A fluoroquinolone antibiotic
Ciprofloxacin
A broad-spectrum fluoroquinolone antibiotic now reserved for specific infections because of rare but serious, sometimes lasting side effects on tendons, nerves and mental health.
What is Ciprofloxacin?
Ciprofloxacin is a fluoroquinolone antibiotic that works against a wide range of bacteria, including many causing urinary, gut and certain chest infections. Because of its side-effect profile, it is generally reserved for situations where other antibiotics are unsuitable.
Education and reference only. This is a plain-language guide to Ciprofloxacin — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Ciprofloxacin is a fluoroquinolone antibiotic that works against a wide range of bacteria, including many that cause urinary, gut and certain chest infections. Once prescribed freely, it is now a "reserved" antibiotic in the UK: the MHRA has restricted its use because of rare but serious side effects that can occasionally be long-lasting or permanent. It is generally kept for infections where there is no safer alternative, rather than used as a first-choice antibiotic. In the UK it is sold as Ciproxin; in the US the equivalent brand is Cipro.
How it works
Ciprofloxacin blocks bacterial enzymes (DNA gyrase and topoisomerase) that bacteria need to copy and repair their DNA. Without these enzymes the bacteria cannot multiply or survive, so the infection is cleared. It penetrates well into many body tissues, including the urinary tract and lungs, which is part of why it was historically so widely used. The same broad reach is also why resistance and disruption of the body's normal bacteria are concerns, and why it is now used more sparingly.
Company & origin
Originated / developed by: Bayer.
Ciprofloxacin was synthesized in 1981 by Klaus Grohe and colleagues at Bayer in Germany, patented in 1983, and approved by the FDA in 1987 as the first widely used oral fluoroquinolone (Cipro).
Practical use
How to take Ciprofloxacin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it at evenly spaced times and complete the full course, even if you feel better, to clear the infection and limit resistance.
- Separate it from dairy products, indigestion remedies, and iron or calcium supplements, which can stop it being absorbed — take these a few hours apart.
- Stop and seek urgent advice if you develop tendon pain or swelling, as it can rarely cause tendon damage or rupture.
- Report any new numbness, tingling, severe mood changes, or sudden severe abdominal, chest or back pain promptly.
- Drink plenty of fluids and avoid too much sun exposure, as it can increase sensitivity to sunlight.
- Tell your doctor about heart-rhythm problems or other medicines, as it can affect the heart's electrical activity.
Weighing it up
Advantages & disadvantages of Ciprofloxacin
Advantages
- Effective against a broad range of bacteria, including some hard-to-treat ones.
- Reaches good levels in tissues such as the urinary tract and gut.
- Useful when other antibiotics cannot be used.
- Available in forms that allow treatment outside hospital.
Disadvantages
- Can rarely cause serious tendon damage or rupture, including of the Achilles tendon.
- Linked to rare but serious effects on the nerves, mental health, and the main artery (aortic aneurysm or tear).
- Can prolong the heart's QT interval and affect heart rhythm.
- Absorption is reduced by dairy and antacids, and it is reserved for when safer options are unsuitable.
Practical use
Good to know
Because of an MHRA safety restriction, ciprofloxacin is reserved for situations where other antibiotics cannot be used. The key safety message is to stop the antibiotic and seek medical advice at the first sign of tendon pain or swelling (especially around the back of the ankle/Achilles), new nerve symptoms such as pins and needles or burning, or changes in mood or mental health — these can rarely be serious and lasting. It should not normally be combined with steroid tablets, which add to the tendon risk. Dairy products, indigestion remedies (antacids), and iron or zinc supplements bind to it and stop it being absorbed, so they are separated from it. It can also lower the seizure threshold and raise caffeine levels.
Who should not take it / use with caution
- People who have had a tendon problem (such as tendon pain, swelling or rupture) linked to a fluoroquinolone before — a reason not to take it again.
- Used with great caution, and usually avoided, in older people, those taking steroids, and people with a history of seizures or certain heart-rhythm risks (such as QT prolongation).
- Avoided where a safer antibiotic will do the job, and used cautiously in pregnancy, breastfeeding and in children/young people except in specific situations.
Monitoring
- For any tendon, nerve, joint or mental-health symptoms (stop and seek advice)
- Response of the infection
- Kidney function and INR (if on warfarin) where relevant
Side effects
- Nausea, diarrhoea, tummy upset and headache are the more common, milder effects.
- Tendon pain or swelling (notably the Achilles), which can rarely progress to tendon rupture — stop and seek advice if this occurs.
- Rarely, lasting nerve symptoms, joint or muscle problems, mood or mental-health changes, seizures, heart-rhythm changes (QT prolongation), or serious gut infection (Clostridioides difficile) — all reasons to seek prompt medical advice.
Key interactions
- Dairy products, antacids (indigestion remedies), and iron, zinc or calcium supplements bind to it and block absorption, so they are taken well apart from it.
- Steroid tablets add to the tendon-injury risk and are best avoided alongside it; care also with medicines that prolong the QT interval.
- It raises levels of theophylline and caffeine, can increase the effect of warfarin (raising bleeding risk), and may interact with certain diabetes medicines affecting blood sugar.
Available as: Tablets, a liquid (suspension), and forms given by drip in hospital. Separate eye and ear drops also exist for local infections.
Answers
Ciprofloxacin: frequently asked questions
Why is ciprofloxacin only given for certain infections now?
The MHRA has restricted fluoroquinolones like ciprofloxacin because, although usually well tolerated, they can rarely cause serious and sometimes long-lasting effects on tendons, nerves, joints and mental health. They are now reserved for infections where no safer antibiotic is suitable, rather than used as a first choice.
What tendon symptoms should make me stop it?
Stop the antibiotic and contact a doctor straight away if you get pain, swelling or tenderness in a tendon — most often the Achilles tendon at the back of the ankle. In rare cases the tendon can rupture, and the risk is higher in older people and those also taking steroid tablets.
Can I take it with milk or indigestion remedies?
Dairy products, antacids and iron, zinc or calcium supplements stick to ciprofloxacin and stop your body absorbing it, which can make it fail to work. They should be taken well apart from the antibiotic — your pharmacist can advise on the timing for your situation.
Is it safe with my other medicines?
Ciprofloxacin has several important interactions, including with warfarin, theophylline, some diabetes medicines and anything that affects heart rhythm, and it can raise the effect of caffeine. Always tell your pharmacist or prescriber what else you take so they can check it is safe.
What is the difference between ciprofloxacin and Cipro or Ciproxin?
They are the same medicine — ciprofloxacin is the generic (active-ingredient) name, Ciproxin is a common UK brand and Cipro is the equivalent US brand. The active ingredient is identical.
The wider class
About Fluoroquinolone antibiotics
Ciprofloxacin belongs to the fluoroquinolone antibiotics class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Ciprofloxacin.
- MHRA Drug Safety Update: Fluoroquinolone antibiotics — reminder of restrictions and precautions.
- NICE CKS: Ciprofloxacin.
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