Principles of initial experimental drug abuse liability assessment in humans

Event-level associations among THC, CBD, social context, and subjective effects during Cannabis use episodes

BACKGROUND

Limited research considers the quantity and potency of cannabis products along with social context on the subjective effects of real-world cannabis use.

AIMS

This study examined the subjective effects of acute use as a function of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) doses and social context during cannabis use episodes.

METHOD

Ninety-six participants (43.75% male, Mage = 35.73) reporting weekly cannabis use completed a baseline self-report battery assessing cannabis use. Then, THC and CBD potency and quantity of the cannabis product, social context, and subjective experience were assessed through self-initiated surveys after cannabis use episodes during a 14-day ecological momentary assessment (EMA).

RESULTS

Greater feeling high and liking were significantly associated with a higher THC dose than one's average (b = 0.03, p < 0.001; b = 0.02, p < 0.001) and social use (b = 0.38, p < 0.001; b = 0.20, p = 0.01). A higher CBD dose than one's average (b = 0.01, p = 0.04) was significantly associated with greater liking. A significant interaction effect of THC dose and social context (b = 0.01, p = 0.02) was observed such that solitary use had a negative association between THC dose and disliking (b = -0.01, p = 0.04), and social use had a null association (b = 0.003, p = 0.25). Individuals with greater cannabis problems reported lower liking (b = -0.18, p = 0.03) and higher disliking (b = 0.08, p = 0.02), but not feeling high, on average, across the EMA protocol.

CONCLUSION

Social context plays an important role in the subjective experience of cannabis use. Interventions targeting cannabis problems could highlight the evidence that individuals with greater cannabis problems might experience less liking but more disliking in general across use episodes to effectively challenge expectancies/motives of use.

Combining noninvasive brain stimulation with behavioral pharmacology methods to study mechanisms of substance use disorder

Psychotropic drugs and transcranial magnetic stimulation (TMS) are effective for treating certain psychiatric conditions. Drugs and TMS have also been used as tools to explore the relationship between brain function and behavior in humans. Combining centrally acting drugs and TMS has proven useful for characterizing the neural basis of movement. This combined intervention approach also holds promise for improving our understanding of the mechanisms underlying disordered behavior associated with psychiatric conditions, including addiction, though challenges exist. For example, altered neocortical function has been implicated in substance use disorder, but the relationship between acute neuromodulation of neocortex with TMS and direct effects on addiction-related behaviors is not well established. We propose that the combination of human behavioral pharmacology methods with TMS can be leveraged to help establish these links. This perspective article describes an ongoing study that combines the administration of delta-9-tetrahydrocannabinol (THC), the main psychoactive compound in cannabis, with neuroimaging-guided TMS in individuals with problematic cannabis use. The study examines the impact of the left dorsolateral prefrontal cortex (DLPFC) stimulation on cognitive outcomes impacted by THC intoxication, including the subjective response to THC and the impairing effects of THC on behavioral performance. A framework for integrating TMS with human behavioral pharmacology methods, along with key details of the study design, are presented. We also discuss challenges, alternatives, and future directions.

Psychedelic drug abuse potential assessment for new drug applications and controlled substance scheduling: A United States perspective

BACKGROUND

Psychedelics are an increasingly active area of research and pharmaceutical development. This includes abuse potential assessment to better understand their pharmacological mechanisms and effects and guide controlled substance regulation. Psychedelics pose challenges to abuse assessments to ensure valid, reliable, and generalizable outcomes and safe study conduct.

FINDINGS

Key nonclinical techniques, for example, receptor binding and functional assays in vitro, and nonclinical physical dependence determinations, are easily adaptable to psychedelics. However, the entactogens (weak reinforcers) and hallucinogens (non-reinforcers) require more flexible approaches than typically recommended by regulatory agencies. Phase 1 pharmacokinetic/pharmacodynamic safety studies and Phases 2/3 efficacy/safety trials with systematic monitoring of abuse-related adverse events are readily applicable to psychedelics. Human abuse trials require modification because supratherapeutic doses may not be safe and procedures, for example, personal monitors to manage serious adverse events, might bias outcomes.

RECOMMENDATIONS

Abuse-related studies for psychedelics requiring approval by Food and Drug Administration and other agencies should take into consideration existing knowledge that will vary from extensive, for example, psilocybin, to zero for novel hallucinogens and entactogens. Many abuse assessments can be reasonably applied to animals and humans without compromising scientific integrity. Modification of existing techniques and incorporating a broader range of nonclinical tests should ensure generalizable outcomes. Human abuse studies merit reconsideration and possible modification to ensure safety and validity for psychedelic drug evaluation. Other nonclinical and clinical methods can provide evaluations of the pharmacological equivalence of test drugs to known drugs of abuse to provide context to the abuse assessment and guide drug scheduling.

A Randomized, Controlled Study to Assess Biomarkers of Exposure in Adult Smokers Switching to Oral Nicotine Products

This open-label, randomized, controlled, in-clinic, 6-parallel-group study evaluated changes in biomarkers of exposure (BoEs) to select harmful and potentially harmful constituents in adult smokers (N = 213) not planning to quit smoking. Adult smokers were randomized to continue smoking (CS), reduce smoking by 50% and dual use oral tobacco-derived nicotine (OTDN) products (VERVE chews/discs), stop smoking and exclusively use discs or chews, or stop using all tobacco products (NT). The primary objective compared 24-hour urinary total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL; a biomarker for the carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone) in dual and exclusive use of discs and chews to continue smoking and NT on day 7. NNAL levels on day 7 were significantly lower (P < .05) among dual and exclusive users of discs/chews compared to continue smoking; median percent reductions were ≈30% and ≈73%, respectively. NNAL levels were not significantly different between those who used discs/chews and the NT group. Many of the additional secondary biomarkers of exposure were significantly lower in dual users (10/19) and exclusive users of discs/chews (17/19) compared to the continue smoking group. Overall, reductions in secondary biomarkers of exposure were greater in exclusive users than dual users. The 24-hour urinary nicotine equivalents were significantly lower (P < .05) among exclusive users of discs/chews compared to continue smoking. The discs/chews appeared to be well tolerated. These results demonstrate that while switching completely to discs/chews substantially reduces exposure to select harmful and potentially harmful constituents, dual use with 50% reduction in cigarette consumption also reduces exposure. oral tobacco-derived nicotine products like discs/chews may present a harm reduction opportunity for adult smokers, particularly those not intending to quit smoking.

Nicotine pharmacokinetics and subjective responses after using nicotine pouches with different nicotine levels compared to combustible cigarettes and moist smokeless tobacco in adult tobacco users

RATIONALE

Oral tobacco-derived nicotine products include on!® nicotine pouches (NPs) which are tobacco-leaf free and available in multiple flavors and nicotine levels. Switching completely to NPs from cigarettes and moist smokeless tobacco (MST) has the potential to reduce harm for adult tobacco consumers. However, the dependence potential of NPs is not established. Therefore, we characterized the abuse potential of NPs with different nicotine levels compared to cigarettes and MST.

OBJECTIVES

To evaluate nicotine pharmacokinetics (PK) and subjective effects of NPs (ranging from 1.5 to 8 mg nicotine) compared to own brand cigarettes (OBCs) and MST (OBMST).

METHODS

We used a randomized, in-clinic, partial single-blind, 7-way crossover design to assess nicotine PK and subjective effects in dual users of cigarettes and MST.

RESULTS

The mean nicotine Cmax for NPs increased with nicotine level, ranging from 3.5 ng/mL (1.5 mg NP) to 15.4 ng/mL (8 mg NP), compared with 12.2 ng/mL for OBCs and 9.8 ng/mL for OBMST. Nicotine tmax was much longer for all NPs and OBMST (32.5-34.4 min) compared to OBCs (8.5 min). Reductions in urges to smoke after use of the 2 mg, 3.5 mg, and 8 mg NPs were not statistically different (p > 0.05) relative to OBC. Also, NPs resulted in lower ratings of positive subjective effects relative to OBCs and OBMST.

CONCLUSIONS

Overall, based on the study results and literature reported nicotine PK values for cigarettes and MST, the abuse potential of NPs is not likely to be higher than OBCs and OBMST. NPs may be potentially acceptable switching products for users of cigarettes and MST products.

Psychedelic drug abuse potential assessment research for new drug applications and Controlled Substances Act scheduling

New medicines containing classic hallucinogenic and entactogenic psychedelic substance are under development for various psychiatric and neurological disorders. Many of these, including psilocybin, lysergic acid diethylamide (LSD), and 3,4-methylenedioxymethamphetamine (MDMA) are Schedule I controlled substances of the United States Controlled Substances Act (US CSA), and similarly controlled globally. The implications of the CSA for research and medicines development, the path to approval of medicines, and their subsequent removal from Schedule I in the US are discussed. This entire process occurs within the framework of the CSA in the US and its counterparts internationally in accordance with international drug control treaties. Abuse potential related research in the US informs the eight factors of the CSA which provide the basis for rescheduling actions that must occur upon approval of a drug that contains a Schedule I substance. Abuse-related research also informs drug product labeling and the risk evaluation and mitigation strategies (REMS) will likely be required for approved medicines. Human abuse potential studies typically employed in CNS drug development may be problematic for substances with strong hallucinogenic effects such as psilocybin, and alternative strategies are discussed. Implications for research, medicinal development, and controlled substance scheduling are presented in the context of the US CSA and FDA requirements with implications for global regulation. We also discuss how abuse-related research can contribute to understanding mechanisms of action and therapeutic effects as well as the totality of the effects of the drugs on the brain, behavior, mood, and the constructs of spirituality and consciousness.

