Understanding drug addiction: implications for treatment

Cocaine conditioned behavior: a cocaine memory trace or an anti-habituation effect

Whether cocaine locomotor conditioning represents a cocaine positive effect; i.e., a Pavlovian cocaine conditioned response; or, a cocaine negative effect; i.e., interference with habituation to the test environment, is a subject of some controversy. Three separate experiments were conducted to compare the behavior (locomotion and grooming) of separate groups of rats given 1, 9 or 14 cocaine (10 mg/kg) treatments paired/unpaired with placement into an open-field arena. The behavior of the cocaine groups on subsequent saline tests were compared with the habituation rates of saline treated rats. After one cocaine pairing with the test environment, the subsequent behavior of the cocaine paired group on saline tests was similar to a non-habituated control group. In the two experiments with repeated cocaine pairings to the test environment, the subsequent behavior of the cocaine treated groups did not parallel that of the non-habituated saline control groups. These results were not explicable in terms of cocaine anti-habituation effects. It is suggested that cocaine contextual cues paired with cocaine treatment can activate cocaine memory traces which with subsequent cocaine treatments are reinforced and strengthened. In this way repeated cocaine use can forge conditioned stimulus connections to the cocaine behavioral response that are highly resistant to extinction.

CNS genes implicated in relapse

Drug abuse is a condition that impacts not only the individual drug user, but society as a whole. Although prevention of initial drug use is the most effective way to prevent addiction, avoiding relapse is a crucial component of drug addiction recovery. Recent studies suggest that there is a set of genes whose expression is robustly and stably altered following drug use and ensuing abstinence. Such stable changes in gene expression correlate with ultrastructural changes in brain as well as alterations in behavior. As persistent molecular changes, these genes may provide targets for the development of therapeutics. Developing a list of well-characterized candidate genes and examining the effect of manipulating these genes will contribute to the ultimate goal of developing effective treatments to prevent relapse to drug use.

Influence of Neuronal Nicotinic Receptors over Nicotine Addiction and Withdrawal

Cigarette smoking represents an enormous, global public health threat. Nearly five million premature deaths during a single year are attributable to smoking. Despite the resounding message of risks associated with smoking and numerous public health initiatives, cigarette smoking remains the most common preventable cause of disease in the United States. Fortunately, even in an adult smoker, smoking cessation can reverse many of the potential harmful effects. The symptoms associated with nicotine withdrawal represent the major obstacle to smoking cessation. This minireview examines the roles of various nicotinic receptors in the mechanisms of nicotine dependence, discusses the potential role of the habenula-interpeduncular nucleus axis in nicotine withdrawal, and highlights nicotinic receptors containing the β4 subunit as a potential pharmacological target for smoking cessation strategies.

Heroin self-administration: I. Incubation of goal-directed behavior in rats

This study used heroin self-administration to investigate incubation of goal-directed heroin-seeking behavior following abstinence. Male Sprague-Dawley rats self-administered heroin on a fixed ratio 10 (FR10) schedule of reinforcement with licking of an empty spout serving as the operant behavior during 14 daily 3 h sessions. After this acquisition period, all rats received a 90 min extinction session following either 1 day or 14 days of home cage abstinence. When the extinction session occurred after only 1 day of home cage abstinence, rats with a history of heroin self-administration divided their responses equally between the previously "active" and "inactive" spouts. However, when the extinction session occurred following 14 days of home cage abstinence, the rats exhibited marked goal-directed heroin-seeking behavior by licking more on the previously "active" than "inactive" spout. These findings demonstrate that heroin-seeking behavior incubates over time, resulting in goal-directed heroin-seeking behavior in rats following 14 days but not 1 day of abstinence. Moreover, this facilitatory effect occurred in response to a different training schedule, lower total drug intake, and shorter periods of daily access than previously reported with heroin.

