Classifications: quinolone antibiotic;
Therapeutic: antibiotic
; quinolone
Prototype: Ciprofloxacin
Pregnancy Category: C


400 mg tablets


Potent broad-spectrum antibiotic activity. Alters structure of bacterial DNA gyrase, thus promoting double-stranded DNA breakage, thus interfering with synthesis of bacterial protein and blocking bacterial survival.

Therapeutic Effect

Active against many bacterial pathogens of the urinary tract.


Complicated and uncomplicated urinary tract infection (UTI) caused by susceptible organisms. Conjunctivitis.

Unlabeled Uses

Gonorrhea, gastroenteritis, and prevention of travelers' diarrhea.


Use in individual with known factors that predispose to seizures; history of hypersensitivity to norfloxacin and other quinolone antibiotics; history of QT prolongation; tendon pain; pregnancy (category C), lactation; children <18 y.

Cautious Use

Impaired kidney function, adolescents if skeletal growth is complete; G6PD deficiency; GI disease; myasthenia gravis.

Route & Dosage

Urinary Tract Infection
Adult: PO 400 mg b.i.d.

Gonorrhea or Gonococcal Urethritis
Adult: PO 800 mg once/d

Bacterial Gastroenteritis
Adult: PO 400 mg q8–12h


  • Give 1 h before or 2 h after meals with a full glass of water.
  • Administer concomitant antacid at least 2 h after norfloxacin to prevent interference with absorption. Aluminum or magnesium ions in the antacid may bind to and form insoluble complexes with the quinolone in GI tract.
  • Store at 40° C (104° F) or less in tightly closed container. Do not freeze.

Adverse Effects (≥1%)

Musculoskeletal: Joint swelling, cartilage erosion in weight-bearing joints, tendonitis. In immunosuppressed adult: acute ankle and hip pain followed by acute pain, tenderness, and swelling of tendon sheath of middle finger of both hands after 4 wk of therapy. CNS: Headache, dizziness, lightheadedness, fatigue, drowsiness, somnolence, depression, insomnia, seizures, peripheral neuropathy. GI: Nausea, abdominal pain, diarrhea, vomiting, anorexia, dyspepsia, dysphagia, dry mouth, bitter taste, heartburn, flatulence, pruritus ani, increased serum AST, ALT, alkaline phosphatase. Hematologic: Leukopenia, neutropenia. Urogenital: With high doses: Crystalluria (not associated with renal toxicity), vulvar irritation.

Diagnostic Test Interference

May cause false positive on opiate screening tests.


Drug: antacids, iron, sucralfate, zinc decrease absorption; nitrofurantoin may antagonize antibacterial effects; may increase hypoprothrombinemic effects of warfarin; may cause slight increase in theophylline levels; concurrent administration with class ia and class iii antiarrhythmics may result in development of QT prolongation as well as torsades de points.


Absorption: 30–40% from GI tract. Peak: 1–2 h. Distribution: Renal parenchyma, gallbladder, liver, prostate; crosses placenta; distributed into breast milk. Metabolism: In liver. Elimination: In urine and feces. Half-Life: 3–4 h.

Nursing Implications

Assessment & Drug Effects

  • Collect urine specimens for testing before initiating antibiotic.
  • Monitor patient for tendon pain. Norfloxacin should be discontinued and physician informed.
  • Lab tests: Periodic WBC with differential, liver enzymes, and alkaline phosphatase, especially with prolonged use.
  • Report to the physician if patient is adequately hydrated, yet I&O ratio and pattern changes are noted, or if condition does not improve within a few days. Dosage may need to be modified.

Patient & Family Education

  • Take drug at same times each day.
  • Take drug exactly as prescribed. Erratic dosing can encourage emergence of resistant bacteria; underdosing or premature discontinuation of treatment can cause return of UTI symptoms.
  • Keep fluid intake high (at least 2500–3000 mL/d if tolerated) to provide adequate urine output and hydration, important in the prevention of crystalluria (rare side effect).

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2022 Last Updated On: 11/20/2022 (0)
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