P300 assessment of opiate and cocaine users: effects of detoxification and buprenorphine treatment

Psychosocial interventions for stimulant use disorder

BACKGROUND

Stimulant use disorder is a continuously growing medical and social burden without approved medications available for its treatment. Psychosocial interventions could be a valid approach to help people reduce or cease stimulant consumption. This is an update of a Cochrane review first published in 2016.

OBJECTIVES

To assess the efficacy and safety of psychosocial interventions for stimulant use disorder in adults.

SEARCH METHODS

We searched the Cochrane Drugs and Alcohol Group Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, three other databases, and two trials registers in September 2023. All searches included non-English language literature. We handsearched the references of topic-related systematic reviews and the included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing any psychosocial intervention with no intervention, treatment as usual (TAU), or a different intervention in adults with stimulant use disorder.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included a total of 64 RCTs (8241 participants). Seventy-three percent of studies included participants with cocaine or crack cocaine use disorder; 3.1% included participants with amphetamine use disorder; 10.9% included participants with methamphetamine use disorder; and 12.5% included participants with any stimulant use disorder. In 18 studies, all participants were in methadone maintenance treatment. In our primary comparison of any psychosocial treatment to no intervention, we included studies which compared a psychosocial intervention plus TAU to TAU alone. In this comparison, 12 studies evaluated cognitive behavioural therapy (CBT), 27 contingency management, three motivational interviewing, one study looked at psychodynamic therapy, and one study evaluated CBT plus contingency management. We also compared any psychosocial intervention to TAU. In this comparison, seven studies evaluated CBT, two contingency management, two motivational interviewing, and one evaluated a combination of CBT plus motivational interviewing. Seven studies compared contingency management reinforcement related to abstinence versus contingency management not related to abstinence. Finally, seven studies compared two different psychosocial approaches. We judged 65.6% of the studies to be at low risk of bias for random sequence generation and 19% at low risk for allocation concealment. Blinding of personnel and participants was not possible for the type of intervention, so we judged all the studies to be at high risk of performance bias for subjective outcomes but at low risk for objective outcomes. We judged 22% of the studies to be at low risk of detection bias for subjective outcomes. We judged most of the studies (69%) to be at low risk of attrition bias. When compared to no intervention, we found that psychosocial treatments: reduce the dropout rate (risk ratio (RR) 0.82, 95% confidence interval (CI) 0.74 to 0.91; 30 studies, 4078 participants; high-certainty evidence); make little to no difference to point abstinence at the end of treatment (RR 1.15, 95% CI 0.94 to 1.41; 12 studies, 1293 participants; high-certainty evidence); make little to no difference to point abstinence at the longest follow-up (RR 1.22, 95% CI 0.91 to 1.62; 9 studies, 1187 participants; high-certainty evidence); probably increase continuous abstinence at the end of treatment (RR 1.89, 95% CI 1.20 to 2.97; 12 studies, 1770 participants; moderate-certainty evidence); may make little to no difference in continuous abstinence at the longest follow-up (RR 1.14, 95% CI 0.89 to 1.46; 4 studies, 295 participants; low-certainty evidence); reduce the frequency of drug intake at the end of treatment (standardised mean difference (SMD) -0.35, 95% CI -0.50 to -0.19; 10 studies, 1215 participants; high-certainty evidence); and increase the longest period of abstinence (SMD 0.54, 95% CI 0.41 to 0.68; 17 studies, 2118 participants; high-certainty evidence). When compared to TAU, we found that psychosocial treatments reduce the dropout rate (RR 0.79, 95% CI 0.65 to 0.97; 9 studies, 735 participants; high-certainty evidence) and may make little to no difference in point abstinence at the end of treatment (RR 1.67, 95% CI 0.64 to 4.31; 1 study, 128 participants; low-certainty evidence). We are uncertain whether they make any difference in point abstinence at the longest follow-up (RR 1.31, 95% CI 0.86 to 1.99; 2 studies, 124 participants; very low-certainty evidence). Compared to TAU, psychosocial treatments may make little to no difference in continuous abstinence at the end of treatment (RR 1.18, 95% CI 0.92 to 1.53; 1 study, 128 participants; low-certainty evidence); probably make little to no difference in the frequency of drug intake at the end of treatment (SMD -1.17, 95% CI -2.81 to 0.47, 4 studies, 479 participants, moderate-certainty evidence); and may make little to no difference in the longest period of abstinence (SMD -0.16, 95% CI -0.54 to 0.21; 1 study, 110 participants; low-certainty evidence). None of the studies for this comparison assessed continuous abstinence at the longest follow-up. Only five studies reported harms related to psychosocial interventions; four of them stated that no adverse events occurred.

AUTHORS' CONCLUSIONS

This review's findings indicate that psychosocial treatments can help people with stimulant use disorder by reducing dropout rates. This conclusion is based on high-certainty evidence from comparisons of psychosocial interventions with both no treatment and TAU. This is an important finding because many people with stimulant use disorders leave treatment prematurely. Stimulant use disorders are chronic, lifelong, relapsing mental disorders, which require substantial therapeutic efforts to achieve abstinence. For those who are not yet able to achieve complete abstinence, retention in treatment may help to reduce the risks associated with stimulant use. In addition, psychosocial interventions reduce stimulant use compared to no treatment, but they may make little to no difference to stimulant use when compared to TAU. The most studied and promising psychosocial approach is contingency management. Relatively few studies explored the other approaches, so we cannot rule out the possibility that the results were imprecise due to small sample sizes.

Gender-Specific Interactions in a Visual Object Recognition Task in Persons with Opioid Use Disorder

Opioid use disorder (OUD)-associated overdose deaths have reached epidemic proportions worldwide over the past two decades, with death rates for men reported at twice the rate for women. Using a controlled, cross-sectional, age-matched (18-56 y) design to better understand the cognitive neuroscience of OUD, we evaluated the electroencephalographic (EEG) responses of male and female participants with OUD vs. age- and gender-matched non-OUD controls during a simple visual object recognition Go/No-Go task. Overall, women had significantly slower reaction times (RTs) than men. In addition, EEG N200 and P300 event-related potential (ERP) amplitudes for non-OUD controls were significantly larger for men, while their latencies were significantly shorter than for women. However, while N200 and P300 amplitudes were not significantly affected by OUD for either men or women in this task, latencies were also affected differentially in men vs. women with OUD. Accordingly, for both N200 and P300, male OUD participants exhibited longer latencies while female OUD participants exhibited shorter ones than in non-OUD controls. Additionally, robust oscillations were found in all participants during a feedback message associated with performance in the task. Although alpha and beta power during the feedback message were significantly greater for men than women overall, both alpha and beta oscillations exhibited significantly lower power in all participants with OUD. Taken together, these findings suggest important gender by OUD differences in cognitive processing and reflection of performance in this simple visual task.

Differences in cognitive deficits in patients with methamphetamine and heroin use disorder compared with healthy controls in a Chinese Han population

BACKGROUND AND AIMS

To date, the pattern of heroin- and methamphetamine-induced cognitive impairment is unclear, especially in the Chinese population. The aim of this study was to compare the similarity and heterogeneity of cognitive impairment between heroin and methamphetamine-dependent patients and to link cognitive impairment to drug-related variables.

METHODS

567 pure methamphetamine patients, 78 pure heroin patients and 201 healthy volunteers participated in this study. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was used to assess cognitive function including immediate memory, visuospatial/constructional index, language, attention, delayed memory, and total scores.