Methamphetamine, amphetamine, and aggression in humans: A systematic review of drug administration studies

The relationship between amphetamine use and aggressive or violent behaviour is unclear. This review examined laboratory data collected in humans, who were administered an acute dose of amphetamine or methamphetamine, in order to investigate the link between amphetamines and aggression. It is registered with PROSPERO (CRD42019127711). Included in the analysis are data from twenty-eight studies. Behavioural and/or subjective measures of aggression were assessed in one thousand and sixty-nine research participants, with limited amphetamine-use histories, following a single amphetamine dose (0-35mg). The available published evidence indicates that neither amphetamine nor methamphetamine acutely increased aggression as assessed by traditional laboratory measures. Future research should assess supratherapeutic amphetamine doses as well as include a broader range of multiple aggression measures, facilitating simultaneous assessment of the various components that comprise this complex, multifaceted construct.

A Brief Introduction to Human Behavioral Pharmacology: Methods, Design Considerations and Ethics

Human behavioral pharmacology methods have been used to rigorously evaluate the effects of a range of centrally acting drugs in humans under controlled conditions for decades. Methods like drug self-administration and drug discrimination have been adapted from nonhuman laboratory animal models. Because humans have the capacity to communicate verbally, self-report methods are also commonly used to understand drug effects. This perspective article provides an overview of these traditional human behavioral pharmacology methods and introduces some novel methodologies that have more recently been adapted for use in the field. Design (e.g., using placebo controls, testing multiple doses) and ethical (e.g., avoiding enrollment of individuals seeking treatment, determining capacity to consent) considerations that must be addressed when conducting these types of studies are also described.

Human Abuse Liability Assessment of Tobacco and Nicotine Products: Approaches for Meeting Current Regulatory Recommendations

Many regulatory bodies now recommend that tobacco product manufacturers provide information regarding new tobacco products' abuse liability to inform regulatory authorization of currently marketed tobacco products or new product applications (including premarket tobacco product applications in the United States). In addition, the US Food and Drug Administration (FDA) recommends including this information as part of modified risk tobacco product applications. Regulators, including FDA, and many public health officials and researchers consider abuse liability assessment a model which predicts the likelihood that the use of the tobacco product would result in addiction and be used repeatedly or even sporadically resulting in undesirable effects. Abuse liability of a new, potentially reduced harm product can also inform its ability to substitute completely for more harmful tobacco products. While many methods exist, no standard tobacco product abuse liability assessment has been established. The purpose of this review is to provide background information and practical recommendations for human abuse liability testing methods to meet tobacco regulatory needs. A combination of nicotine test product pharmacokinetic, subjective effect and/or behavioral response, and physiological response data relative to comparator products with known abuse liability satisfies some regulatory requirements. Implications: This review provides a practical inspection of the current, international regulatory recommendations for abuse liability assessment of tobacco and regulatory review of such information within the United States and also recommends study designs and methods for abuse liability testing of tobacco products based on scientific and regulatory knowledge. Given that tobacco product abuse liability testing is of increasing interest to regulatory bodies globally, especially with the emergence of novel tobacco products, this timely work provides background and functional recommendations for tobacco product abuse liability testing.

Concentration-Response Model of Immediate Release Oxycodone Drug Liking by Different Routes of Abuse

OBJECTIVE

To understand the correlation between oxycodone concentration and drug liking response for immediate-release formulations as they relate to different doses and different routes of administration following manipulation involved in opioid misuse and nontherapeutic use.

METHODS

Concentration-response and noncompartmental analyses of drug liking and plasma oxycodone data from Category 3 human abuse potential studies (n = 15 to 29 per study) were conducted, using Phoenix 6.0 software. Time to onset of a set threshold of subjective effects (Tonset) and offset of subjective effects (Toffset) were estimated based on a baseline pharmacodynamic response set at 50 on a bipolar Drug Liking visual analog scale of 0-100 and the threshold for drug liking set at ≥ 65, based on study qualification criteria. Partial Area Under the Concentration (AUCTonset-Toffset) and Effect (AUETonset-Toffset) profiles were calculated and their correlation with individual partial AUE vs. partial AUC was assessed.

RESULTS

The oxycodone concentration-response (drug liking) was best described by a sigmoidal-effect Emax model (S-shaped). Using a defined threshold, drug liking was closely associated with the rate of rise in concentration and the onset of action for oxycodone administered via oral or intranasal route. Partial AUCTonset-Toffset and AUETonset-Toffset showed a strong linear correlation.

CONCLUSIONS

Results indicate that oxycodone concentration-response and duration of drug liking following manipulation via different routes of administration may be an approach for further exploring drug liking effects of opioids.

Nicotine pharmacokinetics and subjective response among adult smokers using different flavors of on!® nicotine pouches compared to combustible cigarettes

RATIONALE

on!® nicotine pouches (NPs) are oral tobacco-derived nicotine products that are tobacco-leaf free and are available in a variety of flavors and nicotine strengths. Switching completely to NPs from cigarettes may present the potential to reduce harm in adult smokers (AS) unable or unwilling to quit smoking. We characterized the abuse potential of six different flavor variants of NPs compared to cigarettes.

OBJECTIVES

The objective of this study was to evaluate the nicotine pharmacokinetics (PK) and subjective effects of different flavor variants of NPs compared to participants' own brand cigarettes (OBCs) in AS.

METHODS

In this single-blind, randomized, 7-way crossover study, we assessed nicotine PK, subjective measures (using well-established questionnaires), and product use behavior associated with six flavors of 4 mg NPs and OBCs in AS that remained in clinic for the duration of the test period.

RESULTS

Nicotine C_max values ranged from 9.0 to 11.5 ng/mL for the NPs and 16.3 ng/mL for OBCs. The t_max ranged from 30.1 to 34.9 min for ONPs and 7.5 min for OBCs. Use of NPs resulted in lower ratings of urge to smoke or craving a cigarette. All the NPs were considered pleasant, but not as much as OBCs. Flavor did not appear to influence the nicotine PK or subjective responses.

CONCLUSIONS

Based on the nicotine PK parameters and subjective responses, we conclude that NPs, regardless of flavor, likely have lower abuse potential than cigarettes. Overall, this study suggests that the NPs may be potentially acceptable switching products for adult smokers.

No Abuse Potential of Silexan in Healthy Recreational Drug Users: A Randomized Controlled Trial

BACKGROUND

Silexan is a lavender essential oil with established anxiolytic and calming efficacy. Here we asked whether there is a potential for abuse in human patients.

METHODS

We carried out a phase I abuse liability single-center, double-blind, 5-way crossover study in healthy users of recreational central nervous system depressants. They received single oral doses of 80 mg (therapeutic dose) and 640 mg Silexan, 2 mg and 4 mg lorazepam (active control) and placebo in randomized order, with 4- to 14-day washout periods between treatments. Pharmacodynamic measures included validated visual analogue scales assessing positive, negative, and sedative drug effects and balance of effects; a short form of the Addiction Research Center Inventory; and a drug similarity assessment. The primary outcome measure was the individual maximum value on the drug liking visual analogue scale during 24 hours post-dose.

RESULTS

Forty participants were randomized and 34 were evaluable for pharmacodynamic outcomes. In intraindividual head-to-head comparisons of the drug liking visual analogue scale maximum value, both doses of Silexan were rated similar to placebo whereas differences were observed between Silexan and lorazepam and between placebo and lorazepam (P < .001). These data were supported by all secondary measures of positive drug effects and of balance of effects. Differences between placebo and both doses of Silexan were always negligible in magnitude. Moreover, Silexan showed no sedative effects and was not perceived to be similar to commonly used drugs that participants had used in the past.

CONCLUSIONS

Silexan did not exhibit any abuse potential in a standard abuse potential detection screen study and is unlikely to be recreationally abused.

Randomized Crossover Trial to Compare Abuse Liability of Intravenous Remimazolam Versus Intravenous Midazolam and Placebo in Recreational Central Nervous System Depressant Users

Remimazolam (RMZ) is a new and ultra-fast-acting, short-duration intravenous benzodiazepine, a drug class associated with abuse potential. This trial was designed to compare the abuse potential of remimazolam with placebo and midazolam (MDZ), a well-characterized member of the same pharmacological class in healthy, recreational drug users 18-55 years-of-age, who demonstrated good drug tolerance and were able to discriminate between midazolam and placebo. At equipotent intravenous doses selected to produce effects ranging from mild/moderate to relatively strong sedation without loss of consciousness (RMZ: 5, 10 mg versus MDZ: 2.5, 5 mg), peak scores (E_max or E_min , respectively) for drug liking, good/bad/any effects, and sedation (drowsiness and relaxation) were significantly greater than placebo for both active drugs and were broadly comparable between RMZ and MDZ. In contrast, areas under the effect-time curves (TA_AUE) were notably lower for RMZ versus MDZ, particularly for measures of good and any effects, reflecting the shorter duration of action and consistent with the more rapid observed plasma clearance for RMZ versus MDZ and the lack of an active RMZ metabolite. Scores for willingness to take drug again were also lower for RMZ versus MDZ, but not significantly so. We concluded that the abuse potential of RMZ is comparable to or lower than that of MDZ, a drug known to have a low potential for intravenous abuse.

Assessment of an Equimolar Mixture of Oxygen and Nitrous Oxide: Effects in Pediatric Dentistry

Background

Many studies were conducted to assess the benefit/risk of equimolar mixture of oxygen and nitrous oxide (EMONO), but evaluating the appetite associated to its use is now getting very little attention in the literature. The purpose of this study was to investigate the effects present, felt, and sought during care by the child related with the 50% nitrous oxide/oxygen (EMONO) sedation used in pediatric dentistry.

Materials and methods

All patients in consultation with the Dental Service of Nantes hospital and in need of EMONO were included in the study. In this prospective single-center study, the effects present, felt, and sought during care by the child and the assessment of EMONO appreciation were recorded. The presence of clear signs that the child was trying to extend the duration of the EMONO use was also sought.

Results

Only 62% of the patients were presented with an anxiolytic effect, and 40% relative analgesia. Both effects were associated in 33% of children. Over the 76 patients assessed, 12 attempted to extend the duration of the EMONO use (16%). After a bivariate statistical analysis, none of the variables appeared significantly associated with the extension of the EMONO use duration.

