A 52-year-old woman presents to the pain clinic with a 6-month history of severe, burning pain in her right foot following a crush injury to the ankle. She describes the pain as disproportionate to the clinical findings, with associated swelling, skin color changes (mottled erythema), and increased sweating. Temperature of the affected limb is 2°C lower than the contralateral side. She has already failed trials of NSAIDs and paracetamol. On examination, allodynia is evident. Which of the following is the most appropriate first-line pharmacological intervention for this condition?

Explanation

## Clinical Diagnosis: Complex Regional Pain Syndrome (CRPS) **Key Point:** This patient presents with classic features of CRPS Type 1 (formerly Reflex Sympathetic Dystrophy): disproportionate pain, swelling, skin changes, temperature asymmetry, and allodynia following a crush injury. ### First-Line Pharmacotherapy for CRPS Gabapentin is the evidence-based first-line agent for neuropathic pain in CRPS because: 1. **Mechanism**: Gabapentin reduces calcium influx via α~2~δ subunit antagonism on voltage-gated calcium channels, reducing neurotransmitter release and central sensitization. 2. **Efficacy**: Demonstrated benefit in randomized trials for CRPS-related neuropathic pain. 3. **Safety profile**: Well-tolerated with predictable pharmacokinetics; no drug interactions. 4. **Dosing**: Starting 300 mg thrice daily, titrated to 1800–3600 mg/day in divided doses based on response and tolerability. **High-Yield:** Pregabalin is an alternative first-line agent with similar efficacy but higher cost; gabapentin remains preferred in resource-limited settings and is guideline-recommended by the International Association for the Study of Pain (IASP). ### Multimodal Approach in CRPS | Intervention | Role | Evidence | |---|---|---| | Gabapentin/Pregabalin | First-line neuropathic pain | Strong | | Physical/Occupational therapy | Restore function, reduce disability | Strong | | Topical agents (lidocaine patch, capsaicin) | Adjunctive, localized pain | Moderate | | Opioids (morphine, tramadol) | Reserved for refractory pain after neuropathic agents | Weak for CRPS-specific benefit | | NSAIDs | Ineffective in established CRPS | Weak | | Corticosteroids (early CRPS) | May reduce inflammation if started early | Moderate (early phase only) | **Clinical Pearl:** CRPS is fundamentally a neuropathic pain disorder with sympathetic dysfunction; therefore, neuropathic agents (gabapentin, pregabalin) are superior to opioids or NSAIDs as monotherapy. Early diagnosis and multimodal intervention (including physical therapy and sympathetic blocks in severe cases) improve outcomes. **Warning:** Opioids alone are ineffective and risk dependence in chronic CRPS; they should be reserved for adjunctive use only after neuropathic agents have been optimized.