RESULTS

Methamphetamine-dependent and heroin-dependent patients performed significantly worse on all RBANS subtest and total scores (all p < 0.05). Moreover, methamphetamine-dependent patients had more delayed memory impairment than heroin-dependent patients (p = 0.02). In addition, some drug-related variables, such as duration of abstinence, age at first drug use, and duration of drug use, were independently associated with memory and visuospatial/constructional index in methamphetamine patients (all p < 0.05). In contrast, none of the drug-related variables were associated with cognitive performance in heroin patients (all p > 0.05).

CONCLUSIONS

Chronic heroin and methamphetamine patients may exhibit different patterns of cognitive deficits.

Bouncing back: Brain rehabilitation amid opioid and stimulant epidemics

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Frontoparietal event related potentials predict/track recovery.

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Frontostriatal functional magnetic resonance imaging signals predict/track recovery.

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Transcranial magnetic left prefrontal stimulation reduces craving and drug use.

Recent methamphetamine and opioid use epidemics are a major public health concern. Chronic stimulant and opioid use are characterized by significant psychosocial, physical and mental health costs, repeated relapse, and heightened risk of early death. Neuroimaging research highlights deficits in brain processes and circuitry that are linked to responsivity to drug cues over natural rewards as well as suboptimal goal-directed decision-making. Despite the need for interventions, little is known about (1) how the brain changes with prolonged abstinence or as a function of various treatments; and (2) how symptoms change as a result of neuromodulation. This review focuses on the question: What do we know about changes in brain function during recovery from opioids and stimulants such as methamphetamine and cocaine? We provide a detailed overview and critique of published research employing a wide array of neuroimaging methods – functional and structural magnetic resonance imaging, electroencephalography, event-related potentials, diffusion tensor imaging, and multiple brain stimulation technologies along with neurofeedback – to track or induce changes in drug craving, abstinence, and treatment success in stimulant and opioid users. Despite the surge of methamphetamine and opioid use in recent years, most of the research on neuroimaging techniques for recovery focuses on cocaine use. This review highlights two main findings: (1) interventions can lead to improvements in brain function, particularly in frontal regions implicated in goal-directed behavior and cognitive control, paired with reduced drug urges/craving; and (2) the targeting of striatal mechanisms implicated in drug reward may not be as cost-effective as prefrontal mechanisms, given that deep brain stimulation methods require surgery and months of intervention to produce effects. Overall, more studies are needed to replicate and confirm findings, particularly for individuals with opioid and methamphetamine use disorders.

Single-Trial Mechanisms Underlying Changes in Averaged P300 ERP Amplitude and Latency in Military Service Members After Combat Deployment

Attenuation in P300 amplitude has been characterized in a wide range of neurological and psychiatric disorders such as dementia, schizophrenia, and posttraumatic stress disorder (PTSD). However, it is unclear whether the attenuation observed in the averaged event-related potential (ERP) is due to the reduction of neural resources available for cognitive processing, the decreased consistency of cognitive resource allocation, or the increased instability of cognitive processing speed. In this study, we investigated this problem by estimating single-trial P300 amplitude and latency using a modified Woody filter and examined the relation between amplitudes and latencies from the single-trial level to the averaged ERP level. ERPs were recorded from 30 military service members returning from combat deployment at two time points separated by 6 or 12 months. A conventional visual oddball task was used to elicit P300. We observed that the extent of changes in the within-subject average P300 amplitude over time was significantly correlated with the amount of change in three single-trial measures: (1) the latency variance of the single-trial P300 (r = -0.440, p = 0.0102); (2) the percentage of P300-absent trials (r = -0.488, p = 0.005); and (3) the consistent variation of the single-trial amplitude (r = 0.571, p = 0.0022). These findings suggest that there are multiple underlying mechanisms on the single-trial level that contribute to the changes in amplitudes seen at the averaged ERP level. The changes between the first and second assessments were quantified with the intraclass correlation coefficient, the standard error of measurement and the minimal detectable difference. The unique population, the small sample size and the large fraction of participants lost to follow up precludes generalizations of these measures of change to other populations.

Cognitive Memory Comparison Between Tinnitus and Normal Cases Using Event-Related Potentials

About 20 percent of people above 60 years old suffer from tinnitus though no definitive treatment has been found for it. Evaluation of electrical brain activity using Event-Related Potentials (ERPs) is one of the methods to investigate the underlying reasons of tinnitus perception. Previous studies using ERPs suggest that the precognitive memory in tinnitus groups is negatively affected in comparison to the normal hearing groups. In this study, cognitive memory has been assessed using visual and auditory P300 response with oddball paradigm. Fifteen chronic tinnitus subjects and six normal hearing subjects participated in the experiment. T-test with significance level of 0.05 was applied on amplitude and latency of auditory and visual P300 for all electroencephalography (EEG) channels separately to compare tinnitus and normal hearing groups where the tinnitus group showed meaningful lower amplitude of auditory P300 peak in three EEG channels.

Buprenorphine requires concomitant activation of NOP and MOP receptors to reduce cocaine consumption

Buprenorphine's clinical use is approved for the treatment of heroin addiction; however, evidence supporting its efficacy in cocaine abuse also exists. While for heroin it has been demonstrated that the effect of buprenorphine is mediated by its ability to activate μ-opioid peptide receptor (MOP) receptors, the mechanism through which it attenuates cocaine intake remains elusive. We explored this mechanism using operant models where rodents were trained to chronically self-administer cocaine for 2 hours daily. Buprenorphine (0.3, 1.0 and 3.0 mg/kg) given intraperitoneally 90 minutes before access to cocaine significantly and dose dependently reduced its intake. Pre-treatment with naltrexone or with the selective nociceptin/orphanin FQ peptide (NOP) antagonist SB-612111 did not prevent buprenorphine-induced reduction of cocaine intake. However, when naltrexone and SB-612111 were combined, the effect of buprenorphine on cocaine was completely prevented. To confirm that co-activation of MOP and NOP receptors is the underlying mechanism through which buprenorphine reduces cocaine intake, three compounds, namely, AT-034, AT-201 and AT-202, with a range of affinity and intrinsic activity profiles for MOP and NOP receptors, but weak ability for kappa-opioid peptide receptor (KOP) transmission, were tested. Consistent with our hypothesis based on buprenorphine's effects, results demonstrated that AT-034 and AT-201, which co-activate MOP and NOP receptors, reduced cocaine self-administration like buprenorphine. AT-202, which selectively stimulates NOP receptors, was not effective. Together, these data demonstrate that for buprenorphine, co-activation of MOP and NOP receptors is essential to reduce cocaine consumption. These results open new vistas on the treatment of cocaine addiction by developing compounds with mixed MOP/NOP agonist properties.

Psychosocial interventions for psychostimulant misuse

BACKGROUND

Psychostimulant misuse is a continuously growing medical and social burden. There is no evidence proving the efficacy of pharmacotherapy. Psychosocial interventions could be a valid approach to help patients in reducing or ceasing drug consumption.

OBJECTIVES

To assess the effects of psychosocial interventions for psychostimulant misuse in adults.

SEARCH METHODS

We searched the Cochrane Drugs and Alcohol Group Specialised Register (via CRSLive); Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; CINAHL; Web of Science and PsycINFO, from inception to November 2015. We also searched for ongoing and unpublished studies via ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (apps.who.int/trialsearch/).All searches included non-English language literature. We handsearched references of topic-related systematic reviews and the included studies.

