quetiapine fumarate + selective serotonin reuptake inhibitor

Quetiapine fumarate + selective serotonin reuptake inhibitor is a combination therapy involving the atypical antipsychotic *quetiapine fumarate* and a drug from the *selective serotonin reuptake inhibitor* (SSRI) class. Quetiapine is a dibenzothiazepine derivative that acts mainly as an antagonist at several neurotransmitter receptors, including *serotonin 5-HT2A*, *dopamine D1 and D2*, *histamine H1*, and *adrenergic α1 and α2* receptors, with a much higher affinity for 5-HT2A than D2 receptors[1][2][3][4]. SSRIs, such as paroxetine, fluoxetine, sertraline, citalopram, or escitalopram, inhibit the presynaptic reuptake of serotonin, thereby increasing serotonergic activity in the central nervous system. The combination is used adjunctively (add-on therapy) primarily in **major depressive disorder** (MDD) and **bipolar depression** to enhance antidepressant response or management of treatment-resistant depression. Clinical studies have shown improved outcomes for depression and anxiety symptoms with this combination but a higher rate of adverse effects, including extrapyramidal symptoms, sedation, metabolic changes, and increased risk of certain events in older adults[2][3]. There is no single marketed fixed-dose product of this combination; the individual drugs are administered together.