Dopamine and corticotropin-releasing factor synergistically alter basolateral amygdala-to-medial prefrontal cortex synaptic transmission: functional switch after chronic cocaine administration

Basolateral amygdala (BLA) neurons provide a major excitatory input to medial prefrontal cortex (mPFC)-layer V pyramidal neurons. Under stressful conditions, commonly associated with chronic cocaine abuse, altered BLA-to-mPFC synaptic transmission could lead to defective emotional information processing and decision making within the mPFC and result in misguided and inappropriate behaviors. We examined the effects of cocaine administered chronically in vivo on EPSCs recorded from a putative BLA-mPFC pathway in vitro and their modulation by dopamine (DA), corticotropin-releasing factor (CRF), and their combination (DA plus CRF). In saline-treated animals, activation of D(1/5) receptors depressed BLA-mPFC EPSCs, whereas CRF1 receptor activation alone had no effect on EPSCs. Activating D(1/5) and CRF1 receptors in combination, however, worked synergistically through presynaptic and postsynaptic mechanisms to depress EPSCs to levels greater than D(1/5) receptor activation alone. After chronic cocaine administration, the function of DA(1/5) and CRF receptors switched from inhibitory to excitatory. In slices from cocaine-treated animals, putative BLA-mPFC EPSCs were depressed through a presynaptic mechanism. Now, activation of either D(1/5) or CRF2 receptors increased the cocaine-induced, depressed EPSCs. Additionally, simultaneous activation of presynaptic D(1/5) and CRF2 receptors led to further enhancement of EPSCs. These data indicate that CRF acting synergistically with DA normally potentiates D(1/5)-induced synaptic depression. However, after chronic cocaine, the combined synergistic actions of DA and CRF switched polarity to enhance facilitation of BLA-mPFC glutamatergic transmission. Also unmasked after acute withdrawal from chronic cocaine are endogenous, tonic-inhibitory D2-like and tonic-facilitatory CRF2 receptor actions. These multiple functional and receptor changes may underlie the altered, possibly aberrant, decision-making process after chronic cocaine.

Examining the clinical efficacy of bupropion and nortriptyline as smoking cessation agents in a rodent model of nicotine withdrawal

RATIONALE

At present, there is a lack of an established animal model to demonstrate the clinical efficacy of smoking cessation agents in the laboratory. The aim of this study was to compare the effects of the antidepressants bupropion and nortriptyline, clinically proven smoking cessation aids, within a rodent model of a nicotine withdrawal based on somatic measures.

MATERIALS AND METHODS

Male hooded Lister rats were chronically exposed to nicotine (3.16 mg kg1 day1) for 7 days via SC implanted ALZET osmotic minipumps. Animals were acutely pre-treated with bupropion (10, 30 or 60 mg/kg, IP) or nortriptyline (1.5, 4.7 and 15 mg/kg, IP), and nicotine withdrawal was precipitated by mecamylamine (1 mg/kg).

RESULTS

Precipitation of nicotine withdrawal led to an increase in somatic signs including body shakes, chews, eye blinks, foot licks, head shakes and ptosis. Bupropion dose-dependently decreased the total abstinence scores and reduced the occurrence of some individual somatic signs. Pre-treatment with 60 mg/kg bupropion did not result in a significant increase in total abstinence scores or individual somatic signs scores after mecamylamine challenge, compared to the mecamylamine control group, suggesting nicotine withdrawal is fully attenuated at this dose. Similarly, the highest dose of nortriptyline reduced total abstinence scores and some individual somatic signs to the level of the mecamylamine control group. However, nortriptyline was only effective at alleviating somatic measures of withdrawal at doses which also suppressed locomotor activity.

CONCLUSION

In concurrence with clinical findings proposing alleviation of withdrawal states as a possible mechanism of bupropion and nortriptyline's smoking cessation action, both drugs were found to ameliorate somatic signs of nicotine withdrawal in rodents.

Bupropion may support psychosocial treatment of nicotine-dependent adolescents: preliminary results

STUDY OBJECTIVE

To assess the efficacy and safety of long-term bupropion therapy for nicotine dependence in adolescents.

DESIGN

Prospective, double-blind, placebo-controlled trial.

SETTING

Outpatient clinic in Innsbruck, Austria.

SUBJECTS

Twenty-two adolescents, aged 16-19 years, with nicotine dependence.

INTERVENTION

Participants were randomly assigned to receive bupropion 150 mg/day or placebo for 90 days.

