Treatment with modafinil and escitalopram, alone and in combination, on cocaine-induced effects: a randomized, double blind, placebo-controlled human laboratory study

Integrative Pharmacology in the Treatment of Substance Use Disorders

The detrimental physical, mental, and socioeconomic effects of substance use disorders (SUDs) have been apparent to the medical community for decades. However, it has become increasingly urgent in recent years to develop novel pharmacotherapies to treat SUDs. Currently, practitioners typically rely on monotherapy. Monotherapy has been shown to be superior to no treatment at all for most substance classes. However, many randomized controlled trials (RCTs) have revealed that monotherapy leads to poorer outcomes when compared with combination treatment in all specialties of medicine. The results of RCTs suggest that monotherapy frequently fails since multiple dysregulated pathways, enzymes, neurotransmitters, and receptors are involved in the pathophysiology of SUDs. As such, research is urgently needed to determine how various neurobiological mechanisms can be targeted by novel combination treatments to create increasingly specific yet exceedingly comprehensive approaches to SUD treatment. This article aims to review the neurobiology that integrates many pathophysiologic mechanisms and discuss integrative pharmacology developments that may ultimately improve clinical outcomes for patients with SUDs. Many neurobiological mechanisms are known to be involved in SUDs including dopaminergic, nicotinic, N-methyl-D-aspartate (NMDA), and kynurenic acid (KYNA) mechanisms. Emerging evidence indicates that KYNA, a tryptophan metabolite, modulates all these major pathophysiologic mechanisms. Therefore, achieving KYNA homeostasis by harmonizing integrative pathophysiology and pharmacology could prove to be a better therapeutic approach for SUDs. We propose KYNA-NMDA-α7nAChRcentric pathophysiology, the "conductor of the orchestra," as a novel approach to treat many SUDs concurrently. KYNA-NMDA-α7nAChR pathophysiology may be the "command center" of neuropsychiatry. To date, extant RCTs have shown equivocal findings across comparison conditions, possibly because investigators targeted single pathophysiologic mechanisms, hit wrong targets in underlying pathophysiologic mechanisms, and tested inadequate monotherapy treatment. We provide examples of potential combination treatments that simultaneously target multiple pathophysiologic mechanisms in addition to KYNA. Kynurenine pathway metabolism demonstrates the greatest potential as a target for neuropsychiatric diseases. The investigational medications with the most evidence include memantine, galantamine, and N-acetylcysteine. Future RCTs are warranted with novel combination treatments for SUDs. Multicenter RCTs with integrative pharmacology offer a promising, potentially fruitful avenue to develop novel therapeutics for the treatment of SUDs.

Contingency management plus acceptance and commitment therapy for initial cocaine abstinence: Results of a sequential multiple assignment randomized trial (SMART)

BACKGROUND

This study tested an adaptive intervention for optimizing abstinence outcomes over phases of treatment for cocaine use disorder using a SMART design. Phase 1 assessed whether 4 weeks of contingency management (CM) improved response with the addition of Acceptance and Commitment Therapy (ACT). Phase 2 assessed pharmacological augmentation with modafinil (MOD) vs. placebo (PLA) for individuals not achieving abstinence during Phase 1.

METHOD

For Phase 1 of treatment, participants (N=118) were randomly allocated to ACT+CM or Drug Counseling (DC+CM), the comparison condition. At week 4, treatment response was defined as the submission of six consecutive cocaine-negative urine drug screens (UDS). Phase 1 non-responders were re-randomized to MOD or PLA as adjunct to their initial treatment. Phase 1 responders continued receiving their initial treatment. Primary outcomes included response rate and proportion of cocaine-negative UDS for Phase 1 and 2. Analyses used Bayesian inference with 80% pre-specified as the posterior probability (PP) threshold constituting moderate evidence that an effect exists.

RESULTS

Phase 1 response was higher in the ACT+CM group (24.5%) compared to the DC+CM group (17.5%; PP = 84.5%). In Phase 2, the proportion of cocaine-negative UDS among Phase 1 responders did not differ by initial treatment (PP = 61.8%) but remained higher overall compared to Phase 1 non-responders (PPs > 99%). No evidence of an effect favoring augmentation with MOD was observed.

DISCUSSION

Adding ACT to CM increased abstinence initiation. Initial responders were more likely to remain abstinent compared to initial non-responders, for whom modafinil was not an effective pharmacotherapy augmentation strategy.

Potential effect of antidepressants on remission from cocaine use disorder - A nationwide matched retrospective cohort study

BACKGROUND

Cocaine use disorder (CUD) is a significant public health issue for which there is no Food and Drug Administration-approved pharmacotherapy. Depressive disorders are common psychiatric comorbidity amongst individuals with CUD.

METHODS

A retrospective cohort study was conducted among 161,544 patients diagnosed with CUD and depression to evaluate the effectiveness of 13 antidepressants on CUD remission. For any antidepressant found to be associated with CUD remission that had an additional indication, we conducted an additional analysis to evaluate the effectiveness of the candidate drug in patients with CUD with that indication. We then analyzed publicly genomic and functional databases to identify potential explanatory mechanisms of action of the candidate drug in the treatment of CUD.

