norfloxacin (Discontinued)

Brand and Other Names:Noroxin, Norfloxacin Systemic
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Dosing & Uses


Dosage Forms & Strengths


  • 400mg


Caused by susceptible strains E.coli

400 mg PO q12hr for 28-42 days

UTI (Cystitis)

Uncomplicated, caused by E. coli, K. pneumoniae or P. mirabilis: 400 mg PO q12hr for 3 days

Uncomplicated, caused by other susceptible organisms: 400 mg PO q12hr for 7-10 days

Complicated: 400 mg PO q12hr for 10-21 days

Limitation-of-use: Reserve fluoroquinolones for patients who do not have other available treatment options for uncomplicated urinary tract infections


800 mg PO single dose

Uncomplicated urethral and cervical gonorrhea caused by Neisseria gonorrhoeae

Travelers Diarrhea

400 mg PO q12hr for 3 days

Renal Impairment

CrCl <30 mL/min: Give qDay

Other Indications & Uses

Treatment of infection caused by suscep strains of designated organisms based on culture and suscep if possible

Campylobacter jejuni, Citrobacter spp., Enterobacter spp., Enterococcus faecalis, E. coli, Klebsiella pneumoniae, Legionella pneumophila, Proteus mirabilis, Providencia spp, Pseudomonas aeruginosa, Salmonella spp, Serratia spp., Shigella spp, MSSA, Staphylococcus saprophyticus

<18 years: Safety and efficacy not established



Interaction Checker

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            Adverse Effects


            Nausea (4%)

            Dizziness (3%)

            Headache (3%)

            Stomach cramps (3%)

            Weakness (1%)


            Abdominal pain






            Back pain

            Bitter taste

            Cholestatic jaundice










            Exacerbation of myasthenia gravis



            GI bleeding


            Postmarketing Reports

            Hypersensitivity reactions: Anaphylactoid reactions, angioedema, dyspnea, vasculitis, urticaria, arthritis, arthralgia, and myalgia

            Skin: Toxic epidermal necrolysis, Stevens-Johnson syndrome and erythema multiforme, exfoliative dermatitis, photosensitivity/phototoxicity reactions, leukocytoclastic vasculitis, drug rash with eosinophilia and systemic symptoms (DRESS syndrome)

            Gastrointestinal: Pseudomembranous colitis, hepatitis, jaundice (including cholestatic jaundice and elevated liver function tests), pancreatitis (rare), stomatitis

            Hepatic: Hepatic failure, including fatal cases

            Cardiovascular: On rare occasions, prolonged QTc interval and ventricular arrhythmia including torsades de pointes

            Renal: Interstitial nephritis, renal failure

            Nervous system/psychiatric: Peripheral neuropathy, Guillain-Barré syndrome, ataxia, paresthesia, hypoesthesia, psychic disturbances (including psychotic reactions and confusion)

            Central nervous system effects: Hallucinations, anxiety, depression, insomnia, severe headaches, and confusion

            Musculoskeletal: Tendinitis, tendon rupture; exacerbation of myasthenia gravis, elevated creatine kinase (CK), muscle spasms

            Hematologic: Neutropenia, leukopenia, agranulocytosis, hemolytic anemia (sometimes associated with glucose-6-phosphate dehydrogenase deficiency), thrombocytopenia

            Special senses: Hearing loss, tinnitus, diplopia, dysgeusia



            Black Box Warnings

            Fluoroquinolones have been associated with disabling and potentially irreversible serious adverse reactions that have occurred together including: tendinitis and tendon rupture, peripheral neuropathy, and CNS effects

            Discontinue the drug immediately and avoid use of systemic fluoroquinolones in patients who experience any of these serious adverse reactions

            May exacerbate muscle weakness in patients with myasthenia gravis; avoid fluoroquinolones with known history of myasthenia gravis

            Serious adverse effects and limitations-of-use

            • Both oral and injectable fluoroquinolones are associated with disabling side effects involving tendons, muscles, joints, nerves and the central nervous system
            • These side effects can occur hours to weeks after exposure to fluoroquinolones and may potentially be permanent
            • Because the risk of these serious side effects generally outweighs the benefits for patients with acute bacterial sinusitis, acute exacerbation of chronic bronchitis, and uncomplicated UTIs, that fluoroquinolones should be reserved for use in patients with these conditions who have no alternative treatment options
            • For some serious bacterial infections, including anthrax, plague, and bacterial pneumonia among others, the benefits of fluoroquinolones outweigh the risks and it is appropriate for them to remain available as a therapeutic option


            Documented hypersensitivity

            All drugs or conditions that prolong QT interval


            In prolonged therapy, perform periodic evaluations of organ system functions (eg, renal, hepatic, hematopoietic); adjust dose in renal function impairment; superinfections may occur with prolonged or repeated antibiotic therapy

            Convulsions, increased intracranial pressure (including pseudotumor cerebri), and toxic psychosis reported with fluoroquinolones

            Peripheral neuropathy: Sensory or sensorimotor axonal polyneuropathy affecting small and/or large axons resulting in paresthesias, hypoesthesias, dysesthesias, and weakness reported; peripheral neuropathy may occur rapidly after initiating and may potentially become permanent

            Not drug of first choice in pediatrics due to increased incidence of adverse events compared to controls, including arthropathy; no data exist for dose for pediatric patients with renal impairment (ie, CrCl <50 mL/min)

            Acute onset of retinal detachment increased 4.5-fold with oral fluoroquinolones in a single case-controlled study - JAMA 2012;307(13):1414-1419; another study disputes these findings (relative risk, 1.29) - JAMA 2013;310(20):2184-2190

            Clostridium difficile-associated diarrhea (CDAD) has been reported; if CDAD suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued; appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated

            Prescribing antibiotics in absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to patient and increases risk of development of drug-resistant bacteria

            Commonly seen adverse reactions include tendinitis, tendon rupture, arthralgia, myalgia, peripheral neuropathy, and central nervous system effects (hallucinations, anxiety, depression, insomnia, severe headaches, and confusion); these reactions can occur within hours to weeks after starting therapy, including in patients of any age or without pre-existing risk factors; discontinue therapy immediately at first signs or symptoms of any serious adverse reaction; in addition, avoid use of fluoroquinolones, in patients who have experienced any serious adverse reactions associated with fluoroquinolones

            Risk of developing fluoroquinolone-associated tendinitis and tendon rupture is increased in patients over 60 years of age, in patients taking corticosteroid drugs, and in patients with kidney, heart or lung transplants; other factors that may independently increase risk of tendon rupture include strenuous physical activity, renal failure, and previous tendon disorders such as rheumatoid arthritis


            Pregnancy & Lactation

            Pregnancy Category: C; crosses placenta

            Lactation: Small amounts excreted in breast milk, discontinue drug or do not nurse

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.



            Mechanism of Action

            Inhibits bacterial DNA gyrase, which in turn inhibits DNA replication and transcription, DNA repair, recombination and transposicion, causing bacterial cell death


            Absorption: rapid, up to 40%

            Peak Plasma Time: 1-2 hr


            Protein Bound: 15%



            Enzymes inhibited: CYP1A2


            Half-Life: 3-4.5 hr

            Excretion: Feces 39%; urine 26-36%



            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.