Efficacy of buspirone in smoking cessation: a placebo-controlled trial

Current Perspectives on Selective Dopamine D3 Receptor Antagonists/Partial Agonists as Pharmacotherapeutics for Opioid and Psychostimulant Use Disorders

Over three decades of evidence indicate that dopamine (DA) D3 receptors (D3R) are involved in the control of drug-seeking behavior and may play an important role in the pathophysiology of substance use disorders (SUD). The expectation that a selective D3R antagonist/partial agonist would be efficacious for the treatment of SUD is based on the following key observations. First, D3R are distributed in strategic areas belonging to the mesolimbic DA system such as the ventral striatum, midbrain, and ventral pallidum, which have been associated with behaviors controlled by the presentation of drug-associated cues. Second, repeated exposure to drugs of abuse produces neuroadaptations in the D3R system. Third, the synthesis and characterization of highly potent and selective D3R antagonists/partial agonists have further strengthened the role of the D3R in SUD. Based on extensive preclinical and preliminary clinical evidence, the D3R shows promise as a target for the development of pharmacotherapies for SUD as reflected by their potential to (1) regulate the motivation to self-administer drugs and (2) disrupt the responsiveness to drug-associated stimuli that play a key role in reinstatement of drug-seeking behavior triggered by re-exposure to the drug itself, drug-associated environmental cues, or stress. The availability of PET ligands to assess clinically relevant receptor occupancy by selective D3R antagonists/partial agonists, the definition of reliable dosing, and the prospect of using human laboratory models may further guide the design of clinical proof of concept studies. Pivotal clinical trials for more rapid progression of this target toward regulatory approval are urgently required. Finally, the discovery that highly selective D3R antagonists, such as R-VK4-116 and R-VK4-40, do not adversely affect peripheral biometrics or cardiovascular effects alone or in the presence of oxycodone or cocaine suggests that this class of drugs has great potential in safely treating psychostimulant and/or opioid use disorders.

Dopamine D3 receptor-based medication development for the treatment of opioid use disorder: Rationale, progress, and challenges

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Opioid abuse and overdose have become a national crisis in the USA.

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Although several opioid-based pharmacotherapies are available, they are ineffective in long-term relapse prevention.

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National Institute on Drug Abuse has listed dopamine D3 receptor antagonists as high priority for anti-opioid medication development.

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The novel D3 receptor antagonists (VK4-116, VK4-40) are effective in reducing opioid reward and relapse as well as potentiate opioid analgesia.

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D3 receptor antagonists deserve further studies as new pharmacotherapies for pain and of opioid use disorder.

Opioid abuse and related overdose deaths continue to rise in the United States, contributing to the current national opioid crisis. Although several opioid-based pharmacotherapies are available (e.g., methadone, buprenorphine, naloxone), they show limited effectiveness in long-term relapse prevention. In response to the opioid crisis, the National Institute on Drug Abuse proposed a list of pharmacological targets of highest priority for medication development for the treatment of opioid use disorders (OUD). Among these are antagonists of dopamine D3 receptors (D3R). In this review, we first review recent progress in research of the dopamine hypothesis of opioid reward and abuse and then describe the rationale and recent development of D3R ligands for the treatment of OUD. Herein, an emphasis is placed on the effectiveness of newly developed D3R antagonists in the animal models of OUD. These new drug candidates may also potentiate the analgesic effects of clinically used opioids, making them attractive as adjunctive medications for pain management and treatment of OUD.