RESULTS

Among these antidepressants, bupropion was associated with higher rates of CUD remission compared to propensity-score matched patients prescribed other antidepressants: hazard ratio (HR) and 95% confidence interval (CI) 1.57 (95% CI: 1.27-1.94). Bupropion is also approved for smoking cessation. We identified CUD patients with co-occurring nicotine dependence and observed that patients prescribed bupropion displayed a higher rate of CUD remission compared to matched individuals prescribed other drugs for nicotine dependence: 1.38 (95% CI: 1.11-1.71). Genetic and functional analyses revealed that bupropion interacts with four protein-encoding genes (COMT, DRD2, SLC6A3, and SLC6A4) which are also associated with CUD and targets CUD-associated pathways including serotonergic synapses, cocaine addiction, and dopaminergic synapses.

CONCLUSIONS

Our findings suggest that bupropion might be considered a treatment for improving CUD remission in patients with CUD and co-occurring depression or nicotine dependence.

A mechanistic overview of approaches for the treatment of psychostimulant dependence

Psychostimulant use disorder is a major health issue around the world with enormous individual, family-related and societal consequences, yet there are no effective pharmacological treatments available. In this review, a target-based overview of pharmacological treatments toward psychostimulant addiction will be presented. We will go through therapeutic approaches targeting different aspects of psychostimulant addiction with focus on three major areas; 1) drugs targeting signalling, and metabolism of the dopamine system, 2) drugs targeting either AMPA receptors or metabotropic glutamate receptors of the glutamate system and 3) drugs targeting the severe side-effects of quitting long-term psychostimulant use. For each of these major modes of intervention, findings from pre-clinical studies in rodents to clinical trials in humans will be listed, and future perspectives of the different treatment strategies as well as their potential side-effects will be discussed. Pharmaceuticals modulating the dopamine system, such as antipsychotics, DAT-inhibitors, and disulfiram, have shown some promising results. Cognitive enhancers have been found to increase aspects of behavioural control, and drugs targeting the glutamate system such as modulators of metabotropic glutamate receptors and AMPA receptors have provided interesting changes in relapse behaviour. Furthermore, CRF-antagonists directed toward alleviating the symptoms of the withdrawal stage have been examined with interesting resulting changes in behaviour. There are promising results investigating therapeutics for psychostimulant addiction, but further preclinical work and additional human studies with a more stratified patient selection are needed to prove sufficient evidence of efficacy and tolerability.

Human behavioral pharmacology of stimulant drugs: An update and narrative review

Stimulant use disorders present an enduring public health concern. Chronic stimulant use is associated with a range of health problems, with notable increases in stimulant overdose that disproportionately affect marginalized populations. With these persistent problems, it is important to understand the behavioral and pharmacological factors that contribute to stimulant use in humans. The purpose of this chapter is to provide an update and narrative review on recent human laboratory research that has evaluated the behavioral pharmacology of stimulant drugs. We focus on two prototypic stimulants: cocaine as a prototype monoamine reuptake inhibitor and d-amphetamine as a prototype monoamine releaser. As such, placebo controlled human laboratory studies that involved administration of doses of cocaine or d-amphetamine and were published in peer reviewed journals within the last 10 years (i.e., since 2011) are reviewed. Primary outcomes from these studies are subjective effects, reinforcing effects, cognitive/behavioral effects, and discriminative stimulus effects. Both cocaine and d-amphetamine produce classical stimulant-like behavioral effects (e.g., increase positive subjective effects, function as reinforcers), but there are notable gaps in the literature including understanding sex differences in response to stimulant drugs, cognitive-behavioral effects of stimulants, and influence of use history (e.g., relatively drug naïve vs drug experienced) on stimulant effects.

Clinical neuropharmacology of cocaine reinforcement: A narrative review of human laboratory self-administration studies

Cocaine use is an unrelenting public health concern. To inform intervention and prevention efforts, it is crucial to develop an understanding of the clinical neuropharmacology of the reinforcing effects of cocaine. The purpose of this review is to evaluate and synthesize human laboratory studies that assess pharmacological manipulations of cocaine self-administration. Forty-one peer-reviewed, human cocaine self-administration studies in which participants received a pretreatment drug were assessed. The pharmacological action and treatment regimen for all drugs reviewed were considered. Drugs that increase extracellular dopamine tend to have the most consistent effects on cocaine self-administration. The ability of nondopaminergic drugs to impact cocaine reinforcement might be related to their downstream effects on dopamine, though it is difficult to draw conclusions because pharmacologically selective compounds are not widely available for human testing. The ability of acute versus chronic drug treatment to differentially affect human cocaine self-administration was not determined because buprenorphine was the only pretreatment drug that was assessed under both acute and chronic dosing regimens. Future research directly comparing acute and chronic drug treatment and/or comparing drugs with different mechanisms of action, is needed to make more conclusive determinations about the clinical neuropharmacology of cocaine reinforcement.

Psychostimulant Use Disorder, an Unmet Therapeutic Goal: Can Modafinil Narrow the Gap?

