.093) for males. The partial regression coefficient for BUP was similar for females and males (FEMALES:βBUP = 10.62, p = .0017; MALES:βBUP = 11.38, p = .009). DISCUSSION/SIGNIFICANCE: We show for the first time a differential contribution of NorBUP to BUP-associated NOWS in each sex, suggesting sex differences in NorBUP susceptibility and implicating that treatment strategies reducing prenatal NorBUP exposure may be more effective for females than males.

Opioid antagonism in humans: a primer on optimal dose and timing for central mu-opioid receptor blockade

Non-human animal studies outline precise mechanisms of central mu-opioid regulation of pain, stress, affiliation and reward processing. In humans, pharmacological blockade with non-selective opioid antagonists such as naloxone and naltrexone is typically used to assess involvement of the mu-opioid system in such processing. However, robust estimates of the opioid receptor blockade achieved by opioid antagonists are missing. Dose and timing schedules are highly variable and often based on single studies. Here, we provide a detailed analysis of central opioid receptor blockade after opioid antagonism based on existing positron emission tomography data. We also create models for estimating opioid receptor blockade with intravenous naloxone and oral naltrexone. We find that common doses of intravenous naloxone (0.10–0.15 mg/kg) and oral naltrexone (50 mg) are more than sufficient to produce full blockade of central MOR (>90% receptor occupancy) for the duration of a typical experimental session (~60 min), presumably due to initial super saturation of receptors. Simulations indicate that these doses also produce high KOR blockade (78–100%) and some DOR blockade (10% with naltrexone and 48–74% with naloxone). Lower doses (e.g., 0.01 mg/kg intravenous naloxone) are estimated to produce less DOR and KOR blockade while still achieving a high level of MOR blockade for ~30 min. The models and simulations form the basis of two novel web applications for detailed planning and evaluation of experiments with opioid antagonists. These tools and recommendations enable selection of appropriate antagonists, doses and assessment time points, and determination of the achieved receptor blockade in previous studies.

Chronic Intermittent Sucrose Consumption Facilitates the Ability to Discriminate Opioid Receptor Blockade with Naltrexone in Rats.

The opioid antagonist naltrexone (NTX) decreases intake of preferred diets in rats at very low doses relative to doses needed to decrease intake of “bland” laboratory chow. In the absence of an opioid agonist, NTX is not discriminable using operant techniques. In the current study, we found that rats given intermittent access to a 25% sucrose solution learned to discriminate between various naltrexone doses and saline. None of the rats given only water learned to discriminate between naltrexone and saline. When access to the sucrose solution was discontinued for 14 days, the rats lost the ability to discriminate between NTX and saline. We also studied the changes of c-Fos IR in selected brain regions in rats treated with saline versus NTX that were drinking water or 25% sucrose. An injection of NTX or saline resulted in a significant drug, diet, and interaction effect in various brain regions associated with feeding behavior, particularly the amygdala, accumbens, and hypothalamic sites. Thus, we found that ingestion of a sucrose solution results in the ability of rats to reliably discriminate naltrexone administration. In addition, sucrose and naltrexone altered c-Fos IR in an interactive fashion in brain regions known to be involved in ingestion behavior.

Naltrexone at low doses (LDN) and its relevance to cancer therapy

ABSTRACT Introduction Naltrexone was designed to inhibit opioid receptors without activating them and hence used to block the stimulatory effects of morphine and heroin. It was noted that in certain patients being treated with naltrexone for an opioid addiction many reported significant secondary benefit when being weaned off naltrexone. This group of patients had chronic inflammatory and autoimmune conditions and reported improvements whilst using the lower dosages of naltrexone. There have also been recent anecdotal reports of cancer resolution following the use of low doses of naltrexone (LDN). However, the mechanism of action is unclear. Areas covered We review three mechanisms through which LDN can influence cancer progression; namely, (a) antagonism of receptors to which LDN binds, which include toll-like receptors 7–9 that lead to IL-6 suppression b) modulation of immune function in patients; and c) direct inhibition of signaling pathways involved in cancer cell control, including the priming of pro-apoptotic pathways. Expert opinion Considering the increase in the number of anecdotal reports of activity, there will likely be a bigger drive toward using LDN in the oncological setting. These reports support clinical trials of LDN in cancer, especially when given in combination with certain chemotherapy.

