The subjective, reinforcing, and analgesic effects of oxycodone in patients with chronic, non-malignant pain who are maintained on sublingual buprenorphine/naloxone

Human laboratory models of reward in substance use disorder

Human laboratory models in substance use disorder provide a key intermediary step between highly controlled and mechanistically informative non-human preclinical methods and clinical trials conducted in human populations. Much like preclinical models, the variety of human laboratory methods provide insights into specific features of substance use disorder rather than modelling the diverse causes and consequences simultaneously in a single model. This narrative review provides a discussion of popular models of reward used in human laboratory research on substance use disorder with a focus on the specific contributions that each model has towards informing clinical outcomes (forward translation) and analogs within preclinical models (backward translation). Four core areas of human laboratory research are discussed: drug self-administration, subjective effects, behavioral economics, and cognitive and executive function. Discussion of common measures and models used, the features of substance use disorder that these methods are purported to evaluate, unique issues for measure validity and application, and translational links to preclinical models and special considerations for studies wishing to evaluate homology across species is provided.

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

Day-to-day hedonic and calming effects of opioids, opioid craving, and opioid misuse among patients with chronic pain prescribed long-term opioid therapy

ABSTRACT

Concerns have been raised regarding the misuse of opioids among patients with chronic pain. Although a number of factors may contribute to opioid misuse, research has yet to examine if the hedonic and calming effects that can potentially accompany the use of opioids contribute to opioid misuse. The first objective of this study was to examine the degree to which the hedonic and calming effects of opioids contribute to opioid misuse in patients with chronic pain. We also examined whether the hedonic and calming effects of opioids contribute to patients' daily levels of opioid craving, and whether these associations were moderated by patients' daily levels of pain intensity, catastrophizing, negative affect, or positive affect. In this longitudinal diary study, patients (n = 103) prescribed opioid therapy completed daily diaries for 14 consecutive days. Diaries assessed a host of pain, psychological, and opioid-related variables. The hedonic and calming effects of opioids were not significantly associated with any type of opioid misuse behavior. However, greater hedonic and calming effects were associated with heightened reports of opioid craving (both P's < 0.005). Analyses revealed that these associations were moderated by patients' daily levels of pain intensity, catastrophizing, and negative affect (all P's < 0.001). Results from this study provide valuable new insights into our understanding of factors that may contribute to opioid craving among patients with chronic pain who are prescribed long-term opioid therapy. The implications of our findings for the management of patients with chronic pain are discussed.

Minocycline attenuates oxycodone-induced positive subjective responses in non-dependent, recreational opioid users

BACKGROUND

Recent data suggest that glial cells may be involved in the analgesic effects and abuse liability of opioids. Preclinical studies have demonstrated that mu-opioid-receptor-selective agonists, such as oxycodone, activate glia and increase the release of cytokines, causing a suppression of opioid-induced analgesic effects. Preclinical studies also show that certain medications, such as the broad-spectrum tetracycline antibiotic minocycline, inhibit opioid-induced glial activation and thereby enhance the analgesic effects of opioids. Importantly, minocycline reduces the rewarding effects of opioids at the same doses that it enhances opioid-induced analgesia.

AIMS

The purpose of the present study was to assess the effects of acute administration of minocycline on the subjective, physiological, and analgesic effects of oxycodone in human research volunteers.

DESIGN

This study was a within-subject, randomized, double-blind outpatient study. Participants completed five separate sessions in which they received 0, 100, or 200 mg minocycline (MINO) simultaneously with either 0 or 40 mg oxycodone (OXY). The subjective, physiological, and analgesic effects of OXY were measured before and repeatedly after drug administration.

SETTINGS AND PARTICIPANTS

Participants were between 21 and 45 years of age, non-treatment seeking, non-dependent recreational opioid users (N = 12). This study was conducted between 2013 and 2014 at the New York State Psychiatric Institute in New York, NY.

