Norfloxacin

- 4-quinolone antibacterial
- Fluorinated piperazinyl-substituted congener of nalidixic acid
- Greater antibacterial activity compared to nalidixic acid

 

 

Antibacterial Spectrum

- E.coli
- Klebsiella
- Enterobacter
- Proteus
- Citrobacter
- H.influenzae
- N.gonorrhoeae, N.meningitidis
- Salmonella
- Shigella
- Staphylococci

 

Pharmacokinetics

- 70% absorbed after oral administration
- Absorption slightly delayed with food
- 400 mg oral dose gives 1.35-1.58 mg/l serum concentrations in 1-2 hours
- Good concentrations in kidney, prostate, urine, bile, faeces, vagina, cervix, salpinges, ovaries
- 30% excreted unchanged in urine
- Metabolised in liver
- Elimination half life 3.5-6.5 hours

 

Uses

1. UTI
- High urinary concentration
- Coverage of commonly involved organisms
- Coverage of Ps.aeruginosa; useful in catheter associated / nosocomial infections
- No need to alkalinise the urine
- Does not disturb normal anaerobic bowel flora
- High cure rates

 

Advantages over other drugs in UTI

Nalidixic acid
- Effective against bacteria resistant to nalidixic acid
- Broader spectrum, including Pseudomonas aeruginosa
- Resistance relatively rare

Advantages over other drugs in UTI (contd.)

Aminoglycosides
- Oral route of administration hence more convenient- Different chemical group, hence effective against organisms resistant to aminoglycosides
- Avoids adverse effects of aminoglycosides, I.e., VIII cranial nerve toxicity and nephrotoxicity

 

 

Advantages over other drugs in UTI (contd.)

Penicillins (ampicillin, amoxycillin)
- Different chemical class, hence effective in cases resistant to penicillins
- Coverage of pseudomonas
- No plasmid mediated resistance
- May be used in patients allergic to penicillins

 

 

 

 

Uses (contd.)

2. Gonorrhoea
- Good activity against Neisseria gonorrhoea, including penicillinase producers
- Good concentrations in genitourinary tract
- Single dose (800mg) therapy for uncomplicated gonorrhoea

 

 

 

Uses (contd.)

3. Gastrointestinal Infections
- Good activity against Shigella, Salmonella, E.coli, Yersinia enterocolitica, Campylobacter jejuni, Aeromonas hydrophilia, Pleismonas shigelloides and Vibrio parahaemolyticus
- Poor activity against anaerobes, hence does not disturb normal anaerobic bowel flora
- Good concentrations in stools
- Useful in bacterial diarrhoea, traveller’s diarrhoea, gastroenteritis

Uses (contd.)

4. In Granulocytopenic patients
- Cytotoxic drugs (for cancer) may cause granulocytopenia
- In granulocytopenic patients, infections may occur arising from organisms from the patient’s own gut
- Norfloxacin may be used for bowel decontamination
- Norfloxacin covers aerobic pathogens but spares normal anaerobic bowel flora which helps in “colonisation resistance”

 

 

Dosage

Usual dosage
400 mg twice daily for 7-10 days

In renal impairment (creatinine clearance < 30 ml/min)
400 mg daily

Chronic relapsing UTI
400 mg twice daily for 10-21 days

Uncomplicated gonorrhoea
800 mg single dose

 

 

+Adverse Effects
- Well tolerated
- Commoner effects are GI or neurological (nausea, headache, dizziness)

Contraindications/Precautions
- Contraindicated in hypersensitivity
- Adequate fluid intake advised to avoid crystalluria
- Avoid in children and in pregnancy, as damage to articular cartilage has occurred in juvenile animals administered the drug
- Nitrofurantoin antagonises norfloxacin effect in urinary tract if administered concurrently

 

Comparison with Ciprofloxacin

- Norfloxacin is adequate for UTI, GI infections
- Ciprofloxacin is costlier Comparison with Nalidixic Acid
- Wider spectrum
- Less resistance
- Better penetration into tissues of urinary tract