Tetracyclines (TCNs)

  • Binds bacterial ribosomal unit (30s) → blocks bacterial protein synthesis
  • Spectrum: GP/GN bacteria, Chlamydia, Mycoplasma, rickettsia, spirochetes (syphilis, Lyme disease), certain mycobacteria (leprosy); different types of TCNs:
    • Doxycycline: excreted in GI tract, so can use in renal failure patients; photosensitivity
    • Tetracycline: most common to cause fixed drug eruption and may cause onycholysis, contraindicated in patients <9 years old due to brown discoloration of gingival third of teeth; photosensitivity
    •    
       Minocycline treatment of choice for CARP (confluent and reticulated papillomatosis of Gougerot-Carteaud) 
         
      Minocycline: side effect includes blue-black pigmentation of skin/teeth (green-gray discoloration of mid-portion of teeth), drug-induced LE, autoimmune hepatitis
    • Demeclocycline: most phototoxic (then doxycycline
  • ↓ Absorption with Fe/Ca2+; pregnancy category D