Ciprofloxacin
Fluoroquinolone antibiotic for bacterial infections
📊 Quick Facts: Ciprofloxacin
💡 Key Takeaways About Ciprofloxacin
- Broad-spectrum antibiotic: Ciprofloxacin treats a wide range of bacterial infections including urinary tract, respiratory, gastrointestinal, and skin infections
- FDA Black Box Warning: Fluoroquinolones carry serious risks of tendinitis, tendon rupture, peripheral neuropathy, and CNS effects that may be irreversible
- Drug interactions matter: Do not take with tizanidine; calcium, antacids, and iron supplements reduce absorption significantly
- Complete the full course: Stopping early increases antibiotic resistance and risk of infection recurrence
- Avoid in pregnancy: Ciprofloxacin is not recommended during pregnancy or breastfeeding due to potential harm to the developing child
What Is Ciprofloxacin and What Is It Used For?
Ciprofloxacin is a fluoroquinolone antibiotic that kills bacteria by inhibiting the enzymes DNA gyrase and topoisomerase IV, which are essential for bacterial DNA replication. It is prescribed for urinary tract infections, respiratory infections, gastrointestinal infections, skin infections, bone and joint infections, and post-exposure prophylaxis against anthrax.
Ciprofloxacin belongs to the fluoroquinolone class of antibiotics, which are among the most widely prescribed antibacterial agents worldwide. It was first approved for clinical use in 1987 and has since become a cornerstone in the treatment of many serious bacterial infections. The drug works by targeting two critical bacterial enzymes — DNA gyrase (topoisomerase II) and topoisomerase IV — which are essential for bacterial DNA replication, transcription, repair, and recombination. By inhibiting these enzymes, ciprofloxacin causes bacterial cell death, making it a bactericidal rather than merely bacteriostatic antibiotic.
Ciprofloxacin demonstrates broad-spectrum activity against many gram-negative bacteria, including Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella, and Shigella species. It also has activity against some gram-positive organisms, including certain strains of Staphylococcus aureus. However, it has limited activity against anaerobic bacteria and is not effective against viral infections such as the common cold or influenza.
Due to the risk of serious adverse effects, major regulatory agencies including the EMA and the FDA have issued guidance that fluoroquinolones, including ciprofloxacin, should generally be reserved for infections where other antibiotic options are not suitable. This is particularly important for uncomplicated infections where safer alternatives exist.
Uses in Adults
Ciprofloxacin is approved for the treatment of the following bacterial infections in adults:
- Urinary tract infections — including complicated and uncomplicated UTIs, and acute pyelonephritis (kidney infections)
- Respiratory tract infections — particularly lower respiratory tract infections in patients with chronic obstructive pulmonary disease (COPD) or cystic fibrosis
- Ear and sinus infections — chronic or recurrent otitis media and sinusitis
- Gastrointestinal infections — including traveller's diarrhea caused by susceptible organisms, and intra-abdominal infections (usually in combination with metronidazole)
- Skin and soft tissue infections — caused by susceptible gram-negative organisms
- Bone and joint infections — including osteomyelitis caused by gram-negative bacteria
- Genital tract infections — including gonococcal urethritis and cervicitis
- Prevention of meningococcal disease — prophylaxis after exposure to Neisseria meningitidis
- Inhalational anthrax — post-exposure prophylaxis and treatment
Ciprofloxacin may also be used in patients with a low white blood cell count (neutropenia) who develop fever suspected to be caused by a bacterial infection. In cases of severe infection or mixed bacterial infections, additional antibiotics may be prescribed alongside ciprofloxacin.
Uses in Children and Adolescents
In children and adolescents, ciprofloxacin use is more restricted and should be supervised by a medical specialist. Approved paediatric indications include:
- Acute pulmonary exacerbations in children and adolescents with cystic fibrosis caused by Pseudomonas aeruginosa
- Complicated urinary tract infections, including pyelonephritis
- Post-exposure prophylaxis for inhalational anthrax
The restricted use in children is due to concerns about potential cartilage toxicity observed in juvenile animal studies. However, when the benefit outweighs the risk — particularly in life-threatening or serious infections — ciprofloxacin may be used under specialist supervision.
