New developments in the pharmacotherapy of cocaine abuse

The dopamine transporter antagonist vanoxerine inhibits G9a and suppresses cancer stem cell functions in colon tumors

Cancer stem cells (CSCs), functionally characterized by self-renewal and tumor-initiating activity, contribute to decreased tumor immunogenicity, while fostering tumor growth and metastasis. Targeting G9a histone methyltransferase (HMTase) effectively blocks CSC functions in colorectal tumors by altering pluripotent-like molecular networks; however, existing molecules directly targeting G9a HMTase activity failed to reach clinical stages due to safety concerns. Using a stem cell-based phenotypic drug-screening pipeline, we identified the dopamine transporter (DAT) antagonist vanoxerine, a compound with previously demonstrated clinical safety, as a cancer-specific downregulator of G9a expression. Here we show that gene silencing and chemical antagonism of DAT impede colorectal CSC functions by repressing G9a expression. Antagonizing DAT also enhanced tumor lymphocytic infiltration by activating endogenous transposable elements and type-I interferon response. Our study unveils the direct implication of the DAT-G9a axis in the maintenance of CSC populations and an approach to improve antitumor immune response in colon tumors.

Modifications to 1-(4-(2-Bis(4-fluorophenyl)methyl)sulfinyl)alkyl Alicyclic Amines That Improve Metabolic Stability and Retain an Atypical DAT Inhibitor Profile

Atypical dopamine transporter (DAT) inhibitors have shown therapeutic potential in the preclinical models of psychostimulant use disorders (PSUD). In rats, 1-(4-(2-((bis(4-fluorophenyl)methyl)sulfinyl)ethyl)-piperazin-1-yl)-propan-2-ol (JJC8-091, 3b) was effective in reducing the reinforcing effects of both cocaine and methamphetamine but did not exhibit psychostimulant behaviors itself. Improvements in DAT affinity and metabolic stability were desirable for discovering pipeline drug candidates. Thus, a series of 1-(4-(2-bis(4-fluorophenyl)methyl)sulfinyl)alkyl alicyclic amines were synthesized and evaluated for binding affinities at DAT and the serotonin transporter (SERT). Replacement of the piperazine with either a homopiperazine or a piperidine ring system was well tolerated at DAT (Ki range = 3-382 nM). However, only the piperidine analogues (20a-d) showed improved metabolic stability in rat liver microsomes as compared to the previously reported analogues. Compounds 12b and 20a appeared to retain an atypical DAT inhibitor profile, based on negligible locomotor activity in mice and molecular modeling that predicts binding to an inward-facing conformation of DAT.

Disulfiram for the treatment of cocaine dependence

BACKGROUND

Cocaine is a psychostimulant used by approximately 0.4% of the general population worldwide. Cocaine dependence is a chronic mental disorder characterised by the inability to control cocaine use and a host of severe medical and psychosocial complications. There is current no approved pharmacological treatment for cocaine dependence. Some researchers have proposed disulfiram, a medication approved to treat alcohol use disorder. This is an update of a Cochrane review first published in 2010.

OBJECTIVES

To evaluate the efficacy and safety of disulfiram for the treatment of cocaine dependence.

SEARCH METHODS

We updated our searches of the following databases to August 2022: the Cochrane Drugs and Alcohol Group Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL, and PsycINFO. We also searched for ongoing and unpublished studies via two trials registries. We handsearched the references of topic-related systematic reviews and included studies. The searches had no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials that evaluated disulfiram alone or associated with psychosocial interventions versus placebo, no intervention, other pharmacological interventions, or any psychosocial intervention for the treatment of cocaine dependence.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

Thirteen studies (1191 participants) met our inclusion criteria. Disulfiram versus placebo or no treatment Disulfiram compared to placebo may increase the number of people who are abstinent at the end of treatment (point abstinence; risk ratio (RR) 1.58, 95% confidence interval (CI) 1.05 to 2.36; 3 datasets, 142 participants; low-certainty evidence). However, compared to placebo or no pharmacological treatment, disulfiram may have little or no effect on frequency of cocaine use (standardised mean difference (SMD) -0.11 standard deviations (SDs), 95% CI -0.39 to 0.17; 13 datasets, 818 participants), amount of cocaine use (SMD -0.00 SDs, 95% CI -0.30 to 0.30; 7 datasets, 376 participants), continuous abstinence (RR 1.23, 95% CI 0.80 to 1.91; 6 datasets, 386 participants), and dropout for any reason (RR 1.20, 95% CI 0.92 to 1.55; 14 datasets, 841 participants). The certainty of the evidence was low for all these outcomes. We are unsure about the effects of disulfiram versus placebo on dropout due to adverse events (RR 12.97, 95% CI 0.77 to 218.37; 1 study, 67 participants) and on the occurrence of adverse events (RR 3.00, 95% CI 0.35 to 25.98), because the certainty of the evidence was very low for these outcomes. Disulfiram versus naltrexone Disulfiram compared with naltrexone may reduce the frequency of cocaine use (mean difference (MD) -1.90 days, 95% CI -3.37 to -0.43; 2 datasets, 123 participants; low-certainty evidence) and may have little or no effect on amount of cocaine use (SMD 0.12 SDs, 95% CI -0.27 to 0.51, 2 datasets, 123 participants; low-certainty evidence). We are unsure about the effect of disulfiram versus naltrexone on dropout for any reason (RR 0.86, 95% CI 0.56 to 1.32, 3 datasets, 131 participants) and dropout due to adverse events (RR 0.50, 95% CI 0.07 to 3.55; 1 dataset, 8 participants), because the certainty of the evidence was very low for these outcomes.

AUTHORS' CONCLUSIONS

Our results show that disulfiram compared to placebo may increase point abstinence. However, disulfiram compared to placebo or no pharmacological treatment may have little or no effect on frequency of cocaine use, amount of cocaine use, continued abstinence, and dropout for any reason. We are unsure if disulfiram has any adverse effects in this population. Caution is required when transferring our results to clinical practice.

PPL-103: A mixed opioid partial agonist with desirable anti-cocaine properties

Cocaine use disorder (CUD) is a persistent public health problem for which no effective medications are available. PPL-103 is an opioid receptor ligand with partial agonist activity at mu, kappa and delta opioid receptors, with a greater efficacy for kappa and low efficacy at mu receptors. Because chronic cocaine use induces changes in the kappa opioid receptor/dynorphin system, we hypothesized that a kappa partial agonist, such as PPL-103, would attenuate the aversive properties of the upregulated kappa system, resulting in effective treatment approach for CUD. We tested the effects of PPL-103 on cocaine self-administration models that recapitulate core aspects of CUD in humans. We found that PPL-103 reduced both long and short access cocaine self-administration, motivation to respond for cocaine, and binge-like cocaine taking, in rats. Operant responding for food, fentanyl and locomotor behavior were not altered at doses that decreased cocaine infusions. Repeated PPL-103 treatment did not lead to tolerance development. PPL-103 also reduced both priming- and cue-induced reinstatement of cocaine seeking, being more effective in the former. Surprisingly, PPL-103 reduced self-administration parameters and reinstatement in rats previously treated with the long-acting kappa receptor antagonist JDTic more potently than in non-JDTic treated animals, whereas naltrexone injected to rats subsequent to JDTic administration increased self-administration, suggesting that the partial mu agonist activity, rather than kappa agonism is important for reduction in cocaine taking and seeking. However, partial kappa activation seems to increase safety by limiting dysphoria, tolerance and addiction development. PPL-103 displays a desirable profile as a possible CUD pharmacotherapy.

Novel therapeutic compounds for prostate adenocarcinoma treatment: An analysis using bioinformatic approaches and the CMap database

INTRODUCTION

Prostate adenocarcinoma is the most frequently diagnosed malignancy, particularly for people >70 years old. The main challenge in the treatment of advanced neoplasm is bone metastasis and therapeutic resistance for known oncology drugs. Novel treatment methods to prolong the survival time and improve the life quality of these specific patients are required. The present study attempted to screen potential therapeutic compounds for the tumor through bioinformatics approaches, in order to provide conceptual treatment for this malignant disease.

