Norfloxacin (Norflox) Tablet - Drug Profile

Drug Class

Fluoroquinolone antibiotic (2nd generation)

Mechanism of Action

Norfloxacin is bactericidal. It inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, preventing DNA unwinding and replication. This leads to bacterial cell death.

Goodman & Gilman's Pharmacological Basis of Therapeutics

Spectrum of Activity

Organism Type	Coverage
Gram-negative (E. coli, Proteus, Serratia, Salmonella, Shigella)	Good
Pseudomonas aeruginosa	Some activity
Gram-positive (Staphylococci)	Limited
Anaerobes	Poor
Intracellular organisms (Chlamydia, Mycoplasma)	Limited

Key limitation: Norfloxacin achieves effective concentrations only in the GI tract and urinary tract - it cannot be used for systemic infections because serum levels are relatively low.

Goodman & Gilman's, Katzung's Basic & Clinical Pharmacology

Indications

Urinary Tract Infections (UTI) - uncomplicated and recurrent (primary use)
Prostatitis - achieves good levels in prostatic secretions; 4-6 weeks course
Traveler's diarrhea - 1 to 3 day course; reduces loose stools by 1-3 days
SBP (Spontaneous Bacterial Peritonitis) prophylaxis - 400 mg/day in cirrhosis with ascites
Recurrent UTI prophylaxis - 200 mg daily (low dose)

Goodman & Gilman's, Sleisenger & Fordtran's GI and Liver Disease, Harrison's Principles (22nd ed)

Dosage

Indication	Dose	Duration
Uncomplicated UTI	400 mg twice daily	7-10 days
Complicated UTI / Prostatitis	400 mg twice daily	4-6 weeks
Traveler's diarrhea	400 mg twice daily OR 800 mg single dose	1-3 days
SBP prophylaxis	400 mg once daily	Long-term
Recurrent UTI prophylaxis	200 mg once daily	Long-term

Administration: Take on an empty stomach - at least 1 hour before or 2 hours after meals/milk (food and dairy reduce absorption).

Pharmacokinetics

Parameter	Details
Absorption	Well absorbed orally
Peak serum levels	1-3 hours after dose
Serum t½	3-5 hours
Distribution	High concentrations in urine, kidney, prostatic tissue, stool, bile
Elimination	~25% excreted unchanged in urine; also hepatic metabolism
Serum levels	Relatively low - limits systemic use

Goodman & Gilman's

Interactions: Absorption significantly reduced by antacids (Al/Mg), sucralfate, iron, zinc, calcium supplements. These should be taken 2 hours apart.

Adverse Effects (Black Box Warnings apply to all fluoroquinolones)

Common:

Nausea, vomiting, diarrhea
Headache, dizziness

Serious (Black Box Warnings):

Tendinitis and tendon rupture (especially Achilles tendon; risk higher in elderly >60 years, corticosteroid users, transplant recipients) - discontinue at first sign
Peripheral neuropathy (may be permanent)
CNS effects - hallucinations, anxiety, insomnia, confusion, seizures (possibly via GABA inhibition or Mg sequestration)

Other:

QT prolongation and torsades de pointes risk
Phototoxicity (exaggerated sunburn) - advise sunscreen, avoid UV
Hypersensitivity reactions
Hypoglycemia (especially with antidiabetic agents)
Aortic dissection/aneurysm (rare, associated with class)
Lippincott Illustrated Reviews Pharmacology, Tintinalli's Emergency Medicine

Contraindications

Known hypersensitivity to norfloxacin or any fluoroquinolone
History of fluoroquinolone-associated tendinopathy
Pre-pubertal children (risk of arthropathy/cartilage damage)
Pregnancy
Myasthenia gravis (may worsen neuromuscular blockade)

Drug Interactions

Antacids, sucralfate, iron, zinc, calcium - chelation reduces absorption (take 2 hrs apart)
Warfarin - fluoroquinolones inhibit CYP1A2, increasing anticoagulant effect; monitor INR
NSAIDs - increased seizure risk
QT-prolonging drugs - additive QT prolongation risk

Key Clinical Tips

Norfloxacin is not available in the United States (withdrawn); ciprofloxacin is the preferred alternative for systemic use
Resistance among E. coli is increasing in many regions - check local susceptibility patterns before empiric use
No longer recommended for gonorrhea (widespread resistance)
Dose adjustment required in renal impairment (CrCl ≤30 mL/min - extended dosing interval)
Not suitable for respiratory, CNS, or bone infections due to poor systemic penetration

Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics | Lippincott Illustrated Reviews Pharmacology | Harrison's Principles of Internal Medicine (22nd ed) | Katzung's Basic & Clinical Pharmacology | Sleisenger & Fordtran's GI and Liver Disease

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