Norfloxacin

Norfloxacin is a fluoroquinolone that reaches useful levels only in urine and the gut, so it is limited to urinary tract infection, prostatitis and gut-directed uses. It has been withdrawn in several countries and is rarely preferred now.

Classification. Fluoroquinolone, second generation.

Mechanism. Inhibits DNA gyrase and topoisomerase IV; bactericidal.

Spectrum. Enterobacterales and some Pseudomonas aeruginosa in urine. Weak against Gram-positive bacteria. Not suitable for systemic or respiratory infection.

Pharmacokinetics. Oral bioavailability 30 to 40%. Half-life 3 to 4 hours. Low serum levels, high urinary and faecal levels. Excreted in urine and bile.

Maximum 800 mg daily.

Adults, oral. 400 mg every 12 hours, taken 1 hour before or 2 hours after food. - Uncomplicated cystitis: 400 mg every 12 hours for 3 days. - Complicated urinary tract infection and pyelonephritis (oral step-down only): 400 mg every 12 hours for 7 to 10 days. - Chronic prostatitis: 400 mg every 12 hours for 28 days. - Prevention of spontaneous bacterial peritonitis in cirrhosis with low ascitic protein: 400 mg once daily (only where other options are unavailable).

Children. Not advised.

Alternatives. Nitrofurantoin, trimethoprim, fosfomycin, ciprofloxacin, levofloxacin.

Boxed-warning level risks. The class risks: tendon rupture, neuropathy, central nervous system effects, myasthenia aggravation.

Contraindications. Fluoroquinolone hypersensitivity; previous tendon disorder with a fluoroquinolone; growing children and adolescents; epilepsy (relative); glucose 6-phosphate dehydrogenase deficiency (haemolysis reported).

Adverse effects. Nausea, abdominal pain, headache, dizziness. Serious: tendon rupture, QT prolongation, dysglycaemia, neuropathy, seizures, psychosis, hepatotoxicity, Clostridioides difficile infection, severe skin reactions.

Interactions. Cations (separate by 2 hours before or 2 hours after), warfarin, theophylline, ciclosporin, QT-prolonging drugs, corticosteroids, NSAIDs, and caffeine.

Common prescribing errors. Using it for systemic infection, giving it with food or dairy, and not shortening the interval in renal impairment.

Special groups. - Pregnancy: avoid. Breastfeeding: avoid. - Older adults: increased tendon and central nervous system risk. - Kidney impairment: creatinine clearance 30 mL/min or less 400 mg once daily. - Liver impairment: use with caution. - Region: availability in East Africa is limited and variable.

Preparation. Oral tablets with a full glass of water, empty stomach, separated from cations and dairy.

Baseline and monitoring. - Baseline: medication review, creatinine, pregnancy status, glucose in diabetes. - During treatment: tendon pain, paraesthesia, mood; culture-based review at 3 days for failure.

Stop rules. Stop for tendon pain, neuropathy, psychiatric disturbance, seizure or severe rash.

Referral and escalation. Refer for treatment failure, recurrent urinary infection, and complicated prostatitis.