## Fluoroquinolone-Induced Tendinopathy ### Clinical Presentation This patient develops acute Achilles tendon pain and swelling during fluoroquinolone therapy — a classic presentation of fluoroquinolone-induced tendinopathy. ### Mechanism of Injury **Key Point:** Fluoroquinolones inhibit bacterial DNA gyrase (topoisomerase II), but they also inhibit the human mitochondrial topoisomerase II in tendon fibroblasts, leading to impaired collagen synthesis and tendon degeneration. ### Risk Factors for Tendinopathy - Age > 60 years (this patient is 58, borderline) - Concurrent corticosteroid use - Renal impairment - Achilles tendon (most commonly affected site) - Prolonged fluoroquinolone exposure ### High-Yield Facts **High-Yield:** Achilles tendon rupture can occur even weeks after cessation of fluoroquinolone therapy. The risk is approximately 3-fold higher than in the general population. **Mnemonic: TENDON** — **T**opoisomerase inhibition, **E**lderly patients, **N**itrofurantoin (also causes), **D**uration of therapy, **O**lder quinolones (especially), **N**SAIDs (additive risk). ### Management 1. Discontinue fluoroquinolone immediately 2. Immobilize the affected tendon 3. Avoid weight-bearing 4. NSAIDs (cautiously, as they may worsen tendinopathy) 5. Physiotherapy after acute phase resolves 6. Surgical repair if rupture occurs ### Fluoroquinolone Generations and Tendinopathy Risk | Generation | Examples | Tendinopathy Risk | |---|---|---| | First | Nalidixic acid | High | | Second | Ciprofloxacin, norfloxacin | High | | Third | Levofloxacin, ofloxacin | Moderate-High | | Fourth | Moxifloxacin, gemifloxacin | Moderate | **Clinical Pearl:** Levofloxacin is the L-isomer of ofloxacin and carries a significant risk of tendinopathy, particularly in older adults. The risk is dose- and duration-dependent. [cite:KD Tripathi 8e Ch 47]
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