Randomized Clinical Trials Investigating Innovative Interventions for Smoking Cessation in the Last Decade

The Nicotinic Agonist Cytisine: The Role of the NH···N Interaction

We report a detailed structural study of cytisine, an alkaloid used to help with smoking cessation, looking forward to unveiling its role as a nicotinic agonist. High-resolution rotational spectroscopy has allowed us to characterize two different conformers exhibiting axial and equatorial arrangements of the piperidinic NH group. Unexpectedly, the axial form has been found as the predominant configuration, in contrast to that observed for related molecules, such as piperidine. This anomalous behavior has been justified in terms of an intramolecular NH···N hydrogen bond. Moreover, this interaction justifies the overstabilization of the axial conformer over the equatorial one and is crucial for the mechanism of action of cytisine over the nicotinic receptor, further rationalizing its behavior as a nicotinic agonist.

Is there a therapeutic potential in combining bupropion and naltrexone in schizophrenia?

INTRODUCTION

A sustained-release tablet composed of a combination of the dopamine and norepinephrine reuptake inhibitor bupropion (BUP) and the µ-opioid receptor antagonist naltrexone (NAT) is marketed under the brand name Contrave by Orexigen Therapeutics for appetite control. Minimal literature is available regarding the use of combination bupropion and naltrexone (BUPNAT) in individuals with schizophrenia.

AREAS COVERED

In this review, we propose a theoretical model where BUPNAT may have a therapeutic effect in the treatment of schizophrenia. We explore the pathways targeted by the constituent drugs BUP and NAT and summarize the literature on their efficacy and possible adverse effects. We then look at the potential use of BUPNAT in schizophrenia.

EXPERT OPINION

Research has hinted that BUP's dopaminergic properties affect the same striatal pathways involved in schizophrenia. NAT, via opioid receptor antagonism, indirectly increases striatal dopamine release by disinhibiting nicotinic acetylcholine receptors. As such, we hypothesize that BUPNAT can have a therapeutic effect in schizophrenia, particularly on negative symptoms. We also suggest that it may ameliorate comorbidities frequently seen in this group of patients, including obesity, smoking, and substance use. Further research and clinical data are needed to elucidate the potential clinical benefits of BUPNAT in the treatment of schizophrenia.

Evaluating N-acetylcysteine for early and end-of-treatment abstinence in adult cigarette smokers

BACKGROUND

There is robust preclinical literature and preliminary clinical findings supporting the use of N-Acetylcysteine (NAC) to treat substance use disorders, including tobacco use disorder (TUD). However, randomized controlled trials have yielded mixed results and NAC's efficacy for TUD has not been established. The goals of this study were to assess the efficacy of NAC in promoting early and end-of-treatment abstinence and preventing relapse among adult smokers.

METHODS

This randomized, double-blinded clinical trial enrolled adult, daily smokers (N = 114; ages 23-64; 51 % female; 65 % White; 29 % Black/African American; 7% Hispanic/Latinx), who were randomized 1:1 to receive NAC (n = 59) or placebo (n = 55) (1200 mg b.i.d.) for eight weeks. Participants received brief cessation counseling and incentives for abstinence during the first three days of the quit attempt. Primary outcomes: (i) carbon monoxide (CO)-confirmed abstinence during the first three days of the quit attempt.

SECONDARY OUTCOMES

(ii) time to relapse; (iii) biologically confirmed abstinence at Week 8.

RESULTS

No differences were found between NAC and placebo groups on measures of early abstinence (3-day quit attempt; 11 % for NAC vs. 15 % for placebo; all p > 0.11), time to relapse (p = 0.19), and end-of-treatment abstinence (7% for NAC vs. 11 % for placebo; all p > 0.40].

CONCLUSIONS

Results indicate that NAC is a well-tolerated pharmacotherapy but is unlikely to be efficacious as a monotherapy for TUD in adults. Considered in the collective context of other research, NAC may potentially be more useful in a younger population, as a combination pharmacotherapy, or in the presence of more intensive psychosocial treatment.

Cytisine and cytisine derivatives. More than smoking cessation aids

Cytisine, a natural bioactive compound that is mainly isolated from plants of the Leguminosae family (especially the seeds of Laburnum anagyroides), has been marketed in central and eastern Europe as an aid in the clinical management of smoking cessation for more than 50 years. Its main targets are neuronal nicotinic acetylcholine receptors (nAChRs), and pre-clinical studies have shown that its interactions with various nAChR subtypes located in different areas of the central and peripheral nervous systems are neuroprotective, have a wide range of biological effects on nicotine and alcohol addiction, regulate mood, food intake and motor activity, and influence the autonomic and cardiovascular systems. Its relatively rigid conformation makes it an attractive template for research of new derivatives. Recent studies of structurally modified cytisine have led to the development of new compounds and for some of them the biological activities are mediated by still unidentified targets other than nAChRs, whose mechanisms of action are still being investigated. The aim of this review is to describe and discuss: 1) the most recent pre-clinical results obtained with cytisine in the fields of neurological and non-neurological diseases; 2) the effects and possible mechanisms of action of the most recent cytisine derivatives; and 3) the main areas warranting further research.