SELECTION CRITERIA

We included randomised controlled trials comparing any psychosocial intervention with no intervention, treatment as usual (TAU) or a different intervention in adults with psychostimulant misuse or dependence.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included a total of 52 trials (6923 participants).The psychosocial interventions considered in the studies were: cognitive behavioural therapy (19 studies), contingency management (25 studies), motivational interviewing (5 studies), interpersonal therapy (3 studies), psychodynamic therapy (1 study), 12-step facilitation (4 studies).We judged most of the studies to be at unclear risk of selection bias; blinding of personnel and participants was not possible for the type of intervention, so all the studies were at high risk of performance bias with regard to subjective outcomes; the majority of studies did not specify whether the outcome assessors were blind. We did not consider it likely that the objective outcomes were influenced by lack of blinding.The comparisons made were: any psychosocial intervention versus no intervention (32 studies), any psychosocial intervention versus TAU (6 studies), and one psychosocial intervention versus an alternative psychosocial intervention (13 studies). Five of included studies did not provide any useful data for inclusion in statistical synthesis.We found that, when compared to no intervention, any psychosocial treatment: reduced the dropout rate (risk ratio (RR): 0.83, 95% confidence interval (CI) 0.76 to -0.91, 24 studies, 3393 participants, moderate quality evidence); increased continuous abstinence at the end of treatment (RR: 2.14, 95% CI 1.27 to -3.59, 8 studies, 1241 participants, low quality evidence); did not significantly increase continuous abstinence at the longest follow-up (RR: 2.12, 95% CI 0.77 to -5.86, 4 studies, 324 participants, low quality evidence); significantly increased the longest period of abstinence: (standardised mean difference (SMD): 0.48, 95% CI 0.34 to 0.63, 10 studies, 1354 participants, high quality evidence). However, it should be noted that the in the vast majority of the studies in this comparison the specific psychosocial treatment assessed in the experimental arm was given in add on to treatment as usual or to another specific psychosocial or pharmacological treatment which was received by both groups. So, many of the control groups in this comparison were not really untreated. Receiving some amount of treatment is not the same as not receiving any intervention, so we could argue that the overall effect of the experimental psychosocial treatment could be smaller if given in add on to TAU or to another intervention than if given to participants not receiving any intervention; this could translate to a smaller magnitude of the effect of the psychosocial intervention when it is given in add on.When compared to TAU, any psychosocial treatment reduced dropout rate (RR: 0.72, 95% CI 0.59 to 0.89, 6 studies, 516 participants, moderate quality evidence), did not increase continuous abstinence at the end of treatment (RR: 1.27, 95% CI 0.94 to 1.72, 2 studies, 224 participants, low quality evidence), did not increase longest period of abstinence (MD -3.15 days, 95% CI -10.35 to 4.05, 1 study, 110 participants, low quality evidence). No studies in this comparison assessed the outcome of continuous abstinence at longest follow-up.There were few studies comparing two or more psychosocial interventions, with small sample sizes and considerable heterogeneity in terms of the types of interventions assessed. None reported significant results.None of the studies reported harms related to psychosocial interventions.

AUTHORS' CONCLUSIONS

The addition of any psychosocial treatment to treatment as usual (usually characterised by group counselling or case management) probably reduces the dropout rate and increases the longest period of abstinence. It may increase the number of people achieving continuous abstinence at the end of treatment, although this might not be maintained at longest follow-up. The most studied and the most promising psychosocial approach to be added to treatment as usual is probably contingency management. However, the other approaches were only analysed in a few small studies, so we cannot rule out the possibility that the results were not significant because of imprecision. When compared to TAU, any psychosocial treatment may improve adherence, but it may not improve abstinence at the end of treatment or the longest period of abstinence.The majority of the studies took place in the United States, and this could limit the generalisability of the findings, because the effects of psychosocial treatments could be strongly influenced by the social context and ethnicity. The results of our review do not answer the most relevant clinical question, demonstrating which is the most effective type of psychosocial approach.Further studies should directly compare contingency management with the other psychosocial approaches.

Resting EEG and ERPs findings in methadone-substituted opiate users: a review

Methadone has been used to treat opiate dependence since the mid-1960s. Despite its clinical effectiveness there is evidence from neuropsychological studies demonstrating that its long-term use might have negative effects on cognition. Nevertheless, it remains uncertain whether the observed cognitive impairments in patients undertaking methadone maintenance treatment (MMT) are solely attributable to the pharmacological effects of methadone, as suggested by some researchers. Determining the effects of MMT on neuropsychological function using electroencephalography (EEG) combined with event-related potentials (ERP) has been used infrequently. However EEG and ERP provide a means of closely examining information processing to determine whether MMT induces any deficits. The purpose of this review was to investigate whether psychophysiological evidence supports cognitive impairment in association with MMT by focusing on research using EEG and ERPs. The findings of EEG studies to date appear not support the notion that cognitive impairments are attributable to the specific pharmacological effects of methadone suggested by some neuropsychological studies. However, due to the methodological deficits and limited number of the studies, any conclusion based on the findings of the existing EEG studies should be avoided.

Auditory event-related potentials in methadone substituted opiate users

The effects of methadone maintenance treatment (MMT) on neurophysiological function are unclear. Using an auditory oddball paradigm, event-related potential (ERP) amplitudes and latencies were measured in 32 patients undertaking MMT, 17 opiate users who were addicted but not receiving substitution treatment and 25 healthy control subjects. Compared with healthy control subjects, the MMT and opiate user groups showed an increased P200 amplitude in response to target stimuli. The opiate user group also exhibited a decreased amplitude and an increased latency of N200, and a greater number of task-related errors than either healthy control subjects or patients undertaking MMT. There were no significant group differences in the P300 amplitude. However, it is noteworthy that the frontal P300 amplitude of the MMT group was greater than that of opiate users or healthy controls. Our findings suggest that altered sensory information processing associated with a history of opiate use remains in patients undertaking MMT. However, there are less marked ERP abnormalities in those receiving MMT than in active opiate users. The deficits in information processing associated with illicit opiate use are likely to be reduced during MMT.

The opioid receptors as targets for drug abuse medication

The endogenous opioid system is largely expressed in the brain, and both endogenous opioid peptides and receptors are present in areas associated with reward and motivation. It is well known that this endogenous system plays a key role in many aspects of addictive behaviours. The present review summarizes the modifications of the opioid system induced by chronic treatment with drugs of abuse reported in preclinical and clinical studies, as well as the action of opioid antagonists and agonists on the reinforcing effects of drugs of abuse, with therapeutic perspectives. We have focused on the effects of chronic psychostimulants, alcohol and nicotine exposure. Taken together, the changes in both opioid peptides and opioid receptors in different brain structures following acute or chronic exposure to these drugs of abuse clearly identify the opioid system as a potential target for the development of effective pharmacotherapy for the treatment of addiction and the prevention of relapse.

WITHDRAWN: Psychosocial interventions for cocaine and psychostimulant amphetamines related disorders

Review withdrawn as the Cochrane Funding Arbitration Panel found this review non‐compliant with the Cochrane’s commercial sponsorship policy. The new author team will update and replace this review.

The editorial group responsible for this previously published document have withdrawn it from publication.