Conclusion

The significant proportion of patients who have prolonged the EMONO use seems to indicate a real attraction for nitrous oxide. This is the first study to evaluate nitrous oxide appreciation on a child.

How to cite this article

Prud’homme T, Allio A, Dajean-Trutaud S, et al. Assessment of an Equimolar Mixture of Oxygen and Nitrous Oxide: Effects in Pediatric Dentistry. Int J Clin Pediatr Dent 2019;12(5):429–436.

Potential for limited reinforcing and abuse-related subjective effects of intranasal oxytocin

BACKGROUND

There has been growing interest in using oxytocin as a pharmacotherapy for psychiatric disorders, including substance use disorder. Limited data exist regarding oxytocin's reinforcing efficacy, which is a necessary consideration for novel pharmacotherapies, especially in substance-using populations.

AIMS

This study aimed to determine the potential reinforcing effects of intranasally administered oxytocin by assessing behavioral economic demand and subjective effects.

METHODS

Healthy adults (n = 23) participated in a double-blind, repeated-measures, laboratory study wherein they received intranasal oxytocin (40 IU) or placebo in a randomized order across two sessions. Participants completed drug purchasing tasks at the conclusion of both sessions. Throughout both sessions, subjective and physiological effects were assessed.

RESULTS

Demand-curve analysis of purchasing tasks revealed greater median purchasing for oxytocin relative to placebo. Physiological and subjective effects did not significantly differ between oxytocin and placebo. However, a nonsignificant trend was observed for moderately greater drug liking for oxytocin relative to placebo. There was a significant, positive correlation between the difference in drug liking (between oxytocin and placebo) and the difference in lowest-price purchasing (between oxytocin and placebo).

CONCLUSIONS

These data suggest the potential for limited reinforcing and abuse-related subjective effects of intranasal oxytocin. Given the small sample, the greater drug liking of oxytocin compared to placebo, and the positive relation between demand and drug liking, it is possible that oxytocin may produce reinforcing effects in some participants. Therefore, additional studies of oxytocin reinforcement are warranted.

Abuse Potential of Lasmiditan: A Phase 1 Randomized, Placebo- and Alprazolam-Controlled Crossover Study

Lasmiditan is a centrally penetrant, highly selective 5‐hydroxytryptamine (serotonin) receptor 1F (5HT_1F) agonist under development as a novel therapy for acute treatment of migraine. A phase 1 randomized, placebo‐ and positive‐controlled crossover study assessed the abuse potential of lasmiditan in adult recreational polydrug users. Following a qualification phase, subjects were randomized into treatment sequences, each consisting of 5 study treatments: placebo, alprazolam 2 mg, lasmiditan 100, 200 (lasmiditan 100 and 200 mg are proposed therapeutic doses), and 400 mg (supratherapeutic). The abuse potential of lasmiditan was investigated and compared with alprazolam and with placebo using the maximal effect score (E_max) of the Drug‐Liking Visual Analog Scale as the primary end point. Lasmiditan was not similar to placebo in drug‐liking scores at all doses tested, with a maximum difference observed with the lasmiditan 400‐mg dose (upper 90% confidence limit on difference in least‐squares [LS] means > 14 for all lasmiditan doses). Drug‐liking scores for lasmiditan 400 mg were not significantly different from alprazolam (lower 90% confidence limit on difference in LS means < 5), but drug‐liking scores at lower doses (100 and 200 mg) were significantly different from alprazolam. During the treatment phase, the incidence of treatment‐emergent adverse events (TEAEs) increased with increasing dose of lasmiditan; all TEAEs reported with lasmiditan treatment were mild. Subjective drug‐liking effects for lasmiditan versus placebo and versus alprazolam, and the safety and tolerability profile of lasmiditan suggest that lasmiditan has a low potential for abuse.

The association between endogenous opioid function and morphine responsiveness: a moderating role for endocannabinoids

We sought to replicate previous findings that low endogenous opioid (EO) function predicts greater morphine analgesia and extended these findings by examining whether circulating endocannabinoids and related lipids moderate EO-related predictive effects. Individuals with chronic low-back pain (n = 46) provided blood samples for endocannabinoid analyses, then underwent separate identical laboratory sessions under 3 drug conditions: saline placebo, intravenous (i.v.) naloxone (opioid antagonist; 12-mg total), and i.v. morphine (0.09-mg/kg total). During each session, participants rated low-back pain intensity, evoked heat pain intensity, and nonpain subjective effects 4 times in sequence after incremental drug dosing. Mean morphine effects (morphine-placebo difference) and opioid blockade effects (naloxone-placebo difference; to index EO function) for each primary outcome (low-back pain intensity, evoked heat pain intensity, and nonpain subjective effects) were derived by averaging across the 4 incremental doses. The association between EO function and morphine-induced back pain relief was significantly moderated by endocannabinoids [2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA)]. Lower EO function predicted greater morphine analgesia only for those with relatively lower endocannabinoids. Endocannabinoids also significantly moderated EO effects on morphine-related changes in visual analog scale-evoked pain intensity (2-AG), drug liking (AEA and 2-AG), and desire to take again (AEA and 2-AG). In the absence of significant interactions, lower EO function predicted significantly greater morphine analgesia (as in past work) and euphoria. Results indicate that EO effects on analgesic and subjective responses to opioid medications are greatest when endocannabinoid levels are low. These findings may help guide development of mechanism-based predictors for personalized pain medicine algorithms.

Abuse potential of mirogabalin in recreational polydrug users

Mirogabalin is a selective calcium channel α₂δ subunit ligand being developed to treat neuropathic pain. In accordance with US Food and Drug Administration (FDA) guidance, the human abuse potential of mirogabalin (15–105 mg) was examined, relative to placebo, diazepam (15 or 30 mg), and pregabalin (200 or 450 mg), in two single-dose, randomized, double-blind, placebo- and active-controlled crossover studies in recreational polydrug users who could discern between positive comparator and placebo. The primary endpoint was maximum observed effect (E_max) for Drug Liking Visual Analog Scale. At therapeutic doses, mirogabalin Drug Liking E_max did not differ significantly from placebo and was significantly lower than diazepam and pregabalin. This indicates therapeutic doses mirogabalin may have less abuse potential versus diazepam or pregabalin. At supratherapeutic doses (⩾4× therapeutic dose), mirogabalin had significantly higher Drug Liking E_max than placebo, but lower E_max than pregabalin. In both studies, therapeutic doses of mirogabalin demonstrated limited evidence of abuse potential.

Human Abuse Potential of the New Opioid Analgesic Molecule NKTR-181 Compared with Oxycodone

Objective

Evaluate the human abuse potential, pharmacokinetics, pharmacodynamics, and safety of NKTR-181, a novel mu-opioid agonist molecule, relative to oxycodone.

Design

This randomized, single-center, double-blind, active- and placebo-controlled five-period crossover study enrolled healthy, adult, non–physically dependent recreational opioid users.

Setting

Inpatient clinical research site.

Subjects

Forty-two randomized subjects (73.8% male, 81% white, mean age = 25 years).

Methods

The primary objective was to evaluate single orally administered 100, 200, and 400 mg NKTR-181 doses in solution compared with 40 mg oxycodone and placebo solutions using the Drug Liking visual analog scale. Secondary measures included the Drug Effects Questionnaire, Addiction Research Center Inventory/Morphine Benzedrine Group Subscale, Price Value Assessment Questionnaire, Global Assessment of Overall Drug Liking, and Take Drug Again Assessment. Central nervous system mu-opioid effects were assessed using pupillometry. The study included qualifying and treatment phases. Subjects received each of the five treatments using a crossover design.

Results

NKTR-181 at all dose levels had significantly lower Drug Liking E_max than oxycodone (P < 0.0001). Drug Liking scores for oxycodone increased rapidly within 15 minutes and peaked at approximately one hour postdose, whereas Drug Liking (and most secondary abuse potential measures) for all doses of NKTR-181 were comparable with placebo for at least the first hour. Only the 400 mg Drug Liking scores were minimally differentiated vs placebo from one and a half to four hours, but remained significantly lower than oxycodone (P < 0.003). NKTR-181 treatment-related adverse effects were mild and occurred at a lower rate compared with oxycodone.

Conclusions

NKTR-181 demonstrated delayed onset of CNS effects and significantly lower abuse potential scores compared with oxycodone in recreational opioid users.

The MEOPAeDent trial protocol-an observational study of the Equimolar Mixture of Oxygen and Nitrous Oxide (EMONO) effects in paediatric dentistry

BACKGROUND

Many studies were conducted to assess the benefit/risk ratio of EMONO (Equimolar Mixture of Oxygen and Nitrous Oxide) in France before it was authorized for use outside the hospital setting in 2009. The main objective of this project is to evaluate the effects sought and felt by children when EMONO is used in paediatric dentistry. The secondary objectives are to (i) evaluate the appreciation of EMONO by the children, (ii) characterize children who experience both analgesia and anxiolysis, (iii) evaluate children's appetite for EMONO and characterize children with a high appetite and (iv) evaluate the impact of the difference in practice among the French dental service university hospitals on anxiety. The maintenance of a framework for the safe use of this drug, whose place in dental care is fundamental, is essential. Twelve of the 16 French dental service university hospitals agreed to participate in this study.

METHODS

MEOPAeDent is an observational, descriptive, transversal study that aims to evaluate the effects sought and felt by children when EMONO is used in paediatric dentistry. Subjects requiring dental care under EMONO are recruited by 12 French dental service university hospitals. Patients aged from 3 to 15 years are recruited for the study when they visit a dental service of a French university hospital requiring dental care under EMONO. The investigator collects the necessary data from the child's medical records, from his own observations and from questions posed to the child and his/her parents. A survey is completed at the first and final sessions of dental care under EMONO.

