ISSUE:Ketamine induces rapid-onset and short-duration improvement in depressive and suicidal symptoms in both treatment-resistant unipolar depression and bipolar depression, and also reduces chronic pain after short intravenous infusions. In order to develop long-acting oral agents with the same clinical effects, the pharmacologic mechanism of action must be understood, and the leading hypotheses are discussed here.

Depressive symptoms and episodes dominate the long-term course of bipolar disorder and are associated with high levels of disability and an increased risk of suicide. However, the treatment of bipolar depression has been poorly investigated in comparison with that of manic episodes and unipolar major depressive disorder. The goal of treatment in bipolar depression is not only to achieve full remission of acute symptoms, but also to avoid long-term mood destabilization and to prevent relapses. A depressive presentation of bipolar disorder may often delay the appropriate management and, thus, worsen the long-term outcome. In these cases, an accurate screening for diagnostic indicators of a possible bipolar course of the illness should guide the therapeutic choices, and lead to prognostic improvement. Antidepressant use is still the most controversial issue in the treatment of bipolar depression. Despite inconclusive evidence of efficacy and tolerability, this class of agents is commonly prescribed in acute and long-term treatment, often in combination with mood stabilizers. In this article, we review available treatment options for bipolar depression, and we shall provide some suggestions for the management of the different presentations of depression in the course of bipolar disorder.

Depression is a common psychiatric condition characterized by affective, cognitive, psychomotor, and neurovegetative symptoms that interfere with a person's ability to work, study, deal with interpersonal relationships, and enjoy once-pleasurable activities. After the serendipitous discovery of the first antidepressants, for years the only pharmacodynamic mechanisms explored in the search of novel antidepressants were those related to the 3 main monoamines: serotonin, norepinephrine, and dopamine. New-generation monoaminergic antidepressants, such as selective-serotonin and dual-acting serotonin/norepinephrine reuptake inhibitors, improved treatment and quality of life of depressed patients. Nevertheless, there are still important clinical limitations: the long latency of onset of the antidepressant action; side effects, which can lead to early discontinuation; low rate of response; and high rate of relapse/recurrence. Therefore, in the last several years, the focus of research has moved from monoamines toward other molecular mechanisms, including glutamatergic (Glu) neurotransmission. This review provides a comprehensive overview of the current knowledge on the Glu system and on its relationships with mood disorders. Up to now, N-methyl-D-aspartate (NMDA) receptor antagonists, in particular ketamine, provided the most promising results in preclinical studies and produced a consistent and rapid, although transient, antidepressant effect with a good tolerability profile in humans. Although data are encouraging, more double-blind, randomized, placebo-controlled trials are needed to clarify the real potentiality of ketamine, and of the other Glu modulators, in the treatment of unipolar and bipolar depression.

In this article, we examined evidence for the acute treatment of depression in bipolar I disorder, focusing on double-blind, placebo-controlled studies with a definite primary outcome measure and published in peer review journals. Quetiapine and olanzapine/fluoxetine are currently approved by the FDA for the treatment of bipolar depression, and a number of additional agents (including other atypical antipsychotics, mood stabilizers, antidepressants, and novel compounds) have been studied with varying degrees of efficacy. The medication with the most evidence for efficacy in bipolar depression is quetiapine, with five studies showing positive efficacy compared to placebo. In contrast, five studies of lamotrigine were negative, although meta-analyses of the pooled have found some treatment effects. Two studies of olanzapine and olanzapine/fluoxetine and three small studies of divalproex showed significant efficacy in treating bipolar depression. Two studies of aripiprazole found no differences compared to placebo. Early research on lithium in bipolar depression had significant methodological flaws, and only one study of lithium met our primary search criteria. To better understand the role of antidepressants, we also examined studies of antidepressants as adjunctive treatment of bipolar depression in participants taking mood stabilizers or atypical antipsychotics. These studies reported mixed results for a variety of antidepressants, but the majority found no differences compared to placebo. Other studies of adjunctive treatment were also discussed. There has been one positive adjunctive study each of lamotrigine, omega-3 fatty acids, modafinil, and armodafinil, while there was one negative trial each of omega-3 fatty acids, ziprasidone, and levetiracetam.

Children and adolescents with bipolar disorder may have depression as the presenting mood state. It is important for clinicians to distinguish between unipolar and bipolar depression in youth. Depressive episodes are common during the course of bipolar illness in children and adolescents. Evidence-based treatments are needed to guide clinicians’ treatment decisions for youth with bipolar depression. This article reviews the prevalence, diagnosis, course, and treatment of bipolar depression in youth, and emphasizes the need for large, controlled treatment studies in the pediatric population.