What Should You Know Before Taking Ciprofloxacin?
Do not take ciprofloxacin if you are allergic to any quinolone antibiotic or if you are taking tizanidine. Inform your doctor about any history of tendon problems, epilepsy, kidney disease, heart rhythm disorders, diabetes, or myasthenia gravis. Fluoroquinolones carry an FDA/EMA warning for potentially disabling and irreversible side effects affecting tendons, nerves, and the central nervous system.
Contraindications
You must not take ciprofloxacin in the following situations:
- Allergy to ciprofloxacin or other quinolones — if you have ever had an allergic reaction to ciprofloxacin, moxifloxacin, norfloxacin, ofloxacin, levofloxacin, or nalidixic acid
- Concurrent use with tizanidine — co-administration is contraindicated due to significant drug interaction causing hypotension and sedation
- Previous serious adverse reaction to any fluoroquinolone — you should not take any fluoroquinolone if you have previously experienced tendon damage, neuropathy, or other serious side effects from a quinolone antibiotic
Fluoroquinolones, including ciprofloxacin, are associated with disabling and potentially irreversible serious adverse reactions that can occur together. These include tendinitis and tendon rupture, peripheral neuropathy, and central nervous system effects. Discontinue ciprofloxacin immediately if any of these serious adverse reactions occur, and contact your healthcare provider.
Warnings and Precautions
Before starting ciprofloxacin, tell your doctor if you have or have ever had any of the following conditions, as your treatment may need to be adjusted:
- Kidney problems — dose adjustment may be necessary
- Epilepsy or other neurological conditions — ciprofloxacin may lower the seizure threshold
- Previous tendon problems with any quinolone antibiotic
- Diabetes — ciprofloxacin can cause both hyperglycaemia and hypoglycaemia; blood glucose should be monitored carefully
- Myasthenia gravis — symptoms may worsen during treatment
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency — risk of haemolytic anaemia
- Heart rhythm disorders — particularly prolonged QT interval, bradycardia, electrolyte imbalances (low potassium or magnesium), heart failure, or history of heart attack
- Aortic aneurysm or dissection — or family history of these conditions, or risk factors such as connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome), Takayasu arteritis, giant cell arteritis, Behcet's disease, hypertension, or atherosclerosis
- Heart valve disease — known regurgitation or prolapse of heart valves
Contact your doctor immediately and stop taking ciprofloxacin if you experience: tendon pain or swelling (especially in the Achilles tendon), tingling, numbness or burning in hands or feet, severe diarrhea (particularly if bloody), sudden severe abdominal, chest or back pain, shortness of breath when lying down, or signs of a severe allergic reaction (throat swelling, difficulty breathing, skin rash).
Long-lasting Adverse Reactions
Fluoroquinolone antibiotics, including ciprofloxacin, have been associated with very rare but potentially serious adverse reactions that may be long-lasting (months to years), disabling, or potentially permanent. These include pain in tendons, muscles, and joints of the arms and legs, difficulty walking, abnormal sensations such as tingling, prickling, numbness or burning (paraesthesia), sensory disturbances including impaired vision, taste, smell, and hearing, depression, impaired memory, severe fatigue, and severe sleep disturbances.
If you experience any of these adverse reactions after taking ciprofloxacin, contact your doctor immediately before continuing treatment. You and your doctor will decide whether to continue or switch to a different type of antibiotic.
Pregnancy and Breastfeeding
Ciprofloxacin should be avoided during pregnancy. Animal studies have shown potential for damage to weight-bearing joints in the developing foetus, and there is insufficient data in humans to confirm safety. If you are pregnant, think you may be pregnant, or are planning to have a baby, consult your healthcare provider before taking this medicine.
Ciprofloxacin should not be used during breastfeeding, as the drug passes into breast milk and may be harmful to the nursing infant. Your healthcare provider may recommend an alternative antibiotic if treatment is needed during breastfeeding.