The number of individuals affected by psychostimulant use disorder (PSUD) has increased rapidly over the last few decades resulting in economic, emotional, and physical burdens on our society. Further compounding this issue is the current lack of clinically approved medications to treat this disorder. The dopamine transporter (DAT) is a common target of psychostimulant actions related to their use and dependence, and the recent availability of atypical DAT inhibitors as a potential therapeutic option has garnered popularity in this research field. Modafinil (MOD), which is approved for clinical use for the treatment of narcolepsy and sleep disorders, blocks DAT just like commonly abused psychostimulants. However, preclinical and clinical studies have shown that it lacks the addictive properties (in both behavioral and neurochemical studies) associated with other abused DAT inhibitors. Clinical availability of MOD has facilitated its off-label use for several psychiatric disorders related to alteration of brain dopamine (DA) systems, including PSUD. In this review, we highlight clinical and preclinical research on MOD and its R-enantiomer, R-MOD, as potential medications for PSUD. Given the complexity of PSUD, we have also reported the effects of MOD on psychostimulant-induced appearance of several symptoms that could intensify the severity of the disease (i.e., sleep disorders and impairment of cognitive functions), besides the potential therapeutic effects of MOD on PSUD.

Pharmacotherapeutic strategies for treating cocaine use disorder-what do we have to offer?

BACKGROUND

Cocaine use contines to be a significant public health problem world-wide. However, despite substantial research efforts, no pharmacotherapies are approved for the treatment of cocaine use disorder (CUD).

ARGUMENT

Studies have identified positive signals for a range of medications for treating CUD. These include long-acting amphetamine formulations, modafinil, topiramate, doxazosin and combined topiramate and mixed amphetamine salts extended-release (MAS-ER). However, valid conclusions about a medication's clinical efficacy require nuanced approaches that take into account behavioural phenotypes of the target population (frequency of use, co-abuse of cocaine and other substances, genetic subgroups, psychiatric comorbidity), variables related to the medication (dose, short-/long-acting formulations, titration speed, medication adherence) and other factors that may affect treatment outcomes. Meta-analyses frequently do not account for these co-varying factors, which contributes to a somewhat nihilistic view on pharmacotherapeutic options for CUD. In addition, the predominant focus on abstinence, which is difficult for most patients to achieve, may overshadow more nuanced therapeutic signals.

CONCLUSION

While there is an emphasis on finding new medications with novel mechanisms of action for treating CUD, currently available medications deserve further investigation based on the existing literature. Evaluating refined metrics of treatment success in well-defined subgroups of patients, and further exploring combination therapies and their synergy with behavioural/psychosocial interventions, are promising avenues to establishing effective therapies for CUD.

Modafinil reduces smoked cocaine self-administration in humans: effects vary as a function of cocaine 'priming' and cost

BACKGROUND

The absence of an FDA-approved medication for the treatment of cocaine use disorder (CUD) may, in part, reflect the varying conditions present when the decision to use cocaine is made, with one medication unlikely to work under all conditions. The objective of this double-blind, placebo-controlled, human laboratory study was to test the effects of modafinil, a medication with mixed efficacy for the treatment of CUD, using a novel self-administration procedure designed to model distinct clinical scenarios.

METHODS

During modafinil maintenance (0, 300 mg/day), participants chose to self-administer up to 7 doses of smoked cocaine (25 mg) under 9 conditions: immediately after exposure to: (a) cues associated with cocaine and a non-contingent cocaine administration, i.e. 'prime' (25 mg), (b) only cocaine cues, and (c) neither cues nor cocaine. Each condition was tested when self-administered cocaine cost $5, $10 and $15/dose.

RESULTS

Nontreatment-seeking cocaine smokers (3 F,13 M), spending $388 ± 218/week on cocaine and with no history of alcohol use disorder, completed the study. Relative to placebo, modafinil robustly attenuated self-administration when cocaine was expensive ($10,$15/dose) and when there was no 'prime.' Modafinil had no effect on self-administration when cocaine was inexpensive ($5/dose) or when participants received a 'prime.'

CONCLUSIONS

Modafinil's effects on cocaine-taking varied substantially as a function of recent cocaine exposure and cost, which may help explain the mixed clinical findings. Modafinil may be most effective for preventing relapse in abstinent patients, particularly under conditions in which cocaine is costly, rather than initiating abstinence for those continuing to use cocaine.

Improving translation of animal models of addiction and relapse by reverse translation

Critical features of human addiction are increasingly being incorporated into complementary animal models, including escalation of drug intake, punished drug seeking and taking, intermittent drug access, choice between drug and non-drug rewards, and assessment of individual differences based on criteria in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Combined with new technologies, these models advanced our understanding of brain mechanisms of drug self-administration and relapse, but these mechanistic gains have not led to improvements in addiction treatment. This problem is not unique to addiction neuroscience, but it is an increasing source of disappointment and calls to regroup. Here we first summarize behavioural and neurobiological results from the animal models mentioned above. We then propose a reverse translational approach, whose goal is to develop models that mimic successful treatments: opioid agonist maintenance, contingency management and the community-reinforcement approach. These reverse-translated 'treatments' may provide an ecologically relevant platform from which to discover new circuits, test new medications and improve translation.

Modulating the immune response with the wake-promoting drug modafinil: A potential therapeutic approach for inflammatory disorders

Modafinil is a psychostimulant drug approved by the FDA primarily for the treatment of sleep disorders such as narcolepsy, excessive daytime sleepiness and sleep apnea. Several documented but not yet approved uses for modafinil have been described over the last 30 years, including alleviating fatigue in neurological and neurodegenerative disorders. Recent evidence has suggested that modafinil may have an immunomodulatory effect. Here, we review the different effects of modafinil treatment in animal models of brain inflammation and peripheral immune function. We conclude that there is unequivocal evidence of an anti-inflammatory effect of modafinil in experimental animal models of brain inflammation and neurodegenerative disorders, including systemic inflammation and methamphetamine-induced neuroinflammation, Parkinson's disease, brain ischemia, and multiple sclerosis. Modafinil acts on resident glial cells and infiltrating immune cells, negatively affecting both innate and adaptive immune responses in the brain. We also review the outcomes of modafinil treatment on peripheral immune function. The results of studies on this subject are still controversial and far from conclusive, but point to a new avenue of research in relation to peripheral inflammation. The data reviewed here raise the possibility of modafinil being used as adjuvant treatment for neurological disorders in which inflammation plays an important role.

