Macrolides and tetracyclines vs Aminoglycosides
How to tell Macrolides and tetracyclines and Aminoglycosides apart when a board question makes them look alike.
Macrolides are 50S/QT; tetracyclines are 30S/teeth-photosensitivity; aminoglycosides are 30S bactericidal with oto-nephrotoxicity.
Side by side
Atypical coverage with bacteriostatic protein-synthesis inhibition: macrolides bind 50S; tetracyclines bind 30S.
Serious aerobic gram-negative coverage with bactericidal 30S action plus nephrotoxicity and ototoxicity monitoring.
Macrolides block 50S translocation; tetracyclines prevent aminoacyl-tRNA attachment to the 30S subunit.
Aminoglycosides bind 30S irreversibly, cause misreading of mRNA, and require oxygen-dependent uptake.
Macrolide clue: QT prolongation and CYP interactions; tetracycline clue: photosensitivity and teeth/bone deposition.
Aminoglycoside clue: peak/trough monitoring with rising creatinine or hearing/vestibular toxicity.
The trap
Do not group all ribosomal antibiotics together; same ribosome target does not mean same toxicity or clinical lane.
The repair move
For protein-synthesis drugs, force three labels: ribosome subunit, static versus cidal, and signature toxicity.
Try a free question
CoreA patient with atypical pneumonia receives azithromycin. The drug binds the 50S ribosomal subunit and can prolong the QT interval. Which class best fits?
Show answer and explanation
Answer: A. Macrolide. Macrolides bind the 50S subunit and are classic atypical pneumonia drugs; QT prolongation is a key toxicity clue.
Why the other choices are tempting
- B. Tetracyclines bind 30S and are remembered for teeth/bone effects and photosensitivity.
- C. Aminoglycosides bind 30S irreversibly and are bactericidal with nephrotoxicity and ototoxicity.
- D. Fluoroquinolones inhibit DNA gyrase/topoisomerase.
- E. Sulfonamides inhibit folate synthesis.
Flashcards
Tap a card to flip it.
What is the fastest separator for Macrolides and tetracyclines vs Aminoglycosides?
Macrolides are 50S/QT; tetracyclines are 30S/teeth-photosensitivity; aminoglycosides are 30S bactericidal with oto-nephrotoxicity.
What clue should make you choose Macrolides and tetracyclines?
Atypical coverage with bacteriostatic protein-synthesis inhibition: macrolides bind 50S; tetracyclines bind 30S.
Quick answers
What is the fastest way to tell Macrolides and tetracyclines from Aminoglycosides?
Macrolides are 50S/QT; tetracyclines are 30S/teeth-photosensitivity; aminoglycosides are 30S bactericidal with oto-nephrotoxicity.
What is the key clue for Macrolides and tetracyclines?
Atypical coverage with bacteriostatic protein-synthesis inhibition: macrolides bind 50S; tetracyclines bind 30S.
What is the key clue for Aminoglycosides?
Serious aerobic gram-negative coverage with bactericidal 30S action plus nephrotoxicity and ototoxicity monitoring.
What is the common trap with Macrolides and tetracyclines vs Aminoglycosides?
Do not group all ribosomal antibiotics together; same ribosome target does not mean same toxicity or clinical lane.