The following drugs are established treatments for bipolar depression:
Lithium
Lithium plus antidepressants
Lamotrigine
Olanzapine and fluoxetine
Quetiapine
There are many groups and types of antidepressants, too many to list in completeness here. Those commonly prescribed today are the SSRIs (selective serotonin reuptake inhibitors) and include fluoxetine, paroxetine and citalopram.
They work by altering the balance of the brain chemical serotonin in parts of the brain. Antidepressants alone without a mood stabiliser are avoided in bipolar depression as there is a risk of inducing a hypomania or rapid cycling.
Other treatments, but with less scientific evidence for effectiveness in bipolar depression, include valproate, carbamazepine, aripiprazole and gabapentin