Driving and Operating Machinery
Ciprofloxacin may cause dizziness, reduce alertness, and affect reaction time. Do not drive or operate machinery until you know how ciprofloxacin affects you. If you experience any neurological side effects, refrain from these activities and consult your doctor.
How Does Ciprofloxacin Interact with Other Drugs?
Ciprofloxacin has clinically significant interactions with many medications. It must not be taken with tizanidine. It increases levels of theophylline, caffeine, warfarin, duloxetine, and several other drugs. Antacids, iron supplements, and calcium-rich products taken separately from meals can significantly reduce ciprofloxacin absorption.
Ciprofloxacin is a moderate inhibitor of the cytochrome P450 enzyme CYP1A2 and can affect the metabolism of many other drugs. Understanding these interactions is critical for safe and effective treatment. Always inform your doctor about all medications, supplements, and herbal products you are taking.
Major Interactions (Avoid Combination)
| Drug | Risk | Action |
|---|---|---|
| Tizanidine | Severe hypotension and sedation; up to 10-fold increase in tizanidine levels | Absolutely contraindicated |
| Theophylline | Increased theophylline levels; risk of seizures, nausea, cardiac arrhythmias | Monitor levels closely; dose reduction may be needed |
| Warfarin / Vitamin K antagonists | Enhanced anticoagulant effect; increased bleeding risk | Monitor INR frequently; adjust warfarin dose |
| Methotrexate | Increased methotrexate toxicity due to reduced renal clearance | Monitor closely; avoid if possible |
| Cyclosporine | Increased nephrotoxicity; elevated cyclosporine levels | Monitor kidney function and cyclosporine levels |
| QT-prolonging drugs | Additive risk of cardiac arrhythmias (antiarrhythmics, certain antipsychotics, tricyclic antidepressants) | Avoid combination or monitor ECG |
Moderate Interactions (Use with Caution)
| Drug | Effect | Recommendation |
|---|---|---|
| Phenytoin | Altered phenytoin levels (increased or decreased) | Monitor phenytoin levels |
| Duloxetine | Up to 5-fold increase in duloxetine exposure | Avoid combination if possible |
| Ropinirole | Increased ropinirole levels; risk of side effects | Monitor and consider dose reduction |
| Clozapine / Olanzapine | Increased plasma concentrations of antipsychotics | Monitor for side effects |
| Caffeine | Increased caffeine levels; enhanced stimulatory effects | Reduce caffeine intake during treatment |
| Sildenafil | Approximately 2-fold increase in sildenafil exposure | Consider lower sildenafil dose |
| Lidocaine (IV) | Increased lidocaine levels | Monitor cardiac function |
Drugs That Reduce Ciprofloxacin Absorption
Certain medications and supplements can significantly reduce the absorption of ciprofloxacin from the gastrointestinal tract, potentially making the antibiotic less effective. These include:
- Antacids containing aluminium, magnesium, or calcium
- Sucralfate (for stomach ulcers)
- Mineral supplements containing iron, zinc, or calcium
- Phosphate binders such as sevelamer or lanthanum carbonate
- Omeprazole and other proton pump inhibitors (may reduce absorption)
- Didanosine (HIV medication)
If you need to take any of these medications, take ciprofloxacin approximately 2 hours before or at least 4 hours after them. This timing separation is essential to ensure adequate absorption of the antibiotic.
Ciprofloxacin with Food and Drink
Ciprofloxacin can be taken with or without food. However, there is an important nuance regarding dairy products and calcium-fortified beverages. When ciprofloxacin tablets are taken as part of a meal that includes dairy products (such as milk or yoghurt), the calcium present does not significantly affect drug absorption. However, when dairy products or calcium-rich beverages are consumed separately from meals, they can substantially reduce ciprofloxacin absorption.
Therefore, ciprofloxacin tablets should be taken either 1–2 hours before or at least 4 hours after dairy products or calcium-rich drinks consumed outside of mealtimes.
What Is the Correct Dosage of Ciprofloxacin?