Current and Emerging Pharmacotherapies for Cessation of Tobacco Smoking

Tobacco use disorder is a chronic illness. With its high comorbidity rate, it is a major cause of years of life lost or years lived with disability; however, it is also considered the most preventable cause of death in developed countries. Since the development of nicotine replacement therapy (NRT) in 1978, treatment options have continued to evolve and expand. Despite this, currently available treatments remain insufficient, with less than 25% of smokers remaining abstinent 1 year after treatment. In this article, we review existing and emerging smoking cessation pharmacotherapies, with a special emphasis on the most promising agents that are currently being investigated. A search of the Cochrane Database of Systematic Reviews and the PubMed, Ovid, and ClinicalTrials.gov databases (August 2 to September 1, 2017) was undertaken for articles on smoking cessation pharmacotherapies, applying no language restrictions. More than 40 pharmacotherapies were reviewed including conventional pharmacotherapies-NRT, bupropion, and varenicline (all approved by the U.S. Food and Drug Administration as first-line treatment of smoking cessation)-and novel therapies: cytisine, N-acetylcysteine, cycloserine, memantine, baclofen, topiramate, galantamine, and bromocriptine. Studies of combination NRT and varenicline showed the greatest smoking cessation rates. Clonidine and nortriptyline are second-line treatments used when first-line treatments fail or are contraindicated, or by patient preference. Some novel therapies, especially acetylcholinesterase inhibitors, cytisine, and N-acetylcysteine, display promising results. Because the results of randomized clinical trials were reported using varied end points and outcome measures, direct comparisons between different pharmacotherapies cannot easily be evaluated. Additional high-quality randomized double-blind placebo-controlled trials with long-term follow-up, using validated sustained abstinence measures, are needed to find more effective smoking cessation aids.

Dopamine D3 receptors as a therapeutic target for methamphetamine dependence

BACKGROUND

Methamphetamine (MA) use disorders are major public health problems nationally and worldwide and treatment remains an unmet need.

OBJECTIVES

(1) To review preclinical and clinical studies identifying the dopamine D3 receptor as a therapeutic target for substance use disorders (SUDs), including MA dependence, (2) to consider buspirone (Buspar®) as a potential medication based on its dopamine D3 receptor antagonist properties, and (3) to evaluate the safety and initial efficacy of buspirone in a pilot study of MA-dependent individuals.

METHODS

Literature on the dopamine D3 receptor as a therapeutic target and on the potential of buspirone as a novel therapy for MA dependence was reviewed. The cardiovascular and subjective effects of intravenous MA challenge were assessed in five non-treatment seeking individuals. Participants met DSM-IV criteria for MA dependence and were treated subacutely (9 days) with buspirone (60 mg daily).

RESULTS

The literature identified the dopamine D3 receptor as a therapeutic target for MA dependence, a safe and approved medication, and a valuable opportunity to re-purpose buspirone for treating MA dependence and perhaps other SUDs. Pilot data (n = 5) indicated that buspirone is safe in MA-using individuals and comparison against historical placebo data from this laboratory suggested that at least some aspects of the subjective properties of MA may be diminished during buspirone treatment.

CONCLUSION

Future studies should include a small-scale, placebo-controlled Phase IIa trial of buspirone in MA dependence.

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.

Effects of chronic buspirone treatment on nicotine and concurrent nicotine+cocaine self-administration

Nicotine dependence and cocaine abuse are major public health problems, and most cocaine abusers also smoke cigarettes. An ideal pharmacotherapy would reduce both cigarette smoking and cocaine abuse. Buspirone (Buspar) is a clinically available, non-benzodiazepine anxiolytic medication that acts on serotonin and dopamine systems. In preclinical studies, it reduced cocaine self-administration following both acute and chronic treatment in rhesus monkeys. The present study evaluated the effectiveness of chronic buspirone treatment on self-administration of intravenous (IV) nicotine and IV nicotine+cocaine combinations. Five cocaine-experienced adult rhesus monkeys (Macaca mulatta) were trained to self-administer nicotine or nicotine+cocaine combinations, and food pellets (1 g) during four 1-h daily sessions under a second-order schedule of reinforcement (FR 2 (VR16:S)). Each nicotine+cocaine combination maintained significantly higher levels of drug self-administration than nicotine or cocaine alone (P<0.05-0.001). Buspirone (0.032-0.56 mg/kg/h) was administered IV through one lumen of a double-lumen catheter every 20 min for 23 h each day, for 7-10 consecutive days. Each 7-10-day sequence of buspirone treatment was followed by saline-control treatment for at least 3 days until food- and drug-maintained responding returned to baseline. Buspirone dose-dependently reduced responding maintained by nicotine alone (0.001-0.1 mg/kg/inj; P<0.01) and by nicotine (0.001 or 0.0032 mg/kg/inj)+cocaine combinations (0.0032 mg/kg/inj; P<0.05-0.001) with no significant effects on food-maintained responding. We conclude that buspirone selectively attenuates the reinforcing effects of nicotine alone and nicotine+cocaine polydrug combinations in a nonhuman primate model of drug self-administration.

