Association of cocaine withdrawal symptoms with more severe dependence and enhanced subjective response to cocaine

Cocaine Use Disorder (CUD): Current Clinical Perspectives

Cocaine use disorder (CUD) is a devastating disorder, impacting both individuals and society. Individuals with CUD face many barriers in accessing treatment for CUD, and most individuals with CUD never receive treatment. In this review, we provide an overview of CUD, including risk factors for CUD, common co-occurring disorders, acute and chronic effects of cocaine use, and currently available pharmacological and behavioral treatments. There are no FDA-approved pharmacological treatments for CUD. Future studies with larger sample sizes and testing treatment combinations are warranted. However, individuals with CUD and co-occurring disorders (eg, a mood or anxiety disorder) may benefit from medication treatments. There are behavioral interventions that have demonstrated efficacy in treating CUD – contingency management (CM) and cognitive-behavioral therapy for substance use disorders (CBT-SUD) in particular – however many barriers remain in delivering these treatments to patients. Following the discussion of current treatments, we highlight some promising emerging treatments, as well as offer a framework that can be used in building a treatment plan for individuals with CUD.

Sleep loss and addiction

Reducing sleep hours is a risk factor for developing cardiovascular, metabolic, and psychiatric disorders. Furthermore, previous studies have shown that reduction in sleep time is a factor that favors relapse in addicted patients. Additionally, animal models have demonstrated that both sleep restriction and sleep deprivation increase the preference for alcohol, methylphenidate, and the self-administration of cocaine. Therefore, the present review discusses current knowledge about the influence of sleep hours reduction on addictivebehaviors; likewise, we discuss the neuronal basis underlying the sleep reduction-addiction relationship, like the role of the orexin and dopaminergic system and neuronal plasticity (i.e., delta FosB expression). Potentially, chronic sleep restriction could increase brain vulnerability and promote addictive behavior.

Arousal-Mediated Sleep Disturbance Persists During Cocaine Abstinence in Male Mice

Acute cocaine disturbs sleep on a dose-dependent basis; however, the consequences of chronic cocaine remain unclear. While the arousal promotion following cocaine has been well-established, effects of cocaine on sleep after termination of chronic cocaine exposure appear variable in human subjects with few studies in non-human subjects. Here, a within-subjects design (outcomes normalized to baseline, undisturbed behavior) and between-subjects design (repeated experimenter-administered cocaine vs. experimenter-administered saline) was used to investigate sleep homeostasis and sleep/waking under repeated cocaine/saline exposure and prolonged forced abstinence conditions in mice. Overall, during the forced abstinence period increases in arousal, as determined by sleep latency and gamma energy, persisted for 2 weeks. However, the sleep response to externally enforced sleep deprivation was unchanged suggesting that sleep disruptions during the forced abstinence period were driven by enhancement of arousal in the absence of changes in sleep homeostatic responses.

Childhood trauma and the severity of past suicide attempts in outpatients with cocaine use disorders

INTRODUCTION

Suicide attempts have been associated with both cocaine use disorder (CocUD) and childhood trauma. We investigated how childhood trauma is an independent risk factor for serious and recurrent suicide attempts in CocUD. Method: 298 outpatients (23% women) with CocUD underwent standardized assessments of substance dependence (Diagnostic and Statistical Manual-mental disorders, fourth edition, text revised), impulsiveness, resilience, and childhood trauma, using validated tools. Suicide attempts history was categorized as single vs. recurrent or non-serious vs. serious depending on the lifetime number of suicide attempts and the potential or actual lethality of the worst attempt reported, respectively. Bivariate and multinomial regression analyses were used to characterize which childhood trauma patterns were associated with the suicide attempts groups. Results: 58% of CocUD patients reported childhood trauma. Recurrent and serious suicide attempts clustered together and were thus combined into "severe SA." Severe suicide attempt risk increased proportionally to the number of childhood traumas (test for trend, p = 9 × 10^-7). Non-severe suicide attempt risk increased with impulsiveness and decreased with resilience. In multinomial regression models, a higher number of traumas and emotional abuse were independently and only associated with severe vs. non-severe suicide attempts (effect size = 0.82, AUC = 0.7). The study was limited by its cross-sectional design. Conclusion: These preferential associations between childhood trauma and severe suicide attempts warrant specific monitoring of suicide attempts risk in CocUD, regardless of the severity of addiction profiles.

Interaction between cocaine use and sleep behavior: A comprehensive review of cocaine's disrupting influence on sleep behavior and sleep disruptions influence on reward seeking

Dopamine, orexin (hypocretin), and adenosine systems have dual roles in reward and sleep/arousal suggesting possible mechanisms whereby drugs of abuse may influence both reward and sleep/arousal. While considerable variability exists across studies, drugs of abuse such as cocaine induce an acute sleep loss followed by an immediate recovery pattern that is consistent with a normal response to loss of sleep. Under more chronic cocaine exposure conditions, an abnormal recovery pattern is expressed that includes a retention of sleep disturbance under withdrawal and into abstinence conditions. Conversely, experimentally induced sleep disturbance can increase cocaine seeking. Thus, complementary, sleep-related therapeutic approaches may deserve further consideration along with development of non-human models to better characterize sleep disturbance-reward seeking interactions across drug experience.

