Nitrofurantoin
MACROBID
Pronunciation: nye-troe-fyoor-AN-toyn
“Mac bids (on) Night fur”
What it isUrinary antiseptic whose reactive intermediates damage bacterial DNA; uncomplicated lower urinary infection.
Why this oneIt concentrates in urine with little systemic or microbiome exposure, so resistance remains relatively uncommon.
What limits itDo not use for pyelonephritis or bacteremia; poor renal function prevents urinary delivery. Long courses risk lung, liver and nerve toxicity.
Pearls
- As effective as TMP/SMX for cystitis, with less E. coli resistance.
- Label bars CrCl ≤60; short courses probably safe down to 30.
- Avoid at term or in labor: neonatal hemolytic anemia.
- G6PD deficiency: hemolysis risk.
Nitrofurantoin prescription history
Animated chart of estimated U.S. prescriptions per year, Antibacterials (systemic) (1938–2026). Nitrofurantoin enters in 1953 (estimated).
FDA-approved for
- UTIs (~1953)
Principal riskPulmonary toxicity with long-term use; ineffective in pyelonephritis
Classes and tags
Clinical profile
Legacy pregnancy categoryB
Defining liabilityAllergy, gastrointestinal effects and agent-specific renal, hepatic, hematologic or interaction risks.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Urinary tract infection | Adults & peds >12 yr | 100 mg BID | 100 mg BID | 100 mg BID x7 days |
Renal Contraindicated if CrCl <60 mL/min or significant renal impairment (anuria/oliguria)
Hepatic Contraindicated with prior nitrofurantoin-associated cholestatic jaundice/hepatic dysfunction; otherwise Undefined
Instructions
- Take with food
Available strengths
- cap 50, 100 mg
Contraindications
- Anuria, oliguria, or significant renal impairment (CrCl <60 mL/min)
- Pregnancy at term (38-42 wk), labor/delivery, or imminent labor (neonatal hemolytic anemia risk)
- Neonates under 1 month of age
- Prior cholestatic jaundice/hepatic dysfunction associated with nitrofurantoin
Cautions
- Acute, subacute, or chronic pulmonary hypersensitivity reactions (may be irreversible)
- Peripheral neuropathy — may be severe/irreversible; higher risk with renal impairment, anemia, diabetes, B deficiency
- Hepatotoxicity (hepatitis, cholestatic jaundice, hepatic necrosis)
- Hemolytic anemia (G6PD deficiency)
- Pseudomembranous colitis
Adverse reactions
- Nausea
- Headache
- Flatulence
- Pulmonary hypersensitivity reactions
- Peripheral neuropathy
- Hepatic reactions
Pregnancy Contraindicated at term (38-42 wk), during labor/delivery, or when labor imminent (neonatal hemolytic anemia risk)
Lactation Undefined
Cost
Generic entry2011
Open Nitrofurantoin in the interactive console ↗
Memory aids: interaction avatars
Open Nitrofurantoin in the interactive console ↗
Self-check
- Can nitrofurantoin treat pyelonephritis or bacteremia?
No. - Why can poor renal function undermine nitrofurantoin treatment?
It prevents urinary delivery.