Ciprofloxacin
Ciprofloxacin is a fluoroquinolone antibiotic used to treat a range of bacterial infections including urinary tract infections, respiratory infections, gastrointestinal infections, bone and joint infections, and anthrax prophylaxis.
It works by inhibiting bacterial DNA gyrase and topoisomerase IV, preventing bacterial DNA replication.
Ciprofloxacin is a prescription-only medicine (POM) in the UK and should be reserved for infections where other antibiotics are unsuitable.
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Ciprofloxacin is a fluoroquinolone antibiotic widely used in the United Kingdom for the treatment of bacterial infections that cannot be adequately treated with other antibiotics.
It is effective against a broad range of Gram-negative and selected Gram-positive bacteria and achieves high tissue concentrations in the urinary tract, respiratory tract, gastrointestinal tract, bone, and prostate.
Ciprofloxacin is available as tablets (250 mg and 500 mg), oral suspension, and intravenous infusion, with the oral tablet being the most commonly prescribed formulation in community and outpatient settings.
Following EU-wide safety reviews in 2018 and 2019, the Medicines and Healthcare products Regulatory Agency (MHRA) issued strengthened warnings for all fluoroquinolone antibiotics, including ciprofloxacin.
These medicines are now restricted to infections where other appropriate antibiotics cannot be used, owing to the risk of serious, disabling, long-lasting, and potentially irreversible side effects affecting tendons, muscles, joints, and the nervous system.
This page provides a comprehensive clinical overview of ciprofloxacin including its mechanism of action, licensed indications, dosing, side effects, MHRA safety warnings, drug interactions, and how to obtain a prescription in the UK.
Important safety information about ciprofloxacin
Before reading further, note the following critical safety points. Ciprofloxacin is a prescription-only medicine (POM) and must only be prescribed when other suitable antibiotics are not appropriate.
- Stop ciprofloxacin immediately and contact your GP if you experience tendon pain, swelling, or inflammation (particularly in the Achilles tendon). Rest the affected limb until a diagnosis has been made.
- Stop ciprofloxacin and seek medical advice if you develop numbness, tingling, burning, or weakness in the hands or feet (possible peripheral neuropathy).
- Fluoroquinolone side effects affecting tendons, muscles, joints, and nerves can occur within hours to weeks of starting treatment and may persist after stopping the drug.
- Ciprofloxacin should not be prescribed for mild or self-limiting infections, prophylaxis of travellers' diarrhoea, or non-bacterial conditions.
How ciprofloxacin works: mechanism of action
Ciprofloxacin belongs to the fluoroquinolone class of antibiotics. It exerts its bactericidal effect by inhibiting two essential bacterial enzymes involved in DNA replication and repair.
DNA gyrase (topoisomerase II) is responsible for introducing negative supercoils into bacterial DNA, a process critical for DNA replication, transcription, and chromosome compaction.
Topoisomerase IV is required for the separation of replicated chromosomal DNA during cell division.
By inhibiting both enzymes simultaneously, ciprofloxacin prevents DNA replication, causes DNA fragmentation, and kills bacteria rapidly.
This dual-target mechanism contributes to the broad-spectrum activity of ciprofloxacin and reduces the likelihood of resistance developing through single mutations.
However, resistance has become an increasing concern globally, particularly among Escherichia coli and Pseudomonas aeruginosa.
Local antibiotic susceptibility data should be considered when prescribing ciprofloxacin, and cultures should be obtained where possible before initiating therapy for serious infections.
Spectrum of activity
Ciprofloxacin has excellent activity against most aerobic Gram-negative bacteria including Escherichia coli, Klebsiella species, Proteus mirabilis, Enterobacter species, Serratia marcescens, Salmonella species, Shigella species, Campylobacter jejuni, and Pseudomonas aeruginosa.
It has moderate activity against some Gram-positive organisms including Staphylococcus aureus (methicillin-sensitive) and limited activity against Streptococcus pneumoniae.
It has good activity against atypical organisms such as Legionella pneumophila, Mycoplasma, and Chlamydia. It is not reliably active against anaerobes or methicillin-resistant Staphylococcus aureus (MRSA).