Neuropsychological performance of methadone-maintained opiate users

Methadone maintenance treatment (MMT) has been used to treat opiate dependence since the mid-1960s. Previous studies have investigated the effects of methadone on cognitive function however the findings have been inconsistent. Some report a complete absence of deficits while others report different types of cognitive impairment. Our research aimed to investigate the effects of MMT on cognitive function by comparing the performance of patients currently enrolled in MMT (n=32) with opiate-dependent subjects (n=17) and healthy control subjects (n=25) on a computerised neuropsychological test battery. Both the patients undertaking MMT and the opiate users showed less efficient interaction between visual searching and manually connecting digits and letters during the Switching of Attention Task than the healthy control subjects (F(2,64)=3.25, p=0.05), which indicates deficits in information processing. Nevertheless, the performance of the MMT group was similar to that of healthy control subjects in all other tasks, in contrast to the group of opiate users who performed poorly when compared to healthy control subjects during tests of attention (mean difference (MD)=2.8, 95% confidence interval (CI) (0.9-4.7), p=0.001) and executive function (MD=5.9, 95% CI (1.3-10.5), p=0.007). These findings suggest that cognitive function in patients undertaking MMT is improved compared to those dependent on illicit opiates.

Event-related potentials in substance use disorders: a narrative review based on articles from 1984 to 2012

Mechanisms that mediate the transition from occasional, controlled, drug use to the impaired control that characterizes severe dependence are still a matter of investigation. The etiology of substance use disorders (SUDs) is complex, and in this context of complexity, the concept of "endophenotype," has gained extensive popularity in recent years. The main aim of endophenotypes is to provide a simpler, more proximal target to discover the biological underpinnings of a psychiatric syndrome. In this view, neurocognitive and neurophysiological impairments that suggest functional impairments associated with SUDs have been proposed as possible endophenotypes. Because of its large amplitude and relatively easy elicitation, the most studied of the cognitive brain event-related potentials (ERPs), the P300 component, has been proposed as one possible candidate. However, if a P300 amplitude alteration is a common finding in SUDs, it is also observable in other psychiatric afflictions, suggesting that the associations found may just reflect a common measure of brain dysfunction. On this basis, it has been proposed that a multivariate endophenotype, based on a weighted combination of electrophysiological features, may provide greater diagnostic classification power than any single endophenotype. The rationale for investigating multiple features is to show that combining them provides extra useful information that is not available in the individual features, leading ultimately to a multivariate phenotype.The aim of the present article is to outline the potential usefulness of this kind of "combined electrophysiological procedure" applied to SUDs. We present a review of ERP studies, combining data from people with SUD, family members, and normal control subjects, to verify whether the combination of 4ERPs (P50, MMN, P300, and N400) may produce profiles of cortical anomalies induced by different types of SUD (alcohol vs cocaine vs cannabis vs heroin).

Influence of alcohol use on neural response to Go/No-Go task in college drinkers

Impaired inhibition of prepotent motor response may represent an important risk factor for alcoholism. Alcohol use may also increase impulsive behavior, including impaired response inhibition. Little is known about the brain function underlying response inhibition among college-age drinkers based on their drinking patterns, despite college-age drinkers demonstrating high rates of alcohol-use disorders. Our major objective was to compare behavior and associated brain activity measured with fMRI during a response-inhibition task in matched heavy- and light-alcohol-drinking college students. Participants were light (N=36) and heavy (N=56) drinkers, aged 18-20 years. We characterized blood oxygen level-dependent (BOLD) responses, while participants performed an fMRI Go/No-Go task to quantify inhibitory behavior and brain activity. Behaviorally, group performance differences were observed for Go correct-hit and No-Go false-alarm reaction times with increased reaction times in heavy compared with light drinkers. During fMRI No-Go correct rejections, light drinkers exhibited greater BOLD response than did heavy drinkers in left supplementary motor area (SMA), bilateral parietal lobule, right hippocampus, bilateral middle frontal gyrus, left superior temporal gyrus, and cingulate gyrus/anterior cingulate cortex (Brodmann area 24). Group differences in Go/No-Go-related regional activations correlated with alcohol- and impulsivity-related measures. These findings suggest that heavy alcohol drinkers may have dysfunction in brain regions underlying attention and response inhibition, leading to diminished abilities to suppress prepotent responding. The extent to which these tendencies relate to impulsive decision-making and behaviors in real-life settings and may guide intervention development warrants additional investigation.

Alpha-synuclein and heroin craving in opiate-dependent patients on injectable heroin maintenance

Research suggests that alpha-synuclein (SNCA) and NACP-Rep1, a polymorphic complex microsatellite repeat ~10 kb upstream of the SNCA gene translational start, may be involved in substance-use behaviors and craving. This study was the first to examine the effects of diacetylmorphine (DAM) on peripheral SNCA protein expression along with craving in opiate-dependent patients and to compare their NACP-Rep1 allele lengths with those of healthy controls. Using an experimental design, opiate-dependent patients on injectable heroin maintenance were investigated at four time points, twice pre- and post-injection of DAM. SNCA protein levels of 30 DAM-maintained patients were measured using enzyme-linked immunosorbent assay. Participant-rated effects were assessed in 42 patients by Tiffany's Heroin Craving Questionnaire (HCQ), Gossop's Short Opiate Withdrawal Scale and Visual Analogs. NACP-Rep1 alleles of 42 patients and 101 controls were analyzed. One-way repeated-measures ANOVAs provided significant overall effects for SNCA protein content (P = 0.028), craving (P < 0.001), withdrawal symptomatology (P < 0.001) and mood (P < 0.001), indicating that DAM injections may not only reduce craving but also SNCA protein expression. However, there was no association between protein expression and craving. Relative to controls, patients had significantly longer NACP-Rep1 alleles (P < 0.001). NACP-Rep1 allele lengths correlated positively with HCQ total scores averaged across all time points (r = 0.420; P = 0.006) as well as with post-DAM HCQ total scores in the morning (r = 0.488, P = 0.001) and afternoon (r = 0.423, P = 0.005). The findings provide evidence of a contributory role of SNCA and NACP-Rep1 for opiate dependence.

Sensitivity to monetary reward is most severely compromised in recently abstaining cocaine addicted individuals: a cross-sectional ERP study

Recent studies suggest that drug-addicted individuals have a dampened cortical response to non-drug rewards. However, it remains unclear whether recency of drug use impacts this impairment. Therefore, in this event-related potential study, recency of cocaine use was objectively determined by measuring cocaine in urine on study day. Thirty-five individuals with current cocaine use disorder [CUD: 21 testing positive (CUD+) and 14 testing negative (CUD-) for cocaine in urine] and 23 healthy controls completed a sustained attention task with graded monetary incentives (0¢, 1¢ and 45¢). Unlike in controls, in both CUD subgroups P300 amplitude was not modulated by the varying amounts of money and the CUD- showed the most severe impairment as documented by the lowest P300 amplitudes and task accuracy. Moreover, while recency of drug use was associated with better accuracy and higher P300 amplitudes, chronic drug use was associated with lower sensitivity to money. These results extend our previous findings of decreased sustained sensitivity to monetary reward in CUD+ to recently abstaining individuals, where level of impairment was most severe. Taken together, these results support the self-medication hypothesis, where CUD may be self-administering cocaine to avoid or compensate for underlying cognitive and emotional difficulties albeit with a long-term detrimental effect on sensitivity to non-drug reward.

