Brief report

Clozapine decreases smoking in patients with chronic schizophrenia

A retrospective study was conducted to analyze prescription pattern of clozapine in dual diagnosis inpatients' and to find out if there was any association between clozapine prescription and acute relapses either from psychiatric symptoms or from substance use disorder. All patients admitted at Lisbon's Psychiatric Hospital Center during a 4 months' period for psychiatric inpatient treatment with a dual diagnosis at discharge were selected and their clinical files were screened. From 536 patients, 17,5% had a dual diagnosis at discharge. Most frequent psychiatric diagnosis associated with substance use disorder was schizophrenia (50%), followed by major depression disorder (17%) and bipolar disorder (10,6%). Most frequent substance of abuse was alcohol, followed by cannabinoids, nicotine, cocaine, and opiates. At least one antipsychotic drug was prescribed to 85,1% patients, and clozapine was prescribed to 22,3%. There was a statistically significant association between clozapine prescription and prevention of acute relapses of psychiatric symptoms in dual diagnosis patients. Although there was no significant association between prescription of clozapine versus other antipsychotic drugs in the prevention of relapses of substance use, there was a larger than expected number of patients in clozapine that didn't have a relapse of substance use.

Almost fifty years after its first introduction into clinical care, clozapine remains the only evidence-based pharmacological option for treatment-resistant schizophrenia (TRS), which affects approximately 30% of patients with schizophrenia.

Despite the long-time experience with clozapine, the specific mechanism of action (MOA) responsible for its superior efficacy among antipsychotics is still elusive, both at the receptor and intracellular signaling level. This systematic review is aimed at critically assessing the role and specific relevance of clozapine’s multimodal actions, dissecting those mechanisms that under a translational perspective could shed light on molecular targets worth to be considered for further innovative antipsychotic development.

In vivo and in vitro preclinical findings, supported by innovative techniques and methods, together with pharmacogenomic and in vivo functional studies, point to multiple and possibly overlapping MOAs. To better explore this crucial issue, the specific affinity for 5-HT₂R, D1R, α_2c, and muscarinic receptors, the relatively low occupancy at dopamine D2R, the interaction with receptor dimers, as well as the potential confounder effects resulting in biased ligand action, and lastly, the role of the moiety responsible for lipophilic and alkaline features of clozapine are highlighted. Finally, the role of transcription and protein changes at the synaptic level, and the possibility that clozapine can directly impact synaptic architecture are addressed. Although clozapine’s exact MOAs that contribute to its unique efficacy and some of its severe adverse effects have not been fully understood, relevant information can be gleaned from recent mechanistic understandings that may help design much needed additional therapeutic strategies for TRS.

Lifetime prevalence of substance use disorders (SUD) in patients with schizophrenia is nearly 50%. Nicotine, alcohol, and cannabis are the substances most frequently used, with a high percentage of poly-substance users. There are few available data about pharmacological approaches in this population. Amongst antipsychotics, clozapine shows positive evidence in the literature. The aim of the present article is to provide systematic review on the efficacy of clozapine in SUD improvement in schizophrenic patients. PRISMA recommendations were followed (PROSPERO id: CRD42017059299). Five studies for nicotine use and nine studies for SUD (other than nicotine) were analyzed. Regarding nicotine use, results from randomized controlled trials (RCT) have found a decrease in nicotine use after 12 weeks of 200–600 mg/day clozapine, as compared with lower doses. In SUD improvement (other than nicotine), RCT have shown superiority of clozapine when compared with risperidone, in short-term studies (from 4 to 12 weeks) performed in cannabis users. In long-term studies (1 year), clozapine was equal to ziprasidone in reducing cannabis use and equal to treatment as usual in reducing alcohol use. We conclude that positive results on nicotine use are scarce and derived from studies with a low degree of evidence. Evidence of clozapine on SUD (other than nicotine) is stronger, especially when clozapine is compared with first generation antipsychotics in poly-substance users. When compared with second generation antipsychotics, clozapine was superior to risperidone but equal to olanzapine or ziprasidone in poly-substance and cannabis users.