The standard adult dose of ciprofloxacin is 250–750 mg twice daily, depending on the type and severity of infection. Treatment typically lasts 5–21 days. Dosage must be adjusted in patients with kidney impairment. Always take ciprofloxacin exactly as prescribed by your doctor.
Your doctor will determine the exact dose, frequency, and duration of treatment based on the type and severity of your infection, your kidney function, and other individual factors. It is essential to follow the prescribed regimen exactly and to complete the full course of treatment, even if you start feeling better after a few days.
Adults
| Infection | Dose | Frequency | Duration |
|---|---|---|---|
| Uncomplicated UTI | 250–500 mg | Twice daily | 3 days |
| Complicated UTI / Pyelonephritis | 500 mg | Twice daily | 7–14 days |
| Lower respiratory tract | 500–750 mg | Twice daily | 7–14 days |
| Chronic sinusitis / Otitis media | 500–750 mg | Twice daily | 7–14 days |
| GI infections | 500 mg | Twice daily | 5–7 days |
| Bone & joint infections | 500–750 mg | Twice daily | Up to 3 months |
| Skin & soft tissue | 500–750 mg | Twice daily | 7–14 days |
| Anthrax (post-exposure) | 500 mg | Twice daily | 60 days |
Children
Dosing in children is based on body weight and must be determined by a specialist physician. The typical dose ranges from 10–20 mg/kg body weight per day, divided into two doses, with a maximum of 750 mg per dose. Children with cystic fibrosis may require higher doses. An oral suspension formulation (50 mg/ml) is available for children who cannot swallow tablets.
Elderly Patients
Elderly patients should receive the appropriate dose based on the severity of infection and their kidney function. Older adults are at increased risk for tendon disorders and should be closely monitored during treatment. Co-administration with corticosteroids should be avoided if possible, as this combination further increases the risk of tendon rupture.
Patients with Kidney Impairment
If you have reduced kidney function, your doctor will adjust your dose accordingly, as ciprofloxacin is partially excreted through the kidneys. Inadequate dose adjustment can lead to drug accumulation and increased risk of side effects. Inform your doctor about any kidney problems before starting treatment.
How to Take Ciprofloxacin
- Swallow tablets whole with plenty of water — do not chew them
- Tablets have a score line to help you break them if you have difficulty swallowing, but they should not be crushed
- Try to take your doses at the same time each day
- You can take ciprofloxacin with or between meals
- Drink plenty of fluids throughout treatment to maintain adequate hydration and prevent crystal formation in the urine
Missed Dose
If you miss a dose, take it as soon as you remember — provided there are 6 or more hours until your next scheduled dose. If fewer than 6 hours remain, skip the missed dose and continue with your regular schedule. Never take a double dose to compensate for a missed one.
Overdose
If you take more ciprofloxacin than prescribed, seek medical help immediately. Bring the remaining tablets and packaging to show the doctor. Symptoms of overdose may include dizziness, tremor, headache, fatigue, seizures, hallucinations, confusion, abdominal discomfort, liver and kidney problems, and crystals or blood in the urine. Treatment is supportive, and there is no specific antidote.
It is essential to complete the full prescribed course of ciprofloxacin, even if you start feeling better after a few days. Stopping treatment early can lead to inadequate treatment of the infection, symptom recurrence, and the development of antibiotic-resistant bacteria. Only stop treatment if instructed to do so by your doctor.
What Are the Side Effects of Ciprofloxacin?
Common side effects include nausea, diarrhea, and joint pain (in children). Serious but rare side effects include tendon rupture, peripheral neuropathy, CNS effects (seizures, psychosis), severe allergic reactions, liver damage, and aortic aneurysm. Some serious side effects can be long-lasting or permanent.
Like all medicines, ciprofloxacin can cause side effects, although not everyone will experience them. Some side effects are serious and require immediate medical attention. The following overview groups side effects by how frequently they occur, based on clinical studies and post-marketing surveillance data.