Neuroimaging for drug addiction and related behaviors

In this review, we highlight the role of neuroimaging techniques in studying the emotional and cognitive-behavioral components of the addiction syndrome by focusing on the neural substrates subserving them. The phenomenology of drug addiction can be characterized by a recurrent pattern of subjective experiences that includes drug intoxication, craving, bingeing, and withdrawal with the cycle culminating in a persistent preoccupation with obtaining, consuming, and recovering from the drug. In the past two decades, imaging studies of drug addiction have demonstrated deficits in brain circuits related to reward and impulsivity. The current review focuses on studies employing positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and electroencephalography (EEG) to investigate these behaviors in drug-addicted human populations. We begin with a brief account of drug addiction followed by a technical account of each of these imaging modalities. We then discuss how these techniques have uniquely contributed to a deeper understanding of addictive behaviors.

Neurocognitive deficits in male alcoholics: an ERP/sLORETA analysis of the N2 component in an equal probability Go/NoGo task

In alcoholism research, studies concerning time-locked electrophysiological aspects of response inhibition have concentrated mainly on the P3 component of the event-related potential (ERP). The objective of the present study was to investigate the N2 component of the ERP to elucidate possible brain dysfunction related to the motor response and its inhibition using a Go/NoGo task in alcoholics. The sample consisted of 78 abstinent alcoholic males and 58 healthy male controls. The N2 peak was compared across group and task conditions. Alcoholics showed significantly reduced N2 peak amplitudes compared to normal controls for Go as well as NoGo task conditions. Control subjects showed significantly larger NoGo than Go N2 amplitudes at frontal regions, whereas alcoholics did not show any differences between task conditions at frontal regions. Standardized low resolution electromagnetic tomography analysis (sLORETA) indicated that alcoholics had significantly lower current density at the source than control subjects for the NoGo condition at bilateral anterior prefrontal regions, whereas the differences between groups during the Go trials were not statistically significant. Furthermore, NoGo current density across both groups revealed significantly more activation in bilateral anterior cingulate cortical (ACC) areas, with the maximum activation in the right cingulate regions. However, the magnitude of this difference was much less in alcoholics compared to control subjects. These findings suggest that alcoholics may have deficits in effortful processing during the motor response and its inhibition, suggestive of possible frontal lobe dysfunction.

The P300 event-related brain potential as a neurobiological endophenotype for substance use disorders: a meta-analytic investigation

Endophenotypes are intermediate phenotypes on the putative causal pathway from genotype to phenotype and can aid in discovering the genetic etiology of a disorder. There are currently very few suitable endophenotypes available for substance use disorders (SUD). The amplitude of the P300 event-related brain potential is a possible candidate. The present study determined whether the P300 amplitude fulfils two fundamental criteria for an endophenotype: (1) an association with the disorder (disease marker), and (2) presence in unaffected biological relatives of those who have the disorder (vulnerability marker). For this purpose, two separate meta-analyses were performed. Meta-analysis 1 investigated the P300 amplitude in relation to SUD in 39 studies and Meta-analysis 2 investigated P300 amplitude in relation to a family history (FH+) of SUD in 35 studies. The findings indicate that a reduced P300 amplitude is significantly associated with SUD (d=0.51) and, though to a lesser extent, with a FH+ of SUD (d=0.28). As a disease maker, the association between reduced P300 amplitude and SUD is significantly larger for participants that were exclusively recruited from treatment facilities (d=0.67) than by other methods (i.e., community samples and family studies; d=0.45 and 0.32, respectively), and larger for abstinent SUD patients (d=0.71) than for current substance users (d=0.37). Furthermore, in contrast to FH+ males, a P300 amplitude reduction seems not to be present in FH+ females (d=-0.07). Taken together, these results suggest that P300 amplitude reduction can be both a useful disease and vulnerability marker and is a promising neurobiological endophenotype for SUD, though only in males. Implications and future directions are discussed.

Neurocognitive impairment and HIV risk factors: a reciprocal relationship

Cognitive impairment among populations at risk for HIV poses a significant barrier to managing risk behaviors. The impact of HIV and several cofactors, including substance abuse and mental illness, on cognitive function is discussed in the context of HIV risk behaviors, medication adherence, and risk-reduction interventions. Literature suggests that cognitive impairment is intertwined in a close, reciprocal relationship with both risk behaviors and medication adherence. Not only do increased risk behaviors and suboptimal adherence exacerbate cognitive impairment, but cognitive impairment also reduces the effectiveness of interventions aimed at optimizing medication adherence and reducing risk. In order to be effective, risk-reduction interventions must therefore take into account the impact of cognitive impairment on learning and behavior.

Association of P3 amplitude to treatment completion in substance dependent individuals

Individuals with substance use disorders typically show reduced amplitudes of the P3 component of the evoked potential and high scores on impulsivity and aggression measures. The present study investigated the usefulness of P3 amplitude, addiction severity and impulsivity as predictors of treatment completion in substance dependence. Forty-four participants (8 women), between the ages of 19 and 61 years old, who met DSM-IV-TR Axis I substance/alcohol dependence criteria were recruited for the present study. All participants were currently residents at a local substance abuse facility receiving treatment and had been free of all drug toxicity for a minimum of 21 days. The P3 was evoked using a standard rotated-heads oddball paradigm. Significantly reduced P3 amplitude at Pz was found in patients who did not complete treatment compared to those who did. P3 amplitude at Pz elicited by target stimuli correctly identified 76.2% of those who did complete the treatment and 46.7% of those who did not.

Auditory event-related potentials, bispectral index, and entropy for the discrimination of different levels of sedation in intensive care unit patients

BACKGROUND

Sedation protocols, including the use of sedation scales and regular sedation stops, help to reduce the length of mechanical ventilation and intensive care unit stay. Because clinical assessment of depth of sedation is labor-intensive, performed only intermittently, and interferes with sedation and sleep, processed electrophysiological signals from the brain have gained interest as surrogates. We hypothesized that auditory event-related potentials (ERPs), Bispectral Index (BIS), and Entropy can discriminate among clinically relevant sedation levels.

METHODS

We studied 10 patients after elective thoracic or abdominal surgery with general anesthesia. Electroencephalogram, BIS, state entropy (SE), response entropy (RE), and ERPs were recorded immediately after surgery in the intensive care unit at Richmond Agitation-Sedation Scale (RASS) scores of -5 (very deep sedation), -4 (deep sedation), -3 to -1 (moderate sedation), and 0 (awake) during decreasing target-controlled sedation with propofol and remifentanil. Reference measurements for baseline levels were performed before or several days after the operation.

RESULTS

At baseline, RASS -5, RASS -4, RASS -3 to -1, and RASS 0, BIS was 94 [4] (median, IQR), 47 [15], 68 [9], 75 [10], and 88 [6]; SE was 87 [3], 46 [10], 60 [22], 74 [21], and 87 [5]; and RE was 97 [4], 48 [9], 71 [25], 81 [18], and 96 [3], respectively (all P < 0.05, Friedman Test). Both BIS and Entropy had high variabilities. When ERP N100 amplitudes were considered alone, ERPs did not differ significantly among sedation levels. Nevertheless, discriminant ERP analysis including two parameters of principal component analysis revealed a prediction probability PK value of 0.89 for differentiating deep sedation, moderate sedation, and awake state. The corresponding PK for RE, SE, and BIS was 0.88, 0.89, and 0.85, respectively.

CONCLUSIONS

Neither ERPs nor BIS or Entropy can replace clinical sedation assessment with standard scoring systems. Discrimination among very deep, deep to moderate, and no sedation after general anesthesia can be provided by ERPs and processed electroencephalograms, with similar P(K)s. The high inter- and intraindividual variability of Entropy and BIS precludes defining a target range of values to predict the sedation level in critically ill patients using these parameters. The variability of ERPs is unknown.