Cannabidiol Modulates Behavioural and Gene Expression Alterations Induced by Spontaneous Cocaine Withdrawal

The aim of this study was to evaluate the effects of cannabidiol (CBD) on the behavioural and gene expression changes in a new animal model of spontaneous cocaine withdrawal. For this purpose, male CD-1 mice were exposed to progressive increasing doses of cocaine for 12 days (15 to 60 mg/kg/day, i.p.), evaluating spontaneous cocaine withdrawal 6 h after the last cocaine administration. The effects of CBD (10, 20, and 40 mg/kg, i.p.) were evaluated on cocaine withdrawal-induced alterations in motor activity, somatic signs, and anxiety-like behaviour. Furthermore, gene expression changes in dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the ventral tegmental area, and in cannabinoid receptors 1 (CNR1) and 2 (CNR2) in the nucleus accumbens, were analysed by real-time PCR. The results obtained in the study showed that mice exposed to the spontaneous cocaine withdrawal model presented increased motor activity, somatic withdrawal signs, and high anxiety-like behaviour. Interestingly, the administration of CBD normalized motor and somatic signs disturbances and induced an anxiolytic effect. Moreover, the administration of CBD blocked the increase of DAT and TH gene expression in mice exposed to the cocaine withdrawal, regulated the decrease of CNR1 and induced an additional upregulation of CNR2 gene expression. Thus, this model of spontaneous cocaine withdrawal induces clear behavioural and gene expression changes in mice. Interestingly, CBD alleviates these behavioural and gene expression alterations suggesting its potential for the management of cocaine withdrawal.

Mirtazapine attenuates anxiety- and depression-like behaviors in rats during cocaine withdrawal

BACKGROUND

Anxiety and depression, key symptoms of the cocaine withdrawal syndrome in human addicts, are considered the main factors that precipitate relapse in chronic cocaine addiction. Preclinical studies have found that rodents exposed to different withdrawal periods show an increase in anxiety and depressive-like behavior. Mirtazapine - a tetracyclic medication - is used primarily to treat depression and, sometimes, anxiety. It has also successfully improved withdrawal symptoms in drug-dependent patients.

AIM

This study sought to determine whether chronic dosing of mirtazapine during cocaine withdrawal reduced depression- and anxiety-like behaviors that characterize cocaine withdrawal in animals.

METHODS

Cocaine pre-treated Wistar rats were subjected to a 60-day cocaine withdrawal period during which depression- and anxiety-like behaviors were evaluated in open field tests (OFT), the elevated plus-maze (EPM), the light-dark box test (LDT), the forced swimming test (FST) and spontaneous locomotor activity (SLA).

RESULTS

We found that chronic dosing with different doses of mirtazapine (30 and 60 mg/kg) decreased depression- and anxiety-like behaviors induced by different doses of cocaine (10, 20 and 40 mg/kg) during the 60-day cocaine withdrawal.

INTERPRETATION

Our results suggest that the pharmacological effect of mirtazapine on its target sites of action (α₂-adrenergic and 5-HT_2A and 5-HT₃ receptors) within the brain may improve depression- and anxiety-like behaviors for long periods.

CONCLUSION

Therefore, the findings support the use of mirtazapine as a potentially effective therapy to reduce anxiety and depressive-like behavior during cocaine withdrawal.

Conditioned aversive responses produced by delayed, but not immediate, exposure to cocaine and morphine in male Sprague-Dawley rats

RATIONALE

To determine the conditions under which tastes paired with delayed access to experimenter-delivered cocaine and morphine elicit a conditionally aversive affective state.

OBJECTIVES AND METHODS

The potential of saccharin paired with immediate access to cocaine (5, 10, 20 mg/kg, sc and ip) and delayed (30 and 10 min) access to cocaine (20 mg/kg, sc and ip) and morphine (10 mg/kg, sc) to elicit a pattern of aversive responding in the taste reactivity test (Grill and Norgren 1978a) was evaluated. Cocaine-induced aversions were compared with those produced by a moderate dose of LiCl (50 mg/kg). Finally, as an independent measure of cocaine withdrawal, the potential of exposure to saccharin paired with delayed access to cocaine to produce anxiogenic-like responding in the Light-Dark Emersion test was evaluated.

RESULTS

Immediate access to cocaine did not produce conditioned aversion at any dose. Delayed (30 or 10 min) access to sc cocaine (20 mg/kg) produced robust conditioned aversion and delayed access to ip cocaine (20 mg/kg; 30 min) and to sc morphine (10 mg/kg; 10 min) produced weaker conditioned aversion. Yawning emerged as a potential withdrawal response in rats conditioned with delayed (30 min) access to 20 mg/kg, sc, cocaine. Contextual cues did not produce conditioned aversion when paired with delayed access to sc cocaine (20 mg/kg). Finally, exposure to saccharin paired with delayed access to cocaine produced anxiogenic-like responding in the Light-Dark Emersion test.

CONCLUSION

Our results support the contention that a conditioned aversive state develops when a taste cue comes to predict the delayed availability of drugs of abuse.

