A 58-year-old man from Delhi presents with a 7-day history of dysuria, urinary frequency, and suprapubic pain. He has a history of type 2 diabetes (HbA1c 8.2%) and mild chronic kidney disease (eGFR 55 mL/min/1.73m²). Urine culture grows E. coli sensitive to fluoroquinolones. He is started on levofloxacin 750 mg once daily. On day 3 of therapy, he develops acute onset severe pain in the left Achilles tendon with inability to walk. What is the most appropriate next step in management?

Explanation

## Fluoroquinolone-Induced Tendinopathy: Recognition and Management ### Clinical Presentation **Key Point:** Fluoroquinolone-associated tendinopathy is a well-established adverse effect that typically presents with acute tendon pain, swelling, and functional impairment, most commonly affecting the Achilles tendon. ### Risk Factors for Tendinopathy | Risk Factor | Mechanism / Notes | | --- | --- | | Age > 60 years | Increased collagen fragility | | Diabetes mellitus | Impaired tendon healing, glycation of collagen | | Chronic kidney disease | Altered drug clearance, accumulation | | Concurrent corticosteroids | Synergistic collagen degradation | | High-dose / prolonged FQ use | Dose-dependent toxicity | **High-Yield:** This patient has THREE independent risk factors: age 58 (borderline), diabetes, and CKD — making him at substantially elevated risk even on standard dosing. ### Pathophysiology 1. Fluoroquinolones inhibit bacterial DNA gyrase and topoisomerase IV 2. They also inhibit mitochondrial DNA gyrase in eukaryotic cells 3. This impairs collagen synthesis and cross-linking in tendons 4. Tendon microtears accumulate → acute rupture risk ### Management Algorithm ```mermaid flowchart TD A[Acute tendon pain during FQ therapy]:::outcome --> B{Confirm FQ causation}:::decision B -->|High suspicion| C[Discontinue FQ immediately]:::urgent C --> D[Imaging: Ultrasound or MRI]:::action D --> E{Rupture confirmed?}:::decision E -->|Yes| F[Orthopedic referral, possible surgery]:::action E -->|No| G[Rest, ice, NSAIDs, physical therapy]:::action C --> H[Switch to alternative antibiotic]:::action H --> I[Ensure adequate renal dosing]:::action ``` **Clinical Pearl:** Once tendinopathy is suspected, fluoroquinolone discontinuation is non-negotiable. Continuing the drug risks progression to complete tendon rupture, which may require surgical repair and prolonged rehabilitation. **Warning:** Do NOT reduce the dose and continue — the problem is the drug class itself, not the dose. NSAIDs and corticosteroids may mask symptoms but do not address the underlying collagen damage and increase rupture risk further. ### Antibiotic Alternatives for UTI in This Patient Given CKD (eGFR 55), suitable alternatives include: - **Cephalosporin** (e.g., cefixime 400 mg BD; renal-safe) - **Nitrofurantoin** (contraindicated if eGFR < 30; acceptable here at 55) - **Trimethoprim-sulfamethoxazole** (if susceptible; monitor renal function) **Key Point:** Imaging (ultrasound) is essential to rule out partial or complete tendon rupture and guide further orthopedic management. [cite:KD Tripathi 8e Ch 51]