The P300 event-related potential and its possible role as an endophenotype for studying substance use disorders: a review

The concept of endophenotypes has gained popularity in recent years. This is because of the potential that endophenotypes provide of measuring objective trait markers that are simpler to access and assess than complex behavioral disease phenotypes themselves. The simplicity, ease of measurement and the putative links to the etiology of the disease in the study of an endophenotype has the potential promise of unraveling the genetic basis of the disease in question. Of the various proposed endophenotypes, the P300 component of the event-related potential has been used in studies on alcoholism, schizophrenia and externalizing disorders. The current state of knowledge regarding the concept of endophenotypes, P300 and the validity of P300 as an endophenotype with special reference to substance use disorders is discussed in this review. The implications of the above are discussed.

Attentional Bias to Drug- and Stress-Related Pictorial Cues in Cocaine Addiction Comorbid with PTSD

Cocaine addiction places a specific burden on mental health services through its comorbidity with other psychiatric disorders. Treatment of patients with cocaine abuse is more complicated when addiction is co-occurring with PTSD. This study used dense-array event-related potential (ERP) technique to investigate whether the patients with this form of dual diagnosis display excessive reactivity to both trauma and drug cues as compared to neutral cues. Cue reactivity refers to a phenomenon in which individuals with a history of drug dependence exhibit verbal, physiological, and behavioral responses to cues associated with their preferred substance of abuse. This study explores ERP differences associated with cue-related responses to both drug and trauma cues in a three-category oddball task using neutral, drug-, and trauma-related pictorial stimuli. The study was conducted on 14 cocaine dependent subjects, 11 subjects with cocaine dependence comorbid with PTSD, and 9 age- and gender-matched control subjects. A 128 channel Electrical Geodesics EEG system was used to record ERP during the visual three-category oddball task with three categories (neutral, drug, stress) of affective pictures. Patients with cocaine dependence and PTSD, as compared to patients with only cocaine addiction and control subjects, showed excessive cue reactivity to both drug- and trauma-related visual stimuli. Most profound differences were found in the amplitude and latency of frontal P3a, and centro-parietal P3b ERP components. Group differences were found as well between patients with cocaine abuse (both addiction-only and dual diagnosis groups) vs. controls on most ERP measures for drug-related cues. We propose that the employed ERP cue reactivity variables could be used as valuable functional outcome measures in dually diagnosed drug addicts undergoing behavioral treatment.

Event-Related Potential Study of Executive Dysfunctions in a Speeded Reaction Task in Cocaine Addiction

This study used a flanker task with NoGo elements to investigate frontal executive function deficits in 19 cocaine abusers. The executive functions of interest in this study were cortical inhibition or ability to withhold motor response, the ability to select an appropriate response among several competing ones, the ability to inhibit inappropriate responses, and the ability to detect error and exercise corrective control. These processes were evaluated with specific frontal and parietal event-related potentials (ERP) registered during performance on this speeded reaction time task with conflicting motor response demands. Specifically we used behavioral response measures, stimulus-locked anterior (frontal N200, N450) ERP markers of conflict detection, response inhibition (NoGo-N2 and NoGo-P3), and response-locked error-related negativity (ERN) that represent different time points of signal classification, motor response conflict detection, response inhibition, and error monitoring processes. The results revealed that the higher-level executive motor control attributed to the prefrontal cortex is hypoactive in cocaine abusers, and therefore is incapable to effectively resolve response conflicts arising between the competing motor response alternatives. It was also demonstrated that the mesial frontal structures, such as the anterior cingulate cortex, implicated in motor response conflict detection and error monitoring functions were also compromised in addicts. It is reasonable to propose that a 'hypofunctional' prefrontal and midfrontal processing results in a diminished ability to effectively override strong habitual automated response tendencies controlled by the lower-level neural mechanisms triggered by the external stimuli. The results propose a neurobiological basis for the understanding why cocaine abusers are facing difficulties in controlling their drug-seeking and drug-taking behaviors, and why their drug-related habitual behavior is so vulnerable to be triggered by external (e.g., drug-related items and environment) cues.

Preliminary Feasibility and Efficacy of a Brief Motivational Intervention with Psychophysiological Feedback for Cocaine Abuse

Motivational interviewing (MI) with personalized feedback, particularly related to biological markers of risk or harm, has been found effective for alcohol use disorders, but has not been fully investigated in cocaine use disorders. A randomized, controlled pilot study evaluating the feasibility and preliminary efficacy of a brief MI intervention using EEG/ERP graphical feedback for cocaine abusers was conducted. Treatment-seeking cocaine abusers (N = 31) were randomly assigned to a two-session MI intervention or a minimal control condition. All participants received EEG assessments at intake and post-treatment. Results indicated that the MI intervention was feasible and the subjective impact of the EEG feedback was positive. Significant group differences in percentage of cocaine positive urine screens across the study were found, favoring the MI group; 84.9% for the control group and 62.6% in the MI group, p < .05. Further research must determine the specific conditions under which MI is most appropriate and efficacious.

Compromised sensitivity to monetary reward in current cocaine users: an ERP study

We studied modulation of the P300 by monetary reward expected to be received on a sustained attention task in 18 individuals with current cocaine use disorders (CUD) and 18 control subjects. Results in the controls revealed sensitivity to money as measured with P300 amplitude and speed of behavioral response and their intercorrelations. In contrast, despite generally faster P300 waveforms and higher self-reported interest in the task, individuals with CUD did not display these responses to money versus nonreward; at the behavioral level, this impairment correlated with frequency of recent cocaine use. These preliminary results suggest a compromised sensitivity to a secondary reinforcer in CUD. This deficit, which needs to be replicated in larger samples of people with currently active versus abstaining CUD, may underlie the compromised ability to advantageously modify behavior in response to changing inner motivations and environmental contingencies.

EEG biofeedback as a treatment for substance use disorders: review, rating of efficacy, and recommendations for further research

Electroencephalographic (EEG) biofeedback has been employed in substance use disorder (SUD) over the last three decades. The SUD is a complex series of disorders with frequent comorbidities and EEG abnormalities of several types. EEG biofeedback has been employed in conjunction with other therapies and may be useful in enhancing certain outcomes of therapy. Based on published clinical studies and employing efficacy criteria adapted by the Association for Applied Psychophysiology and Biofeedback and the International Society for Neurofeedback and Research, alpha theta training-either alone for alcoholism or in combination with beta training for stimulant and mixed substance abuse and combined with residential treatment programs, is probably efficacious. Considerations of further research design taking these factors into account are discussed and descriptions of contemporary research are given.

Auditory target processing in methadone substituted opiate addicts: the effect of nicotine in controls

BACKGROUND

The P300 component of the auditory evoked potential is an indicator of attention dependent target processing. Only a few studies have assessed cognitive function in substituted opiate addicts by means of evoked potential recordings. In addition, P300 data suggest that chronic nicotine use reduces P300 amplitudes. While nicotine and opiate effects combine in addicted subjects, here we investigated the P300 component of the auditory event related potential in methadone substituted opiate addicts with and without concomitant non-opioid drug use in comparison to a group of control subjects with and without nicotine consumption.

METHODS

We assessed 47 opiate addicted out-patients under current methadone substitution and 65 control subjects matched for age and gender in an 2-stimulus auditory oddball paradigm. Patients were grouped for those with and without additional non-opioid drug use and controls were grouped for current nicotine use. P300 amplitude and latency data were analyzed at electrodes Fz, Cz and Pz.

