Ciprofloxacin: A Comprehensive Guide

Ciprofloxacin is a broad-spectrum antibiotic belonging to the fluoroquinolone class, widely used to treat various bacterial infections. Ciprofloxacin works by inhibiting bacterial DNA gyrase and topoisomerase IV—key enzymes involved in DNA replication. Thanks to its strong antimicrobial activity and availability in multiple formulations, Ciprofloxacin remains a cornerstone in modern antibacterial therapy.

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Uses of Ciprofloxacin

Ciprofloxacin is used in a wide range of infections including urinary tract infections (UTIs), respiratory tract infections, gastrointestinal infections like traveller’s diarrhoea, skin infections, and bone and joint infections. Ciprofloxacin is also an important treatment option in cases of anthrax exposure and certain multidrug-resistant infections.

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Dosage and Administration

Ciprofloxacin is usually prescribed orally or via intravenous infusion. The standard adult oral dose for uncomplicated UTIs is 250–500 mg twice daily for 3–7 days. For respiratory infections or more severe systemic infections, doses may range up to 750 mg twice daily. Intravenous formulations are generally administered at 200–400 mg every 12 hours, depending on severity and type of infection. Always take Ciprofloxacin with a full glass of water, and avoid dairy or calcium-rich supplements around the time of dosing.

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Dose Adjustment in Special Conditions

Renal Impairment:

Ciprofloxacin is partially excreted by the kidneys, so dosage adjustments are necessary in patients with reduced renal function. For creatinine clearance below 30 mL/min, a reduction to 250–500 mg once daily is often recommended.

Hepatic Impairment:

Though Ciprofloxacin undergoes hepatic metabolism, dose adjustment is usually not necessary in mild to moderate hepatic impairment. Caution is advised in severe cases.

Pregnancy and Lactation:

Ciprofloxacin is generally not recommended during pregnancy, particularly in the first trimester, due to concerns about cartilage damage in the fetus. During breastfeeding, caution should also be exercised, and alternative antibiotics are usually preferred.

Effects and Side Effects of Ciprofloxacin

Common side effects of Ciprofloxacin include nausea, diarrhoea, abdominal discomfort, and headache. Some patients may experience photosensitivity—hence sun protection is advised. Rare but serious effects include tendon rupture, peripheral neuropathy, QT interval prolongation, and CNS effects like confusion or hallucination, particularly in the elderly.

How Ciprofloxacin Works

Ciprofloxacin targets bacterial enzymes DNA gyrase and topoisomerase IV, crucial for DNA unwinding and replication. By inhibiting these, Ciprofloxacin halts bacterial proliferation, making it bactericidal rather than just bacteriostatic.

Drug Combinations and Infusion Considerations

Ciprofloxacin is often combined with beta-lactams or metronidazole in polymicrobial infections. During IV infusion, Ciprofloxacin should be diluted properly (e.g., in 0.9% saline) and administered over 60 minutes to avoid venous irritation. Avoid administering with calcium-containing IV fluids or antacids simultaneously.

Presentation and Dosage Forms

Form	Strength	Route
Tablet	250 mg, 500 mg, 750 mg	Oral
Oral Suspension	250 mg/5 mL	Oral
IV Infusion	200 mg/100 mL, 400 mg/200 mL	Intravenous
Eye Drops	0.3%	Ophthalmic
Ear Drops	0.3%	Otic

Pharmacokinetics and Pharmacodynamics

Ciprofloxacin has good oral bioavailability (approximately 70%) and reaches peak plasma concentration in 1–2 hours. It is widely distributed in tissues and fluids. The drug has a half-life of about 4 hours and is eliminated via both renal and hepatic pathways.

Spectrum of Activity:

Ciprofloxacin is effective against Gram-negative organisms like E. coli, Klebsiella, Pseudomonas aeruginosa, and some Gram-positive bacteria like Staphylococcus aureus. However, resistance among Gram-positive organisms like Streptococcus pneumoniae is increasing.

Drug Interactions

Ciprofloxacin interacts with antacids, iron, and calcium supplements, which can reduce its absorption. It can enhance the effects of warfarin and increase serum levels of theophylline and caffeine. Caution is also advised with drugs prolonging the QT interval, such as amiodarone or erythromycin.

Comparison with Other Fluoroquinolones

Drug	Gram-negative Coverage	Gram-positive Coverage	Respiratory Activity	Half-life
Ciprofloxacin	Excellent	Moderate	Limited	4 hours
Levofloxacin	Good	Good	Strong	7 hours
Moxifloxacin	Moderate	Strong	Strong	12 hours

Precautions and Special Considerations

Avoid Ciprofloxacin in children unless benefits outweigh risks.
Do not use in patients with a history of tendon disorders related to fluoroquinolone use.
Hydration is important to prevent crystalluria.
Monitor ECG in patients with cardiac history.

Toxicity, Overdose and Antidote

In case of Ciprofloxacin overdose, symptoms may include dizziness, confusion, seizures, and renal impairment. There is no specific antidote. Management is supportive with emphasis on hydration, monitoring renal function, and possible haemodialysis (though only partially effective in elimination).

Recent 2025 Update and Guidelines

In 2025, the NICE guidelines emphasised cautious use of Ciprofloxacin due to increasing resistance and risk of serious side effects. It is now recommended as a second-line agent in uncomplicated infections and should be reserved for when culture sensitivity confirms its necessity.

Facts to Remember

Ciprofloxacin should not be taken with milk or yoghurt.
Never crush the tablets—swallow them whole.
Always complete the full course even if symptoms improve.
Keep a gap of 2 hours before or after antacids.

Did You Know?

Ciprofloxacin was one of the first fluoroquinolones approved and became globally famous in 2001 during the anthrax bioterrorism scare in the US, when it was stockpiled as the frontline antibiotic against Bacillus anthracis.

References

National Institute for Health and Care Excellence (NICE) Guidelines – 2025 Update
British National Formulary (BNF), 80th Edition
World Health Organization (WHO) Model List of Essential Medicines
Martindale: The Complete Drug Reference, 2024 Edition
The Lancet Infectious Diseases, January 2025 Issue – “Fluoroquinolone Resistance Trends in Europe”