Samidorphan/olanzapine combination therapy for schizophrenia: Efficacy, tolerance and adverse outcomes of regimen, evidence-based review of clinical trials

Abstract

Introduction: Schizophrenia is a complex medical illness characterized by hallucinations, delusions, and cognitive issues. Olanzapine, a second-generation antipsychotic widely prescribed for schizophrenia has proven to be efficacious, however, its use is associated with major adverse effects such as weight gain, metabolic syndrome and diabetes mellitus. Recently, FDA approved a combination dose of olanzapine and samidorphan (OLZ/SAM) to mitigate the adverse outcomes associated with olanzapine use for the treatment of Schizophrenia.

Objectives: The approval of olanzapine/samidorphan combination by FDA in treatment of schizophrenia and bipolar I disorder has been a milestone. This article summarizes the clinical trials reporting the clinical efficacy and adverse effects of olanzapine/samidorphan combination along with their bias assessment.

Methods: Pubmed, science direct, Ovid SP and Google Scholar were comprehensively searched for data collection. Clinical trials reporting the efficacy and adverse outcomes of the OLZ/SAM regimen were included in the review and the Cochrane risk of bias assessment tool (RoB 2.0, version 2019) was used to assess the risk of bias in each study.

Results: Five trials employed the use of Positive and Negative Syndrome Scales (PANSS) and Clinical Global Impression-Severity (CGI-S) scale to assess the efficacy of OLZ/SAM. Overall, OLZ/SAM showed a significant reduction in PANSS total scores and CGI-S scores and might be a viable option for long-term treatment. The safety of combined therapy is assessed by trials considering the factors of ECG parameters, suicidal events, and movement disorders. Major adverse events included nervous system disorders, changes in blood chemistry, and metabolic or nutritional disorders, with worsening of adverse outcomes observed in a total of nineteen cases in six studies.

Conclusion: The FDA-approved drug recombination of OLZ/SAM for the treatment of schizophrenia revealed efficacious outcomes and was generally well tolerated by patients partaking in various trials. The potential of samidorphan in mimicking the efficacy of olanzapine while mitigating olanzapine-induced weight gain makes it a promising regimen for improving symptoms and health outcomes in schizophrenic patients.

Keywords: Olanzapine; Psychiatric; Research; Review; Samidorphan; Schizophrenia; Systematic.

Fig. 1

Pathomechanism of both the Olanzapine and Samidorphan drugs. Olanzapine blocks serotonin or dopamine D2 receptors to inhibit extra pyramidal activities. Samidorphan-an opioid receptor antagonist-gets metabolized in the liver and excreted through kidney in urine, contraindicated in patients with liver and kidney disease [[16], [17], [18]].

Fig. 2

Risk of bias of included studies assessed on Cochrane risk of the bias assessment tool.