Current pharmacological treatments for depression prove unsatisfactory efficacy with a proportion of subjects demonstrating treatment-resistant depression (TRD). The observation applies both to major depressive disorder (MDD) as well as bipolar I depression. There is growing evidence that the glutamatergic system plays a role in the pathophysiology and treatment of depression. Discovery of rapid, although transient antidepressant effect of ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist used in a single sub-anaesthetic intravenous dose in unipolar, bipolar and treatment-resistant patients provides evidence for a glutamatergic antidepressant. Subsequent studies confirmed this effect in repeated doses. Further research demonstrated that repeated ketamine infusions result in sustainable antidepressant effect with both, twice-weekly and thrice-weekly administration schedules. However, the worsening of depression may occur after infusions are completed. Given the risk of relapses, there is a definite need for the development of new strategies to maintain the beneficial effects of ketamine treatment. In the present study, the investigators aim to openly assess the safety, tolerability, and effectiveness of repeated, individually tailored IV, nasal spray and oral ketamine for treatment-resistant mood disorders. The investigators intend to explore questions regarding optimal dose, treatment frequency and duration.
