Understanding the Efficacy and Mechanism of Action of a Dextromethorphan-Bupropion Combination: Where Does It Fit in the NMDA Versus mu-Opioid Story?

Profiling the combination of bupropion and dextromethorphan as a treatment option for major depressive disorder

INTRODUCTION

Major Depressive Disorder (MDD) is a common mental health disorder marked by sadness, hopelessness, and anhedonia. Various therapies exist, but their effectiveness is limited. Dextromethorphan hydrobromide combined with bupropion hydrochloride (Auvelity®) is a recently approved alternative for treating this condition in adults.

AREAS COVERED

This review summarizes the neurobiology of major depression and delves into the pharmacology, efficacy, safety, and tolerability of dextromethorphan plus bupropion in adult patients. It is based on observational studies, clinical trials, and other secondary studies obtained through systematic literature searches.

EXPERT OPINION

The combination of bupropion and dextromethorphan as a new pharmacotherapy for mental health is an interesting addition to the treatment options that can be used for MDD. The combination can be used in a range of scenarios, including as a first line therapy, as a second option when a patient has failed to achieve remission with a serotonin targeting agent, and for treatment resistant depression. Further research for other indications, including addiction disorders, may provide exciting results. Although a new combination, clinicians will be very familiar with both agents, increasing their acceptability. This pharmacotherapy also may bring increased impetus for discovering other combinations that may have beneficial synergistic effects.

Ultra-overt therapy: a novel medical approach centered on patient consciousness

Within the realms of human and artificial intelligence, the concepts of consciousness and comprehension are fundamental distinctions. In the clinical sphere, patient awareness regarding medication and its physiological processes plays a crucial role in determining drug efficacy and outcomes. This article introduces a novel perspective on prescription practices termed "Ultra-Overt Therapy" (UOT). A review of current supporting evidence was conducted through a non-systematic search in PubMed and Google Scholar, focusing on concepts such as the "mind-body relationship," "placebo response," "neuroscience," and "complementary medicine." Our findings, rooted in the mechanisms of the "placebo effect," the intricacies of "intersubjective therapy," the potency of "interoceptive awareness," and other domains of medical science, suggest that UOT holds theoretical promise. Future research endeavors focusing on these areas may elucidate the global impact of this method on medical treatment and patient care.

The why, when, where, how, and so what of so-called rapidly acting antidepressants

Developing antidepressants that are not only more effective but are rapidly acting is the Holy Grail for psychiatry. We review multiple issues that arise in determining rapid responses in antidepressant trials. The current status of purportedly rapid acting agents is first reviewed. Then, a number of key questions/issues are addressed: Is there a unifying definition for rapid response across studies? Should rapid response criteria be based on required measurable effects on overall improvement? On specific symptoms such as psychomotor retardation, depressed mood, or anhedonia? In associated symptoms such as anxiety or insomnia? When should onset be considered rapid-by Day 3? Day7? Day 14? If there is a rapid response, for how long should the effects be maintained? Is maintenance of effect dependent on continuing the medication? Is rapid response associated with specific mechanisms of action? Do the mechanisms of action suggest possible risk for drug abuse? How important is rapid response really in an often chronic or recurrent depressive disorder? In which types of patients could rapid response be particularly important? What are the study design issues that need to be considered for assessing rapid response, including: selection of specific types of depressed patients, multiple doses of drug studied, designation of primary and secondary outcome measures, specific time points at which to determine efficacy, requirements for demonstrating durability, etc. A framework for approaching this complex area is developed for both researchers and clinicians.

Dextromethorphan-Bupropion for the Treatment of Depression: A Systematic Review of Efficacy and Safety in Clinical Trials

BACKGROUND

A significant proportion of adults with major depressive disorder (MDD) do not respond to treatments which are currently used in clinical practice such as first-generation monoamine-based antidepressants.

OBJECTIVES

The objective of this systematic review was to assess the efficacy, safety, and mechanisms of action of AXS-05, a combination of the NMDA-receptor antagonist dextromethorphan with bupropion, in adults with MDD.

METHODS

We searched PubMed, Embase, Google Scholar, and ClinicalTrials.gov for current studies reporting on efficacy and/or safety of AXS-05 in patients with MDD. The search terms included: "AXS-05" OR "dextromethorphan and bupropion" AND "depression". Studies from database inception to January 2023 were evaluated. Risk of bias was assessed using the Cochrane Risk of Bias tool.

RESULTS

The search yielded 54 studies of which 5 were included. All studies had low risk of bias. Depression severity, measured with the Montgomery-Åsberg Depression Rating Scale (MADRS) significantly decreased as early as 1-week post-treatment from baseline when compared to a placebo-controlled group (LS mean difference 2.2; 95% CI 0.6-3.9; p = 0.007) and at 2 weeks compared to an active control group (LS mean difference 4.7; 95% CI 0.6-8.8; p = 0.024). Treatment efficacy could be maintained for up to 12 months with mean MADRS score reduction of 23 points from baseline. Clinical remission and response rates also improved at week 1 and were maintained for 12 months. The treatment was well-tolerated, with some transient adverse events reported.

CONCLUSION

Current evidence suggests that the combination of dextromethorphan and bupropion is a well-tolerated, rapid-acting treatment option for adults with MDD. Initial success with AXS-05 supports the mechanistic role of glutamatergeric and sigma 1 signaling in the pathophysiology of MDD.

Advancements in Drug Repurposing: Examples in Psychiatric Medications

Because there are a limited number of animal models for psychiatric diseases that can be extrapolated to humans, drug repurposing has been actively pursued. This study was aimed at uncovering recent trends in drug repurposing approaches and new technologies that can predict efficacy on humans based on animal models used in psychiatric drug development. Psychiatric drugs that were approved by the FDA between 2002 and 2022 were listed, and the method of how the drug repurposing has been applied was analyzed. Drug repurposing has been increasingly applied to recently approved psychiatric drugs. The development concepts of psychiatric drugs that have been developed through drug repurposing over the past 20 years were found to be divided into six categories: new application exploration, reduction of side effects, improvement of symptom control, improvement of medication compliance, enhancement of drug efficacy, and reduction of drug-drug interactions. All repurposed drugs approved before 2016 used either prodrugs or active metabolites, while all drugs approved in 2021 and beyond used fixed-dose combinations with sophisticated ideas. SmartCube^®, which uses artificial intelligence to predict human drug efficacy from animal phenotypes, was developed and produced novel drugs that show clinical efficacy. Well-designed drug repurposing approaches and new technologies for predicting human drug efficacy based off of animal models would contribute to novel psychiatric drug development.

Improvement of depressive symptoms, after a suicide attempt, with dextromethorphan/bupropion combination treatment in a patient with treatment-resistant depression and psychiatric comorbidities

We admitted a 42-year-old patient with severe treatment-resistant depression and with psychiatric comorbidities. The patient attempted suicide 5 weeks after admission. Subsequently, we initiated dextromethorphan/bupropion based on prior evidence. As a result, the patient demonstrated an improvement in mood symptoms and a reduction in suicide risk, leading to her discharge.