Clinical Trials for Stimulant Use Disorders: Addressing Heterogeneities That May Undermine Treatment Outcomes

In recent years, use of cocaine and amphetamines and deaths associated with stimulants have been on the rise, and there are still no FDA-approved medications for stimulant use disorders. One contributing factor may involve heterogeneity. At the neurobiological level, dual dopamine dysfunction may be undermining medication efficacy, suggesting a need for combination pharmacotherapies. At the population level, individual variability is expressed in a number of ways and, if left unaddressed, may interfere with medication efficacy. This chapter reviews studies investigating medications to address dopamine dysfunction, and it also identifies several prominent heterogeneities associated with stimulant (and other substance) use disorders. The chapter has implications for improving interventions to treat stimulant use disorders, and the theme of individual heterogeneity may have broader application across substance use disorders.

The treatment of cocaine use disorder

Cocaine use continues to be a serious worldwide public health problem. Cocaine abuse is associated with substantial morbidity and mortality. Cocaine overdose deaths are increasing in the United States and, in certain populations, outnumber heroin and opiate overdose deaths. Psychosocial treatments remain the treatments of choice for cocaine use disorder (CUD), with standard approaches including contingency management and cognitive behavioral therapy. However, the effect sizes of these treatments are not large, and they are not effective for most patients. Consequently, investigators have sought to develop pharmacological agents to augment the efficacy of psychosocial treatments. Despite these efforts, no medications have yet been proven to be safe and effective for the treatment of CUD. The most promising pharmacological strategies for CUD treatment thus far include the use of dopamine agonists, such as long-acting amphetamine and modafinil or glutamatergic and GABAergic agents such as topiramate. Combination drugs may be especially promising.

FAAH variant Pro129Thr modulates subjective effects produced by cocaine administration

BACKGROUND AND OBJECTIVES

The endogenous cannabinoid anandamide (AEA), an agonist at type-1 cannabinoid (CB1) receptors, is metabolized by fatty acid amide hydrolase (FAAH). The common variant rs324420 C->A within the FAAH gene on chromosome 1 codes for a missense substitution (Pro129Thr), resulting in decreased FAAH activity and increased endocannabinoid potentiation. This FAAH variant has been linked to alterations in mood and stress reactivity, as well as being independently linked to increased risk for addiction. We hypothesized that cocaine use disordered (CUD) participants with the FAAH Pro129 Thr variant would exhibit a distinct profile of cocaine-induced subjective effects in the laboratory.

METHODS

A total of 70 CUD participants received intravenous doses of saline (placebo, 0 mg) and cocaine (20, 40 mg) in a lab-controlled setting and rated 10 subjective effect measures prior to and following saline and cocaine administration, using a Visual Analog Scale (VAS).

RESULTS

The variant allele was associated with increased cocaine-induced subjective ratings for "Drug Effect," "High," and "Depressed." The prevalence of the variant allele A and the AA genotypes were greater in our CUD group than in the general population (A allele: 47% vs. 34%; AA genotype: 30% vs. 13%; p < .05). Finally, the reported amount and frequency of tobacco and cocaine use was higher in subjects with the AC/AA allele.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

These results add to existing evidence that this variant of the FAAH genotype may be over-represented among those who have CUD, and this over-representation may result from greater subjective responses to cocaine administration. (Am J Addict 2018;27:567-573).

Pharmacotherapies for decreasing maladaptive choice in drug addiction: Targeting the behavior and the drug

Drug addiction can be conceptualized as a disorder of maladaptive decision making in which drugs are chosen at the expense of pro-social, nondrug alternatives. The study of decision making in drug addiction has focused largely on the role of impulsivity as a facilitator of addiction, in particular the tendency for drug abusers to choose small, immediate gains over larger but delayed outcomes (i.e., delay discounting). A parallel line of work, also focused on decision making in drug addiction, has focused on identifying the determinants underlying the choice to take drugs over nondrug alternatives (i.e., drug vs. nondrug choice). Both tracks of research have been valuable tools in the development of pharmacotherapies for treating maladaptive decision making in drug addiction, and a number of common drugs have been studied in both designs. However, we have observed that there is little uniformity in the administration regimens of potential treatments between the designs, which hinders congruence in the development of single treatment strategies to reduce both impulsive behavior and drug choice. The current review provides an overview of the drugs that have been tested in both delay-discounting and drug-choice designs, and focuses on drugs that reduced the maladaptive choice in both designs. Suggestions to enhance congruence between the findings in future studies are provided. Finally, we propose the use of a hybridized, experimental approach that may enable researchers to test the effectiveness of therapeutics at decreasing impulsive and drug choice in a single design.