MEASUREMENTS AND MAIN RESULTS

Patients were classified as abstinent or relapsed on day 0 (when study drug was started) and again on days 30 and 90, according to their self-reports. Treatment failure was defined as relapse or nonattendance. Time to first treatment failure was the primary outcome measure. Mean cumulative abstinence duration was significantly greater in the bupropion group than in the placebo group (78.4 +/- 39.6 vs 30.2 +/- 19.2 days. p=0.0042).

CONCLUSION

Bupropion seems to be an effective and well-tolerated pharmacologic adjunct to psychosocial and behavioral treatment programs for some adolescent nicotine-dependent patients. However, experienced clinicians should continuously monitor patients for adverse effects.

Challenges facing health professionals caring for HIV-infected drug users

Although injection drug use accounts for only 5% to 10% of cumulative HIV infections globally, it is a more efficient way of spreading HIV than sexual intercourse. HIV epidemics among injection drug users (IDUs) have a potential for rapid spread of the virus within the IDU community and outward into the general population. Effective interventions addressing this mode of HIV transmission are needed because part of a comprehensive strategy to curb the spread of HIV infection. IDUs, often marginalized, pose serious health challenges that can no longer be overlooked. Health care providers need to familiarize themselves with these challenges in order to meet the needs of this disenfranchised population. Providers need to have a clear understanding of targeted behavior and their patients' environmental context. Efforts must be made to foster healthy behavior among IDUs to assist them in managing their infection effectively and become productive members of society. This paper reviews these challenges and outlines selected models that may assist health care providers in fostering behavior changes among HIV-positive injection drug users.

Review of bupropion for smoking cessation

The advent of bupropion hydrochloride sustained release (Zyban) has heralded a major change in the options available for smoking cessation pharmacotherapy. Bupropion is a selective re-uptake inhibitor of dopamine and noradrenalin which prevents or reduces cravings and other features of nicotine withdrawal. Bupropion is a useful oral and non-nicotine form of pharmacotherapy for smoking cessation. For this review a total of 221 papers were reviewed plus poster presentations. This review examines in detail original clinical trials on efficacy, categorised according to whether they were acute treatment trials in healthy smokers; studies in specific populations such as people with depression, chronic obstructive pulmonary disease (COPD) or cardiovascular disease; or relapse prevention studies. Overall, these studies in varying populations comprising over four thousand subjects, showed bupropion consistently produces a positive effect on smoking cessation outcomes. The evidence highlights the major public health role that bupropion has in smoking cessation. The methodological issues of published clinical trials reporting one year outcomes were examined in detail including: completeness of follow-up; loss to follow-up; intention to treat analysis; blindness of assessment; and validation of smoking status. The review discusses contraindications, adverse effects, dose and overdose, addictive potential, and the role of bupropion in reducing cessation-related weight gain. Bupropion combined with or compared to other pharmacotherapies (nicotine patch; nortriptyline) is considered. Impressive evidence exists for the use of bupropion in smoking cessation among difficult patients who are hard-core smokers such as those with cardiovascular disease, chronic obstructive pulmonary disease (COPD) and depression. Bupropion reduces withdrawal symptoms as well as weight gain and is effective for smoking cessation for people with and without a history of depression or alcoholism. Serious side effects of bupropion use are rare. The major safety issue with bupropion is risk of seizures (estimated at approximately 0.1%) and it should not be prescribed to patients with a current seizure disorder or any history of seizures. In clinical trials of bupropion for smoking cessation no seizures were reported. Allergic reactions occur at a rate of approximately 3% and minor adverse effects are common including dry mouth and insomnia.

Evaluación económica del empleo de terapias farmacológicas para la cesación en el hábito tabáquico

INTRODUCTION

Public policies for smoking cessation are mainly based on advice from the primary care physician and group therapy. Several pharmacological treatments to reduce tobacco addiction are currently available. One of these treatments, bupropion, has remarkable efficacy (30% over 1 year) compared with nicotine replacement therapies (chewing gum 8%, patches 17% over 1 year). The objective of this study was to assess the efficiency of three smoking cessation strategies based on pharmacotherapies in Spain.

MATERIAL AND METHODS

The current situation of methods for smoking cessation in Spain includes a mixture of primary care physician advice, group therapy and willpower, combined with the use of drugs in a small proportion of individuals. This situation was compared with three scenarios in which the use of the available pharmacotherapies was increased (by up to 10%) for 1 year. A cost-effectiveness evaluation was used to calculate the cost per death prevented and per year of life saved in each scenario. The analysis used a time horizon of 20 years and was based on an adaptation of the HECOS model, sponsored by WHO-Euro, which enables comparison of distinct pharmacotherapy interventions. Epidemiological data were based on the National Health Survey (1997) and the National Institute of Statistics (1999).