METHODS

Differentially expressed genes were obtained from the Gene Expression Omnibus database and submitted into the Connectivity Map database for the detection of potentially associated compounds. Target genes were extracted from the search results. Functional annotation and pathway enrichment were performed for the confirmation. Survival analysis was used to measure potential therapeutic effects.

RESULTS

It was revealed that 3 compounds (vanoxerine, tolnaftate, and gabexate) may help to prolong the disease-free survival time from tumor metastasis of patients with the tumor. A total of 6 genes [also-keto reductase family 1 member C3 (AKR1C3), collagen type III α 1 chain (COL3A1), lipoprotein lipase (LPL), glucuronidase, β pseudogene 11 (GUSBP11), apolipoprotein E (APOE), and collagen type I α 1 chain (COL1A1)] were identified to be the potential therapeutic targets for the aforementioned compounds.

CONCLUSION

In the present study, it was speculated that 3 compounds may function as the potential therapeutic drugs of bone metastatic prostate adenocarcinoma; however, further studies verifying vitro and in vivo are necessary.

Structure-Activity Relationships for a Series of (Bis(4-fluorophenyl)methyl)sulfinyl Alkyl Alicyclic Amines at the Dopamine Transporter: Functionalizing the Terminal Nitrogen Affects Affinity, Selectivity, and Metabolic Stability

Atypical dopamine transporter (DAT) inhibitors have shown therapeutic potential in preclinical models of psychostimulant abuse. In rats, 1-(4-(2-((bis(4-fluorophenyl)methyl)sulfinyl)ethyl)-piperazin-1-yl)-propan-2-ol (3b) was effective in reducing the reinforcing effects of both cocaine and methamphetamine but did not exhibit psychostimulant behaviors itself. While further development of 3b is ongoing, diastereomeric separation, as well as improvements in potency and pharmacokinetics were desirable for discovering pipeline drug candidates. Thus, a series of bis(4-fluorophenyl)methyl)sulfinyl)alkyl alicyclic amines, where the piperazine-2-propanol scaffold was modified, were designed, synthesized, and evaluated for binding affinities at DAT, as well as the serotonin transporter and σ₁ receptors. Within the series, 14a showed improved DAT affinity (K_i = 23 nM) over 3b (K_i = 230 nM), moderate metabolic stability in human liver microsomes, and a hERG/DAT affinity ratio = 28. While 14a increased locomotor activity relative to vehicle, it was significantly lower than activity produced by cocaine. These results support further investigation of 14a as a potential treatment for psychostimulant use disorders.

Novel technologies in detection, treatment and prevention of substance use disorders

Substance use disorders are a widely recognized problem, which affects various levels of communities and influenced the world socioeconomically. Its source is deeply embedded in the global population. In order to fight against such an adversary, governments have spared no efforts in implementing substance abuse treatment centers and funding research to develop treatments and prevention procedures. In this review, we will discuss the use of immunological-based treatments and detection kit technologies. We will be detailing the steps followed to produce performant antibodies (antigens, carriers, and adjuvants) focusing on cocaine and methamphetamine as examples. Furthermore, part of this review is dedicated to substance use detection. Owing to novel technologies such as bio-functional polymeric surfaces and biosensors manufacturing, detection has become a more convenient method with the fast and on-site developed devices. Commercially available devices are able to test substance use disorders in urine, saliva, hair, and sweat. This improvement has had a tremendous impact on the prevention of driving under influence and other illicit behaviors. Lastly, substance abuse became a major issue involving the cooperation of experts on all levels to devise better treatment programs and prevent abuse-based accidents, injury and death.

Granulocyte-Colony-Stimulating Factor Alters the Proteomic Landscape of the Ventral Tegmental Area

Cocaine addiction is characterized by aberrant plasticity of the mesolimbic dopamine circuit, leading to dysregulation of motivation to seek and take drug. Despite the significant toll that cocaine use disorder exacts on society, there are currently no available pharmacotherapies. We have recently identified granulocyte-colony stimulating factor (G-CSF) as a soluble cytokine that alters the behavioral response to cocaine and which increases dopamine release from the ventral tegmental area (VTA). Despite these known effects on behavior and neurophysiology, the molecular mechanisms by which G-CSF affects brain function are unclear. In this study mice were treated with repeated injections of G-CSF, cocaine or a combination and changes in protein expression in the VTA were examined using an unbiased proteomics approach. Repeated G-CSF treatment resulted in alterations in multiple signaling pathways related to synaptic plasticity and neuronal morphology. While the treatment groups had marked overlap in their effect, injections of cocaine and the combination of cocaine and G-CSF lead to distinct patterns of significantly regulated proteins. These experiments provide valuable information as to the molecular pathways that G-CSF activates in an important limbic brain region and will help to guide further characterization of G-CSF function and evaluation as a possible translational target.

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.

Novel and High Affinity 2-[(Diphenylmethyl)sulfinyl]acetamide (Modafinil) Analogues as Atypical Dopamine Transporter Inhibitors

The development of pharmacotherapeutic treatments of psychostimulant abuse has remained a challenge, despite significant efforts made toward relevant mechanistic targets, such as the dopamine transporter (DAT). The atypical DAT inhibitors have received attention due to their promising pharmacological profiles in animal models of cocaine and methamphetamine abuse. Herein, we report a series of modafinil analogues that have an atypical DAT inhibitor profile. We extended SAR by chemically manipulating the oxidation states of the sulfoxide and the amide functional groups, halogenating the phenyl rings, and/or functionalizing the terminal nitrogen with substituted piperazines, resulting in several novel leads such as 11b, which demonstrated high DAT affinity (K_i = 2.5 nM) and selectivity without producing concomitant locomotor stimulation in mice, as compared to cocaine. These results are consistent with an atypical DAT inhibitor profile and suggest that 11b may be a potential lead for development as a psychostimulant abuse medication.

Treatment-refractory substance use disorder: Focus on alcohol, opioids, and cocaine

Substance use disorders are common, but only a small minority of patients receive adequate treatment. Although psychosocial therapies are effective, relapse is common. This review focusses on novel pharmacological and other treatments for patients with alcohol, opioid, or cocaine use disorders who do not respond to conventional treatments. Disulfiram, acamprosate, and the opioid antagonist naltrexone have been approved for the treatment of alcoholism. A novel, "as needed" approach is the use of the mu-opioid antagonist and partial kappa agonist nalmefene to reduce alcohol consumption. Other novel pharmacological approaches include the GABA-B receptor agonist baclofen, anticonvulsants such as topiramate and gabapentin, the partial nicotine receptor agonist varenicline, and other drugs. For opioid dependence, opioid agonist therapy with methadone or buprenorphine is the first-line treatment option. Other options include oral or depot naltrexone, morphine sulfate, depot or implant formulations, and heroin (diacetylmorphine) in treatment-refractory patients. To date, no pharmacological treatment has been approved for cocaine addiction; however, 3 potential pharmacological treatments are being studied, disulfiram, methylphenidate, and modafinil. Pharmacogenetic approaches may help to optimize treatment response in otherwise treatment-refractory patients and to identify which patients are more likely to respond to treatment, and neuromodulation techniques such as repeated transcranial magnetic stimulation and deep brain stimulation also may play a role in the treatment of substance use disorders. Although no magic bullet is in sight for treatment-refractory patients, some novel medications and brain stimulation techniques have the potential to enrich treatment options at least for some patients.

Distinct behavioral and immunoendocrine parameters during crack cocaine abstinence in women reporting childhood abuse and neglect

AIM

To assess plasma levels of cortisol and cytokines between cocaine-dependent women with and without childhood maltreatment (CM) history during cocaine detoxification treatment.

METHOD

We assessed immunoendocrine and clinical parameters of 108 crack cocaine female users during 3 weeks of inpatient detoxification treatment, and 24 healthy women to obtain reference values. Women with (CM+, n=53) or without (CM-, n=55) CM history were identified answering the Childhood Trauma Questionnaire (CTQ). Blood samples and clinical assessment were collected before lunch during the first, second and third week post-treatment admission. Flow cytometry was used to assess TNF-α, IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-17A plasma levels and ELISA assay was used to measure plasma cortisol levels.

