Mecamylamine treatment for alcohol dependence: a randomized controlled trial

Effectiveness of contingency management using transdermal alcohol monitoring to reduce heavy drinking among driving while intoxicated (DWI) arrestees: A randomized controlled trial

BACKGROUND

Driving while intoxicated (DWI) is a serious public health problem. However, treatment for DWI arrestees is not readily available. This study examines the effectiveness of a contingency management (CM) procedure using transdermal alcohol concentration (TAC) monitoring to reduce drinking among DWI arrestees.

METHOD

The study participants were 216 DWI arrestees under pretrial and included both Mandated participants undergoing court-ordered TAC monitoring and Non-Mandated participants wearing a study-provided TAC monitor. Participants were randomly assigned to either a CM (Mandated = 35; Non-Mandated = 74) or a Control condition (Mandated = 37; Non-Mandated = 70) and completed the 8-week intervention. CM participants received $50/week for not exceeding a TAC of 0.02 g/dL during the previous week. Payments to Controls were yoked to the CM group.

RESULTS

Among Non-Mandated participants, the probability of meeting the contingency was higher and remained stable (about 65%) over time in the CM group, whereas the probability was lower and declined in the Control group, widening the gaps in the probability between the study conditions (16.7%-24.1% greater in the CM group from visit 4 to 8, all p < 0.05). Among Mandated participants, the probability was not significantly different between conditions (p = 0.06-0.95). Furthermore, among Non-Mandated participants, the percentage of heavy drinking days remained low (9.16%-11.37%) in the CM group, whereas it was greater and increased over time (17.43%-26.59%) in the Control group. In Mandated participants, no significant differences in percent heavy drinking days were observed between conditions (p = 0.07-0.10).

CONCLUSION

We found that contingency effects on alcohol use are more pronounced among frequent and heavy alcohol users, i.e., Non-Mandated DWI arrestees. However, for individuals whose drinking was already suppressed by existing contingencies (i.e., court-mandated TAC monitoring), our CM procedure did not produce additional reductions in drinking.

Pharmacological Treatment of Alcohol Cravings

(1) Background: The treatment of substance addiction is challenging and has persisted for decades, with only a few therapeutic options. Although there are some recommendations for specific treatments for Alcohol Use Disorder (AUD), there is no specific medication used to treat alcohol cravings, which could benefit millions of patients that are suffering from alcoholism. Cravings, or the urge to use drugs, refer to the desire to experience the effects of a previously experienced psychoactive substance. (2) Methods: We included original studies of alcohol abuse or dependence extracted from a controlled, blind, pharmacological treatment study which presented measures and outcomes related to alcohol cravings. (3) Results: Specific drugs used for the treatment of alcoholism, such as Naltrexone and Acamprosate, have had the best results in relieving craving symptoms, as well as promoting abstinence. Baclofen and anticonvulsants such as Gabapentin and Topiramate have shown good results in promoting abstinence and the cessation of cravings. (4) Conclusions: Specific drugs used for the treatment of alcoholism to obtain the best results can be considered the gold standard for promoting abstinence and relieving cravings. Anticonvulsants and Baclofen also had good results, with these medications being considered as second-line ones. Varenicline is an option for alcohol dependents who also concomitantly ingest tobacco.

Nicotinic and muscarinic acetylcholine receptor antagonism dose-dependently decreases sign- but not goal-tracking behavior in male rats

RATIONALE

Acetylcholinergic antagonists have shown some promise in reducing addiction-related behaviors in both preclinical and clinical studies. However, the psychological mechanisms by which these drugs are able to affect addictive behavior remain unclear. A particular key process for the development of addiction is the attribution of incentive salience to reward-related cues, which can be specifically measured in animals using a Pavlovian conditioned approach procedure. When confronted with a lever that predicts food delivery, some rats engage with the lever directly (i.e., they sign track), indicating attribution of incentive-motivational properties to the lever itself. In contrast, others treat the lever as a predictive cue and approach the location of impending food delivery (i.e., they goal track), without treating the lever itself as a reward.

OBJECTIVES

We tested whether systemic antagonism of the either nicotinic or muscarinic acetylcholine receptors would selectively affect sign- or goal-tracking behavior, indicating a selective effect on incentive salience attribution.