Patient characteristics associated with initiation of XR-naltrexone for opioid use disorder in clinical trials

BackgroundExtended-release injectable naltrexone (XR-naltrexone) is effective for treatment of patients with opioid use disorder (OUD), but initiation remains a barrier due to the challenge of tolerating opioid withdrawal prior to administration. Understanding factors associated with successful initiation of XR-naltrexone could facilitate its implementation through patient-treatment matching. MethodsWe combined data from five consecutive studies that sought to initiate patients with active opioid use onto XR-naltrexone using a rapid procedure consisting of minimal buprenorphine, non-opioid medications for treating opioid withdrawal, and ascending low doses of oral naltrexone. Associations between patient characteristics and initiating naltrexone were estimated with logistic regression models. To evaluate whether associations differed between inpatient and outpatient settings, patient characteristic-by-setting interactions were also estimated. Results409 patients were included in the analyses and 228 (56%) received the first injection. A significantly greater percent of inpatients (62%) vs outpatients (48%) initiated XR-naltrexone. Initiation success was significantly more likely on an inpatient basis for heroin (60.9% inpatient vs 36.2% outpatient), intravenous (56.3% inpatient vs 22.5% outpatient), and speedball users (68.1% inpatient vs 32.3% outpatient). Prescription opioid users showed similar, higher initiation rates across settings (68.9% inpatient; 73.7% outpatient). ConclusionsAn inpatient setting may be the preferred strategy for rapid initiation of XR-naltrexone for opioid users with greater severity, including heroin or speedball injection users or those who use opioids intravenously. Initiation on an outpatient basis may be more likely to succeed for prescription opioid users.

Aticaprant (Clinically Developed Kappa-Opioid Receptor Antagonist) Combined With Naltrexone Prevents Alcohol "Relapse" Drinking.

Alcohol relapse is the treatment target for medications development for alcohol dependence. Aticaprant, a selective and short-acting kappa-opioid receptor (KOR) antagonist, has recently been under development for new clinical implications (depression or anhedonia). Recent studies have also found that aticaprant reduces alcohol intake and prevents stress- triggered alcohol seeking in rodents via a KOR-mediated mechanism. Here, we further investigated whether aticaprant alone or in combination with naltrexone (mu-opioid receptor [MOR] antagonist) altered alcohol relapse-like drinking using a mouse alcohol deprivation effect (ADE) paradigm to mimic the relapse episodes in human alcoholics. A long-acting and selective KOR antagonist nor-BNI was used as a reference compound for the effects of the KOR antagonism on the ADE. After 3-week intermittent-access alcohol drinking (two-bottle choice, 24-h access every other day), male and female mice displayed excessive alcohol intake and then pronounced ADE after 1-week abstinence. Aticaprant alone decreased alcohol ADE in a dose- dependent manner (1–3 mg/kg) in both males and females. Aticaprant at a lower dose (0.3 mg/kg) than the effective one (3 mg/kg) combined with a low dose of naltrexone (1 mg/kg) reduced the ADE in both sexes, and the combination was effective after a multi-dosing regimen (5 daily injections during the abstinence) without development of tolerance, suggesting synergistic effects of the combination. In contrast, nor-BNI alone or with naltrexone had no effect on the ADE in either sex. Our present study suggests that a combination of clinically developed, short-acting KOR antagonist aticaprant with low-dose naltrexone has therapeutic potential in alcohol “relapse” treatment.

Acute Hypophagia and Changes in c-Fos Immunoreactivity in Adolescent Rats Treated with Low Doses of Oxytocin and Naltrexone.