RESULTS

At baseline, lower Th1 and Th17-related cytokines levels and higher Th2 cytokines levels were observed in crack cocaine users compared with reference values. Cytokines levels of cocaine dependents gradually became closer to reference values along detoxification treatment. However, when CM+ and CM- groups were compared, increased levels of IL-6, IL-4 and TNF-α across time were observed in CM+ group only. Additionally, a Th1/Th2 immune imbalance was observed within CM+ group, which was negatively correlated with the severity of the crack withdrawal. Finally, loading trauma exposure severity, immunoendocrine and clinical parameters in factor analysis, we identified three clusters of observed variables during detoxification: (1) systemic immunity and trauma exposure, (2) pro-inflammatory immunity and (3) behavior

CONCLUSION

Our results suggest the existence of an immunological phenotype variant associated with CM exposure during crack cocaine detoxification of women.

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.

Identifying Medication Targets for Psychostimulant Addiction: Unraveling the Dopamine D3 Receptor Hypothesis

The dopamine D3 receptor (D3R) is a target for developing medications to treat substance use disorders. D3R-selective compounds with high affinity and varying efficacies have been discovered, providing critical research tools for cell-based studies that have been translated to in vivo models of drug abuse. D3R antagonists and partial agonists have shown especially promising results in rodent models of relapse-like behavior, including stress-, drug-, and cue-induced reinstatement of drug seeking. However, to date, translation to human studies has been limited. Herein, we present an overview and illustrate some of the pitfalls and challenges of developing novel D3R-selective compounds toward clinical utility, especially for treatment of cocaine abuse. Future research and development of D3R-selective antagonists and partial agonists for substance abuse remains critically important but will also require further evaluation and development of translational animal models to determine the best time in the addiction cycle to target D3Rs for optimal therapeutic efficacy.

Synthesis and κ-opioid receptor activity of furan-substituted salvinorin A analogues

The neoclerodane diterpene salvinorin A, found in the leaves of Salvia divinorum, is a potent κ-opioid receptor agonist, making it an attractive scaffold for development into a treatment for substance abuse. Although several successful semisynthetic studies have been performed to elucidate structure-activity relationships, the lack of analogues with substitutions to the furan ring of salvinorin A has prevented a thorough understanding of its role in binding to the κ-opioid receptor. Herein we report the synthesis of several salvinorin A derivatives with modified furan rings. Evaluation of these compounds in a functional assay indicated that sterically less demanding substitutions are preferred, suggesting the furan ring is bound in a congested portion of the binding pocket. The most potent of the analogues successfully reduced drug-seeking behavior in an animal model of drug-relapse without producing the sedation observed with other κ-opioid agonists.

Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis

AIMS

Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. Here, we synthesised published results to determine whether inhibitory ability is reliably impaired in substance users compared to controls.

METHODS

The meta-analysis used fixed-effects models to integrate results from 97 studies that compared groups with heavy substance use or addiction-like behaviours with healthy control participants on two experimental paradigms commonly used to assess response inhibition: the Go/NoGo task, and the Stop-Signal Task (SST). The primary measures of interest were commission errors to NoGo stimuli and stop-signal reaction time in the SST. Additionally, we examined omission errors to Go stimuli, and reaction time in both tasks. Because inhibition is more difficult when inhibition is required infrequently, we considered papers with rare and equiprobable NoGo stimuli separately.

RESULTS

Inhibitory deficits were apparent for heavy use/dependence on cocaine, MDMA, methamphetamine, tobacco, and alcohol (and, to a lesser extent, non-dependent heavy drinkers), and in pathological gamblers. On the other hand, no evidence for an inhibitory deficit was observed for opioids or cannabis, and contradictory evidence was observed for internet addiction.

CONCLUSIONS

The results are generally consistent with the view that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control. Implications for treatment of substance use are discussed, along with suggestions for future research arising from the limitations of the extant literature.

Treatment of crack-cocaine dependence with topiramate: a randomized controlled feasibility trial in The Netherlands

BACKGROUND

Crack-cocaine dependence is a complex disorder with limited treatment options. Topiramate is one of the promising medications with reported reductions in cocaine use and craving in former studies. The present study evaluated the acceptance and effectiveness of topiramate as an add-on to cognitive behavioral therapy (CBT) in crack-cocaine dependent patients.

METHODS

Seventy-four crack-cocaine dependent outpatients participated in an open-label, randomized feasibility trial. They were randomized to receive either 12-week CBT plus topiramate (200mg/day) or 12-week CBT only. The primary outcome measure was treatment retention. Secondary outcomes included medication adherence, safety, cocaine and other substance use, health, social functioning, and patient satisfaction.

RESULTS

Adherence to topiramate treatment was low. In the intent-to-treat analyses, topiramate neither improved treatment retention nor reduced cocaine and other substance use. Post hoc, exploratory analyses suggested a moderation effect of comorbid opioid dependence, with a significant effect of topiramate on cocaine use reduction only in crack-cocaine dependent patients with comorbid opioid dependence.

CONCLUSIONS

Topiramate was safe and well-tolerated in this sample of crack-cocaine dependent patients, but efficacy was not supported probably due to low acceptance of the treatment. Given the equivocal results of previous studies and the negative findings in our study, the potential of topiramate in the treatment of cocaine dependence seems limited.

Pharmacological evidence for an abstinence-induced switch in 5-HT1B receptor modulation of cocaine self-administration and cocaine-seeking behavior

Studies examining serotonin-1B (5-HT_1B) receptor manipulations on cocaine self-administration and cocaine-seeking behavior initially seemed discrepant. However, we recently suggested based on viral-mediated 5-HT_1B-receptor gene transfer that the discrepancies are likely due to differences in the length of abstinence from cocaine prior to testing. To further validate our findings pharmacologically, we examined the effects of the selective 5-HT_1B receptor agonist CP 94,253 (5.6 mg/kg, s.c.) on cocaine self-administration during maintenance and after a period of protracted abstinence with or without daily extinction training. We also examined agonist effects on cocaine-seeking behavior at different time points during abstinence. During maintenance, CP 94,253 shifted the cocaine self-administration dose–effect function on an FR5 schedule of reinforcement to the left, whereas following 21 days of abstinence CP 94,253 downshifted the function and also decreased responding on a progressive ratio schedule of reinforcement regardless of extinction history. CP 94,253 also attenuated cue-elicited and cocaine-primed drug-seeking behavior following 5 days, but not 1 day, of forced abstinence. The attenuating effects of CP 94,253 on the descending limb of the cocaine dose–effect function were blocked by the selective 5-HT_1B receptor antagonist SB 224289 (5 mg/kg, i.p.) at both time points, indicating 5-HT_1B receptor mediation. The results support a switch in 5-HT_1B receptor modulation of cocaine reinforcement from facilitatory during self-administration maintenance to inhibitory during protracted abstinence. These findings suggest that the 5-HT_1B receptor may be a novel target for developing medication for treating cocaine dependence.

Reduction of the reinforcing effectiveness of cocaine by continuous D-amphetamine treatment in rats: importance of active self-administration during treatment period

RATIONALE

Continuous administration of D-amphetamine has shown promise as a treatment for psychostimulant addiction. In rodent studies, constant infusion of D-amphetamine (5 mg/kg/day) has been shown to reduce cocaine-reinforced responding in the dose range of 0.19-0.75 mg/kg/inf.

OBJECTIVES

The present study tested whether these effects were a reflection of pharmacological interactions between D-amphetamine and cocaine or if they resulted from associative learning mechanisms

METHODS

After stable progressive ratio (PR) baselines were established, rats were implanted with subcutaneous osmotic minipumps filled with either D-amphetamine (5 mg/kg/day-groups 1 and 2) or saline (group 3). During the treatment period, groups 1 and 3 self-administered cocaine at a dose that was previously shown to produce the most robust effects in combination with D-amphetamine treatment (0.19 mg/kg/inf), while group 2 received passive cocaine infusions.

RESULTS

In replication of previous studies, D-amphetamine treatment resulted in a significant (35 %) decrease in breakpoints relative to saline controls. By contrast, no reductions in breakpoints were observed in animals that received passive cocaine infusions during the treatment period (group 2).