Mirtazapine attenuates cocaine seeking in rats

BACKGROUND

Relapse to cocaine use is a major problem in the clinical treatment of cocaine addiction. Antidepressants have been studied for their therapeutic potential to treat cocaine use disorder. Research has suggested that antidepressants attenuate both drug craving and the re-acquisition of drug-seeking and drug-taking behaviors. This study examined the efficacy of mirtazapine, an antidepressant/anxiolytic, in decreasing cocaine seeking in rats.

METHODS

We used the cocaine self-administration paradigm to assess the effects of mirtazapine on rats trained to self-administer cocaine or food under a fixed-ratio schedule. Mirtazapine (30 mg/kg, i.p.) was administered during extinction.

RESULTS

Mirtazapine significantly attenuated non-reinforced lever-press responses during extinction. Moreover, the mirtazapine dosed for 30 days during extinction produced sustained attenuation of lever-press responses during re-acquisition of cocaine self-administration, without changing food-seeking behavior. Our results showed that mirtazapine attenuated the re-acquisition of cocaine-seeking responses.

CONCLUSION

Our study pointed to the efficacy of mirtazapine in reducing the risk of drug relapse during abstinence, suggesting for its potential use as a novel pharmacological agent to treat drug abuse.

Topiramate for the management of methamphetamine dependence: a pilot randomized, double-blind, placebo-controlled trial

To date, no medication has been approved as an effective treatment for methamphetamine dependence. Topiramate has attracted considerable attention as a treatment for the dependence on alcohol and stimulants. Therefore, this study aimed to evaluate the effect of topiramate for methamphetamine dependence. This study was a double-blind, randomized, placebo-controlled trial. In the present investigation, 62 methamphetamine-dependent adults were enrolled and randomized into two groups, and received topiramate or a placebo for 10 weeks in escalating doses from 50 mg/day to the target maintenance dose of 200 mg/day. Addiction severity index (ASI) and craving scores were registered every week. The Beck questionnaire was also given to each participant at baseline and every 2 weeks during the treatment. Urine samples were collected at baseline and every 2 weeks during the treatment. Fifty-seven patients completed 10 weeks of the trial. There was no significant difference between both groups in the mean percentage of prescribed capsules taken by the participants. At week six, the topiramate group showed a significantly lower proportion of methamphetamine-positive urine tests in comparison with the placebo group (P = 0.01). In addition, there were significantly lower scores in the topiramate group in comparison with the placebo group in two domains of ASI: drug use severity (P < 0.001) and drug need (P < 0.001). Furthermore, the craving score (duration) significantly declined in the topiramate patients compared to those receiving the placebo. In conclusion, the results of this trial suggest that topiramate may be beneficial for the treatment of methamphetamine dependence.

A critical review of the literature on attentional bias in cocaine use disorder and suggestions for future research

Cocaine use disorder (CUD) continues to be an important public health problem, and novel approaches are needed to improve the effectiveness of treatments for CUD. Recently, there has been increased interest in the role of automatic cognition such as attentional bias (AB) in addictive behaviors, and AB has been proposed to be a cognitive marker for addictions. Automatic cognition may be particularly relevant to CUD, as there is evidence for particularly robust AB to cocaine cues and strong relationships to craving for cocaine and other illicit drugs. Further, the wide-ranging cognitive deficits (e.g., in response inhibition and working memory) evinced by many cocaine users enhance the potential importance of interventions targeting automatic cognition in this population. In the current article, we discuss relevant addiction theories, followed by a review of studies that examined AB in CUD. We then consider the neural substrates of AB, including human neuroimaging, neurobiological, and pharmacological studies. We conclude with a discussion of research gaps and future directions for AB in CUD.

Psychometric properties of the Spanish version of the Cocaine Selective Severity Assessment to evaluate cocaine withdrawal in treatment-seeking individuals

Reliable and valid assessment of cocaine withdrawal is relevant for treating cocaine-dependent patients. This study examined the psychometric properties of the Spanish version of the Cocaine Selective Severity Assessment (CSSA), an instrument that measures cocaine withdrawal. Participants were 170 cocaine-dependent inpatients receiving detoxification treatment. Principal component analysis revealed a 4-factor structure for CSSA that included the following components: 'Cocaine Craving and Psychological Distress', 'Lethargy', 'Carbohydrate Craving and Irritability', and 'Somatic Depressive Symptoms'. These 4 components accounted for 56.0% of total variance. Internal reliability for these components ranged from unacceptable to good (Chronbach's alpha: 0.87, 0.65, 0.55, and 0.22, respectively). All components except Somatic Depressive Symptoms presented concurrent validity with cocaine use. In summary, while some properties of the Spanish version of the CSSA are satisfactory, such as interpretability of factor structure and test-retest reliability, other properties, such as internal reliability and concurrent validity of some factors, are inadequate.