FINDINGS

MINO 100 and 200 mg were safe and well-tolerated in combination with OXY 40 mg. MINO 200 mg administered with OXY 40 mg attenuated OXY-induced positive subjective effects such as "Good Effect" and "Liking" compared to OXY alone. MINO did not alter the physiological or analgesic effects of OXY.

CONCLUSIONS

MINO may attenuate the abuse liability of mu-opioid-receptor-selective agonists.

Nonclinical safety assessment of PF614: A novel TAAP prodrug of oxycodone for chronic pain indication

PF614, a novel trypsin activated abuse protection (TAAP) prodrug of oxycodone, is being studied as chronic pain analgesic with extended release and abuse resistant properties. A series of nonclinical safety studies were conducted to support PF614 introduction to clinical trials. Ames assays (PF614 and its metabolites), comet assay (PF614 ≤ 50 mg/kg/day oral gavage in rats) and micronucleus assay (PF614 ≤ 175 mg/kg/day oral gavage in rats) were negative. hERG assay IC50 for PF614 was ≥300 μM. PF614 (0.1 and 10 μM) showed a low permeability in Caco-2 cells (≤1.17 x 10-6 cm/s) and was not a P-gp or BCRP substrate or inhibitor. The mean percent unbound PF614 among all concentrations in plasma ranged from 91.2 to 98.4, 79.4 to 100, and 52.9-79.9% in rat, dog, and human, respectively. Also, PF614 was metabolically stable in rat, dog, and human hepatocytes with no metabolites identified. Safety pharmacology study in dog indicated moderately lower heart rate at ≥ 2 mg/kg oral gavage doses. Toxicity studies of PF614 in rat and dog with daily oral doses of 25 and 18 mg/kg, respectively, for 14 Days were well tolerated with favorable safety profile supporting its further clinical evaluation.

Psycho-physiological response to pain among individuals with comorbid pain and opioid use disorder: Implications for patients with prolonged abstinence

Background: Individuals with comorbid opioid addiction and pain (COAP) relapse 3-5 times more often than patients with opioid use disorder (OUD) but without pain. However, psychophysiological responses to pain among a COAP population are unknown. Objectives: We hypothesized that those on Medications for Opioid Use Disorder (MOUD) with chronic pain, relative to opioid-naïve chronic pain individuals, would show greater psycho-physiological pain reactivity and slower recovery when exposed to acute pain. Methods: Four groups with chronic pain were recruited (N = 120; 60% Female): 1) MOUD-methadone; 2) MOUD-buprenorphine; 3) history of completed MOUD with prolonged opioid abstinence (PA; M_abstinence = 121 weeks; SD = 23.3); and 4) opioid-naïve. We assessed heart rate (HR), galvanic skin conductance (GSC), peripheral temperature, and frontalis electromyography (EMG) during a cold pain task. Results: MOUD subjects had delayed HR reactivity to pain compared to those not on MOUD (PA & opioid-naïve; F(3,119) = 2.87, p < .04). The PA group showed a normal HR reactivity pattern, but had higher HR compared to the opioid-naïve group. The GSC group x time analysis showed the PA group had greater baseline levels and pain reactivity than the other groups (F(3,119) = 3.84, p < .02). The opioid-naïve group had lower reactivity on peripheral temperature compared to other groups (F(3,119) = 9.69, p < .001). Conclusion: Greater psychophysiological reactivity to pain was experienced by co-morbid OUD/chronic pain subjects who had been opioid abstinent for an extended period, possibly due to the lack of a buffering effect of opioid agonists. These subjects may develop coping skills to tolerate pain distress, thereby avoiding relapse in response to pain triggers. Understanding how pain creates more intense psychophysiological responses among COAP patients may lead to better treatments.

The risk for problematic opioid use in chronic pain: What can we learn from studies of pain and reward?