Atypical dopamine transporter inhibitors R-modafinil and JHW 007 differentially affect D2 autoreceptor neurotransmission and the firing rate of midbrain dopamine neurons

Abuse of psychostimulants like cocaine that inhibit dopamine (DA) reuptake through the dopamine transporter (DAT) represents a major public health issue, however FDA-approved pharmacotherapies have yet to be developed. Recently a class of ligands termed "atypical DAT inhibitors" has gained attention due to their range of effectiveness in increasing extracellular DA levels without demonstrating significant abuse liability. These compounds not only hold promise as therapeutic agents to treat stimulant use disorders but also as experimental tools to improve our understanding of DAT function. Here we used patch clamp electrophysiology in mouse brain slices to explore the effects of two atypical DAT inhibitors (R-modafinil and JHW 007) on the physiology of single DA neurons in the substantia nigra and ventral tegmental area. Despite their commonalities of being DAT inhibitors that lack cocaine-like behavioral profiles, these compounds exhibited surprisingly divergent cellular effects. Similar to cocaine, R-modafinil slowed DA neuron firing in a D2 receptor-dependent manner and rapidly enhanced the amplitude and duration of D2 receptor-mediated currents in the midbrain. In contrast, JHW 007 exhibited little effect on firing, slow DAT blockade, and an unexpected inhibition of D2 receptor-mediated currents that may be due to direct D2 receptor antagonism. Furthermore, pretreatment with JHW 007 blunted the cellular effects of cocaine, suggesting that it may be valuable to investigate similar DAT inhibitors as potential therapeutic agents. Further exploration of these and other atypical DAT inhibitors may reveal important cellular effects of compounds that will have potential as pharmacotherapies for treating cocaine use disorders.

Modafinil Treatment of Cocaine Dependence: A Systematic Review and Meta-Analysis

BACKGROUND

Currently, there is none FDA-approved medication to treat cocaine dependency. Studies conducted with various medications, including antipsychotics, antidepressants, anticonvulsants, and others, revealed inconsistent results.

OBJECTIVES

To meta-analytically investigate the efficacy and safety of modafinil in the treatment of cocaine-dependent patients.

METHODS

Randomized controlled trials with ≥20 subjects comparing the numerical therapeutic outcomes of modafinil with placebo were identified in databases, such as PUBMED, psycINFO, EMBASE, and Clinicaltrials.gov. Relevant data on efficacy and safety were extracted. Relative risk (RR) and standardized mean difference were applied for reporting dichotomous and continuous outcomes respectively. Random effects, subgroup, and meta-regression analyses were conducted to further explore the results and evaluate for any moderators.

RESULTS

In total, 11 studies (participants = 896, duration = 6.7 ± 1.9 weeks) comparing modafinil with placebo were systematically analyzed, which indicated that modafinil was not superior to placebo in improving the treatment retention rate (studies = 11, participants = 891, RR = 1.030, 95% CI = 0.918-1.156, p = .613). Similarly, data from 7/11 studies did not evidence superiority of modafinil in achieving cocaine abstinence (participants = 696, RR = 1.259, 95% CI = 0.813-1.949, p = .302). However, subgroup analysis of six studies conducted in the United States demonstrated superiority of modafinil in cocaine abstinence rate (studies = 6, participants = 669, 95% CI = 1.027-2.020, p = 0.035). In addition, no evidence suggested modafinil-related discontinuation or specific adverse events than placebo.

CONCLUSIONS

Overall, there is no evidence to conclude superiority of modafinil in increasing cocaine abstinence and treatment retention rate. However, promising result in subgroup analysis of cocaine abstinence, secondary outcomes, and good safety profile urged the need of larger studies to derive more conclusive results.

The Novel Modafinil Analog, JJC8-016, as a Potential Cocaine Abuse Pharmacotherapeutic

(±)Modafinil ((±)MOD) and its R-enantiomer (R-modafinil; R-MOD) have been investigated for their potential as treatments for psychostimulant addiction. We recently reported a series of (±)MOD analogs, of which JJC8-016 (N-(2-((bis(4-fluorophenyl)methyl)thio)ethyl)-3-phenylpropan-1-amine) was selected for further development. JJC8-016 and R-MOD were evaluated for binding across ~70 receptors, transporters, and enzymes. Although at a concentration of 10 μM, there were many hits for JJC8-016, binding affinities in the range of its DAT affinity were only observed at the serotonin transporter (SERT), dopamine D₂-like, and sigma₁ receptors. R-MOD was more selective, but had much lower affinity at the DAT (K_i=3 μM) than JJC8-016 (K_i=116 nM). In rats, systemic administration of R-MOD alone (10-30 mg/kg i.p.) dose-dependently increased locomotor activity and electrical brain-stimulation reward, whereas JJC8-016 (10-30 mg/kg i.p.) did not produce these effects. Strikingly, pretreatment with JJC8-016 dose-dependently inhibited cocaine-enhanced locomotion, cocaine self-administration, and cocaine-induced reinstatement of drug-seeking behavior, whereas R-MOD inhibited cocaine-induced reinstatement only at the high dose of 100 mg/kg. Notably, JJC8-016 alone neither altered extracellular dopamine in the nucleus accumbens nor maintained self-administration. It also failed to induce reinstatement of drug-seeking behavior. These findings suggest that JJC8-016 is a unique DAT inhibitor that has no cocaine-like abuse potential by itself. Moreover, pretreatment with JJC8-016 significantly inhibits cocaine-taking and cocaine-seeking behavior likely by interfering with cocaine binding to DAT. In addition, off-target actions may also contribute to its potential therapeutic utility in the treatment of cocaine abuse.

