Norfloxacin

Second-generation fluoroquinolone

ATC code: J01MA06(J01MA06)

Brand names: Noroxin, Utinor, Norflox

Updated 24 Sep 2026 · Methodology

Indications

Spontaneous bacterial peritonitis prophylaxis

First line

Norfloxacin 400 mg daily is the first-line agent for secondary SBP prophylaxis in cirrhotic patients with ascites after a prior SBP episode. 2021 and 2018 endorse this recommendation. Primary prophylaxis is justified with low ascitic protein (below 15 g/L) and concurrent renal or hepatic dysfunction. The 2009 Cochrane review showed a 50–60% reduction in SBP risk and all-cause mortality. In light of fluoroquinolone risks per 2018 and 2019, prophylaxis duration and patient status are reassessed every 3–6 months.

Alternatives include ciprofloxacin or rifaximin. The drug is not used in patients with fluoroquinolone intolerance or a history of aortic aneurysm.

Sources

ICD-10: K65.0 · ICD-11: DC50.0

Travelers' diarrhea

Individual decision

For travelers' diarrhea, norfloxacin 400 mg twice daily for 1–3 days was formerly part of standard regimens. With 2018 and 2019 restrictions, fluoroquinolones are not used for self-limited gastrointestinal infections. First-line agents for severe diarrhea are azithromycin 1000 mg as a single dose or rifaximin in the absence of fever and bloody stools. Norfloxacin is considered individually when alternatives are unavailable in patients without risk factors for adverse effects.

Sources

EMA: EMA Disabling and potentially permanent side effects lead to suspension or restrictions of quinolone and fluoroquinolone antibiotics (2019)

ICD-10: A09 · ICD-11: 1A40

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Uncomplicated acute cystitis in women

Not recommended

For acute uncomplicated cystitis in non-pregnant women, norfloxacin is not recommended as first line. 2018 and 2019 restricted fluoroquinolones because of severe and potentially irreversible adverse effects (tendinitis, tendon rupture, peripheral neuropathy, aortic aneurysm). When alternatives are available (nitrofurantoin, fosfomycin, trimethoprim-sulfamethoxazole), fluoroquinolones are not used for simple cystitis. Norfloxacin is reserved for confirmed resistance to first-line agents in patients without risk factors for fluoroquinolone adverse effects.

Not prescribed in patients over 60, after organ transplantation, on systemic glucocorticoids, with connective tissue diseases, or with QT prolongation.

Sources

ICD-10: N30.0 · ICD-11: GC00.0

Acute viral bronchitis

Not recommended

For acute uncomplicated bronchitis in immunocompetent adults, norfloxacin is not prescribed. An antibiotic does not shorten cough duration in a viral infection, while a fluoroquinolone with severe and irreversible adverse effects (tendinitis, aortic aneurysm) is used only under strict indications. 2018 explicitly restricts fluoroquinolone use in simple infections where alternatives exist or antibiotics are not indicated.

Sources

EMA: EMA Disabling and potentially permanent side effects lead to suspension or restrictions of quinolone and fluoroquinolone antibiotics (2019)

ICD-10: J20 · ICD-11: CA42

How to read tiers A–F

AStrong evidence – first or second line in international guidelines
BRecommended in selected cases
CStudy data contradict each other
DBenefit not proven, no documented harm
FDocumented harm, or risk without benefit

Mechanism of action

Inhibits bacterial DNA gyrase and topoisomerase IV. Used mainly for uncomplicated UTI. and restricted fluoroquinolones since 2018–2019 due to tendinopathy, aortopathy, and neurological adverse events.

Safety

Boxed warning

FDA boxed warning for the entire fluoroquinolone class: risk of tendinitis and tendon rupture, peripheral neuropathy and CNS effects, and myasthenia gravis exacerbation. The cumulative risk of these adverse effects outweighs benefit in sinusitis, bronchitis, and uncomplicated UTI when alternatives are available. Since 2018, FDA has restricted fluoroquinolone use in these indications.

Contraindications

Hypersensitivity to fluoroquinolones in history
Tendinitis or tendon rupture on fluoroquinolones in history
Age under 18 (cartilage and arthropathy risk)
Pregnancy and breastfeeding
QT prolongation, uncorrected hypokalemia/hypomagnesemia
History of aortic aneurysm or dissection
Connective tissue disorders (Marfan, Ehlers-Danlos syndromes)
Epilepsy or seizure history

Serious adverse effects

Achilles and rotator cuff tendon rupture, especially in the elderly and on systemic glucocorticoids
Peripheral neuropathy, often irreversible
Aortic aneurysm and dissection
Psychiatric disturbances: depression, psychosis, suicidal ideation
Hypoglycemia, hyperglycemia (especially in elderly on antidiabetic agents)
Severe ventricular arrhythmias including torsades de pointes
C. difficile-associated colitis

Common adverse effects

Nausea, diarrhea, abdominal discomfort
Headache, dizziness
Insomnia, increased anxiety
Rash, photosensitivity

Uncommon adverse effects

Tendinitis, especially of the Achilles tendon
QT interval prolongation on ECG
Crystalluria with inadequate urine output

Pregnancy: can you take Norfloxacin?