Problematic prescription opioid use is cited as a primary contributor to the current 'opioid epidemic' in the United States, which is characterized by recent rapid increases in individuals seeking treatment for opioid dependence and staggering rates of opioid overdose deaths. Individuals with chronic pain are commonly prescribed opioids to treat pain, and by this mere exposure are at increased risk for the development of problematic opioid use. However, the factors contributing to variation in risk across patients have only recently begun to be unraveled. In the present review, we describe the recent and expanding literature on interactions between pain and reward system function in an effort to inform our understanding of risk for problematic opioid use in chronic pain. To that end, we describe the limited experimental evidence regarding opioid abuse liability under conditions of pain, and offer suggestions for how to advance a research agenda that better informs clinicians about the factors contributing to opioid addiction risk in patients with chronic pain. We raise mechanistic hypotheses by highlighting the primary conclusions of several recent reviews on the neurobiology of pain and reward, with an emphasis on describing dopamine deficits in chronic pain, the role of the reward system in mediating the affective and motivational components of pain, and the role of opponent reward/anti-reward processes in the perpetuation of pain states and the development of problematic opioid use behaviors. Finally, we also argue that positive affect-which is directly regulated by the mesolimbic reward system-is a key pain inhibitory factor that, when deficient, may increase risk for problematic opioid use, and present a model that integrates the potential contributions of pain, reward system function, and positive affect to problematic opioid use risk.

2017 HIVMA of IDSA Clinical Practice Guideline for the Management of Chronic Pain in Patients Living With HIV

Pain has always been an important part of human immunodeficiency virus (HIV) disease and its experience for patients. In this guideline, we review the types of chronic pain commonly seen among persons living with HIV (PLWH) and review the limited evidence base for treatment of chronic noncancer pain in this population. We also review the management of chronic pain in special populations of PLWH, including persons with substance use and mental health disorders. Finally, a general review of possible pharmacokinetic interactions is included to assist the HIV clinician in the treatment of chronic pain in this population.It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. The Infectious Diseases Society of American considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

BOLD Imaging in Awake Wild-Type and Mu-Opioid Receptor Knock-Out Mice Reveals On-Target Activation Maps in Response to Oxycodone

Blood oxygen level dependent (BOLD) imaging in awake mice was used to identify differences in brain activity between wild-type, and Mu (μ) opioid receptor knock-outs (MuKO) in response to oxycodone (OXY). Using a segmented, annotated MRI mouse atlas and computational analysis, patterns of integrated positive and negative BOLD activity were identified across 122 brain areas. The pattern of positive BOLD showed enhanced activation across the brain in WT mice within 15 min of intraperitoneal administration of 2.5 mg of OXY. BOLD activation was detected in 72 regions out of 122, and was most prominent in areas of high μ opioid receptor density (thalamus, ventral tegmental area, substantia nigra, caudate putamen, basal amygdala, and hypothalamus), and focus on pain circuits indicated strong activation in major pain processing centers (central amygdala, solitary tract, parabrachial area, insular cortex, gigantocellularis area, ventral thalamus primary sensory cortex, and prelimbic cortex). Importantly, the OXY-induced positive BOLD was eliminated in MuKO mice in most regions, with few exceptions (some cerebellar nuclei, CA3 of the hippocampus, medial amygdala, and preoptic areas). This result indicates that most effects of OXY on positive BOLD are mediated by the μ opioid receptor (on-target effects). OXY also caused an increase in negative BOLD in WT mice in few regions (16 out of 122) and, unlike the positive BOLD response the negative BOLD was only partially eliminated in the MuKO mice (cerebellum), and in some case intensified (hippocampus). Negative BOLD analysis therefore shows activation and deactivation events in the absence of the μ receptor for some areas where receptor expression is normally extremely low or absent (off-target effects). Together, our approach permits establishing opioid-induced BOLD activation maps in awake mice. In addition, comparison of WT and MuKO mutant mice reveals both on-target and off-target activation events, and set an OXY brain signature that should, in the future, be compared to other μ opioid agonists.

