Selective serotonin reuptake inhibitors (SSRIs) are used to treat depression, anxiety, and obsessive-compulsive disorder (OCD). They also have other uses, such as treating panic disorder and post-traumatic stress disorder (PTSD). SSRIs work by increasing the levels of serotonin, a chemical in your brain that helps improve mood. These medications are usually taken as oral pills. Examples include fluoxetine (Prozac), escitalopram (Lexapro), sertraline (Zoloft), citalopram (Celexa), paroxetine (Paxil), and vilazodone (Viibryd). You can talk to your healthcare provider to find the one that best fits your needs.