Seroquel (quetiapine) is not classified as a controlled substance under the U.S. Controlled Substances Act, but it is a prescription-only antipsychotic with known risks of side effects, misuse, and withdrawal if stopped abruptly. Seroquel is a prescription medicine used to treat the symptoms of Schizophrenia, Bipolar I Disorder, Mania; Bipolar Disorder, Depressive Episodes; Bipolar I Disorder, Maintenance; and Major Depressive Disorder. Seroquel may be used alone or with other medications. Find patient medical information for Quetiapine (Seroquel) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings Quetiapine is used alone or together with other medicines to treat bipolar disorder (depressive and manic episodes) and schizophrenia. Quetiapine extended-release tablet is also used together with other antidepressants to treat major depressive disorder. Seroquel is used to treat the symptoms of schizophrenia, bipolar disorder and major depressive disorder. Learn about side effects, interactions and indications. Quetiapine (Seroquel) is an antipsychotic that treats schizophrenia and bipolar disorder. It balances dopamine and serotonin in your brain. Quetiapine is one of only two antipsychotics (the other is cariprazine) that produce equal efficacy as standalone therapies for mixed manic-depressive mood swings as they do in combination with an SSRI antidepressant.