Which medication is most helpful in the treatment of obsessive-compulsive disorder?

• A. Trifluoperazine.
• B. Chlordiazepoxide.
• C. Buspirone.
• D. Fluoxetine.

Answer: (D)

Obsessive-compulsive disorder responds best to medications that boost serotonin signaling in the brain. SSRIs increase serotonin availability and reliably reduce the intrusive thoughts (obsessions) and repetitive behaviors (compulsions) over several weeks. Fluoxetine is an SSRI proven to be effective for OCD, and for this condition it is often needed at higher doses than those used for depression. The other options don’t target OCD’s serotonin-driven cycle: trifluoperazine is a dopamine-blocking antipsychotic with broader motor side effects and isn’t specifically effective for OCD symptoms; chlordiazepoxide is a benzodiazepine that mainly helps general anxiety short-term without addressing obsessive-compulsive patterns; buspirone helps generalized anxiety but has limited impact on OCD. Thus, fluoxetine best fits the treatment of OCD among these choices.