In the majority of cases of bipolar disorder, manic episodes are usually brief 
and typically responsive to currently available psychopharmacological agents. In 
contrast, depressive manifestations are more prevalent and persistent, and can 
present as major depressive/mixed episodes or residual interepisode symptoms. 
The depressive phase is often associated with other neuropsychiatric conditions, 
such as anxiety spectrum disorders, substance use disorders, stressor-related 
disorders, and eating disorders. It is viewed as a systemic disease with 
associated ailments such as metabolic syndrome, diabetes mellitus, and 
cardiovascular disease. There is an increased rate of mortality not only from 
suicide, but also from concomitant physical illness. This scenario is made worse 
by the fact that depressive symptoms, which represent the main disease burden, 
are often refractory to existing psychotropic drugs. As such, there is a 
pressing need for novel agents that are efficacious in acute depressive 
exacerbations, and also have applicable value in preventing recurrent episodes. 
The rationale of the present review is to delineate the pharmacotherapy of the 
depressive phase of bipolar disorder with medications for which there is 
evidence in the form of observational, open-label, or double-blind randomized 
controlled studies. In the treatment of acute bipolar depression in adults, a 
comprehensive appraisal of the extant literature reveals that among mood 
stabilizers, the most robust proof of efficacy exists for divalproex sodium; 
while atypical antipsychotics, which include olanzapine, quetiapine, lurasidone, 
and cariprazine, are also effective, as demonstrated in controlled trials.