DISCUSSION

This study will provide an evaluation of the effects of EMONO on the French paediatric population in need of dental care as well as evaluate the appetite for the use of this substance. The results will first be used to provide additional data that is essential to monitor the use of a product with an authorization to use it outside of hospitals from 2009 in France, confirm its safety for use and justify its framework of application.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03453411 registered 2 March 2018.

Assessment of the Abuse Potential of Cebranopadol in Nondependent Recreational Opioid Users: A Phase 1 Randomized Controlled Study

BACKGROUND

Cebranopadol is a nociceptin/orphanin FQ peptide/opioid receptor agonist with central antinociceptive activity. We hypothesize that this novel mechanism of action may lead to a lower risk of abuse compared with pure μ-opioid peptide receptor agonists.

METHODS

We conducted a single-dose, nested-randomized, double-blind crossover study in nondependent recreational opioid users to evaluate the abuse potential of single doses of cebranopadol relative to hydromorphone immediate release and placebo. The study consisted of a qualification phase and a 7-period treatment phase (cebranopadol 200, 400, and 800 μg; hydromorphone 8 and 16 mg; and 2 placebos). The primary end point was the peak effect of drug liking at this moment, measured by visual analog scale (VAS). Various secondary end points (eg, VAS rating for good drug effects, high, bad drug effects, take drug again, drug similarity, and pupillometry) were also investigated.

RESULTS

Forty-two subjects completed the study. Cebranopadol 200 and 400 μg did not differentiate from placebo on the abuse potential assessments and generated smaller responses than hydromorphone. Responses observed with cebranopadol 800 μg were similar to hydromorphone 8 mg and smaller than hydromorphone 16 mg. The maximum effect for VAS drug liking at this moment was delayed compared with hydromorphone (3 and 1.5 hours, respectively). Cebranopadol administration was safe; no serious adverse events or study discontinuation due to treatment-emergent adverse events occurred.

CONCLUSIONS

These results confirm our hypothesis that cebranopadol, a nociceptin/orphanin FQ peptide/opioid receptor agonist, has lower abuse potential than hydromorphone immediate release, a pure μ-opioid peptide agonist.

Self-reported cumulative medical opioid exposure and subjective responses on first use of opioids predict analgesic and subjective responses to placebo-controlled opioid administration

BACKGROUND AND OBJECTIVES

To expand the evidence base needed to enable personalized pain medicine, we evaluated whether self-reported cumulative exposure to medical opioids and subjective responses on first opioid use predicted responses to placebo-controlled opioid administration.

METHODS

In study 1, a survey assessing cumulative medical opioid exposure and subjective responses on first opioid use was created (History of Opioid Medical Exposure (HOME)) and psychometric features documented in a general sample of 307 working adults. In study 2, 49 patients with chronic low back pain completed the HOME and subsequently rated back pain intensity and subjective opioid effects four times after receiving saline placebo or intravenous morphine (four incremental doses) in two separate double-blinded laboratory sessions. Placebo-controlled morphine effects were derived for all outcomes.

RESULTS

Two HOME subscales were supported: cumulative opioid exposure and euphoric response, both demonstrating high test-retest reliability (Intraclass Correlation Coefficients > 0.93) and adequate internal consistency (Revelle's Omega Total = 0.73-0.77). In study 2, higher cumulative opioid exposure scores were associated with significantly greater morphine-related reductions in back pain intensity (p=0.02), but not with subjective drug effects. Higher euphoric response subscale scores were associated with significantly lower overall perceived morphine effect (p=0.003), less sedation (p=0.04), greater euphoria (p=0.03) and greater desire to take morphine again (p=0.02).

DISCUSSION

Self-reports of past exposure and responses to medical opioid analgesics may have utility for predicting subsequent analgesic responses and subjective effects. Further research is needed to establish the potential clinical and research utility of the HOME.

TRIAL REGISTRATION NUMBER

NCT02469077.

Fentanyl: Receptor pharmacology, abuse potential, and implications for treatment

Opioid overdoses, many of which are attributed to use of illicit fentanyl, are currently one of the leading causes of death in the U.S. Although fentanyl has been used safely for decades in clinical settings, the widespread use of illicit fentanyl is a recent phenomenon. Starting in 2013, illicitly manufactured fentanyl and its analogs began to appear on the streets. These substances were added to or sold as heroin, often unbeknownst to the user. Because fentanyl is so potent, only small amounts are needed to produce pharmacological effects, but the margin between safe and toxic doses is narrow. Surprisingly little is known about the exact signaling mechanisms underlying fentanyl-related respiratory depression or the effectiveness of naloxone in reversing this effect. Similarly, little is known about the ability of treatment medications such as buprenorphine, methadone, or naltrexone to reduce illicit fentanyl use. The present article reviews the receptor, preclinical and clinical pharmacology of fentanyl, and how its pharmacology may predict the effectiveness of currently approved medications for treating illicit fentanyl use.

A randomized, double-blind, placebo-controlled, crossover study to evaluate the human abuse liability of solriamfetol, a selective dopamine and norepinephrine reuptake inhibitor

BACKGROUND

This study evaluated the human abuse potential of solriamfetol (formerly JZP-110), a selective dopamine and norepinephrine reuptake inhibitor with robust wake-promoting effects.

METHODS

Adults with a recent history of recreational polydrug use, including stimulants, and who met criteria in a Qualification Phase were randomized to one of six sequences in a Test Phase. Each Test Phase sequence included a single administration of placebo, solriamfetol (300, 600, and 1200 mg), and phentermine (45 and 90 mg), with a two-day washout between periods. The primary endpoint was peak rating ( Emax) of Liking at the Moment across the first 12 h on a liking/disliking visual analog scale; key secondary endpoints were Next Day Overall Drug Liking, how much the participant would like to Take the Drug Again, and positive and negative subjective effects. Safety was also assessed throughout the study.

RESULTS

Of 43 participants (74.4% male; mean age 29.3 years), 37 completed the study. Peak Emax Liking at the Moment for all solriamfetol doses was significantly greater than placebo and significantly less than phentermine 90 mg ( p < 0.05). Overall Next Day Drug Liking was greater than placebo for solriamfetol 300 mg and phentermine 45 and 90 mg ( p < 0.05). Willingness to Take the Drug Again was significantly greater than placebo and significantly less than both doses of phentermine for all doses of solriamfetol ( p < 0.05). Ratings of negative subjective effects (bad effects, disliking, anxiety, agitation) were higher with solriamfetol 600 and 1200 mg relative to phentermine. The most common treatment-emergent adverse events with solriamfetol were hypervigilance, elevated mood, dry mouth, hyperhidrosis, and insomnia.

CONCLUSION

Solriamfetol appears to have abuse potential similar to or lower than phentermine.

Abuse potential assessment of cannabidiol (CBD) in recreational polydrug users: A randomized, double-blind, controlled trial

RATIONALE

Treatment with a highly purified oral solution of cannabidiol (CBD), derived from the plant Cannabis sativa L., demonstrated some evidence of central nervous system (CNS)-related adverse events in patients enrolled in phase 3 trials for treatment of childhood-onset epilepsy. Cannabidiol was categorized as a Schedule 1 substance by the United States Drug Enforcement Administration; therefore, it was important to test CBD for human abuse potential.

METHODS

This was a single-dose, randomized, double-blind, double-dummy, placebo- and active-controlled crossover trial. The abuse potential of single oral doses of plant-derived pharmaceutical formulations of highly purified CBD (Epidiolex®; 750 mg, 1500 mg, and 4500 mg) was compared with that of single oral doses of alprazolam (2 mg), dronabinol (10 mg and 30 mg), and placebo in healthy recreational polydrug users. The primary endpoint to assess abuse potential was the maximum effect (E_max) on Drug-Liking visual analog scale (VAS). Other measurements included E_max on Overall Drug-Liking VAS, Take Drug Again VAS, positive and negative effects, other subjective effects, and Drug Similarity VAS. Cognitive and psychomotor functions were assessed using the Divided Attention Test, the Hopkins Verbal Learning Test-Revised, and the Digit-Symbol Substitution Task. Pharmacokinetic parameters were determined for CBD and its major metabolites. Standard safety measures and adverse events were assessed.

PRINCIPAL RESULTS

Of 95 eligible subjects, 43 qualified for the treatment phase, received at least 1 dose of investigational medicinal product, and were included in safety assessments; 35 subjects were included in the pharmacodynamic analysis. Subjects receiving alprazolam and dronabinol had significantly higher Drug-Liking E_max (P < 0.0001) compared with those receiving placebo, confirming study validity. Compared with placebo, Drug-Liking was not significantly different for subjects taking 750-mg CBD (P = 0.51). Drug-Liking E_max values for 1500-mg and 4500-mg CBD were significantly different from placebo (P = 0.04 and 0.002, respectively); however, the mean differences were <10 points on VAS compared with >18-point differences between positive controls and placebo. Alprazolam and dronabinol had significantly higher Drug-Liking, Overall-Liking, and Take Drug Again VAS E_max values compared with all doses of CBD (P ≤ 0.004). In contrast to alprazolam, CBD administration had no observable effect on cognitive/psychomotor tests. Pharmacokinetic parameters for CBD in this trial were consistent with previous studies. The majority of adverse events reported during the trial were of mild or moderate severity; no serious adverse events or deaths were reported.

CONCLUSION

Administration of a therapeutic dose of CBD (750 mg) showed significantly low abuse potential in a highly sensitive population of polydrug users. Although high and supratherapeutic doses of CBD (1500 mg and 4500 mg, respectively) had detectable subjective effects compared with placebo; the effects were significantly lower than those observed with alprazolam and dronabinol.

