Which of the following SSRIs is commonly used to treat panic disorder, OCD, PTSD, and social phobia?

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) that is often prescribed for a variety of anxiety and mood disorders, including panic disorder, obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and social phobia. It works by increasing serotonin levels in the brain, which can help to stabilize mood and reduce anxiety symptoms. Its efficacy in treating these conditions has been well-documented, making it a commonly chosen medication in clinical settings for the management of these disorders.

Other options listed, such as clomipramine and benzodiazepines like Valium, are used in the treatment of anxiety and panic disorders but are not classified as SSRIs. Clomipramine, while effective for OCD, is a tricyclic antidepressant rather than an SSRI. Additionally, medications like Valium and thiopental are primarily used for sedation and anxiety relief in different contexts and do not target the same conditions as effectively or specifically as fluoxetine does. Thus, fluoxetine stands out as the most suitable option for treating the disorders mentioned in the question.