Sex differences among opioid-abusing patients with chronic pain in a clinical trial

BACKGROUND

The characteristics of patients with co-occurring chronic pain and prescription opioid abuse have not been well described, and even less is known about differences between men and women in this population.

OBJECTIVES

This study evaluated sex differences in the demographic, diagnostic, and behavioral attributes of patients with chronic pain and opioid abuse.

METHODS

Data were collected via self-report and semistructured clinical interviews from 162 patients (120 men and 42 women) who screened for a study investigating the abuse liability of prescription opioids.

RESULTS

There were no differences between men and women in age, race, education, marital status, or employment status. Participants had used prescription opioids for 5.4 ± 6.7 years. The majority of participants (60%) had low back pain in addition to opioid dependence as defined by the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition. More women reported more arthritic pain than men, but otherwise there were no differences in types of pain. Pain exerted a greater effect in women on mood, walking ability, and social relations. Men reported more of certain aberrant behaviors, including abuse of alcohol or illicit drugs, unauthorized dose increases, contact with street culture, and being arrested by police. Women were more depressed than men.

CONCLUSIONS

The demographic profile of opioid-abusing patients with chronic pain presenting for treatment in a clinical trial was similar between sexes; however, some important differences were observed. Women reported more psychiatric comorbidity and endorsed greater pain-related physical and social impairment. Men reported more aberrant behaviors. These differences suggest that men with chronic pain and opioid abuse/dependence may benefit by closer monitoring of aberrant behaviors whereas women may benefit from closer attention paid to physical and psychological effects of pain.

Effects of Acute and Repeated Administration of Oxycodone and Naloxone-Precipitated Withdrawal on Intracranial Self-Stimulation in Rats

Incidence of prescription opioid abuse and overdose, often led by oxycodone, continues to increase, producing twice as many overdose deaths as heroin. Surprisingly, preclinical reports relevant to oxycodone's abuse-related effects are relatively sparse considering its history and patient usage. The goal of this study was to characterize dose- and time-dependent effects of acute and repeated oxycodone administration in a frequency-rate intracranial self-stimulation (ICSS) procedure, an assay often predictive of drug-related reinforcing effects, in male Sprague-Dawley rats. We hypothesized that oxycodone would produce a biphasic profile of rate-increasing and rate-decreasing effects maintained by ICSS similar to μ-opioid receptor agonists. Oxycodone (0.03, 0.3, 1, and 3 mg/kg, s.c.) produced dose- and time-dependent alterations on ICSS, with the predicted biphasic profile of rate-increasing effects at lower stimulation frequencies followed by rate-decreasing effects at higher frequencies. Peak effects were observed between 30 and 60 minutes, which were reversed by naloxone pretreatment (30 minutes). Tolerance to rate-decreasing effects was observed over a 5-day period when rats were treated with 1 mg/kg oxycodone twice a day. Subsequently, the dosing regimen was increased to 3 mg/kg twice a day over 10 days, although further marked tolerance did not develop. When then challenged with 10 mg/kg naloxone, a significant suppression below baseline levels of ICSS-maintained responding occurred indicative of dependence that recovered to baseline within 5 hours. The results of this study provide the first report of acute and chronic effects of oxycodone on responding maintained by ICSS presentation and the use of ICSS-maintained responding to characterize its tolerance and dependence effects.

Need and utility of a polyethylene glycol marker to ensure against urine falsification among heroin users

BACKGROUND

Deceptive methods of falsifying urine samples are of concern for anyone who relies on accurate urine toxicology results. A novel method to combat these efforts utilizes polyethylene glycol (PEG) markers administered orally prior to providing a urine sample. By using various PEG combinations to create a tracer capsule of unique composition, each urine sample can be matched to that individual. The goal of this study was to determine the effectiveness of using the PEG marker system among active heroin users screening for research studies.

METHODS

Upon each screening visit, participants (N=55) were randomized to provide an unobserved urine sample, or the PEG tracer procedure was used. LCMS analysis was used to distinguish the PEG combinations, and allowed us to provide a unique qualitative analysis of patterns of drug use (N=168, total urine specimens).

