Antidepressant pharmacotherapy Although expansion of antidepressant treatment in the USA has been substantial, low rates persist in racial and ethnic minorities. Antidepressants were the most commonly prescribed class of drugs in office-based and hospital outpatient-based medical practice in 2005.110 The table lists the antidepressants that have been approved by the US Food and Drug Administration (FDA), and the proposed mechanisms of action for the various classes of antidepressants. A complete assessment of their use can be found in the American Psychiatric Association guidelines for depression.111