CONCLUSIONS

Active self-administration of cocaine during the treatment period appears to be an important factor in reducing cocaine-reinforced breakpoints. These findings suggest learning mechanisms are involved in the therapeutic effects of continuous D-amphetamine, and pharmacological interaction mechanisms such as cross-tolerance cannot completely account for the observed decreases in cocaine seeking.

Chlorophenylpiperazine analogues as high affinity dopamine transporter ligands

Selective σ2 ligands continue to be an active target for medications to attenuate the effects of psychostimulants. In the course of our studies to determine the optimal substituents in the σ2-selective phenyl piperazines analogues with reduced activity at other neurotransmitter systems, we discovered that 1-(3-chlorophenyl)-4-phenethylpiperazine actually had preferentially increased affinity for dopamine transporters (DAT), yielding a highly selective DAT ligand.

Dopamine D3 and 5-HT1B receptor dysregulation as a result of psychostimulant intake and forced abstinence: Implications for medications development

Addiction to psychostimulants, including cocaine and amphetamine, is associated with dysregulation of dopamine and serotonin (5-HT) neurotransmitter systems. Neuroadaptations in these systems vary depending on the stage of the drug taking-abstinence-relapse cycle. Consequently, the effects of potential treatments that target these systems may vary depending on whether they are given during abstinence or relapse. In this review, we discuss evidence that dopamine D3 receptors (D3Rs) and 5-HT1B receptors (5-HT1BRs) are dysregulated in response to both chronic psychostimulant use and subsequent abstinence. We then review findings from preclinical self-administration models which support targeting D3Rs and 5-HT1BRs as potential medications for psychostimulant dependence. Potential side effects of the treatments are discussed and attention is given to studies reporting positive treatment outcomes that depend on: 1) whether testing occurs during self-administration versus abstinence, 2) whether escalation of drug self-administration has occurred, 3) whether the treatments are given repeatedly, and 4) whether social factors influence treatment outcomes. We conclude that D3/D2 agonists may decrease psychostimulant intake; however, side effects of D3/D2R full agonists may limit their therapeutic potential, whereas D3/D2R partial agonists have fewer undesirable side effects. D3-selective antagonists may not reduce psychostimulant intake during relapse, but nonetheless, may decrease motivation for seeking psychostimulants with relatively few side-effects. 5-HT1BR agonists provide a striking example of treatment outcomes that are dependent on the stage of the addiction cycle. Specifically, these agonists initially increase cocaine's reinforcing effects during maintenance of self-administration, but after a period of abstinence they reduce psychostimulant seeking and the resumption of self-administration. In conclusion, we suggest that factors contributing to dysregulation of monoamine systems, including drug history, abstinence, and social context, should be considered when evaluating potential treatments to better model treatment effects in humans. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

S-(N, N-diethylcarbamoyl)glutathione (carbamathione), a disulfiram metabolite and its effect on nucleus accumbens and prefrontal cortex dopamine, GABA, and glutamate: a microdialysis study

Disulfiram (DSF), used for the treatment of alcohol use disorders (AUDs) for over six decades, most recently has shown promise for treating cocaine dependence. Although DSF's mechanism of action in alcohol abuse is due to the inhibition of liver mitochondrial aldehyde dehydrogenase (ALDH2), its mechanism of action in the treatment of cocaine dependence is unknown. DSF is a pro-drug, forming a number of metabolites each with discrete pharmacological actions. One metabolite formed during DSF bioactivation is S-(N, N-diethylcarbamoyl) glutathione (carbamathione) (carb). We previously showed that carb affects glutamate binding. In the present studies, we employed microdialysis techniques to investigate the effect of carb administration on dopamine (DA), GABA, and glutamate (Glu) in the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), two brain regions implicated in substance abuse dependence. The effect of DSF on DA, GABA, and Glu in the NAc also was determined. Both studies were carried out in male rats. Carb (20, 50, 200 mg/kg i v) in a dose-dependent manner increased DA, decreased GABA, and had a biphasic effect on Glu, first increasing and then decreasing Glu in both the NAc and mPFC. These changes all occurred concurrently. After carb administration, NAc and mPFC carb, as well as carb in plasma, were rapidly eliminated with a half-life for each approximately 4 min, while the changes in DA, GABA, and GLu in the NAc and mPFC persisted for approximately two hours. The maximal increase in carb (Cmax) in the NAc and mPFC after carb administration was dose-dependent, as was the area under the curve (AUC). DSF (200 mg/kg i p) also increased DA, decreased GABA, and had a biphasic effect on Glu in the NAc similar to that observed in the NAc after carb administration. When the cytochrome P450 inhibitor N-benzylimidazole (NBI) (20 mg/kg i p) was administered before DSF dosing, no carb could be detected in the NAc and plasma and also no changes in NAc DA, GABA, and GLu occurred. Changes in these neurotransmitters occurred only if carb was formed from DSF. When NBI was administered prior to dosing with carb, the increase in DA, decrease in GABA, and biphasic effect on GLu was similar to that seen after dosing with carb only. The i p or i v administration of carb showed similar changes in DA, GABA, and GLu, except the time to reach Cmax for DA as well as the changes in GABA, and GLu after i p administration occurred later. The elimination half-life of carb and the area under the curve (AUC) were similar after both routes of administration. It is concluded that carb must be formed from DSF before any changes in DA, GABA, and GLu in the NAc and mPFC are observed. DSF and carb, when administered to rats, co-release DA, GABA, and GLu. Carb, once formed can cross the blood brain barrier and enter the brain. Although inhibition of liver ALDH2 is the accepted mechanism for DSF's action in treating AUDs, the concurrent changes in DA, GABA, and GLu in the NAc and mPFC after DSF administration suggest that changes in these neurotransmitters as a potential mechanism of action not only for AUDs, but also for cocaine dependence cannot be excluded.

Pregabalin reduces cocaine self-administration and relapse to cocaine seeking in the rat

Pregabalin (Lyrica™) is a structural analog of γ-aminobutyric acid (GABA) and is approved by the FDA for partial epilepsy, neuropathic pain and generalized anxiety disorders. Pregabalin also reduces excitatory neurotransmitter release and post-synaptic excitability. Recently, we demonstrated that pregabalin reduced alcohol intake and prevented relapse to the alcohol seeking elicited by stress or environmental stimuli associated with alcohol availability. Here, we sought to extend these findings by examining the effect of pregabalin on cocaine self-administration (0.25 mg/infusion) and on cocaine seeking elicited by both conditioned stimuli and stress, as generated by administration of yohimbine (1.25 mg/kg). The results showed that oral administration of pregabalin (0, 10 or 30 mg/kg) reduced self-administration of cocaine over an extended period (6 hours), whereas it did not modify self-administration of food. In cocaine reinstatement studies, pregabalin (10 and 30 mg/kg) abolished the cocaine seeking elicited by both the pharmacological stressor yohimbine and the cues predictive of cocaine availability. Overall, these results demonstrate that pregabalin may have potential in the treatment of some aspects of cocaine addiction.

AAVrh.10-mediated expression of an anti-cocaine antibody mediates persistent passive immunization that suppresses cocaine-induced behavior

Cocaine addiction is a major problem affecting all societal and economic classes for which there is no effective therapy. We hypothesized an effective anti-cocaine vaccine could be developed by using an adeno-associated virus (AAV) gene transfer vector as the delivery vehicle to persistently express an anti-cocaine monoclonal antibody in vivo, which would sequester cocaine in the blood, preventing access to cognate receptors in the brain. To accomplish this, we constructed AAVrh.10antiCoc.Mab, an AAVrh.10 gene transfer vector expressing the heavy and light chains of the high affinity anti-cocaine monoclonal antibody GNC92H2. Intravenous administration of AAVrh.10antiCoc.Mab to mice mediated high, persistent serum levels of high-affinity, cocaine-specific antibodies that sequestered intravenously administered cocaine in the blood. With repeated intravenous cocaine challenge, naive mice exhibited hyperactivity, while the AAVrh.10antiCoc.Mab-vaccinated mice were completely resistant to the cocaine. These observations demonstrate a novel strategy for cocaine addiction by requiring only a single administration of an AAV vector mediating persistent, systemic anti-cocaine passive immunity.