Pharmacological treatment of comorbid PTSD and substance use disorder: recent progress

Previous research has identified a strong association between posttraumatic stress disorder (PTSD) and substance use disorder (SUD), necessitating the development of treatments that address both conditions. Some pharmacotherapies are effective for the treatment of PTSD and SUD alone, however; no medications have been proven to be effective for the combination of these conditions. We review the recent advances in pharmacological treatment of comorbid PTSD and SUD. A randomized clinical trial of sertraline, a serotonin reuptake inhibitor (SSRI), did not show overall efficacy for comorbid PTSD and alcohol dependence (AD), although it may have efficacy among light drinkers. Another clinical trial demonstrated the efficacy of both disulfiram and naltrexone for the treatment of AD in individuals with PTSD. A more recent clinical trial suggested that norepinephrine uptake inhibitors may also have efficacy for the treatment of comorbid PTSD and AD. In animal and preliminary human studies, brain norepinephrine and glutamate/GABA have emerged as potential treatment targets for comorbid PTSD and SUD. Noradrenergic medications that are promising for comorbid PTSD and SUD include prazosin, guanfacine, and atomoxetine. Promising glutamate/GABA medications include topiramate, memantine, acamprosate, N-acetylcysteine (NAC), and ketamine. The safety and efficacy of these medications for the treatment of PTSD and SUD need to be tested in controlled clinical trials.

Abstinence-related changes in sleep during treatment for cocaine dependence

BACKGROUND

Former sleep studies among non-treatment seeking chronic cocaine users had captured polysomnographic changes for as long as three weeks of abstinence.

METHODS

20 cocaine dependent participants, randomized to placebo in an ongoing clinical trial, received 12 days of inpatient substance abuse treatment followed by 6 weeks of outpatient cognitive behavioral therapy. Polysomnographic recording was performed on consecutive nights during the 1st and 2nd inpatient and 3rd and 6th outpatient weeks. Number of days abstinent was determined from thrice weekly urine toxicology and self-report. Polysomnographic sleep was compared between study week 1 and 2, using paired t-tests. Trajectory of total sleep time (TST) was modeled both as a linear and a quadratic function of days abstinent.

RESULTS

Despite reporting an improvement in overall sleep quality, polysomnographic sleep worsened from week 1 to 2. Among all participants, TST and stage 2 sleep time decreased, while REM sleep latency increased. Among participants who began the study with a positive urine test, there was also a decrease in REM and a trend for decreased slow wave sleep. TST compared to number of days abstinent (up to 54 days) was best fit with a quadratic model (p=0.002), suggesting the possibility of an improvement in total sleep time with extended abstinence.

CONCLUSIONS

This is the first polysomnographic characterization of sleep in a large sample of cocaine users in treatment. Present findings confirm earlier results of poor and deteriorating sleep early in abstinence, and raise the possibility of improvement after an extended abstinence.

A double-blind, placebo-controlled trial of topiramate for the treatment of comorbid cocaine and alcohol dependence

BACKGROUND

Topiramate increases GABAergic activity and antagonizes the AMPA/kainate subtype of glutamate receptors. Through these mechanisms of action, topiramate may reduce alcohol and cocaine reward and may reduce alcohol and cocaine craving. Topiramate has been shown to reduce drinking in persons with alcohol dependence, and reduce relapse in stimulant-dependent patients. The current trial was intended to test the ability of topiramate to promote cocaine and alcohol abstinence among patients addicted to both drugs.

METHODS

The study was a double-blind, placebo-controlled, 13-week trial involving 170 cocaine and alcohol dependent subjects. After achieving a period of cocaine and alcohol abstinence, subjects were randomized to topiramate, 300 mg daily, or identical placebo capsules. In addition, subjects received weekly individual psychotherapy. Primary outcome measures included self-reported alcohol and cocaine use, and thrice weekly urine drug screens. Secondary outcome measures included cocaine and alcohol craving, Addiction Severity Index results, cocaine withdrawal symptoms, and clinical global improvement ratings.

RESULTS

Topiramate was not better than placebo in reducing cocaine use on the a priori primary outcome measure, or in reducing alcohol use. Topiramate was not better than placebo in reducing cocaine craving. Topiramate-treated subjects, compared to placebo-treated subjects, were more likely to be retained in treatment and more likely to be abstinent from cocaine during the last three weeks of the trial. Subjects who entered treatment with more severe cocaine withdrawal symptoms responded better to topiramate.

DISCUSSION

Topiramate plus cognitive behavioral therapy may reduce cocaine use for some patients with comorbid cocaine and alcohol dependence.

Pharmacologically-mediated reactivation and reconsolidation blockade of the psychostimulant-abuse circuit: a novel treatment strategy

Psychostimulant abuse continues to present legal, socioeconomic and medical challenges as a primary psychiatric disorder, and represents a significant comorbid factor in major psychiatric and medical illnesses. To date, monotherapeutic drug treatments have not proven effective in promoting long-term abstinence in psychostimulant abusers. In contrast to clinical trials utilizing monotherapies, combinations of dopamine (DA) agonists and selective 5-HT(3), 5HT(2A/2C), or NK(1) antagonists have shown robust efficacy in reversing behavioral and neurobiological alterations in animal models of psychostimulant abuse. One important temporal requirement for these treatments is that the 5-HT or NK(1) receptor antagonist be given at a critical time window after DA agonist administration. This requirement may reflect a necessary dosing regimen towards normalizing underlying dysfunctional neural circuits and "addiction memory" states. Indeed, chronic psychostimulant abuse can be conceptualized as a consolidated form of dysfunctional memory maintained by repeated drug- or cue-induced reactivation of neural circuit and subsequent reconsolidation. According to this concept, the DA agonist given first may reactivate this memory circuit, thereby rendering it transiently labile. The subsequent antagonist is hypothesized to disrupt reconsolidation necessary for restabilization, thus leading progressively to a therapeutically-mediated abolishment of dysfunctional synaptic plasticity. We propose that long-term abstinence in psychostimulant abusers may be achieved not only by targeting putative mechanistic pathways, but also by optimizing drug treatment regimens designed to disrupt the neural processes underlying the addicted state.