The limited impact that cocaine use patterns have on neurocognitive functioning in individuals with cocaine use disorder

It is well-documented in the literature that cocaine use is associated with neurocognitive impairment. The manner in which patterns of cocaine use, such as years of use, recent use over the past month, and daily amount of cocaine use, moderate neurocognition has been studied in a relatively piecemeal manner. Hence, the purpose of the study was to evaluate whether cocaine use patterns modulate neurocognition in individuals with cocaine use disorder. Cocaine users who were cocaine-negative ( n=125) were divided into tertiles based on cocaine use patterns and the performances of the highest and lowest groups were compared on the following cognitive measures: Continuous Performance Task-II, n-back, and Hopkins Verbal Learning Task-Revised. Participants with cocaine use disorder who used for more years (25.2±0.6 versus 10.1±0.6 years; mean±standard error of the mean) and who had more recent cocaine use over the past month (26.3±0.5 versus 6.0±0.6 days) did not differ significantly on any of the neurocognitive variables when compared to those with use patterns of shorter duration and less frequency (all p's >0.05). Lastly, participants reporting the greatest amount daily cocaine use (1.8±0.0 g) demonstrated better performance on an auditory working memory task when compared to those with the lowest daily use (0.7±0.0 g; p=0.04). While one might expect that individuals who used greater amounts of cocaine over longer periods of time would demonstrate relatively poorer performance on measures of neurocognition, particularly in the initial phase of abstinence, our findings did not confirm this. While speculative, a potential explanation for these findings is that after an individual uses cocaine for a certain number of years, or uses a specific amount over time, then the deleterious effects of cocaine on neurocognition stabilizes, and increased duration of cocaine use does not further exacerbate those impairments.

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.

A COMPARISON OF MAZUR'S k AND AREA UNDER THE CURVE FOR DESCRIBING STEEP DISCOUNTERS

Delay discounting describes how a reward loses value as a function of increasing delay to its receipt and has been reliably associated with a variety of vulnerable populations including those with substance use disorders (SUDs). Two commonly used models to assess delay discounting in the field of SUDs include log k derived from Mazur's hyperbolic equation and area under the curve (AUC). In the current study, we compared log k with AUC on delay discounting data obtained from non-treatment seeking, cocaine- and methamphetamine-dependent volunteers. We specifically chose this population in order to obtain a distribution of relatively steep discounters. The results show that the relationship between AUC and log k is better described by a quadratic rather than a linear function. In other words, changes in discounting, as measured by AUC and log k, are reflected differently across a range of obtained responses. Additionally, the distribution of AUC values was skewed, which appears to be more likely among populations exhibiting greater discounting. Finally, closer examination of indifference points revealed that AUC was almost perfectly predicted by the area from the two longest delays, with relatively less input from shorter delays. Given these results, researchers should exercise additional caution when deciding which method to assess discounting data and how final results are to be interpreted, particularly when dealing with relatively high rates of discounting. High rates of discounting are likely in populations with impulsive disorders such as those with SUDs.

Modafinil decreases cocaine choice in human cocaine smokers only when the response requirement and the alternative reinforcer magnitude are large

This study examined how response effort (pressing a keyboard button) for cocaine and the value of an alternative reinforcer (opportunity to play a game of chance for money) combined with 'free' cocaine (with no response effort) affected cocaine choice when participants were maintained on modafinil or placebo. Nontreatment-seeking current cocaine smokers were enrolled in a placebo-controlled, double-blind, within-subject study comprising both inpatient and outpatient phases. Participants were maintained on placebo capsules (0mg/day) during one inpatient phase and modafinil (300mg/day) capsules during another inpatient phase in counter-balanced order. A minimum of 8 medication-free days separated the two 15-day inpatient phases to allow for medication clearance. Under each medication condition participants had the opportunity to self-administer smoked cocaine (25mg) when the response effort for cocaine was low (500responses/dose) and had a low value alternative (2 game plays for money) or when the response effort for cocaine was large (2500responses/dose) and had a more valuable alternative (4 game plays for money). Under both conditions, participants received one free dose of cocaine (0, 12, 25 or 50mg) prior to making their first choice of the session. Fifteen individuals began the study and 7 completed it. Participants chose fewer cocaine doses when the response effort for cocaine and the alternative value was high (4.4±0.19) compared to when the response effort for cocaine and the alternative value was low (5.3±0.14). Providing individuals a free "priming" dose of cocaine prior to making their cocaine choice did not alter cocaine taking. Modafinil decreased cocaine choice only when the response effort for cocaine and the alternative value was high. These results suggest that modafinil may be most effective when combined with therapy emphasizing the large personal costs of using cocaine.

Pituitary Adenylate cyclase-activating polypeptide orchestrates neuronal regulation of the astrocytic glutamate-releasing mechanism system xc (.)

