A 58-year-old woman with chronic cancer pain is being managed with a multimodal analgesic regimen. Regarding adjuvant analgesics and non-opioid medications used in chronic pain management, all of the following are appropriate uses EXCEPT:

Explanation

## Adjuvant Analgesics in Chronic Pain Management ### Classification and Mechanisms **Key Point:** SSRIs are NOT first-line agents for neuropathic pain. Tricyclic antidepressants (TCAs) and SNRIs have superior evidence and efficacy. | Drug Class | Mechanism | Neuropathic Pain | Visceral Pain | Evidence Level | |------------|-----------|------------------|---------------|----------------| | Gabapentin/Pregabalin | Voltage-gated Ca²⁺ channel blockade | ✓ First-line | ✗ Limited | Strong (RCTs) | | Tricyclic antidepressants (TCA) | NE & 5-HT reuptake inhibition | ✓ First-line | ✓ Moderate | Strong (RCTs) | | SNRIs (venlafaxine, duloxetine) | NE & 5-HT reuptake inhibition | ✓ First-line | ✓ Moderate | Strong (RCTs) | | SSRIs (sertraline, paroxetine) | 5-HT reuptake inhibition only | ✗ Limited efficacy | ✗ Limited | Weak (observational) | | NSAIDs | COX inhibition → ↓ PGE₂, PGI₂ | ✗ Ineffective | ✓ First-line | Strong (RCTs) | ### Detailed Analysis of Each Option **Option 1 (Gabapentin):** ✓ CORRECT Gabapentin blocks presynaptic voltage-gated calcium channels (specifically α₂δ subunit), reducing release of excitatory neurotransmitters (glutamate, norepinephrine). FDA-approved for postherpetic neuralgia and diabetic neuropathy. **Option 2 (Tricyclic antidepressants):** ✓ CORRECT Amitriptyline and nortriptyline inhibit reuptake of norepinephrine and serotonin, enhancing descending inhibitory pain pathways. TCAs are first-line for neuropathic pain with strong RCT evidence (NNT ~3–4). **Option 3 (NSAIDs):** ✓ CORRECT NSAIDs inhibit COX-1 and COX-2, reducing prostaglandin synthesis. They are highly effective for inflammatory, visceral, and somatic pain but have limited efficacy in pure neuropathic pain. **Option 4 (SSRIs):** ✗ INCORRECT SSRIs (e.g., sertraline, paroxetine) inhibit ONLY serotonin reuptake and lack norepinephrine activity. They have weak evidence for neuropathic pain and are NOT recommended as first-line agents. TCAs and SNRIs (which block both NE and 5-HT) are superior for neuropathic pain management. **High-Yield:** The critical distinction is that **dual-action agents (TCAs and SNRIs)** are superior to **single-action agents (SSRIs)** for neuropathic pain. This is a frequently tested concept in NEET PG pain management questions. **Mnemonic:** **GABS-TCA** = Gabapentin/Pregabalin, Amitriptyline/TCA, and SNRIs are the "Big Three" first-line adjuvants for neuropathic pain. **Clinical Pearl:** In this patient with cancer pain, a multimodal approach combining opioids + gabapentin/pregabalin + TCA (or SNRI) + NSAIDs (if appropriate) provides superior analgesia with lower opioid doses and reduced side effects. **Warning:** Do not confuse SSRIs with SNRIs. SSRIs alone are inadequate for neuropathic pain; SNRIs (venlafaxine, duloxetine) are appropriate first-line agents because they block both norepinephrine and serotonin reuptake. [cite:Harrison 21e Ch 297]