Effect of 5-HT2A receptor antagonism on levels of D2/3 receptor occupancy and adverse behavioral side-effects induced by haloperidol: a SPECT imaging study in the rat

Withdrawal syndrome after antipsychotics discontinuation: an analysis of the WHO database of spontaneous reports (Vigibase) between 2000 and 2022

RATIONALE

Withdrawal syndrome (WDS) has been described after discontinuation of antipsychotics. WDS could be the consequence of an over-activation of the dopaminergic pathway. Antipsychotics with a higher affinity for dopamine D2 receptors could be associated with a higher risk of WDS. This study aims to address this statement and evaluate the risk difference for withdrawal syndrome between antipsychotics based on pharmacovigilance data.

METHODS

We collected individual reports registered in Vigibase® between 01/01/2000 and 31/12/2022 of patients treated with antipsychotics and who had presented WDS. A disproportionality analysis was performed to evaluate the risk of reporting WDS with each antipsychotic compared to all other antipsychotics. We performed a correlation analysis to assess the correlation between the risk of reporting WDS for each antipsychotic in relation with their pKi for D2 and 5HT2A receptors.

RESULTS

The most frequent psychiatric withdrawal symptoms after antipsychotic discontinuation were insomnia, anxiety and depression. Tremor, headache and dizziness were among the most frequently reported neurologic withdrawal symptoms. Tiotixene had the highest risk of reporting WDS (ROR 7.08; 95%CI 3.49 - 14.35) followed by pimozide (ROR 4.35; 95%CI 1.93 - 9.77), quetiapine (ROR 4.24; 95%CI 3.87 - 4.64), thioridazine (ROR 4.17; 95%CI 2.50-6.98) and ziprasidone (ROR 2.98; 95%CI 2.41-3.67). We found a poor correlation between D2/5HT2A binding affinity and the risk of reporting withdrawal syndrome (R2 = 0,094).

CONCLUSION

Our results suggest that there might be a risk difference for WDS between antipsychotics. Tiotixene, pimozide and quetiapine were associated with a higher risk of reporting a WDS whereas this risk was lower with chlorpromazine, clozapine and fluphenazine. We could not address the issue of withdrawal psychosis, withdrawal dyskinesia, rebound psychosis or supersensitivity psychosis due to the lack of specific WHO medDRA coded terms to identify potential cases.

Discovery of new chemotypes of dual 5-HT2A/D2 receptor antagonists with a strategy of drug design methodologies

Aim: Through the application of structure- and ligand-based methods, the authors aimed to create an integrative approach to developing a computational protocol for the rational drug design of potent dual 5-HT_2A/D₂ receptor antagonists without off-target activities on H₁ receptors. Materials & methods: Molecular dynamics and virtual docking methods were used to identify key interactions of the structurally diverse antagonists in the binding sites of the studied targets, and to generate their bioactive conformations for further 3D-quantitative structure-activity relationship modeling. Results & conclusion: Toward the goal of finding multi-potent drugs with a more effective and safer profile, the obtained results led to the design of a new set of dual antagonists and opened a new perspective on the therapy for complex brain diseases.

The Role of G Protein-Coupled Receptors (GPCRs) and Calcium Signaling in Schizophrenia. Focus on GPCRs Activated by Neurotransmitters and Chemokines

Schizophrenia is a common debilitating disease characterized by continuous or relapsing episodes of psychosis. Although the molecular mechanisms underlying this psychiatric illness remain incompletely understood, a growing body of clinical, pharmacological, and genetic evidence suggests that G protein-coupled receptors (GPCRs) play a critical role in disease development, progression, and treatment. This pivotal role is further highlighted by the fact that GPCRs are the most common targets for antipsychotic drugs. The GPCRs activation evokes slow synaptic transmission through several downstream pathways, many of them engaging intracellular Ca²⁺ mobilization. Dysfunctions of the neurotransmitter systems involving the action of GPCRs in the frontal and limbic-related regions are likely to underly the complex picture that includes the whole spectrum of positive and negative schizophrenia symptoms. Therefore, the progress in our understanding of GPCRs function in the control of brain cognitive functions is expected to open new avenues for selective drug development. In this paper, we review and synthesize the recent data regarding the contribution of neurotransmitter-GPCRs signaling to schizophrenia symptomology.