Levofloxacin !

A «respiratory» fluoroquinolone that covers pneumococcus and atypical bacteria, fully absorbed by mouth and also used for drug-resistant tuberculosis.

Updated 2026-11-01

Class: Fluoroquinolones
Enzyme: Bacterial topoisomerase IV and DNA gyrase
ATC code: J01MA12
WHO Model List of Essential Medicines

Bacterial topoisomerase IV and DNA gyraseLevofloxacin

The figure shows levofloxacin bound to DNA cut by topoisomerase IV of Streptococcus pneumoniae.

Target in 3D: Bacterial topoisomerase IV and DNA gyrase. PDB structure 3RAE (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Levofloxacin, the active S-isomer of ofloxacin, traps topoisomerase IV and DNA gyrase on DNA they have cut. In pneumococcus topoisomerase IV is its main target. The trapped complexes turn into double-strand breaks and the bacterium dies.

Absorbed almost completely by mouth
Binds topoisomerase IV or gyrase on cut DNA
The enzyme cannot reseal the DNA
Double-strand breaks kill the bacterium

Pharmacokinetics

Absorption: Oral bioavailability about 99%; oral and IV forms give similar levels.
Metabolism: Very little.
Elimination: Mostly unchanged in the urine; the dose is adjusted when kidney function is reduced.
Half-life: About 6–8 hours.

Indications

Community-acquired pneumonia, including atypical bacteria and penicillin-resistant pneumococcus Community-acquired pneumonia →
Acute pyelonephritis and complicated urinary tract infection Acute pyelonephritis →
Chronic bacterial prostatitis Prostatitis →
Drug-resistant tuberculosis (WHO list of antituberculosis medicines) Tuberculosis →
Inhalational anthrax after exposure and plague

Adverse effects

Common

Nausea, diarrhoea and headache
Insomnia and dizziness
Photosensitivity

Contraindications

Allergy to levofloxacin or other quinolones

Key interactions

Antacids, sucralfate, iron, zinc and other polyvalent cations: Reduce absorption; the doses are spaced.
Insulin and oral antidiabetic drugs: Risk of severe low or high blood sugar.
Warfarin: Stronger anticoagulant effect.
Corticosteroids: Higher risk of tendon rupture.

What is monitored

Blood glucose, especially in diabetes
Kidney function to adjust the dose
Tendon pain, neuropathy symptoms and mental changes; ECG if QT risk

Administration and safety

Oral doses are spaced from antacids and mineral supplements
The IV form is infused slowly, never as a rapid or intramuscular injection
Oral and IV forms are interchangeable at the same dose

Nursing care

Teach the signs of hypoglycaemia
Teach to stop and report tendon pain or tingling
Encourage fluids
Ask about myasthenia gravis and steroid use

Pregnancy and breastfeeding

Usually avoided when a safer alternative exists; human data are limited.

Test yourself

Think of the answer, then tap the question to see it.

How does levofloxacin relate to ofloxacin?

It is the active S-isomer (levo form) of ofloxacin.

Why can a patient switch from IV to oral levofloxacin at the same dose?

Oral bioavailability is close to 100%.

Which metabolic adverse effect must diabetic patients watch for?

Severe hypoglycaemia (or hyperglycaemia).

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - LEVOFLOXACIN tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Levofloxacin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025); Quinolone(Levofloxacin)-DNA cleavage complex of type IV topoisomerase from S. pneumoniae (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.