A 38-year-old woman presents with major depressive disorder accompanied by chronic pain syndrome (fibromyalgia). She has no cardiac history. Which antidepressant is the drug of choice for this presentation?

Explanation

## Drug of Choice: Venlafaxine for Depression + Fibromyalgia **Key Point:** When major depressive disorder coexists with fibromyalgia/chronic pain syndrome, SNRIs (venlafaxine, duloxetine) are the preferred modern first-line agents due to dual efficacy in both mood and pain, combined with a superior safety profile compared to TCAs. ### Mechanism of Dual Action Venlafaxine inhibits both serotonin and norepinephrine reuptake. The noradrenergic component activates descending pain inhibitory pathways in the dorsal horn of the spinal cord, providing analgesic benefit independent of its antidepressant effect. At doses ≥150 mg/day, norepinephrine reuptake inhibition becomes clinically significant (KD Tripathi, *Essentials of Medical Pharmacology*, 8th ed.). ### Comparative Analysis | Feature | Venlafaxine | Fluoxetine | Amitriptyline | Sertraline | |---------|-------------|-----------|---------------|------------| | **Serotonin reuptake inhibition** | ✓ | ✓ | ✓ | ✓ | | **Norepinephrine reuptake inhibition** | ✓ (dose-dependent) | ✗ | ✓ | ✗ | | **Efficacy in depression** | ✓✓ | ✓✓ | ✓✓ | ✓✓ | | **Efficacy in fibromyalgia/chronic pain** | ✓✓ | ✗ | ✓✓ | ✗ | | **Cardiac safety (no QT prolongation)** | ✓ | ✓ | ✗ | ✓ | | **Anticholinergic burden** | Minimal | Minimal | High | Minimal | | **Preferred in modern guidelines** | ✓ (first-line) | ✗ | Second-line | ✗ | ### Why Not Amitriptyline? Amitriptyline (TCA) has well-established efficacy in both depression and fibromyalgia pain and was historically considered the drug of choice. However, it carries significant risks: anticholinergic side effects (urinary retention, dry mouth, constipation), orthostatic hypotension, sedation, and — critically — cardiac conduction delays (QT prolongation, risk of arrhythmias). Current guidelines (ACR fibromyalgia guidelines; NICE depression guidelines) position SNRIs as preferred first-line agents over TCAs due to this safety profile. The stem specifies **no cardiac history**, which removes the absolute contraindication to amitriptyline but does not make it the preferred choice — safety and tolerability still favor venlafaxine. ### Why Not SSRIs (Fluoxetine/Sertraline)? SSRIs lack meaningful noradrenergic activity and therefore provide inadequate analgesia in fibromyalgia. They are appropriate for depression alone but not for the combined presentation. **High-Yield (NEET PG):** For depression + neuropathic pain / fibromyalgia → SNRI (venlafaxine or duloxetine) is the drug of choice. Duloxetine is FDA-approved specifically for fibromyalgia; venlafaxine is the classic SNRI taught in this context. **Clinical Pearl:** Duloxetine (another SNRI) is FDA-approved for fibromyalgia, diabetic peripheral neuropathy, and MDD — making it an equally valid answer if listed. Between the options given, venlafaxine is the correct SNRI choice. **Reference:** KD Tripathi, *Essentials of Medical Pharmacology*, 8th ed., Chapter on Antidepressants; Harrison's *Principles of Internal Medicine*, 21st ed., Fibromyalgia management.