Licensed indications in the UK
Ciprofloxacin is licensed in the UK for the treatment of the following infections when caused by susceptible organisms and when other appropriate antibiotics cannot be used.
Urinary tract infections including acute uncomplicated cystitis, complicated UTI, pyelonephritis, and chronic bacterial prostatitis.
Respiratory tract infections including acute exacerbation of chronic obstructive pulmonary disease (COPD), lower respiratory tract infections caused by Gram-negative bacteria, and Pseudomonas aeruginosa infections in cystic fibrosis.
Acute sinusitis. Acute otitis media. Gastrointestinal infections including salmonellosis, shigellosis, travellers' diarrhoea, and typhoid fever. Bone and joint infections. Skin and soft tissue infections.
Inhalational anthrax post-exposure prophylaxis and treatment.
NICE and PHE (now UKHSA) antimicrobial prescribing guidelines recommend ciprofloxacin as a second-line or alternative agent for most of these indications.
For uncomplicated lower UTI in women, first-line antibiotics include nitrofurantoin, trimethoprim, and pivmecillinam.
Ciprofloxacin should be reserved for cases where these are unsuitable due to allergy, resistance, or contraindication.
Dosage and administration
Dosing varies by infection type and severity. For uncomplicated lower UTI: 250 mg twice daily for 3 days.
For complicated UTI or pyelonephritis: 500 mg twice daily for 7 to 14 days. For chronic bacterial prostatitis: 500 mg twice daily for 28 days.
For lower respiratory tract infections: 500 mg twice daily for 7 to 14 days. For acute exacerbation of COPD: 500 mg twice daily for 5 to 10 days.
For acute sinusitis: 500 mg twice daily for 10 days.
For bone and joint infections: 500 mg to 750 mg twice daily for 4 to 6 weeks (or up to 3 months for osteomyelitis).
For gastrointestinal infections: 500 mg twice daily for 1 to 5 days. For anthrax prophylaxis: 500 mg twice daily for 60 days.
Tablets should be swallowed whole with a generous amount of water. They may be taken with or without food.
Avoid concurrent administration with dairy products, calcium-fortified beverages, antacids containing aluminium, magnesium, or calcium, iron supplements, zinc supplements, or sucralfate.
These substances form insoluble chelate complexes with ciprofloxacin, substantially reducing oral bioavailability. Take ciprofloxacin at least 2 hours before or 6 hours after these products.
Renal dose adjustment
For patients with creatinine clearance between 30 and 60 mL/min, no routine dose adjustment is required for most indications, but monitoring for adverse effects is advised.
For creatinine clearance below 30 mL/min, the daily dose should be halved (e.g. 250 mg twice daily rather than 500 mg).
Specific guidance for patients on dialysis is available in the Summary of Product Characteristics. Adequate hydration should be maintained to reduce the risk of crystalluria.
MHRA safety warnings for fluoroquinolones
In 2018 and 2019, the European Medicines Agency (EMA) completed a review of the safety of fluoroquinolone and quinolone antibiotics.
The resulting regulatory action, enforced in the UK by the MHRA, included several key changes. Fluoroquinolones should not be prescribed for mild or self-limiting infections.
They should not be used for non-bacterial conditions or for prophylaxis of travellers' diarrhoea.
Patients must be informed about the risk of disabling, long-lasting, and potentially irreversible effects on tendons, muscles, joints, and the nervous system.
Treatment should be stopped at the first sign of tendon pain, peripheral neuropathy, or CNS effects.
Special caution is required in elderly patients, those with renal impairment, organ transplant recipients, and those treated with corticosteroids.
These restrictions reflect reports of tendon rupture (particularly Achilles tendon), peripheral neuropathy, psychiatric disturbances, aortic aneurysm and dissection, and other musculoskeletal and neurological effects that in some patients persisted for months or years after discontinuation.
Healthcare professionals are encouraged to discuss these risks with patients before prescribing and to report suspected adverse reactions via the MHRA Yellow Card scheme.