Reversal of long-term methamphetamine sensitization by combination of pergolide with ondansetron or ketanserin, but not mirtazapine

Psychostimulant abuse represents a psychiatric disorder and societal concern that has been largely unamenable to therapeutic interventions. We have previously demonstrated that the 5-HT₃ antagonist ondansetron or non-selective 5-HT(₂A/₂C) antagonist ketanserin administered 3.5 h following daily pergolide, a non-selective DA agonist, reverses previously established cocaine sensitization. The present study was conducted to evaluate whether the same treatments or delayed pairing of pergolide with the antidepressant mirtazapine can also reverse consolidated methamphetamine (METH) behavioral sensitization. Sprague-Dawley rats received METH infusion via osmotic minipumps (25 mg/kg/day, s.c.) for 7 days, with accompanying daily injections of escalating METH doses (0-6 mg/kg, s.c.). This regimen takes into account the faster elimination of METH in rats, and is designed to replicate plasma METH concentrations with superimposed peak drug levels as observed during METH binging episodes in humans. Following a 7-day METH withdrawal, ondansetron (0.2 mg/kg, s.c.), ketanserin (1.0 mg/kg, s.c.), or mirtazapine (10mg/kg, i.p.) was administered 3.5 h after pergolide injections (0.1 mg/kg, s.c., qd) for 7 days. Behavioral sensitization as a model of METH abuse was assessed 14 days after the combination treatment cessation (i.e., day 28 of METH withdrawal) through an acute challenge with METH (0.5 mg/kg, i.p.). Pergolide combined with ondansetron or ketanserin reversed METH behavioral sensitization, but pergolide-mirtazapine combination was ineffective. The role of reactivation of addiction "circuit" by a non-selective DA agonist, and subsequent reconsolidation blockade through 5-HT₃ or 5-HT₂ antagonism in reversal of METH sensitization and treatment of METH addiction is discussed.

Treatment Outcome Predictors for Cocaine Dependence

Over the past decade, a large number of potential medications have been examined in clinical trials for cocaine dependence. Unfortunately, no effective pharmacotherapies for cocaine dependence have been found to date. Although effective treatments for cocaine dependence are still being investigated, a few variables have been found to significantly predict cocaine treatment response. These variables include cocaine use variables, such as days of cocaine use in the month before treatment, baseline urine cocaine results, and cocaine withdrawal symptoms. Comorbid depression and alcohol use have also been shown to be risk factors for relapse. Among personality variables, impulsivity and similar personality traits may predict treatment response. Initial promising findings with genetic polymorphism, brain activation, and stress response have also been found and need to be replicated in future studies.

Cocaine Withdrawal Symptoms Predict Medication Response in Cocaine Users

The purpose of this study was to examine the influence of cocaine withdrawal symptoms on addiction severity and treatment outcomes in methadone stabilized cocaine users who participated in pharmacotherapy trials using gamma-aminobutyric acid (GABA) medications. Subjects who fulfilled DSM-IV cocaine withdrawal criteria (n = 45), compared to those who did not (n = 40), showed a greater increase in cocaine free urines in response to pharmacotherapy with GABA medications. Altogether, our results and previous studies support the clinical utility of cocaine withdrawal symptoms in predicting treatment response to medications, such that low withdrawal severity may predict better treatment response to GABA medications, while high withdrawal severity may predict better response to adrenergic blockers. This hypothesis needs to be tested in prospective clinical trials.

Heterogeneity of stimulant dependence: a national drug abuse treatment clinical trials network study

We investigated the presence of DSM-IV subtyping for dependence on cocaine and amphetamines (with versus without physical dependence) among outpatient stimulant users enrolled in a multisite study of the Clinical Trials Network (CTN). Three mutually exclusive groups were identified: primary cocaine users (n = 287), primary amphetamine users (n = 99), and dual users (cocaine and amphetamines; n = 29). Distinct subtypes were examined with latent class and logistic regression procedures. Cocaine users were distinct from amphetamine users in age and race/ethnicity. There were four distinct classes of primary cocaine users: non-dependence (15%), compulsive use (14%), tolerance and compulsive use (15%), and physiological dependence (tolerance, withdrawal, and compulsive use; 56%). Three distinct classes of primary amphetamine users were identified: non-dependence (11%), intermediate physiological dependence (31%), and physiological dependence (58%). Regardless of stimulants used, most female users were in the most severe or the physiological dependence group. These results lend support for subtyping dependence in the emerging DSM-V.