The abuse potential of medical psilocybin according to the 8 factors of the Controlled Substances Act

This review assesses the abuse potential of medically-administered psilocybin, following the structure of the 8 factors of the US Controlled Substances Act (CSA). Research suggests the potential safety and efficacy of psilocybin in treating cancer-related psychiatric distress and substance use disorders, setting the occasion for this review. A more extensive assessment of abuse potential according to an 8-factor analysis would eventually be required to guide appropriate schedule placement. Psilocybin, like other 5-HT2A agonist classic psychedelics, has limited reinforcing effects, supporting marginal, transient non-human self-administration. Nonetheless, mushrooms with variable psilocybin content are used illicitly, with a few lifetime use occasions being normative among users. Potential harms include dangerous behavior in unprepared, unsupervised users, and exacerbation of mental illness in those with or predisposed to psychotic disorders. However, scope of use and associated harms are low compared to prototypical abused drugs, and the medical model addresses these concerns with dose control, patient screening, preparation and follow-up, and session supervision in a medical facility. CONCLUSIONS: (1) psilocybin has an abuse potential appropriate for CSA scheduling if approved as medicine; (2) psilocybin can provide therapeutic benefits that may support the development of an approvable New Drug Application (NDA) but further studies are required which this review describes; (3) adverse effects of medical psilocybin are manageable when administered according to risk management approaches; and (4) although further study is required, this review suggests that placement in Schedule IV may be appropriate if a psilocybin-containing medicine is approved. This article is part of the Special Issue entitled 'Psychedelics: New Doors, Altered Perceptions'.

Reduced Nicotine Content Cigarettes and Cannabis Use in Vulnerable Populations

Objective: We estimated whether recent cannabis use moderates response to cigarettes varying in nicotine content (0.4, 2.4, 5.2, 15.8 mg/g) among smokers with concurrent affective disorders, opioid dependence, or socioeconomic disadvantage. Methods: We conducted a secondary analysis of a multi-site, double-blind, laboratory study examining acute response to reduced nicotine content cigarettes (RNCC) in 169 adult smokers with co-morbid conditions. Participants positive for recent cannabis use or self-reported past 30-day cannabis use at baseline were categorized as current cannabis users (N = 63). Repeated measures analysis of variance tests assessed whether baseline cannabis use moderated cigarette reinforcement, tobacco withdrawal, craving, smoking topography, or carbon monoxide boost. Results: Cannabis users were younger, less educated, and had more depression and anxiety than non-users (p < .05). Cannabis use status did not moderate the effects of nicotine dose on concurrent choice testing, subjective effects of RNCCs, or smoking topography. After adjusting for sociodemographic characteristics, cannabis users had higher ratings on Smoking Satisfaction, Enjoyment of Respiratory Tract Sensations, and Craving Reduction across all nicotine doses. Cannabis users reported longer withdrawal symptom duration and more rapid decline of carbon monoxide boost than non-users. Conclusions: Findings suggest RNCCs decrease the addiction potential of cigarettes in vulnerable populations independent of cannabis use status.

Human abuse potential of brivaracetam in healthy recreational central nervous system depressant users

BACKGROUND

Brivaracetam is a new antiepileptic drug indicated for adjunctive treatment of focal seizures in adults at a dose of 50-200mg/day taken in two equal doses. The objective of this study was to evaluate the abuse potential of brivaracetam compared with alprazolam (positive control), placebo, and levetiracetam.

METHODS

This was a randomized, double-blind, triple-dummy, crossover study in healthy male and female recreational central nervous system (CNS) depressant users aged 18-55years, who could distinguish between the subjective effects of alprazolam 2mg and placebo. All participants received single doses of brivaracetam (50 [therapeutic dose], 200, 1000mg [supratherapeutic doses]), alprazolam (1.5, 3mg), placebo, and levetiracetam (4000mg) in random order each separated by 7-10days. Subjective Visual Analogue Scales (VAS) and Addiction Research Center Inventory (ARCI) scales were completed at intervals up to 24h postdose. Primary endpoints were Drug Liking (at this moment) VAS, Overall Drug Liking VAS, Feeling High VAS, and ARCI Pentobarbital Chlorpromazine Alcohol Group (PCAG, sedation) maximum effect (E_max). Maximum effect values on each scale were analyzed using a mixed-effect model (per protocol population, N=44).

RESULTS

The maximum effect for both alprazolam doses was significantly greater versus placebo for six designated endpoints, confirming study validity. Drug Liking (at this moment) VAS E_max was significantly lower for brivaracetam 50mg than alprazolam (both doses); there were no significant differences between brivaracetam 200mg and alprazolam (both doses), and brivaracetam 1000mg and alprazolam 1.5mg. Brivaracetam 1000mg (supratherapeutic single dose) had significantly higher Drug Liking (at this moment) VAS E_max than alprazolam 3mg. Overall, Drug Liking VAS E_max for brivaracetam 50 and 200mg was not significantly different from alprazolam (both doses). Brivaracetam 1000mg had significantly higher Overall Drug Liking VAS E_max than alprazolam 1.5mg, but was not significantly different from alprazolam 3mg. Feeling High VAS E_max was lower versus alprazolam with brivaracetam 50 and 200mg, while brivaracetam 1000mg was comparable with alprazolam (both doses). Addiction Research Center Inventory PCAG E_max for brivaracetam (all doses) was significantly lower than alprazolam (both doses). On the secondary/supportive endpoints, compared with alprazolam, brivaracetam had fewer positive effects (ARCI Morphine Benzedrine Group [euphoria]; Good Drug Effects VAS [50mg]) and fewer negative effects (Bad Drug Effects VAS; ARCI Lysergic Acid Diethylamide [dysphoria]). Brivaracetam was not significantly different from alprazolam for Take Drug Again VAS (50, 200mg). For most endpoints, brivaracetam (50-200mg) was not significantly different from levetiracetam (4000mg).

CONCLUSION

This study in healthy recreational CNS depressant users showed that single doses of brivaracetam 50mg (therapeutic single dose) had lower sedative, positive, and negative drug effects than alprazolam, while brivaracetam 200 and 1000mg (supratherapeutic single doses) were more similar to alprazolam. The subjective profile of brivaracetam appeared to be similar to that of levetiracetam, but further evaluation using a range of levetiracetam doses would be needed to confirm similar abuse potential.

When adverse effects are seen as desirable: Abuse potential of the newer generation antiepileptic drugs

There has been growing recognition of the possible abuse potential of newer generation antiepileptic drugs, and several of these agents have been categorized as controlled substances in the United States. To properly schedule a new medication, the abuse potential, or the potential for a drug to be used for its nonmedical positive subjective effects, must be determined. Performing a human abuse potential study is one step in the overall abuse potential assessment. These studies analyze the abuse potential of a new drug in a very specific population of known recreational drug users. Studying the test drug in this population enables a more meaningful assessment of abuse, and likely represents the population most probable to abuse. In these double-blind, single-dose, active and placebo controlled studies subjects may report their subjective liking, estimated street value, and rate euphoric or depressive sensations of the test drug compared with placebo and scheduled active comparators with a known abuse potential. In order to provide an enhanced understanding of the abuse potential assessment and how it relates to controlled substance scheduling, this review will examine the human abuse potential studies of perampanel, eslicarbazepine, lacosamide, and brivaracetam.

A regulatory perspective on the evaluation of hallucinogen drugs for human use

In recent years, there is renewed interest in the study of various hallucinogens for their potential therapeutic effects. In the United States of America (USA), the abuse potential assessment of a drug is carried out as part of the general safety and efficacy evaluation of a drug. Additionally, the abuse potential assessment is taken under consideration in determining if a drug needs to be subject to controls to minimize the abuse of the drug once on the market. This assessment is conducted for all new drugs with central nervous system (CNS) activity, that are chemically or pharmacologically similar to other drugs with known abuse potential, or drugs that produce psychoactive effects predictive of abuse, such as euphoria and hallucinations. This paper describes the regulatory framework for evaluating the abuse potential of new drugs, with emphasis on hallucinogens. The paper discusses the role of the United States Food and Drug Administration (FDA) in the evaluation of the abuse potential of drugs and its role in drug control, and provides an overview of the controlled status of hallucinogens and the requirements to conduct research with Schedule I substances in the USA. This article is part of the Special Issue entitled 'Psychedelics: New Doors, Altered Perceptions'.

Addiction Potential of Cigarettes With Reduced Nicotine Content in Populations With Psychiatric Disorders and Other Vulnerabilities to Tobacco Addiction

IMPORTANCE

A national policy is under consideration to reduce the nicotine content of cigarettes to lower nicotine addiction potential in the United States.

OBJECTIVE

To examine how smokers with psychiatric disorders and other vulnerabilities to tobacco addiction respond to cigarettes with reduced nicotine content.

DESIGN, SETTING, AND PARTICIPANTS

A multisite, double-blind, within-participant assessment of acute response to research cigarettes with nicotine content ranging from levels below a hypothesized addiction threshold to those representative of commercial cigarettes (0.4, 2.3, 5.2, and 15.8 mg/g of tobacco) at 3 academic sites included 169 daily smokers from the following 3 vulnerable populations: individuals with affective disorders (n = 56) or opioid dependence (n = 60) and socioeconomically disadvantaged women (n = 53). Data were collected from March 23, 2015, through April 25, 2016.

INTERVENTIONS

After a brief smoking abstinence, participants were exposed to the cigarettes with varying nicotine doses across fourteen 2- to 4-hour outpatient sessions.

MAIN OUTCOMES AND MEASURES

Addiction potential of the cigarettes was assessed using concurrent choice testing, the Cigarette Purchase Task (CPT), and validated measures of subjective effects, such as the Minnesota Nicotine Withdrawal Scale.

RESULTS

Among the 169 daily smokers included in the analysis (120 women [71.0%] and 49 men [29.0%]; mean [SD] age, 35.6 [11.4] years), reducing the nicotine content of cigarettes decreased the relative reinforcing effects of smoking in all 3 populations. Across populations, the 0.4-mg/g dose was chosen significantly less than the 15.8-mg/g dose in concurrent choice testing (mean [SEM] 30% [0.04%] vs 70% [0.04%]; Cohen d = 0.40; P < .001) and generated lower demand in the CPT (α = .027 [95% CI, 0.023-0.031] vs α = .019 [95% CI, 0.016-0.022]; Cohen d = 1.17; P < .001). Preference for higher over lower nicotine content cigarettes could be reversed by increasing the response cost necessary to obtain the higher dose (mean [SEM], 61% [0.02%] vs 39% [0.02%]; Cohen d = 0.40; P < .001). All doses reduced Minnesota Nicotine Withdrawal Scale total scores (range of mean decreases, 0.10-0.50; Cohen d range, 0.21-1.05; P < .001 for all), although duration of withdrawal symptoms was greater at higher doses (η2 = 0.008; dose-by-time interaction, P = .002).