RESULTS

Patients and controls did not differ with regard to P300 amplitudes and latencies when whole groups were compared. Subgroup analyses revealed significantly reduced P300 amplitudes in controls with nicotine use when compared to those without. P300 amplitudes of methadone substituted opiate addicts were in between the two control groups and did not differ with regard to additional non-opioid use. Controls with nicotine had lower P300 amplitudes when compared to patients with concomitant non-opioid drugs. No P300 latency effects were found.

CONCLUSION

Attention dependent target processing as indexed by the P300 component amplitudes and latencies is not reduced in methadone substituted opiate addicts when compared to controls. The effect of nicotine on P300 amplitudes in healthy subjects exceeds the effects of long term opioid addiction under methadone substitution.

Impaired pre-attentive auditory processing in opioid dependence with and without benzodiazepine co-dependence revealed by combined magnetoencephalography and electroencephalography

Cognitive dysfunctions may be a significant factor in drug-seeking behavior, reducing the efficiency of rehabilitation in opioid dependence. Neurophysiological basis of these dysfunctions is poorly understood. 21 opioid-dependent patients and 15 healthy controls with no experience of illicit drugs were studied with simultaneous electroencephalography (EEG) and magnetoencephalography (MEG). Among opioid dependents 15 were benzodiazepine co-dependent. In a passive oddball paradigm, a train of 700-Hz standard tones (80%), presented to the left ear, was occasionally interrupted by infrequent deviants, which were either 600-Hz or 400-Hz pure tones or complex novel sounds. The auditory evoked potentials (AEP) and fields (AEF) were analyzed. The strength of the N1m dipoles was enhanced in patients with benzodiazepine co-dependence, but the latency of the response or the source location was not changed. A delay of mismatch negativity (MMN) response of novel tones in EEG, and delay of P3am response on the contralateral hemisphere to stimulated ear in MEG in opioid-dependent patients were observed. There were no differences in source locations or strengths of the dipoles for P1m, MMNm, and P3am determined using equivalent current dipoles. There were no group differences in EEG amplitude measures. In conclusion, our results suggest delayed pre-attentive auditory processing of novel information in opioid dependence. Benzodiazepine co-dependence modulated N1m response.

Psychosocial interventions for cocaine and psychostimulant amphetamines related disorders

BACKGROUND

The consumption of psychostimulants for non-medical reasons probably occurs because of their euphoriant and psychomotor-stimulating properties. Chronic consumption of these agents results in development of stereotyped behaviour, paranoia, and possibly aggressive behaviour. Psychosocial treatments for psychostimulant use disorder are supposed to improve compliance, and to promote abstinence. Evidence from randomised controlled trials in this subject needs to be summarised.

OBJECTIVES

To conduct a systematic review of all RCTs on psychosocial interventions for treating psychostimulant use disorder.

SEARCH STRATEGY

Electronic searches of Cochrane Library, EMBASE, MEDLINE, and LILACS (to may 2006); reference searching; personal communication; conference abstracts; unpublished trials from pharmaceutical industry; book chapters on treatment of psychostimulants abuse/ dependence.

SELECTION CRITERIA

All randomised-controlled trials focusing on psychosocial interventions for treating psychostimulants abuse/ dependence.

DATA COLLECTION AND ANALYSIS

Three authors extracted the data independently and Relative Risks, weighted mean difference and number needed to treat were estimated, when possible. The reviewers assumed that people who died or dropped out had no improvement (intention to treat analysis) and tested the sensitivity of the final results to this assumption.

MAIN RESULTS

Twenty-seven randomised controlled studies (3663 participants) fulfilled inclusion criteria and had data that could be used for at least one of the main comparisons. There was a wide heterogeneity in the interventions evaluated: this did not allow to provide a summary estimate of effect and results cannot be summarised in a clear cut way. The comparisons between different type of Behavioural Interventions showed results in favour of treatments with some form of Contingency management in respect to both reducing drop outs and lowering cocaine use..

AUTHORS' CONCLUSIONS

Overall this review reports little significant behavioural changes with reductions in rates of drug consumption following an intervention. Moreover, with the evidence currently available, there are no data supporting a single treatment approach that is able to comprise the multidimensional facets of addiction patterns and to significantly yield better outcomes to resolve the chronic, relapsing nature of addiction, with all its correlates and consequences.

Brain potentials implicate temporal lobe abnormalities in criminal psychopaths

Psychopathy is associated with abnormalities in attention and orienting. However, few studies have examined the neural systems underlying these processes. To address this issue, the authors recorded event-related potentials (ERPs) while 80 incarcerated men, classified as psychopathic or nonpsychopathic via the Hare Psychopathy Checklist--Revised (R. D. Hare, 1991, 2003), completed an auditory oddball task. Consistent with hypotheses, processing of targets elicited larger frontocentral negativities (N550) in psychopaths than in nonpsychopaths. Psychopaths also showed an enlarged N2 and reduced P3 during target detection. Similar ERP modulations have been reported in patients with amygdala and temporal lobe damage. The data are interpreted as supporting the hypothesis that psychopathy may be related to dysfunction of the paralimbic system--a system that includes parts of the temporal and frontal lobes.

Opioid plasma concentrations in methadone-and buprenorphine-maintained patients

This is the first trial to compare the relationship of opioid plasma concentrations in methadone-versus buprenorphine-maintained subjects. Sixty subjects (19 females and 41 males) seeking treatment who met Diagnostic and Statistical Manual version IV (DSM-IV) criteria for opioid dependence were recruited and treated at the Drug Addiction Outpatient Clinic at the University of Vienna. Of these, 44 (11 female and 33 male) were included in the analyses of plasma concentrations. Subjects received either daily sublingual buprenorphine (2 mg or 8 mg tablets; maximum daily dose: 8 mg) or oral methadone (racemic R-/S-methadone) and were maintained on a stable dose after an induction period of 2 weeks. Mean dose and mean plasma concentrations were correlated on an individual and collective basis. Correlation was 0.51 for buprenorphine, whereas the score for methadone was 0.69. Intra-individual variation was much higher for buprenorphine (p<0.0001), while the concentration-to-dose ratio was very small. Based on the differences of the pharmacokinetics of blood plasma of the two agents, we tried to explain the differences in the acceptance of treatment, which was significantly lower in the buprenorphine-maintained group. No such differences could be evaluated between completers and dropouts in buprenorphine-maintained subjects, neither concerning withdrawal scores nor dose, plasma concentration, concentration-to-dose ratios or intra-individual variation.

Alcoholism is a disinhibitory disorder: neurophysiological evidence from a Go/No-Go task

Response inhibition is considered a core dimension in alcoholism and its co-existing disorders. The major objective of this study is to compare the magnitude and spatial distribution of ERP components during response activation and inhibition in alcoholics (N = 30) and normal controls (N = 30) using a visual Go/No-Go task. The results indicate that alcoholics manifest a decreased P3(00) amplitude during Go as well as No-Go conditions. The difference between Go and No-Go processing was more evident in controls than in alcoholics. The topography of current source density in alcoholics during the P3 response was found to be very different from that of normals, suggesting that alcoholics perhaps activated inappropriate brain circuitry during cognitive processing. The significantly reduced No-Go P3 along with the relatively less anteriorized CSD topography during No-Go condition suggests poor inhibitory control in alcoholics. It is proposed that the No-Go P3, the electrophysiological signature of response inhibition, can be considered as an endophenotypic marker in alcoholism.

