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Depression affects over 121 million people annually worldwide. Relatively low remission rates among depressive patients enforce the search for new therapeutic solutions and an urgent need to develop faster-acting antidepressants with a different mechanism of action occurs. The pathomechanism of depression postulated by the monoamine hypothesis is limited. The results of abnormalities in glutamate and γ-aminobutyric acid (GABA) systems in the brains of people with mood disorders allowed to develop new theories regarding pathophysiology of these disorders. Glutamatergic transmission is influenced by magnesium and ketamine through glutamatergic N-methyl-D-aspartate receptor (NMDAR) antagonistic effects. Magnesium and ketamine have a common mechanism of action in the treatment of depression: an increase in GluN2B (NMDAR subunit) expression is related to the administration of both of the agents, as well as inhibition of phosphorylation of eEF2 (eukaryotic elongation factor 2) in cell culture and increase of the expression of BDNF in the hippocampus. Combination of ketamine and magnesium in a normal magnesium level presents a superadditive effect in depression treatment. Analysed substances affect the GABAergic system and have anti-inflammatory effects, which is correlated with their antidepressant effect. The synergistic interaction between the pharmacodynamic activity of magnesium and ketamine may be of particular importance for patients with mood disorders. Further research is needed to determine the relationship between magnesium levels and ketamine treatment response mainly in the attempt to establish if the magnesium supplementation can change ketamine treatment response time or present superadditive effect.

Major depressive disorder is one of the most important psychiatric issues worldwide, with important prevalence of treatmentresistant depression (TRD). Non-monoaminergic agents are currently in the spotlight. Objective was to explore for information about mechanisms of action of ketamine, its connections with copper and possible importance for TRD treatment. There are at least few possible pathways for ketamine action in depression in which copper and other divalent ions may show a vital role. There is urgent need for more studies to gather information about correlation between ketamine, copper and antidepressive features of these agents.

Bipolar depression (BD) is among the most severe psychiatric disorders. A significant number of patients do not achieve an entirely symptom-free state and experience residual sub-syndromal depression. Most of the treatment options approved for bipolar depression give no rapid symptom improvement. Ketamine is an anaesthetic medication that acts as an antagonist of the NMDA receptor and has antidepressant potential. Due to its unique way of action, ketamine seems to be crucial for the treatment of anhedonia. This review paper aims to provide an overview of the efficacy of ketamine infusions in bipolar depression with a focus on anhedonia Literature suggests that intravenous ketamine 0.5 mg/kg over 40min weekly could be useful in the treatment of bipolar depression with prominent anhedonia, but there is still a small number of studies that examine the efficacy of ketamine infusions in BD. In conclusion, ketamine should be considered as a valuable treatment option for patients with BD and anhedonia.

Suicidal ideations or attempts in patients with major depressive disorder (MDD) are emergent conditions that require immediate treatment. Numerous therapeutic interventions to reduce suicide risk in psychiatric disorders are effective in long-term suicide prevention, but there is necessity of sufficient, rapid pharmacological treatment of suicidal risk in MDD. Ketamine, an N-methyl-D-aspartate (NMDA) antagonist, has been reported to have rapid antidepressant effect. Depressive symptoms, anxiety, hopelessness, suicidal ideation had decreased within hours after ketamine infusion. Ketamine’s rapid symptoms relief and reduction of suicide thoughts has aroused growing interests in psychiatric association.

Major depression is one of the most frequent psychiatric conditions. Despite many available treatment methods, more than 30% of patients do not achieve remission, even after trying several antidepressants and augmentation strategies. S-enantiomer of ketamine, well-known anesthetic and analgesic, has been recently approved by Food and Drug Administration in the intranasal form as a new generation antidepressant. However, the mechanism in which ketamine reduces depressive symptoms in treatment-resistant depression patients is still not completely understood. There are several theories explaining how ketamine might reduce depressive symptoms, which have been described in detail; one of them is immunomodulatory effect of ketamine, according to the inflammatory theory of depression. In the review authors present and summarize studies showing ketamine effect on human immune system ex vivo and in vitro, including changes in cytokine levels, number, ratio and activity of various immune cell population and the correlation with clinical improvement in depressive symptoms. Most of the results confirm the anti-inflammatory effect of ketamine. There are only a few studies in the population of patients suffering from depression receiving ketamine, focused on correlation between immunological changes and clinical outcome of the therapy; further studies of that area are neccesary for understanding the immunomodulatory effect of ketamine in depression.