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Available Tetracyclines
  • Tetracycline
  • Oxytetracycline
  • Demeclocycline
  • Doxycycline
  • Minocycline
  • Are primarily bacteriostatic
  • Inhibit protein synthesis by binding to 30s ribosome in susceptible organism
  • Subsequent to such binding, attachment of aminoacyl-t-RNA to acceptor (A) site of mRNA-ribosome complex is interfered with
  • As a result, peptide chain fails to grow
  • Irritative effects-
    • Oral- Epigastric pain, nausea, vomiting, diarrhea, Odynophagia and esophageal ulceration- due to release of material of capsule during swallowing especially with doxycycline
    • IM- Very painful
    • IV- thrombophlebitis
  • Organ Toxicity-
    • Liver damage- Fatty infiltration and jaundice
    • Kidney damage- Fanconi anemia by outdated tetracycline
    • Phototoxicity- sunburn like esp. with doxycycline
    • Teeth and bone- Chelating property, gets deposited in developing bone and teeth, brown discoloration, ill formed tooth susceptible to caries
    • Antianabolic effect-reduce protein synthesis and have catabolic effect
    • Increased ICP
    • Diabetes insipidus- Demeclocycline antagonizes ADH action
    • Vestibular toxicity- Minocycline can cause ataxia, vertigo and nystagmus
  • Hypersensitivity- Skin rash, urticaria
  • Superinfection- Marked suppression of resident flora, Intestinal

superinfection by Candida albicans is most prominent, Psudomembranous enterocolitis is rare.

  • Empirical therapy– initial treatment of mixed infection, although combination of B-lactam, and AG is much preferred
  • DOC in:
    • Veneral disease– Chlamydia urethritis/endocervicitis, LGV, Granuloma inguinale
    • Atypical pneumonia
    • Cholera
    • Brucellosis
    • Plague
    • Relapsing fever– Borrellia recurrentis
    • Rickettsial infection– typhus, Q fever, RMSF
  • UTI
  • Community acquired pneumonia- when more selective antibiotic cannot be used
  • Acne vulgaris- Propionibacterium acne is sensitive to tetracycline
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