RESULTS

The unique composition of the tracer capsules was accurately detected in 83.5% of the urine specimens. Analyses of inconsistencies implicated a number of possible attempts at fraudulence (11.4%) and investigator/lab error (5.1%). Among this sample, the concurrent use of multiple classes of psychoactive drugs was more common than not, though concomitant drug use was often underreported.

CONCLUSION

Urine drug testing should be the minimum standard for obtaining information about drug use as self-report was unreliable even in a situation where there were no perceived adverse consequences for full disclosure. In cases where there are significant pressures for individuals to falsify these data, more protective collection methods such as the PEG marker system should be considered.

Abuse potential of intranasal buprenorphine versus buprenorphine/naloxone in buprenorphine-maintained heroin users

In spite of the clinical utility of buprenorphine, parenteral abuse of this medication has been reported in several laboratory investigations and in the real world. Studies have demonstrated lower abuse liability of the buprenorphine/naloxone combination relative to buprenorphine alone. However, clinical research has not yet examined the utility of the combined formulation to deter intranasal use in a buprenorphine-maintained population. Heroin-using volunteers (n = 12) lived in the hospital for 8-9 weeks and were maintained on each of three sublingual buprenorphine doses (2, 8, 24 mg). Under each maintenance dose, participants completed laboratory sessions during which the reinforcing and subjective effects of intranasal doses of buprenorphine (8, 16 mg), buprenorphine/naloxone (8/2, 8/8, 8/16, 16/4 mg) and controls (placebo, heroin 100 mg, naloxone 4 mg) were assessed. Intranasal buprenorphine alone typically produced increases in positive subjective effects and the 8 mg dose was self-administered above the level of placebo. The addition of naloxone dose dependently reduced positive subjective effects and increased aversive effects. No buprenorphine/naloxone combination dose was self-administered significantly more than placebo. These data suggest that within a buprenorphine-dependent population, intranasal buprenorphine/naloxone has reduced abuse potential in comparison to buprenorphine alone. These data strongly argue in favor of buprenorphine/naloxone rather than buprenorphine alone as the more reasonable option for managing the risk of buprenorphine misuse.

Chronic pain and depression among primary care patients treated with buprenorphine

BACKGROUND

Pain and depression are each prevalent among opioid dependent patients receiving maintenance buprenorphine, but their interaction has not been studied in primary care patients.

OBJECTIVE

We set out to examine the relationship between chronic pain, depression, and ongoing substance use, among persons maintained on buprenorphine in primary care settings.

DESIGN

Between September 2012 and December 2013, we interviewed buprenorphine patients at three practice sites.

PARTICIPANTS

Opioid dependent persons at two private internal medicine offices and a federally qualified health center participated in the study.

MAIN MEASURES

Pain was measured in terms of chronicity, with chronic pain being defined as pain lasting at least 6 months; and in terms of severity, as measured by self-reported pain in the past week, measured on a 0-100 scale. We defined mild chronic pain as pain severity between 0 and 39 and lasting at least 6 months, and moderate/severe chronic pain as severity ≥ 40 and lasting at least 6 months. To assess depression, we used the Center for Epidemiologic Studies Depression (CESD) ten-item symptom scale and the two-item Patient Health Questionnaire (PHQ-2).

KEY RESULTS

Among 328 participants, 169 reported no chronic pain, 56 reported mild chronic pain, and 103 reported moderate/severe chronic pain. Participants with moderate/severe chronic pain commonly used non-opioid pain medications (56.3%) and antidepressants (44.7%), yet also used marijuana, alcohol, or cocaine (40.8%) to help relieve pain. Mean CESD scores were 7.1 (±6.8), 8.3 (±6.0), and 13.6 (±7.6) in the no chronic, mild, and moderate/severe pain groups, respectively. Controlling for covariates, higher CESD scores were associated with a higher likelihood of moderate/severe chronic pain relative to both no chronic pain (OR = 1.09, p < 0.001) and mild chronic pain (OR = 1.06, p = 0.04).

