NORFLOXACIN 400MG TABLET

Indications

• Urinary tract infections
• Bacterial infections
• Prostatitis

Dosage

Children: Refer to BNF for Children for specific dosing information.

Adults: The usual oral dosage for adults is 400 mg twice daily, taken at least 1 hour before or 2 hours after meals.

Mechanism of action

Norfloxacin exerts its bactericidal effect by inhibiting the enzymes topoisomerase II (DNA gyrase) and topoisomerase IV, which are crucial for bacterial DNA replication, transcription, repair, and recombination. The fluorine atom at the 6 position enhances its potency against Gram-negative organisms, while the piperazine moiety at the 7 position provides anti-pseudomonal activity. Additionally, norfloxacin prolongs the QT interval by blocking voltage-gated potassium channels, particularly the rapid component of the delayed rectifier potassium current I(Kr).

Pharmacodynamics

As a fluoroquinolone antibiotic, norfloxacin demonstrates a bactericidal effect through its high affinity binding to bacterial DNA gyrase, which facilitates the untwisting required for DNA replication. The drug is noted for its significantly greater affinity for bacterial enzymes compared to mammalian enzymes, ensuring selective action against bacteria.

Pharmacokinetics

Norfloxacin is well-absorbed following oral administration, with peak plasma concentrations occurring within 1 to 2 hours. It is widely distributed in body tissues and fluids, including urine, where it achieves therapeutic concentrations. The drug undergoes hepatic metabolism and is primarily excreted via the kidneys. The half-life of norfloxacin ranges from 3 to 4 hours, necessitating multiple doses for effective therapy.

Contra-indications

• Hypersensitivity to norfloxacin or any of its components
• History of tendon disorders related to fluoroquinolone use
• Patients with a history of myasthenia gravis

Adverse effects

• Nausea
• Diarrhea
• Headache
• Dizziness
• Rash
• Tendon rupture
• QT interval prolongation

Interactions

• Antacids containing magnesium, aluminum, or calcium may reduce the absorption of norfloxacin
• Concurrent use with other drugs that prolong the QT interval can increase the risk of cardiac arrhythmias
• Ciprofloxacin and other fluoroquinolones may increase the effects of warfarin

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of tendon injury, especially in older patients and those on concurrent corticosteroids
• Assess risk factors for QT prolongation before prescribing

Pregnancy

Norfloxacin should only be used in pregnancy if the benefit outweighs the risk, as it may affect fetal development.

Breast-feeding

Norfloxacin is excreted in breast milk; caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from direct sunlight and moisture.

Formulations

• Oral tablet: 400 mg

Mechanism of action

The bactericidal action of Norfloxacin results from inhibition of the enzymes topoisomerase II (DNA gyrase) and topoisomerase IV, which are required for bacterial DNA replication, transcription, repair, and recombination. Norfloxacin is a broad-spectrum antibiotic agent that is shown to be effective against various Gram-positive and Gram-negative bacterial species. The fluorine atom at the 6 position increases potency against gram-negative organisms, and the piperazine moiety at the 7 position is responsible for anti-pseudomonal activity Norfloxacin usually is bactericidal in action. Like other fluoroquinolone anti-infectives, norfloxacin inhibits DNA synthesis in susceptible organisms via inhibition of type II DNA topoisomerases (DNA gyrase, topoisomerase IV). Fluoroquinolones prolong the QT interval by blocking voltage-gated potassium channels, especially the rapid component of the delayed rectifier potassium current I(Kr), expressed by HERG (the human ether-a-go-go-related gene). According to the available case reports and clinical studies, moxifloxacin carries the greatest risk of QT prolongation from all available quinolones in clinical practice and it should be used with caution in patients with predisposing factors for Torsades de pointes (TdP).

Pharmacodynamics

Norfloxacin is a quinolone/fluoroquinolone antibiotic. Norfloxacin is bactericidal and its mode of action depends on blocking of bacterial DNA replication by binding itself to an enzyme called DNA gyrase, which allows the untwisting required to replicate one DNA double helix into two. Notably the drug has 100 times higher affinity for bacterial DNA gyrase than for mammalian.