Modification of cocaine self-administration by buspirone (buspar®): potential involvement of D3 and D4 dopamine receptors

Converging lines of evidence indicate that elevations in synaptic dopamine levels play a pivotal role in the reinforcing effects of cocaine, which are associated with its abuse liability. This evidence has led to the exploration of dopamine receptor blockers as pharmacotherapy for cocaine addiction. While neither D1 nor D2 receptor antagonists have proven effective, medications acting at two other potential targets, D3 and D4 receptors, have yet to be explored for this indication in the clinic. Buspirone, a 5-HT1A partial agonist approved for the treatment of anxiety, has been reported to also bind with high affinity to D3 and D4 receptors. In view of this biochemical profile, the present research was conducted to examine both the functional effects of buspirone on these receptors and, in non-human primates, its ability to modify the reinforcing effects of i.v. cocaine in a behaviourally selective manner. Radioligand binding studies confirmed that buspirone binds with high affinity to recombinant human D3 and D4 receptors (∼98 and ∼29 nm respectively). Live cell functional assays also revealed that buspirone, and its metabolites, function as antagonists at both D3 and D4 receptors. In behavioural studies, doses of buspirone that had inconsistent effects on food-maintained responding (0.1 or 0.3 mg/kg i.m.) produced a marked downward shift in the dose-effect function for cocaine-maintained behaviour, reflecting substantial decreases in self-administration of one or more unit doses of i.v. cocaine in each subject. These results support the further evaluation of buspirone as a candidate medication for the management of cocaine addiction.

Targeting nicotine addiction: the possibility of a therapeutic vaccine

Cigarette smoking is the primary cause of lung cancer, cardiovascular diseases, reproductive disorders, and delayed wound healing all over the world. The goals of smoking cessation are both to reduce health risks and to improve quality of life. The development of novel and more effective medications for smoking cessation is crucial in the treatment of nicotine dependence. Currently, first-line smoking cessation therapies include nicotine replacement products and bupropion. The partial nicotinic receptor agonist, varenicline, has recently been approved by the US Food and Drug Administration (FDA) for smoking cessation. Clonidine and nortriptyline have demonstrated some efficacy, but side effects may limit their use to second-line treatment products. Other therapeutic drugs that are under development include rimonabant, mecamylamine, monoamine oxidase inhibitors, and dopamine D3 receptor antagonists. Nicotine vaccines are among newer products seeking approval from the FDA. Antidrug vaccines are irreversible, provide protection over years and need booster injections far beyond the critical phase of acute withdrawal symptoms. Interacting with the drug in the blood rather than with a receptor in the brain, the vaccines are free of side effects due to central interaction. For drugs like nicotine, which interacts with different types of receptors in many organs, this is a further advantage. Three anti-nicotine vaccines are today in an advanced stage of clinical evaluation. Results show that the efficiency of the vaccines is directly related to the antibody levels, a fact which will help to optimize the vaccine effect. The vaccines are expected to appear on the market between 2011 and 2012.

Effect of sustained-release (SR) bupropion on craving and withdrawal in smokers deprived of cigarettes for 72 h

RATIONALE

Sustained-release (SR) bupropion enhances quit rates of smokers, generally decreases tobacco withdrawal, and in some studies, reduces craving.

OBJECTIVE

Investigate the effects of SR bupropion on craving and withdrawal during cigarette abstinence.

METHODS

Twenty three smokers participated in three 17-day periods composed of 14 out-patient days followed by 3 (72 h) in-patient days. During the out-patient days, subjects received SR bupropion, placebo, or no drug. During the in-patient days, subjects were abstinent from cigarettes on two occasions while receiving either SR bupropion or placebo and smoked freely during the other occasion. SR bupropion was titrated over the first three out-patient days followed by a fixed dose (300 mg/day) for 14 days (including the three in-patient abstinence days). Cigarette craving, withdrawal, and selected physiological measures were assessed repeatedly over the 72-h periods.

