## **Core Concept**
Obsessive Compulsive Disorder (OCD) is an anxiety disorder characterized by recurrent, intrusive thoughts (obsessions) and repetitive behaviors (compulsions). The first-line treatment for OCD typically involves medications that target the serotonin system.

## **Why the Correct Answer is Right**
The correct answer, **C. Fluoxetine**, is a selective serotonin reuptake inhibitor (SSRI). SSRIs are considered the first-line treatment for OCD due to their efficacy in reducing symptoms of obsessions and compulsions. Fluoxetine works by inhibiting the reuptake of serotonin (5-HT) in the brain, thereby increasing the availability of serotonin in the synaptic cleft. This action helps to alleviate OCD symptoms. Other SSRIs like sertraline, paroxetine, and citalopram are also effective.

## **Why Each Wrong Option is Incorrect**
- **Option A:** is not specified, but if it were a typical antipsychotic or a different class of medication not primarily used for OCD, it would be incorrect because it's not the first-line treatment.
- **Option B:** is not specified, but if it were a benzodiazepine or another anxiolytic not primarily used for OCD, it would be incorrect because these do not target the underlying pathology of OCD effectively.
- **Option D:** is not specified, but if it were a different class of medication such as a tricyclic antidepressant (which can be used but is not first-line due to side effects) or another type of medication not primarily indicated for OCD, it would be incorrect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that for OCD, SSRIs are the first-line pharmacological treatment. Among these, **fluoxetine, sertraline, and paroxetine** are commonly used. It's also crucial to note that patients with OCD may require higher doses and longer treatment duration compared to depression.

## **Correct Answer: C. Fluoxetine**