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. |
| 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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NOROXIN (NOROXIN).
| Breastfeeding | Norfloxacin is excreted in human breast milk. The milk-to-plasma ratio is approximately 0.9. Due to potential adverse effects on infant joint development and gastrointestinal flora, breastfeeding is not recommended during norfloxacin therapy. Consider alternative antibiotics or discontinue nursing. |
| 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. |
■ 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 fluoroquinolone","History of tendon disorders related to fluoroquinolone use","Concurrent use with tizanidine (potent CYP1A2 inhibition leading to severe hypotension/sedation)","Pregnancy (FDA Category C; risk to fetus based on animal studies)","Lactation (excreted in breast milk; potential for serious adverse reactions in nursing infants)","Children and adolescents (<18 years of age) due to risk of arthropathy"]
| 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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| 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. |