Protracted withdrawal from cocaine self-administration flips the switch on 5-HT(1B) receptor modulation of cocaine abuse-related behaviors

BACKGROUND

The role of serotonin-1B receptors (5-HT(1B)Rs) in modulating cocaine abuse-related behaviors has been controversial due to discrepancies between pharmacological and gene knockout approaches and opposite influences on cocaine self-administration versus cocaine-seeking behavior. We hypothesized that modulation of these behaviors via 5-HT(1B)Rs in the mesolimbic pathway may vary depending on the stage of the addiction cycle.

METHODS

To test this hypothesis, we examined the effects of increasing 5-HT(1B)R production by microinfusing a viral vector expressing either green fluorescent protein and 5-HT(1B)R or green fluorescent protein alone into the medial nucleus accumbens shell of rats either during maintenance of cocaine self-administration (i.e., active drug use) or during protracted withdrawal.

RESULTS

5-HT(1B)R receptor gene transfer during maintenance shifted the dose-response curve for cocaine self-administration upward and to the left and increased breakpoints and cocaine intake on a progressive ratio schedule, consistent with enhanced reinforcing effects of cocaine. In contrast, following 21 days of forced abstinence, 5-HT(1B)R gene transfer attenuated breakpoints and cocaine intake on a progressive ratio schedule of reinforcement, as well as cue- and cocaine-primed reinstatement of cocaine-seeking behavior.

CONCLUSIONS

This unique pattern of effects suggests that mesolimbic 5-HT(1B)Rs differentially modulate cocaine abuse-related behaviors, with a facilitative influence during periods of active drug use, in striking contrast to an inhibitory influence during protracted withdrawal. These findings suggest that targeting 5-HT(1B)Rs may lead to a novel treatment for cocaine dependence and that the therapeutic efficacy of these treatments may vary depending on the stage of the addiction cycle.

Treatment of cocaine withdrawal anxiety with guanfacine: relationships to cocaine intake and reinstatement of cocaine seeking in rats

RATIONALE

Successful treatment of cocaine addiction is severely impeded by the propensity of users to relapse. Withdrawal severity may serve as a key predictor of susceptibility to relapse. Therefore, the identification and treatment of cocaine withdrawal symptoms such as anxiety may improve addiction treatment outcome.

OBJECTIVES

The current study examined the role of anxiety-like behavior during cocaine withdrawal and anxiolytic treatment in reinstatement of cocaine seeking in an animal model of relapse.

METHODS

Male rats experienced daily IV cocaine self-administration. One group of animals received the norepinephrine α-2 agonist, guanfacine, or vehicle prior to anxiety testing 48 h after the last self-administration session. In the second group of rats, relationships between cocaine intake, anxiety-like behavior after withdrawal of cocaine, and reinstatement responding were investigated. The third and fourth groups of animals received guanfacine, yohimbine (norepinephrine α-2 antagonist), or vehicle once per day for 3 days 48 h after cessation of cocaine self-administration, followed by extinction and subsequent reinstatement induced by cocaine injections, cocaine-paired cues, and yohimbine administration.

RESULTS

Cocaine-withdrawn rats at 48 h demonstrated higher levels of anxiety-like behavior as measured on a defensive burying task when compared to yoked saline controls, an effect reversed by guanfacine treatment. Cocaine intake was positively correlated with measures of anxiety-like behavior during early withdrawal, and this anxiety-like behavior was significantly correlated with subsequent cocaine-primed reinstatement. Yohimbine treatment during early withdrawal increased reinstatement to conditioned cues, while guanfacine treatment reduced reinstatement to yohimbine.

CONCLUSIONS

These studies suggest an important role for noradrenergic mediation of anxiety-like behavior that emerges after withdrawal of cocaine and potential risk of relapse as modeled by reinstatement, and suggest that treatment of anxiety symptoms during early abstinence may reduce the risk of relapse.

Diazepam promotes choice of abstinence in cocaine self-administering rats

When facing a choice between cocaine and a potent, albeit inessential, non-drug alternative (i.e. water sweetened with saccharin), most cocaine self-administering rats abstain from cocaine in favor of the non-drug pursuit, regardless of the dose available and even after extended drug use. Only a minority continues to take the drug despite the opportunity of making a different choice and increasing stakes. This pattern of individual variation could suggest that the majority of rats are resilient to addiction, taking cocaine by default of other options. Only a minority would be vulnerable to addiction. This study tested the hypothesis that rats choose to refrain from cocaine self-administration because cocaine would be conflictual, having both rewarding and anxiogenic properties. Contrary to this hypothesis, however, we report here that diazepam-a broad-spectrum benzodiazepine anxiolytic-did not decrease, but instead, further increased cocaine abstinence. Interestingly, although diazepam decreased locomotion, rats adapted to this effect by spending more time near the lever associated with the preferred reward, a behavior that minimized the need for locomotion at the moment of choice. When responding for cocaine or saccharin was analyzed separately, we found that diazepam decreased responding for cocaine without affecting responding for saccharin. Finally, the abstinence-promoting effects of diazepam were also induced in cocaine-preferring rats treated chronically with diazepam. Overall, this study demonstrates that abstinence from cocaine cannot be explained away by the anxiogenic effects of cocaine, thereby reinforcing the notion of resilience to addiction. It also supports the use of benzodiazepines in the treatment of cocaine addiction.

Cocaine Addiction Treatments to improve Control and reduce Harm (CATCH): new pharmacological treatment options for crack-cocaine dependence in the Netherlands

BACKGROUND

Cocaine, particularly in its base form ('crack'), has become one of the drugs of most concern in the Netherlands, being associated with a wide range of medical, psychiatric and social problems for the individual, and with significant public order consequences for society. Available treatment options for cocaine dependent users are limited, and a substantial part of the cocaine dependent population is not reached by the addiction treatment system. Psychosocial interventions for cocaine dependence generally show modest results, and there are no registered pharmacological treatments to date, despite the wide range of medications tested for this type of dependence. The present study (Cocaine Addiction Treatments to improve Control and reduce Harm; CATCH) investigates the possibilities and problems associated with new pharmacological treatments for crack dependent patients.

METHODS/DESIGN

The CATCH-study consists of three separate randomised controlled, open-label, parallel-group feasibility trials, conducted at three separate addiction treatment institutes in the Netherlands. Patients are either new referrals or patients already in treatment. A total of 216 eligible outpatients are randomised using pre-randomisation double-consent design and receive either 12 weeks treatment with oral topiramate (n = 36; Brijder Addiction Treatment, The Hague), oral modafinil (n = 36; Arkin, Amsterdam), or oral dexamphetamine sustained-release (n = 36; Bouman GGZ, Rotterdam) as an add-on to cognitive behavioural therapy (CBT), or receive a 12-week CBT only (controls: n = 3 × 36). Primary outcome in these feasibility trials is retention in the underlying psychosocial treatment (CBT). Secondary outcomes are acceptance and compliance with the study medication, safety, changes in cocaine (and other drug) use, physical and mental health, social functioning, and patient satisfaction.

DISCUSSION

To date, the CATCH-study is the first study in the Netherlands that explores new treatment options for crack-cocaine dependence focusing on both abstinence and harm minimisation. It is expected that the study will contribute to the development of new treatments for one of the most problematic substance use disorders.

TRIAL REGISTRATION

The Netherlands National Trial Register NTR2576The European Union Drug Regulating Authorities Clinical Trials EudraCT2009-010584-16.

Progress in HIV reduction and prevention among injection and noninjection drug users

Substantial progress has been made in reducing HIV among injection drug users (IDUs) in the United States, despite political and social resistance that reduced resources and restricted access to services. The record for HIV prevention among noninjecting drug users is less developed, although they are more numerous than IDUs. Newer treatments for opiate and alcohol abuse can now be integrated into primary HIV care; treatment for stimulant abuse is less developed. All drug users present challenges for newer HIV prevention strategies (eg, "test and treat," nonoccupational postexposure prophylaxis and preexposure prophylaxis, contingency management, and conditional cash transfer). A comprehensive HIV prevention program that includes multicomponent multilevel approaches (ie, individual, network, structural) has been effective in HIV prevention among IDUs. Expanding these approaches to noninjecting drug users, especially those at highest risk (eg, minority men who have sex with men) and incorporating these newer approaches is a public health priority.

