Medicine & USMLE


Antibiotics / Antiparasitics
  1. Penicillin Overview
  2. Penicillinase-Sensitive vs. Penicillinase-Resistant Penicillins
  3. Anti-Pseudomonal Penicillins
  4. Cephalosporins Overview
  5. 1st Generation Cephalosporins
  6. 2nd Generation Cephalosporins
  7. 3rd Generation Cephalosporins
  8. 4th Generation Cephalosporins
  9. 5th Generation Cephalosporins
  10. Carbapenems
  11. Monobactams (Aztreonam)
  12. Vancomycin
  13. Aminoglycosides
  14. Tetracyclines
  15. Tigecycline
  16. Chloramphenicol
  17. Clindamycin
  18. Linezolid
  19. Macrolides
  20. Polymyxins
  21. Sulfonamides
  22. Dapsone
  23. Trimethoprim
  24. Fluoroquinolones
  25. Daptomycin
  26. Metronidazole
  27. Rifamycins (Rifampin, Rifabutin)
  28. Isoniazid
  29. Pyrazinamide
  30. Ethambutol
  31. Chloroquine


Ethambutol is an antibiotic that inhibits the enzyme arabinosyltransferase, which is an enzyme that produces arabinogalactan, a building block of the mycobacterial cell wall seen in tuberculosis. It is used in combination with other antitubercular agents to treat tuberculosis. The main adverse effect of ethambutol is optic neuropathy, which can cause red-green color blindness, decreased visual acuity, or central scotoma. This side effect can be reversed by discontinuation of the drug.

Key Points

  • Ethambutol
    • Mechanism
      • Inhibits arabinosyltransferase
        • Prevents production of arabinogalactan, a key component of mycobacterial cell wall
    • Clinical Use
      • Mycobacterium tuberculosis
        • Part of RIPE regimen of rifamycin, isoniazid, pyrazinamide, and ethambutol
      • May be used to treat mycobacterium avium complex (MAC)
    • Adverse Effects
      • Optic neuropathy
        • Clinically manifests as red-green color blindness, decreased visual acuity, and central scotoma
        • Reversible with discontinuation of the drug