Tolerability and safety: essentials in antidepressant pharmacotherapy.

Current antidepressants achieve similar efficacy, with 60% to 80% of patients responding adequately. Clinical response is gradual, and differential response factors are difficult to discern. However, side effect profiles and toxicity vary substantially, so the choice of medication depends primarily on tolerability and safety. Dry mouth is prevalent with tricyclic antidepressants (TCAs), whereas nausea occurs more frequently with a serotonin selective reuptake inhibitor (SSRI). Long-term unwanted effects tend not to be a major problem, with a dropout rate of approximately 5% due to side effects. The relationship between suicidality and antidepressants remains under debate. Many TCAs are highly toxic in overdose whereas the SSRIs appear much safer. Nefazodone is a unique antidepressant with demonstrated efficacy. It is different from other antidepressants because of its two actions in the serotonin system, moderate serotonin selective reuptake blocking properties and direct 5-HT2 antagonism, which also can enhance 5-HT1 neurotransmission. The 5-HT2 antagonist properties may limit serotonin-mediated effects and, as a result, nefazodone may be more anxiolytic than other antidepressants. Nefazodone also moderately inhibits norepinephrine reuptake and blocks alpha 1-adrenergic receptors. The data base on the safety of nefazodone currently comprises approximately 3,500 patients from all research trials, which include controlled trials that allow comparisons of nefazodone treatment with several hundred patients taking TCAs or SSRIs and nearly 900 patients receiving placebo. The most frequent adverse experiences with nefazodone as compared with placebo treatment are nausea (21% vs. 14%), somnolence (19% vs. 13%), dry mouth (19% vs. 13%), dizziness (12% vs. 6%), constipation (11% vs. 7%), asthenia (11% vs. 6%), light-headedness (10% vs. 4%), and amblyopia (blurred vision; 6% vs. 3%). Approximately 12% of nefazodone-treated patients dropped out because of adverse experiences, as compared with 7.4% on placebo, 10.4% on SSRIs, but 21.8% on imipramine after short-term exposure in placebo-controlled trials. Long-term safety data include nearly 1,300 patients; nefazodone was well tolerated. Nefazodone was evaluated in normal subjects by the author and was found to produce less impairment than imipramine and was less likely to interact with alcohol. In summary, nefazodone has a favorable adverse-event profile as compared with the TCAs and a rather different one from the SSRIs. It appears to be safe and well tolerated after both acute and long-term use.