NOROXIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NOROXIN (NOROXIN).
Noroxin (norfloxacin) is a fluoroquinolone antibacterial agent that inhibits DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes required for bacterial DNA replication, transcription, repair, and recombination.
| Metabolism | Norfloxacin is metabolized in the liver via N-dealkylation and glucuronide conjugation. It undergoes enterohepatic recirculation. Approximately 30% of an oral dose is excreted unchanged in the urine, with additional metabolites excreted renally. |
| Excretion | Renal excretion accounts for approximately 30% of the dose as unchanged drug. Biliary/fecal elimination is a major route, with about 60-70% recovered in feces as unchanged drug and metabolites. |
| Half-life | Terminal elimination half-life is 6-7 hours in patients with normal renal function. Prolonged to 21-28 hours in severe renal impairment (CrCl <30 mL/min), requiring dose adjustment. |
| Protein binding | 30-40% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | Volume of distribution is 2-3 L/kg, indicating extensive tissue penetration, including prostate, kidney, and urine. |
| Bioavailability | Oral bioavailability is 30-50% due to first-pass metabolism. Ophthalmic: Systemic bioavailability is minimal (<1%) after topical administration. |
| Onset of Action | Oral: Onset of action occurs within 1-2 hours. Ophthalmic: Onset within 30 minutes following topical administration. |
| Duration of Action | Oral: Duration of action is approximately 12 hours, supporting twice-daily dosing. Ophthalmic: Duration is 4-6 hours after topical application. |
| Molecular Weight | 319.33 |
| Action Class | Quinolones/ Fluroquinolones |
| Brand Substitutes | Hiflox 400mg Tablet, Norotab 400mg Tablet, Norbat 400mg Tablet, Norcen 400mg Tablet, Uroquin 400mg Tablet |
400 mg orally twice daily for 3-14 days depending on indication.
| Dosage form | TABLET |
| Renal impairment | CrCl 30-50 mL/min: 400 mg once daily; CrCl <30 mL/min: contraindicated. |
| Liver impairment | No adjustment required for mild-moderate hepatic impairment; severe impairment (Child-Pugh class C): caution, use lower dose if necessary. |
| Pediatric use | Not recommended for children <18 years due to arthropathy risk. |
| Geriatric use | Use with caution; consider renal function and reduce dose if CrCl <50 mL/min. Monitor for tendonitis and QT prolongation. |
| 1st trimester | Avoid; animal studies show arthropathy and cartilaginous defects; human data limited but risk cannot be excluded. |
| 2nd trimester | Avoid; potential for fetal cartilage damage; use only if benefit outweighs risk. |
| 3rd trimester | Avoid; high risk of fetal cartilage damage and neonatal arthropathy. |
Clinical note
Comprehensive clinical and safety monograph for NOROXIN (NOROXIN).
| Placental transfer | Noroxin crosses the placenta; fetal concentrations are approximately 50% of maternal serum levels. |
| Breastfeeding | Noroxin is excreted in breast milk; potential for adverse effects in nursing infants, especially cartilage damage. Use caution; consider alternative therapies. |
| Lactation Rating |
■ FDA Black Box Warning
Fluoroquinolones, including norfloxacin, are associated with an increased risk of tendinitis and tendon rupture in all ages. This risk is further increased in older patients usually over 60 years of age, in patients taking corticosteroid drugs, and in patients with kidney, heart, or lung transplants.
| Serious Effects |
Hypersensitivity to norfloxacin or any fluoroquinoloneHistory of tendinitis or tendon rupture with fluoroquinolone useChildren and adolescents (<18 years)PregnancyBreastfeeding
| Precautions | Tendon damage (tendinitis and tendon rupture) – discontinue at first sign of pain or inflammation, Peripheral neuropathy – may occur rapidly; discontinue immediately, Central nervous system effects (e.g., dizziness, confusion, seizures) – use with caution in patients with CNS disorders, Exacerbation of myasthenia gravis – avoid use in patients with history of myasthenia gravis, Hypersensitivity reactions (including anaphylaxis) – discontinue and treat appropriately, QTc prolongation – use with caution in patients with risk factors for prolonged QTc, Photosensitivity/phototoxicity – avoid excessive sunlight or UV light, Clostridioides difficile-associated diarrhea – consider if diarrhea develops |
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| L4 (Possibly Hazardous) |
| Teratogenic Risk | NOROXIN (norfloxacin) is a fluoroquinolone antibiotic. It is contraindicated in pregnancy due to the risk of arthropathy in immature animals and potential fetal harm based on human data. First trimester: Avoid. Second and third trimesters: Avoid; associated with increased risk of aortic dissection and tendonitis. FDA Pregnancy Category C. |
| Fetal Monitoring | Monitor for maternal signs of hypersensitivity, tendonitis, aortic dissection (especially in pregnant or postpartum women). Fetal monitoring includes ultrasound for joint abnormalities if inadvertent exposure occurs. No specific fetal monitoring is routinely required. |
| Fertility Effects | Norfloxacin does not have known significant effects on fertility in humans based on available data. Animal studies showed no impairment of fertility at therapeutic doses. |
| Food/Dietary |
| Avoid dairy products (milk, yogurt) and calcium-fortified juices within 2 hours of dosing, as they can reduce absorption. Caffeine intake should be limited, as Noroxin may increase caffeine effects (nervousness, insomnia). |
| Clinical Pearls | Noroxin (norfloxacin) is a fluoroquinolone antibiotic with limited systemic absorption; it is primarily used for uncomplicated urinary tract infections and prostatitis. Avoid coadministration with antacids, sucralfate, and iron or zinc supplements due to chelation. Use with caution in patients with known QT prolongation or those taking class IA/III antiarrhythmics. Noroxin is contraindicated in patients with a history of tendon disorders related to fluoroquinolones. Renal dose adjustment is required for CrCl <30 mL/min. |
| Patient Advice | Take Noroxin on an empty stomach, at least 1 hour before or 2 hours after meals. · Avoid antacids, iron supplements, zinc supplements, or sucralfate within 2 hours of taking Noroxin. · Drink plenty of fluids to prevent crystalluria. · Stop taking the medication and contact your doctor immediately if you experience tendon pain, swelling, or rupture, especially in the Achilles tendon. · Report any signs of allergic reaction, such as rash, hives, or difficulty breathing. · Noroxin may cause dizziness or lightheadedness; avoid driving or operating machinery until you know how it affects you. · Complete the full course of therapy even if you feel better. · Avoid excessive sun exposure and use sunscreen, as Noroxin can increase photosensitivity. |