Anti-infective
Fluoroquinolones
e.g. ciprofloxacin — Broad-spectrum antibiotics now restricted to specific situations because of serious side-effects.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Fluoroquinolones are powerful broad-spectrum antibiotics. Because of safety concerns they are now reserved for particular infections where alternatives are unsuitable.
How it works
They inhibit the bacterial enzymes (DNA gyrase and topoisomerase) needed to copy and repair DNA, killing a wide range of bacteria.
In practice
In practice fluoroquinolones are reserved rather than first-line: regulators have restricted them because of rare but serious and sometimes long-lasting effects on tendons, muscles, nerves and the nervous system. Use them only when recommended for the specific infection, avoid in those at higher tendon risk (older age, steroids), counsel patients to stop and seek advice at the first sign of tendon pain, and remember the QT and interaction cautions.
Examples
Practical use
How to take it & use it well
- Take each dose with a full glass of water and keep well hydrated through the day.
- Separate this antibiotic from antacids, and from milk and dairy, as well as iron or calcium supplements, leaving a clear gap so the antibiotic is absorbed properly.
- Complete the full course as prescribed even if you feel better, unless told to stop because of a side effect.
- Stay out of strong sunlight and use sun protection, as your skin can burn more easily on these antibiotics.
- Stop the antibiotic and seek advice straight away if you notice tendon pain or swelling, new tingling or numbness, or unusual mood changes.
Common uses
- Specific resistant or complicated infections where recommended
- Some urinary, respiratory and GI infections per guidance
Monitoring
- Appropriateness versus alternatives before prescribing
- Tendon, neurological and psychiatric symptoms
- QT where risk factors exist
Weighing it up
Advantages & disadvantages
Advantages
- They are effective against a broad range of bacteria, including some that resist other antibiotics.
- They are well absorbed by mouth, so tablets can often replace the need for an intravenous drip.
- They reach high levels in tissues such as the urinary tract, making them useful for certain hard-to-treat infections.
- A short course can clear some infections quickly when used appropriately.
Disadvantages
- They carry a rare but serious risk of tendon inflammation or rupture, particularly of the Achilles tendon.
- Nerve damage causing lasting tingling, numbness or weakness has been reported, sometimes after only a few doses.
- Because of these risks, UK guidance restricts them to situations where other antibiotics are unsuitable.
- They can occasionally trigger anxiety, low mood, confusion or disturbed sleep.
Key safety principles
What to watch for
- Rare but serious: tendon damage (including rupture), and effects on muscles, joints and the nervous system that can be long-lasting — stop at the first sign and seek advice.
- Higher tendon risk in older people and with corticosteroids.
- QT prolongation, reduced seizure threshold, and several interactions (e.g. with some antacids and other drugs).
Key interactions
What to avoid or check alongside
- Antacids, dairy products and iron or calcium supplements bind the antibiotic in the gut and greatly reduce its absorption if taken close together.
- Combining with warfarin can increase the blood-thinning effect and raise bleeding risk, so clotting may need checking.
- Taken with theophylline they can raise its levels and cause side effects such as a racing heart or seizures.
- Used with oral steroids the risk of tendon damage rises, especially in older people.
- Several drugs that affect heart rhythm can combine with these antibiotics to disturb the heart's electrical activity.
Patient & carer advice
- Stop and seek advice immediately if you get tendon pain or swelling, numbness, or mood changes
- Avoid heavy exercise during treatment
- Tell us about other medicines, including antacids and supplements
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Fluoroquinolones: frequently asked questions
Why are fluoroquinolones restricted in the UK?
Because they can rarely cause serious, sometimes lasting side effects affecting tendons, nerves and mental health, they are now reserved for infections where safer antibiotics cannot be used.
Can I take this antibiotic with milk or antacids?
Not at the same time. Dairy, antacids and iron or calcium supplements bind the medicine and stop it being absorbed, so leave a clear gap between them.
What tendon symptoms should I watch for?
Pain, swelling or stiffness in a tendon, often around the ankle or back of the heel. Stop the antibiotic, rest the limb and seek medical advice promptly.
Are these antibiotics safe in pregnancy?
They are generally avoided in pregnancy and breastfeeding unless there is no suitable alternative. Tell your prescriber if you are or might be pregnant.
Can fluoroquinolones affect my mood?
Occasionally they can cause anxiety, low mood, confusion or sleep problems. If you notice new mental health changes, contact your prescriber.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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