Fluoroquinolones vs Sulfonamides
How to tell Fluoroquinolones and Sulfonamides apart when a board question makes them look alike.
Fluoroquinolones: block DNA gyrase, risk tendon rupture and QT prolongation; sulfonamides: block folate synthesis, risk SJS and hyperkalemia.
Side by side
DNA gyrase/topoisomerase inhibition with tendinopathy, QT risk, neuropathy warnings, and cartilage/tendon concerns.
Folate synthesis blockade with rash, hemolysis risk in G6PD deficiency, and kernicterus concern near term.
Fluoroquinolones inhibit bacterial DNA gyrase and topoisomerase IV.
Sulfonamides mimic PABA and inhibit dihydropteroate synthase; trimethoprim blocks a later folate step.
Tendon pain after ciprofloxacin/levofloxacin or QT-risk review points fluoroquinolone.
Trimethoprim-sulfamethoxazole, folate-pathway wording, rash, or hyperkalemia points sulfonamide combination logic.
The trap
Both can appear in urinary infection questions, so the adverse effect or mechanism usually decides.
Watch it explained
Test it nowThe repair move
When both feel like UTI drugs, ignore the infection site and sort by mechanism: DNA enzyme versus folate enzyme.
Try a free question
CoreA patient treated for a complicated urinary infection later develops Achilles tendon pain and QT prolongation risk is reviewed. Which antibiotic class best fits?
Show answer and explanation
Answer: A. Fluoroquinolone. Fluoroquinolones inhibit DNA gyrase/topoisomerase and are remembered for tendinopathy, QT risk, cartilage concerns, and neuropathy warnings.
Why the other choices are tempting
- B. Sulfonamides block folate synthesis and are remembered for rash, hemolysis risk, and kernicterus risk.
- C. Macrolides can prolong QT but do not cause the classic tendon clue.
- D. Aminoglycosides cause oto-nephrotoxicity and require monitoring.
- E. Nitroimidazoles cover anaerobes/protozoa and cause disulfiram-like reactions.
Flashcards
Tap a card to flip it.
What is the fastest separator for Fluoroquinolones vs Sulfonamides?
Fluoroquinolones: block DNA gyrase, risk tendon rupture and QT prolongation; sulfonamides: block folate synthesis, risk SJS and hyperkalemia.
What clue should make you choose Fluoroquinolones?
DNA gyrase/topoisomerase inhibition with tendinopathy, QT risk, neuropathy warnings, and cartilage/tendon concerns.
Quick answers
What is the fastest way to tell Fluoroquinolones from Sulfonamides?
Fluoroquinolones: block DNA gyrase, risk tendon rupture and QT prolongation; sulfonamides: block folate synthesis, risk SJS and hyperkalemia.
What is the key clue for Fluoroquinolones?
DNA gyrase/topoisomerase inhibition with tendinopathy, QT risk, neuropathy warnings, and cartilage/tendon concerns.
What is the key clue for Sulfonamides?
Folate synthesis blockade with rash, hemolysis risk in G6PD deficiency, and kernicterus concern near term.
What is the common trap with Fluoroquinolones vs Sulfonamides?
Both can appear in urinary infection questions, so the adverse effect or mechanism usually decides.