Pharmacotherapy for substance abuse disorders in adolescence

The public health effects of adolescent substance abuse disorders (SUD) reaches further than the immediate intoxicating effects. Medications play a limited role in the treatment of youth beyond addressing short-term symptoms but may improve longer-term outcomes for some patients. Given the potential devastating consequences of SUD, clinicians should become familiar with all available treatment options. This article reviews the pharmacotherapy for adolescent SUD to inform clinicians considering the use of this modality for selected groups of patients.

Attenuation of reinforcing and psychomotor stimulant effects of amphetamine by aripiprazole

Partial dopamine agonists are potential medications for the treatment of amphetamine addiction. They have been hypothesized to stabilize the dopamine system by acting as antagonists during high dopaminergic tone resulting from amphetamine use and as agonists during withdrawal. Aripiprazole is an atypical antipsychotic that acts as a partial D2 dopamine and a serotonin 5-HT₁(A) agonist and a serotonin 5-HT₂(A) antagonist. The aim of the present study was to examine the effects of aripiprazole on behaviors induced and maintained by d-amphetamine. To this end, intravenous d-amphetamine self-administration [fixed ratio 3 (FR3) schedule, 0.02 mg/infusion] and d-amphetamine-induced (0, 1.5 mg/kg intraperitoneally) locomotor activity, as well as spontaneous locomotor activity and sucrose pellet selfadministration (FR3 schedule) were studied in male Wistar rats after aripiprazole (0, 0.3, 1, 3 mg/kg i.p.) administration. Aripiprazole pre-treatment resulted in bidirectional effects on amphetamine self-administration. The 1 mg/kg dose increased, and the highest dose decreased the number of amphetamine infusions. In the locomotor activity experiments, aripiprazole attenuated amphetamine-induced activity dose-dependently and tended to suppress spontaneous activity. The highest aripiprazole doses decreased also sucrose pellet self-administration. The increase in amphetamine self-administration with the intermediate aripiprazole dose, as well as the decrease in amphetamine-induced locomotor activity, suggests that aripiprazole acted as a dopamine antagonist. Suppression of amphetamine and sucrose self-administration by the highest aripiprazole dose was probably caused by non-specific effects. Together, these results indicate that under conditions of dopaminergic stimulation, aripiprazole attenuates the reinforcing and psychomotor stimulant effects of d-amphetamine, but the dose range for this effect is rather limited.

Anti-cocaine vaccine development

Cocaine abuse is an ongoing and serious problem that has led to the growth of a brutal criminal enterprise, particularly in the Americas and Europe. At present, there are no effective pharmacological agents available to treat the addiction by blocking cocaine or reversing its effects. In order to help motivated addicts conquer their addiction, vaccines against cocaine are being developed and one has progressed to clinical trials. This article will discuss the concept of antidrug vaccines in general, the successes and limitations of the various anti-cocaine vaccine approaches, the results of the clinical trials with an anti-cocaine vaccine and some new vaccine-mediated approaches to combat cocaine addiction.

Behavioral evaluation of modafinil and the abuse-related effects of cocaine in rhesus monkeys

Modafinil is a central nervous system stimulant used to promote wakefulness, and it is being evaluated clinically as an agonist medication for treating stimulant abuse. This is the first report of the effects of modafinil on the abuse-related effects of cocaine in nonhuman primates. The behavioral effects of modafinil were examined in three studies. First, the discriminative stimulus effects of modafinil (3.2-32 mg/kg) were evaluated in rhesus monkeys (Macaca mulatta) trained to discriminate either low (0.18 mg/kg, IM) or high (0.4 mg/kg, IM) doses of cocaine from saline. Modafinil dose-dependently substituted for cocaine in 6 of 7 monkeys. In the second study, the effects of chronically administered modafinil (32-56 mg/kg/day, IV) on food- and cocaine-maintained (0.001-0.1 mg/kg/inj) operant responding were examined. Modafinil was administered 3 times/hr for 23 hr/day to ensure stable drug levels. Chronic treatment with 32 mg/kg/day modafinil selectively reduced responding maintained by intermediate and peak reinforcing doses of cocaine, but responding maintained by higher doses of cocaine was unaffected. Food-maintained behavior did not change during chronic modafinil treatment. In a third study, modafinil (32 and 56 mg/kg/day, IV) was examined in a reinstatement model. Modafinil transiently increased responding during extinction. These findings indicate that modafinil shares discriminative stimulus effects with cocaine and selectively reduces responding maintained by reinforcing doses of cocaine. In addition, modafinil reinstated cocaine-seeking behavior, which may reflect its cocaine-like discriminative stimulus effects. These data support clinical findings and indicate that these preclinical models may be useful for predicting the effectiveness of agonist medications for drug abuse treatment.

Pharmacotherapy of addictive disorders

Substance use disorders are highly prevalent in the United States and cause considerable damage to our society. They are underrecognized and undertreated despite a vast body of literature demonstrating the efficacy of treatment using both psychosocial and psychopharmacological modalities. For the last decade, research and progress into the biological basis of the addictive process has led to a rapidly growing number of pharmacological agents used to interrupt the addictive process at its various stages such as the initiation of substance abuse, the transition from abuse to dependence, and the prevention of drug reinstatement or relapse. Food and Drug Administration-approved medications exist for nicotine, alcohol, and opioid use disorders, and progress is being made to develop agents for stimulant use disorders. Regarding nicotine use disorders, nicotine replacement therapies,bupropion and varenicline, have Food and Drug Administration approval, and future options exist with endocannabinoid antagonists and immune therapy. Aversive agents, opiate antagonists, and glutamate based interventions are currently approved to treat alcohol use disorders with future promise with GABAergic, serotonergic, and endocannabinoid system agents. Opiate addiction is treated by approved agonist and antagonist mu-opioid medications with the future potential for agents that can modulate the stress systems and the iboga alkaloids. Although no pharmacotherapies are currently approved for cocaine addiction, promising lines of research include agents that affect dopaminergic, GABAergic, serotonergic,and glutamatergic systems as well as the promise for immune therapies.

The neurobiology of addictive disorders

Addiction is increasingly understood as a neurobiological illness where repetitive substance abuse corrupts the normal circuitry of rewarding and adaptive behaviors causing drug-induced neuroplastic changes. The addictive process can be examined by looking at the biological basis of substance initiation to the progression of substance abuse to dependence to the enduring risk of relapse. Critical neurotransmitters and neurocircuits underlie the pathological changes at each of these stages. Enhanced dopamine transmission in the nucleus accumbens is part of the common pathway for the positively rewarding aspects of drugs of abuse and for initiation of the addictive process. F-Aminobutyric acid,opioid peptides, serotonin, acetylcholine, the endocannabinoids, and glutamate systems also play a role in the initial addictive process. Dopamine also plays a key role in conditioned responses to drugs of abuse, and addiction is now recognized as a disease of pathological learning and memory. In the path from substance abuse to addiction, the neurochemistry shifts from a dopamine-based behavioral system to a predominantly glutamate-based one marked by dysregulated glutamate transmission from the prefrontal cortex to the nucleus accumbens in relation to drug versus biologically oriented stimuli. This is a core part of the executive dysfunction now understood as one of the hallmark features of addiction that also includes impaired decision making and impulse dysregulation.Understanding the neurobiology of the addictive process allows for a theoretical psychopharmacological approach to treating addictive disorders,one that takes into account biological interventions aimed at particular stages of the illness.

Efficacy of opiate maintenance therapy and adjunctive interventions for opioid dependence with comorbid cocaine use disorders: A systematic review and meta-analysis of controlled clinical trials

AIMS

To determine the efficacy of Opiate Maintenance Therapy (OMT) and adjunctive interventions for dual heroin and cocaine dependence by means of a meta-analysis.