Tobacco use is common in patients with schizophrenia (SZ) but little is known on the role of tobacco in the physiopathology or on the course of the disease. Only few studies embrace an extensive examination of clinical and therapeutic characteristics in stabilized patients. The objective of the present study was to determine the prevalence of tobacco smoking in stabilized SZ outpatients and the clinical and treatment characteristics associated with daily tobacco use in a large community-dwelling sample of patients.

Three-hundred-and-sixty-one patients were included in the network of the FondaMental Expert Centers for Schizophrenia. Current tobacco status was self-declared.

53.7% were smokers. Mean age at tobacco onset was 17.2 years old. In multivariate analyses, after adjustment for confounding factors, positive symptoms and mean daily antipsychotic dose were associated with a higher frequency of tobacco use (OR = 1.06 95%IC[1.02–1.12], for positive symptoms, OR = 1.1, 95%IC[1.02–1.18] for daily antipsychotic dose). Education level, negative symptoms, anticholinergic agents, clozapine or aripiprazole administration were independently associated with a lower frequency of tobacco use (respectively OR = 0.87, 95%IC [0.79, 0.95], OR = 0.95, 95%IC[0.91–0.98], OR = 0.41, 95%IC[0.22–0.76], OR = 0.56, 95%IC = [0.32, 0.99] and OR = 0.49, 95%IC [0.26–0.91]).

The prevalence of current tobacco smoking in a French community-dwelling SZ patients is higher that observed in the general population. Patients with tobacco use present clinical and therapeutic specificities that may involve interaction between cholinergic-nicotinic and dopaminergic systems. The present study suggests that some therapeutics may improve daily smoking behavior in smokers. These results should be confirmed in longitudinal studies.

The estimated mortality gap between those with and without serious mental illness (SMI) is increasing, now estimated at 28 years, which is largely due to smoking-related diseases.

We sought to identify predictors of 14-day continuous abstinence in stable outpatient smokers with SMI.

Adult smokers with schizophrenia spectrum (n = 130) or bipolar disorder (n = 23) were enrolled in a 12-week course of varenicline and cognitive-behavioral therapy for smoking cessation.

Independent predictors of abstinence included reduction in withdrawal symptoms prior to the quit day, fewer cigarettes smoked per day at baseline, better baseline attention, remitted alcohol dependence, and lower expectation of peer support to aid quitting.

Interventions that consider these targets may improve smoking cessation outcomes in those with SMI.

Although functional abnormalities of the salience network are associated with schizophrenia, the acute effects of nicotine on its function and network dynamics during the resting state in patients are poorly understood. In this study, the effects of a 7 mg nicotine patch (vs. placebo) on salience network connectivity were examined in 17 patients with schizophrenia and 19 healthy subjects. We hypothesized abnormal connectivity between the salience network and other major networks (e.g. executive network) in patients under placebo administration and amelioration of this difference after nicotine. We also examined effects of nicotine on betweenness centrality (a measure of the influence of a region on information transfer throughout the brain) and local efficiency (a measure of local information transfer) of the network. A hybrid independent component analysis (ICA)/seed-based connectivity approach was implemented in which the salience network was extracted by ICA and cortical network peaks (anterior cingulate cortex (ACC), left and right insula) were used as seeds for whole-brain seed-to-voxel connectivity analysis. Significant drug X diagnosis interactions were observed between the ACC seed and superior parietal lobule and ventrolateral prefrontal cortex. A significant interaction effect was also observed between the left insula seed and middle cingulate cortex. During placebo conditions, abnormal connectivity predicted negative symptom severity and lower global functioning in patients. A significant drug X diagnosis interaction was also observed for betweenness centrality of the ACC. These results suggest that nicotine may target abnormalities in functional connectivity between salience and executive network areas in schizophrenia as well as affect the ability of the salience network to act as an integrator of global signaling in the disorder.