METHODS

A total of 98 male Sprague Dawley rats were either given the muscarinic antagonist scopolamine (100, 50, or 10 µg/kg i.p.) or the nicotinic antagonist mecamylamine (0.3, 1.0, or 3 mg/kg i.p.) before being trained on a Pavlovian conditioned approach procedure.

RESULTS

Scopolamine dose-dependently decreased sign tracking behavior and increased goal-tracking behavior. Mecamylamine reduced sign-tracking but did not affect goal-tracking behavior.

CONCLUSIONS

Antagonism of either muscarinic or nicotinic acetylcholine receptors can reduce incentive sign-tracking behavior in male rats. This effect appears to be specifically due to a reduction in incentive salience attribution since goal-tracking either increased or was not affected by these manipulations.

The role of nicotinic receptors in alcohol consumption

The use of alcohol causes significant morbidity and mortality across the globe. Alcohol use disorder (AUD) is defined by the excessive use of this drug despite a negative impact on the individual's life. While there are currently medications available to treat AUD, they have limited efficacy and several side effects. As such, it is essential to continue to look for novel therapeutics. One target for novel therapeutics is nicotinic acetylcholine receptors (nAChRs). Here we systematically review the literature on the involvement of nAChRs in alcohol consumption. Data from both genetic and pharmacology studies provide evidence that nAChRs modulate alcohol intake. Interestingly, pharmacological modulation of all nAChR subtypes examined can decrease alcohol consumption. The reviewed literature demonstrates that nAChRs should continue to be investigated as novel therapeutics for AUD.

Smoking As an Outcome Moderator In the Treatment of Alcohol Use Disorders

AIMS

To clarify whether smoking interferes with successful treatment of alcohol use disorder (AUD).

METHODS

The current systematic review investigates the potential moderating effect of smoking on behavioural and pharmacological treatment of AUD. In addition, this review summarizes the results of randomized controlled trials investigating the effect of smoking cessation treatments in subjects with AUD on drinking outcomes.

RESULTS

Overall, the results show that 16 out of the 31 pharmacological and psychotherapeutic alcohol treatment studies showed that being a non-smoker or decreased tobacco consumption during AUD treatment is associated with beneficial drinking outcomes, including reduced drinking, later relapse and prolonged alcohol abstinence. As such, smoking predicts poorer drinking outcomes in alcohol treatments. In the stop-smoking studies in patients with AUD, reduced smoking had virtually no effect on drinking behaviours. The inverse association between smoking and drinking outcome observed here indicates that non-smokers may be more successful to attain alcohol abstinence than smokers do. However, this association does not imply per se that smoking triggers alcohol consumption, since it can also mean that alcohol consumption promotes smoking.

CONCLUSIONS

It is concluded that (continued) tobacco smoking may have a negative moderating effect on the treatment outcome of AUD treatments. To optimize treatment outcome of AUD one may consider informing and counselling patients with AUD about the risks of smoking for treatment outcomes and offering support for smoking cessation.

Mecamylamine inhibits seizure-like activity in CA1-CA3 hippocampus through antagonism to nicotinic receptors

Cholinergic modulation of hippocampal network function is implicated in multiple behavioral and cognitive states. Activation of nicotinic and muscarinic acetylcholine receptors affects neuronal excitability, synaptic transmission and rhythmic oscillations in the hippocampus. In this work, we studied the ability of the cholinergic system to sustain hippocampal epileptiform activity independently from glutamate and GABA transmission. Simultaneous CA3 and CA1 field potential recordings were obtained during the perfusion of hippocampal slices with the aCSF containing AMPA, NMDA and GABA receptor antagonists. Under these conditions, spontaneous epileptiform discharges synchronous between CA3 and CA1 were recorded. Epileptiform discharges were blocked by addition of the calcium-channel blocker Cd²⁺ and disappeared in CA1 after a surgical cut between CA3 and CA1. Cholinergic antagonist mecamylamine abolished CA3-CA1 synchronous epileptiform discharges, while antagonists of α7 and α4β2 nAChRs, MLA and DhβE, had no effect. Our results suggest that activation of nicotinic acetylcholine receptors can sustain CA3-CA1 synchronous epileptiform activity independently from AMPA, NMDA and GABA transmission. In addition, mecamylamine, but not α7 and α4β2 nAChRs antagonists, reduced bicuculline-induced seizure-like activity. The ability of mecamylamine to decrease hippocampal network synchronization might be associated with its therapeutic effects in a wide variety of CNS disorders including addiction, depression and anxiety.