CONCLUSIONS AND RELEVANCE

Reducing the nicotine content of cigarettes may decrease their addiction potential in populations that are highly vulnerable to tobacco addiction. Smokers with psychiatric conditions and socioeconomic disadvantage are more addicted and less likely to quit and experience greater adverse health impacts. Policies to reduce these disparities are needed; reducing the nicotine content in cigarettes should be a policy focus.

Foods are differentially associated with subjective effect report questions of abuse liability

OBJECTIVES

The current study investigates which foods may be most implicated in addictive-like eating by examining how nutritionally diverse foods relate to loss of control consumption and various subjective effect reports. Subjective effect reports assess the abuse liabilities of substances and may similarly provide insight into which foods may be reinforcing in a manner that triggers an addictive-like response for some individuals.

DESIGN

Cross-sectional.

SETTING

Online community.

PARTICIPANTS

507 participants (n = 501 used in analyses) recruited through Amazon MTurk.

MEASUREMENTS

Participants (n = 501) self-reported how likely they were to experience a loss of control over their consumption of 30 nutritionally diverse foods and rated each food on five subjective effect report questions that assess the abuse liability of substances (liking, pleasure, craving, averseness, intensity). Hierarchical cluster analytic techniques were used to examine how foods grouped together based on each question.

RESULTS

Highly processed foods, with added fats and/or refined carbohydrates, clustered together and were associated with greater loss of control, liking, pleasure, and craving. The clusters yielded from the subjective effect reports assessing liking, pleasure, and craving were most similar to clusters formed based on loss of control over consumption, whereas the clusters yielded from averseness and intensity did not meaningfully differentiate food items.

CONCLUSION

The present work applies methodology used to assess the abuse liability of substances to understand whether foods may vary in their potential to be associated with addictive-like consumption. Highly processed foods (e.g., pizza, chocolate) appear to be most related to an indicator of addictive-like eating (loss of control) and several subjective effect reports (liking, pleasure, craving). Thus, these foods may be particularly reinforcing and capable of triggering an addictive-like response in some individuals. Future research is warranted to understand whether highly processed foods are related to these indicators of abuse liability at a similar magnitude as addictive substances.

Evaluation of the "Pipeline" for Development of Medications for Cocaine Use Disorder: A Review of Translational Preclinical, Human Laboratory, and Clinical Trial Research

Cocaine use disorder is a persistent public health problem for which no widely effective medications exist. Self-administration procedures, which have shown good predictive validity in estimating the abuse potential of drugs, have been used in rodent, nonhuman primate, and human laboratory studies to screen putative medications. This review assessed the effectiveness of the medications development process regarding pharmacotherapies for cocaine use disorder. The primary objective was to determine whether data from animal and human laboratory self-administration studies predicted the results of clinical trials. In addition, the concordance between laboratory studies in animals and humans was assessed. More than 100 blinded, randomized, fully placebo-controlled studies of putative medications for cocaine use disorder were identified. Of the 64 drugs tested in these trials, only 10 had been examined in both human and well-controlled animal laboratory studies. Within all three stages, few studies had been conducted for each drug and when multiple studies had been conducted conclusions were sometimes contradictory. Overall, however, there was good concordance between animal and human laboratory results when the former assessed chronic drug treatment. Although only seven of the ten reviewed drugs showed fully concordant results across all three types of studies reviewed, the analysis revealed several subject-related, procedural, and environmental factors that differ between the laboratory and clinical trial settings that help explain the disagreement for other drugs. The review closes with several recommendations to enhance translation and communication across stages of the medications development process that will ultimately speed the progress toward effective pharmacotherapeutic strategies for cocaine use disorder.

Inhalation of Alcohol Vapor: Measurement and Implications

Decades of alcohol research have established the health risks and pharmacodynamic profile of oral alcohol consumption. Despite isolated periods of public health concern, comparatively less research has evaluated exposure to alcohol vapor. Inhaled alcohol initially bypasses first-pass metabolism and rapidly reaches the arterial circulation and the brain, suggesting that this route of administration may be associated with pharmacological effects that increase the risk of addiction. However, detailed reviews assessing the possible effects of inhaled alcohol in humans are lacking. A comprehensive, systematic literature review was conducted using Google Scholar and PubMed to examine manuscripts studying exposure to inhaled alcohol and measurement of biomarkers (biochemical or functional) associated with alcohol consumption in human participants. Twenty-one publications reported on alcohol inhalation. Fourteen studies examined inhalation of alcohol vapor associated with occupational exposure (e.g., hand sanitizer) in a variety of settings (e.g., naturalistic, laboratory). Six publications measured inhalation of alcohol in a controlled laboratory chamber, and 1 evaluated direct inhalation of an e-cigarette with ethanol-containing "e-liquid." Some studies have reported that inhalation of alcohol vapor results in measurable biomarkers of acute alcohol exposure, most notably ethyl glucuronide. Despite the lack of significantly elevated blood alcohol concentrations, the behavioral consequences and subjective effects associated with repeated use of devices capable of delivering alcohol vapor are yet to be determined. No studies have focused on vulnerable populations, such as adolescents or individuals with alcohol use disorder, who may be most at risk of problems associated with alcohol inhalation.

Oral Human Abuse Potential of Oxycodone DETERx® (Xtampza® ER)

Oxycodone DETERx^® (Collegium Pharmaceutical Inc, Canton, Massachusetts) is an extended‐release, microsphere‐in‐capsule, abuse‐deterrent formulation designed to retain its extended‐release properties after tampering (eg, chewing/crushing). This randomized, double‐blind, placebo‐controlled, triple‐dummy study evaluated the oral abuse potential of intact and chewed oxycodone DETERx capsules compared with crushed immediate‐release oxycodone. Subjects with a history of recreational opioid use who were nondependent/nontolerant to opioids were enrolled. Treatments included intact oxycodone DETERx (high‐fat, high‐calorie meal and fasted), chewed oxycodone DETERx (high‐fat, high‐calorie meal and fasted), crushed immediate‐release oxycodone (fasted), and placebo (high‐fat, high‐calorie meal). Plasma samples were collected to determine pharmacokinetic parameters. The primary endpoint was drug liking at the moment; other endpoints included drug effects questionnaire scores, Addiction Research Center Inventory/Morphine Benzedrine Group score, pupillometry measurements, and safety. Thirty‐eight subjects completed the study. Chewed and intact oxycodone DETERx were bioequivalent, unlike crushed immediate‐release oxycodone, which yielded higher peak oxycodone plasma concentrations compared with all methods of oxycodone DETERx administration. The mean maximum (peak) effect (E_max) for drug liking was significantly lower for chewed and intact oxycodone DETERx than for crushed immediate‐release oxycodone (P < .01). The time to E_max was significantly longer for chewed and intact oxycodone DETERx than for crushed immediate‐release oxycodone (P < .0001). Scores for feeling high and Addiction Research Center Inventory/Morphine Benzedrine Group scores demonstrated lower abuse potential for chewed and intact oxycodone DETERx compared with crushed immediate‐release oxycodone. Study treatments were well tolerated; no subjects experienced serious adverse events. These results demonstrate the lower oral abuse potential of chewed and intact oxycodone DETERx than crushed immediate‐release oxycodone.

Assessment of the Abuse Potential of the Orexin Receptor Antagonist, Suvorexant, Compared With Zolpidem in a Randomized Crossover Study

Suvorexant is a dual orexin receptor antagonist approved in the United States and Japan for the treatment of insomnia at a maximum dose of 20 mg. This randomized double-blind crossover study evaluated the abuse potential of suvorexant in 36 healthy recreational polydrug users with a history of sedative and psychedelic drug use. Single doses of suvorexant (40, 80, and 150 mg: 2-7.5 × maximum dose), zolpidem (15 and 30 mg: 1.5-3 × maximum dose), and placebo were administered, with a 10-day washout between treatments. Subjective and objective measures, including visual analog scales (VASs), Addiction Research Center Inventory, and cognitive/psychomotor tests, were evaluated for 24-hour postdose. Suvorexant had significantly greater peak effects on "drug liking" VAS (primary endpoint) than placebo. Although effects of suvorexant on abuse potential measures were generally similar to zolpidem, they remained constant across doses, whereas zolpidem often had greater effects at higher doses. Suvorexant (all doses) had significantly fewer effects than zolpidem 30 mg on secondary measures, such as "high" VAS, Bowdle VAS, and Addiction Research Center Inventory morphine-benzedrine group. The overall incidence of abuse-related adverse events, such as euphoric mood and hallucination, was numerically lower with suvorexant than zolpidem. In agreement with its classification as a schedule IV drug, suvorexant demonstrated abuse potential, compared with placebo. The abuse potential was similar to zolpidem using certain measures, but with a reduced incidence of abuse-related adverse events. Although this suggests that the overall abuse liability of suvorexant may be lower than zolpidem, the actual abuse rates will be assessed with the postmarketing experience.

Abuse liability assessment of eslicarbazepine acetate in healthy male and female recreational sedative users: A Phase I randomized controlled trial

RATIONALE

Eslicarbazepine acetate (ESL) is a once-daily oral antiepileptic drug for the treatment of partial-onset seizures. Adverse events such as dizziness and somnolence reported in clinical studies suggest that ESL has detectable central nervous system (CNS) effects in addition to its antiepileptic effects. This Phase I study evaluated the abuse liability of ESL compared with that of alprazolam (ALP) and placebo (PBO) in recreational CNS depressant users.