RESULTS

During the 72-h periods, craving intensity was significantly lower with free smoke and SR bupropion than with placebo, and significantly lower during free smoke than during SR bupropion. Overall withdrawal symptoms were significantly lower with free smoke than with either placebo or SR bupropion. Among individual withdrawal symptoms (excluding craving), appetite increase was significantly reduced during SR bupropion compared to placebo. During placebo and SR bupropion, craving intensity displayed a circadian pattern that was different from that observed during free smoke.

CONCLUSIONS

SR bupropion reduced craving and appetite increase during smoking abstinence. These findings support the hypothesis that craving and withdrawal symptoms may be controlled by distinct central nervous system pathways.

Novel pharmacotherapeutic targets for the management of drug addiction

Despite individual variation in the liability to the abuse of psychoactive substances, there is substantial commonality shared by drugs of abuse. The knowledge of these common mechanisms together with the continued elucidation of the neurobiological underpinnings of withdrawal symptoms, drug intake, craving, relapse, and co-morbid psychiatric associations are critically important for the development of new therapeutic strategies. The present review will focus on recent advances in the development of innovative pharmacotherapeutic agents, which should promote higher efficacy (abstinence, prevention of relapse, long-term recovery) and patient compliance, as well as improved safety profiles.

Current pharmacological treatments for nicotine dependence

There are nearly 1.1 billion users of nicotine and tobacco products worldwide. Tobacco use through cigarette smoking is the leading preventable cause of death in the world and kills nearly four million people annually. However, although some cigarette smokers are able to quit, many are not, and standard medications to assist in smoking cessation (e.g. nicotine-replacement therapies and sustained-release bupropion) are ineffective in many remaining smokers. Recent developments in our understanding of the neurobiology of nicotine dependence have identified several neurotransmitter systems that might contribute to the process of smoking maintenance and relapse, including dopamine, noradrenaline, 5-hydroxytryptamine, acetylcholine, endogenous opioids, GABA, glutamate and endocannabinoids. Several existing medications are being tested as treatments for nicotine dependence and novel investigational agents are under development as effective treatments for nicotine dependence in the 'hard to treat' tobacco user.

Applying genetic approaches to the treatment of nicotine dependence

To advance the science of tobacco control, an enhanced understanding of the bio-behavioral basis of nicotine addiction is needed. In this study, we provide an overview of data from investigations of genetic factors in smoking behavior, discuss potential bio-behavioral mechanisms and effect modifiers, and suggest avenues for pharmacogenetics research in the area of smoking cessation treatment. The evidence to date is very consistent with respect to the significance of genetic contributions to smoking behavior. However, attempts to elucidate the role of specific genetic variants have met with mixed success. Explanations for the lack of consistency in the results of genetic association studies include biases in ascertainment, ethnic admixture, lack of attention to co-variates or modifiers of genetic risk, and the need for more refined phenotypes. As the field of genetics and smoking research progresses, increasing attention is being devoted to gene-environment interactions, with particular attention to the identification of genetic variants that may modify the effects of pharmacological treatment for smoking. With advances in molecular biology and genomics technology, individualized tailoring of smoking cessation therapy to genotype is within our grasp. Such research has the potential to improve treatment outcome, thereby reducing morbidity and mortality from smoking-related disease.

[Smoking cessation and bupropion: anxiety and depression as predictors of therapeutic efficacy]

Smoking and depression are related. Bupropion, the first non-nicotinic drug that is an effective treatment in smoking cessation, is a tricyclic antidepressant that inhibits neuronal uptake of serotonin, dopamine and norepinephrine in the thalamic nuclei.

OBJECTIVE

To assess if certain personality factors (anxiety or depression) might predict the efficacy of bupropion for smoking cessation.

