Ciprofloxacin vs Norfloxacin

## Overview

Norfloxacin was one of the first fluoroquinolones, developed before ciprofloxacin. It has lower systemic bioavailability and tissue penetration, making it limited to urinary tract and gastrointestinal infections. Ciprofloxacin is broader and used for systemic infections.

## Mechanism of Action

Both inhibit bacterial DNA gyrase and topoisomerase IV. Norfloxacin's weaker systemic absorption limits its use to infections where high urinary concentrations are sufficient.

## Pharmacokinetics

Norfloxacin: oral bioavailability ~30–40%, half-life ~3–4 h, primarily urinary excretion. Ciprofloxacin: bioavailability ~70–80%, excellent tissue penetration, systemic use. Norfloxacin does not achieve adequate tissue levels for pneumonia, soft tissue, or bloodstream infections.

## Spectrum

Norfloxacin active against E. coli, Klebsiella, Proteus, and some S. aureus — adequate for uncomplicated UTI. Ciprofloxacin covers the same organisms plus Pseudomonas, provides systemic penetration.

## Key Takeaways

- Norfloxacin: UTI-only drug (insufficient systemic bioavailability)
- Ciprofloxacin: superior in all respects except norfloxacin's lower cost in some markets
- Norfloxacin essentially obsolete where ciprofloxacin is available