Paroxetine is a prescription medication classified as a selective serotonin reuptake inhibitor (SSRI). It is primarily used to treat conditions such as depression, anxiety disorders, obsessive-compulsive disorder, and post-traumatic stress disorder. Paroxetine works by increasing the levels of serotonin in the brain, which can help improve mood and reduce anxiety. Common side effects may include nausea, drowsiness, and sexual dysfunction.