Vaccines for cocaine abuse

Treatments for cocaine abuse have been disappointingly ineffective, especially in comparison with those for some other abused substances. A new approach, using vaccination to elicit specific antibodies to block the access of cocaine to the brain, has shown considerable promise in animal models, and more recently in human trials. The mechanism of action for the antibody effect on cocaine is very likely to be the straightforward and intuitive result of the binding of the drug in circulation by antibodies, thereby reducing its entry into the central nervous system and thus its pharmacological effects. The effectiveness of such antibodies on drug pharmacodynamics is a function of both the quantitative and the qualitative properties of the antibodies, and this combination will determine the success of the clinical applications of anti-cocaine vaccines in helping addicts discontinue cocaine abuse. This review will discuss these issues and present the current developmental status of cocaine conjugate vaccines.

Norepinephrine and stimulant addiction

No pharmacotherapies are approved for stimulant use disorders, which are an important public health problem. Stimulants increase synaptic levels of the monoamines dopamine (DA), serotonin and norepinephrine (NE). Stimulant reward is attributable mostly to increased DA in the reward circuitry, although DA stimulation alone cannot explain the rewarding effects of stimulants. The noradrenergic system, which uses NE as the main chemical messenger, serves multiple brain functions including arousal, attention, mood, learning, memory and stress response. In pre-clinical models of addiction, NE is critically involved in mediating stimulant effects including sensitization, drug discrimination and reinstatement of drug seeking. In clinical studies, adrenergic blockers have shown promise as treatments for cocaine abuse and dependence, especially in patients experiencing severe withdrawal symptoms. Disulfiram, which blocks NE synthesis, increased the number of cocaine-negative urines in five randomized clinical trials. Lofexidine, an alpha(2)-adrenergic agonist, reduces the craving induced by stress and drug cues in drug users. In addition, the NE transporter (NET) inhibitor atomoxetine attenuates some of d-amphetamine's subjective and physiological effects in humans. These findings warrant further studies evaluating noradrenergic medications as treatments for stimulant addiction.

The neuropsychology of cocaine addiction: recent cocaine use masks impairment

Individuals with current cocaine use disorders (CUD) form a heterogeneous group, making sensitive neuropsychological (NP) comparisons with healthy individuals difficult. The current study examined the effects on NP functioning of four factors that commonly vary among CUD: urine status for cocaine (positive vs negative on study day), cigarette smoking, alcohol consumption, and dysphoria. Sixty-four cocaine abusers were matched to healthy comparison subjects on gender and race; the groups also did not differ in measures of general intellectual functioning. All subjects were administered an extensive NP battery measuring attention, executive function, memory, facial and emotion recognition, and motor function. Compared with healthy control subjects, CUD exhibited performance deficits on tasks of attention, executive function, and verbal memory (within one standard deviation of controls). Although CUD with positive urine status, who had higher frequency and more recent cocaine use, reported greater symptoms of dysphoria, these cognitive deficits were most pronounced in the CUD with negative urine status. Cigarette smoking, frequency of alcohol consumption, and dysphoria did not alter these results. The current findings replicate a previously reported statistically significant, but relatively mild NP impairment in CUD as compared with matched healthy control individuals and further suggest that frequent/recent cocaine use [corrected] may mask underlying cognitive (but not mood) disturbances. These results call for development of pharmacological agents targeted to enhance cognition, without negatively impacting mood in individuals addicted to cocaine.

Association of psychiatric and substance use disorder comorbidity with cocaine dependence severity and treatment utilization in cocaine-dependent individuals

The relations among psychiatric and substance dependence disorders and treatment utilization are of interest both for their clinical management and for health services. We examined these relations using six self-reported indices of cocaine dependence severity and three self-reported measures of treatment utilization and self-help group participation for cocaine dependence. The sample consisted of dyads: namely, a cocaine-dependent adult proband (N=449) and a cocaine-dependent sibling (N=449). Psychiatric and substance use disorders were assessed with the Semi-structured Assessment for Drug Dependence and Alcoholism. We controlled for the nesting within families of proband-sibling dyads and for demographic features using generalized estimating equation linear and logistic regression analyses. We found that psychiatric disorders were associated with an increased likelihood of cocaine dependence treatment or self-help group participation, but with only one of six indices of cocaine dependence severity. Bipolar disorder and antisocial personality disorder were associated with greater past heavy cocaine use, and with utilizing self-help but not treatment. Major depressive disorder and posttraumatic stress disorder were associated with treatment utilization and overall services utilization, respectively. The presence of other substance use disorders (SUDs) was the strongest correlate of cocaine dependence severity. Results suggest that co-occurring substance dependence and psychiatric disorders warrant attention in cocaine dependence assessment, treatment, and self-help.

The search for medications to treat stimulant dependence

Progress in understanding the neurobiology of stimulant dependence has enabled researchers to identify medications whose pharmacological effects suggest that they might help patients initiate abstinence or avoid relapse. Several of these medications and a vaccine have shown encouraging results in controlled clinical trials with cocaine-dependent patients. The search for a medical treatment for methamphetamine dependence started more recently, due to the later emergence of this epidemic, but at least one candidate medication has shown promise in early clinical testing. Treatment approaches that combine efficacious medications and empirically proven behavioral interventions, such as voucher-based reinforcement therapy, will almost certainly produce the best results.