Long-term abstinence syndrome in heroin addicts: indices of P300 alterations associated with a short memory task

Attentional deficits have been implicated in the pathophysiology of opioid addicts. The P300 component of event-related potentials (ERPs) is considered as a manifestation of attentional operations. The authors' goal was the comparison of P300 elicited during a short memory test between subjects with prolonged heroin abstinence and current heroin users as well as healthy controls. The P300 component was evaluated during the anticipatory period of a short memory task in 20 patients characterized by a past history of opioid dependence (6 months abstinence), in 18 current heroin users and in 20 healthy comparison subjects, matched for age, sex and educational level. Abstinent heroin addicts exhibited significant reduction of P300 amplitude at central frontal region, relative to the other two groups. The findings are discussed in connection to the aim of identifying psychophysiological indices, addressing issues in opioid use disorders, and suggest that knowledge about cognitive operations, such as those reflected by P300 component, could provide further insight into psychophysiological mechanisms underlying the long-term abstinence state of heroin addicts.

Randomized trial of buprenorphine for treatment of concurrent opiate and cocaine dependence

BACKGROUND

Buprenorphine is a partial mu-opiate agonist and kappa-opiate antagonist with established efficacy in the treatment of opiate dependence. Its efficacy for cocaine dependence is uncertain. This study evaluated buprenorphine for the treatment of concomitant cocaine and opiate dependence.

METHODS

Two hundred outpatients currently dependent on both cocaine and opiates were randomly assigned to double-blind groups receiving a sublingual solution of buprenorphine (2, 8, or 16 mg daily, or 16 mg on alternate days, or placebo), plus weekly individual drug abuse counseling, for 13 weeks. The chief outcome measures were urine concentrations of opiate and cocaine metabolites (quantitative) and proportion of urine samples positive for opiates or cocaine (qualitative). Group differences were assessed by use of mixed regression modeling.

RESULTS

The target dose of buprenorphine was achieved in 179 subjects. Subjects receiving 8 or 16 mg buprenorphine daily showed statistically significant decreases in urine morphine levels (P =.0135 for 8 mg and P <.001 for 16 mg) or benzoylecgonine concentrations (P =.0277 for 8 mg and P =.006 for 16 mg) during the maintenance phase of the study. For the 16-mg group, mean benzoylecgonine concentrations fell from 3715 ng/mL during baseline to 186 ng/mL during the withdrawal phase; mean morphine concentrations fell from 3311 ng/mL during baseline to 263 ng/mL during withdrawal. For the 8-mg group, mean benzoylecgonine concentrations fell from 6761 ng/mL during baseline to 676 ng/mL during withdrawal; mean morphine concentrations fell from 3890 ng/mL during baseline to 661 ng/mL during withdrawal. Qualitative urinalysis showed a similar pattern of results. Subjects receiving the highest dose showed concomitant decreases in both urine morphine and benzoylecgonine concentrations. There were no significant group differences in treatment retention or adverse events.

CONCLUSIONS

A sublingual buprenorphine solution at 16 mg daily is well tolerated and effective in reducing concomitant opiate and cocaine use. The therapeutic effect on cocaine use appears independent of that on opiate use.

CNS recovery from cocaine, cocaine and alcohol, or opioid dependence: a P300 study

OBJECTIVES

The goal of the present study was to evaluate the relative effects of cocaine, cocaine and alcohol, or opioid dependence on P300 event-related potentials (ERPs). In addition, the effects of selected premorbid and comorbid factors were examined.

METHODS

P300 ERPs were recorded from 72 residential treatment program patients, characterized by a history of either cocaine (n=25), or cocaine and alcohol (n=18), or opioid (n=29) dependence, and 14 non-drug-dependent community volunteers. The 86 subjects completed a visual continuous performance test formed by a series of 150 presentations of individual consonant letters. They were asked to press a key whenever a letter was presented twice in succession.

RESULTS

Analyses of P300 ERPs obtained on target trials revealed a similar amplitude decrement in all the patient groups. Further analyses of P300 activity in the 3 drug-dependent patient groups revealed a negative correlation between P300 amplitude and the number of DSM-IIIR childhood conduct disorder criterion behaviors as well as a positive correlation between P300 amplitude and the duration of drug abstinence.

CONCLUSIONS

P300 amplitude in drug-dependent patients is influenced by a complex interaction between CNS pathology that predates, and probably promotes, the onset of drug dependence and CNS pathology that resolves during the process of recovery from drug dependence.

Abnormal P600 in heroin addicts with prolonged abstinence elicited during a working memory test

The P600 component of event-related potentials, believed to be generated by anterior cingulate gyrus and basal ganglia, is considered as an index of aspects of second-pass parsing processes of information processing, having much in common with working memory (WM) systems. Moreover, dysfunction of these brain structures as well as WM deficits have been implicated in the pathophysiology of opioid addicts. The present study is focused on P600 elicited during a WM test in twenty heroin addicts with prolonged abstinence compared with an equal number of healthy controls. The results showed significantly prolonged latencies at right hemisphere, specifically at Fp2 abduction. Moreover, memory performance of patients did not differ from that of normal controls. These findings may indicate that abstinent heroin addicts manifest abnormal aspects of second-pass parsing processes as are reflected by the P600 latencies, elicited during a WM test. Additionally, the P600 might serve as a valuable investigative tool for a more comprehensive understanding of the neurobiological substrate of drug abuse.

[Opioid addiction: P300 assessment in treatment by methadone substitution]

The aim of this study was to assess cognitive functions in two clinical conditions, namely during heroin detoxification and during substitution treatment by methadone. Two groups of chronic heroin user inpatients, meeting DSM-III-R criteria for concurrent opiate dependence, were tested using an auditory oddball paradigm of P300. The first group (four women and six men) were drug-free and the second (five women, ten men) received methadone treatment. Patients were also compared to a control group of non-dependent healthy subjects (five women, nine men). The patients were recorded 6-10 days after the beginning of either detoxification or methadone treatment. There were significant P300 alterations in the two patient groups, with amplitude decrease and latency increase, at a time when self-reported signs of withdrawal were absent or minimal. Paradoxically, the reaction time was accelerated in the two groups of patients, who also showed increased discrimination errors. These abnormalities were found with a lesser degree in the methadone-treated group than in detoxification patients.

Regional cerebral blood flow and comorbid diagnosis in abstinent opioid addicts

Studies using single photon emission computed tomography (SPECT) have found low cerebral blood flow (CBF) in frontal and parietal cortices in patients with chronic opiate dependence. In the present study, SPECT with 99mTc-HMPAO as tracer was used to compare 27 detoxified opiate addicts with nine healthy control subjects. All the subjects were evaluated with clinical psychiatric (DSM-IV), psychometric and neuropsychological measures. Compared with normal control subjects, the addicts showed a non-significant reduction of whole brain perfusion values. Significant hypoperfusion in the right frontal and left temporal lobes was found in addicts with comorbid depression, and a significant decrease in CBF in the right frontal lobe was observed in those with antisocial tendencies. A significant negative correlation emerged between Depression subscale scores on the Minnesota Multiphasic Personality Inventory and left temporal CBF in the patients. No significant correlations were found, however, between measures of cognition and CBF in opiate addicts. The asymmetrical findings in CBF that characterized the addicts relative to normal control subjects may be more closely related to mood and behavioral traits than to substance abuse, per se.

Endogenous opiates: 1996

This paper is the nineteenth installment of our annual review of research concerning the opiate system. It summarizes papers published during 1996 reporting the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress, tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.