METHOD

We searched for and retrieved randomized controlled clinical trials. We used RevMan 5.0 with random effects modeling for statistical analysis and for comparisons of relative risk, effect sizes, and confidence intervals. Subsequent moderator variables and sensitivity analyses were performed.

RESULTS

Thirty-seven studies, which have enrolled 3,029 patients, have been included in this meta-analysis. High doses of OMT were more efficacious than lower ones in the achievement of sustained heroin abstinence (RR = 2.24 [1.54, 3.24], p < .0001) but had no effect on cocaine abstinence. At equivalent doses, methadone was more efficacious than buprenorphine on cocaine abstinence (RR = 1.63 [1.20, 2.22], p = .002) and also appeared to be superior on heroin abstinence (RR = 1.39 [1.00, 1.93], p = .05). Several pharmacological and psychological potentiation strategies have been investigated. An improvement on sustained cocaine abstinence was achieved with indirect dopaminergic agonists (RR = 1.44 [1.05, 1.98], p = .03) and with contingency management (CM) focusing on cocaine abstinence (RR = 3.11 [1.80, 5.35], p < .0001).

CONCLUSIONS

Dual opioid and cocaine dependence can be effectively treated with OMT in combination with adjunctive interventions. Higher OMT doses are preferable to lower ones and methadone to buprenorphine. OMT can be enhanced with indirect dopaminergic drugs and with CM focusing on cocaine abstinence.

Neurochemistry of drug action: insights from proton magnetic resonance spectroscopic imaging and their relevance to addiction

Proton magnetic resonance spectroscopy ((1)H MRS) is a noninvasive imaging technique that permits measurement of particular compounds or metabolites within the tissue of interest. In the brain, (1)H MRS provides a snapshot of the neurochemical environment within a defined volume of interest. A search of the literature demonstrates the widespread utility of this technique for characterizing tumors, tracking the progress of neurodegenerative disease, and for understanding the neurobiological basis of psychiatric disorders. As of relatively recently, (1)H MRS has found its way into substance abuse research, and it is beginning to become recognized as a valuable complement in the brain imaging toolbox that also contains positron emission tomography, single-photon-emission computed tomography, and functional magnetic resonance imaging. Drug abuse studies using (1)H MRS have identified several biochemical changes in the brain. The most consistent alterations across drug class were reductions in N-acetylaspartate and elevations in myo-inositol, whereas changes in choline, creatine, and amino acid transmitters also were abundant. Together, the studies discussed herein provide evidence that drugs of abuse may have a profound effect on neuronal health, energy metabolism and maintenance, inflammatory processes, cell membrane turnover, and neurotransmission, and these biochemical changes may underlie the neuropathology within brain tissue that subsequently gives rise to the cognitive and behavioral impairments associated with drug addiction.

Receptor-Based Discovery of a Plasmalemmal Monoamine Transporter Inhibitor via High Throughput Docking and Pharmacophore Modeling

Recognition of psychostimulants such as cocaine and the amphetamines by the dopamine transporter (DAT) protein is principally responsible for the euphoria and addiction associated with these drugs. Using as a template the crystal structure of a distantly related bacterial leucine transporter, 3-D DAT computer molecular models have been generated. Ligand docking to such models has revealed potential substrate and inhibitor binding pockets, subsequently confirmed by in vitro pharmacology. An inhibitor pocket defined by the DAT model to be within the "extracellular vestibule", just to the extracellular side of the external gate of the primary substrate pocket, was used for virtual screening of a structural library of compounds. High-throughput docking and application of pharmacophore constraints within this vestibular inhibitor pocket identified a compound structurally dissimilar to the classic monoamine (dopamine, norepinephrine and serotonin) transporter (MAT) inhibitors. The compound displaced binding of radiolabeled cocaine analogs at all three MATs, usually with nanomolar K(i) values and within two fold of cocaine's affinity at the norepinephrine transporter. Although a very weak dopamine uptake inhibitor itself, this compound reduced by three fold the potency of cocaine in inhibiting DAT-mediated cellular uptake of dopamine. To our knowledge, the present findings are the first to successfully employ "receptor-based" computer modeling to identify moderate-to-high affinity MAT ligands. In silico ligand screening using MAT models provides a rapid, low cost discovery process that should accelerate identification of novel ligand scaffolds and provide lead compounds in combating psychostimulant addiction and in treating other monoamine-related CNS diseases.

A molecular model for cocaine binding by the immunotherapeutic human/mouse chimeric monoclonal antibody 2E2

Immunotherapy by cocaine-binding monoclonal antibodies (mAbs) has emerged as a promising strategy for the treatment of cocaine addiction. The human (gamma1 heavy chain)/murine (lambda light chain) chimeric mAb 2E2 has excellent affinity and specificity for cocaine and recent animal studies have demonstrated 2E2's ability in vivo to reduce cocaine levels in the brain as well as alter cocaine self-administration behavior in rats. In this study, we used mAb 2E2 amino acid sequence information to create a homology model for the 3-D structure of its Fv fragment. Subsequent computational docking studies revealed the intermolecular interactions potentially responsible for mAb 2E2's cocaine binding properties. The driving force of cocaine binding was identified as a combination of hydrophobic interactions and a single hydrogen bond between a light chain tyrosine residue and a carbonyl oxygen atom of cocaine. The model also allowed for an in silico evaluation of single/double residue mutations in the heavy and light chain variable regions that might further enhance mAb 2E2's cocaine binding properties.

Drug users' adherence to a 6-month vaccination protocol: effects of motivational incentives

Vaccines represent a new and promising avenue of treatment for drug abuse but pose new medication adherence challenges due to prolonged and widely spaced administration schedules. This study examined effects of prize-based incentives on retention and medication adherence among 26 cocaine users involved in a 6-month hepatitis B vaccination series. Participants could meet with research staff weekly for 24 weeks and receive 7 injections containing either the Hepatitis B vaccine or a placebo. All participants received $10 at each weekly visit (maximum of $240). Those randomly assigned to the incentive program received additional monetary payments on an escalating schedule for attendance at weekly monitoring and vaccination visits with maximum possible earnings of $751. Group attendance diverged after study week 8 with attendance better sustained in the incentive than control group (group by time interaction, p=.035). Overall percent of weekly sessions attended was 82% for incentive versus 64% for control (p=.139). Receiving all scheduled injections were 77% of incentive versus 46% of control participants (p=.107). A significantly larger percentage (74% versus 51%; p=.016) of injections were received by incentive versus control participants on the originally scheduled day. Results suggest that monetary incentives can successfully motivate drug users to attend sessions regularly and to receive injected medications in a more reliable and timely manner than may be seen under usual care procedures. Thus, incentives may be useful for addressing adherence and allowing participants to reap the full benefits of newly developed medications.

Disulfiram for the treatment of cocaine dependence

BACKGROUND

Cocaine dependence is a disorder for which no pharmacological treatment of proven efficacy exists, advances in the neurobiology could guide future medication development.

OBJECTIVES

To evaluate the efficacy and the acceptability of disulfiram for cocaine dependence.

SEARCH STRATEGY

We searched: PubMed, EMBASE, CINAHL (up to January 2008), the Cochrane Central Register of Controlled Trials (CENTRAL-The Cochrane Library, 1, 2009), reference lists of trials, main electronic sources of ongoing trials, conference proceedings.

SELECTION CRITERIA

Randomised and controlled clinical trials comparing disulfiram alone or associated with psychosocial intervention with no intervention, placebo, or other pharmacological intervention for the treatment of cocaine dependence.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

Seven studies, 492 participants, met the inclusion criteriaDisulfiram versus placebo: no statistically significant results for dropouts but a trend favouring disulfiram, two studies, 87 participants, RR 0.82 (95% CI 0.66 to 1.03). One more study, 107 participants, favouring disulfiram, was excluded from meta-analysis due high heterogeneity, RR 0.34 (95% CI 0.20 to 0.58). For cocaine use, it was not possible to pool together primary studies, results from single studies showed that, one, out of four comparisons, was in favour of disulfiram (number of weeks abstinence, 20 participants, WMD 4.50 (95% CI 2.93 to 6.07).Disulfiram versus naltrexone: no statistically significant results for dropouts but a trend favouring disulfiram, three studies, 131 participants, RR 0.67 (95% CI 0.45 to 1.01). No significant difference for cocaine use was seen in the only study that considered this outcome.Disulfiram versus no pharmacological treatment: for cocaine use: a statistically significant difference in favour of disulfiram, one study, two comparisons, 90 participants: maximum weeks of consecutive abstinence, WMD 2.10 (95% CI 0.69 to 3.51); number of subjects achieving 3 or more weeks of consecutive abstinence, RR 1.88 (95% CI 1.09 to 3.23).