METHOD

The study was carried out in two smoking cessation clinics in Madrid and Barcelona. Fifty patients (21 men) declaring the desire to quit smoking were enrolled. Their mean age was 43.6 years (SD 8.75). The patients were treated with 300 mg of bupropion per day for one month and expired CO was monitored for 6 months. Personality factors were assessed on a hospital anxiety and depression scale (HADS). We evaluated whether there was a significant difference in HADS scores for patients who were still not smoking after 6 months and those who had not managed to quit.

RESULTS

The 50 patients were smokers of a mean 39 packs per year (SD 17.82) and had mean scores of 7.4 (SD 4.15) for anxiety and 5.8 (SD 3.93) for depression. Four patients (8%) were unable to complete the study. After one month, 28% of the patients smoked, after 3 months 56% smoked and after 6 months 58% still smoked. The patients who smoked during the first month had higher depression scores than did the non-smokers (p = 0.03). After 3 and 6 months the patients who had managed to continue not smoking were those who had higher anxiety scores than did those who still smoked (p = 0.0052 at 3 months and p = 0.017 at 6 months).

CONCLUSION

Patients who responded better to treatment with bupropion after 6 months of follow-up were those with higher anxiety scores on the HADS. Depression levels influenced outcome only during the first month.

Effect of nonnicotine pharmacotherapy on smoking behavior

Smoking-related disease is the single biggest preventable cause of morbidity and mortality in the United States, yet approximately 25% of Americans continue to smoke. Various dosage forms of nicotine replacement therapy increase smoking quit rates relative to placebo, but they generally do not result in 1-year quit rates of over 20%. To increase these rates, a number of nonnicotine agents have been investigated. Drugs that modulate noradrenergic neurotransmission (bupropion, nortriptyline, moclobemide) are more effective than those affecting serotonin (selective serotonin reuptake inhibitors, buspirone, ondansetron) or other neurotransmitters.

Neurobiology of the nicotine withdrawal syndrome

The aversive aspects of withdrawal from chronic nicotine exposure are thought to be an important motivational factor contributing to the maintenance of the tobacco habit in human smokers. Much emphasis has been placed on delineating the underlying neurobiological mechanisms mediating different components of the nicotine withdrawal syndrome. Recent studies have shown that both central and peripheral populations of nicotinic acetylcholine receptors (nAChRs) are involved in mediating somatic signs of nicotine withdrawal as measured by the rodent nicotine abstinence scale. However, only central populations of nAChRs are involved in mediating affective aspects of nicotine withdrawal, as measured by elevations in brain-stimulation reward thresholds and conditioned place aversion. Nicotine interacts with several neurotransmitter systems, including acetylcholine, dopamine, opioid peptides, serotonin, and glutamate systems. Evidence so far suggests that these neurotransmitters play a role in nicotine dependence and withdrawal processes. The available evidence also suggests that different underlying neurochemical deficits mediate somatic and affective components of nicotine withdrawal. The aim of the present review is to discuss preclinical findings concerning the neuroanatomical and neurochemical substrates involved in these different aspects of nicotine withdrawal.

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.

Phenotypic characterization of an alpha 4 neuronal nicotinic acetylcholine receptor subunit knock-out mouse

Neuronal nicotinic acetylcholine receptors (nAChR) are present in high abundance in the nervous system (Decker et al., 1995). There are a large number of subunits expressed in the brain that combine to form multimeric functional receptors. We have generated an alpha(4) nAChR subunit knock-out line and focus on defining the behavioral role of this receptor subunit. Homozygous mutant mice (Mt) are normal in size, fertility, and home-cage behavior. Spontaneous unconditioned motor behavior revealed an ethogram characterized by significant increases in several topographies of exploratory behavior in Mt relative to wild-type mice (Wt) over the course of habituation to a novel environment. Furthermore, the behavior of Mt in the elevated plus-maze assay was consistent with increased basal levels of anxiety. In response to nicotine, Wt exhibited early reductions in a number of behavioral topographies, under both unhabituated and habituated conditions; conversely, heightened levels of behavioral topographies in Mt were reduced by nicotine in the late phase of the unhabituated condition. Ligand autoradiography confirmed the lack of high-affinity binding to radiolabeled nicotine, cytisine, and epibatidine in the thalamus, cortex, and caudate putamen, although binding to a number of discrete nuclei remained. The study confirms the pivotal role played by the alpha(4) nAChR subunit in the modulation of a number of constituents of the normal mouse ethogram and in anxiety as assessed using the plus-maze. Furthermore, the response of Mt to nicotine administration suggests that persistent nicotine binding sites in the habenulo-interpeduncular system are sufficient to modulate motor activity in actively exploring mice.