Glutamate signaling is achieved by an elaborate network involving neurons and astrocytes. Hence, it is critical to better understand how neurons and astrocytes interact to coordinate the cellular regulation of glutamate signaling. In these studies, we used rat cortical cell cultures to examine whether neurons or releasable neuronal factors were capable of regulating system xc (-) (Sxc), a glutamate-releasing mechanism that is expressed primarily by astrocytes and has been shown to regulate synaptic transmission. We found that astrocytes cultured with neurons or exposed to neuronal-conditioned media displayed significantly higher levels of Sxc activity. Next, we demonstrated that the pituitary adenylate cyclase-activating polypeptide (PACAP) may be a neuronal factor capable of regulating astrocytes. In support, we found that PACAP expression was restricted to neurons, and that PACAP receptors were expressed in astrocytes. Interestingly, blockade of PACAP receptors in cultures comprised of astrocytes and neurons significantly decreased Sxc activity to the level observed in purified astrocytes, whereas application of PACAP to purified astrocytes increased Sxc activity to the level observed in cultures comprised of neurons and astrocytes. Collectively, these data reveal that neurons coordinate the actions of glutamate-related mechanisms expressed by astrocytes, such as Sxc, a process that likely involves PACAP. A critical gap in modeling excitatory signaling is how distinct components of the glutamate system expressed by neurons and astrocytes are coordinated. In these studies, we found that system xc (-) (Sxc), a glutamate release mechanism expressed by astrocytes, is regulated by releasable neuronal factors including PACAP. This represents a novel form of neuron-astrocyte communication, and highlights the possibility that pathological changes involving astrocytic Sxc may stem from altered neuronal activity.

Genetic variation of the dopamine transporter (DAT1) influences the acute subjective responses to cocaine in volunteers with cocaine use disorders

OBJECTIVE

The aim of this study was to identify gene variants of DAT1 (SLC6A3) that modulate subjective responses to acute cocaine exposure.

METHODS

Non-treatment-seeking volunteers (n=66) with cocaine use disorders received a single bolus infusion of saline and cocaine (40 mg, intravenous) in a randomized order. Subjective effects were assessed with visual analog scales administered before (-15 min) and up to 20 min after infusion. Ratings of subjective effects were normalized to baseline, and saline infusion values were subtracted. Data were analyzed using repeated measures analysis of variance. DNA from the participants was genotyped for the DAT1 intron 8 (rs3836790) and 3'-untranslated region (rs28363170) variable number of tandem repeats.

RESULTS

Participants were mostly male (∼80%) and African American (∼70%). No differences were found among drug use variables between groups for either polymorphism. Carriers of the 9-allele of the DAT1 3'-untranslated region (9,9 and 9,10) exhibited greater responses to cocaine for 'high', 'any drug effect', 'anxious', and 'stimulated' (all P-values<0.001) compared with individuals homozygous for the 10-allele. For the intron 8 polymorphism, individuals homozygous for the 6-allele exhibited greater responses for 'anxious' compared with carriers of the 5-allele (P<0.001). Individuals possessing the genotype pattern of 10,10 and at least one 5-allele reported lower responses to 'good effects', 'bad effects', 'depressed', and 'anxious' (all P-values<0.01).

CONCLUSION

The data presented here show for the first time support for the hypothesis that genetic differences in DAT1 contribute to the variation in subjective responses to cocaine among participants with cocaine use disorders.

Cocaine choice procedures in animals, humans, and treatment-seekers: Can we bridge the divide?

Individuals with cocaine use disorder chronically self-administer cocaine to the detriment of other rewarding activities, a phenomenon best modeled in laboratory drug-choice procedures. These procedures can evaluate the reinforcing effects of drugs versus comparably valuable alternatives under multiple behavioral arrangements and schedules of reinforcement. However, assessing drug-choice in treatment-seeking or abstaining humans poses unique challenges: for ethical reasons, these populations typically cannot receive active drugs during research studies. Researchers have thus needed to rely on alternative approaches that approximate drug-choice behavior or assess more general forms of decision-making, but whether these alternatives have relevance to real-world drug-taking that can inform clinical trials is not well-understood. In this mini-review, we (A) summarize several important modulatory variables that influence cocaine choice in nonhuman animals and non-treatment seeking humans; (B) discuss some of the ethical considerations that could arise if treatment-seekers are enrolled in drug-choice studies; (C) consider the efficacy of alternative procedures, including non-drug-related decision-making and 'simulated' drug-choice (a choice is made, but no drug is administered) to approximate drug choice; and (D) suggest opportunities for new translational work to bridge the current divide between preclinical and clinical research.

Poorer Drinking Outcomes with Citalopram Treatment for Alcohol Dependence: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Previous research on the use of selective serotonin reuptake inhibitors (SSRIs) as a treatment for alcohol dependence has yielded mixed results. Depression has been shown to be a predictor of relapse and poor outcome following treatment, and it has been hypothesized that SSRIs would be beneficial in reducing drinking in depressed alcohol-dependent individuals. This randomized, double-blind, placebo-controlled trial was designed to test the effects of citalopram on treatment outcomes among alcohol-dependent individuals with and without depression.

METHODS

Two hundred and sixty-five patients meeting criteria for a DSM-IV diagnosis of alcohol abuse or dependence were randomly assigned to receive placebo or citalopram 20 mg per day for the first week, followed by 40 mg per day from weeks 2 through 12. All patients received a standard course of treatment consisting of weekly individual and group psychotherapy. Participants were reassessed at 12 weeks, including dropouts from both treatment groups to determine rates of abstinence, changes in alcohol use, addiction severity, depressive symptoms, and psychiatric status.

