Classifications: urinary tract antiinfective; antibiotic, quinolone;
Therapeutic: urinary tract antiinfective
; quinolone antibiotic
Prototype: Ciprofloxacin
Pregnancy Category: B second and third trimester


250 mg, 500 mg, 1 g tablets


Synthetic quinolone. Intracellular action inhibits microbial DNA replication and RNA synthesis.

Therapeutic Effect

Marked bactericidal activity against most gram-negative urinary tract pathogens with the exception of strains of Pseudomonas.


Urinary tract infections caused by susceptible gram-negative organisms including most Proteus strains, Klebsiella, Enterobacter, and Escherichia coli.

Unlabeled Uses

GI tract infections caused by susceptible strains of Shigella sonnei; prophylaxis of bacteriuria and in bladder irrigation for low-grade cystitis.


History of convulsive disorders; first trimester of pregnancy; infants <3 mo.

Cautious Use

Prepubertal child; second and third trimesters of pregnancy (category B); kidney or liver disease; epilepsy; cerebral arteriosclerosis; respiratory insufficiency; patients and breast-feeding infants with G6PD deficiency.

Route & Dosage

Urinary Tract Infections
Adult: PO Acute therapy: 1 g q.i.d.; Chronic therapy: 500 mg q.i.d.
Child (>3 mo): PO Acute therapy: 55 mg/kg/d in 4 divided doses; Chronic therapy: 33 mg/kg/d in 4 divided doses


  • Give with food or milk if drug causes GI distress. Otherwise, give on an empty stomach 1 h before or 2 h after meals.
  • Store at 15°–30° C (59°–86° F) in tight container and avoid freezing.

Adverse Effects (≥1%)

Body as a Whole: Angioedema, fever, chills, arthralgia, hypersensitivity pneumonitis, anaphylaxis (rare). CNS: Drowsiness, headache, malaise, dizziness, vertigo, syncope, weakness, myalgia, peripheral neuritis, confusion, excitement, mental depression, seizures, insomnia. GI: Abdominal pain, nausea, vomiting, diarrhea, cholestasis, transient increase in AST. Hematologic: Eosinophilia, hemolytic anemia (especially in G6PD deficiency). Skin: Photosensitivity, pruritus, urticaria, rash. Other: Cartilage erosion.

Diagnostic Test Interference

False-positive urine tests for glucose with cupric sulfate reagent (e.g., Benedict's or Clinitest) but not with glucose oxidase methods (e.g., Clinistix, TesTape). May cause elevation of urinary 17-ketosteroids (Zimmerman method) and urine vanillylmandelic acid (VMA).


Drug: antacids, sucralfate, calcium, magnesium, didanosine, multivitamins (containing iron or zinc) may decrease absorption of nalidixic acid; may increase hypoprothrombinemic effects of warfarin.


Absorption: Readily from GI tract. Peak: Urine: 3–4 h. Distribution: Crosses placenta; distributed into breast milk. Metabolism: Partially in liver; some in kidneys. Elimination: In urine. Half-Life: 1.1–2.5 h.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Perform C&S tests prior to initiation of treatment and periodically thereafter. Obtain blood counts and kidney or liver function tests if therapy is continued longer than 2 wk.
  • Watch for CNS reactions, which tend to occur 30 min after initiation of treatment or after second or third dose. Infants, children, and older adults are especially susceptible. Report immediately the onset of marked irritability, vomiting, bulging of anterior fontanelle, headache, excitement or drowsiness, papilledema, vertigo.

Patient & Family Education

  • Use drug exactly as prescribed and do not change dosage. Omitted doses, especially in early days of therapy, may promote development of bacterial resistance. Take full amount of medication.
  • Contact physician immediately for unexplained behavior changes or severe headaches.
  • Maintain adequate hydration (2000–3000 mL/d if tolerated) during treatment period. Consult physician if you notice a change in your urination pattern.
  • Avoid exposure to direct sunlight or ultraviolet light while receiving drug. Contact physician if photosensitivity occurs. You may be photosensitive up to 3 mo after termination of drug.
  • Contact your physician if you notice visual disturbances during first few days of therapy. Symptoms usually disappear promptly with reduction of dosage or discontinuation of therapy.

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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