Clozapine reconstructed: Haloperidol's ability to reduce alcohol intake in the Syrian golden hamster can be enhanced through noradrenergic modulation by desipramine and idazoxan

Prevention of suicide by clozapine in mental disorders: systematic review

BACKGROUND

Previous research has investigated the efficacy of clozapine in reducing suicidality in patients with schizophrenia and schizoaffective disorder. We aimed to systematically review published evidence, including studies concerning clozapine administration to treat: (a) refractory suicidality in other mental disorders, including bipolar disorder and borderline and other personality disorders; and (b) refractory cases of non-suicidal self-injury.

METHOD

We performed a PUBMED-search (last day: July 17, 2022) of English-language studies, combining the keywords "clozapine", "suicidality", and "suicide" with various psychopathological terms (e.g. "schizophrenia"). All duplications were eliminated.

RESULTS

Fifty-one studies were eligible for inclusion in the review. Most studies suggest a superior anti-suicide effect of clozapine in schizophrenia/schizoaffective disorder, compared to other antipsychotics, or no antipsychotic therapy, which is not due to the close monitoring of patients for blood dyscrasias. No consensus exists as to whether other antipsychotic drugs share this effect. Discontinuation of clozapine is associated with increases in suicidality. Reductions in refractory suicidality/NSSI are observed in clozapine-treated patients with bipolar disorder or borderline personality disorder, but the evidence is limited. Potential biological underpinnings of the anti-suicide effect of clozapine include its unique profile of modulation of brain neurotransmitters; its non-selectivity for neurotransmitter receptors; specific genetic and hormonal factors; effects on neuroinflammation; and ability to elicit epileptiform activity.

CONCLUSION

The superior anti-suicide effect of clozapine in schizophrenia/schizoaffective disorder patients is well established. It may have a role in severe and refractory cases of suicidality and non-suicidal self-injury in patients with bipolar disorder or borderline personality disorder, but the level and quality of supporting evidence is limited.

The role of alcohol intake in the pharmacogenetics of treatment with clozapine

Clozapine (CLZ) is an atypical antipsychotic reserved for patients with refractory psychosis, but it is associated with a significant risk of severe adverse reactions (ADRs) that are potentiated with the concomitant use of alcohol. Additionally, pharmacogenetic studies have explored the influence of several genetic variants in CYP450, receptors and transporters involved in the interindividual response to CLZ. Herein, we systematically review the current multiomics knowledge behind the interaction between CLZ and alcohol intake, and how its concomitant use might modulate the pharmacogenetics. CYP1A2*1F, *1C and other alleles not yet discovered could support a precision medicine approach for better therapeutic effects and fewer CLZ ADRs. CLZ monitoring systems should be amended and include alcohol intake to protect patients from severe CLZ ADRs.

Alcohol intake potentiates clozapine adverse effects associated to CYP1A2*1C in patients with refractory psychosis

Clozapine (CLZ) is an atypical antipsychotic and the gold standard for refractory psychosis treatment. However, there is little information regarding pharmacogenetics of CLZ in patients with refractory psychosis and its clinical correlation with alcohol intake. Although neurological effects of CLZ in patients with concomitant alcohol intake are documented, its use is very common in patients with psychosis. We explored the impact of CYP1A2, CYP2D6, CYP2C19, and CYP3A4 genetic variants on CLZ pharmacokinetics and side effects, along with coffee/alcohol/tobacco consumption habits and clinical data of 48 adult patients with refractory psychosis on CLZ antipsychotic monotherapy. Relevant CYP variants in CLZ metabolism were evaluated by targeted genotyping and multiplex ligation-dependent probe amplification. CLZ and its main metabolite plasma concentrations were determined by high performance liquid chromatography. Biochemical and molecular data, along with other potential confounders, were included in the analysis by linear regression. Overall, CYP variants showed no effect on CLZ pharmacokinetics. The rs2069514 variant in homozygous genotype (also known as CYP1A2*1C/*1C) was associated with CLZ adverse reactions in Mexican patients with refractory psychosis (OR = 3.55 CI₉₅  = 1.041-12.269, p = .043) and demonstrated that this effect is doubled by concomitant alcohol consumption (OR = 7.9 CI₉₅  = 1.473-42.369, p = .016). Clinicians should be aware of this information before starting CLZ use, when treating patients with refractory psychosis, who are alcohol drinkers and carriers of this genetic variant in order to prevent CLZ-related adverse reactions. Nevertheless, our findings should be replicated in larger samples.

Unique Effects of Clozapine: A Pharmacological Perspective

Schizophrenia is a heterogenous and severe neuropsychiatric disorder that affects nearly 1% of the population worldwide. Antipsychotic drugs are the mainstay of treatment, but not all patients with schizophrenia respond to treatment with these agents. Clozapine, the first atypical antipsychotic, is a highly effective medication for patients with schizophrenia who do not respond to other antipsychotics. Although clozapine tends not to produce extrapyramidal symptoms, other side effects of the drug (e.g., agranulocytosis, myocarditis, seizures) limit its widespread use. This chapter reviews clozapine's unique clinical effects and unusual pharmacological profile. In addition to its effects in treatment-resistant schizophrenia, clozapine has been shown to decrease suicidality, which occurs at an increased rate in patients with schizophrenia. Still preliminary, but consistent data, also suggest that clozapine limits substance use in these patients, an important effect since substance use disorders are common in patients with schizophrenia and are associated with a poor outcome, including an increased risk for suicide and poor response to treatment. We have suggested, from animal studies, that clozapine's apparent ability to limit substance use may occur through its actions as a weak dopamine D2 receptor antagonist, a potent norepinephrine α-2 receptor antagonist and a norepinephrine reuptake inhibitor. Using animal models, we have built combinations of agents toward creation of safer clozapine-like drugs to reduce substance use in these patients. Future research into the mechanisms of action of clozapine toward the development of safe clozapine-like agents is of great public health importance.