RESULTS

Citalopram provided no advantage over placebo in terms of treatment outcomes, and for some measures, citalopram produced poorer outcomes. Patients in the citalopram group had a higher number of heavy drinking days throughout the trial, and smaller changes in frequency and amount of alcohol consumption at 12 weeks. There was no influence of depression severity on outcomes in either medication group. Survival analyses also indicated no differences between depressed and nondepressed patients in the citalopram group for time to first slip or relapse. A diagnosis of personality disorder was associated with poorer treatment responses overall, regardless of treatment condition.

CONCLUSIONS

This trial does not support the use of citalopram in the treatment of alcohol dependence. The results suggest that the use of SSRIs among depressed and nondepressed alcohol-dependent individuals early in recovery, prior to the onset of abstinence, may be contraindicated.

Evaluation of the dopamine β-hydroxylase (DβH) inhibitor nepicastat in participants who meet criteria for cocaine use disorder

In the present study, we tested the hypothesis that the potent and selective dopamine-β-hydroxylase (DβH) inhibitor nepicastat would have minimal effects on cardiovascular and pharmacokinetic parameters associated with cocaine administration and would reduce the positive subjective effects produced by cocaine. We conducted a double-blind, placebo-controlled, inpatient study of oral nepicastat (0, 80 and 160mg) concurrent with intravenous (IV) cocaine (0, 10, 20 and 40mg) in non-treatment seeking participants who metcriteria for cocaine use disorder. Safety analyses revealed that nepicastat was well-tolerated and there were no differences in adverse events observed after nepicastat plus cocaine vs. cocaine alone. In addition, the pharmacokinetic properties of cocaine administration were not altered by nepicastat treatment. Cocaine-induced cardiovascular and subjective effects were evaluated for completers in the cohort randomized to nepicastat (n=13) using a within-subjects statistical analysis strategy. Specifically, the cardiovascular and subjective effects of cocaine were assessed in the presence of placebo (0mg), 80mg of nepicastat or 160mg of nepicastat on study Days 4, 8 and 12, respectively. Analyses revealed a main effect of nepicastat to reduce several cocaine-induced positive subjective effects. Taken together, these data indicate that nepicastat is safe when co-administered with cocaine and may suppress its positive subjective effects, and may be viable as a pharmacotherapy for treatment of cocaine use disorder.

Use of Preclinical Drug vs. Food Choice Procedures to Evaluate Candidate Medications for Cocaine Addiction

Drug addiction is a disease that manifests as an inappropriate allocation of behavior towards the procurement and use of the abused substance and away from other behaviors that produce more adaptive reinforcers (e.g. exercise, work, family and social relationships). The goal of treating drug addiction is not only to decrease drug-maintained behaviors, but also to promote a reallocation of behavior towards alternative, nondrug reinforcers. Experimental procedures that offer concurrent access to both a drug reinforcer and an alternative, nondrug reinforcer provide a research tool for assessment of medication effects on drug choice and behavioral allocation. Choice procedures are currently the standard in human laboratory research on medications development. Preclinical choice procedures have been utilized in biomedical research since the early 1940's, and during the last 10-15 years, their use for evaluation of medications to treat drug addiction has increased. We propose here that parallel use of choice procedures in preclinical and clinical studies will facilitate translational research on development of medications to treat cocaine addiction. In support of this proposition, a review of the literature suggests strong concordance between preclinical effectiveness of candidate medications to modify cocaine choice in nonhuman primates and rodents and clinical effectiveness of these medications to modify either cocaine choice in human laboratory studies or metrics of cocaine abuse in patients with cocaine use disorder. The strongest evidence for medication effectiveness in preclinical choice studies has been obtained with maintenance on the monoamine releaser d-amphetamine, a candidate agonist medication for cocaine use analogous to use of methadone to treat heroin abuse or nicotine formulations to treat tobacco dependence.

Modafinil in the treatment of crack-cocaine dependence in the Netherlands: Results of an open-label randomised controlled feasibility trial

BACKGROUND

Crack-cocaine dependence is a serious disorder with no approved pharmacological treatment. Modafinil is a promising medication with increased cocaine abstinence and reduced craving in some previous studies. In the present study, we examined the acceptance, safety and potential benefits of modafinil as an add-on treatment to cognitive behavioural therapy (CBT) in crack-cocaine dependent patients.

METHODS

Sixty-five crack-cocaine dependent outpatients participated in an open-label, randomised feasibility trial. Patients were randomised to receive either 12-week individual CBT plus 400 mg/day modafinil or 12-week individual CBT only. The primary outcome measure was CBT treatment retention. Secondary outcomes included modafinil adherence, tolerability and safety, use of cocaine and other substances, cocaine craving, health, social functioning and patient satisfaction.

RESULTS

Modafinil adherence was low, with only 10% treatment completers. Intent-to-treat analyses showed that modafinil did not improve CBT treatment retention or any of the secondary cocaine-related outcomes. Both groups showed similar, large reductions in cocaine use during the study treatment. Post hoc exploratory analyses within the CBT plus modafinil group showed significantly larger baseline to week 12 reductions in cocaine use days in high (⩾ 8 weeks) modafinil adherent patients.

CONCLUSIONS

Acceptance and benefits of modafinil were not demonstrated in the present study. Since reduction in cocaine use was observed in high modafinil adherent patients, further research in the treatment of cocaine dependence, in which modafinil adherence is optimised, is warranted.