What it is
Ciprofloxacin is a second-generation fluoroquinolone that is very active against Gram-negative bacteria (E. coli, Pseudomonas). It penetrates tissues well and has good oral bioavailability, so it is used in complicated urinary infections, prostatitis and some severe infectious diarrhoeas. Against Gram-positives and atypical bacteria it is weak.
Since 2018–2019 the European and Spanish medicines agencies have restricted fluoroquinolones because of serious, long-lasting and sometimes irreversible side effects (tendons, muscles, nerves, nervous system, aorta). They must not be used for mild or self-limiting infections, or when another antibiotic is appropriate: today they are second-line.
Mechanism of action
It works by inhibiting:
- Bacterial DNA gyrase and topoisomerase IV (it blocks DNA synthesis and replication)
- A bactericidal effect (it kills bacteria, not just stops them)
- Very active against Gram-negatives; weak against Gram-positives and atypical bacteria
At the counter
When to recommend it
- Complicated urinary infections caused by Gram-negatives, according to the culture result
- Acute bacterial prostatitis
- Severe infectious diarrhoea (Salmonella, Shigella, Campylobacter) on prescription
- Gram-negative infections where another antibiotic is not appropriate
When not to
- Allergy to quinolones
- A previous serious reaction to a quinolone, or a history of tendinitis or tendon rupture with them
- Mild or self-limiting infections (sore throat, acute bronchitis, uncomplicated cystitis when there are alternatives)
- Under 18s (except for specific indications)
- Pregnancy and breastfeeding
Warnings
- Important Tendinitis / tendon rupture (Achilles): rare but serious and disabling. Higher risk over 60 and with corticosteroids.
- Important Peripheral neuropathy: potentially irreversible. Warn the patient about tingling and weakness.
- Caution Photosensitivity: severe skin reactions in the sun. Recommend full sun protection.
- Caution Psychiatric and nervous system effects (confusion, anxiety, insomnia, dizziness) and, in at-risk patients, aortic aneurysm or dissection. Advise not driving if dizziness appears.
Pharmacokinetics
- Absorption
- Rapid oral absorption. Bioavailability of 70–80%. Food has no significant effect, but calcium, iron, magnesium and dairy products do. Peak at 1–2 hours.
- Distribution
- Wide tissue distribution (urine, prostate, lung, eye). Very high urine concentrations. Protein binding of 20–40%. It crosses the placenta.
- Metabolism
- Minimal hepatic metabolism. Most of it is eliminated unchanged.
- Elimination
- 50–75% eliminated unchanged by the kidney. Half-life of 4 hours. High concentrations in urine.
Ciprofloxacin vs nitrofurantoin
| Aspect | Ciprofloxacin | Nitrofurantoin |
|---|---|---|
| Antibacterial spectrum | Broad, mainly Gram-negatives | Urinary tract only (mainly E. coli) |
| Systemic effect | Yes: useful in prostatitis | No: it acts in the urine |
| Safety profile | Tendons, nerves, aorta: restricted | Better in short courses; avoid with reduced kidney function and in long courses |
| Resistance | Increasing | Low |
| Ideal indication | Complicated UTI, prostatitis | Uncomplicated cystitis |
Ciprofloxacin for complicated urinary infections or prostatitis when it is indicated. Nitrofurantoin (or fosfomycin) for simple cystitis: a better safety profile and less resistance.
Self-assessment
Three questions. When you check your answers you will see the explanation for each one.
-
The European and Spanish agencies restricted fluoroquinolones because of serious and sometimes irreversible side effects. They are kept for infections where another antibiotic is not appropriate.
-
The magnesium and aluminium in antacids (and also calcium, iron and dairy products) form complexes with quinolones and greatly reduce their absorption. They need to be taken apart.
-
Tendinitis and peripheral neuropathy are serious side effects of quinolones. Tendon pain, especially at the ankle, or persistent tingling mean stopping and getting checked straight away.
Training content. It does not replace the summary of product characteristics or clinical judgement.