CONCLUSION

Many buprenorphine patients are receiving over-the-counter or prescribed pain medications, as well as antidepressants, and yet continue to have significant and disabling pain and depressive symptoms. There is a clear need to address the pain-depression nexus in novel ways.

Sublingual buprenorphine as an analgesic in chronic pain: a systematic review

OBJECTIVE

There is growing interest in the use of sublingual buprenorphine for the treatment of chronic pain due to the unique pharmacology of buprenorphine, widespread use of the transdermal buprenorphine patch for chronic pain, and recent availability of sublingual buprenorphine tablets for the treatment of opioid dependence. The aim of this systematic review was to evaluate the evidence from clinical trials that have assessed the effectiveness of sublingual buprenorphine for chronic pain analgesia.

METHODS

Electronic searches of MEDLINE, Embase, CINAHL, Web of Science, and the Cochrane Database of Systematic Reviews were used to identify clinical trials of sublingual buprenorphine for the treatment of chronic pain.

RESULTS

Ten trials involving 1,190 patients were included in the review. Due to heterogeneity of studies, pooling of the results and meta-analysis were not possible. All studies reported that sublingual buprenorphine demonstrated some effectiveness as a chronic pain analgesic. The majority of studies were observational and of low quality.

CONCLUSIONS

Preliminary trials suggest a plausible role; however, due to a paucity of high-quality trials, the current evidence is insufficient to determine the effectiveness of sublingual buprenorphine for the treatment of chronic pain. Rigorous further trials are warranted.

A review of human drug self-administration procedures

Drug self-administration procedures in laboratory settings allow us to closely model drug-taking behavior in real-world settings. This review provides an overview of many of the common self-administration methods used in human laboratory research. Typically, self-administration studies provide a quantifiable measure of the reinforcing effect of a drug, which is believed to be predictive of its potential for abuse. Several adaptations of the self-administration paradigm exist, the simplest of which allows participants free access to the drug under investigation. Free-access procedures allow investigators to observe patterns of drug self-administration and drug effects in a controlled setting. Allowing participants to choose between two simultaneously available reinforcers (choice procedures) is another well-established method of assessing the reinforcing effects of a drug. Offering a choice between two reinforcers (e.g. two different doses of the same drug, two different drugs, or drug and nondrug reinforcers) provides researchers with a point of comparison (e.g. between a drug of known abuse potential and a novel drug). When combined with other endpoints, such as subjective effects ratings, physiological responses, and cognitive performance, human self-administration paradigms have contributed significantly to our understanding of the factors that contribute to, maintain, and alter drug-taking behavior including: craving, positive subjective effects, toxicity, drug interactions and abstinence. This area of research has also begun to incorporate other techniques such as imaging and genetics to further understand the multifaceted nature of substance abuse. The present paper summarizes the different self-administration techniques that are commonly used today and the application of other procedures that may complement interpretation of the drug self-administration findings.

Update on tamper-resistant drug formulations

An expert panel convened in 2005 by the College on Problems of Drug Dependence (CPDD) to consider strategies to reduce the risk of prescription medication abuse concluded that drug formulation plays a significant role in determining risk of abuse. Efforts on the part of the pharmaceutical industry to develop drugs that deter abuse have focused primarily on opioid formulations resistant to common forms of tampering, most notably crushing or dissolving the tablet to accelerate release. Several opioid formulations developed to be tamper resistant have been approved, but the US Food and Drug Administration has not approved explicit label claims of abuse deterrence and has stated that any such claim will require substantial postmarketing data. Drug development efforts in this area raise questions about the relative impact of abuse-deterrent formulations, not only on individuals who might abuse a medication, but also on patients who are compliant with therapy. This review discusses progress since the 2005 CPDD meeting with an emphasis on opioids. Articles cited in the review were identified via a PubMed search covering the period between January 1, 2000, and October 5, 2011. Scientific work presented by the authors and their colleagues at meetings held through May 2012 also was included. Published literature suggests that development of abuse-deterrent products will require broad public health support and continued encouragement from regulatory authorities so that such products will become the expected standard of care for certain drug classes.