- Severe allergic reaction (difficulty breathing, facial or throat swelling, skin rash with blistering)
- Tendon pain, swelling, or rupture (especially Achilles tendon)
- Tingling, numbness, or burning in hands or feet (signs of neuropathy)
- Severe or bloody diarrhea (may indicate Clostridioides difficile colitis)
- Sudden severe pain in abdomen, chest, or back (may indicate aortic dissection)
- Signs of liver damage (jaundice, dark urine, loss of appetite)
Common
- Nausea
- Diarrhea
- Joint pain (in children)
Uncommon
- Fungal superinfections (e.g., oral or vaginal thrush)
- Increased white blood cell count (eosinophilia, leukocytosis)
- Decreased appetite
- Hyperactivity or restlessness
- Headache, dizziness, sleep disturbances, taste changes
- Vomiting, abdominal pain, indigestion, flatulence
- Elevated liver enzymes (transaminases, bilirubin, alkaline phosphatase)
- Skin rash, itching, urticaria (hives)
- Joint pain (in adults), musculoskeletal pain, weakness, fever
- Impaired kidney function
Rare
- Severe or bloody diarrhea (pseudomembranous colitis)
- Anaemia, thrombocytopenia (low platelet count)
- Blood sugar disturbances (hyperglycaemia, hypoglycaemia)
- Confusion, disorientation, anxiety, nightmares, depression, hallucinations
- Seizures (including status epilepticus)
- Paraesthesia (tingling, numbness), dysaesthesia, tremor
- Vertigo, tinnitus, hearing loss
- Visual disturbances (colour vision changes, blurred or double vision)
- Rapid heartbeat (tachycardia), low blood pressure, fainting
- Shortness of breath, asthmatic symptoms
- Liver damage including hepatitis, jaundice; very rarely liver necrosis
- Photosensitivity (increased sensitivity to sunlight)
- Kidney failure, blood or crystals in urine
- Tendinitis and tendon rupture (especially Achilles tendon)
- Increased infections due to low white blood cell count (agranulocytosis)
- Severe allergic reactions including anaphylaxis and angioedema
- Muscle weakness, joint inflammation, increased muscle tone
Very Rare or Frequency Unknown
- Severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Peripheral neuropathy (potentially permanent nerve damage)
- Pancreatitis
- Aortic aneurysm and dissection
- Heart valve regurgitation
- Prolonged QT interval (heart rhythm disorder)
- DRESS syndrome (drug reaction with eosinophilia and systemic symptoms)
- Hypoglycaemic coma (severe drop in blood sugar)
- Psychotic reactions including suicidal thoughts
- SIADH (syndrome of inappropriate antidiuretic hormone secretion)
- Worsening of myasthenia gravis symptoms
- Mania or hypomania
In very rare cases, adverse effects including tendon inflammation, tendon rupture, joint pain, limb pain, difficulty walking, paraesthesia, neuropathy, depression, fatigue, memory impairment, and impaired hearing, vision, taste, and smell have been reported to persist for months to years, or even become permanent. These effects have been associated with quinolone and fluoroquinolone antibiotics regardless of pre-existing risk factors. If you experience any persistent symptoms, consult your doctor promptly.
How Should You Store Ciprofloxacin?
Store ciprofloxacin at room temperature, protected from moisture and direct light. Keep out of sight and reach of children. Do not use after the expiry date printed on the packaging. Do not dispose of medicines in wastewater or household waste — return unused medicines to a pharmacy for safe disposal.
Store ciprofloxacin tablets in their original packaging to protect them from moisture. No special temperature storage conditions are required — standard room temperature is appropriate. Always check the expiry date on the blister pack or carton before taking the medicine. The expiry date refers to the last day of the stated month.
Keep all medicines out of the sight and reach of children. Do not dispose of medicines via household waste or wastewater. Instead, return unused or expired medicines to your local pharmacy for proper disposal. These measures help protect the environment.
What Does Ciprofloxacin Contain?
Each ciprofloxacin tablet contains ciprofloxacin as the active ingredient (as ciprofloxacin hydrochloride), available in 100 mg, 250 mg, and 500 mg strengths. Inactive ingredients include microcrystalline cellulose, maize starch, crospovidone, pregelatinised starch, colloidal anhydrous silica, and magnesium stearate, with a film coating containing hypromellose and titanium dioxide.
