Objectives:
In the last decade several authors described a robust and clinically relevant alleviation of depressive symptoms after infusions of the uncompetitive N-methyl-D-aspartate (NMDA) glutamate receptor antagonist - ketamine. In the majority of published reports ketamine was administrated to patients with depression resistant to pharmacotherapy, but not to ECT. We present a series of 5 subjects suffering from multimodal treatment-resistant depression (including ECT or rTMS and various medications) treated with intravenous infusions of ketamine in a subanesthetic dose of 0.5 mg/kg in the naturalistic setting. To the best of our knowledge it is the first report on ketamine infusion in patient resistant to antidepressants and rTMS

Methods:
Two subjects have been diagnosed with with MDD, one with BD, two with severe depressive episode.The efficacy and possible adverse events were monitored using psychometric scales. Basic life parameters and ECG were observed.

Results:
Ketamine's infusions showed transient antidepressant efficacy.Improvement rate in our group was significant lower than in previously reported. Ketamine was generally well tolerated. We noted transient BP variations and appearance of mild and transient dissociative symptoms. Low early response rate may be correlated with resistance to previous multimodal treatment, high rate of somatization and anxiety comorbidity or heterogeneity of our group.

Conclusions:
Our findings do not support the use of ketamine infusions as the monotherapy in the subgroup of patients with multimodal treatment resistant depression.