[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Fluoroquinolones](https://durgical.com/en/pharmacology/classes/fluoroquinolones/) › Ciprofloxacin [Pharmacology](https://durgical.com/en/pharmacology/) · [Fluoroquinolones](https://durgical.com/en/pharmacology/classes/fluoroquinolones/) # Ciprofloxacin The fluoroquinolone most active against gram-negatives such as Pseudomonas. Used for kidney, prostate and gut infections, with tendon and nerve warnings. Updated 2026-11-01 - Class: [Fluoroquinolones](https://durgical.com/en/pharmacology/classes/fluoroquinolones/) - Enzyme: Bacterial DNA gyrase and topoisomerase IV - ATC code: J01MA02 - WHO Model List of Essential Medicines ✂**Bacterial DNA gyrase and topoisomerase IV**Ciprofloxacin ⓘ The figure shows ciprofloxacin wedged into DNA cut by Staphylococcus aureus DNA gyrase. **Target in 3D:** Bacterial DNA gyrase and topoisomerase IV. PDB structure 2XCT (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/2XCT) · Drag to rotate · pinch to zoom ## Mechanism of action Ciprofloxacin binds DNA gyrase and topoisomerase IV at the moment they have cut both DNA strands. The enzyme cannot rejoin the DNA, so the cut becomes a lasting double-strand break and the bacterium dies. Its strongest activity is against gram-negative bacilli, including Pseudomonas aeruginosa; it is weaker against pneumococcus. - Enters the bacterium through porins - Binds gyrase or topoisomerase IV on cut DNA - The DNA cannot be rejoined - Double-strand breaks kill the cell ## Pharmacokinetics **Absorption** Well absorbed by mouth; antacids with magnesium or aluminium can cut absorption by up to 90%. Also given IV. **Distribution** Wide; plasma protein binding 20–40%. **Elimination** Kidney and other routes; the dose is adjusted in kidney failure. **Half-life** About 4 hours with normal kidney function. ## Indications - Acute pyelonephritis (WHO first choice in mild to moderate disease) [Acute pyelonephritis →](https://durgical.com/en/conditions/acute-pyelonephritis/) - Bacterial prostatitis [Prostatitis →](https://durgical.com/en/conditions/prostatitis/) - Complicated urinary tract infection when other options are unsuitable [Urinary tract infection (acute cystitis) →](https://durgical.com/en/conditions/urinary-tract-infection/) - Typhoid and paratyphoid fever and infectious diarrhoea (WHO list) - Inhalational anthrax after exposure and plague; ear drops for external otitis ## Adverse effects ### Common - Nausea, diarrhoea and abdominal pain - Headache, dizziness and insomnia - Rash and photosensitivity ### Serious (rare, important) - Tendinitis and tendon rupture, peripheral neuropathy and CNS effects (boxed warning), often together and sometimes permanent - Worse muscle weakness in myasthenia gravis - QT prolongation, low or high blood sugar, aortic aneurysm and dissection - Hepatotoxicity, severe allergic reactions and C. difficile colitis ## Contraindications - Allergy to ciprofloxacin or any quinolone - Use together with tizanidine ## Key interactions **Tizanidine** Contraindicated: ciprofloxacin blocks its breakdown by CYP1A2, causing low blood pressure and sedation. **Theophylline and caffeine** Levels rise (CYP1A2 inhibition): risk of seizures and arrhythmia with theophylline. **Antacids, calcium, iron, zinc, dairy products alone** Bind ciprofloxacin in the gut; the doses are spaced. **Warfarin and antidiabetic drugs** Stronger anticoagulant effect; risk of hypoglycaemia. ## What is monitored - Tendon pain, numbness or tingling, mood or sleep changes - Blood glucose in diabetes - ECG in patients at risk of QT prolongation; kidney function ## Administration and safety - Oral doses are separated from antacids, minerals and dairy-only drinks - Plenty of fluid helps avoid crystals in the urine - Infuse the IV form slowly into a large vein ## Nursing care - Ask about previous tendon problems, myasthenia gravis and corticosteroid use - Teach to stop and report tendon pain, numbness, confusion or palpitations - Advise sun protection - Check glucose more often in diabetes ## Pregnancy and breastfeeding Animal studies have not shown malformations and human data have not shown a clear increase in birth defects, but safer options are usually chosen. ## Memory aid «Cipro cuts and keeps the scissors stuck»: the gyrase cuts the DNA, ciprofloxacin jams it, and the broken strands kill the bacterium. ## Test yourself Think of the answer, then tap the question to see it. ## Which bacteria are the main strength of ciprofloxacin? Gram-negative bacilli, including Pseudomonas aeruginosa. ## Why is tizanidine contraindicated with ciprofloxacin? Ciprofloxacin inhibits CYP1A2, the enzyme that clears tizanidine, causing severe hypotension and sedation. ## Which adverse effects form the boxed warning? Tendinitis and tendon rupture, peripheral neuropathy, central nervous system effects and worsening of myasthenia gravis. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/ciprofloxacin/) ## Related drugs - [Levofloxacin](https://durgical.com/en/pharmacology/levofloxacin/) - [Moxifloxacin](https://durgical.com/en/pharmacology/moxifloxacin/) - [Ofloxacin](https://durgical.com/en/pharmacology/ofloxacin/) ## Related conditions - [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/) - [Prostatitis](https://durgical.com/en/conditions/prostatitis/) - [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/) [← Back to the class: Fluoroquinolones](https://durgical.com/en/pharmacology/classes/fluoroquinolones/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - CIPROFLOXACIN tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=fa32aafd-e3f5-4be6-9413-c7663c1c2cec) (DailyMed (U.S. National Library of Medicine), 2026); [Ciprofloxacin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a688016.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/?query=ciprofloxacin) (World Health Organization, 2025); [The twinned 3.35A structure of S. aureus Gyrase complex with Ciprofloxacin and DNA](https://www.rcsb.org/structure/2XCT) (RCSB Protein Data Bank, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/ciprofloxacin/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/ciprofloxacin/