METHODS

In this single-dose, randomized, double-blind, PBO- and active-controlled crossover study, healthy recreational CNS depressant users who could discern between ALP 2mg and PBO received single oral doses of each of the following treatments with a washout interval of ≥7days between each treatment: ESL (800mg, 1600mg, 2000mg, and 2400mg); ALP (1.5mg and 3.0mg); and PBO. Subjective measures, including visual analog scales (VASs) e.g., Drug-Liking (primary endpoint), and Addiction Research Center Inventory (ARCI) Morphine-Benzedrine Group (MBG), Pentobarbital Chlorpromazine Alcohol Group (PCAG), and Lysergic Acid Diethylamide Group scales were evaluated at multiple time points up to 24h postdose. Cognitive effects were evaluated using the Choice Reaction Time (CRT), Divided Attention (DAT) and Hopkins Verbal Learning Task-Revised tests.

PRINCIPAL RESULTS

Peak scores for Drug-Liking VAS (maximum effect [Emax]) were significantly higher for both ALP doses than for PBO (p<0.0001), thereby confirming study validity. Drug-Liking VAS Emax was significantly lower for all ESL doses than both ALP doses (p<0.0001). Drug-Liking VAS Emax for ESL 800mg was similar to that for PBO (least squares [LS] mean difference: 3.6; p=0.19). At the three higher ESL doses (1600mg and the supratherapeutic doses of 2000mg and 2400mg), Drug-Liking VAS Emax was significantly higher than for PBO, although the differences were minimal (LS mean difference: 9.3-13.3 out of 100). For most secondary subjective endpoints (i.e., Good Effects VAS and High VAS, ARCI-MBG, Take Drug Again VAS, Overall Drug-Liking VAS, and ARCI-PCAG; p<0.05), the effect of ESL (all doses) was significantly less than that of ALP (both doses). On most secondary measures, the dose-response relationship was relatively flat or showed saturation at higher ESL doses. Although significant differences were observed for ESL compared with those for PBO for some specific CRT and DAT endpoints (i.e., reaction time, manual tracking, hit latency), ALP demonstrated significant and dose-dependent impairment on the majority of cognitive endpoints when compared with PBO and ESL. Mean plasma concentrations of the active metabolite of ESL, eslicarbazepine, increased with increasing ESL dose. Pharmacokinetic parameters estimated for eslicarbazepine were generally comparable with results from previous studies in healthy volunteers.

CONCLUSION

This study demonstrated that single doses of ESL may have less abuse liability than ALP in recreational sedative users. Although ESL had detectable subjective effects and showed some drug-'liking' at higher doses, the magnitude of these effects was small.

Assessment of human abuse potential of dasotraline compared to methylphenidate and placebo in recreational stimulant users

AIMS

The aim of this study was to evaluate the abuse potential of dasotraline, a novel dopamine and norepinephrine reuptake inhibitor with slow absorption (tmax, 10-12h) and elimination (t1/2=47-77 h) that is in development for the treatment of attention deficit hyperactivity disorder (ADHD).

METHODS

Recreational stimulant users (N=48) who had specific experience with cocaine, and who were able to distinguish methylphenidate (60 mg) versus placebo in a qualification session, were randomized, in a 6-period, double-blind, crossover design, to receive single doses of dasotraline 8 mg, 16 mg, and 36 mg, methylphenidate (MPH) 40 mg and 80 mg, and placebo. The primary endpoint was the Drug Liking Visual Analog Scale (VAS) score at the time of peak effect (Emax).

RESULTS

There were no significant differences between the 3 doses of dasotraline and placebo on the drug liking VAS at Emax, and on most secondary endpoints. Both doses of MPH had significantly higher VAS-drug liking scores at Emax relative to both placebo (P<0.001 for all comparisons) and dasotraline 8 mg (P<0.001), 16 mg (P<0.001) and 36 mg (P<0.01). The increase in heart rate for MPH and dasotraline 36 mg showed a time-course that closely matched subject-rated measures such as Any Effects VAS.

CONCLUSIONS

In this study, dasotraline was found to have low potential for abuse, which may be, in part, related to its established pharmacokinetics (PK) profile, which is characterized by slow absorption and gradual elimination.

Assessment of Pharmacokinetic and Pharmacodynamic Interactions Between Albumin-Fused Mutated Butyrylcholinesterase and Intravenously Administered Cocaine in Recreational Cocaine Users

Cocaine dependence presents a major public health issue, and to date, no pharmacotherapies are approved for its treatment. TV-1380 is a novel recombinant albumin-fused mutated butyrylcholinesterase (Albu-BChE) that has increased catalytic efficiency for cocaine compared with wild-type BChE and therefore has the potential to facilitate abstinence in cocaine-dependent subjects by decreasing exposure to cocaine and its reinforcing effects.

METHODS

This randomized, double-blind, placebo-controlled, parallel-group study in nondependent cocaine users was conducted to evaluate the effect of a single intramuscular dose of Albu-BChE (50, 100, and 300 mg) on the pharmacokinetic and metabolic profile of intravenous cocaine infusions (40 mg) administered at baseline and at 24, 96, and 168 hours after Albu-BChE dosing, to assess safety of coadministering Albu-BChE and cocaine, and to explore the subjective responses to cocaine infusions after Albu-BChE dosing.

RESULTS

Administration of Albu-BChE resulted in significant dose-dependent reductions in cocaine exposure (maximum concentration, area under the curve) and half-life. Effects were greatest at 24 hours after Albu-BChE dose, but were sustained up to 168 hours. Spearman correlations indicated a significant negative relationship between Albu-BChE concentration and cocaine clearance and exposure. Consistent with its mechanism of action, Albu-BChE also shifted cocaine metabolism toward preferential formation of ecgonine methyl ester. Administration of Albu-BChE was associated with modest decreases in subjective reports of feeling high and willingness to take cocaine again after cocaine infusion. Coadministration of Albu-BChE and cocaine was safe and well tolerated.

CONCLUSIONS

Administration of Albu-BChE at single doses of 50, 100, and 300 mg safely resulted in long-lasting decreases in cocaine exposure in recreational cocaine users.

The Contribution of Differential Opioid Responsiveness to Identification of Opioid Risk in Chronic Pain Patients

The Screener and Opioid Assessment for Patients with Pain-Revised (SOAPP-R) predicts increased risk of opioid misuse in chronic pain patients. We evaluated whether higher SOAPP-R scores are associated with greater opioid reinforcing properties, potentially contributing to their predictive utility. Across 2 counterbalanced laboratory sessions, 55 chronic low back pain sufferers completed the SOAPP-R at baseline and measures of back pain intensity, evoked pain responsiveness (thermal, ischemic), and subjective opioid effects after receiving intravenous morphine (.08 mg/kg) or saline placebo. Morphine effect measures were derived for all outcomes, reflecting the difference between morphine and placebo condition values. Higher SOAPP-R scores were significantly associated with greater desire to take morphine again, less feeling down and feeling bad, and greater reductions in sensory low back pain intensity following morphine administration. This latter effect was due primarily to SOAPP-R content assessing medication-specific attitudes and behavior. Individuals exceeding the clinical cutoff (18 or higher) on the SOAPP-R exhibited significantly greater morphine liking, desire to take morphine again, and feeling sedated; less feeling bad; and greater reductions in sensory low back pain following morphine. The SOAPP-R may predict elevated opioid risk in part by tapping into individual differences in opioid reinforcing effects.

PERSPECTIVE

Based on placebo-controlled morphine responses, associations were observed between higher scores on a common opioid risk screener (SOAPP-R) and greater desire to take morphine again, fewer negative subjective morphine effects, and greater analgesia. Opioids may provide the best analgesia in those patients at greatest risk of opioid misuse.

Comparing the Effect of Tampering on the Oral Pharmacokinetic Profiles of Two Extended-Release Oxycodone Formulations with Abuse-Deterrent Properties

OBJECTIVE

Oxycodone DETERx® is an extended-release (ER), microsphere-in-capsule abuse-deterrent-formulation designed to retain its extended-release properties following tampering or misuse (e.g., chewing, crushing). This study assessed the safety and pharmacokinetics of orally administered intact and crushed Oxycodone DETERx® capsules compared with intact and crushed reformulated OxyContin® tablets and crushed immediate-release oxycodone tablets (IR oxycodone).

METHODS

This was a randomized, open-label, active-controlled, cross-over study. Healthy subjects received five oxycodone treatments (40 mg) with a standardized high-fat, high-calorie meal: Oxycodone DETERx® (intact or crushed), OxyContin® (intact or crushed), and IR oxycodone (crushed). Blood samples were collected for assessment of oxycodone plasma concentrations.

RESULTS

Thirty-eight subjects completed the study. Both crushed and intact Oxycodone DETERx® resulted in lower peak plasma concentrations when compared with IR oxycodone. Crushed Oxycodone DETERx® was bioequivalent to intact Oxycodone DETERx® and exhibited a numerically lower Cmax . Also, median Tmax was unchanged by crushing. In contrast, mean peak plasma oxycodone concentrations for crushed OxyContin® were significantly higher compared with intact OxyContin® and were bioequivalent to IR oxycodone. Median Tmax for crushed OxyContin® was the same as IR oxycodone and 3.25 hours shorter than intact OxyContin®.

CONCLUSIONS

These data demonstrate that when crushed and taken orally, Oxycodone DETERx® maintains its EXTENDED-release profile, while crushed OxyContin® shows a pharmacokinetic profile similar to an immediate-release product. These results suggest that Oxycodone DETERx® may be less attractive to illicit drug users compared with existing abuse-deterrent-formulations, while providing a safer option for patients who may unknowingly crush their medication such as those who have difficulty swallowing.