Side effects of ciprofloxacin
Common side effects
The most frequently reported adverse effects are gastrointestinal: nausea (affecting approximately 5% of patients), diarrhoea (approximately 3%), vomiting, abdominal pain, and dyspepsia.
Rash occurs in approximately 1 to 2% of patients. Mild elevation of liver transaminases (ALT, AST) is relatively common and usually resolves without intervention.
These effects are generally dose-related and resolve after completion of the course.
Musculoskeletal side effects
Tendinitis and tendon rupture are the most clinically significant musculoskeletal risks. The Achilles tendon is most frequently affected, but any tendon can be involved.
Tendinitis may present as pain, swelling, or stiffness, and tendon rupture may occur during or up to several months after treatment.
Risk factors include age over 60, concurrent corticosteroid use, renal impairment, and organ transplantation. Arthralgia and myalgia have also been reported.
Stop ciprofloxacin and rest the affected limb at the first sign of tendon symptoms.
Neurological and psychiatric side effects
Ciprofloxacin can cause CNS effects including headache, dizziness, insomnia, and, less commonly, tremor, seizures (particularly in patients with a history of epilepsy), peripheral neuropathy (numbness, tingling, burning, weakness in extremities), anxiety, depression, confusion, and psychotic reactions including hallucinations.
Peripheral neuropathy may develop within days of starting treatment and may be irreversible. Discontinue ciprofloxacin immediately if neurological symptoms occur.
Other notable side effects
Photosensitivity (exaggerated sunburn reaction) may occur during and for 48 hours after treatment. QT prolongation is a recognised risk, particularly in patients with predisposing conditions.
Clostridioides difficile-associated diarrhoea may develop during or after antibiotic use. Hypersensitivity reactions ranging from mild rash to severe anaphylaxis have been reported.
Haemolytic anaemia may occur in patients with G6PD deficiency. Very rarely, aortic aneurysm and dissection have been reported, predominantly in elderly patients.
When to seek medical advice
Contact your GP or call NHS 111 if you experience tendon pain or swelling, numbness or tingling in the hands or feet, persistent or worsening diarrhoea (particularly with blood or mucus), mood changes, or a skin rash during treatment.
Seek emergency care (call 999 or attend A&E) if you develop signs of severe allergic reaction (facial swelling, throat tightness, difficulty breathing), seizures, chest or back pain (possible aortic emergency), or inability to walk due to tendon pain.
Report any suspected adverse reactions via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk .
Drug interactions
Ciprofloxacin has several clinically significant drug interactions. Tizanidine is contraindicated due to markedly increased tizanidine plasma levels and risk of severe hypotension and sedation.
Theophylline levels are increased by ciprofloxacin, potentially to toxic levels; monitoring of theophylline concentrations is required if concurrent use is necessary.
Warfarin anticoagulant effect may be enhanced; INR should be monitored closely. Methotrexate clearance may be reduced, increasing the risk of methotrexate toxicity.
Ciclosporin levels may be increased, requiring monitoring of renal function. Phenytoin levels may be altered (increased or decreased).
NSAIDs may increase the risk of CNS stimulation and seizures when combined with fluoroquinolones.
Antacids, iron, calcium, magnesium, aluminium, and zinc preparations substantially reduce ciprofloxacin absorption and must be separated in dosing time.
Who should not take ciprofloxacin
Ciprofloxacin is contraindicated in patients with known hypersensitivity to ciprofloxacin, any other fluoroquinolone, or any of the excipients. It is contraindicated in concurrent use with tizanidine.
It should not be used in patients with a history of tendon disorders related to fluoroquinolone use.
It is generally avoided in children and adolescents under 18 due to the risk of cartilage damage (except for specific licensed indications such as cystic fibrosis, complicated UTI, and anthrax).
It is avoided in pregnancy and breastfeeding unless no safer alternative exists.
Special caution is required in patients with myasthenia gravis (fluoroquinolones may exacerbate weakness and should be avoided if possible), epilepsy or conditions predisposing to seizures, known QT prolongation or concurrent QT-prolonging medications, G6PD deficiency, and aortic aneurysm or family history of aneurysm.
