Adrenergic blocker carvedilol attenuates the cardiovascular and aversive effects of nicotine in abstinent smokers

Pilot investigation of the effect of carvedilol on stress-precipitated smoking-lapse behavior

INTRODUCTION

Separate α1- and β-adrenergic antagonists have shown efficacy in reducing nicotine-motivated behaviors in rodents and humans, supporting a role for the noradrenergic system in mediating the reinforcing properties of drugs of abuse. However, the effect of the combined α1- and β-adrenergic antagonist, carvedilol, on stress-related smoking is unknown.

METHODS

Using a well-established human laboratory model of stress-precipitated smoking-lapse behavior, we examined whether carvedilol (0 or 50 mg/day; between subject, n=17 per group), administered to steady-state, would attenuate the ability to resist smoking following stress imagery (vs. neutral imagery) and reduce subsequent smoking self-administration in nicotine-deprived smokers ( n = 34 total). Tobacco craving, withdrawal, and physiologic reactivity were also assessed.

RESULTS

Latency to start smoking and number of cigarettes smoked during the self-administration period did not differ by medication condition. Counter to our hypothesis, tobacco craving demonstrated a medication × time effect, with greater craving in the carvedilol condition. Systolic blood pressure and heart rate demonstrated lower values in the carvedilol versus placebo group, consistent with known effects of carvedilol.

CONCLUSION

While carvedilol attenuated physiologic reactivity consistent with its clinical indication, beneficial effects on smoking outcomes were absent in this preliminary investigation and may suggest possible worsening. Future work may benefit from discerning the single versus combined effects of α1- and β-adrenergic antagonism on smoking outcomes.

Effect of doxazosin on stress reactivity and the ability to resist smoking

Preclinical findings support a role for α1-adrenergic antagonists in reducing nicotine-motivated behaviors, but these findings have yet to be translated to humans. The current study evaluated whether doxazosin would attenuate stress-precipitated smoking in the human laboratory. Using a well-validated laboratory analogue of smoking-lapse behavior, this pilot study evaluated whether doxazosin (4 and 8 mg/day) versus placebo attenuated the effect of stress (vs neutral imagery) on tobacco craving, the ability to resist smoking and subsequent ad-libitum smoking in nicotine-deprived smokers ( n=35). Cortisol, adrenocorticotropin, norepinephrine, epinephrine, and physiologic reactivity were assessed. Doxazosin (4 and 8 mg/day vs placebo) decreased cigarettes per day during the 21-day titration period. Following titration, doxazosin (4 and 8 mg/day vs placebo) decreased tobacco craving. During the laboratory session, doxazosin (8 mg/day vs placebo) further decreased tobacco craving following stress versus neutral imagery. Doxazosin increased the latency to start smoking following stress, and reduced the number of cigarettes smoked. Dosage of 8 mg/day doxazosin increased or normalized cortisol levels following stress imagery and decreased cortisol levels following neutral imagery. These preliminary findings support a role for the noradrenergic system in stress-precipitated smoking behavior, and support further development of doxazosin as a novel pharmacotherapeutic treatment strategy for smoking cessation.

New Pharmacological Agents to Aid Smoking Cessation and Tobacco Harm Reduction: What Has Been Investigated, and What Is in the Pipeline?

A wide range of support is available to help smokers to quit and to aid attempts at harm reduction, including three first-line smoking cessation medications: nicotine replacement therapy, varenicline and bupropion. Despite the efficacy of these, there is a continual need to diversify the range of medications so that the needs of tobacco users are met. This paper compares the first-line smoking cessation medications with (1) two variants of these existing products: new galenic formulations of varenicline and novel nicotine delivery devices; and (2) 24 alternative products: cytisine (novel outside Central and Eastern Europe), nortriptyline, other tricyclic antidepressants, electronic cigarettes, clonidine (an anxiolytic), other anxiolytics (e.g. buspirone), selective serotonin reuptake inhibitors, supplements (e.g. St John's wort), silver acetate, Nicobrevin, modafinil, venlafaxine, monoamine oxidase inhibitors (MAOIs), opioid antagonists, nicotinic acetylcholine receptor (nAChR) antagonists, glucose tablets, selective cannabinoid type 1 receptor antagonists, nicotine vaccines, drugs that affect gamma-aminobutyric acid (GABA) transmission, drugs that affect N-methyl-D-aspartate (NMDA) receptors, dopamine agonists (e.g. levodopa), pioglitazone (Actos; OMS405), noradrenaline reuptake inhibitors and the weight management drug lorcaserin. Six 'ESCUSE' criteria-relative efficacy, relative safety, relative cost, relative use (overall impact of effective medication use), relative scope (ability to serve new groups of patients) and relative ease of use-are used. Many of these products are in the early stages of clinical trials; however, cytisine looks most promising in having established efficacy and safety with low cost. Electronic cigarettes have become very popular, appear to be efficacious and are safer than smoking, but issues of continued dependence and possible harms need to be considered.