AEMPS summary of product characteristics (section 4.6): the safety of norfloxacin in pregnant women has not been established, so the benefits of treatment are weighed against the potential risks. Norfloxacin is found in the umbilical cord and amniotic fluid.

Breastfeeding: can you take Norfloxacin?

Norfloxacin passes into breast milk. Breastfeeding is interrupted during the course or an alternative compatible with lactation is selected.

Calculate RID Full profile on NIH LactMed ↗

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Practical notes

Timing and administration

Take 1 hour before or 2 hours after a meal, with a full glass of water. Do not co-administer with dairy, antacids, calcium, iron, magnesium, zinc, or sucralfate – divalent cations form non-absorbable complexes and reduce bioavailability 2-3-fold. The interval is at least 2 hours before and 6 hours after norfloxacin.

Dose titration

Standard doses: UTI – 400 mg twice daily for 3–7 days; SBP prophylaxis – 400 mg once daily long-term; travelers' diarrhea – 400 mg twice daily for 1–3 days. At eGFR 10–30 mL/min/1.73 m², the dosing interval is extended to 24 hours. In the elderly, the dose is unchanged, but renal function and tendon status are monitored.

Monitoring

Before starting prolonged therapy (SBP prophylaxis), check ECG, serum potassium and magnesium, creatinine, and eGFR. On long-term therapy, the need for continuation and tolerability are reassessed every 3–6 months. Tendon pain, swelling, or tendinopathy is an immediate indication to stop the drug and limit physical activity. In patients on antidiabetics, glycemia is monitored in the first days of therapy.

Special situations

Concomitant NSAIDs raise seizure risk; warfarin – INR prolongation; theophylline – seizures and tachycardia; QT-prolonging agents – torsades de pointes. In diabetic patients on antidiabetics, fluoroquinolones cause both hypo- and hyperglycemia. Long flights and physical exertion during therapy raise the risk of Achilles tendon rupture and are discussed with the patient.

Common myths

Myth: "fluoroquinolone is a universal antibiotic, fits any infection". Fact: since 2018 and have restricted fluoroquinolone use because of severe irreversible adverse effects. They are not prescribed for simple UTI, sinusitis, or bronchitis when alternatives are available.

Myth: "tendinitis is a rare complication, nothing to watch for". Fact: tendinitis occurs in 0.1–0.4% of patients, up to 6% in the elderly on glucocorticoids. Tendon pain is an indication to stop immediately.

Myth: "can be combined with calcium and vitamins". Fact: co-administration with calcium, iron, magnesium, zinc, or antacids cuts norfloxacin bioavailability 2-3-fold. The interval is at least 2 hours.

Drug–drug interactions

1 pair found. Sorted from critical to minor.

MinorEthinylestradiolEstrogens. Natural and semisynthetic estrogens, plain

Mechanism

Norfloxacin does not induce CYP3A4 and does not affect ethinylestradiol metabolism. The historical theory of reduced COC efficacy is rejected by meta-analyses.

Symptoms

The combination usually causes no specific symptoms. Each drug's individual side effects remain.

Management

Additional contraception during short norfloxacin courses (3–7 days) is not needed.

Sources

ACOG: Use of Hormonal Contraception in Women With Coexisting Medical Conditions, Practice Bulletin No. 206 (2018)

