Norfloxacin
Fluoroquinolones
Fluoroquinolones
Old oral fluoroquinolone, the least potent of the group: blood levels are low, so it is limited to urinary and prostate infections.
Quick facts
- Group
- Fluoroquinolones
- Target
- Bacterial DNA gyrase and topoisomerase IV
- Used for
- Urinary tract infections · Bacterial prostatitis
- Key effects
- Nausea · Headache and dizziness · Joint pain
- Monitor
- Tendon pain or swelling · Neuropathy symptoms
- ATC
- J01MA06
No doses: the clinician sets them by the current guideline.
Mechanism of action
No structure of norfloxacin bound to its target is published; the figure shows ciprofloxacin, its direct derivative (an ethyl swapped for a cyclopropyl), wedged into the DNA cut by Staphylococcus aureus DNA gyrase.
Norfloxacin traps DNA gyrase and topoisomerase IV after they have cut the DNA, so the break is not resealed and the bacterium dies. Its gram-negative activity resembles ciprofloxacin's, though weaker, and it is also the least active of the group against gram-positives. Because blood levels are low, it is limited to urinary and prostate infections.
- Enters the gram-negative bacterium
- Wedges between gyrase and the cut DNA
- The break is not resealed and the helix breaks
- The bacterium dies (bactericidal)
Indications
- Urinary tract infections by susceptible gram-negatives, when other recommended antibiotics cannot be used Urinary tract infection (acute cystitis) →
- Bacterial prostatitis Prostatitis →
- Not used for systemic infections (blood, lung, bone) because of its low blood levels
Adverse effects
Common
- Nausea, abdominal pain and diarrhoea
- Headache and dizziness
- Rash and photosensitivity
- Joint pain
Contraindications
- Allergy to any quinolone
- History of a serious adverse effect with a quinolone or fluoroquinolone
Key interactions
- Antacids, calcium, iron and multivitamins with minerals
- Chelate norfloxacin and reduce absorption; separated by at least 2 hours.
- Corticosteroids
- Increase the risk of tendon injury.
- NSAIDs and theophylline
- Raise the risk of seizures with fluoroquinolones.
What is monitored
- Tendon pain or swelling
- Neuropathy symptoms (tingling, burning, weakness)
- Urine culture and clinical response
Administration and safety
- Oral, separated from antacids, iron and calcium products
- Not used for mild or self-limiting infections, nor to prevent travellers' diarrhoea or recurrent urinary infections
Nursing care
- Ask about previous adverse effects with quinolones
- Teach to stop and seek advice if tendon pain, tingling or weakness appears
- Watch people over 60, transplant recipients and those on corticosteroids more closely
- Teach sun protection
Pharmacokinetics
- Absorption
- Oral; cations (calcium, iron, aluminium) chelate it and reduce absorption.
- Distribution
- Low blood levels, not enough for systemic infections.
- Metabolism
- Partly hepatic.
- Elimination
- About a quarter leaves unchanged in the urine.
- Half-life
- 3 to 5 hours.
Test yourself
Think of the answer, then tap the question to see it.
Why is norfloxacin not used for pneumonia or bacteraemia?
Its blood levels are low, not enough outside the urinary tract.
Which groups have a higher risk of tendon rupture with fluoroquinolones?
People over 60, those on corticosteroids and solid-organ transplant recipients.
How is norfloxacin related to ciprofloxacin?
Ciprofloxacin derives from it (an ethyl swapped for a cyclopropyl) and is more potent, with useful systemic levels.
Which uses did the European Medicines Agency restrict for fluoroquinolones?
They are not used for mild or self-limiting infections, nor to prevent travellers' diarrhoea or recurrent lower urinary infections.
Connections
← Back to the class: Fluoroquinolones
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Quinolone- and fluoroquinolone-containing medicinal products - referral (European Medicines Agency, 2019); The twinned 3.35A structure of S. aureus Gyrase complex with Ciprofloxacin and DNA (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.