quetiapine + selective serotonin reuptake inhibitor + venlafaxine

A combination therapy of **quetiapine**, one or more **selective serotonin reuptake inhibitor (SSRI)** antidepressants, and **venlafaxine** (a serotonin-norepinephrine reuptake inhibitor or SNRI). This regimen is used in psychiatry for treatment-resistant major depressive disorder (MDD) and other mood disorders, where symptoms persist after standard monotherapy. **Quetiapine** is an atypical antipsychotic that acts as an antagonist at serotonin 5-HT2A, 5-HT1A, dopamine D1 and D2, histamine H1, and adrenergic α1 and α2 receptors[3][4]. **SSRIs** block the serotonin transporter to increase synaptic serotonin, and **venlafaxine** inhibits reuptake of serotonin and norepinephrine. Studies show the addition of quetiapine to antidepressant therapy (SSRI and/or venlafaxine) may lead to improved depressive symptoms and anxiety, with evidence especially for add-on quetiapine in patients unresponsive to SSRIs or SNRIs alone[3]. However, the combination increases the likelihood of adverse effects, and careful monitoring is required due to potential drug interactions and additive side effects[1][3]. No combination drug product contains all three agents in a fixed formulation; treatment entails co-prescribing individual drugs.