How it works:
It blocks dopamine-2 receptors, especially at higher doses. This is how it works for schizophrenia. It also blocks serotonin-2A receptors, which increases dopamine release in certain brain areas. Also, this is a 5HT-1A partial agonist which is similar to certain other antidepressants and anxiety medications.
What makes it unique:
This is mainly used for illnesses other than depression. It is useful in treating schizophrenia, and bipolar disorder.
This medication is sedating. Prescribers try to use it off label to help people sleep better. It can also cause weight gain and metabolic side effects. The weight gain can lead to diabetes and high cholesterol. Additional side effects include neuroleptic malignant syndrome, tardive dyskinesia, leukopenia, cataracts and decreases in blood pressure in children.
This medication carries a risk of suicidal thinking and behavior in people age 24 and younger when used with an antidepressant medication.
How effective is it:
(1) A study compared adjunctive Quetiapine XR 150mg, 300mg, and placebo in 493 patients. MADRS depression scores decreased by 15.26 in the 150mg group, by 14.94 in the 300mg group and by 12.21 in the placebo group. More patients in the Quetiapine group withdrew due to side effects as compared to the placebo group. The most common side effects were dry mouth and somnolence.
(2) A study compared Quetiapine XR to another antidepressant medication, Duloxetine and to placebo. 612 patients with major depressive disorder were included in the study. Quetiapine XR 150mg, 300mg and Duloxetine 60mg were all more effective than placebo in reducing the MADRS depression scale. Both strengths of Quetiapine worked more quickly than Duloxetine.
I rarely see this medication prescribed purely for depression. It may be good for someone with high anxiety depression because of its sedating effects. It has a lot of other uses though and I see it used more for sleep, sedation, bipolar and schizophrenia. Using low doses for sedation and sleep is controversial because there are other sedating medications with fewer side effects. Pharmaceuticals should never be used as the sole treatment for mental illnesses. Therapy, exercise, meditation or other treatments should always accompany prescriptions.
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1. Bauer M, Pretorius H, Constant E, et al. Extended-release quetiapine as adjunct to an antidepressant in patients with major depressive disorder: results of a randomized, placebo-controlled, double-blind study. J Clin Psychiatry. 2009 Apr;70(4):540-9.
2. Cutler A, Montgomery S, Feifel D, et al. Extended release quetiapine fumarate monotherapy in major depressive disorder: a placebo- and duloxetine-controlled study. J Clin Psychiatry. 2009 Apr;70(4):526-39.