Targeting the Brain Stress Systems for the Treatment of Tobacco/Nicotine Dependence: Translating Preclinical and Clinical Findings

Tobacco use is the leading cause of preventable mortality in the United States, and Food and Drug Administration (FDA) approved medications fail to maintain long-term abstinence for the majority of smokers. One of the principal mechanisms associated with the initiation, maintenance of, and relapse to smoking is stress. Targeting the brain stress systems as a potential treatment strategy for tobacco dependence may be of therapeutic benefit. This review explores brain stress systems in tobacco use and dependence. The corticotropin-releasing factor (CRF) system, the hypothalamic-pituitary-adrenal (HPA) axis, and the noradrenergic system are discussed in relation to tobacco use. Preclinical and clinical investigations targeting these stress systems as treatment strategies for stress-induced tobacco use are also discussed. Overall, nicotine-induced activation of the CRF system, and subsequent activation of the HPA axis and noradrenergic system may be related to stress-induced nicotine-motivated behaviors. Pharmacological agents that decrease stress-induced hyperactivation of these brain stress systems may improve smoking-related outcomes.

Targeting the noradrenergic system for gender-sensitive medication development for tobacco dependence

INTRODUCTION

Tobacco use remains the leading cause of morbidity and mortality for both women and men in the United States, and women often experience poorer smoking cessation outcomes than men. Preliminary evidence suggests there are sex differences in medication effectiveness for smoking cessation. However, current medications do not take into account gender-sensitive treatment development and efficacy, underscoring the importance of this underdeveloped area of research.

METHODS

We reviewed preclinical and clinical evidence for gender differences in the inability to quit smoking by examining (a) the effect of increased negative affect and stress reactivity on smoking outcomes in women and (b) smoking for nicotine reinforcement in men. We also reviewed the current literature targeting the noradrenergic system as a novel gender-sensitive treatment strategy for tobacco dependence.

RESULTS

We hypothesize that noradrenergic agents that normalize noradrenergic activity may differentially attenuate stress reactivity in women and nicotine-related reinforcement in men, indicating that targeting the noradrenergic system for smoking cessation may be effective for both genders, with benefits operating through sex-specific mechanisms.

CONCLUSIONS

Converging lines of preclinical and clinical evidence suggest that gender-sensitive approaches to medication development for smoking cessation are a critical next step for addressing low quit rates and exacerbated health risks among women. Evidence reviewed indicates that smoking activates different brain systems modulated by noradrenergic activity in women versus men, and noradrenergic compounds may preferentially target these gender-sensitive systems.

Emerging drugs for the treatment of tobacco dependence: 2014 update

INTRODUCTION

Tobacco dependence remains a global epidemic and the largest preventable cause of morbidity and mortality around the world. Smoking cessation has benefits at all ages but remains challenging for several reasons, among which are the complexities of nicotine addiction and limitations of available pharmacotherapies.

AREAS COVERED

This review summarizes current and emerging pharmacotherapies for the treatment of tobacco dependence, including first- and second-line recommended agents. Medications with alternative primary indications that have been investigated as potential treatments for tobacco dependence are also discussed. Articles reviewed were obtained through searches of PubMed, Ovid MEDLINE, ClinicalTrials.gov and the Pharmaprojects database.

EXPERT OPINION

Current evidence suggests that the two most effective pharmacotherapies to treat tobacco dependence are varenicline and combination nicotine replacement therapy. Alternative agents investigated demonstrate mixed rates of success in achieving long-term abstinence from smoking. No single pharmacotherapy will serve as a universally successful treatment given the complex underpinnings of tobacco dependence and individuality of smokers. The ultimate goal of tobacco research with respect to pharmacotherapeutic development continues to be providing clinicians with an armamentarium of drugs to choose from allowing for tailoring of treatment for smokers.