How to get ciprofloxacin in the UK
Ciprofloxacin is a prescription-only medicine (POM) in the UK.
It can be prescribed by your GP, hospital doctor, or an authorised online prescriber following a clinical assessment that determines ciprofloxacin is the most appropriate antibiotic for your infection.
Prescribers should follow local and national antimicrobial guidelines, obtain cultures where possible, and document the rationale for choosing a fluoroquinolone over first-line alternatives.
Ciprofloxacin is available generically at low cost. Brand-name products such as Ciproxin are also available but are less commonly prescribed.
The standard NHS prescription charge in England is currently 9.90 pounds per item; prescriptions are free in Scotland, Wales, and Northern Ireland.
Antimicrobial stewardship
Ciprofloxacin should be prescribed in accordance with antimicrobial stewardship principles.
These include using the narrowest-spectrum antibiotic effective for the infection, choosing the shortest appropriate course duration, obtaining cultures before starting treatment where feasible, switching from intravenous to oral therapy as soon as clinically appropriate, and reviewing the prescription at 48 to 72 hours against culture results.
Fluoroquinolone resistance among urinary and respiratory pathogens has increased in the UK, and indiscriminate use of these agents accelerates resistance and increases the risk of C. difficile infection.
NHS England and UKHSA publish quarterly antimicrobial resistance reports to guide local prescribing.
Sources
- Ciprofloxacin 500 mg Film-coated Tablets - Summary of Product Characteristics (EMC)
- Ciprofloxacin - British National Formulary (BNF)
- MHRA Drug Safety Update: Fluoroquinolone antibiotics - restrictions and precautions
- NICE NG109: Urinary tract infection (lower) - antimicrobial prescribing
- Ciprofloxacin - NHS
- MHRA Yellow Card Scheme
Medical information
Ciprofloxacin is a second-generation fluoroquinolone with broad-spectrum bactericidal activity against Gram-negative and some Gram-positive organisms. It exerts its antimicrobial effect by inhibiting two essential bacterial enzymes: DNA gyrase (topoisomerase II), which is critical for DNA supercoiling and replication, and topoisomerase IV, which is required for chromosome separation. This dual mechanism results in rapid bactericidal activity and a low propensity for single-step resistance compared with agents targeting a single enzyme. Ciprofloxacin achieves high concentrations in urine, respiratory secretions, bone, and prostate tissue, making it effective for infections at these sites. Following MHRA safety reviews (2018-2019) and EU referral, fluoroquinolones are now restricted to situations where other appropriate antibiotics cannot be used, owing to the risk of disabling, long-lasting, and potentially irreversible side effects affecting tendons, muscles, joints, and the nervous system.Dosage guidance
Ciprofloxacin dosing depends on the type and severity of infection. The following are standard oral doses for adults as recommended in the BNF and Summary of Product Characteristics. For uncomplicated lower urinary tract infections (acute cystitis): 250 mg twice daily for 3 days. For complicated UTI or upper UTI (pyelonephritis): 500 mg twice daily for 7 to 14 days. For acute bacterial prostatitis: 500 mg twice daily for 28 days. For lower respiratory tract infections: 500 mg twice daily for 7 to 14 days. For acute exacerbation of chronic bronchitis: 500 mg twice daily for 7 to 14 days. For acute sinusitis: 500 mg twice daily for 10 days. For bone and joint infections: 500 mg to 750 mg twice daily for up to 3 months, depending on severity. For gastrointestinal infections (including travellers' diarrhoea): 500 mg twice daily for 1 to 5 days depending on the pathogen. For anthrax post-exposure prophylaxis: 500 mg twice daily for 60 days. Tablets should be swallowed whole with plenty of fluid. They may be taken with or without food, but should not be taken with dairy products or calcium-fortified drinks, as calcium can reduce absorption. Dose adjustment is required in renal impairment. For creatinine clearance 30 to 60 mL/min, no routine adjustment is needed for most indications, though monitoring is advised. For creatinine clearance below 30 mL/min, the dose should be halved. For patients on peritoneal dialysis or haemodialysis, specific dosing guidance should be followed per the SmPC. Ciprofloxacin should be taken at least 2 hours before or 6 hours after products containing magnesium, aluminium, iron, calcium, or zinc (including antacids, mineral supplements, and sucralfate), as these form insoluble chelates that substantially reduce absorption. It is important to complete the full prescribed course even if symptoms improve before the course is finished, to reduce the risk of resistance.Side effects and warnings
