A 28-year-old woman presents to the psychiatry clinic with a 3-year history of intrusive thoughts about harming her 2-year-old daughter. She reports recurrent images of the child being injured, which cause severe anxiety. To neutralize these thoughts, she checks on her daughter repeatedly (up to 50 times per day), counts objects in the house, and performs cleaning rituals lasting 2–3 hours daily. She recognizes these thoughts are irrational and distressing, and they significantly impair her occupational and social functioning. She denies any actual intent to harm her child. Mental status examination is otherwise normal. What is the most appropriate first-line pharmacological intervention?

Explanation

## Diagnosis and First-Line Treatment **Key Point:** This patient meets DSM-5 criteria for Obsessive-Compulsive Disorder (OCD). She has: - Obsessions (intrusive thoughts about harming her daughter) - Compulsions (checking, counting, cleaning rituals) - Recognition that thoughts are irrational (good insight) - Significant functional impairment ### First-Line Pharmacotherapy for OCD **High-Yield:** SSRIs are the gold-standard first-line agents for OCD. Fluoxetine at doses of 40–80 mg/day is FDA-approved and evidence-based for OCD treatment. | Agent | Dose for OCD | Evidence | Notes | |-------|--------------|----------|-------| | Fluoxetine | 40–80 mg/day | Excellent | FDA-approved; first-line | | Sertraline | 50–200 mg/day | Excellent | FDA-approved; first-line | | Paroxetine | 40–60 mg/day | Good | FDA-approved; first-line | | Clomipramine | 100–250 mg/day | Excellent | TCA; more side effects; second-line | **Clinical Pearl:** OCD typically requires higher SSRI doses and longer duration (8–12 weeks) compared to depression. Doses used for depression (e.g., fluoxetine 20 mg) are insufficient for OCD. **Mnemonic: SSRI-OCD** — SSRIs are the Selective Serotonin Reuptake Inhibitors of choice for Obsessive-Compulsive Disorder. ### Why SSRIs Work in OCD Enhanced serotonergic transmission reduces the hyperactivity in orbitofrontal-striatal circuits implicated in OCD pathophysiology. ### Adjunctive and Second-Line Options - **Cognitive-Behavioral Therapy (CBT)** with Exposure and Response Prevention (ERP) is equally effective and should be offered concurrently or as monotherapy if patient declines medication. - **Augmentation strategies** (if SSRI monotherapy fails after 8–12 weeks at adequate dose): - Antipsychotics (risperidone, aripiprazole) — but NOT as monotherapy for OCD. - Clomipramine (TCA with serotonergic and noradrenergic properties) — superior efficacy in some studies but more anticholinergic side effects. **Warning:** Benzodiazepines (lorazepam) are NOT first-line and carry risk of dependence; they may be used short-term for anxiety but do not treat OCD pathology.