Nicotine aversion: Neurobiological mechanisms and relevance to tobacco dependence vulnerability

Nicotine stimulates brain reward circuitries, most prominently the mesocorticolimbic dopamine system, and this action plays a critical in establishing and maintaining the tobacco smoking habit. Compounds that attenuate nicotine reward are considered promising therapeutic candidates for tobacco dependence, but many of these agents have other actions that limit their potential utility. Nicotine is also highly noxious, particularly at higher doses, and aversive reactions to nicotine after initial exposure can decrease the likelihood of developing a tobacco habit in many first time smokers. Nevertheless, relatively little is known about the mechanisms of nicotine aversion. The purpose of this review is to present recent new insights into the neurobiological mechanisms that regulate avoidance of nicotine. First, the role of the mesocorticolimbic system, so often associated with nicotine reward, in regulating nicotine aversion is highlighted. Second, genetic variation that modifies noxious responses to nicotine and thereby influences vulnerability to tobacco dependence, in particular variation in the CHRNA5-CHRNA3-CHRNB4 nicotinic acetylcholine receptor (nAChR) subunit gene cluster, will be discussed. Third, the role of the habenular complex in nicotine aversion, primarily medial habenular projections to the interpeduncular nucleus (IPN) but also lateral habenular projections to rostromedial tegmental nucleus (RMTg) and ventral tegmental area (VTA) are reviewed. Forth, brain circuits that are enriched in nAChRs, but whose role in nicotine avoidance has not yet been assessed, will be identified. Finally, the feasibility of developing novel therapeutic agents for tobacco dependence that act not by blocking nicotine reward but by enhancing nicotine avoidance will be considered. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

Cognitive effects of nicotine: genetic moderators

Cigarette smoking is the main preventable cause of death in developed countries, and the development of more effective treatments is necessary. Cumulating evidence suggests that cognitive enhancement may contribute to the addictive actions of nicotine. Several studies have demonstrated that nicotine enhances cognitive performance in both smokers and non-smokers. Genetic studies support the role of both dopamine (DA) and nicotinic acetylcholine receptors (nAChRs) associated with nicotine-induced cognitive enhancement. Based on knockout mice studies, beta2 nAChRs are thought to be essential in mediating the cognitive effects of nicotine. alpha7nAChRs are associated with attentional and sensory filtering response, especially in schizophrenic individuals. Genetic variation in D2 type DA receptors and the catechol-O-methyltransferase enzyme appears to moderate cognitive deficits induced by smoking abstinence. Serotonin transporter (5-HTT) gene variation also moderates nicotine-induced improvement in spatial working memory. Less is known about the contribution of genetic variation in DA transporter and D4 type DA receptor genetic variation on the cognitive effects of nicotine. Future research will provide a clearer understanding of the mechanism underlying the cognitive-enhancing actions of nicotine.

Modafinil and nicotine interactions in abstinent smokers

In this study, we examined the effects of a wakefulness-promoting medication, modafinil, alone and with the nicotine lozenge, on subjective, physiological and cognitive measures as well as on nicotine withdrawal in overnight abstinent cigarette smokers. Nineteen smokers, 13 male and 6 female, participated in a double-blind, placebo-controlled, crossover study. In each of three experimental sessions, subjects were treated orally with a single 200 mg or 400 mg dose of modafinil or placebo. Two hours and 10 min following the medication treatment, subjects received a single 2 mg nicotine lozenge. Both doses of modafinil alone increased the rating of elated-depressed on the Profile of Mood States (POMS) subscale in the direction of depressed and increased ratings of negative affect on the Positive and Negative Affect Schedule (PANAS). In contrast, the 200 mg modafinil dose combined with a 2 mg nicotine lozenge, increased the rating of energetic-tired in the direction of energetic on the POMS subscale. Modafinil attenuated self-reported rating of 'drug strength' in response to the nicotine lozenge. Modafinil, alone or in combination with the nicotine lozenge, did not affect tobacco withdrawal symptoms. There was an increase in baseline heart rate and systolic blood pressure under modafinil treatment. In addition, modafinil speeded reaction times on a modified Stroop task. The clinical utility of modafinil for smoking cessation needs to be determined in future studies.