A recent case report has shown that an adjunctive oxytocin + naltrexone (OT + NTX) treatment promoted more robust hypophagia and body weight reduction than OT alone in an adolescent male with hypothalamic obesity after craniopharyngioma resection. Thus far, there has been no basic research in adolescent laboratory animals that would examine whether the benefit of OT + NTX on appetite extends onto adolescent individuals without surgically induced overeating. Thus, here we examined whether low doses of combined OT + NTX acutely affect post-deprivation intake of energy-dense, standard chow; intake of energy-dense and palatable high-fat high-sugar (HFHS) diet; or calorie-dilute, palaTable 10% sucrose solution without deprivation in adolescent male rats. We assessed whether OT + NTX decreases water intake after water deprivation or produces a conditioned taste aversion (CTA). Finally, by using c-Fos immunoreactivity, we determined changes in activity of feeding-related brain areas after OT + NTX. We found that individual subthreshold doses of OT and NTX decreased feeding induced by energy and by palatability. Significant c-Fos changes were noted in the arcuate and dorsomedial hypothalamic nuclei. The hypophagic doses of OT + NTX did not suppress water intake in thirsty rats and did not cause a CTA, which suggests that feeding reduction is not a secondary effect of gastrointestinal discomfort or changes in thirst processing. We conclude that OT + NTX is an effective drug combination to reduce appetite in adolescent male rats.

Low-Dose Naltrexone Co-Treatment in the Prevention of Opioid-Induced Hyperalgesia.

Opioid-induced hyperalgesia (OIH) is characterized by a heightened sensitivity to pain that occurs in patients following opioid use. Prescription of opioids is currently the standard form of pain management for both neuropathic and nociceptive pain, due to the relief that patients typically report following their use. Opioids, which aim to provide analgesic effects, can paradoxically cause increasing degrees of pain among the users. The increased nociception can be either due to the underlying pain for which the opioid was initially prescribed, or other unrelated pain. As a result, those who are initially prescribed opioids for chronic pain relief may instead be left with no overall relief, and experience additional algesia. While OIH can be treated through the reduction of opioid use, antagonistic treatment can also be utilized. In an attempt to reduce OIH in patients, low doses of the opioid antagonist naltrexone can be given concurrently. This review will analyze the current role and effectiveness of the use of naltrexone in managing OIH in opioid users as described in clinical and non-clinical studies. Additionally, it seeks to characterize the underlying mechanisms that enable opioid antagonist naltrexone to reduce OIH while still allowing opioids to act as an analgesic. The authors find that OIH is a prevalent condition, and in order to effectively combat it, clinicians and patients can benefit from an extended study on how naltrexone can be utilized as a treatment alongside opioids prescribed for pain management.

Spillover of Medicaid Expansion to Prescribing of Opioid Use Disorder Medications in Medicare Part D.

The authors examined whether there were positive spillovers in opioid use disorder medication prescribing to Medicare Part D beneficiaries in Medicaid expansion states. Although prior studies have shown several positive benefits of Medicaid expansion for Americans with opioid use disorder, research has not examined potential spillovers to Medicare beneficiaries who have been hit hard by the opioid crisis. Prescribing data were taken from the Medicare Part D Prescription Public Use File (2010-2017). A difference-in-differences linear regression framework was used to identify spillovers in prescribing of buprenorphine and injectable naltrexone to Medicare Part D beneficiaries in Medicaid expansion states. Three sets of dependent variables measured medication prescribing at the county-year level (N=24,850). All models included county and year fixed effects, with standard errors clustered at the state level to address within-state serial correlation. Medicaid expansion was associated with an increase in the probability of a county having an injectable naltrexone provider (p<0.01). After expansion, the number of buprenorphine providers in expansion states increased by 5.6% (p<0.05), and the number of injectable naltrexone providers increased by 3.3% (p<0.01), relative to nonexpansion states. Expansion was associated with a 23.1% (p<0.01) increase in the number of daily doses of injectable naltrexone, relative to nonexpansion states. Medicaid expansion states may be better equipped to address the opioid crisis because of direct benefits to Medicaid beneficiaries and availability of opioid use disorder medications for Medicare Part D beneficiaries. However, additional efforts are likely needed to close the opioid use disorder treatment gap for Medicare beneficiaries.

Varenicline with naltrexone curbs smoking and drinking

Varenicline, marketed as Chantix, is known to help reduce smoking, but it may be effective in reducing alcohol consumption, a recent study has found. The study involved 165 people who received varenicline, for smoking, and naltrexone, which is used to treat alcoholism. The participants in the study smoked at least five cigarettes a day and consumed more than 14 drinks a week (men) and more than seven drinks a week (women). Over the course of the 12‐week study period, each participant received 2 milligrams of varenicline twice a day. Half the group also received a 50‐milligram dose of naltrexone daily, while the other 82 received placebo pills. All participants were told to quit smoking and drink less.