A Critical Review of Alcohol Administration Guidelines in Laboratory Medication Screening Research: Is It Time to Include Treatment Seekers?

Human laboratory studies play an important role in alcohol use disorder (AUD) medication development. Medications that are found to be safe and effective during human laboratory screening will then move to more expensive clinical trials in patient populations. Given the gatekeeping role of human laboratory studies in the medication development pipeline, it is critical that these studies accurately forecast how pharmacotherapies will perform under true-to-life clinical conditions. On the other hand, the design of these studies also must adhere to ethical guidelines: certain aspects of clinical reality cannot be incorporated into screening studies because doing so might place the participant at risk for harm or breach other ethical guidelines. Conventions exist that guide the resolution of these conflicting ideals. This article considers the practice of recruiting non-treatment-seeking heavy drinkers to participate in laboratory screening studies. By convention, volunteers are excluded from laboratory screening studies that involve alcohol administration if they are deemed "treatment seeking," meaning that they recently stopped drinking or are motivated to do so. Although this common practice may reduce risk to participants, findings may not accurately predict medication effects on treatment seekers. Indeed, there is empirical evidence that treatment seekers differ from nontreatment seekers in their responses to medications (Neuropsychopharmacology 2017a; 42: 1776; Am J Drug Alcohol Abuse 2017b; 43: 703; J Psychiatr Res 2006; 40: 383). Here, we argue for the importance of recruiting treatment seekers for this research due to their qualitative difference from nontreatment seekers. We argue that these individuals should be the default population in human laboratory medication screening studies. We conclude by discussing 2 case examples of medication experiments led by our research groups that involved administering medications to treatment seekers.

The role of nicotinic acetylcholine receptors in alcohol-related behaviors

Alcohol use disorder (AUD) causes an alarming economic and health burden in the United States. Unfortunately, this disease does not exist in isolation; AUD is highly comorbid with nicotine use. Results from both human and animal models demonstrate a genetic correlation between alcohol and nicotine behaviors. These data support the idea of shared genetic and neural mechanisms underlying these behaviors. Nicotine acts directly at nicotinic acetylcholine receptors (nAChR) to have its pharmacological effect. Interestingly, alcohol also acts both directly and indirectly at these receptors. Research utilizing genetically engineered rodents and pharmacological manipulations suggest a role for nAChR in several ethanol behaviors. The current manuscript collates this literature and discusses findings that implicate specific nAChR subunits in ethanol phenotypes. These data suggest future directions for targeting nAChR as novel therapeutics for AUD.

Reduced expression of ethanol sensitization by α3β4 nicotinic acetylcholine receptors in DBA/2J mice

Alcohol use disorder (AUD) is a leading cause of preventable death in the United States, however existing treatments are ineffective and produce aversive side effects such as nausea and fatigue. One potential therapeutic for AUD is the α3β4 nicotinic acetylcholine receptor (nAChR) antagonist 18-methoxycoronaridine (18-MC). Prior work has shown that 18-MC reduces ethanol consumption in rodent models. The present study sought to further examine the therapeutic potential of 18-MC by testing its effects on nonconsummatory behaviors. We examined 2 behavioral measures: ethanol-induced locomotor stimulation, which measures euphoric properties of the drug, and the expression of locomotor sensitization which models neuroadaptations in response to repeated exposure. We tested dose-dependent effects of 18-MC (0, 10, 20 and 30 mg/kg) administration on ethanol stimulation and locomotor sensitization in female and male DBA/2J mice. 18-MC had no effect on acute ethanol-induced stimulation, but the highest dose (30 mg/kg) significantly decreased the expression of locomotor sensitization. Our results support the involvement of α3β4 nAChR in the expression of ethanol-induced locomotor sensitization and suggest that 18-MC may be a therapeutic for AUD. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Prospects for pharmacotherapies to treat alcohol use disorder: an update on recent human studies

PURPOSE OF REVIEW

The aim of this study was to provide an update on medication development efforts for alcohol use disorder (AUD) by reviewing recently published (past 2 years) human studies that evaluated medications' effects on alcohol-related outcomes.