AUTHORS' CONCLUSIONS

There is low evidence, at the present, supporting the clinical use of disulfiram for the treatment of cocaine dependence. Larger randomised investigations are needed investigating relevant outcomes and reporting data to allow comparisons of results between studies. Results from ongoing studies will be added as soon as their results will be available.

Active immunotherapy for the Treatment of Cocaine Dependence

Although cocaine is illegal in most countries of the world, addiction is common and increasing in many populations, and the effectiveness of current treatment options for those afflicted has been very limited. The availability of an anti-cocaine vaccine could offer help to those who wish to quit their addiction. A number of vaccines differing in their chemical nature have been developed, and one has advanced into clinical trials. This review will discuss the successes and limitations of the various vaccines and the results of clinical trials of the vaccine using succinyl norcocaine conjugated to cholera toxin B. This latter vaccine shows considerable promise for those individuals whose antibody response is adequate..

Hypothesis-driven medication discovery for the treatment of psychostimulant addiction

Psychostimulant abuse is a serious social and health problem, for which no effective treatments currently exist. A number of review articles have described predominantly 'clinic'-based pharmacotherapies for the treatment of psychostimulant addiction, but none have yet been shown to be definitively effective for use in humans. In the present article, we review various 'hypothesis'- or 'mechanism'-based pharmacological agents that have been studied at the preclinical level and evaluate their potential use in the treatment of psychostimulant addiction in humans. These compounds target brain neurotransmitter or neuromodulator systems, including dopamine (DA), gamma-aminobutyric acid (GABA), endocannabinoid, glutamate, opioid and serotonin, which have been shown to be critically involved in drug reward and addiction. For drugs in each category, we first briefly review the role of each neurotransmitter system in psychostimulant actions, and then discuss the mechanistic rationale for each drug's potential anti-addiction efficacy, major findings with each drug in animal models of psychostimulant addiction, abuse liability and potential problems, and future research directions. We conclude that hypothesis-based medication development strategies could significantly promote medication discovery for the effective treatment of psychostimulant addiction.

Tic hydantoin sigma-1 agonist: pharmacological characterization on cocaine-induced stimulant and appetitive effects

Activation of the newly identified sigma(1) chaperone protein is involved in several aspects of the psychostimulant and addictive effects of cocaine. The development of ligands that selectively target the sigma(1) protein may lead to putative potent anti-cocaine agents. Here, we synthetized substituted hydantoins with high affinity for the sigma(1) protein and evaluated their behavioral efficacy. Two pure enantiomers were designed and synthesized: tetrahydroisoquinoleine-hydantoin fused compounds 3 and 4. They increased cocaine-induced locomotor stimulation or sensitization. The most active enantiomer 4, facilitated CPP acquisition but failed to substitute for cocaine. When CPP was acquired with cocaine and then extinguished, 4 provoked reactivation of CPP. These observations showed that compound 4 shows a typical profile of sigma(1) protein activator, facilitating cocaine-induced behavioral effects. Preliminary ADME properties are in favour of an optimal therapeutic development. Such Tic-hydantoin compound may serve as a new effective agonist therapy in cocaine addiction.

Valproate treatment and cocaine cue reactivity in cocaine dependent individuals

Based on prior clinical trials indicating that gamma-aminobutyric acid (GABA)-based anticonvulsant medications reduce drug craving in cocaine dependent study participants, we tested the effects of valproate treatment on cue-induced cocaine craving. Crack cocaine dependent individuals (N=20) were tested in a randomized, placebo-controlled, within-subjects, crossover study design. Valproate treatment was titrated up to 1500 mg/day by Day 6 of treatment, cue testing was completed on Day 8 of treatment, and all study participants underwent a washout period of 5 days between active and placebo medication treatment periods. Testing included both cocaine and neutral cue exposure sessions, presented in a random and counterbalanced order. Main effects of cue exposure were found for subjective ratings of "desire to use cocaine now", the cocaine craving index, cocaine-like high, and cocaine withdrawal. Treatment interaction effects were found with "desire to use cocaine now", which underwent a greater increase following cocaine cue exposure in the valproate condition. Main effects of medication treatment were found, in which lower blood pressure and heart rate, and higher plasma cortisol levels, were associated with valproate treatment. Valproate treatment was also associated, at a trend level, with higher pre-test cocaine craving levels. The results demonstrate that cocaine cue reactivity is a robust phenomena across two assessment sessions, but fail to support the use of valproate as a means of reducing spontaneous and cue-induced cocaine craving. The use of valproate as a treatment for cocaine dependence is not supported.

Anti-drug vaccines to treat substance abuse

Substance abuse is a growing world-wide problem. The big four drugs of abuse that might lend themselves to immunotherapy are nicotine, cocaine, morphine/heroin and methamphetamine. Tobacco abuse has a well-known enormous impact on major chronic cardiovascular and pulmonary diseases, while the last three, aside from their neuropsychological effects, are illegal, leading to crime and incarceration as well as the transmission of viral diseases. Having an efficient vaccine that would generate antibodies to sequester the drug and prevent its access to the brain could go a long way toward helping a motivated addict quit the addiction. This review will discuss what has been done to bring such vaccines to human use, and what the challenges are for the future of this promising intervention.

Natural products as tools for neuroscience: discovery and development of novel agents to treat drug abuse

Much of what we know about the neurosciences is the direct result of studying psychoactive natural products. Unfortunately, there are many gaps in our understanding of the basic biological processes that contribute to the etiology of many CNS disorders. The investigation of psychoactive natural products offers an excellent approach to identify novel agents to treat CNS disorders and to find new chemical tools to better elucidate their biological mechanisms. This review will detail recent progress in a program directed toward investigating psychoactive natural products with the goal of treating drug abuse by targeting kappa opioid receptors.

Serotonergic mechanisms in addiction-related memories

Drug-associated memories are a hallmark of addiction and a contributing factor in the continued use and relapse to drugs of abuse. Repeated association of drugs of abuse with conditioned stimuli leads to long-lasting behavioral responses that reflect reward-controlled learning and participate in the establishment of addiction. A greater understanding of the mechanisms underlying the formation and retrieval of drug-associated memories may shed light on potential therapeutic approaches to effectively intervene with drug use-associated memory. There is evidence to support the involvement of serotonin (5-HT) neurotransmission in learning and memory formation through the families of the 5-HT(1) receptor (5-HT(1)R) and 5-HT(2)R which have also been shown to play a modulatory role in the behavioral effects induced by many psychostimulants. While there is a paucity of studies examining the effects of selective 5-HT(1A)R ligands, the available dataset suggests that 5-HT(1B)R agonists may inhibit retrieval of cocaine-associated memories. The 5-HT(2A)R and 5-HT(2C)R appear to be integral in the strong conditioned associations made between cocaine and environmental cues with 5-HT(2A)R antagonists and 5-HT(2C)R agonists possessing potency in blocking retrieval of cocaine-associated memories following cocaine self-administration procedures. The complex anatomical connectivity between 5-HT neurons and other neuronal phenotypes in limbic-corticostriatal brain structures, the heterogeneity of 5-HT receptors (5-HT(X)R) and the conflicting results of behavioral experiments which employ non-specific 5-HT(X)R ligands contribute to the complexity of interpreting the involvement of 5-HT systems in addictive-related memory processes. This review briefly traces the history of 5-HT involvement in retrieval of drug-cue associations and future targets of serotonergic manipulation that may reduce the impact that drug cues have on addictive behavior and relapse.