Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions.
SSRIs primarily work by blocking serotonin reabsorption (reuptake) via the serotonin transporter, leading to gradual changes in brain signaling and receptor regulation, with some also interacting with sigma-1 receptors, particularly fluvoxamine, which may contribute to cognitive effects. Marketed SSRIs include six main antidepressants—citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline—and dapoxetine, which is indicated for premature ejaculation. Fluoxetine has been approved for veterinary use in the treatment of canine separation anxiety.