Use of Remifentanil in a Novel Clinical Paradigm to Characterize Onset and Duration of Opioid Blockade by Samidorphan, a Potent μ-Receptor Antagonist

A novel clinical study design was used to evaluate the blockade of a selective short-acting μ-opioid agonist (remifentanil) in 24 opioid-experienced subjects. Samidorphan (3-carboxamido-4-hydroxynaltrexone) is a novel opioid modulator with μ-antagonist properties. Objective (pupil diameter) and subjective (visual analog scale) responses to repeated remifentanil and saline infusion challenges were assessed after single oral administration of placebo (day 1) and samidorphan (day 2). Complete blockade persisted with samidorphan for 24 hours for pupil miosis and 48 hours for the drug liking visual analog scale. Samidorphan effects persisted beyond measurable samidorphan exposure (t½ = 7 hours). Samidorphan was associated with complete blockade of remifentanil, and the duration supports daily administration. This study used a novel approach with multiple administrations of remifentanil to successfully demonstrate a durable effect with samidorphan and a rapid and potent blockade of physiological and subjective μ-opioid effects.

Indicators of drug-seeking aberrant behaviours: the feasibility of use in observational post-marketing cohort studies for risk management

Background

Problematic prescription drug use is reflected by or associated with drug-seeking aberrant behaviours. Research gaps include lack of post-marketing evidence and instruments. As part of the pharmacovigilance requirements, a risk management plan was developed for fentanyl buccal tablets (FEBT) by the manufacturer, with an additional pharmacovigilance activity requested by the regulatory authority, to investigate the risks of misuse, abuse, criminal use, off-label use and accidental exposure to FEBT after the product became commercially available. A Modified Prescription-Event Monitoring (M-PEM), observational, post-authorisation safety surveillance (PASS) study was conducted, with an overall aim to examine the use of FEBT in relation to their safety as prescribed in primary care in England. One of the exploratory objectives included estimating the prevalence of aberrant behaviours during FEBT treatment.

Objective

To determine the feasibility of estimating the prevalence of risk factors associated with dependence on starting treatment and aberrant behaviours in patients during treatment with a prototypical abuse liable substance (fentanyl), as based on the application of an existing index (the Chabal criteria).

Methods

Data were collected as part of the M-PEM PASS study; exposure and outcome data (including risk factors for dependence and aberrant behaviours based on behavioural not clinical manifestations) were derived from questionnaires sent to primary care physicians in England during April 2008 to June 2011. For the exploratory objective of interest, descriptive statistics and simple (non-weighted) risk scores were constructed on aggregate counts (score ≥3 considered ‘high-risk’). Supplementary analyses explored the relationship between the two indices and the characteristics of patients with aberrant behaviours and those without (crude odds ratios plus 95 % confidence interval (CI) were calculated).

Results

In a cohort of 551 patients, the prevalence of at least one pre-existing risk factor for dependence was 26 % (n = 145), whilst the frequency of aberrant behaviours observed during treatment was 8 % (n = 46). Patients with aberrant behaviours had several different characteristics to patients without. The two indices were associated (χ² df (20) = 58.72, p < 0.001), but a high-dependence risk-factor score provided a poor indication of high aberrant behaviour risk; the area under the receiver operating characteristic curve was 0.58 (95 % CI 0.41, 0.74).

Limitations

Study limitations included subjectivity in relation to physicians identifying aberrant behaviours, and under-reporting thereof in PASS observational study designs. The presence of these criteria does not confirm misuse, but should be considered as a signal of problematic opioid misuse, which requires investigation. Further research is needed to develop a more robust analytical construct.

Conclusion

In this PASS study, the prevalence of at least one pre-existing risk factor for dependence was 26 %, whilst the frequency of aberrant behaviours observed during treatment was 8 %. Patients with aberrant behaviours had several different characteristics to patients without. This study demonstrates the feasibility of the systematic collection of physician reports of risk factors for dependence and aberrant behaviours to facilitate the development of risk scores, using these reports to support the post-marketing risk management of products with misuse potential.

MDMA alters emotional processing and facilitates positive social interaction

BACKGROUND

±3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") produces "prosocial" effects, such as feelings of empathy and closeness, thought to be important to its abuse and its value in psychotherapy. However, it is not fully understood how MDMA alters basic emotional processes to produce these effects, or whether it produces corresponding changes in actual social behavior. Here, we examined how MDMA affects perceptions of and responses to emotional expressions, and tested its effects on behavior during a social interaction. We also examined whether MDMA's prosocial effects related to a measure of abuse liability.

METHODS

Over three sessions, 36 healthy volunteers with previous ecstasy use received MDMA (0.75, 1.5 mg/kg) and placebo under double-blind conditions. We measured (i) mood and cardiovascular effects, (ii) perception of and psychophysiological responses to emotional expressions, (iii) use of positive and negative words in a social interaction, and (iv) perceptions of an interaction partner. We then tested whether these effects predicted desire to take the drug again.

RESULTS

MDMA slowed perception of angry expressions, increased psychophysiological responses to happy expressions, and increased positive word use and perceptions of partner empathy and regard in a social interaction. These effects were not strongly related to desire to take the drug again.

CONCLUSIONS

MDMA alters basic emotional processes by slowing identification of negative emotions and increasing responses to positive emotions in others. Further, it positively affects behavior and perceptions during actual social interaction. These effects may contribute to the efficacy of MDMA in psychotherapy, but appear less closely related to its abuse potential.

Relationship between intranasal cocaine self-administration and subject-rated effects: predictors of cocaine taking on progressive-ratio schedules

OBJECTIVE

Subject-rated measures and drug self-administration represent two of the most commonly used methods of assessing abuse potential of drugs, as well as screening intervention efficacy in the human laboratory. Although the results from these methods are often consistent, dissociations between subject-rated and self-administration data have been observed. The purpose of the present retrospective analysis was to examine the relationship between subject-rated effects and intranasal cocaine self-administration to help guide future research design and intervention assessment.

METHODS

Data were combined from two previous studies in which drug and an alternative reinforcer (i.e., money) were available on concurrent progressive-ratio schedules of reinforcement. Pearson correlation coefficients and regression model selection utilizing corrected Akaike information criterion were used to determine which subject-rated measures were associated with and best predicted cocaine self-administration.

RESULTS

Eleven subject-rated effects were positively associated with cocaine-maintained breakpoints. A combination of three of these subject ratings (i.e., Like Drug, Performance Improved, and Rush) best predicted cocaine taking.

CONCLUSIONS

The present findings suggest that, at least under certain conditions with intranasal cocaine, some, but not all, positive subject-rated effects may predict drug self-administration. These findings will be useful in guiding future examinations of putative interventions for cocaine-use disorders.

Separate and combined impact of acute naltrexone and alprazolam on subjective and physiological effects of oral d-amphetamine in stimulant users

RATIONALE

Opioid antagonists (e.g., naltrexone) and positive modulators of γ-aminobutyric-acidA (GABAA) receptors (e.g., alprazolam) modestly attenuate the abuse-related effects of stimulants like amphetamine. The use of higher doses to achieve greater efficacy is precluded by side effects. Combining naltrexone and alprazolam might safely maximize efficacy while avoiding the untoward effects of the constituent compounds.

OBJECTIVES

The present pilot study tested the hypothesis that acute pretreatment with the combination of naltrexone and alprazolam would not produce clinically problematic physiological effects or negative subjective effects and would reduce the positive subjective effects of d-amphetamine to a greater extent than the constituent drugs alone.

METHODS

Eight nontreatment-seeking, stimulant-using individuals completed an outpatient experiment in which oral d-amphetamine (0, 15, and 30 mg) was administered following acute pretreatment with naltrexone (0 and 50 mg) and alprazolam (0 and 0.5 mg). Subjective effects, psychomotor task performance, and physiological measures were collected.

RESULTS

Oral d-amphetamine produced prototypical physiological and stimulant-like positive subjective effects (e.g., VAS ratings of Active/Alert/Energetic, Good Effect, and High). Pretreatment with naltrexone, alprazolam, and their combination did not produce clinically problematic acute physiological effects or negative subjective effects. Naltrexone and alprazolam each significantly attenuated some of the subjective effects of d-amphetamine. The combination attenuated a greater number of subjective effects than the constituent drugs alone.

CONCLUSIONS

The present results support the continued evaluation of an opioid receptor antagonist combined with a GABAA-positive modulator using more clinically relevant experimental conditions like examining the effect of chronic dosing with these drugs on methamphetamine self-administration.

Evaluation of the safety, pharmacodynamic, and pharmacokinetic effects following oral coadministration of immediate-release morphine with ethanol in healthy male participants

OBJECTIVE

This paper aimed to evaluate the effects of coadministered immediate-release morphine and ethanol on safety, pharmacokinetic, and pharmacodynamic measures.

METHODS

In the first stage of a randomized, double-blind, placebo-controlled, crossover study, 16 healthy men with a history of moderate drinking received morphine 50 mg+ethanol 0.7 g/kg, morphine 50 mg+ethanol placebo, and morphine placebo+ethanol 0.7 g/kg. In the second stage, participants received either a lower (30 mg) or higher (80 mg) morphine dose (alone and in combination with ethanol) depending on their tolerability to treatments in stage 1. Safety, pharmacodynamic (including visual analog scales, pupillometry, capnography, and psychomotor and cognitive measures), and pharmacokinetic assessments were conducted.

RESULTS

With the exception of one severe adverse event (AE), all others were mild or moderate in intensity. Morphine resulted in dose-related increases in AEs. When morphine was administered with ethanol, similar AEs were observed (dizziness, headache, somnolence, nausea, and vomiting), but these were sometimes more frequent compared with those observed with either drug alone. No consistent additive or interaction effects were observed on pharmacodynamic measures. Ethanol had no apparent effects on the pharmacokinetics of morphine or its metabolites.

CONCLUSIONS

Coadministration of single doses of morphine and ethanol tested in this study did not affect the safety, pharmacodynamics, or pharmacokinetics of morphine or ethanol administered alone. Copyright © 2014 John Wiley & Sons, Ltd.