A 35-year-old woman develops tendon pain and swelling while on a fluoroquinolone for a urinary tract infection. The proposed mechanism of fluoroquinolone-induced tendinopathy involves:
- A Chelation of magnesium ions in tendons, disrupting collagen cross-linking and inducing matrix metalloproteinase upregulation ✓
- B Inhibition of collagen synthesis via suppression of fibroblast MMP activity
- C Direct mitochondrial DNA gyrase inhibition causing tenocyte apoptosis
- D Free radical generation secondary to CYP1A2 inhibition in tenocytes
Correct answer: A. Chelation of magnesium ions in tendons, disrupting collagen cross-linking and inducing matrix metalloproteinase upregulation
Explanation
Fluoroquinolones chelate divalent cations (especially Mg2+) in collagen-rich tissues. Loss of Mg2+ disrupts integrin-mediated tenocyte signalling, decreases collagen synthesis, and upregulates matrix metalloproteinases (MMPs), leading to matrix degradation and tendon rupture. Risk is greatest with concomitant corticosteroids, in the elderly, and in the Achilles tendon.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.