RESULTS

The cost-effectiveness ratio of bupropion at 5 years was 70,939 euros per death prevented and was 37,305 euros per year of life saved. When the time horizon was increased to 20 years, these figures became net savings of 28,166 and 3,265 euros, respectively. The cost-effectiveness ratios for both nicotine gums and patches were higher than that for bupropion: 171,834 euros per death prevented at 5 years and 90,362 euros per year of life saved for patches and 513,004 euros per death prevented and 269,772 euros per year of life saved at 5 years. Furthermore, bupropion treatment for 1 year would prevent a greater number of deaths than the alternative strategies (approximately 3,000 deaths in a time horizon of 20 years) due to the decrease in the number of smokers.

CONCLUSIONS

The cost of some tobacco cessation methods, such as primary care physician advice and group therapy, is low but their efficacy is also low. New drug treatments increase costs and also achieve higher efficacy rates. When assessing interventions and their costs economic evaluation shows that in the long run greater use of bupropion generates net savings in tobacco-related health costs.

Treating nicotine dependence during pregnancy and postpartum: understanding clinician knowledge and performance

This study investigated the relationship of clinicians' knowledge of treatments for nicotine dependence during pregnancy and postpartum and explored what provider characteristics are associated with knowledge levels. Survey data from community health center (CHC)-based prenatal, pediatric (PED), and WIC program (Special Supplemental Nutrition Program for Women, Infants, and Children) providers participating in a randomized clinical study were used. Providers reported low awareness of the health risks of smoking to the developing fetus/child of pregnant and postpartum women and of the effectiveness of nicotine replacement therapy (NRT) for doubling quit rates. Obstetric (OB) and WIC providers were more aware than PED providers that provider-delivered interventions are effective. Confidence in using counseling steps was significantly associated with general and NRT-related knowledge. NRT-related knowledge, but not general knowledge, was associated with higher performance of intervention steps. Educational programs targeting OB, WIC, and PED providers' knowledge about effective smoking cessation counseling strategies and their confidence in being effective with patients are needed.

Promoting smoking cessation in adults

There is a wealth of opportunities for nurses to facilitate smoking cessation with their patients. Nurses have shown to have a modest but positive effect on cessation rates when they deliver brief or intensive counseling. Because nurses work in a multitude of clinical settings, they can impact both prevention and treatment of nicotine addiction associated with cigarette use. More nurses need to be educated about their role in reducing the morbidity and mortality of tobacco-related diseases.

Consenso sobre o tratamento da dependência de nicotina

Têm sido atribuídas à dependência de nicotina 20% das mortes nos EUA. Estudos têm mostrado que 30% a 50% das pessoas que começam a fumar escalam para um uso problemático. Nos últimos 20 anos, a educação e a persuasão não foram suficientes para promover uma mudança política, cultural e social relacionada ao comportamento de fumar. As intervenções para interromper o uso de tabaco ainda não estão integradas às rotinas dos serviços de saúde no mundo. A falta de estratégias de integração, de tempo disponível para acoplar ações assistenciais mais específicas e mesmo a percepção dos profissionais de saúde de que os tratamentos para a dependência de nicotina são pouco efetivos são algumas das barreiras apontadas. Assim, elaborar um consenso sobre a dependência de nicotina teve como objetivos: • levantar dados epidemiológicos relevantes relacionados ao uso do tabaco no mundo e no Brasil; • revisar as ações gerais e centrais da nicotina; • elaborar um protocolo de triagem mínimo para serviços de atenção primária à saúde; • recomendar diretrizes básicas de avaliação, diagnóstico e tratamento para todos os níveis de atenção à saúde em relação à dependência de nicotina; • fornecer sugestões para a abordagem de grupos especiais de pacientes: adolescentes, gestantes, idosos, pacientes em regime de internação, obesos e pacientes com comorbidades psiquiátricas, cardiovasculares e respiratórias.