Bupropion hydrochloride versus placebo, in combination with cognitive behavioral therapy, for the treatment of cocaine abuse/dependence

Bupropion hydrochloride is a dopamine and norepinephrine reuptake inhibitor which may be an effective treatment for cocaine dependence due to its ability to reverse deficits in dopaminergic functioning that occur in chronic cocaine users. We performed a randomized, double-blind, placebo controlled trial comparing outpatient treatment with bupropion (N = 37) and placebo (N = 33) in combination with standard cognitive behavioral therapy. There were no statistically significant differences between bupropion and placebo in treatment outcomes, including aggregate measures of urine drug screen results (Joint Probability Index at 16 weeks: 0.43 for bupropion and 0.38 for placebo), treatment retention, cocaine craving ratings, and assessments of depressive symptoms. The failure to find an effect for bupropion relative to placebo, when combined with standard cognitive behavioral therapy, dampens enthusiasm for future development of bupropion as a cocaine pharmacotherapy.

Behavioral and electrophysiological indices of negative affect predict cocaine self-administration

The motivation to seek cocaine comes in part from a dysregulation of reward processing manifested in dysphoria, or affective withdrawal. Learning is a critical aspect of drug abuse; however, it remains unclear whether drug-associated cues can elicit the emotional withdrawal symptoms that promote cocaine use. Here we report that a cocaine-associated taste cue elicited a conditioned aversive state that was behaviorally and neurophysiologically quantifiable and predicted subsequent cocaine self-administration behavior. Specifically, brief intraoral infusions of a cocaine-predictive flavored saccharin solution elicited aversive orofacial responses that predicted early-session cocaine taking in rats. The expression of aversive taste reactivity also was associated with a shift in the predominant pattern of electrophysiological activity of nucleus accumbens (NAc) neurons from inhibitory to excitatory. The dynamic nature of this conditioned switch in affect and the neural code reveals a mechanism by which cues may exert control over drug self-administration.

Conditioned and sensitized responses to stimulant drugs in humans

In animal models considerable evidence suggests that increased motivation to seek and ingest drugs of abuse are related to conditioned and sensitized activations of the mesolimbic dopamine (DA) system. Direct evidence for these phenomena in humans, though, is sparse. However, recent studies support the following. First, the acute administration of drugs of abuse across pharmacological classes increases extracellular DA levels within the human ventral striatum. Second, individual differences in the magnitude of this response correlate with rewarding effects of the drugs and the personality trait of novelty seeking. Third, transiently diminishing DA transmission in humans decreases drug craving, the propensity to preferentially respond to reward-paired stimuli, and the ability to sustain responding for future drug reward. Finally, very recent studies suggest that repeated exposure to stimulant drugs, either on the street or in the laboratory, can lead to conditioned and sensitized behavioral responses and DA release. In contrast to these findings, though, in individuals with a long history of substance abuse, drug-induced DA release is decreased. This diminished DA release could reflect two different phenomena. First, it is possible that drug withdrawal related decrements in DA cell function persist longer than previously suspected. Second, drug-paired stimuli may gain marked conditioned control over the release of DA and the expression of sensitization leading to reduced DA release when drug-related cues are absent. Based on these observations a two-factor hypothesis of the role of DA in drug abuse is proposed. In the presence of drug cues, conditioned and sensitized DA release would occur leading to focused drug-seeking behavior. In comparison, in the absence of drug-related stimuli DA function would be reduced, diminishing the ability of individuals to sustain goal-directed behavior and long-term objectives. This conditioned control of the expression of sensitized DA release could aggravate susceptibility to relapse, narrow the range of interests and perturb decision-making, accounting for a wide range of addiction related phenomena.

A qualitative and quantitative review of cocaine-induced craving: the phenomenon of priming

Drug-induced craving is thought to play an important role in relapse occasioned by a "slip", or an isolated use of a previously abused drug after a period of abstinence. Clinical experience suggests that acute exposure to cocaine elicits craving (hereafter referred to as "priming"); however, this has received surprisingly little attention in the clinical literature.

AIMS

The intentions of this review are to provide a qualitative review of the literature as well as a more stringent quantitative review of the existence and presence of cocaine-induced priming effects.

METHODS

In order to determine whether priming effects occur following cocaine administration, we conducted qualitative and quantitative reviews of studies in which participants received cocaine under experimentally controlled conditions in the laboratory.

RESULTS

The results of the qualitative review were equivocal, while the quantitative review revealed that cocaine administration was associated with a significant increase in craving for cocaine, and the effect size of this relationship was large.

CONCLUSION

A review of the individual studies revealed marked variability, suggesting that priming effects did not occur consistently and that there may be factors that mediate or moderate the intensity of the priming effects induced by cocaine. The implications of these findings are discussed.

