Ciprofloxacin is a fluoroquinolone antibiotic used for urinary, gut, bone and prostate infections, and for typhoid. It penetrates tissue exceptionally well. It carries specific warnings about tendon damage and nerve effects, so it is reserved rather than first-line.
What is Ciprofloxacin?
Ciprofloxacin is a fluoroquinolone, dispensed as 250 mg and 500 mg tablets, as eye and ear drops, and as an infusion. It is a Schedule 4 prescription medicine, sold under its own name and as Cifran, Ciprobay, Ciplox and Biotech Ciprofloxacin.
It blocks two bacterial enzymes — DNA gyrase and topoisomerase IV — that bacteria need to unwind and copy their DNA. Without them the bacterium cannot replicate and dies. Human cells use structurally different enzymes, which is the basis of its selectivity.
It is a powerful, broad-spectrum antibiotic that penetrates tissue exceptionally well, reaching places many antibiotics struggle with — bone, the prostate, the inside of the eye. It is particularly effective against Gram-negative organisms, including Pseudomonas, which few oral antibiotics cover.
That capability is why its use has been deliberately narrowed. Regulators worldwide have restricted fluoroquinolones after recognising rare but serious and sometimes long-lasting effects on tendons, muscles, joints and the nervous system. Current guidance is that ciprofloxacin should not be used for mild or self-limiting infections, or where a safer antibiotic would do.
Being prescribed it is therefore not a sign of a worse infection — it usually means the organism, the site, or your allergies made it the appropriate choice.
What is Ciprofloxacin commonly used for?
- Urinary tract infections, including complicated infections and kidney infections (pyelonephritis).
- Prostate infections (prostatitis), where its tissue penetration is a genuine advantage.
- Gut infections — bacterial gastroenteritis, shigellosis, campylobacter, and severe travellers’ diarrhoea.
- Typhoid fever.
- Bone and joint infections, including osteomyelitis, often as long courses.
- Some respiratory infections, particularly involving Pseudomonas, as in cystic fibrosis or bronchiectasis.
- Skin and soft tissue infections caused by susceptible organisms.
- Some eye and ear infections, as drops.
- Anthrax exposure, in specific circumstances.
For uncomplicated cystitis in an otherwise healthy woman, ciprofloxacin is generally no longer first choice — nitrofurantoin or another narrower agent is preferred, precisely because of the fluoroquinolone cautions.
For travellers’ diarrhoea, most cases are self-limiting and need rehydration rather than an antibiotic. Ciprofloxacin is reserved for severe illness, blood in the stool or high fever — and resistance in campylobacter is now high in parts of Asia.
How Ciprofloxacin fits into this medicine category
| Group | Examples | Common targets |
|---|---|---|
| Fluoroquinolones | Ciprofloxacin (Cifran), levofloxacin | Urinary, gut, bone, prostate, Pseudomonas |
| Broad-spectrum penicillins | Amoxicillin | Chest, ear, throat, dental |
| Macrolides | Azithromycin | Chest, some STIs; penicillin allergy |
| Sulfonamide combinations | Co-trimoxazole (Purbac) | Urinary, chest, PCP |
| Nitroimidazoles | Metronidazole | Anaerobic and dental infections |
See the antibiotics and antimicrobials hub.
What to check before using Ciprofloxacin
Separate it from dairy, antacids, and iron, zinc, calcium or magnesium supplements by at least two hours — take ciprofloxacin two hours before or six hours after. This is not minor: those minerals bind ciprofloxacin in the gut and can reduce absorption enough for the treatment to fail. Milk, yoghurt, calcium-fortified juice, indigestion remedies and multivitamins all count.
Drink plenty of water, and avoid excessive sun — ciprofloxacin causes sun sensitivity.
Finish the whole course.
Tell your prescriber or pharmacist if:
- You have a history of tendon problems, or tendon trouble on a previous quinolone.
- You take a corticosteroid such as prednisone — combined with ciprofloxacin this markedly increases tendon rupture risk, particularly over 60.
- You have epilepsy or a seizure history. Ciprofloxacin lowers the seizure threshold.
- You have myasthenia gravis, which it can seriously worsen.
- You have a heart rhythm problem, particularly a long QT interval.
- You have kidney or liver disease.
- You have an aortic aneurysm or a connective tissue condition such as Marfan syndrome.
- You are pregnant or breastfeeding, or the medicine is for a child — fluoroquinolones are generally avoided in both.
- You take theophylline, warfarin, tizanidine, methotrexate, an NSAID, or a diabetes medicine.
- You drink significant caffeine — ciprofloxacin raises caffeine levels and can cause jitteriness and palpitations.
Follow the dispensing label. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
Tendon problems are the signature caution. Ciprofloxacin can cause tendon inflammation and, rarely, rupture — most often the Achilles. It can happen within days of starting, and occasionally weeks after finishing. Risk is higher over 60, on corticosteroids, and after a transplant.
If you develop pain, swelling or inflammation in a tendon — commonly the back of the ankle — stop taking it and contact your doctor. Rest the limb and avoid exercise until assessed. Do not train through it.
Nerve effects. Peripheral neuropathy — pain, burning, tingling, numbness or weakness — can begin soon after starting and may be long-lasting. Report it immediately rather than finishing the course and hoping.
Central nervous system effects are recognised: confusion, agitation, anxiety, depression, insomnia, hallucinations and, rarely, seizures.
Diarrhoea. Severe, watery or bloody diarrhoea, particularly with fever and particularly after the course ends, can indicate Clostridioides difficile infection.
Blood sugar can swing in either direction in people with diabetes.
Seek urgent medical attention for tendon pain or swelling, sudden severe pain in the ankle or calf, numbness or tingling in the limbs, confusion or hallucinations, a seizure, severe abdominal or back pain, palpitations or fainting, a rash that blisters or peels, facial or throat swelling, or severe or bloody diarrhoea.
Related medicine guides
Frequently asked questions
What is ciprofloxacin 500 mg used for? Urinary, gut, bone and prostate infections, typhoid, and severe travellers’ diarrhoea.
Why can I not take it with milk or antacids? Calcium, magnesium, iron and zinc bind ciprofloxacin in the gut and can reduce absorption enough for treatment to fail. Separate them by at least two hours.
Why does it have tendon warnings? Fluoroquinolones can cause tendon inflammation and rupture, most often the Achilles. Stop and contact your doctor if a tendon becomes painful or swollen.
Is it a strong antibiotic? It is broad-spectrum and penetrates tissue very well. It is reserved rather than first-line because of its specific side-effect profile.
Can I exercise while taking it? Avoid strenuous exercise, especially anything loading the Achilles. Stop and seek advice if a tendon becomes sore.
Can I take it for a simple bladder infection? Usually it is no longer first choice for uncomplicated cystitis. A narrower antibiotic such as nitrofurantoin is generally preferred.