Major depression is a common and disabling disorder with far-reaching social and economic implications. Nonetheless, major depression is treatable by one of the many currently available antidepressants with response rates of approximately 65-70%. Treatment of depression has improved in recent years because of the availability of effective and well-tolerated antidepressants, such as the selective serotonin reuptake inhibitors (SSRIs). The currently available antidepressants are generally equally effective and are distinguished primarily by side-effect profiles. The side effects of tricyclic antidepressants (TCAs) are attributed to their nonspecific interaction with cholinergic, histaminergic, serotonergic, and dopaminergic receptors in the central nervous system. The secondary amine TCAs, nortriptyline and desipramine, are preferred among the TCAs because of a more favorable side-effect profile. The TCAs are cardiotoxic, and overdoses are frequently fatal. Adverse effects, including potentially fatal drug and food interactions, limit the use of the monoamine oxidase inhibitors (MAOIs); however, these agents have a role in the treatment of depression with comorbid anxiety, refractory depression, atypical depression, and bulimia. The SSRIs possess a class side-effect profile of headache, nausea, and sexual dysfunction. Individual differences in side effects may distinguish fluoxetine (nervousness, restlessness), sertraline (diarrhea, loose stools), and paroxetine (dry mouth). The SSRIs all inhibit certain cytochrome P450 isoenzymes involved in the metabolism of drugs, such as the TCAs, and each SSRI has been reported to increase plasma concentrations of concomitantly administered TCAs. Bupropion therapy is associated with a risk of seizure development, which can be minimized by multiple daily doses. Trazodone is sedating and can rarely cause priapism. The related compound, nefazodone, does not cause sexual dysfunction or priapism, but is associated with sedation. Venlafaxine, a recently available antidepressant that appears to have efficacy in treatment-refractory depression, may cause nausea that requires gradual upward dosage titration. Higher doses of venlafaxine may also cause elevations in blood pressure, heart rate, and serum cholesterol. As more is learned about the pathophysiology of depression, even more specific and well-tolerated antidepressants will be developed.
