Nitrofurantoin

Bacterial flavoproteins reduce nitrofurantoin to reactive intermediates that inactivate or alter ribosomal proteins and other macromolecules, inhibiting protein, DNA, RNA, and cell wall synthesis

Adult

Uncomplicated UTI: 50-100mg QID or 100mg BID (macrocrystal) x 5-7 days. UTI prophylaxis: 50-100mg once daily at bedtime. Take with food to improve tolerance.

Pediatric

>1 month: 5-7mg/kg/day divided QID (max 400mg/day). Prophylaxis: 1-2mg/kg once daily.

Renal adjustment

FDA label: CONTRAINDICATED in anuria, oliguria, or significant renal impairment (CrCl <60 mL/min) — sub-therapeutic urinary levels + systemic accumulation/toxicity. (Note: AGS Beers 2019 / IDSA consider short courses acceptable at CrCl ≥30; the FDA label is the conservative bound.)

Hepatic adjustment

Contraindicated in active hepatic disease; use caution in hepatic impairment.

Geriatric

Use caution; increased risk of peripheral neuropathy and pulmonary toxicity in elderly; ensure adequate renal function.

Max dose

400mg/day (divided); 100mg/day (prophylaxis)

• Anuria, oliguria, or significant renal impairment (CrCl <60 mL/min) — FDA label contraindication
• Known hypersensitivity to nitrofurantoin
• Pregnancy at term (38-42 weeks gestation)
• Infants <1 month old (risk of hemolytic anemia)
• G6PD deficiency (risk of hemolytic anemia)
• History of cholestatic jaundice or hepatic dysfunction with nitrofurantoin