An open-label pilot study of quetiapine plus mirtazapine for heavy drinkers with alcohol use disorder

Animal research suggests that medications that produce a weak dopamine D2 receptor blockade and potentiate noradrenergic activity may decrease alcohol drinking. In an open-label pilot study of subjects with alcohol dependence, we tested whether the combination of quetiapine, a weak dopamine D2 receptor antagonist, whose primary metabolite, desalkylquetiapine, is a norepinephrine reuptake inhibitor, and mirtazapine, a potent α2 norepinephrine receptor antagonist, would decrease alcohol drinking and craving. Twenty very heavy drinkers with alcohol dependence entered a trial of 8 weeks of treatment with quetiapine followed by 8 weeks of treatment with a combination of quetiapine plus mirtazapine. Alcohol use was assessed weekly with a Timeline Follow-Back interview and craving with the Penn Alcohol Craving Scale. Among the 11 completers, subjects reported improved outcomes in the quetiapine plus mirtazapine period compared to the quetiapine alone period: fewer very heavy drinking days per week (1.3 [SD = 2.4] vs. 2.1 [SD = 2.8]; t = 2.3, df = 10, p = 0.04); fewer total number of drinks per week (39.7 [SD = 61.6] vs. 53.4 [SD = 65.0]; t = 2.8, df = 10, p = 0.02); and lower craving scores (2.5 [SD = 1.4] vs. 3.2 [SD = 1.2]; t = 2.4, df = 10, p = 0.04). All subjects reported at least one adverse event; 72.7% reported somnolence. In this open-label pilot study, treatment with quetiapine plus mirtazapine was associated with a decrease in alcohol drinking and craving. These findings are consistent with our previous work in animal models of alcohol use disorders and suggest that further study of medications or combinations of medications with this pharmacologic profile is warranted.

Effects of iloperidone, combined with desipramine, on alcohol drinking in the Syrian golden hamster

Alcohol use disorder in patients with schizophrenia dramatically worsens their clinical course, and few treatment options are available. Clozapine appears to reduce alcohol use in these patients, but its toxicity limits its use. To create a safer clozapine-like drug, we tested whether the antipsychotic iloperidone, a drug that combines a weak dopamine D2 receptor blockade and a potent norepinephrine alpha-2 receptor blockade would reduce alcohol drinking, and whether its effect on alcohol drinking could be increased if combined with an agent to facilitate norepinephrine activity. Syrian golden hamsters (useful animal model for screening drugs that reduce alcohol drinking in patients with schizophrenia) were given free access to water and alcohol (15% v/v) until stable drinking was established. Animals (n = 6-7/group), matched according to alcohol intake, were treated daily with each drug (iloperidone; clozapine; haloperidol; desipramine [norepinephrine reuptake inhibitor]; with idazoxan [norepinephrine alpha-2 receptor antagonist]) or with a two-drug (iloperidone + desipramine; iloperidone + idazoxan) combination for 14 days. Moderate doses of iloperidone (1-5 mg/kg) significantly reduced alcohol drinking (p < 0.05) in the hamster, whereas higher doses (10-20 mg/kg) did not. In addition, 5 mg/kg of iloperidone reduced alcohol drinking to the same extent as clozapine (8 mg/kg), whereas haloperidol (0.2 mg/kg) did not. Moreover, iloperidone's effects were enhanced via the addition of desipramine (3 mg/kg), but not idazoxan (1.5/3 mg/kg). In this animal model, iloperidone decreases alcohol drinking as effectively as clozapine, and desipramine appears to amplify this effect. The data suggest that iloperidone, alone or in combination with desipramine, should be tested in patients with schizophrenia and alcohol use disorder.

Desipramine enhances the ability of paliperidone to decrease alcohol drinking

Alcohol use disorder commonly occurs in patients with schizophrenia and dramatically worsens their course. The atypical antipsychotic clozapine has been associated with reduced drinking in these patients, but its toxicity reduces its use. We have attempted to create a clozapine-like drug by combining agents that capture components of clozapine's pharmacologic action, including its weak dopamine D2 blockade and noradrenergic modulation. The current study assessed whether paliperidone, a dopamine D2 receptor and adrenergic alpha-2 receptor antagonist like clozapine, would attenuate alcohol drinking in the alcohol-preferring P rat and the Syrian golden hamster, and whether desipramine, a norepinephrine reuptake inhibitor, would potentiate the ability of paliperidone to attenuate alcohol drinking in the P rat and the Syrian golden hamster. Daily subcutaneous injections of paliperidone (5 mg/kg for the rat; 1 mg/kg for the hamster) over 20 days slightly and transiently attenuated initiation of alcohol consumption in both animals. Desipramine (3 mg/kg) or lower doses of paliperidone alone did not affect alcohol drinking. However, the combination of desipramine (3 mg/kg) and paliperidone essentially prevented initiation of alcohol drinking and acquisition of alcohol preference in the P rat (2.5 or 5 mg/kg), and almost as dramatically suppressed chronic alcohol intake and alcohol preference in the hamster (2.5 mg/kg). Taken together, the current data suggest that (1) the desipramine and paliperidone combination attenuates alcohol drinking in a synergistic manner, and (2) desipramine and paliperidone may serve as an effective new treatment for alcohol use disorder in patients with schizophrenia.