Fluoroquinolones · Anti-infectives
Ciprofloxacin
Cipro®(brand names vary by market)
A gram-negative workhorse whose bill of warnings keeps growing.
Also: oral liquid, infusion
Mechanism
Inhibits bacterial DNA gyrase and topoisomerase IV: concentration-dependent bactericidal killing, strong gram-negative activity.
Indications
- Complicated urinary tract infection and pyelonephritis
- Selected gram-negative infections
- Some GI infections
Formulations
Dosing concepts
Chelation
Divalent cations (calcium, magnesium, iron, zinc, antacids, dairy) bind it in the gut; separate administration by hours or lose the drug.
Renal function
Renally cleared; dose adjusts with impairment.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- ~70%
- Half-life
- ~4 h
- Elimination
- renal
Adverse effects
- GI upsetcommon
- Tendinopathy and tendon ruptureseriousRisk rises with age, corticosteroids, renal disease.
- QT prolongationserious
- CNS effects: confusion, seizures (rare)serious
- C. difficile colitisserious
- Aortic aneurysm/dissection signal; hypoglycemiaserious
Contraindications & precautions
Contraindications
- Concurrent tizanidine
- History of quinolone tendinopathy
Precautions
- Older adults on corticosteroids
- Known QT prolongation or interacting QT drugs
- Myasthenia gravis
- Reserve where first-line agents suffice (stewardship)
Interactions
- Ciprofloxacin (and all fluoroquinolones, tetracyclines) + Calcium, magnesium, aluminum, iron, zinc. Antacids, dairy, supplementscautionSub-therapeutic antibiotic levels: treatment failure that looks like resistance.
- Ciprofloxacin + WarfarincautionINR rise during the course.
- Ciprofloxacin + TheophyllineavoidTheophylline toxicity: nausea, tachyarrhythmia, seizures.
Monitoring
Tendon pain (report immediately)
Rupture is preventable if caught at pain stage
QT-relevant combinations
Additive prolongation
Clinical response at 48-72 h
Reassessment / de-escalation point
Counselling points
- Do not take with dairy, antacids, calcium, iron, or zinc. Separate by at least two hours before or six after.
- Stop and call if a tendon (often the Achilles) becomes painful or swollen.
- Sun sensitivity: cover up and use sunscreen.
Clinical pearls
- The chelation interaction is the most commonly quizzed and most commonly committed fluoroquinolone error.
References & review
- Ciprofloxacin product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-15 · jurisdiction: global · drug information changes; verify against current references before practice use.