Buprenorphine/naloxone as a promising therapeutic option for opioid abusing patients with chronic pain: reduction of pain, opioid withdrawal symptoms, and abuse liability of oral oxycodone

Few studies have examined abuse of prescription opioids among individuals with chronic pain under buprenorphine/naloxone (Bup/Nx) maintenance. The current 7-week inpatient study assessed oral oxycodone self-administration by patients with chronic pain who had a history of opioid abuse. Participants (n=25) were transitioned from their preadmission prescribed opioid to Bup/Nx. All of the participants were tested under each of the sublingual Bup/Nx maintenance doses (2/0.5, 8/2 or 16/4 mg) in random order. During each maintenance period, participants could self-administer oxycodone orally (0, 10, 20, 40 or 60 mg prescription opioids) or receive money during laboratory sessions. Drug choice (percentage) was the primary dependent variable. Subjective ratings of clinical pain and withdrawal symptoms also were measured. Mann-Whitney tests compared percentage of drug choice for each active oxycodone dose to placebo. Logistic regression analyses identified correlates of oxycodone preference, defined as 60% or greater choice of oxycodone compared to money. Pain was significantly reduced while participants were maintained on Bup/Nx compared to preadmission ratings. No differences in percentage drug choice were observed between the active oxycodone doses and placebo under each Bup/Nx maintenance dose. However, factors associated with oxycodone preference were lower Bup/Nx maintenance dose, more withdrawal symptoms and more pain. These data suggest that Bup/Nx was effective in reducing pain and supplemental oxycodone use. Importantly, adequate management of pain and withdrawal symptoms by Bup/Nx may reduce oxycodone preference in this population.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Management of pain with comorbid substance abuse

Substance use disorders are a large public health problem in the United States. Over the past decade, there has been a trend of increased prescription drug misuse, morbidity, and mortality related to prescription opioids. For providers who treat pain, this has led to clinical dilemmas as the newly appreciated risks must be balanced with the benefits of treatment, particularly in patients with known substance use disorders. Acute, chronic, and palliative each present distinct issues in pain treatment. A best practices model of pain treatment, including risk stratification and integrative treatment, may provide the best prospect for safe and effective treatment.

Effects of cold pressor pain on the abuse liability of intranasal oxycodone in male and female prescription opioid abusers

BACKGROUND

Approximately 1.9 million persons in the U.S. have prescription opioid use disorders often with concomitant bodily pain, but systematic data on the impact of pain on abuse liability of opioids is lacking. The purpose of this study was to determine whether pain alters the intranasal abuse liability of oxycodone, a commonly prescribed and abused analgesic, in males and females.

METHODS

Sporadic prescription opioid abusers (10 females, 10 males) participated in this mixed (between and within-subject), randomized inpatient study. Experimental sessions (n=6) tested intranasal placebo, oxycodone 15 or 30 mg/70 kg during cold pressor testing (CPT) and a warm water control. Observer- and subject-rated drug effect measures, analgesia, physiologic and cognitive effects were assessed.

RESULTS

The CPT significantly increased blood pressure, heart rate, pain, stress, and "opiate desire" compared to the no-pain control but did not alter opioid liking, high or street value. Intranasal oxycodone produced effects within 10 min, significantly decreasing pain and significantly increasing subjective measures of abuse liability (e.g., high). Females had higher ratings of street value, high, and liking for one or both active doses.

CONCLUSIONS

The CPT was a reliably painful and stressful stimulus that did not diminish the abuse liability of intranasal oxycodone. Females were more sensitive to oxycodone on several abuse liability measures that warrant further follow-up. Snorting oxycodone rapidly produced psychoactive effects indicative of substantial abuse liability.