Pharmacology · Antimicrobials (Cell Wall Inhibitors, Protein Synthesis Inhibitors, Fluoroquinolones)

A patient on fluoroquinolone therapy for a urinary tract infection develops tendon rupture. The sub-mechanism responsible for fluoroquinolone-induced tendinopathy involves:

  • A Chelation of magnesium ions within tenocyte extracellular matrix, disrupting collagen cross-linking and triggering matrix metalloproteinase activation ✓
  • B Direct inhibition of DNA gyrase in tenocytes leading to apoptosis
  • C Competitive antagonism of vitamin K-dependent coagulation factors reducing tendon vascularity
  • D Inhibition of cyclooxygenase-2 in tenocytes causing prostaglandin deficiency
Correct answer: A. Chelation of magnesium ions within tenocyte extracellular matrix, disrupting collagen cross-linking and triggering matrix metalloproteinase activation

Explanation

Fluoroquinolones chelate divalent cations, particularly Mg2+, which are essential cofactors for matrix metalloproteinase (MMP) inhibitors (TIMPs) and collagen fibril assembly. This chelation activates MMPs and simultaneously impairs collagen cross-linking, causing degradation of tendon extracellular matrix. Additionally, fluoroquinolones induce mitochondrial dysfunction and oxidative stress in tenocytes. Risk factors include age >60, concurrent corticosteroids, and renal failure. The Achilles tendon is most frequently affected. This is a class effect of all fluoroquinolones.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.

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