Pair details →Ethinylestradiol →

Label mentions11 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

Majorcorticosteroidesclass named in the label
«Tendinitis y rotura de tendones: Ante el primer signo de tendinitis (p.ej. tumefacción dolorosa, inflamación), se debe interrumpir el tratamiento con norfloxacino y se debe considerar un tratamiento…»
AEMPS, section 4.4 · Open on CIMA
Moderateanticoagulantesclass named in the label
«Las quinolonas, incluido norfloxacino, pueden intensificar la acción de los anticoagulantes orales como warfarina o sus derivados. En la administración conjunta de estos medicamentos, debe…»
AEMPS, section 4.5 · Open on CIMA
ModerateCiclosporin
«La administración conjunta de quinolonas (norfloxacino) y teofilina o ciclosporina aumenta el valor de estas últimas en plasma, pudiéndose producir efectos secundarios ligados a estos fármacos. Por…»
AEMPS, section 4.5 · Open on CIMA
ModerateTheophylline
«La administración conjunta de quinolonas (norfloxacino) y teofilina o ciclosporina aumenta el valor de estas últimas en plasma, pudiéndose producir efectos secundarios ligados a estos fármacos. Por…»
AEMPS, section 4.5 · Open on CIMA
ModerateWarfarin
«Las quinolonas, incluido norfloxacino, pueden intensificar la acción de los anticoagulantes orales como warfarina o sus derivados. En la administración conjunta de estos medicamentos, debe…»
AEMPS, section 4.5 · Open on CIMA
antiácidosclass named in the label
«Los antiácidos, el sucralfato y los preparados de zinc y hierro reducen la absorción de norfloxacino. Por consiguiente, este medicamento debe tomarse de 3 a 4 horas antes o 2 horas después de la…»
AEMPS, section 4.5 · Open on CIMA

From other drugs’ labels

Dofetilide
«Drug-Drug Interactions: Cimetidine: (see WARNINGS, CONTRAINDICATIONS ) Concomitant use of cimetidine is contraindicated. Cimetidine at 400 mg BID (the usual prescription dose) co-administered with…»
FDA, section 7 · Open on DailyMed
Mycophenolate mofetil
«Norfloxacino y metronidazol: No se ha observado interacción significativa en la administración concomitante de micofenolato de mofetilo con norfloxacino o con metronidazol en voluntarios sanos. Sin…»
AEMPS, section 4.5 · Open on CIMA
Theophylline
«Drug Interactions:: co-trimoxazole (trimethoprim and sulfamethoxazole) norfloxacin»
FDA, section 7 · Open on DailyMed
Warfarin
«Inhibidores enzimáticos: pueden potenciar el efecto anticoagulante, con riesgo de hemorragias, debido a una inhibición de su metabolismo hepático, cuando se administra conjuntamente con: alopurinol…»
AEMPS, section 4.5 · Open on CIMA
Warfarin
«CYP450 Interactions: CYP1A2 acyclovir, allopurinol, caffeine, cimetidine, ciprofloxacin, disulfiram, enoxacin, famotidine, fluvoxamine, methoxsalen, mexiletine, norfloxacin, oral contraceptives…»
FDA, section 7 · Open on DailyMed

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Frequently asked

What is Norfloxacin used for?

Norfloxacin is evaluated for the following indications with varying evidence strength: Spontaneous bacterial peritonitis prophylaxis (evidence tier B), Travelers' diarrhea (evidence tier C), Uncomplicated acute cystitis in women (evidence tier D). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Norfloxacin?

Common side effects of Norfloxacin (≥ 1 in 100): Nausea, diarrhea, abdominal discomfort, Headache, dizziness, Insomnia, increased anxiety, Rash, photosensitivity. See the Safety section for uncommon and serious reactions.

Is Norfloxacin safe during pregnancy?

Is Norfloxacin compatible with breastfeeding?

Norfloxacin passes into breast milk. Breastfeeding is interrupted during the course or an alternative compatible with lactation is selected.

Who should not take Norfloxacin?

Norfloxacin is contraindicated in: Hypersensitivity to fluoroquinolones in history; Tendinitis or tendon rupture on fluoroquinolones in history; Age under 18 (cartilage and arthropathy risk); Pregnancy and breastfeeding; QT prolongation, uncorrected hypokalemia/hypomagnesemia. Full list in the Safety section.

Does Norfloxacin carry an FDA boxed warning?

fluoroquinolone is a universal antibiotic, fits any infection

since 2018 FDA and EMA have restricted fluoroquinolone use because of severe irreversible adverse effects. They are not prescribed for simple UTI, sinusitis, or bronchitis when alternatives are available.

tendinitis is a rare complication, nothing to watch for

tendinitis occurs in 0.1–0.4% of patients, up to 6% in the elderly on glucocorticoids. Tendon pain is an indication to stop immediately.

can be combined with calcium and vitamins

co-administration with calcium, iron, magnesium, zinc, or antacids cuts norfloxacin bioavailability 2-3-fold. The interval is at least 2 hours.

Official sources

Direct links to regulator labels. Open in a new tab.

AEMPS / CIMALabel dated 06/12/2025
GRLS

Other drugs in this group

Trimethoprim, Amoxicillin + Clavulanic Acid, Amoxicillin, Azithromycin, Cefalexin, Ciprofloxacin, Doxycycline, Levofloxacin