Common side effects of ciprofloxacin include nausea, diarrhoea, vomiting, rash, and elevations in liver transaminases. These are generally mild and resolve after completion of the course. Uncommon side effects include headache, dizziness, sleep disturbance, taste disturbance, abdominal pain, flatulence, dyspepsia, joint pain, musculoskeletal pain, and fungal superinfection (including oral and vaginal candidiasis). Photosensitivity reactions may occur; avoid excessive sun exposure and do not use sunbeds during treatment and for 48 hours after stopping. Serious side effects requiring medical attention include tendon inflammation (tendinitis) and tendon rupture, particularly of the Achilles tendon. Risk is highest in patients over 60, those taking corticosteroids, and those with renal impairment or a history of organ transplantation. Stop ciprofloxacin and rest the affected limb if you experience tendon pain, swelling, or inflammation. Fluoroquinolones have been associated with peripheral neuropathy (numbness, tingling, burning, weakness in the extremities), psychiatric effects (anxiety, depression, confusion, hallucinations, psychotic reactions), and central nervous system effects including seizures, particularly in patients with a history of epilepsy or conditions predisposing to seizures. The MHRA has issued specific warnings about disabling, long-lasting, and potentially irreversible side effects affecting tendons, muscles, joints, and the nervous system. These can occur within hours to weeks of starting treatment and may persist after stopping. Clostridioides difficile-associated diarrhoea (CDAD) may occur during or after fluoroquinolone treatment. If severe diarrhoea develops, particularly with blood or mucus, stop ciprofloxacin and seek medical attention immediately. Very rarely, aortic aneurysm and dissection have been reported in association with fluoroquinolone use, particularly in elderly patients. Report suspected adverse reactions via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.Following EU-wide safety reviews in 2018 and 2019, the MHRA issued strengthened warnings for all fluoroquinolone antibiotics, including ciprofloxacin.
These antibiotics should be prescribed only when other commonly recommended antibiotics are inappropriate for the infection being treated.
Fluoroquinolones should not be used for mild or self-limiting infections (uncomplicated cystitis is an exception only when first-line agents such as nitrofurantoin, trimethoprim, or pivmecillinam are unsuitable), non-bacterial conditions, or prophylaxis of travellers' diarrhoea.
Ciprofloxacin should be avoided or used with extreme caution in the following groups: patients with a history of tendon disorders related to fluoroquinolone use; patients over 60 (higher tendon rupture risk); patients taking systemic corticosteroids concurrently; patients with renal impairment (increased tendon and CNS risk); organ transplant recipients (markedly increased tendon rupture risk); patients with a history of epilepsy or lowered seizure threshold; patients with myasthenia gravis (fluoroquinolones may exacerbate muscle weakness); and patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency (risk of haemolytic anaemia).
Ciprofloxacin prolongs the QT interval.
It should not be used in patients with congenital or documented acquired QT prolongation, uncorrected electrolyte disturbances (particularly hypokalaemia and hypomagnesaemia), or those taking other QT-prolonging medications.
Ciprofloxacin increases theophylline and caffeine plasma levels and may increase the anticoagulant effect of warfarin. Concurrent tizanidine use is contraindicated.
Monitoring of INR is recommended if ciprofloxacin is prescribed alongside warfarin or acenocoumarol.
Patients should be advised to stay well hydrated during treatment to reduce the risk of crystalluria.
Ciprofloxacin may impair the ability to drive or operate machinery due to CNS effects. Avoid excessive sun exposure during treatment.
Discontinue ciprofloxacin immediately if signs of tendinitis, peripheral neuropathy, or serious hypersensitivity reaction develop, and seek medical advice promptly.
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