The effect of individual cocaine withdrawal symptoms on outcomes in cocaine users

Preclinical and clinical studies suggest that individual drug withdrawal symptoms may have differential effects on addictive behaviors. The goals of this study were (1) to explore the dimensions of DSM-IV cocaine withdrawal symptoms and (2) to examine the association of these dimension and individual withdrawal symptoms with problems related to drug dependence in male and female cocaine users. The results of the principal components analyses of withdrawal symptoms supported a two factor model. The first one is labeled the depressive symptoms factor and included symptoms of depressed mood, psychomotor agitation, psychomotor retardation, craving for cocaine, insomnia, and vivid, unpleasant dreams. The second factor labeled the somatic symptoms factor included symptoms of increased appetite, hypersomnia, and fatigue. The depressive symptoms factor, in comparison to the somatic symptoms factor, was associated with more frequent reporting of having chemical dependency treatment, having depressed mood for longer than 2 weeks, and trading cocaine for sex. When the individual withdrawal symptoms were examined, depressed mood, psychomotor agitation, vivid, unpleasant dreams, and fatigue were associated with more frequent reporting of some of these outcomes. Our findings support two dimensions in cocaine withdrawal symptoms with differential effects on cocaine dependence outcomes.

A double-blind, placebo-controlled trial of modafinil for cocaine dependence

Despite years of active research, there are still no approved medications for the treatment of cocaine dependence. Modafinil is a glutamate-enhancing agent that blunts cocaine euphoria under controlled conditions, and the current study assessed whether modafinil would improve clinical outcome in cocaine-dependent patients receiving standardized psychosocial treatment. This was a randomized, double-blind, placebo-controlled trial conducted at a university outpatient center (from 2002 to 2003) on a consecutive sample of 62 (predominantly African American) cocaine-dependent patients (aged 25-63) free of significant medical and psychiatric conditions. After screening, eligible patients were randomized to a single morning dose of modafinil (400 mg), or matching placebo tablets, for 8 weeks while receiving manual-guided, twice-weekly cognitive behavioral therapy. The primary efficacy measure was cocaine abstinence based on urine benzoylecgonine levels. Secondary measures were craving, cocaine withdrawal, retention, and adverse events. Modafinil-treated patients provided significantly more BE-negative urine samples (p=0.03) over the 8-week trial when compared to placebos, and were more likely to achieve a protracted period (> or =3 weeks) of cocaine abstinence (p=0.05). There were no serious adverse events, and none of the patients failed to complete the study as a result of adverse events. This study provides preliminary evidence, which should be confirmed by a larger study, that modafinil improves clinical outcome when combined with psychosocial treatment for cocaine dependence.

Recent advances in the pharmacotherapy of cocaine dependence

The pharmacotherapy of cocaine dependence is a rapidly developing field of research that may soon produce efficacious medications. Expanding research on reward-related brain circuitry, which is acutely activated and chronically dysregulated by cocaine, has helped reveal the neurobiological features of cocaine dependence and is guiding pharmacologic strategies that have significant potential to improve clinical outcome. Cocaine dependence is a multifaceted disorder with distinct clinical components that may respond to different pharmacologic approaches. Pharmacologic strategies for this disorder include blocking euphoria, reducing withdrawal and negative mood symptoms, ameliorating craving, and enhancing the prefrontal cortical function that seems to be impaired in cocaine-dependent patients. One medication may not be sufficient to treat these diverse elements of cocaine dependence because preliminary studies report efficacy with medications that have opposite actions on reward-related circuits. This review highlights pertinent advances in cocaine neurobiology, recent clinical trials, and controversies in the pharmacologic treatment of cocaine dependence.

Die neuropsychologischen Effekte von Kokain

Zusammenfassung: Kokainkonsumenten sind in der Regel entweder Gelegenheitskonsumenten mit geringem und relativ gut kontrollierbarem Kokainkonsum oder Kokainabhängige, die exzessiv große Mengen Kokain einnehmen (Binge-Taking). Neuropsychologische Untersuchungen bei Gelegenheitskonsumenten mit kleinen bis mittleren Kokaindosen, die geeignet sind, “Euphorie” und “Hochgefühle” auszulösen, ergaben bisher keine Hinweise auf neuropsychologische Funktionsbeeinträchtigungen in der akuten Phase. Vielmehr wurden in der akuten Kokainphase verbesserte Aufmerksamkeitsleistungen und schnellere Reaktionszeiten gemessen, die bis zum Beginn der postakuten Phase anhielten. Explizite Untersuchungen zur postakuten Phase oder Studien über die Effekte von Kokain in einem hohen Dosisbereich liegen derzeit nicht vor. Kokainabhängige weisen in einem Abstinenzzeitraum von bis zu mindestens 3 Monaten neuropsychologische, neurologische und unter Umständen auch psychiatrische Defizite auf. Deutliche Defizite abstinenter Kokainabhängiger wurden bei der Aufmerksamkeitsleistung, der Konzentration, der inhibitorischen Kontrolle und im Gedächtnis gefunden, wobei die verschiedenen Gedächtnistypen unterschiedlich betroffen sind. Kommt es bei Kokainabhängigen zu einer erneuten Kokaineinnahme, d.h. zu einer Binge-Phase, so ist unmittelbar danach in der so genannten Crash-Phase noch zusätzlich mit zum Teil schweren emotional-motivationalen Beeinträchtigungen zu rechnen.