Tetracyclines are a class of antibiotics which are commonly used in clinical practice.

Mechanism of action

Mechanism of action
  • Protein synthesis inhibitors
  • Binds to 30S subunit blocking binding of aminoacyl-tRNA

Mechanism of resistance
  • Increased efflux of the bacteria by plasmid-encoded transport pumps, ribosomal protection


  • Acne vulgaris
  • Lyme disease
  • Chlamydia
  • Mycoplasma pneumoniae

Adverse effects

  • Discolouration of teeth: therefore should not be used in children < 12 years of age
  • Photosensitivity
  • Angioedema
  • Black hairy tongue


Tetracyclines should not be given to women who are pregnant or breastfeeding due to the risk of discolouration of the infant's teeth.