RECENT FINDINGS

Forty-five publications were found suitable for this review. A variety of compounds have been tested in the past 2 years as potential pharmacological options for AUD, including medications that act on multiple targets (topiramate, aripiprazole, quetiapine), calcium channels (gabapentin), gamma-Aminobutyric acid receptors (baclofen, diazepam), glutamate receptors (ifenprodil, memantine, glycine), nicotinic acetylcholine receptors (varenicline, mecamylamine), α1 adrenergic receptors (prazosin, doxazosin), neuroendocrine pathways (oxytocin, a vasopressin receptor 1b antagonist, a ghrelin receptor inverse agonist) and others (samidorphan, ibudilast, N-acetylcysteine, citoline). Important findings and limitations regarding the effects of these medications on alcohol-related outcomes are discussed.

SUMMARY

There is a critical need to increase the armamentarium of medications for AUD. Human laboratory studies may help screen and prioritize promising targets and compounds before running large clinical trials. Given the complexity of AUD and the heterogeneity of afflicted patients, future studies should also investigate potential moderators and predictors of response to each pharmacological intervention.

Selecting an appropriate alcohol pharmacotherapy: review of recent findings

PURPOSE OF REVIEW

Only a few pharmacological treatments are available for treating alcohol use disorders (AUDs). Disulfiram, naltrexone and acamprosate are Food and Drug Administration (FDA)-approved and nalmefene is EMA-approved in European Union. Off-label medications, such as baclofen, gabapentin, ondansetron and topiramate are medications commonly prescribed for the treatment of AUD. The aim of this review is to give an update on recent randomized controlled trials (RCTs) and reviews evaluating pharmacological treatment for AUD.

RECENT FINDINGS

A literature search was conducted for pharmacological treatment for alcohol use disorder, published from January 2017 to January 2019. An additional search from two ongoing-study databases was performed. A total of 13 studies, 11 reviews and 7 on-going clinical trials were identified. Interest in studying baclofen as a treatment for AUD was greater compared with other medications, yet with inconclusive results. Three new RCTs of first-line medication naltrexone showed reduction in drinking.

SUMMARY

Three new published RCTs focus on baclofen and naltrexone. These results are consistent with old findings demonstrating that naltrexone reduces heavy drinking. Several RCT on baclofen do not support the use of baclofen for treatment of AUD. Encouraging results have been reported for topiramate, gabapentin and also varenicline, which might be useful in patients with comorbid nicotine dependence.

Tobacco use during a clinical trial of mecamylamine for alcohol dependence: Medication effects on smoking and associations with reductions in drinking

Mecamylamine is a nicotinic acetylcholine receptor (nAChR) antagonist that was recently used in a clinical trial to treat alcohol use disorder (AUD) in both smokers and non-smokers. The current manuscript reports a reanalysis of data from this clinical trial in which we examine changes in smoking that occurred over the course of the trial. We focused on examining the effects of mecamylamine on smoking and the association between reductions in alcohol use and smoking. Participants were the subgroup of smokers who participated in the clinical trial of mecamylamine (10 mg/day) to treat their AUD (n = 76). Smoking was assessed prior to randomization and tracked throughout the course of the 12-week medication treatment phase. Participants were categorized as treatment responders or non-responders based on their changes in drinking over the course of the clinical trial. Participants showed a reduction in smoking over the course of the clinical trial, but there were no significant differences in smoking outcomes between the mecamylamine and placebo groups. Among moderate/high dependence smokers, those who successfully reduced drinking showed a significant reduction in cigarettes smoked per day over the clinical trial. Mecamylamine had no detectable effect on smoking outcomes. Reductions in alcohol use predicted more favorable smoking outcomes among moderate/high tobacco dependence smokers irrespective of medication condition. The reduction in smoking among patients who decreased their alcohol use responders highlights an opportunity for patients being treated for AUD to reduce their smoking.