Evaluation of current pharmacotherapy of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a severe chronic respiratory condition characterised by progressive, irreversible airflow limitation. It is common, affecting more than 16 million people in the United States and is the fourth highest cause of death. The worldwide incidence of COPD is increasing and, in parallel, the economic and social burden the disease incurs. The treatment of COPD is symptomatic, with no drugs currently available to halt the relentless progression of airflow obstruction. However, with a better understanding of the pathological features of the airway inflammation and alveolar destruction that characterises COPD, new therapeutic strategies are being developed. This article provides a critical evaluation of current pharmacotherapy in COPD, essentially bronchodilators (anticholinergics, beta 2-adrenoceptor agonists and theophylline) and corticosteroids, and an overview of international recommendations for their use.

Advances in non-nicotine pharmacotherapy for smoking cessation

Progress in understanding the pharmacological nature of tobacco addiction, along with the modest success rates achieved by the nicotine replacement therapies, has provided the major impetus for the development of non-nicotine drugs as smoking cessation aids. This article reviews evidence from controlled trials of several non-nicotine medications for the treatment of nicotine dependence. Clonidine was the first non-nicotine medication to show efficacy for smoking cessation in multiple studies, but its effect was found to be limited at best. Positive results across several trials have been consistently demonstrated for amfebutamone (bupropion). Encouraging results have also been observed for nortriptyline and moclobemide. Studies of combined treatments using non-nicotine medications (amfebutamone, mecamylamine, oral dextrose) with nicotine replacement therapy suggest increased efficacy relative to treatments using one or the other treatment strategy alone. Thus, available evidence indicates that non-nicotine drug treatments offer a promising panoply of therapeutic strategies for the addicted smoker.

Anxiolytics for smoking cessation

BACKGROUND

There are two reasons to believe anxiolytics might help in smoking cessation. Anxiety may be a symptom of nicotine withdrawal. Second, smoking appears to be due, in part, to deficits in dopamine, serotonin and norepinephrine, all of which are increased by anxiolytics and antidepressants.

OBJECTIVES

The aim of this review is to assess the effectiveness of anxiolytic drugs in aiding long term smoking cessation. The drugs include buspirone; diazepam; doxepin; meprobamate; ondansetron; and the beta-blockers metoprolol, oxprenolol and propanolol.

SEARCH STRATEGY

We searched the Cochrane Tobacco Addiction Group trials register which includes trials indexed in Medline, Embase, SciSearch and PsycLit, and meetings abstracts.

SELECTION CRITERIA

We considered randomized trials comparing anxiolytic drugs to placebo or an alternative therapeutic control for smoking cessation. We excluded trials with less than 6 months follow-up.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on the type of study population, the nature of the drug therapy, the outcome measures, method of randomisation, and completeness of follow-up. The main outcome measure was abstinence from smoking after at least six months follow-up in patients smoking at baseline. We used the most rigorous definition of abstinence for each trial, and biochemically validated rates if available. Where appropriate, we performed meta-analysis using a fixed effects model.

MAIN RESULTS

There was one trial each of the anxiolytics diazepam, meprobamate, metoprolol and oxprenolol. There were two trials of the anxiolytic buspirone. None of the trials showed strong evidence of an effect for any of these drugs in helping smokers to quit. However, confidence intervals were wide, and an effect of anxiolytics cannot be ruled out on current evidence.

REVIEWER'S CONCLUSIONS

There is no consistent evidence that anxiolytics aid smoking cessation, but the available evidence does not rule out a possible effect.