Anxious adults vs. cool children: children's views on smoking and addiction

Tobacco addiction represents a major public health problem, and most addicted smokers take up the habit during adolescence. We need to know why. With the aim of gaining a better understanding of the meanings smoking and tobacco addiction hold for young people, 85 focused interviews were conducted with adolescent children from economically deprived areas of Northern Ireland. Through adopting a qualitative approach within the community rather than the school context, the adolescent children were given the opportunity to freely express their views in confidence. Children seem to differentiate conceptually between child smoking and adult smoking. Whereas adults smoke to cope with life and are thus perceived by children as lacking control over their consumption, child smoking is motivated by attempts to achieve the status of cool and hard, and to gain group membership. Adults have personal reasons for smoking, while child smoking is profoundly social. Adults are perceived as dependent on nicotine, and addiction is at the core of the children's understanding of adult smoking. Child smoking, on the other hand, is seen as oriented around social relations so that addiction is less relevant. These ideas leave young people vulnerable to nicotine addiction. It is clearly important that health promotion efforts seek to understand and take into account the actions of children within the context of their own world-view to secure their health.

Nicotine as an Addictive Substance: A Critical Examination of the Basic Concepts and Empirical Evidence

The present review is a critical analysis of the concepts behind and the empirical data supporting the view that tobacco use represents an addiction to nicotine. It deals with general aspects of the notion of addiction, while concentrating on specific problems associated with incorporating nicotine into current frameworks. The notion of addiction suffers from unprecedented definitional difficulties. The definitions offered by various authorities are very different, even contradictory. Definitions that reasonably include nicotine are so broad and vague that they allow many trivial things, such as salt, sugar, and watching television, to be considered addictive. Definitions that exclude the trivia also exclude nicotine. The addiction hypothesis, in general, is strongly shaped by views that certain drugs bring about a molecular level subversion of rationality. The main human evidence for this is verbal reports of smokers who say that they can't quit. On the other hand, the existence of many millions of successful quitters suggests that most people can quit. Some smokers don't quit, but whether they can't is another matter. The addiction hypothesis would be greatly strengthened by the demonstration that any drug of abuse produces special changes in the brain. It has yet to be shown that any drug produces changes in the brain different from those produced by many innocuous substances and events. The effects of nicotine on the brain are similar to those of sugar, salt, exercise, and other harmless substances and events. Apart from numerous conceptual and definitional inadequacies with the addiction concept in general, the notion that nicotine is addictive lacks reasonable empirical support. Nicotine does not have the properties of reference drugs of abuse. There are so many findings that conflict so starkly with the view that nicotine is addictive that it increasingly appears that adhering to the nicotine addiction thesis is only defensible on extra-scientific grounds.

An open trial of bupropion for ADHD in adolescents with substance use disorders and conduct disorder

OBJECTIVE

Adolescents with conduct disorder (CD) and substance use disorders (SUD) have higher rates of comorbid attention-deficit/hyperactivity disorder (ADHD) than those without CD and SUD. Comorbid ADHD may contribute to more severe SUD. Treatment of ADHD may enhance effective treatment of substance abuse and behavior problems, yet there are few data regarding pharmacological treatment of ADHD in such youths.

METHOD

Pilot data are presented from a 5-week, open-label bupropian trial in 13 nondepressed adolescent boys in a residential treatment program focusing on substance and behavioral treatments. All had diagnoses of ADHD, CD, and SUD. Patients' doses were titrated to a maximum fixed daily dose of 300 mg of bupropion. The Conners Hyperactivity Index and Daydream Attention scores, along with Clinical Global Impressions Severity of Illness (CGI-S) ratings, were obtained at baseline and at the fifth week of treatment.

RESULTS

Subjects' mean Conners Hyperactivity Index score declined from 75.5 to 65.4 (p < .01, Wilcoxon signed rank test) (13% decline). The mean Daydream Attention score declined from 59.5 to 53.6 (p < .02, Wilcoxon signed rank test) (10% decline). Mean CGI-S declined from 4.9 to 3.0 (p < .002, Wilcoxon signed rank test) (39% decline).

CONCLUSIONS

These preliminary data suggest that bupropion may be a useful treatment for ADHD in adolescents with CD and SUD; they suggest the need for a controlled trial of bupropion in such youths.