Differential regulation of alcohol taking and seeking by antagonism at α4β2 and α3β4 nAChRs

RATIONALE

Alcoholism is a serious public health problem throughout the world. Current pharmacotherapies for the treatment of this disorder are poorly effective. Preclinical and clinical findings point to nicotinic acetylcholine receptors (nAChRs) as a promising target for the development of novel and effective medications. Assuage Pharmaceuticals, in collaboration with Torrey Pines Institute for Molecular Studies, has discovered a new class of potent and selective α4β2 nAChR antagonists.

OBJECTIVE

Here, it was hypothesized that α4β2 nAChR antagonism is a viable approach for treatment of alcohol use disorders.

RESULTS

When tested in rats, one lead compound, AP-202, attenuated both operant alcohol and nicotine self-administration in a paradigm in which the two reinforcers were concurrently available. The conotoxin TP2212-59, a selective α3β4 nAChR antagonist, was only effective in reducing nicotine self-administration. AP-202 also reduced alcohol but not food responding when alcohol was presented as the only reinforcer, whereas the commercially available α4β2 nAChR antagonist dihydro-β-erythroidine failed to alter alcohol self-administration. AP-202 did not block relapse-like behavior induced by previously alcohol-associated stimuli or yohimbine stress. In a reinstatement paradigm, in which alcohol seeking was triggered by a nicotine challenge, a behavior successfully inhibited by the nonselective nAChR antagonist mecamylamine, AP-202 was not effective, while pretreatment with TP2212-59 abolished nicotine-induced reinstatement of alcohol seeking.

CONCLUSIONS

These findings suggest differential roles for α4β2 and α3β4 nAChR on alcohol taking and seeking with selective blockade of α4β2 nAChR being more implicated in modulating alcohol taking while selective blockade of α3β4 nAChR is involved in nicotine-induced alcohol seeking.

Negative Affect Intensity and Hostility in Individuals With Alcohol Use Disorder With or Without Posttraumatic Stress Disorder

OBJECTIVE

Negative affect intensity and hostility have both been implicated in alcohol use disorders (AUD) and posttraumatic stress disorder (PTSD) when they occur separately, but neither have been compared or explored among those with comorbid AUD and PTSD. This study is a secondary analysis designed to compare levels of negative affect intensity and hostility among those with AUD to those with comorbid AUD and PTSD.

METHODS

Participants (n = 113) were recruited from the placebo-controlled groups of two distinct 12-week clinical trials (NCT00342563 and NCT00744055). The Short Affect Intensity Scale and Buss-Durkee Hostility Inventory were administered at weeks 0, 4, 8, and 12 to all study participants to assess negative affect intensity and hostility levels, respectively.

RESULTS

Individuals with comorbid AUD and PTSD showed significantly higher levels of negative affect intensity and hostility than individuals with AUD only. These levels remained relatively stable over the course of the study in spite of all study participants showing clinically significant improvements in AUD severity and PTSD symptomatology (for those with dual diagnosis).

CONCLUSIONS

Our results indicate that individuals with comorbid AUD and PTSD have higher levels of negative affect and higher levels of hostility compared to individuals with AUD alone. In addition, these heightened levels of negative affect intensity and hostility appear to function somewhat independently of diagnosis severity and symptomatology improvement. To our knowledge, this is the first study to compare negative affect intensity and hostility levels between individuals with AUD alone and those with comorbid AUD and PTSD.

Designing selective modulators for the nicotinic receptor subtypes: challenges and opportunities

Nicotinic receptors are membrane proteins involved in several physiological processes. They are considered suitable drug targets for various CNS disorders or conditions, as shown by the large number of compounds which have entered clinical trials. In recent years, nonconventional agonists have been discovered: positive allosteric modulators, allosteric agonists, site-specific agonists and silent desensitizers are compounds able to modulate the receptor interacting at sites different from the orthodox one, or to desensitize the receptor without prior opening. While these new findings can further complicate the pharmacology of these proteins and the design and optimization of ligands, they undoubtedly offer new opportunities to find drugs for the many therapeutic indications involving nicotinic receptors.