Most of the evidence for the use of quetiapine to treat depression consists of short-term studies. That's why an FDA advisory committee in 2009 voted not to recommend it as a stand-alone treatment for depression, citing concerns about potential long-term risks in a large population, especially when safer drugs are available.
But the committee found enough evidence in two six-week trials to recommend quetiapine for limited use as an add-on drug for "resistant depression." Those studies found that depressed patients who took quetiapine plus an antidepressant had significantly reduced symptoms compared with those who received a placebo plus an antidepressant.
"The majority of experts on the committee acknowledged that it is effective," says Wayne K. Goodman, M.D., chairman of the committee and professor and chairman of the department of psychiatry at the Mount Sinai School of Medicine in New York. "But the overarching issue with this class of drugs is safety. Physicians should be aware of the side effects and try other options first."
What are the risks?
Metabolic problems. Chronic use may cause weight gain and increases in cholesterol, triglycerides, and blood-sugar levels, which are components of metabolic syndrome - a disorder that increases the risk of diabetes, heart disease, and stroke.
Movement disorders. Long-term use may lead to repetitive, uncontrollable movements of the face, tongue, and other parts of the body, and those symptoms (tardive dyskinesia) may be irreversible.
Sudden cardiac death. A large 2009 study, published in The New England Journal of Medicine, suggests that users of some atypical antipsychotics, including quetiapine, may have a greater risk of cardiac arrest than nonusers.
Black-box warning (the most serious kind issued by the FDA). Children, teenagers, and young adults who use quetiapine for depression may have an increased risk of suicidal thinking, and older adults undergoing treatment for dementia may have an increased risk of death.
Other safety concerns. Quetiapine may increase the risk of cataracts, reproductive and sexual problems, speech impairment, and hypothyroidism (underactive thyroid). It may temporarily lower your white blood cell count, increasing the risk for infection.
Common side effects. They include drowsiness, dizziness, dry mouth, constipation, and abdominal pain.