Non-nicotine pharmacotherapy for smoking cessation

The selection of a non-nicotine treatment is based on the acceptability of various treatments with smokers, the ability to address the specific neurobiology of nicotine addiction, and the option to provide treatment for co-morbid conditions of nicotine-dependent patients. The search for effective treatments for nicotine dependence has generated a wide variety of non-nicotine approaches based on the neuropharmacologic and sensory basis for tobacco use. The only non-nicotine, FDA-approved medication is bupropion, an amino-ketone agent that is believed to work on the dopaminergic and noradrenergic neurotransmitters involved in perpetuating nicotine dependence. This article reviews other unapproved medications, mechanisms of action, and their effectiveness in clinical trials.

Buspirone: future directions

The Food and Drug Administration approved the use of buspirone for generalized anxiety disorder (GAD) in 1986. Since then, numerous studies have examined the efficacy and safety of buspirone for patients with not only generalized feelings of anxiety, but also panic disorder, major depressive disorder, obsessive-compulsive disorder, body dysmorphic disorder, social phobia, posttraumatic stress disorder, selective serotonin reuptake inhibitor-induced adverse events, dementia, behavioral disturbances, attention deficit-hyperactivity disorder, and tobacco dependency. Although relatively few placebo-controlled trials have been conducted on patients with problems other than GAD, an ever-growing body of research suggests future directions for the use of buspirone. This article reviews the body of research relating to new uses for buspirone.

Buspirone use for smoking cessation

The results of buspirone efficacy have been inconsistent and contradictory. The rate of smoking abstinence has been reported to range from 36% to 88% and 16% to 89% in buspirone and placebo treatment groups, respectively. Only one controlled study reported buspirone efficacy in reducing nicotine withdrawal symptoms, although it was based on a small sample population and only 4 weeks of follow-up. The most recent studies have been unable to demonstrate the efficacy of buspirone in smoking cessation or in the relief of withdrawal symptoms. A placebo-controlled, randomized trial with a large number of patients, relatively high doses of buspirone (30-60 mg/d), strict abstinence criteria, long-term follow-up, and the inclusion of smokers with general anxiety or anxiety reported in previous quit attempts is needed to further evaluate buspirone efficacy in smoking cessation and the reduction of nicotine withdrawal symptoms. The treatment effects of buspirone could then be specifically tested as a function of alleviating the anxiety component of the smoking withdrawal syndrome. Finally, buspirone may prove to be an alternative in patients unsuccessful with or unable to tolerate transdermal nicotine therapy. How buspirone compares with bupropion therapy for smoking cessation is also unknown.

Serotonin-1A antagonists attenuate the effects of nicotine withdrawal on the auditory startle response

Withdrawal from the chronic administration of nicotine has previously been shown to lead to an enhanced auditory startle response in rats. In order to explore the neuropharmacology and neurophysiology underlying this phenomenon, we examined the effects of various 5-hydroxytryptamine (5-HT)-1A antagonists and agonists on the nicotine-withdrawal-enhanced auditory startle response in male rats. Animals were treated with nicotine (6 mg/kg/day nicotine base, via subcutaneously implanted osmotic minipumps) for 12 days. After 12 days the pumps were removed and the animals allowed to undergo spontaneous withdrawal for several days. In agreement with previous results, nicotine withdrawal led to a significant elevation of the auditory startle response. Pretreatment with the 5-HT-1A agonists (+)8-OH-DPAT (0.001-0.1 mg/kg) and LY274600 (0.3-3.0 mg/kg) either had no affect or exacerbated the nicotine-withdrawal-enhanced startle response. Pretreatment with the 5-HT-1A antagonists NAN-190 (1-3 mg/kg), LY206130 (1-10 mg/kg), or WAY-100635 (0.1-1.0 mg/kg) blocked the increase in the startle response caused by nicotine withdrawal at doses that had no effect on baseline startle responses. These data indicate that 5-HT-1A receptors play a role in the neurophysiology of nicotine withdrawal. In addition, 5-HT-1A antagonists may be able to relieve some nicotine withdrawal symptoms in man and may represent a novel pharmacotherapy for smoking cessation.