Active Ingredient
The active substance is ciprofloxacin, present as ciprofloxacin hydrochloride. Available strengths:
- 100 mg tablets — white, round, film-coated
- 250 mg tablets — white, round, film-coated with score line
- 500 mg tablets — white, capsule-shaped, film-coated with score line
- Oral suspension — 50 mg/ml (for patients who cannot swallow tablets)
- Eye drops — 3 mg/ml solution (for ophthalmic use only)
Inactive Ingredients (Excipients)
The tablet core contains: microcrystalline cellulose, maize starch, crospovidone, pregelatinised starch, colloidal anhydrous silica, and magnesium stearate. The film coating contains: hypromellos, titanium dioxide (E171), polydextrose, glycerol triacetate, and macrogol.
The score line on the 250 mg, 500 mg, and 750 mg tablets is intended to help break the tablet if you have difficulty swallowing the whole tablet. Tablets are available in blister packs of 6, 8, 10, 12, 14, 16, 20, 100, and 120 tablets. Not all pack sizes may be marketed in every country.
Why Is Responsible Antibiotic Use Important?
Antibiotics like ciprofloxacin are only effective against bacterial infections, not viruses. Misuse and overuse of antibiotics drives antibiotic resistance, one of the greatest global health threats. Always follow the prescribed dose, dosing interval, and duration of treatment to preserve antibiotic effectiveness.
Antibiotic resistance is a growing global health crisis. The World Health Organization (WHO) has identified antimicrobial resistance as one of the top 10 global public health threats facing humanity. Bacteria that develop resistance to fluoroquinolones like ciprofloxacin become much harder to treat, requiring more expensive and potentially more toxic alternative antibiotics.
You can help combat antibiotic resistance by following these principles:
- Only use antibiotics when prescribed by a qualified healthcare provider
- Follow the prescribed dose and schedule exactly
- Complete the full course of treatment even if you feel better
- Never share your antibiotics with others — the antibiotic may not be appropriate for their condition
- Never use leftover antibiotics from a previous prescription
- Return unused antibiotics to a pharmacy for safe disposal
Remember that antibiotics are ineffective against viral infections such as colds, influenza, and most sore throats. Using antibiotics unnecessarily not only fails to help but actively contributes to the development of resistant bacteria that affect everyone.
Frequently Asked Questions About Ciprofloxacin
Medical References and Sources
This article is based on current medical research, official drug labelling, and international guidelines. All claims are supported by scientific evidence from peer-reviewed sources.
- European Medicines Agency (EMA). "Fluoroquinolone and quinolone antibiotics: PRAC recommends restrictions on use." (2018, updated 2023). EMA Referral Regulatory review of fluoroquinolone safety concerns.
- U.S. Food and Drug Administration (FDA). "FDA Drug Safety Communication: FDA updates warnings for fluoroquinolone antibiotics." (2016, updated 2018). FDA Safety Communication FDA Black Box Warning for fluoroquinolone antibiotics.
- World Health Organization (WHO). "WHO Model List of Essential Medicines – 23rd List." (2023). WHO Essential Medicines Ciprofloxacin listed as essential medicine for specific indications.
- British National Formulary (BNF). "Ciprofloxacin." NICE Evidence Services. BNF Monograph UK prescribing information and clinical guidance.
- Zhanel GG, et al. (2002). "A critical review of the fluoroquinolones: focus on respiratory infections." Drugs. 62(1):13-59. Comprehensive review of fluoroquinolone pharmacology and clinical use.
- Stahlmann R, Lode HM. (2013). "Risks associated with the therapeutic use of fluoroquinolones." Expert Opin Drug Saf. 12(4):497-505. Expert analysis of fluoroquinolone adverse effects.
Evidence grading: This article uses the GRADE framework (Grading of Recommendations Assessment, Development and Evaluation) for evidence-based medicine. Drug information is cross-referenced with official product labelling from multiple international regulatory agencies.
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