Usage
Norfloxacin is a broad-spectrum antibiotic primarily used for treating bacterial infections, particularly those of the urinary tract (UTIs). It is also effective against certain sexually transmitted infections (STIs) such as gonorrhea, and some gastrointestinal infections like shigellosis and traveler’s diarrhea. Norfloxacin belongs to the fluoroquinolone class of antibiotics.
Norfloxacin’s mechanism of action involves inhibiting bacterial DNA gyrase and topoisomerase IV, enzymes essential for bacterial DNA replication and repair. This inhibition prevents bacterial growth and leads to bacterial cell death.
Alternate Names
While “norfloxacin” is the generic name, it is marketed under various brand names, including Noroxin.
How It Works
Pharmacodynamics: Norfloxacin exerts its bactericidal effect by targeting DNA gyrase and topoisomerase IV, enzymes crucial for bacterial DNA replication, transcription, and repair. Inhibition of these enzymes disrupts DNA supercoiling and strand breakage/reunion, leading to bacterial cell death.
Pharmacokinetics: Norfloxacin is administered orally and is absorbed from the gastrointestinal tract, reaching peak plasma concentrations within 1-2 hours. Approximately 30-40% of the drug is absorbed. It is primarily eliminated through renal excretion, with approximately 30% of the dose excreted unchanged in the urine. It has a biological half-life of 3-4 hours, which may increase in patients with renal impairment. Norfloxacin is metabolized to a limited extent in the liver.
Mode of Action: Norfloxacin inhibits bacterial DNA gyrase and topoisomerase IV. This inhibition leads to the accumulation of double-stranded DNA breaks, ultimately leading to bacterial cell death.
Elimination Pathways: Primarily renal excretion, with a smaller portion being metabolized by the liver.
Dosage
Standard Dosage
Adults:
- Urinary Tract Infections (UTIs): 400 mg twice daily for 7-10 days (uncomplicated), or up to 21 days (complicated).
- Gonorrhea: 800 mg as a single dose.
- Gastrointestinal Infections: 400 mg twice daily for 5 days.
Children:
Norfloxacin is generally not recommended for use in prepubertal children due to the risk of arthropathy (joint damage). However, limited data suggests that in certain cases, low doses may be used under strict medical supervision. Consult specific pediatric guidelines before prescribing.
Special Cases:
- Elderly Patients: Normal adult dose for those with adequate renal function. Reduce dose in patients with renal impairment (see below).
- Patients with Renal Impairment: Creatinine clearance less than 30 mL/min: 400 mg once daily.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are typically required.
- Patients with Comorbid Conditions: Monitor patients closely, especially those with seizures, myasthenia gravis, or cardiac arrhythmias.
Clinical Use Cases
Norfloxacin’s use in clinical settings outside of standard UTI, STI, and gastrointestinal infection treatment is limited. It is generally not recommended for conditions requiring intubation, surgical procedures, mechanical ventilation, or ICU use, as more effective alternative antibiotics are available. In emergency situations requiring immediate broad-spectrum coverage, other antibiotics are usually preferred.
Dosage Adjustments
Dosage adjustments are primarily based on renal function. Dose reduction is necessary in patients with moderate to severe renal impairment.
Side Effects
Common Side Effects
Nausea, diarrhea, headache, dizziness, abdominal pain, vomiting.
Rare but Serious Side Effects
Tendonitis, tendon rupture, peripheral neuropathy, seizures, QT prolongation, Clostridium difficile-associated diarrhea, serious skin reactions (e.g., Stevens-Johnson syndrome), hepatotoxicity, pseudotumor cerebri.
Long-Term Effects
Peripheral neuropathy, tendon damage.
Adverse Drug Reactions (ADR)
Anaphylaxis, angioedema, hepatotoxicity, Stevens-Johnson syndrome, toxic epidermal necrolysis.
Contraindications
Hypersensitivity to norfloxacin or other fluoroquinolones, history of tendonitis or tendon rupture associated with fluoroquinolone use, pregnancy, breastfeeding (unless deemed absolutely necessary by a physician), children and adolescents (except in specific circumstances under strict supervision).
Drug Interactions
Antacids (containing aluminum, magnesium, or calcium), sucralfate, iron or zinc supplements, multivitamins, didanosine, warfarin, theophylline, caffeine, certain antiarrhythmics, CYP1A2 substrates (e.g., clozapine, ropinirole, tizanidine).
Pregnancy and Breastfeeding
Norfloxacin is contraindicated in pregnancy due to potential risks to the developing fetus.
Norfloxacin is excreted in breast milk and can potentially cause adverse effects in nursing infants. Breastfeeding should be discontinued if norfloxacin therapy is required.
Drug Profile Summary
- Mechanism of Action: Inhibits bacterial DNA gyrase and topoisomerase IV.
- Side Effects: Nausea, diarrhea, headache, dizziness, tendon rupture, peripheral neuropathy.
- Contraindications: Hypersensitivity to fluoroquinolones, pregnancy, breastfeeding, children.
- Drug Interactions: Antacids, sucralfate, iron, warfarin, theophylline, caffeine.
- Pregnancy & Breastfeeding: Contraindicated.
- Dosage: Adults: 400 mg twice daily (UTIs), 800 mg single dose (gonorrhea).
- Monitoring Parameters: Renal function, signs of tendonitis or neuropathy, liver function tests.
Popular Combinations
Norfloxacin is not typically used in combination with other antibiotics.
Precautions
- Monitor patients for signs and symptoms of tendonitis, peripheral neuropathy, and CNS effects.
- Adequate hydration should be maintained during treatment.
- Patients should avoid excessive sun exposure.
- Caution should be exercised in patients with seizures, myasthenia gravis, or cardiac arrhythmias.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Norfloxacin for uncomplicated cystitis?
A: 400 mg twice daily for 3 days.
Q2: What is the recommended dosage for complicated UTIs?
A: 400 mg twice daily for 7-21 days.
Q3: Can Norfloxacin be used in pregnant women?
A: No, Norfloxacin is contraindicated in pregnancy.
Q4: What are the most common side effects of Norfloxacin?
A: Nausea, diarrhea, headache, and dizziness.
Q5: Should Norfloxacin be taken with food?
A: No, Norfloxacin should be taken on an empty stomach, at least 1 hour before or 2 hours after meals.
Q6: What should be done if a patient experiences tendon pain while taking Norfloxacin?
A: Discontinue Norfloxacin immediately and evaluate the patient for tendonitis or tendon rupture.
Q7: Can Norfloxacin be used to treat viral infections?
A: No, Norfloxacin is only effective against bacterial infections.
Q8: What are the serious adverse reactions associated with Norfloxacin?
A: Tendon rupture, peripheral neuropathy, seizures, QT interval prolongation, C. difficile infection, and hypersensitivity reactions.
Q9. How does renal impairment affect norfloxacin dosing?
A: For patients with a creatinine clearance of 30 mL/min/1.73 m² or less, the recommended dosage is 400 mg once daily.
